Docs: compile times of JSON_HAS_STD_FORMAT=0 and JSON_HAS_RANGES=0

Add sections on switching off std::format and ranges support to the compile-times page, with measurements (Apple clang, GCC 16, -std=c++20), the functionality that is lost, and chart rows (issue #5294). Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Binary reader and writer: remove checks that invariants make dead (#6001 )
2026-11-05 12:19:21 +00:00 · 2026-11-05 09:18:04 +01:00 · 2026-11-04 23:42:17 +01:00 · 2026-11-04 23:38:57 +01:00 · 2026-11-04 23:38:47 +01:00 · 2026-11-04 17:46:20 +01:00
130 changed files with 4303 additions and 8139 deletions
@@ -111,8 +111,6 @@ context which existing file needs to be extended, and only very few cases requir
 When fixing a bug, edit `unit-regression3.cpp` and add a section referencing the fixed issue.
 `unit-regression2.cpp` holds the older tests; the two files exist because a single one grew large enough for the
 MinGW linker to fail relocating it, so please keep adding to the smaller file rather than growing the larger one.
-Tests that call `sax_parse` go into `unit-sax_parse.cpp` rather than into a large test file: every call instantiates
-the parser and the binary reader that recover from errors, which grows a test file considerably.

 #### Exceptions

@@ -28,7 +28,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -22,7 +22,7 @@ jobs:
    runs-on: ubuntu-26.04
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -46,7 +46,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -20,7 +20,7 @@ jobs:
    timeout-minutes: 30
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -13,7 +13,7 @@ jobs:
    runs-on: ubuntu-22.04
    steps:
    - name: Harden Runner
-      uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+      uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
      with:
        egress-policy: audit

@@ -27,7 +27,7 @@ jobs:

    steps:
    - name: Harden Runner
-      uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+      uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
      with:
        egress-policy: audit

@@ -20,7 +20,7 @@ jobs:
      pull-requests: write
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -21,7 +21,7 @@ jobs:
    runs-on: ubuntu-26.04
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -31,7 +31,7 @@ jobs:
      security-events: write
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -54,7 +54,7 @@ jobs:
    timeout-minutes: 60
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -23,7 +23,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -37,7 +37,7 @@ jobs:
    runs-on: ubuntu-26.04
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -40,7 +40,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -36,7 +36,7 @@ jobs:
    runs-on: ubuntu-26.04
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -16,7 +16,7 @@ jobs:

    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -25,7 +25,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -38,7 +38,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Check that Meson and pkg-config offer the CMake options
        run: make check_build_options
      - name: Install Meson
@@ -80,7 +80,7 @@ jobs:
    runs-on: ubuntu-26.04
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -92,7 +92,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -112,7 +112,7 @@ jobs:
        target: [ci_test_single_header, ci_cppcheck, ci_cpplint, ci_reproducible_tests, ci_non_git_tests, ci_offline_testdata, ci_reuse_compliance, ci_test_valgrind]
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -123,7 +123,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -142,7 +142,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -168,7 +168,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -178,7 +178,7 @@ jobs:
    runs-on: ubuntu-26.04
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -244,7 +244,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: CXX=g++-${{ matrix.compiler }} cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -262,7 +262,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -279,7 +279,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Disable filesystem support (std::filesystem is unusable) for clang 7 / 8 / 9 / 10
        run: echo "JSON_FORCED_GLOBAL_COMPILE_OPTIONS=-DJSON_HAS_FILESYSTEM=0;-DJSON_HAS_EXPERIMENTAL_FILESYSTEM=0" >> "$GITHUB_ENV"
        if: ${{ matrix.compiler == '7' || matrix.compiler == '8' || matrix.compiler == '9' || matrix.compiler == '10' }}
@@ -299,7 +299,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -319,7 +319,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build with libc++
@@ -346,7 +346,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -366,7 +366,7 @@ jobs:
      # import-std support. Its opt-in token is CMake-version-specific, so pin
      # CMake to the version whose token is set in tests/module_cpp20/CMakeLists.txt.
      - name: Get pinned CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
        with:
          cmakeVersion: 4.3.4
      # Clang: the std library module is provided by libc++ (the image's libstdc++
@@ -392,7 +392,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -409,7 +409,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -423,7 +423,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DJSON_CI=On
      - name: Build
@@ -433,7 +433,7 @@ jobs:
    runs-on: ubuntu-26.04
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -443,7 +443,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Run CMake
        run: cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=$EMSDK/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -GNinja
      - name: Build
@@ -456,7 +456,7 @@ jobs:
        target: [ci_test_examples, ci_test_build_documentation, ci_test_documentation_mermaid]
    steps:
      - name: Harden Runner
-        uses: step-security/harden-runner@dc2769abcc0fcfbadfc1df54081c1608579ef6b2 # v2.22.2
+        uses: step-security/harden-runner@46b06cea07f9e64621fdf066ba77ac6915163d43 # v2.22.3
        with:
          egress-policy: audit

@@ -484,7 +484,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Check that the job runs natively on arm64
        run: uname -m && test "$(uname -m)" = aarch64
      - name: Run CMake
@@ -90,7 +90,7 @@ jobs:
        with:
          persist-credentials: false
      - name: Get latest CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
      - name: Set extra CXX_FLAGS for latest std_version
        # /wd5285 silences C5285 emitted by the bundled third-party doctest.h, which
        # specializes std::tuple (newly diagnosed by the VS2026 v145 toolset)
@@ -216,7 +216,7 @@ jobs:
      # import-std support. Its opt-in token is CMake-version-specific, so pin
      # CMake to the version whose token is set in tests/module_cpp20/CMakeLists.txt.
      - name: Get pinned CMake and ninja
-        uses: lukka/get-cmake@a89e43e22a96abafcd7a62db652a65ecd33052c9 # v4.4.4
+        uses: lukka/get-cmake@f86dd60acae0d132056913e248bdabf0e0580b7a # v4.4.5
        with:
          cmakeVersion: 4.3.4
      # CMAKE_CXX_FLAGS replaces CMake's MSVC defaults (which include /EHsc), and
@@ -495,7 +495,7 @@ bool key(string_t& val);
 bool parse_error(std::size_t position, const std::string& last_token, const detail::exception& ex);
 ```

-The return value of each function determines whether parsing should proceed. For `parse_error`, returning `true` [recovers from the error](https://json.nlohmann.me/features/parsing/error_recovery/): the parser repairs the input and continues.
+The return value of each function determines whether parsing should proceed.

 To implement your own SAX handler, proceed as follows:

@@ -503,7 +503,7 @@ To implement your own SAX handler, proceed as follows:
 2. Create an object of your SAX interface class, e.g. `my_sax`.
 3. Call `bool json::sax_parse(input, &my_sax)`; where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface.

-Note the `sax_parse` function only returns a `bool` indicating whether the input was parsed without errors and no SAX event returned `false`. It does not return a  `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error -- it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file [`json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp).
+Note the `sax_parse` function only returns a `bool` indicating the result of the last executed SAX event. It does not return a  `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error -- it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file [`json_sax.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/input/json_sax.hpp).

 ### STL-like access

@@ -348,20 +348,20 @@ add_custom_target(ci_test_no_thread_local

 add_custom_target(ci_test_coverage
    COMMAND CXX=g++ ${CMAKE_COMMAND}
-        -DCMAKE_BUILD_TYPE=Debug -GNinja -DCMAKE_CXX_FLAGS="--coverage;-fprofile-arcs;-ftest-coverage"
+        -DCMAKE_BUILD_TYPE=Debug -GNinja -DCMAKE_CXX_FLAGS="--coverage;-fprofile-arcs;-ftest-coverage;-fvar-tracking-assignments"
        -DJSON_BuildTests=ON
        -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_coverage
    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_coverage
    COMMAND cd ${PROJECT_BINARY_DIR}/build_coverage && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure

    COMMAND CXX=g++ ${CMAKE_COMMAND}
-        -DCMAKE_BUILD_TYPE=Debug -GNinja -DCMAKE_CXX_FLAGS="-m32;--coverage;-fprofile-arcs;-ftest-coverage"
+        -DCMAKE_BUILD_TYPE=Debug -GNinja -DCMAKE_CXX_FLAGS="-m32;--coverage;-fprofile-arcs;-ftest-coverage;-fvar-tracking-assignments"
        -DJSON_BuildTests=ON -DJSON_32bitTest=ONLY
        -S${PROJECT_SOURCE_DIR} -B${PROJECT_BINARY_DIR}/build_coverage32
    COMMAND ${CMAKE_COMMAND} --build ${PROJECT_BINARY_DIR}/build_coverage32
    COMMAND cd ${PROJECT_BINARY_DIR}/build_coverage32 && ${CMAKE_CTEST_COMMAND} --parallel ${N} --output-on-failure

-    COMMAND ${LCOV_TOOL} --directory . --capture --output-file json.info --rc branch_coverage=1 --rc geninfo_unexecuted_blocks=1 --ignore-errors mismatch --ignore-errors unused --ignore-errors inconsistent
+    COMMAND ${LCOV_TOOL} --directory . --capture --output-file json.info --rc branch_coverage=1 --ignore-errors mismatch --ignore-errors unused --ignore-errors inconsistent
    COMMAND ${LCOV_TOOL} -e json.info ${SRC_FILES} --output-file json.info.filtered --rc branch_coverage=1 --ignore-errors unused --ignore-errors inconsistent
    COMMAND ${CMAKE_SOURCE_DIR}/tests/thirdparty/imapdl/filterbr.py json.info.filtered > json.info.filtered.noexcept
    COMMAND ${GENHTML_TOOL} --title "JSON for Modern C++" --legend --demangle-cpp --output-directory html --show-details --branch-coverage --ignore-errors inconsistent json.info.filtered.noexcept
@@ -178,8 +178,10 @@ function(_json_test_add_test test_name file main cxx_standard)
            COMMAND ${memcheck_command} $<TARGET_FILE:${test_target}> ${DOCTEST_TEST_FILTER}
            WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
        )
+        # under Valgrind the slowest tests take close to 25 minutes, so ctest's
+        # default timeout of 1500 seconds leaves no headroom
        set_tests_properties(${test_target}_valgrind PROPERTIES
-            LABELS "valgrind" FIXTURES_REQUIRED TEST_DATA
+            LABELS "valgrind" FIXTURES_REQUIRED TEST_DATA TIMEOUT 3600
        )
    endif()
 endfunction()
@@ -120,6 +120,16 @@ overload (3).
    See [Number conversion](../../features/types/number_handling.md#number-conversion)
    for more information.

+!!! note "Booleans as numbers"
+
+    A JSON boolean converts to `#!cpp 0` or `#!cpp 1` for every arithmetic type **except** [`number_integer_t`](number_integer_t.md),
+    [`number_unsigned_t`](number_unsigned_t.md) and [`number_float_t`](number_float_t.md) (by default `#!cpp std::int64_t`,
+    `#!cpp std::uint64_t`, and `#!cpp double`), for which `#!cpp get<T>()` throws
+    [`type_error.302`](../../home/exceptions.md#jsonexceptiontype_error302) ("type must be number, but is boolean"). So
+    `#!cpp json(true).get<int>()` is `#!cpp 1`, while `#!cpp json(true).get<std::int64_t>()` and
+    `#!cpp json(true).get<double>()` throw. This is the behavior of all 3.x versions;
+    [`basic_json_view::get<T>()`](../basic_json_view/get.md) behaves the same.
+
 !!! note "`std::optional` conversions"

    Prior to version 3.13.0, `#!cpp get<std::optional<T>>()` (and other conversions to `std::optional<T>`) failed to
@@ -65,7 +65,12 @@ the same index, which is now a different value.

 ## Exception safety

-Strong exception safety: if an exception occurs, the original value stays intact.
+Overload (1) gives the strong guarantee: if an exception is thrown, there are no changes in the JSON value.
+
+Overloads (2) to (5) give the basic guarantee: if an exception is thrown while the elements or members are copied
+(for example, `std::bad_alloc`), the JSON value may be partially modified, but it stays a valid array or object.
+
+The exceptions listed below are thrown before the JSON value is changed.

 ## Exceptions

@@ -15,7 +15,9 @@ the patch. This function applies a JSON patch in place and returns void.

 ## Exception safety

-No guarantees, value may be corrupted by an unsuccessful patch operation.
+No guarantees: if an operation fails, the operations before it stay applied, and a failing `move` operation may already
+have removed the value at its "from" location. Use [`patch`](patch.md) if the value must be unchanged after a failed
+patch.

 ## Exceptions

@@ -62,8 +64,19 @@ the JSON value, the complexity can usually be neglected.
 ## Notes

 Unlike [`patch`](patch.md), `patch_inplace` applies the operation "in place" and no copy of the JSON value is created.
-That makes it faster for large documents by avoiding the copy. However, the JSON value might be corrupted if the
-function throws an exception.
+That makes it faster for large documents by avoiding the copy.
+
+!!! warning "Not atomic"
+
+    `patch_inplace` applies the operations one after the other and does not undo them when one fails. After an
+    exception, the value holds the result of the operations before the failing one, and a failing `move` operation
+    (a "remove" followed by an "add") may already have removed the value at its "from" location; see the second example
+    below. [RFC 6902](https://tools.ietf.org/html/rfc6902#section-5) requires that a patch with a failing operation is
+    not deemed successful, but leaves open what happens to the document.
+
+    If the value must stay unchanged when the patch fails, use [`patch`](patch.md), which applies the patch to a copy:
+    `#!cpp j = j.patch(json_patch);`. Validating the patch beforehand is not enough, as "test" operations and missing
+    paths are only detected while the patch is applied.

 Duplicate member names inside an operation object are resolved by the parser before the patch is applied (the last one
 is kept, see [`object_t`](object_t.md#behavior)), so `#!json {"op": "add", "op": "remove", "path": "/a"}` is a
@@ -104,9 +104,7 @@ The SAX event lister must follow the interface of [`json_sax`](../json_sax/index

 ## Return value

-`#!cpp true` if the input was parsed without errors and no SAX event returned `#!cpp false`; `#!cpp false` otherwise.
-In particular, the result is `#!cpp false` for input with errors, even if the SAX parser recovered from all of them
-(see [error recovery](../../features/parsing/error_recovery.md)).
+return value of the last processed SAX event

 ## Exception safety

@@ -165,7 +163,6 @@ use the same file with stdio functions, but it must not wait for another thread
 - Added `ignore_trailing_commas` in version 3.13.0.
 - Added `tag_handler` in version 3.13.0.
 - Extended container support (1) to include types with lvalue-only ADL `begin`/`end` (matching `std::begin`/`std::end` semantics) in version 3.13.0.
- Recovering from parse errors (see [`parse_error`](../json_sax/parse_error.md)) added in version 3.13.0.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
 - `JSON_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave a `#!cpp std::istream` positioned right
  after the parsed value when `strict` is `#!cpp false`.
@@ -11,7 +11,8 @@ For the types below, the conversion works directly on the flat index — no `Bas

 - `#!cpp bool`
 - arithmetic types other than `#!cpp bool` (for a boolean, `#!cpp 0`/`#!cpp 1`, exactly as for
-  [`BasicJsonType::get<T>()`](../basic_json/get.md))
+  [`BasicJsonType::get<T>()`](../basic_json/get.md#notes), except for `number_integer_t`, `number_unsigned_t` and
+  `number_float_t`, which throw `type_error.302` for a boolean, as `BasicJsonType::get<T>()` does)
 - `#!cpp std::nullptr_t`
 - `#!cpp std::basic_string<char, Traits, Alloc>` (including `string_t`) — a copy of the string
 - [`string_view_t`](index.md#member-types) — **no copy**: the returned view points into the document's
@@ -7,8 +7,7 @@ struct json_sax;

 This class describes the SAX interface used by [sax_parse](../basic_json/sax_parse.md). Each function is called in
 different situations while the input is parsed. The boolean return value informs the parser whether to continue
-processing the input; for [`parse_error`](parse_error.md), it decides whether to
-[recover from the error](../../features/parsing/error_recovery.md).
+processing the input.

 For instance, parsing the JSON text `{"a": [1, true]}` triggers the following callbacks, in order:

@@ -21,18 +21,11 @@ A parse error occurred.

 ## Return value

-Whether to recover from the error:
-
- `#!cpp false` stops parsing.
- `#!cpp true` recovers from the error: the error is repaired and parsing continues. If that is not possible, which
-  happens in the binary formats when the end of the item with the error is unknown, the value read so far is completed
-  and parsing stops. See [error recovery](../../features/parsing/error_recovery.md) for how errors are repaired.
-
-Either way, [`sax_parse`](../basic_json/sax_parse.md) returns `#!cpp false`.
+Whether parsing should proceed (**must return `#!cpp false`**).

 ## Examples

-??? example "Example: (1) the SAX interface"
+??? example

    The example below shows how the SAX interface is used.

@@ -46,30 +39,13 @@ Either way, [`sax_parse`](../basic_json/sax_parse.md) returns `#!cpp false`.
    --8<-- "examples/sax_parse.output"
    ```

-??? example "Example: (2) recovering from errors"
-
-    The example below shows how a SAX parser recovers from errors.
-
-    ```cpp
-    --8<-- "examples/sax_parse__error_recovery.cpp"
-    ```
-    
-    Output:
-    
-    ```
-    --8<-- "examples/sax_parse__error_recovery.output"
-    ```
-
 ## See also

 - [`sax_parse`](../basic_json/sax_parse.md) - SAX parser
 - [Parsing and Exceptions](../../features/parsing/parse_exceptions.md) - the article on handling parse errors without
  exceptions
- [Error Recovery](../../features/parsing/error_recovery.md) - the article on recovering from parse errors
 - [SAX Interface](../../features/parsing/sax_interface.md) - guide to event-based parsing

 ## Version history

 - Added in version 3.2.0.
- Returning `#!cpp true` recovers from the error since version 3.13.0; before, parsing stopped, but the result of
-  [`sax_parse`](../basic_json/sax_parse.md) could be wrong.
@@ -35,6 +35,9 @@ Note that enabling this macro increases the size of every JSON value by two `std
 overhead to parsing, copying JSON value objects, and the generation of error messages for exceptions. It also causes
 these values to be reported in those error messages.

+If [`JSON_DIAGNOSTICS`](json_diagnostics.md) is also set, the message contains the path and the byte range, such as
+`(/1) (bytes 4-8)`. An exception about the root value has no path and only the range, such as `(bytes 0-4)`.
+
 ## Default definition

 The default value is `0` (position diagnostics are switched off).
@@ -1,43 +0,0 @@
-#include <iostream>
-#include <iomanip>
-#include <nlohmann/json.hpp>
-
-using json = nlohmann::json;
-
-// a SAX parser that creates a JSON value like json::parse does, but that
-// recovers from parse errors instead of stopping at the first one
-class recovering_parser : public nlohmann::detail::json_sax_dom_parser<json>
-{
-  public:
-    explicit recovering_parser(json& result)
-        : nlohmann::detail::json_sax_dom_parser<json>(result, false)
-    {}
-
-    bool parse_error(std::size_t position,
-                     const std::string& /*last_token*/,
-                     const json::exception& ex)
-    {
-        std::cout << "byte " << position << ": " << ex.what() << '\n';
-
-        // repair the input and continue
-        return true;
-    }
-};
-
-int main()
-{
-    // JSON text with several mistakes that ends too early
-    const std::string text = R"({
-    "name": "Hello World",
-    "tags": ["a" "b",],
-    "valid": tru,
-    "size": 1.,
-    "nested": {"x": 1)";
-
-    json result;
-    recovering_parser sax(result);
-    const bool valid = json::sax_parse(text, &sax);
-
-    std::cout << "\nvalid JSON: " << std::boolalpha << valid << '\n'
-              << std::setw(4) << result << std::endl;
-}
@@ -1,19 +0,0 @@
-byte 49: [json.exception.parse_error.101] parse error at line 3, column 20: syntax error while parsing array - unexpected string literal; expected ']'
-byte 51: [json.exception.parse_error.101] parse error at line 3, column 22: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
-byte 70: [json.exception.parse_error.101] parse error at line 4, column 17: syntax error while parsing value - invalid literal; last read: '"valid": tru,'
-byte 86: [json.exception.parse_error.101] parse error at line 5, column 15: syntax error while parsing value - invalid number; expected digit after '.'; last read: '1.,'
-byte 109: [json.exception.parse_error.101] parse error at line 6, column 22: syntax error while parsing object - unexpected end of input; expected '}'
-
-valid JSON: false
-{
-    "name": "Hello World",
-    "nested": {
-        "x": 1
-    },
-    "size": 1,
-    "tags": [
-        "a",
-        "b"
-    ],
-    "valid": null
-}
@@ -0,0 +1,130 @@
+# Reading and writing files
+
+The library has no functions that take a file name. It reads from and writes to streams, so files are handled with
+`#!cpp std::ifstream` and `#!cpp std::ofstream` (or a `#!cpp FILE*` when reading). This page collects the recipes for
+the common cases and the mistakes that show up again and again.
+
+## Reading a JSON file
+
+Pass the stream to [`parse`](../api/basic_json/parse.md) directly, and check that the file was opened:
+
+```cpp
+#include <fstream>
+#include <stdexcept>
+#include <string>
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+json read_json_file(const std::string& path)
+{
+    std::ifstream f(path);
+    if (!f.is_open())
+    {
+        throw std::runtime_error("cannot open " + path);
+    }
+    return json::parse(f);
+}
+```
+
+- **Check that the file is open.** A stream that failed to open looks like an empty input, so `parse` reports
+  [`parse_error.101`](../home/exceptions.md#jsonexceptionparse_error101) ("unexpected end of input") at line 1,
+  column 1 instead of saying that the file is missing. A relative path is resolved against the working directory of the
+  running program, which is often not the directory of the source file (see the
+  [FAQ](../home/faq.md#parsing-a-file-fails-with-unexpected-end-of-input)).
+- **Don't read the file into a string first.** Parsing from a `#!cpp std::ifstream` is only about 10 to 20 % slower
+  than reading the whole file into a string with one `read()` and parsing that, and it needs no memory for the copy (see
+  [input sources and performance](parsing/index.md#input-sources-and-performance)). The common way to read a file with
+  `#!cpp std::istreambuf_iterator<char>` is so slow that it takes about twice as long as parsing from the stream. Read
+  the file into a string only if you need the text itself, for example for an error message. This advice is for
+  `#!cpp json::parse`. [`json_document`](json_view.md) reads a stream into a buffer that it owns anyway, so there is no
+  copy to save: reading the file into a `#!cpp std::string` yourself and passing that as an lvalue, which the document
+  borrows, was about 6 to 12 % faster than parsing from the stream, with the same single buffer.
+- `parse` requires the file to hold exactly one JSON value. Files with one value per line are read with
+  [JSON Lines](parsing/json_lines.md); files too large for memory are covered in
+  [Large, streamed, and partial input](parsing/large_and_partial_input.md).
+
+## Writing a JSON file
+
+[`dump`](../api/basic_json/dump.md) the value into a string first, then write the string:
+
+```cpp
+void write_json_file(const std::string& path, const json& j)
+{
+    const std::string text = j.dump(4) + '\n';  // may throw: nothing is written yet
+
+    std::ofstream f(path, std::ios::binary);
+    if (!f.is_open())
+    {
+        throw std::runtime_error("cannot open " + path);
+    }
+    f << text;
+    f.close();
+    if (f.fail())
+    {
+        throw std::runtime_error("cannot write " + path);
+    }
+}
+```
+
+- **Serialize before opening the file.** Opening a `#!cpp std::ofstream` truncates the file. `dump` and
+  [`operator<<`](../api/operator_ltlt.md) throw [`type_error.316`](../home/exceptions.md#jsonexceptiontype_error316)
+  when a string is not valid UTF-8 (see [handling invalid UTF-8](serialization.md#handling-invalid-utf-8)), and
+  `#!cpp f << std::setw(4) << j` may already have written part of the value when it throws. Serializing into a string
+  first leaves the old file untouched in that case.
+- **Check the stream after closing it.** A full disk or a missing permission sets the stream's error state; it does not
+  throw unless you enabled exceptions on the stream with `exceptions()`.
+- `std::ios::binary` writes the text as it is. Without it, Windows writes `\r\n` for every newline of a pretty-printed
+  value.
+
+## Replacing a file without corrupting it
+
+The library never writes a file itself, so this section is not about the library. It is general C++ advice for a
+problem users of the library keep running into.
+
+A program that crashes or is killed while it writes leaves a truncated file behind. To make sure readers see either the
+old or the new contents, write to a temporary file in the same directory and rename it over the original
+(C++17, `#!cpp <filesystem>`):
+
+```cpp
+#include <filesystem>
+
+void replace_json_file(const std::filesystem::path& path, const json& j)
+{
+    std::filesystem::path tmp = path;
+    tmp += ".tmp";  // use a unique name if several processes may write the file
+
+    write_json_file(tmp.string(), j);
+    std::filesystem::rename(tmp, path);  // replaces path
+}
+```
+
+The temporary file must be in the same directory (more precisely, on the same file system) as the target: a rename
+across file systems does not fall back to a copy, it fails and throws `#!cpp std::filesystem::filesystem_error`. On
+POSIX systems, the rename atomically replaces the file. Standard C++ has no way to flush a file to the disk (`fsync`),
+so this protects against a crashed program, but not necessarily against a power loss.
+
+## Binary formats
+
+The [binary formats](binary_formats/index.md) work the same way, with the streams opened in binary mode:
+
+```cpp
+// read
+std::ifstream in("data.cbor", std::ios::binary);
+json j = json::from_cbor(in);
+
+// write
+const std::vector<std::uint8_t> bytes = json::to_cbor(j);
+std::ofstream out("data.cbor", std::ios::binary);
+out.write(reinterpret_cast<const char*>(bytes.data()), static_cast<std::streamsize>(bytes.size()));
+```
+
+Without `std::ios::binary`, Windows turns the bytes `0x0D 0x0A` into `0x0A` and may stop at a byte `0x1A` while reading,
+and turns `0x0A` into `0x0D 0x0A` while writing, which corrupts the data.
+
+## See also
+
+- [Parsing](parsing/index.md) - the inputs `parse` accepts
+- [Serialization](serialization.md) - the options of `dump`
+- [`parse`](../api/basic_json/parse.md), [`dump`](../api/basic_json/dump.md)
+- [`operator>>`](../api/operator_gtgt.md), [`operator<<`](../api/operator_ltlt.md)
@@ -46,6 +46,8 @@ C++ types, and finally serialize it again.
  [BJData](binary_formats/bjdata.md), [BON8](binary_formats/bon8.md), [BSON](binary_formats/bson.md),
  [CBOR](binary_formats/cbor.md), [MessagePack](binary_formats/messagepack.md), or [UBJSON](binary_formats/ubjson.md).
 - [Binary values](binary_values.md) — store and exchange raw byte sequences.
+- [Reading and writing files](files.md) — read and write files safely, including replacing a file without
+  corrupting it.

 ## How values are stored and configured

@@ -29,7 +29,8 @@ other three continue on its result.

    [`patch`](../api/basic_json/patch.md) leaves the original value unchanged and returns the patched result as a copy.
    If the document is large and the original value is no longer needed,
-    [`patch_inplace`](../api/basic_json/patch_inplace.md) applies the same operations in place instead.
+    [`patch_inplace`](../api/basic_json/patch_inplace.md) applies the same operations in place instead. Unlike
+    `patch`, it is not atomic: if an operation fails, the operations before it stay applied.

 !!! note "Duplicate member names"

@@ -160,7 +160,9 @@ document: `#!cpp auto v = json_document::parse(text).root();` does not compile.
  wide. The limit is 16 bytes below 2^32, because the parser reads in 16-byte steps, and a position one step past the
  end must still fit.
 - **A stream is always read to its end.** There is no partial/streaming read of an `#!cpp std::istream`: the stream
-  is read to its end into a buffer the document owns, and parsing starts after that.
+  is read to its end into a buffer the document owns, and parsing starts after that. For a file, reading it into a
+  `#!cpp std::string` yourself and parsing that (an lvalue is borrowed) is therefore not more expensive in memory, and
+  was about 6 to 12 % faster than parsing from an `#!cpp std::ifstream`.
 - **Fewer source positions after edits.** With
  [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md) enabled,
  [`materialize()`](../api/basic_json_view/materialize.md) sets the same positions as `#!cpp basic_json::parse()`.
@@ -1,122 +0,0 @@
-# Error Recovery
-
-By default, parsing stops at the first error. With the [SAX interface](sax_interface.md), you can instead ask the
-parser to *recover*: to repair the error and continue, so that you get as much as possible out of malformed input, for
-instance a file that was cut off, JSON edited by hand, or the output of a language model.
-
-## Recovering from errors
-
-The SAX parser's [`parse_error`](../../api/json_sax/parse_error.md) function is called for every error. Its return value
-decides what happens next:
-
- `#!cpp false` stops parsing. This is what the SAX parsers of the library do, so [`parse`](../../api/basic_json/parse.md)
-  and [`accept`](../../api/basic_json/accept.md) never recover.
- `#!cpp true` repairs the error and continues parsing.
-
-When recovering, the SAX parser still receives well-formed events: every `start_object` or `start_array` is followed by
-the matching `end_object` or `end_array`, and every `key` is followed by exactly one value. A SAX parser that creates a
-JSON value, such as the one in the example below, therefore gets a complete value. Parsing always ends, and
-[`sax_parse`](../../api/basic_json/sax_parse.md) returns `#!cpp false` for input that is not valid JSON, even if every
-error was repaired. Each token is reported at most once, and the SAX parser can stop at any error by returning
-`#!cpp false`.
-
-!!! example
-
-    The example below derives a SAX parser from the library's parser for `json` values (`json_sax_dom_parser`),
-    and recovers from all errors.
-
-    ```cpp
-    --8<-- "examples/sax_parse__error_recovery.cpp"
-    ```
-    
-    Output:
-    
-    ```
-    --8<-- "examples/sax_parse__error_recovery.output"
-    ```
-
-## How errors are repaired
-
-Each error is repaired with the smallest local edit: a missing separator is inserted, a stray token is removed, what can
-be read of a broken string or number is kept, and a value that cannot be read at all becomes `#!json null`.
-
-| Mistake                   | Repair                                                                         | Example                                  | Result                     |
-|---------------------------|--------------------------------------------------------------------------------|------------------------------------------|----------------------------|
-| missing `,` or `:`        | inserted                                                                       | `#!json [1 2]`, `#!json {"a" 1}`         | `[1,2]`, `{"a":1}`         |
-| missing value             | `#!json null` for an object key or between commas in an array                  | `#!json {"a":}`, `#!json [1,,2]`         | `{"a":null}`, `[1,null,2]` |
-| trailing comma            | removed                                                                        | `#!json [1,2,]`                          | `[1,2]`                    |
-| broken string             | invalid escapes and bytes are replaced (see below); a line break ends the string | `#!json ["a\qb"]`                        | `["aqb"]`                  |
-| broken number             | the longest valid beginning is kept                                            | `#!json [1., 2e+]`                       | `[1,2]`                    |
-| unreadable value          | `#!json null`                                                                  | `#!json [1, NaN, tru]`                   | `[1,null,null]`            |
-| number too large          | passed as infinity, together with its text                                     | `#!json [1e999]`                         | infinity (see below)       |
-| stray `:`                 | removed                                                                        | `#!json ["a":1]`                         | `["a",1]`                  |
-| member without a key      | skipped up to the next `,` or `}`                                              | `#!json {1:2, "b":3}`                    | `{"b":3}`                  |
-| wrong closing bracket     | closes the innermost array or object                                           | `#!json {"a":[1,2}, "b":3}`              | `{"a":[1,2],"b":3}`        |
-| input ends too early      | all open arrays and objects are closed                                         | `#!json {"a":[1,2`                       | `{"a":[1,2]}`              |
-| text before the value     | skipped                                                                        | `#!json )]}'{"a":1}`                     | `{"a":1}`                  |
-
-In a string, an unknown escape like `\q` stands for the escaped character (`q`), as in JavaScript. An invalid `\u`
-escape, a lone surrogate, and ill-formed UTF-8 are each replaced by U+FFFD (REPLACEMENT CHARACTER), and control
-characters are kept. A string without its closing quote ends at the next line break or at the end of the input.
-
-The input after the top-level value is not repaired: as without recovery, it is reported as an error, and parsing stops.
-
-## Binary formats
-
-The binary formats ([BJData](../binary_formats/bjdata.md), [BON8](../binary_formats/bon8.md),
-[BSON](../binary_formats/bson.md), [CBOR](../binary_formats/cbor.md), [MessagePack](../binary_formats/messagepack.md),
-and [UBJSON](../binary_formats/ubjson.md)) have no delimiters to find the next value by. So what can be repaired depends
-on whether the end of the item with the error is known, a distinction that
-[RFC 8949, Section 5.3](https://www.rfc-editor.org/rfc/rfc8949.html#section-5.3) makes for CBOR, too.
-
-If the item is complete, but cannot be passed on as it is, it is replaced, and parsing continues after it:
-
-| Mistake                                                             | Formats                 | Repair                                                                  |
-|---------------------------------------------------------------------|-------------------------|-------------------------------------------------------------------------|
-| tag, if `tag_handler` is `cbor_tag_handler_t::error` (the default)  | CBOR                    | ignored                                                                 |
-| simple value other than `false`, `true`, and `null`, like undefined | CBOR                    | `#!json null`                                                           |
-| number too large for a custom `number_float_t`, like `float`        | all                     | infinity                                                                |
-| character (`C`) that is not ASCII                                   | BJData, UBJSON          | U+FFFD                                                                  |
-| invalid high-precision number (`H`)                                 | BJData, UBJSON          | the longest valid beginning is kept, as for JSON text, or `#!json null` |
-| high-precision number too large                                     | BJData, UBJSON          | passed as infinity, together with its text                              |
-| object key that is not a string                                     | BON8, CBOR, MessagePack | the member is skipped                                                   |
-| element of a type the library does not read, like ObjectId or date  | BSON                    | `#!json null`                                                           |
-| string without its terminator                                       | BSON                    | kept                                                                    |
-| document whose size does not match its content                      | BSON                    | kept                                                                    |
-
-CBOR tags and simple values are repaired as [RFC 8949, Section 6.1](https://www.rfc-editor.org/rfc/rfc8949.html#section-6.1)
-suggests for converting CBOR to JSON. By default, [`sax_parse`](../../api/basic_json/sax_parse.md) reports every tag as
-an error; when recovering, tags are then ignored like with
-[`cbor_tag_handler_t::ignore`](../../api/basic_json/cbor_tag_handler_t.md). Strings that are not valid UTF-8 are no
-error: like [`from_cbor`](../../api/basic_json/from_cbor.md) and the other functions by default, `sax_parse` passes
-them on as they are.
-
-After any other error, the end of the item is unknown: the input ended, a byte is not a valid type marker, or a size
-cannot be right. Parsing then stops, and the value read so far is completed: a key that waits for its value gets
-`#!json null`, and all open arrays and objects are closed. This keeps everything before the error of an input that was
-cut off. The exception is BSON, which stores the size of every document: an element whose end is unknown gets
-`#!json null`, the rest of its document is skipped, and parsing continues after the document.
-
-## Limitations
-
- A repair is a guess. For example, `#!json {"a" "b": 1}` could be meant as `#!json {"a": "b"}` or as
-  `#!json {"a": null, "b": 1}`; it is repaired to the former. Treat recovered values as a best effort, and check the
-  reported errors.
- A closing bracket always closes the innermost array or object. If a bracket is missing rather than wrong, the
-  repair differs from the intention: `#!json {"a": {"b": [1, 2}, "c": 3}` is repaired to
-  `#!json {"a": {"b": [1, 2], "c": 3}}`, although `#!json {"a": {"b": [1, 2]}, "c": 3}` may have been meant.
- Keys without quotes, and strings in single quotes, are not supported; such members are skipped.
- In the binary formats, a member that is skipped because its key is not a string is lost, and so are the elements of a
-  BSON document after one whose end is unknown.
- A number that is too large for `number_float_t` is passed as positive or negative infinity. The SAX parser's
-  `number_float` also gets the number's text, but a JSON value cannot store it, and
-  [`dump`](../../api/basic_json/dump.md) serializes infinity as `#!json null`.
- When parsing is not strict (see [`sax_parse`](../../api/basic_json/sax_parse.md)), a repair may read parts of the
-  input after the value, for instance of the next value in a stream of concatenated values.
-
-## See also
-
- [SAX interface](sax_interface.md) - implement a custom SAX handler
- [`parse_error`](../../api/json_sax/parse_error.md) - the SAX event for parse errors
- [`sax_parse`](../../api/basic_json/sax_parse.md) - generate SAX events
- [parsing and exceptions](parse_exceptions.md) - control error handling
@@ -35,6 +35,8 @@ std::ifstream f("example.json");
 json data = json::parse(f);
 ```

+See [Reading and writing files](../files.md) for checking that the file was opened and for writing files safely.
+
 The input must be encoded in UTF-8; other encodings are not supported. The exception is wide-character input, which
 is read as UTF-16 or UTF-32 — depending on the character type — and converted to UTF-8; see the
 [`parse`](../../api/basic_json/parse.md) page for an example. A single input may contain only one JSON value.
@@ -84,6 +86,9 @@ ahead: after parsing, it is positioned exactly as if every character had been re
 [`operator>>`](../../api/operator_gtgt.md) can still read several values from one stream (see also
 [JSON Lines](json_lines.md)).

+This does not hold for [`json_document`](../json_view.md): it reads a stream into a buffer it owns, so the stream saves
+no memory, and reading the file into a `#!cpp std::string` yourself and borrowing it is about 6 to 12 % faster.
+
 Two macros switch these optimizations off without changing any result:
 [`JSON_DISABLE_STREAM_BULK_SCAN`](../../api/macros/json_disable_stream_bulk_scan.md) for stream buffers that do not
 follow the usual `std::streambuf` contract, and
@@ -141,7 +146,7 @@ See [Zero-copy JSON views](../json_view.md) for the concept and the trade-offs.
 When the input is not valid JSON, the `parse` function throws an exception by default. If exceptions are undesired or
 unavailable, the parser can instead return a discarded value, or [`accept`](../../api/basic_json/accept.md) can be used
 to only check whether an input is valid JSON. See [parsing and exceptions](parse_exceptions.md) for the available
-options. To get as much as possible out of malformed input, a SAX parser can [recover from errors](error_recovery.md).
+options.

 ## See also

@@ -155,7 +160,6 @@ options. To get as much as possible out of malformed input, a SAX parser can [re
 - [SAX interface](sax_interface.md) - implement a custom SAX handler
 - [Zero-copy JSON views](../json_view.md) - parse into a read-only document and read it through views
 - [parsing and exceptions](parse_exceptions.md) - control error handling
- [error recovery](error_recovery.md) - get as much as possible out of malformed input
 - [parsing untrusted input](untrusted_input.md) - what to consider when parsing input from untrusted sources
 - [`operator>>`](../../api/operator_gtgt.md) - deserialize from stream
 - [`json_sax`](../../api/json_sax/index.md) - documentation of the SAX interface
@@ -68,8 +68,7 @@ bool parse_error(std::size_t position,
                 const json::exception& ex);
 ```

-The return value decides whether to stop parsing (`#!cpp false`) or to repair the error and continue
-(`#!cpp true`); see [error recovery](error_recovery.md) for the latter.
+The return value indicates whether the parsing should continue, so the function should usually return `#!cpp false`.

 ??? example "Example: report parse errors without exceptions"

@@ -62,8 +62,7 @@ bool key(string_t& val);
 bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex);
 ```

-The return value of each function determines whether parsing should proceed. For `parse_error`, returning
-`#!cpp true` [recovers from the error](error_recovery.md).
+The return value of each function determines whether parsing should proceed.

 Object keys are passed to `key` decoded and validated: escape sequences are already resolved, so different spellings of
 the same name yield the same string. See [`key`](../../api/json_sax/key.md#notes) for the exact guarantees.
@@ -102,7 +101,7 @@ To implement your own SAX handler, proceed as follows:
 2. Create an object of your SAX interface class, e.g. `my_sax`.
 3. Call `#!cpp bool json::sax_parse(input, &my_sax);` where the first parameter can be any input like a string or an input stream and the second parameter is a pointer to your SAX interface.

-Note the `sax_parse` function only returns a `#!cpp bool` indicating whether the input was parsed without errors and no SAX event returned `#!cpp false`. It does not return `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error - it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file `json_sax.hpp`.
+Note the `sax_parse` function only returns a `#!cpp bool` indicating the result of the last executed SAX event. It does not return `json` value - it is up to you to decide what to do with the SAX events. Furthermore, no exceptions are thrown in case of a parse error - it is up to you what to do with the exception object passed to your `parse_error` implementation. Internally, the SAX interface is used for the DOM parser (class `json_sax_dom_parser`) as well as the acceptor (`json_sax_acceptor`), see file `json_sax.hpp`.

 ## See also

@@ -39,7 +39,9 @@ iterator pair over non-contiguous but random-access storage (e.g. `#!cpp std::de
 optimization but not the second, since the byte-scanning fast path requires contiguous storage.

 Practically: a file can be passed directly to `parse`, which also avoids the memory for a copy of the file. Reading it
-into a string first is no longer necessary for speed:
+into a string first is no longer necessary for speed (this is for `#!cpp json::parse`; a
+[`json_document`](json_view.md) reads a stream into an owned buffer anyway, so for it reading the file into a string
+and borrowing that is the faster way):

 ```cpp
 // fast: the stream buffer's get area is scanned in bulk
@@ -17,6 +17,9 @@ To write a value directly to a stream (for example, a file or `#!cpp std::cout`)
 std::cout << j << std::endl;
 ```

+To write a file without leaving a truncated file behind when serialization fails, see
+[Reading and writing files](files.md#writing-a-json-file).
+
 !!! note "String, not raw value"

    `dump` always returns a **JSON text**. Serializing a JSON string therefore includes the surrounding quotes and
@@ -406,6 +406,7 @@ using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;
 | `#!cpp operator<<(std::ostream&, const json_pointer&)`                                                                            | streamability to `#!cpp std::ostream`                                                                                                                                                        |
 | [`to_string`](../../api/basic_json/to_string.md)                                                                                  | conversion of `StringType` to `#!cpp std::string` (the function returns a `#!cpp std::string`)                                                                                               |
 | exception messages                                                                                                                | `data()` and `size()`, or `begin()` and `end()`                                                                                                                                              |
+| [`basic_json_view::dump`](../../api/basic_json_view/dump.md)                                                                      | `reserve(n)` and `resize(n)` (one argument); `capacity()` is **not** required                                                                                                                |

 ### Compatible types

@@ -110,7 +110,7 @@ in the source files that need it, instantiate `basic_json` once, and consider pr
 The parser did not see any character: the file was most likely not opened. A relative path is resolved against the
 working directory of the running program, which is often the build directory of your IDE, not the source directory.
 Check `is_open()` and try an absolute path. Other causes are an empty file and a stream that was already read. See
-[`parse_error.101`](exceptions.md#jsonexceptionparse_error101).
+[`parse_error.101`](exceptions.md#jsonexceptionparse_error101) and [Reading and writing files](../features/files.md).

 ### Input that arrives in chunks

@@ -1,21 +1,21 @@
-<svg class="nj-fig nj-charts nj-charts--compile" viewBox="0 0 470 516" role="img" aria-labelledby="nj-charts-ct nj-charts-ct-d" xmlns="http://www.w3.org/2000/svg">
+<svg class="nj-fig nj-charts nj-charts--compile" viewBox="0 0 470 620" role="img" aria-labelledby="nj-charts-ct nj-charts-ct-d" xmlns="http://www.w3.org/2000/svg">
 <title id="nj-charts-ct">Change in compile time against the default configuration at -O0, Apple clang and G&#8203;CC 16</title>
-<desc id="nj-charts-ct-d">Grouped horizontal bars, negative is faster. json_fwd.hpp instead of json.hpp on a header-only translation unit: Apple clang -62 %, G&#8203;CC 16 -82 %; extern template on a parsing translation unit: Apple clang -7 %, G&#8203;CC 16 -21 %; JSON_NO_AUTOMATIC_UDLS on a model translation unit: Apple clang -11 %, G&#8203;CC 16 -11 %; JSON_NO_AUTOMATIC_UDLS on a parsing translation unit: Apple clang -1 %, G&#8203;CC 16 -2 %; JSON_HAS_FILESYSTEM=0 + JSON_NO_IO on a model translation unit: Apple clang -8 %, G&#8203;CC 16 -11 %; JSON_HAS_FILESYSTEM=0 on a model translation unit: Apple clang -5 %, G&#8203;CC 16 -9 %; JSON_NO_IO on a model translation unit: Apple clang -2 %, G&#8203;CC 16 -2 %; JSON_USE_GLOBAL_UDLS=0 on a model translation unit: Apple clang 0 %, G&#8203;CC 16 -1 %.</desc>
+<desc id="nj-charts-ct-d">Grouped horizontal bars, negative is faster. json_fwd.hpp instead of json.hpp on a header-only translation unit: Apple clang -62 %, G&#8203;CC 16 -82 %; extern template on a parsing translation unit: Apple clang -7 %, G&#8203;CC 16 -21 %; JSON_NO_AUTOMATIC_UDLS on a model translation unit: Apple clang -11 %, G&#8203;CC 16 -11 %; JSON_NO_AUTOMATIC_UDLS on a parsing translation unit: Apple clang -1 %, G&#8203;CC 16 -2 %; JSON_HAS_FILESYSTEM=0 + JSON_NO_IO on a model translation unit: Apple clang -8 %, G&#8203;CC 16 -11 %; JSON_HAS_FILESYSTEM=0 on a model translation unit: Apple clang -5 %, G&#8203;CC 16 -9 %; JSON_HAS_STD_FORMAT=0 on a model translation unit: Apple clang -1 %, G&#8203;CC 16 -4 %; JSON_HAS_RANGES=0 on a model translation unit: Apple clang -4 %, G&#8203;CC 16 -1 %; JSON_NO_IO on a model translation unit: Apple clang -2 %, G&#8203;CC 16 -2 %; JSON_USE_GLOBAL_UDLS=0 on a model translation unit: Apple clang 0 %, G&#8203;CC 16 -1 %.</desc>
 <rect class="nj-charts-clang" x="8" y="10" width="12" height="12" rx="3"/>
 <text class="nj-charts-leg" x="26" y="20.5">Apple clang</text>
 <rect class="nj-charts-gcc" x="126" y="10" width="12" height="12" rx="3"/>
 <text class="nj-charts-leg" x="144" y="20.5">G&#8203;CC 16</text>
-<line class="nj-charts-grid" x1="47.4" y1="58" x2="47.4" y2="472"/>
-<text class="nj-charts-tick" x="47.4" y="488">&#8722;80 %</text>
-<line class="nj-charts-grid" x1="126.2" y1="58" x2="126.2" y2="472"/>
-<text class="nj-charts-tick" x="126.2" y="488">&#8722;60 %</text>
-<line class="nj-charts-grid" x1="205" y1="58" x2="205" y2="472"/>
-<text class="nj-charts-tick" x="205" y="488">&#8722;40 %</text>
-<line class="nj-charts-grid" x1="283.8" y1="58" x2="283.8" y2="472"/>
-<text class="nj-charts-tick" x="283.8" y="488">&#8722;20 %</text>
-<text class="nj-charts-tick" x="362.6" y="488">0 %</text>
-<text class="nj-charts-tick nj-charts-tick--l" x="8" y="506">&#8592; faster</text>
-<text class="nj-charts-tick nj-charts-tick--r" x="462" y="506">slower &#8594;</text>
+<line class="nj-charts-grid" x1="47.4" y1="58" x2="47.4" y2="576"/>
+<text class="nj-charts-tick" x="47.4" y="592">&#8722;80 %</text>
+<line class="nj-charts-grid" x1="126.2" y1="58" x2="126.2" y2="576"/>
+<text class="nj-charts-tick" x="126.2" y="592">&#8722;60 %</text>
+<line class="nj-charts-grid" x1="205" y1="58" x2="205" y2="576"/>
+<text class="nj-charts-tick" x="205" y="592">&#8722;40 %</text>
+<line class="nj-charts-grid" x1="283.8" y1="58" x2="283.8" y2="576"/>
+<text class="nj-charts-tick" x="283.8" y="592">&#8722;20 %</text>
+<text class="nj-charts-tick" x="362.6" y="592">0 %</text>
+<text class="nj-charts-tick nj-charts-tick--l" x="8" y="610">&#8592; faster</text>
+<text class="nj-charts-tick nj-charts-tick--r" x="462" y="610">slower &#8594;</text>
 <text class="nj-charts-rowlabel" x="8" y="62"><tspan class="nj-charts-code">json_fwd.hpp instead of json.hpp</tspan><tspan class="nj-charts-sub"> &#183; header-only TU</tspan></text>
 <path class="nj-charts-clang" d="M362.6 70 H122.32 Q118.32 70 118.32 74 V78 Q118.32 82 122.32 82 H362.6 Z"><title>json_fwd.hpp instead of json.hpp, header-only TU (Apple clang): &#8722;62 %</title></path>
 <text class="nj-charts-val" x="367.6" y="80.5">&#8722;62 %</text>
@@ -46,15 +46,25 @@
 <text class="nj-charts-val" x="367.6" y="340.5">&#8722;5 %</text>
 <path class="nj-charts-gcc" d="M362.6 344 H331.14 Q327.14 344 327.14 348 V352 Q327.14 356 331.14 356 H362.6 Z"><title>JSON_HAS_FILESYSTEM=0, model TU (G&#8203;CC 16): &#8722;9 %</title></path>
 <text class="nj-charts-val" x="367.6" y="354.5">&#8722;9 %</text>
-<text class="nj-charts-rowlabel" x="8" y="374"><tspan class="nj-charts-code">JSON_NO_IO</tspan><tspan class="nj-charts-sub"> &#183; model TU*</tspan></text>
-<path class="nj-charts-clang" d="M362.6 382 H358.72 Q354.72 382 354.72 386 V390 Q354.72 394 358.72 394 H362.6 Z"><title>JSON_NO_IO, model TU (Apple clang): &#8722;2 %</title></path>
-<text class="nj-charts-val" x="367.6" y="392.5">&#8722;2 %</text>
-<path class="nj-charts-gcc" d="M362.6 396 H358.72 Q354.72 396 354.72 400 V404 Q354.72 408 358.72 408 H362.6 Z"><title>JSON_NO_IO, model TU (G&#8203;CC 16): &#8722;2 %</title></path>
-<text class="nj-charts-val" x="367.6" y="406.5">&#8722;2 %</text>
-<text class="nj-charts-rowlabel" x="8" y="426"><tspan class="nj-charts-code">JSON_USE_GLOBAL_UDLS=0</tspan><tspan class="nj-charts-sub"> &#183; model TU*</tspan></text>
-<path class="nj-charts-clang" d="M362.6 434 h0.5 v12 h-0.5 Z"><title>JSON_USE_GLOBAL_UDLS=0, model TU (Apple clang): 0 %</title></path>
-<text class="nj-charts-val" x="367.6" y="444.5">0 %</text>
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+<text class="nj-charts-rowlabel" x="8" y="374"><tspan class="nj-charts-code">JSON_HAS_STD_FORMAT=0</tspan><tspan class="nj-charts-sub"> &#183; model TU</tspan></text>
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+<text class="nj-charts-val" x="367.6" y="392.5">&#8722;1 %</text>
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+<text class="nj-charts-val" x="367.6" y="406.5">&#8722;4 %</text>
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+<path class="nj-charts-clang" d="M362.6 434 H350.84 Q346.84 434 346.84 438 V442 Q346.84 446 350.84 446 H362.6 Z"><title>JSON_HAS_RANGES=0, model TU (Apple clang): &#8722;4 %</title></path>
+<text class="nj-charts-val" x="367.6" y="444.5">&#8722;4 %</text>
+<path class="nj-charts-gcc" d="M362.6 448 H362.6 Q358.66 448 358.66 451.94 V456.06 Q358.66 460 362.6 460 H362.6 Z"><title>JSON_HAS_RANGES=0, model TU (G&#8203;CC 16): &#8722;1 %</title></path>
 <text class="nj-charts-val" x="367.6" y="458.5">&#8722;1 %</text>
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+<text class="nj-charts-rowlabel" x="8" y="478"><tspan class="nj-charts-code">JSON_NO_IO</tspan><tspan class="nj-charts-sub"> &#183; model TU*</tspan></text>
+<path class="nj-charts-clang" d="M362.6 486 H358.72 Q354.72 486 354.72 490 V494 Q354.72 498 358.72 498 H362.6 Z"><title>JSON_NO_IO, model TU (Apple clang): &#8722;2 %</title></path>
+<text class="nj-charts-val" x="367.6" y="496.5">&#8722;2 %</text>
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+<text class="nj-charts-val" x="367.6" y="510.5">&#8722;2 %</text>
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+<path class="nj-charts-clang" d="M362.6 538 h0.5 v12 h-0.5 Z"><title>JSON_USE_GLOBAL_UDLS=0, model TU (Apple clang): 0 %</title></path>
+<text class="nj-charts-val" x="367.6" y="548.5">0 %</text>
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+<text class="nj-charts-val" x="367.6" y="562.5">&#8722;1 %</text>
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 </svg>
@@ -11,6 +11,11 @@ that cost, ordered by how much they typically save.
    16.2.0 on macOS (Apple M1 Max). All configurations were run interleaved, in alternating order. They show the order
    of magnitude to expect; measure your own code before and after a change.

+    The two sections on `std::format` and ranges apply to C++20 only and were measured with `-std=c++20`, so their
+    baselines are slower than the others. Their differences are mostly within the run-to-run noise of a few percent:
+    two complete runs of the same configuration differed by up to 10% in the median. The tables show the later run (one
+    outlier cell was repeated).
+
    The translation units are listed below. They replace the ones used for earlier versions of this page, whose
    sources were not published, so the numbers differ from earlier versions.

@@ -66,7 +71,8 @@ that cost, ordered by how much they typically save.
 --8<-- "images/compile_times.svg"
 </div>
 <p class="nj-charts-caption" markdown>Change in compile time at `-O0` against the default configuration of the same
-translation unit, taken from the tables below (medians of nine runs, see above). * computed from the milliseconds in
+translation unit, taken from the tables below (medians of nine runs, see above; the `std::format` and ranges rows are
+measured with `-std=c++20`). * computed from the milliseconds in
 [Options without effect on compile times](#options-without-effect-on-compile-times).</p>

 ## Include `json_fwd.hpp` in headers
@@ -214,6 +220,88 @@ from and to `std::string`; whether that fallback exists depends on the platform'
 (`std::wstring` on Windows), so check code that converts paths. `JSON_NO_IO` additionally removes all stream
 functions (see [Options without effect](#options-without-effect-on-compile-times)).

+## Switch off `std::format` support
+
+With C++20 and a standard library that provides `<format>`, the library includes it to provide a
+[`std::formatter<basic_json>`](../api/basic_json/std_formatter.md) specialization (see
+[`JSON_HAS_STD_FORMAT`](../api/macros/json_has_std_format.md)). If you do not format JSON values with `std::format`,
+switch the detection off for the whole project:
+
+```cmake
+target_compile_definitions(my_target PRIVATE JSON_HAS_STD_FORMAT=0)
+```
+
+| Compiler    | Translation unit | Default (`-O0` / `-O2`) | `std::format` off (`-O0` / `-O2`) | Change     |
+|-------------|------------------|------------------------:|----------------------------------:|-----------:|
+| Apple clang | model            |       1283 ms / 1544 ms |                1269 ms / 1539 ms |  −1% / 0%  |
+| GCC 16      | model            |       2026 ms / 2482 ms |                1944 ms / 2416 ms | −4% / −3%  |
+| Apple clang | parsing          |       1350 ms / 2278 ms |                1347 ms / 2300 ms |  0% / +1%  |
+| GCC 16      | parsing          |       2715 ms / 4351 ms |                2644 ms / 4287 ms | −3% / −1%  |
+
+<p class="nj-table-caption" markdown>Compile time with `JSON_HAS_STD_FORMAT=0` against the default configuration, both with `-std=c++20`, at `-O0` and `-O2`.</p>
+
+The saving is small, and only GCC shows it: libstdc++'s `<format>` is an additional header that nothing else in the
+translation unit includes, so the macro removes it (and the headers it pulls in). With libc++ (Apple clang), other
+standard headers include `<format>` anyway, so the macro only removes the library's own formatter, and the difference is
+within the noise.
+
+The trade-off: the `std::formatter<basic_json>` specialization is removed, so `#!cpp std::format("{}", j)`,
+and `#!cpp std::format_to` with a JSON value no longer compile (in a test with both compilers on
+macOS, the error was that `std::formatter` must be specialized for the type). Use [`dump()`](../api/basic_json/dump.md),
+or the stream operators, instead.
+
+## Switch off ranges support
+
+With C++20 and a standard library that provides `<ranges>`, the library includes it to declare the
+[`items()`](../api/basic_json/items.md) proxy a *borrowed range*, and uses the `std::ranges` concepts and algorithms for
+construction from range views and for iterator input (see [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md)). If you
+do not need these, switch the detection off for the whole project:
+
+```cmake
+target_compile_definitions(my_target PRIVATE JSON_HAS_RANGES=0)
+```
+
+| Compiler    | Translation unit | Default (`-O0` / `-O2`) | Ranges off (`-O0` / `-O2`) | Change     |
+|-------------|------------------|------------------------:|---------------------------:|-----------:|
+| Apple clang | model            |       1283 ms / 1544 ms |           1237 ms / 1495 ms | −4% / −3%  |
+| GCC 16      | model            |       2026 ms / 2482 ms |           2004 ms / 2464 ms | −1% / −1%  |
+| Apple clang | parsing          |       1350 ms / 2278 ms |           1311 ms / 2284 ms |  −3% / 0%  |
+| GCC 16      | parsing          |       2715 ms / 4351 ms |           2705 ms / 4427 ms |  0% / +2%  |
+
+<p class="nj-table-caption" markdown>Compile time with `JSON_HAS_RANGES=0` against the default configuration, both with `-std=c++20`, at `-O0` and `-O2`.</p>
+
+The saving is small as well, and with GCC it is not distinguishable from the noise: its `<format>` includes `<span>`,
+so with `std::format` support left on, part of the ranges machinery is still parsed.
+Both macros together save more than either alone:
+
+```cmake
+target_compile_definitions(my_target PRIVATE JSON_HAS_STD_FORMAT=0 JSON_HAS_RANGES=0)
+```
+
+| Compiler    | Translation unit | Default (`-O0` / `-O2`) | Both off (`-O0` / `-O2`) | Change     |
+|-------------|------------------|------------------------:|-------------------------:|-----------:|
+| Apple clang | model            |       1283 ms / 1544 ms |         1223 ms / 1504 ms | −5% / −3%  |
+| GCC 16      | model            |       2026 ms / 2482 ms |         1914 ms / 2378 ms | −6% / −4%  |
+| Apple clang | parsing          |       1350 ms / 2278 ms |         1311 ms / 2271 ms |  −3% / 0%  |
+| GCC 16      | parsing          |       2715 ms / 4351 ms |         2635 ms / 4260 ms | −3% / −2%  |
+
+<p class="nj-table-caption" markdown>Compile time with `JSON_HAS_STD_FORMAT=0` and `JSON_HAS_RANGES=0` against the default configuration, both with `-std=c++20`, at `-O0` and `-O2`.</p>
+
+The trade-offs of `JSON_HAS_RANGES=0` are larger than those of the other options on this page:
+
+- `items()` is no longer a borrowed range. On a temporary, `#!cpp std::ranges::begin(make_json().items())` no longer
+  compiles, and `std::ranges` algorithms such as `#!cpp std::ranges::find_if(make_json().items(), pred)` return
+  `std::ranges::dangling` instead of an iterator, so code that uses the result no longer compiles. Calling them on
+  `#!cpp j.items()` for a named `j` is not affected.
+- [`JSON_HAS_RANGE_VIEW_CONVERSION`](../api/macros/json_has_range_view_conversion.md) becomes `0`, so a JSON array can no
+  longer be constructed from a `std::ranges::view` such as the result of `std::views::filter`. The assignment
+  `#!cpp json j = v | std::views::filter(pred);` no longer compiles.
+- Parsing from an iterator pair loses the C++20 fast path for contiguous iterators that are not pointers (for
+  example those of `std::vector`) and falls back to byte-at-a-time scanning. The result is the same; parsing may be
+  slower (not measured here).
+
+The first two were checked with both compilers on macOS; the third is read from the library's source.
+
 ## Use C++20 modules

 With a toolchain that supports named modules, `import nlohmann.json;` compiles the library once into a module and
@@ -343,6 +431,8 @@ and −2% / 0% (GCC). To get a saving, combine it with

 - [`JSON_HAS_FILESYSTEM`](../api/macros/json_has_filesystem.md) - control the conversions from and to
  `std::filesystem::path`
+- [`JSON_HAS_STD_FORMAT`](../api/macros/json_has_std_format.md) - control the `std::formatter` specialization
+- [`JSON_HAS_RANGES`](../api/macros/json_has_ranges.md) - control the use of `std::ranges`
 - [`JSON_NO_AUTOMATIC_UDLS`](../api/macros/json_no_automatic_udls.md) - do not include the user-defined string
  literals automatically
 - [Modules](../features/modules.md) - C++20 module support
@@ -130,6 +130,7 @@ nav:
          - features/element_access/unchecked_access.md
          - features/element_access/checked_access.md
          - features/element_access/default_value.md
+      - features/files.md
      - features/iterators.md
      - features/merge_patch.md
      - features/json_patch.md
@@ -142,7 +143,6 @@ nav:
      - features/performance.md
      - Parsing:
          - features/parsing/index.md
-          - features/parsing/error_recovery.md
          - features/parsing/json_lines.md
          - features/parsing/large_and_partial_input.md
          - features/parsing/parse_exceptions.md
@@ -1,8 +1,8 @@
 wheel==0.48.0

 mkdocs==1.6.1                                       # documentation framework
-mkdocs-git-revision-date-localized-plugin==1.6.0    # plugin "git-revision-date-localized"
-mkdocs-material==9.7.7                             # theme for mkdocs
+mkdocs-git-revision-date-localized-plugin==1.6.2    # plugin "git-revision-date-localized"
+mkdocs-material==9.8.0                             # theme for mkdocs
 mkdocs-material-extensions==1.3.1                   # extensions
 mkdocs-minify-plugin==0.8.0                         # plugin "minify"
 mkdocs-redirects==1.2.3                             # plugin "redirects"
@@ -73,6 +73,8 @@ COMPILE = [
    ("JSON_NO_AUTOMATIC_UDLS", "parsing TU", -1, -2, False),
    ("JSON_HAS_FILESYSTEM=0 + JSON_NO_IO", "model TU", -8, -11, False),
    ("JSON_HAS_FILESYSTEM=0", "model TU", -5, -9, False),
+    ("JSON_HAS_STD_FORMAT=0", "model TU", -1, -4, False),
+    ("JSON_HAS_RANGES=0", "model TU", -4, -1, False),
    # computed from the ms in "Options without effect on compile times": 1034/1051, 1756/1801, 1055/1051, 1783/1801
    ("JSON_NO_IO", "model TU", round((1034 / 1051 - 1) * 100), round((1756 / 1801 - 1) * 100), True),
    ("JSON_USE_GLOBAL_UDLS=0", "model TU", round((1055 / 1051 - 1) * 100), round((1783 / 1801 - 1) * 100), True),
@@ -91,7 +91,7 @@ const typename BasicJsonType::binary_t& binary_value(const BasicJsonType& j)
 }

 template<typename View, enable_if_t<is_json_view<View>::value, int> = 0>
-typename View::basic_json_type::binary_t binary_value(const View& /*unused*/)
+typename View::basic_json_type::binary_t binary_value(const View& /*unused*/) // LCOV_EXCL_LINE
 {
    return {}; // LCOV_EXCL_LINE
 }
@@ -198,18 +198,19 @@ class exception : public std::exception
            // all other parent types (primitives) contribute no token
        }

-        if (tokens.empty())
+        // the root value has no path, but still has a byte range
+        std::string prefix;
+        if (!tokens.empty())
        {
-            return "";
+            const auto str = std::accumulate(tokens.rbegin(), tokens.rend(), std::string{},
+                                             [](const std::string & a, const std::string & b)
+            {
+                return concat(a, '/', detail::escape(b));
+            });
+            prefix = concat('(', str, ") ");
        }

-        auto str = std::accumulate(tokens.rbegin(), tokens.rend(), std::string{},
-                                   [](const std::string & a, const std::string & b)
-        {
-            return concat(a, '/', detail::escape(b));
-        });
-
-        return concat('(', str, ") ", get_byte_positions(leaf_element));
+        return concat(prefix, get_byte_positions(leaf_element));
 #else
        return get_byte_positions(leaf_element);
 #endif
@@ -222,7 +223,8 @@ class exception : public std::exception
    template<typename BasicJsonType>
    static std::string get_byte_positions(const BasicJsonType* leaf_element)
    {
-        if ((leaf_element->start_pos() != std::string::npos) && (leaf_element->end_pos() != std::string::npos))
+        // a value-initialized iterator has no value (invalid_iterator.212)
+        if (leaf_element != nullptr && leaf_element->start_pos() != std::string::npos && leaf_element->end_pos() != std::string::npos)
        {
            return concat("(bytes ", std::to_string(leaf_element->start_pos()), "-", std::to_string(leaf_element->end_pos()), ") ");
        }
@@ -545,12 +545,9 @@ class input_stream_adapter
    std::char_traits<char>::int_type get_character_slow()
    {
 #if !JSON_DISABLE_STREAM_BULK_SCAN
-        // sbumpc() refills the get area if it is exhausted
-        const bool refill = streambuf_access::get_ptr(sb) == streambuf_access::get_end(sb);
-        if (JSON_HEDLEY_UNLIKELY(refill))
-        {
-            save_token_segment();
-        }
+        // the get area is exhausted (get_character() handles the other case),
+        // so sbumpc() refills it
+        save_token_segment();
 #endif

        auto res = sb->sbumpc();
@@ -563,17 +560,13 @@ class input_stream_adapter
            is->clear(is->rdstate() | std::ios::eofbit);
        }
 #if !JSON_DISABLE_STREAM_BULK_SCAN
-        else if (JSON_HEDLEY_UNLIKELY(refill))
+        else
        {
            // the consumed character is at gptr() - 1, unless the streambuf
            // has no get area and returned it from uflow()
            const char* const next = streambuf_access::get_ptr(sb);
            after_refill(res, next != nullptr && next != streambuf_access::get_begin(sb));
        }
-        else
-        {
-            current_in_get_area = true;
-        }
 #endif
        return res;
    }
@@ -796,22 +789,17 @@ class iterator_input_adapter
        return get_consumed_count() + eof_reads;
    }

-    // number of newlines in the consumed range [first_index, last_index); if
-    // there is one, @a line_start is set to the index after the last of them,
-    // otherwise it is left unchanged; only valid when supports_seek
-    std::size_t count_consumed_lines(std::size_t first_index, std::size_t last_index, std::size_t& line_start) const
+    // number of newlines in the consumed range [0, last_index); @a line_start
+    // is set to the index after the last of them (0 if there is none); only
+    // valid when supports_seek
+    std::size_t count_consumed_lines(std::size_t last_index, std::size_t& line_start) const
    {
-        using difference_type = typename std::iterator_traits<IteratorType>::difference_type;
-        const auto from = std::next(begin, static_cast<difference_type>(first_index));
-        const auto to = std::next(from, static_cast<difference_type>(last_index - first_index));
+        const auto to = std::next(begin, static_cast<typename std::iterator_traits<IteratorType>::difference_type>(last_index));
        const auto newline = char_traits<char_type>::to_char_type('\n');
        using reverse_it = std::reverse_iterator<IteratorType>;
-        const auto last_newline = std::find(reverse_it(to), reverse_it(from), newline);
-        if (last_newline.base() != from)
-        {
-            line_start = static_cast<std::size_t>(std::distance(begin, last_newline.base()));
-        }
-        return static_cast<std::size_t>(std::count(from, last_newline.base(), newline));
+        const auto last_newline = std::find(reverse_it(to), reverse_it(begin), newline);
+        line_start = static_cast<std::size_t>(std::distance(begin, last_newline.base()));
+        return static_cast<std::size_t>(std::count(begin, last_newline.base(), newline));
    }

    // append the already-consumed characters in the half-open range
@@ -138,9 +138,7 @@ struct json_sax
    @param[in] position    the position in the input where the error occurs
    @param[in] last_token  the last read token
    @param[in] ex          an exception object describing the error
-    @return whether to recover from the error: false stops parsing; true
-            repairs the error and continues, or, if that is not possible,
-            stops after completing the value read so far
+    @return whether parsing should proceed (must return false)
    */
    virtual bool parse_error(std::size_t position,
                             const std::string& last_token,
@@ -487,9 +485,6 @@ stored in place as it arrives, so after a parse error the value holds what was
 read up to it.

@tparam BasicJsonType  the JSON type
-@tparam InputAdapterType  the input adapter of the lexer that can be passed to
-                          the constructor to record diagnostic positions; it
-                          does not matter if no lexer is passed
@tparam Collect  whether to collect the values of containers of unknown size on
                 a stack (only for a caller that does not use the value after a
                 parse error)
@@ -498,7 +493,7 @@ read up to it.
                   it, so any type with its three functions works (as
                   materialize() of json_view uses it)
 */
-template<typename BasicJsonType, typename InputAdapterType = string_input_adapter_type, bool Collect = false, typename LexerType = lexer<BasicJsonType, InputAdapterType>>
+template<typename BasicJsonType, typename InputAdapterType, bool Collect = false, typename LexerType = lexer<BasicJsonType, InputAdapterType>>
 class json_sax_dom_parser : public json_sax_dom_error_state
 {
  public:
@@ -804,8 +799,6 @@ class json_sax_dom_parser : public json_sax_dom_error_state
        JSON_HEDLEY_NEVER_INLINE
        void grow()
        {
-            // the stack starts with local_capacity frames and only grows
-            JSON_ASSERT(capacity != 0);
            const std::size_t new_capacity = capacity * 2;
            std::unique_ptr<frame[]> new_heap(new frame[new_capacity]); // NOLINT(cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays)
            for (std::size_t i = 0; i < count; ++i)
@@ -911,7 +904,8 @@ class json_sax_dom_parser : public json_sax_dom_error_state
            {
                hashes.push_back(hasher(element.first));
            }
-            ordered_data.key_indexes.emplace_back(new object_key_index(std::move(hashes)));
+            std::unique_ptr<object_key_index> index(new object_key_index(std::move(hashes))); // NOLINT(cppcoreguidelines-owning-memory,modernize-make-unique): std::make_unique is C++14
+            ordered_data.key_indexes.push_back(std::move(index));
            f.ordered.index = ordered_data.key_indexes.back().get();
        }

@@ -1006,7 +1000,7 @@ class json_sax_dom_parser : public json_sax_dom_error_state
        ordered_data.members[f.ordered.dest_member].second = std::move(value);
    }

-    static void place_member(const frame& /*f*/, BasicJsonType&& /*value*/, std::false_type /*indexed*/) noexcept {}
+    static void place_member(const frame& /*f*/, BasicJsonType&& /*value*/, std::false_type /*indexed*/) noexcept {} // LCOV_EXCL_LINE

    /// store the members of a new object directly in it
    bool start_stored_object(std::size_t len)
@@ -1310,7 +1304,7 @@ class json_sax_dom_parser : public json_sax_dom_error_state
        {
            // a new member is null and holds nothing: construct the value
            // over it instead of destroying and swapping
-            ::new (static_cast<void*>(&member)) BasicJsonType(std::forward<Value>(v));
+            construct_member(member, std::forward<Value>(v), std::is_nothrow_constructible<BasicJsonType, Value> {});
        }
        else
        {
@@ -1319,6 +1313,26 @@ class json_sax_dom_parser : public json_sax_dom_error_state
        }
    }

+    /// constructing the value cannot throw (for example a number or a boolean): construct it in place
+    template<typename Value>
+    JSON_HEDLEY_ALWAYS_INLINE
+    static void construct_member(BasicJsonType& member, Value&& v, std::true_type /*nothrow*/)
+    {
+        ::new (static_cast<void*>(&member)) BasicJsonType(std::forward<Value>(v));
+    }
+
+    /// constructing the value can throw (for example a container or a string), and a
+    /// constructor that was interrupted must not have touched the member (#5985):
+    /// create the value first, then move it over the member (the move constructor is
+    /// noexcept)
+    template<typename Value>
+    JSON_HEDLEY_ALWAYS_INLINE
+    static void construct_member(BasicJsonType& member, Value&& v, std::false_type /*may throw*/)
+    {
+        BasicJsonType value(std::forward<Value>(v));
+        ::new (static_cast<void*>(&member)) BasicJsonType(std::move(value));
+    }
+
    /// a custom base class may care about the lifetime of the value
    template<typename Value>
    static void set_member(BasicJsonType& member, Value&& v, std::false_type /*custom base*/)
@@ -1621,7 +1635,7 @@ class json_sax_dom_binary_parser : public json_sax_dom_error_state
    lexer_t* m_lexer_ref = nullptr;
 };

-template<typename BasicJsonType, typename InputAdapterType = string_input_adapter_type>
+template<typename BasicJsonType, typename InputAdapterType>
 class json_sax_dom_callback_parser : public json_sax_dom_error_state
 {
  public:
@@ -1744,7 +1758,7 @@ class json_sax_dom_callback_parser : public json_sax_dom_error_state
        key_stack.push_back(val);

        // add discarded value at the given key and store the reference for later
-        if (keep && ref_stack.back())
+        if (keep)
        {
            auto& obj = *ref_stack.back()->m_data.m_value.object;
            // a single lookup: insert the placeholder, or find the existing member
@@ -1801,7 +1815,7 @@ class json_sax_dom_callback_parser : public json_sax_dom_error_state

        const string_t object_key = pop_container();

-        if (!ref_stack.empty() && ref_stack.back() && ref_stack.back()->is_structured())
+        if (!ref_stack.empty() && ref_stack.back())
        {
            // remove discarded value
            remove_discarded_value(*ref_stack.back(), object_key);
@@ -1967,8 +1981,7 @@ class json_sax_dom_callback_parser : public json_sax_dom_error_state
    */
    string_t current_key() const
    {
-        if (!ref_stack.empty() && ref_stack.back() && ref_stack.back()->is_object()
-                && !key_stack.empty())
+        if (!ref_stack.empty() && ref_stack.back() && ref_stack.back()->is_object())
        {
            return key_stack.back();
        }
@@ -10,7 +10,7 @@

 #include <array> // array
 #include <cstddef> // size_t
-#include <cstdint> // uint8_t, uint32_t
+#include <cstdint> // uint32_t
 #include <cstdio> // snprintf
 #include <cstring> // memcmp
 #include <initializer_list> // initializer_list
@@ -300,14 +300,16 @@ class lexer : public lexer_base<BasicJsonType>
    /// calls would (including the position and token bookkeeping of a
    /// streaming adapter, see bulk_consume) and leaves @a current holding the last of
    /// the 4 digits, just as the last such get() would; the codepoint is
-    /// written to @a out. Makes no state change and returns false for a
-    /// pending unget, fewer than 4 remaining bytes, or any of the 4 bytes not
-    /// being a hex digit, so the caller falls back unchanged to the
-    /// per-character loop, which then reports the same diagnostic (stopping
-    /// at the first invalid digit) as before this optimization.
+    /// written to @a out. Makes no state change and returns false for fewer
+    /// than 4 remaining bytes or any of the 4 bytes not being a hex digit, so
+    /// the caller falls back unchanged to the per-character loop, which then
+    /// reports the same diagnostic (stopping at the first invalid digit) as
+    /// before this optimization.
    bool get_codepoint_bulk(std::true_type /*bulk*/, int& out)
    {
-        if (next_unget || ia.bulk_remaining() < 4)
+        // no unget is pending inside a string (see get_after_string_run())
+        JSON_ASSERT(!next_unget);
+        if (ia.bulk_remaining() < 4)
        {
            return false;
        }
@@ -385,20 +387,6 @@ class lexer : public lexer_base<BasicJsonType>
        return codepoint;
    }

-    /// the code point of the surrogate pair @a high (U+D800..U+DBFF) and @a low (U+DC00..U+DFFF)
-    static constexpr int combine_surrogates(const int high, const int low) noexcept
-    {
-        return static_cast<int>(
-                   // high surrogate occupies the most significant 22 bits
-                   (static_cast<unsigned int>(high) << 10u)
-                   // low surrogate occupies the least significant 15 bits
-                   + static_cast<unsigned int>(low)
-                   // there is still the 0xD800, 0xDC00, and 0x10000 noise
-                   // in the result, so we have to subtract with:
-                   // (0xD800 << 10) + DC00 - 0x10000 = 0x35FDC00
-                   - 0x35FDC00u);
-    }
-
    /*!
    @brief check if the next byte(s) are inside a given range

@@ -432,7 +420,6 @@ class lexer : public lexer_base<BasicJsonType>
            else
            {
                error_message = "invalid string: ill-formed UTF-8 byte";
-                error_cause = error_kind::string_ill_formed_utf8;
                return false;
            }
        }
@@ -452,11 +439,10 @@ class lexer : public lexer_base<BasicJsonType>
    template<bool Keep>
    char_int_type get_after_string_run(std::true_type /*bulk*/, std::integral_constant<bool, Keep> keep)
    {
-        // a pending unget must be consumed through the normal path first
-        if (next_unget)
-        {
-            return get();
-        }
+        // scan_string() is entered from scan_after_whitespace(), whose current
+        // was read by skip_whitespace() (its first get() clears a pending
+        // unget), and nothing in scan_string() calls unget()
+        JSON_ASSERT(!next_unget);
        const std::size_t remaining = ia.bulk_remaining();
        if (remaining == 0)
        {
@@ -556,7 +542,6 @@ class lexer : public lexer_base<BasicJsonType>
                case char_traits<char_type>::eof():
                {
                    error_message = "invalid string: missing closing quote";
-                    error_cause = error_kind::string;
                    return token_type::parse_error;
                }

@@ -613,7 +598,6 @@ class lexer : public lexer_base<BasicJsonType>
                            if (JSON_HEDLEY_UNLIKELY(codepoint1 == -1))
                            {
                                error_message = "invalid string: '\\u' must be followed by 4 hex digits";
-                                error_cause = error_kind::string_invalid_escape;
                                return token_type::parse_error;
                            }

@@ -621,23 +605,13 @@ class lexer : public lexer_base<BasicJsonType>
                            if (0xD800 <= codepoint1 && codepoint1 <= 0xDBFF)
                            {
                                // expect next \uxxxx entry
-                                if (JSON_HEDLEY_LIKELY(get() == '\\'))
+                                if (JSON_HEDLEY_LIKELY(get() == '\\' && get() == 'u'))
                                {
-                                    if (JSON_HEDLEY_UNLIKELY(get() != 'u'))
-                                    {
-                                        // current is the character escaped by the backslash
-                                        error_message = "invalid string: surrogate U+D800..U+DBFF must be followed by U+DC00..U+DFFF";
-                                        error_cause = error_kind::string_invalid_escape;
-                                        string_error_resume = resume_kind::escaped_character;
-                                        return token_type::parse_error;
-                                    }
-
                                    const int codepoint2 = get_codepoint();

                                    if (JSON_HEDLEY_UNLIKELY(codepoint2 == -1))
                                    {
                                        error_message = "invalid string: '\\u' must be followed by 4 hex digits";
-                                        error_cause = error_kind::string_invalid_escape;
                                        return token_type::parse_error;
                                    }

@@ -645,23 +619,25 @@ class lexer : public lexer_base<BasicJsonType>
                                    if (JSON_HEDLEY_LIKELY(0xDC00 <= codepoint2 && codepoint2 <= 0xDFFF))
                                    {
                                        // overwrite codepoint
-                                        codepoint = combine_surrogates(codepoint1, codepoint2);
+                                        codepoint = static_cast<int>(
+                                                        // high surrogate occupies the most significant 22 bits
+                                                        (static_cast<unsigned int>(codepoint1) << 10u)
+                                                        // low surrogate occupies the least significant 15 bits
+                                                        + static_cast<unsigned int>(codepoint2)
+                                                        // there is still the 0xD800, 0xDC00, and 0x10000 noise
+                                                        // in the result, so we have to subtract with:
+                                                        // (0xD800 << 10) + DC00 - 0x10000 = 0x35FDC00
+                                                        - 0x35FDC00u);
                                    }
                                    else
                                    {
-                                        // the second escape was read completely and is a
-                                        // code point of its own
                                        error_message = "invalid string: surrogate U+D800..U+DBFF must be followed by U+DC00..U+DFFF";
-                                        error_cause = error_kind::string_invalid_escape;
-                                        string_error_resume = resume_kind::after_escape;
-                                        string_error_codepoint = codepoint2;
                                        return token_type::parse_error;
                                    }
                                }
                                else
                                {
                                    error_message = "invalid string: surrogate U+D800..U+DBFF must be followed by U+DC00..U+DFFF";
-                                    error_cause = error_kind::string_invalid_escape;
                                    return token_type::parse_error;
                                }
                            }
@@ -669,10 +645,7 @@ class lexer : public lexer_base<BasicJsonType>
                            {
                                if (JSON_HEDLEY_UNLIKELY(0xDC00 <= codepoint1 && codepoint1 <= 0xDFFF))
                                {
-                                    // the escape was read completely
                                    error_message = "invalid string: surrogate U+DC00..U+DFFF must follow U+D800..U+DBFF";
-                                    error_cause = error_kind::string_invalid_escape;
-                                    string_error_resume = resume_kind::after_escape;
                                    return token_type::parse_error;
                                }
                            }
@@ -689,7 +662,6 @@ class lexer : public lexer_base<BasicJsonType>
                        // other characters after escape
                        default:
                            error_message = "invalid string: forbidden character after backslash";
-                            error_cause = error_kind::string;
                            return token_type::parse_error;
                    }

@@ -766,7 +738,6 @@ class lexer : public lexer_base<BasicJsonType>
                        }
                    };
                    error_message = control_character_messages[static_cast<std::size_t>(current)];
-                    error_cause = error_kind::string;
                    return token_type::parse_error;
                }

@@ -989,7 +960,6 @@ class lexer : public lexer_base<BasicJsonType>
                default:
                {
                    error_message = "invalid string: ill-formed UTF-8 byte";
-                    error_cause = error_kind::string_ill_formed_utf8;
                    return token_type::parse_error;
                }
            }
@@ -1045,7 +1015,6 @@ class lexer : public lexer_base<BasicJsonType>
                        case char_traits<char_type>::eof():
                        {
                            error_message = "invalid comment; missing closing '*/'";
-                            error_cause = error_kind::unclosed_comment;
                            return false;
                        }

@@ -1076,7 +1045,6 @@ class lexer : public lexer_base<BasicJsonType>
            default:
            {
                error_message = "invalid comment; expecting '/' or '*' after '/'";
-                error_cause = error_kind::other;
                return false;
            }
        }
@@ -1202,7 +1170,6 @@ scan_number_minus:
            default:
            {
                error_message = "invalid number; expected digit after '-'";
-                error_cause = error_kind::number;
                return token_type::parse_error;
            }
        }
@@ -1289,7 +1256,6 @@ scan_number_decimal1:
            default:
            {
                error_message = "invalid number; expected digit after '.'";
-                error_cause = error_kind::number;
                return token_type::parse_error;
            }
        }
@@ -1358,7 +1324,6 @@ scan_number_exponent:
            {
                error_message =
                    "invalid number; expected '+', '-', or digit after exponent";
-                error_cause = error_kind::number;
                return token_type::parse_error;
            }
        }
@@ -1385,7 +1350,6 @@ scan_number_sign:
            default:
            {
                error_message = "invalid number; expected digit after exponent sign";
-                error_cause = error_kind::number;
                return token_type::parse_error;
            }
        }
@@ -1447,7 +1411,7 @@ scan_number_done:
                return token_type::value_unsigned;
            }
        }
-        else if (number_type == token_type::value_integer)
+        else // value_integer (the callers handle value_float themselves)
        {
            if (parse_integer_signed(first, last, value_integer))
            {
@@ -1553,11 +1517,9 @@ scan_number_done:
    */
    token_type scan_number_bulk_contiguous()
    {
-        // a pending unget offsets the buffer position from current; fall back
-        if (next_unget)
-        {
-            return token_type::uninitialized;
-        }
+        // called right after scan_after_whitespace() read current (see
+        // get_after_string_run()), so no unget is pending
+        JSON_ASSERT(!next_unget);
        const std::size_t rem = ia.bulk_remaining();
        if (rem == 0)
        {
@@ -1578,11 +1540,7 @@ scan_number_done:
        if (data[0] == '-')
        {
            number_type = token_type::value_integer;
-            i = 1;
-            if (i >= avail)
-            {
-                return token_type::uninitialized;
-            }
+            i = 1; // avail >= 2: rem == 0 returned above
        }
        const std::size_t integer_begin = i;
        if (data[i] == '0')
@@ -1813,7 +1771,6 @@ scan_number_done:
            if (JSON_HEDLEY_UNLIKELY(char_traits<char_type>::to_char_type(get()) != static_cast<char_type>(rest[i])))
            {
                error_message = "invalid literal";
-                error_cause = error_kind::other;
                return token_type::parse_error;
            }
        }
@@ -1825,7 +1782,10 @@ scan_number_done:
    /// the error at the right character
    JSON_HEDLEY_ALWAYS_INLINE bool scan_literal_bulk(const char* rest, const std::size_t length, std::true_type /*bulk*/)
    {
-        if (next_unget || ia.bulk_remaining() < length
+        // called right after scan_after_whitespace() read current (see
+        // get_after_string_run()), so no unget is pending
+        JSON_ASSERT(!next_unget);
+        if (ia.bulk_remaining() < length
                || std::memcmp(ia.bulk_data(), rest, length) != 0)
        {
            return false;
@@ -2232,25 +2192,17 @@ scan_number_done:
        return position.chars_read_total;
    }

-    /// seekable adapter: count the lines in the consumed input. Only the
-    /// input consumed since the previous call is scanned, so a parse that
-    /// reports many errors (a SAX parser recovering from them) stays linear
-    /// in the input instead of rescanning it for every error.
+    /// seekable adapter: count the lines in the consumed input; O(input read
+    /// so far), but only called on errors
    position_t get_position_impl(std::true_type /*lazy*/) const
    {
        position_t result;
        result.chars_read_total = get_chars_read_total();
        // reads at EOF count as characters but are not part of the input
        const std::size_t consumed = (std::min)(result.chars_read_total, ia.get_consumed_count());
-        if (JSON_HEDLEY_UNLIKELY(consumed < position_cache.consumed))
-        {
-            // the consumed input never shrinks; recount from the start if it did
-            position_cache = {};
-        }
-        position_cache.lines += ia.count_consumed_lines(position_cache.consumed, consumed, position_cache.line_start);
-        position_cache.consumed = consumed;
-        result.lines_read = position_cache.lines;
-        result.chars_read_current_line = result.chars_read_total - position_cache.line_start;
+        std::size_t line_start = 0;
+        result.lines_read = ia.count_consumed_lines(consumed, line_start);
+        result.chars_read_current_line = result.chars_read_total - line_start;
        return result;
    }

@@ -2434,7 +2386,6 @@ scan_number_done:
        if (get_chars_read_total() == 0 && !skip_bom())
        {
            error_message = "invalid BOM; must be 0xEF 0xBB 0xBF if given";
-            error_cause = error_kind::other;
            return token_type::parse_error;
        }

@@ -2544,583 +2495,10 @@ scan_number_done:
            // error
            default:
                error_message = "invalid literal";
-                error_cause = error_kind::other;
                return token_type::parse_error;
        }
    }

-  public:
-    /////////////////////
-    // error recovery
-    /////////////////////
-
-    /*!
-    @brief make the best of the token that scan() rejected
-
-    Called by the parser after scan() returned token_type::parse_error and the
-    SAX parser asked to recover from the error (see #3989). Keeps what can be
-    read of the token and skips the rest:
-
-    - A string keeps its characters. An unknown escape stands for the escaped
-      character itself (as in JavaScript), an invalid Unicode escape and ill-formed
-      UTF-8 become U+FFFD, and a control character is kept. A line break or the
-      end of the input ends a string that lacks its closing quote.
-    - A number keeps its longest valid prefix, e.g. `1` for `1.` or `1e+`.
-    - A block comment that is not closed runs to the end of the input.
-    - Anything else is skipped.
-
-    The rest of an invalid token is skipped up to the next delimiter
-    (whitespace, a structural character, or a quote). A delimiter that the
-    invalid token consumed is returned to the input, so that the next scan()
-    reads it.
-
-    @return token_type::value_string or a number token type if a string or a
-            number could be read, token_type::end_of_input for a block comment
-            that is not closed, token_type::uninitialized otherwise
-    */
-    token_type recover_token()
-    {
-        const resume_kind resume = string_error_resume;
-        const int codepoint = string_error_codepoint;
-        string_error_resume = resume_kind::character;
-        string_error_codepoint = -1;
-
-        const error_kind cause = error_cause;
-        error_cause = error_kind::other;
-
-        switch (cause)
-        {
-            case error_kind::string:
-            case error_kind::string_invalid_escape:
-            case error_kind::string_ill_formed_utf8:
-                return recover_string(cause, resume, codepoint);
-
-            case error_kind::number:
-                return recover_number();
-
-            case error_kind::unclosed_comment:
-                // the comment runs to the end of the input
-                return token_type::end_of_input;
-
-            case error_kind::other:
-            default:
-                skip_to_delimiter();
-                return token_type::uninitialized;
-        }
-    }
-
-    /*!
-    @brief return the token that scan() read last to the input, so that the
-           next scan() reads it again
-
-    Called by the parser when recovering from an error. The token must be a
-    single character (',', ':', '[', ']', '{', or '}') or the end of the
-    input, and scan() must have read it last.
-    */
-    void unget_token()
-    {
-        JSON_ASSERT(!next_unget);
-        unget();
-    }
-
-    /*!
-    @brief let the token string for the next error begin at the current character
-
-    The token string of an error reaches back to the beginning of the last
-    string or number. After an error, the parser calls this function so that
-    the next error does not report (and, with many errors, copy) everything
-    read since then.
-    */
-    void restart_token_string()
-    {
-        restart_token_string_impl(std::integral_constant<bool, lazy_token_string> {});
-    }
-
-  private:
-    /// how recover_string() continues after the error scan_string() reported
-    enum class resume_kind : std::uint8_t
-    {
-        /// current is the next character of the string (or the end of input)
-        character,
-        /// current is the character escaped by the preceding backslash
-        escaped_character,
-        /// current is the last character of a complete escape
-        after_escape
-    };
-
-    /// what kind of token scan() rejected, which decides how recover_token() repairs it
-    enum class error_kind : std::uint8_t
-    {
-        /// anything not listed below; skipped up to the next delimiter
-        other,
-        /// a string
-        string,
-        /// a string with an invalid Unicode escape, which becomes U+FFFD
-        string_invalid_escape,
-        /// a string with ill-formed UTF-8, which becomes U+FFFD
-        string_ill_formed_utf8,
-        /// a number
-        number,
-        /// a block comment that is not closed
-        unclosed_comment
-    };
-
-    /// whether current ends an invalid token (see recover_token())
-    bool current_is_delimiter() const noexcept
-    {
-        switch (current)
-        {
-            case ' ':
-            case '\t':
-            case '\n':
-            case '\r':
-            case '[':
-            case ']':
-            case '{':
-            case '}':
-            case ',':
-            case ':':
-            case '\"':
-#if !JSON_STRICT_NUL_HANDLING
-            case '\0':
-#endif
-            case char_traits<char_type>::eof():
-                return true;
-
-            case '/':
-                return ignore_comments;
-
-            default:
-                return false;
-        }
-    }
-
-    /// skip the rest of an invalid token and return its delimiter to the input
-    void skip_to_delimiter()
-    {
-        while (!current_is_delimiter())
-        {
-            get();
-        }
-
-        if (current != char_traits<char_type>::eof())
-        {
-            unget();
-        }
-    }
-
-    /// append U+FFFD REPLACEMENT CHARACTER to token_buffer
-    void add_replacement_character()
-    {
-        add_codepoint(0xFFFD);
-    }
-
-    /// append the UTF-8 encoding of @a codepoint (not a surrogate) to token_buffer
-    void add_codepoint(const int codepoint)
-    {
-        JSON_ASSERT(0x00 <= codepoint && codepoint <= 0x10FFFF);
-        encode_utf8(static_cast<std::uint32_t>(codepoint), [this](std::uint32_t byte)
-        {
-            add(static_cast<char_int_type>(byte));
-        });
-    }
-
-    /// append a code point read from a Unicode escape; a surrogate becomes U+FFFD
-    void add_escaped_codepoint(const int codepoint)
-    {
-        if (0xD800 <= codepoint && codepoint <= 0xDFFF)
-        {
-            add_replacement_character();
-        }
-        else
-        {
-            add_codepoint(codepoint);
-        }
-    }
-
-    /*!
-    @brief remove an incomplete UTF-8 sequence from the end of token_buffer
-
-    next_byte_in_range() adds the bytes of a sequence as it checks them, so
-    when it rejects a byte, the beginning of the sequence is already in
-    token_buffer, which otherwise holds only complete sequences.
-
-    @return whether an incomplete sequence was removed
-    */
-    bool remove_incomplete_utf8_sequence()
-    {
-        std::size_t lead = token_buffer.size();
-        std::size_t continuation_bytes = 0;
-        while (lead > 0 && continuation_bytes < 3
-                && (static_cast<unsigned char>(token_buffer[lead - 1]) & 0xC0u) == 0x80u)
-        {
-            --lead;
-            ++continuation_bytes;
-        }
-        if (lead == 0)
-        {
-            return false;
-        }
-
-        const auto lead_byte = static_cast<unsigned char>(token_buffer[lead - 1]);
-        std::size_t expected = 0;
-        if (lead_byte >= 0xF0)
-        {
-            expected = 3;
-        }
-        else if (lead_byte >= 0xE0)
-        {
-            expected = 2;
-        }
-        else if (lead_byte >= 0xC0)
-        {
-            expected = 1;
-        }
-        if (continuation_bytes >= expected)
-        {
-            return false;
-        }
-
-        token_buffer.resize(lead - 1);
-        return true;
-    }
-
-    /*!
-    @brief read the UTF-8 sequence that begins with current, which is not ASCII
-    @return whether the next character must be read; false if current still
-            needs to be handled, because it does not belong to the sequence
-    */
-    bool recover_utf8_sequence()
-    {
-        // the number of continuation bytes and the range of the first one;
-        // see the ranges in scan_string()
-        std::size_t count = 0;
-        char_int_type low = 0x80;
-        char_int_type high = 0xBF;
-        if (current >= 0xC2 && current <= 0xDF)
-        {
-            count = 1;
-        }
-        else if (current >= 0xE0 && current <= 0xEF)
-        {
-            count = 2;
-            low = (current == 0xE0) ? 0xA0 : 0x80;
-            high = (current == 0xED) ? 0x9F : 0xBF;
-        }
-        else if (current >= 0xF0 && current <= 0xF4)
-        {
-            count = 3;
-            low = (current == 0xF0) ? 0x90 : 0x80;
-            high = (current == 0xF4) ? 0x8F : 0xBF;
-        }
-        else
-        {
-            // an ill-formed byte
-            add_replacement_character();
-            return true;
-        }
-
-        const std::size_t start = token_buffer.size();
-        add(current);
-        for (std::size_t i = 0; i < count; ++i)
-        {
-            get();
-            if (current < low || current > high)
-            {
-                token_buffer.resize(start);
-                add_replacement_character();
-                return false;
-            }
-            add(current);
-            low = 0x80;
-            high = 0xBF;
-        }
-        return true;
-    }
-
-    /*!
-    @brief read the low surrogate that must follow the high surrogate @a high
-    @return whether the next character must be read; false if current still
-            needs to be handled
-    */
-    bool recover_low_surrogate(int high)
-    {
-        while (true)
-        {
-            if (get() != '\\')
-            {
-                add_replacement_character();
-                return false;
-            }
-            if (get() != 'u')
-            {
-                add_replacement_character();
-                // not 'u', so this does not come back here
-                return recover_escape();
-            }
-
-            const int low = get_codepoint();
-            if (low == -1)
-            {
-                add_replacement_character();
-                return false;
-            }
-            if (0xDC00 <= low && low <= 0xDFFF)
-            {
-                add_codepoint(combine_surrogates(high, low));
-                return true;
-            }
-
-            // high has no low surrogate
-            add_replacement_character();
-            if (low < 0xD800 || low > 0xDBFF)
-            {
-                add_codepoint(low);
-                return true;
-            }
-            // another high surrogate
-            high = low;
-        }
-    }
-
-    /*!
-    @brief read the escape whose backslash was read; current is the escaped character
-    @return whether the next character must be read; false if current still
-            needs to be handled
-    */
-    bool recover_escape()
-    {
-        switch (current)
-        {
-            case '\"':
-                add('\"');
-                return true;
-            case '\\':
-                add('\\');
-                return true;
-            case '/':
-                add('/');
-                return true;
-            case 'b':
-                add('\b');
-                return true;
-            case 'f':
-                add('\f');
-                return true;
-            case 'n':
-                add('\n');
-                return true;
-            case 'r':
-                add('\r');
-                return true;
-            case 't':
-                add('\t');
-                return true;
-
-            case 'u':
-            {
-                const int codepoint = get_codepoint();
-                if (codepoint == -1)
-                {
-                    add_replacement_character();
-                    return false;
-                }
-                if (0xD800 <= codepoint && codepoint <= 0xDBFF)
-                {
-                    return recover_low_surrogate(codepoint);
-                }
-                add_escaped_codepoint(codepoint);
-                return true;
-            }
-
-            // an unknown escape stands for the escaped character
-            default:
-                return false;
-        }
-    }
-
-    /*!
-    @brief read the rest of a string after scan_string() rejected it
-
-    token_buffer holds what scan_string() read before the error. See
-    recover_token() for how errors are repaired.
-
-    @param[in] cause      the kind of error scan_string() reported
-    @param[in] resume     how to continue, see resume_kind
-    @param[in] codepoint  for a high surrogate followed by an escape of another
-                          code point: that code point; -1 otherwise
-    */
-    token_type recover_string(const error_kind cause, const resume_kind resume, const int codepoint)
-    {
-        // whether the next character must be read before it can be handled
-        bool fetch = false;
-
-        if (cause == error_kind::string_invalid_escape
-                || (cause == error_kind::string_ill_formed_utf8 && remove_incomplete_utf8_sequence()))
-        {
-            add_replacement_character();
-        }
-
-        switch (resume)
-        {
-            case resume_kind::escaped_character:
-                fetch = recover_escape();
-                break;
-            case resume_kind::after_escape:
-                if (0xD800 <= codepoint && codepoint <= 0xDBFF)
-                {
-                    fetch = recover_low_surrogate(codepoint);
-                }
-                else
-                {
-                    if (codepoint != -1)
-                    {
-                        add_escaped_codepoint(codepoint);
-                    }
-                    fetch = true;
-                }
-                break;
-            case resume_kind::character:
-            default:
-                break;
-        }
-
-        while (true)
-        {
-            if (fetch)
-            {
-                get();
-            }
-            fetch = true;
-
-            switch (current)
-            {
-                case '\"':
-                // a line break or the end of the input ends a string that
-                // lacks its closing quote
-                case '\n':
-                case '\r':
-                case char_traits<char_type>::eof():
-                    return token_type::value_string;
-
-#if !JSON_STRICT_NUL_HANDLING
-                case '\0':
-                    // the end of the input, see scan()
-                    unget();
-                    return token_type::value_string;
-#endif
-
-                case '\\':
-                    get();
-                    fetch = recover_escape();
-                    break;
-
-                default:
-                    if (current < 0x80)
-                    {
-                        // including control characters
-                        add(current);
-                    }
-                    else
-                    {
-                        fetch = recover_utf8_sequence();
-                    }
-                    break;
-            }
-        }
-    }
-
-    /*!
-    @brief keep the longest valid prefix of a number that scan_number() rejected
-
-    token_buffer holds the characters scan_number() accepted before the error,
-    so the prefix ends at its last digit.
-    */
-    token_type recover_number()
-    {
-        // only size(), operator[], and resize() are used, which every string
-        // type the library supports provides
-        std::size_t length = token_buffer.size();
-        while (length != 0 && (token_buffer[length - 1] < '0' || token_buffer[length - 1] > '9'))
-        {
-            --length;
-        }
-        token_buffer.resize(length);
-
-        if (length == 0)
-        {
-            skip_to_delimiter();
-            return token_type::uninitialized;
-        }
-
-        if (decimal_point_position >= length)
-        {
-            decimal_point_position = std::string::npos;
-        }
-
-        std::size_t exponent = std::string::npos;
-        for (std::size_t i = 0; i < length; ++i)
-        {
-            if (token_buffer[i] == 'e' || token_buffer[i] == 'E')
-            {
-                exponent = i;
-                break;
-            }
-        }
-        const std::size_t mantissa_end = (exponent == std::string::npos) ? length : exponent;
-        token_type number_type = token_type::value_unsigned;
-        if (decimal_point_position != std::string::npos || exponent != std::string::npos)
-        {
-            number_type = token_type::value_float;
-        }
-        else if (token_buffer[0] == '-')
-        {
-            number_type = token_type::value_integer;
-        }
-
-        const token_type result = convert_number(number_type, mantissa_end);
-        skip_to_delimiter();
-        return result;
-    }
-
-    /// seekable or token-tracking adapter: the token string begins at current
-    void restart_token_string_impl(std::true_type /*lazy*/)
-    {
-        restart_token_string_lazy(std::integral_constant<bool, adapter_token> {});
-    }
-
-    /// seekable adapter: the token string begins at current, which was consumed
-    void restart_token_string_lazy(std::false_type /*adapter_token*/) noexcept
-    {
-        const std::size_t consumed = ia.get_consumed_count();
-        token_string_start = (consumed > 0 && current != char_traits<char_type>::eof()) ? consumed - 1 : consumed;
-    }
-
-    /// token-tracking adapter: the token begins with current, or with the next
-    /// character if current was put back or is the end of input
-    void restart_token_string_lazy(std::true_type /*adapter_token*/)
-    {
-        if (!next_unget && current != char_traits<char_type>::eof())
-        {
-            ia.mark_token_start(current);
-        }
-        else
-        {
-            ia.begin_token();
-        }
-    }
-
-    /// streaming adapter: the token string begins at current; a character
-    /// that was put back is copied again when it is read again
-    void restart_token_string_impl(std::false_type /*lazy*/)
-    {
-        token_string.clear();
-        if (!next_unget && current != char_traits<char_type>::eof())
-        {
-            token_string.push_back(char_traits<char_type>::to_char_type(current));
-        }
-    }
-
    /// input adapter
    InputAdapterType ia;

@@ -3145,19 +2523,6 @@ scan_number_done:
    /// that unget() can restore the column instead of leaving it at 0
    std::size_t chars_read_before_newline = 0;

-    /// seekable adapter: what get_position() counted last, so that the next
-    /// call only scans the input consumed since
-    struct position_cache_t
-    {
-        /// consumed characters scanned so far
-        std::size_t consumed = 0;
-        /// newlines among them
-        std::size_t lines = 0;
-        /// index after the last of these newlines
-        std::size_t line_start = 0;
-    };
-    mutable position_cache_t position_cache {};
-
    /// raw input token string for error messages; only populated for streaming
    /// adapters (seekable adapters reconstruct it lazily via token_string_start)
    std::vector<char_type> token_string {};
@@ -3178,15 +2543,6 @@ scan_number_done:
    /// a description of occurred lexer errors
    const char* error_message = "";

-    /// what kind of token scan() rejected; set together with error_message
-    error_kind error_cause = error_kind::other;
-    /// how recover_token() continues a string that scan_string() rejected;
-    /// set only on the error paths that need more than error_message
-    resume_kind string_error_resume = resume_kind::character;
-    /// the code point of the second escape when a high surrogate is followed
-    /// by an escape that is not a low surrogate; -1 otherwise
-    int string_error_codepoint = -1;
-
    // number values
    number_integer_t value_integer = 0;
    number_unsigned_t value_unsigned = 0;
@@ -152,72 +152,25 @@ class parser
    bool accept(const bool strict = true)
    {
        json_sax_acceptor<BasicJsonType> sax_acceptor;
-        return sax_parse_impl<false>(&sax_acceptor, strict);
+        return sax_parse(&sax_acceptor, strict);
    }

-    /*!
-    @brief public SAX interface
-
-    If the SAX parser's parse_error() returns true, the parser recovers from
-    the error: it repairs the input and continues (see #3989).
-
-    @param[in] sax     the SAX parser
-    @param[in] strict  whether to expect the last token to be EOF
-    @return whether the input was parsed without errors and no SAX event
-            returned false
-    */
    template<typename SAX>
    JSON_HEDLEY_NON_NULL(2)
    bool sax_parse(SAX* sax, const bool strict = true)
-    {
-        return sax_parse_impl<true>(sax, strict);
-    }
-
-  private:
-    /// what sax_parse_internal() does after an object key was expected
-    enum class next_step : std::uint8_t
-    {
-        /// stop parsing
-        stop,
-        /// parse a value that begins with last_token
-        parse_value,
-        /// evaluate the state of the innermost container, which reads
-        /// last_token again
-        evaluate_state
-    };
-
-    template<bool AllowRecovery, typename SAX>
-    JSON_HEDLEY_NON_NULL(2)
-    bool sax_parse_impl(SAX* sax, const bool strict)
    {
        (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
-        const bool result = sax_parse_internal<AllowRecovery>(sax);
+        const bool result = sax_parse_internal(sax);

        if (result)
        {
-            if (strict)
-            {
-                // strict mode: next byte must be EOF; after recovering from an
-                // error, the end of the input may already have been read
-                if (last_token != token_type::end_of_input && get_token() != token_type::end_of_input)
-                {
-                    // the value is complete, so there is nothing to recover
-                    static_cast<void>(report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::end_of_input, "value"), nullptr),
-                                                   std::integral_constant<bool, AllowRecovery> {}));
-                    return false;
-                }
-            }
-            else
-            {
-                // the caller keeps using the input: position it right after
-                // the value by leaving the character that terminated it
-                m_lexer.release_lookahead();
-            }
+            return finish_input(*sax, strict);
        }

-        return result && !error_reported;
+        return false;
    }

+  private:
    /// the text of the current float token for @a sax (see sax_ignores_number_text)
    template<typename SAX>
    const string_t& number_float_text(SAX* /*sax*/)
@@ -285,26 +238,17 @@ class parser
    template<typename DomSax>
    bool parse_dom(DomSax& sdp, const bool strict)
    {
-        sax_parse_internal<false>(&sdp);
+        sax_parse_internal(&sdp);

        static_cast<void>(finish_input(sdp, strict));

        return !sdp.is_errored();
    }

-    /*!
-    @brief parse a JSON value and pass it to a SAX parser
-
-    @tparam AllowRecovery  whether to recover from an error if the SAX parser's
-                           parse_error() returns true; false for the SAX parsers
-                           of parse() and accept(), which never do, so that no
-                           code for recovering is generated for them
-    */
-    template<bool AllowRecovery, typename SAX>
+    template<typename SAX>
    JSON_HEDLEY_NON_NULL(2)
    bool sax_parse_internal(SAX* sax)
    {
-        const std::integral_constant<bool, AllowRecovery> allow_recovery{};
        // value to avoid a goto (see comment where set to true)
        bool skip_to_state_evaluation = false;

@@ -343,18 +287,10 @@ class parser
                            break;
                        }

-                        // remember we are now inside an object
-                        states.push_back(0);
-
-                        // parse key (the steps of parse_key(), which are
-                        // repeated here and below for speed)
+                        // parse key
                        if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
                        {
-                            if (!continue_after(key_error(sax, allow_recovery, false), skip_to_state_evaluation))
-                            {
-                                return false;
-                            }
-                            continue;
+                            return syntax_error(*sax, exception_message(token_type::value_string, "object key"));
                        }
                        if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string_token())))
                        {
@@ -364,13 +300,12 @@ class parser
                        // parse separator (:)
                        if (JSON_HEDLEY_UNLIKELY(!get_token_expecting(token_type::name_separator)))
                        {
-                            if (!continue_after(key_error(sax, allow_recovery, true), skip_to_state_evaluation))
-                            {
-                                return false;
-                            }
-                            continue;
+                            return syntax_error(*sax, exception_message(token_type::name_separator, "object separator"));
                        }

+                        // remember we are now inside an object
+                        states.push_back(0);
+
                        // parse values
                        get_token();
                        continue;
@@ -406,11 +341,9 @@ class parser

                        if (JSON_HEDLEY_UNLIKELY(!std::isfinite(res)))
                        {
-                            if (!overflow_error(sax, res, allow_recovery))
-                            {
-                                return false;
-                            }
-                            break;
+                            return sax->parse_error(m_lexer.get_position(),
+                                                    m_lexer.get_token_string(),
+                                                    out_of_range::create(exception_id::number_overflow, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr));
                        }

                        if (JSON_HEDLEY_UNLIKELY(!sax->number_float(res, number_float_text(sax))))
@@ -478,63 +411,16 @@ class parser
                    case token_type::parse_error:
                    {
                        // using "uninitialized" to avoid an "expected" message
-                        if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::uninitialized, "value"), nullptr), allow_recovery))
-                        {
-                            return false;
-                        }
-
-                        // recover: keep what can be read of the token
-                        recover_token(allow_recovery);
-                        if (last_token != token_type::uninitialized)
-                        {
-                            // a string or a number
-                            continue;
-                        }
-                        if (states.empty())
-                        {
-                            // look for the value after the garbage
-                            if (!skip_to_value(allow_recovery))
-                            {
-                                return false;
-                            }
-                            continue;
-                        }
-                        // nothing could be read
-                        if (JSON_HEDLEY_UNLIKELY(!sax->null()))
-                        {
-                            return false;
-                        }
-                        break;
+                        return syntax_error(*sax, exception_message(token_type::uninitialized, "value"));
                    }
                    case token_type::end_of_input:
                    {
                        if (JSON_HEDLEY_UNLIKELY(m_lexer.get_chars_read_total() == 1))
                        {
-                            // there is nothing to recover
-                            static_cast<void>(report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(),
-                                                           empty_input_message(), nullptr), allow_recovery));
-                            return false;
+                            return syntax_error(*sax, empty_input_message());
                        }

-                        if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr), allow_recovery))
-                        {
-                            return false;
-                        }
-
-                        // recover: the input ends where a value is missing
-                        if (states.empty())
-                        {
-                            // there is no value
-                            return false;
-                        }
-                        if (!recover_missing_value(sax, states, allow_recovery))
-                        {
-                            return false;
-                        }
-                        // the state evaluation reads the token again
-                        unget_token(allow_recovery);
-                        skip_to_state_evaluation = true;
-                        continue;
+                        return syntax_error(*sax, exception_message(token_type::literal_or_value, "value"));
                    }
                    case token_type::uninitialized:
                    case token_type::end_array:
@@ -544,35 +430,7 @@ class parser
                    case token_type::literal_or_value:
                    default: // the last token was unexpected
                    {
-                        if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::literal_or_value, "value"), nullptr), allow_recovery))
-                        {
-                            return false;
-                        }
-
-                        // recover
-                        if (states.empty())
-                        {
-                            // look for the value after the garbage
-                            if (!skip_to_value(allow_recovery))
-                            {
-                                return false;
-                            }
-                            continue;
-                        }
-                        if (last_token == token_type::name_separator)
-                        {
-                            // a stray ':'; the value may follow
-                            get_token();
-                            continue;
-                        }
-                        if (!recover_missing_value(sax, states, allow_recovery))
-                        {
-                            return false;
-                        }
-                        // the state evaluation reads the token again
-                        unget_token(allow_recovery);
-                        skip_to_state_evaluation = true;
-                        continue;
+                        return syntax_error(*sax, exception_message(token_type::literal_or_value, "value"));
                    }
                }
            }
@@ -623,30 +481,7 @@ class parser
                    continue;
                }

-                if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::end_array, "array"), nullptr), allow_recovery))
-                {
-                    return false;
-                }
-
-                // recover
-                if (last_token == token_type::end_of_input)
-                {
-                    // the input ends inside the array
-                    return close_containers(sax, states, allow_recovery);
-                }
-                if (last_token == token_type::end_object)
-                {
-                    // a wrong closing bracket closes the innermost container
-                    if (JSON_HEDLEY_UNLIKELY(!sax->end_array()))
-                    {
-                        return false;
-                    }
-                    states.pop_back();
-                    skip_to_state_evaluation = true;
-                }
-                // otherwise, a missing ',' (or a stray ':', which value
-                // parsing drops): the next value begins here
-                continue;
+                return syntax_error(*sax, exception_message(token_type::end_array, "array"));
            }

            // states.back() is false -> object
@@ -663,12 +498,9 @@ class parser
                    // parse key
                    if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
                    {
-                        if (!continue_after(key_error(sax, allow_recovery, false), skip_to_state_evaluation))
-                        {
-                            return false;
-                        }
-                        continue;
+                        return syntax_error(*sax, exception_message(token_type::value_string, "object key"));
                    }
+
                    if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string_token())))
                    {
                        return false;
@@ -677,11 +509,7 @@ class parser
                    // parse separator (:)
                    if (JSON_HEDLEY_UNLIKELY(!get_token_expecting(token_type::name_separator)))
                    {
-                        if (!continue_after(key_error(sax, allow_recovery, true), skip_to_state_evaluation))
-                        {
-                            return false;
-                        }
-                        continue;
+                        return syntax_error(*sax, exception_message(token_type::name_separator, "object separator"));
                    }

                    // parse values
@@ -709,546 +537,10 @@ class parser
                continue;
            }

-            if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::end_object, "object"), nullptr), allow_recovery))
-            {
-                return false;
-            }
-
-            // recover
-            if (last_token == token_type::end_of_input)
-            {
-                // the input ends inside the object
-                return close_containers(sax, states, allow_recovery);
-            }
-            if (last_token == token_type::end_array)
-            {
-                // a wrong closing bracket closes the innermost container
-                if (JSON_HEDLEY_UNLIKELY(!sax->end_object()))
-                {
-                    return false;
-                }
-                states.pop_back();
-                skip_to_state_evaluation = true;
-                continue;
-            }
-            if (!continue_after(recover_member(sax, allow_recovery), skip_to_state_evaluation))
-            {
-                return false;
-            }
+            return syntax_error(*sax, exception_message(token_type::end_object, "object"));
        }
    }

-    /*!
-    @brief continue sax_parse_internal() after a recovery
-    @return whether to continue parsing
-    */
-    bool continue_after(const next_step step, bool& skip_to_state_evaluation)
-    {
-        if (step == next_step::evaluate_state)
-        {
-            // the state evaluation reads the token again
-            m_lexer.unget_token();
-            skip_to_state_evaluation = true;
-        }
-        return step != next_step::stop;
-    }
-
-    /// the parser for parse() and accept() never recovers: stop parsing
-    JSON_INTERNAL_ALWAYS_INLINE
-    static std::false_type continue_after(std::false_type /*step*/, bool& /*skip_to_state_evaluation*/) noexcept
-    {
-        return {};
-    }
-
-    /*!
-    @brief parse an object key and the name separator (:) after it
-
-    last_token is the token where the key is expected. sax_parse_internal()
-    repeats these steps rather than calling this function, which is used
-    when recovering from an error.
-
-    @return next_step::parse_value if the value follows, with last_token its
-            first token; next_step::evaluate_state if the object's state is
-            to be evaluated after recovering from an error; next_step::stop
-            to stop parsing
-    */
-    template<typename SAX>
-    next_step parse_key(SAX* sax)
-    {
-        const std::true_type allow_recovery{};
-
-        if (JSON_HEDLEY_UNLIKELY(last_token != token_type::value_string))
-        {
-            return key_error(sax, allow_recovery, false);
-        }
-
-        if (JSON_HEDLEY_UNLIKELY(!sax->key(m_lexer.get_string_token())))
-        {
-            return next_step::stop;
-        }
-
-        // parse separator (:)
-        if (JSON_HEDLEY_UNLIKELY(get_token() != token_type::name_separator))
-        {
-            return key_error(sax, allow_recovery, true);
-        }
-
-        // the value begins with the next token
-        get_token();
-        return next_step::parse_value;
-    }
-
-    /*!
-    @brief report a number that is too large for number_float_t, and recover
-           from the error by passing the value on; the SAX parser gets the
-           number's text as well
-
-    This is a separate function, as reading other numbers is measurably
-    slower if the error is handled where they are read.
-
-    @param[in] sax    the SAX parser
-    @param[in] value  the value that is not finite
-    @return whether to continue parsing
-    */
-    template<typename SAX>
-    bool overflow_error(SAX* sax, const number_float_t value, std::true_type allow_recovery)
-    {
-        if (!report_error(sax, out_of_range::create(exception_id::number_overflow, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr), allow_recovery))
-        {
-            return false;
-        }
-        return sax->number_float(value, number_float_text(sax));
-    }
-
-    /// @copydoc overflow_error
-    template<typename SAX>
-    JSON_INTERNAL_ALWAYS_INLINE
-    std::false_type overflow_error(SAX* sax, const number_float_t /*value*/, std::false_type allow_recovery)
-    {
-        return report_error(sax, out_of_range::create(exception_id::number_overflow, concat("number overflow parsing '", m_lexer.get_token_string(), '\''), nullptr), allow_recovery);
-    }
-
-    /*!
-    @brief report a missing key, or a missing name separator (:) after the
-           key; the parser for parse() and accept() never recovers
-
-    @param[in] key_read  whether the key was read, so that the name separator
-                         is missing
-    @return std::false_type, see report_error()
-    */
-    template<typename SAX>
-    JSON_INTERNAL_ALWAYS_INLINE
-    std::false_type key_error(SAX* sax, std::false_type allow_recovery, const bool key_read)
-    {
-        return report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), key_read
-                            ? exception_message(token_type::name_separator, "object separator")
-                            : exception_message(token_type::value_string, "object key"), nullptr), allow_recovery);
-    }
-
-    /*!
-    @brief report a missing key, or a missing name separator (:) after the
-           key, and recover from it
-
-    @param[in] key_read  whether the key was read, so that the name separator
-                         is missing
-    */
-    template<typename SAX>
-    next_step key_error(SAX* sax, std::true_type allow_recovery, const bool key_read)
-    {
-        if (!key_read)
-        {
-            if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::value_string, "object key"), nullptr), allow_recovery))
-            {
-                return next_step::stop;
-            }
-            return recover_key(sax);
-        }
-
-        if (!report_error(sax, parse_error::create(exception_id::syntax_error, m_lexer.get_position(), exception_message(token_type::name_separator, "object separator"), nullptr), allow_recovery))
-        {
-            return next_step::stop;
-        }
-        return recover_name_separator(sax);
-    }
-
-    /////////////////////
-    // error recovery
-    /////////////////////
-
-    /*
-    The functions below repair an error after the SAX parser's parse_error()
-    returned true (see #3989). Each mistake is repaired by the smallest local
-    edit: a missing ',' or ':' is inserted, a stray token is removed, what can
-    be read of an invalid string or number is kept (see
-    lexer::recover_token()), a missing value becomes null, a wrong closing
-    bracket closes the innermost container, and the end of the input closes
-    all of them. The events stay balanced, and every key() is followed by
-    exactly one value.
-
-    A repair hands a token to the state evaluation, by returning it to the
-    lexer (lexer::unget_token()) so that the state evaluation reads it again,
-    only if it is ',', ']', '}', or the end of the input. The state evaluation
-    hands a token to value or key parsing only if it is none of them, so a
-    token is never handed back and forth. Every other step reads a token or
-    closes a container, so parsing always ends.
-    */
-
-    /*!
-    @brief report an error to the SAX parser; the parser for parse() and
-           accept() never recovers
-
-    @return std::false_type rather than false: its value is known where the
-            function is called even if the call is not inlined, so the code
-            for recovering is not generated
-    */
-    template<typename SAX, typename Exception>
-    JSON_INTERNAL_ALWAYS_INLINE
-    std::false_type report_error(SAX* sax, const Exception& ex, std::false_type /*allow_recovery*/)
-    {
-        static_cast<void>(sax); // MSVC 2015 does not count calling a static parse_error() as using it
-        error_reported = true;
-        static_cast<void>(sax->parse_error(m_lexer.get_position(), m_lexer.get_token_string(), ex));
-        return {};
-    }
-
-    /*!
-    @brief report an error to the SAX parser
-    @return whether to recover from the error
-    */
-    template<typename SAX, typename Exception>
-    bool report_error(SAX* sax, const Exception& ex, std::true_type /*allow_recovery*/)
-    {
-        static_cast<void>(sax); // MSVC 2015 does not count calling a static parse_error() as using it
-        const std::size_t position = m_lexer.get_position().chars_read_total;
-        if (error_reported && position == last_error_position && last_token == last_error_token)
-        {
-            // a repair handed on the token of the error it repaired; the
-            // token was reported already, and the SAX parser asked to recover
-            return true;
-        }
-
-        error_reported = true;
-        last_error_position = position;
-        last_error_token = last_token;
-
-        if (!sax->parse_error(m_lexer.get_position(), m_lexer.get_token_string(), ex))
-        {
-            return false;
-        }
-
-        // the token string of the next error begins here
-        m_lexer.restart_token_string();
-        return true;
-    }
-
-    /*!
-    @brief keep what can be read of the token that the lexer rejected
-
-    The error was reported for the rejected token, so it is not reported again
-    for the token it is repaired to (see lexer::recover_token()).
-    */
-    token_type recover_token()
-    {
-        last_token = m_lexer.recover_token();
-        last_error_position = m_lexer.get_position().chars_read_total;
-        last_error_token = last_token;
-        return last_token;
-    }
-
-    // The functions below are called from sax_parse_internal() after an error
-    // was reported. The parser for parse() and accept() stopped there, so for
-    // it they are stubs: the code for recovering is then not even referenced,
-    // and unoptimized builds do not emit it either.
-
-    /// @copydoc recover_token()
-    JSON_INTERNAL_ALWAYS_INLINE
-    token_type recover_token(std::true_type /*allow_recovery*/)
-    {
-        return recover_token();
-    }
-
-    /// @copydoc recover_token()
-    JSON_INTERNAL_ALWAYS_INLINE
-    static std::false_type recover_token(std::false_type /*allow_recovery*/) noexcept
-    {
-        return {};
-    }
-
-    /// return the token that was read last to the lexer (see lexer::unget_token())
-    JSON_INTERNAL_ALWAYS_INLINE
-    void unget_token(std::true_type /*allow_recovery*/)
-    {
-        m_lexer.unget_token();
-    }
-
-    /// @copydoc unget_token(std::true_type)
-    JSON_INTERNAL_ALWAYS_INLINE
-    static void unget_token(std::false_type /*allow_recovery*/) noexcept {}
-
-    /// @copydoc skip_to_value
-    JSON_INTERNAL_ALWAYS_INLINE
-    static std::false_type skip_to_value(std::false_type /*allow_recovery*/) noexcept
-    {
-        return {};
-    }
-
-    /// @copydoc recover_missing_value
-    template<typename SAX>
-    JSON_INTERNAL_ALWAYS_INLINE
-    static std::false_type recover_missing_value(SAX* /*sax*/, const std::vector<std::uint8_t>& /*states*/, std::false_type /*allow_recovery*/) noexcept
-    {
-        return {};
-    }
-
-    /// pass the end events of all open containers
-    template<typename SAX>
-    bool close_containers(SAX* sax, std::vector<std::uint8_t>& states, std::true_type /*allow_recovery*/)
-    {
-        while (!states.empty())
-        {
-            const bool is_array = states.back() != 0;
-            states.pop_back();
-            if (JSON_HEDLEY_UNLIKELY(is_array ? !sax->end_array() : !sax->end_object()))
-            {
-                return false;
-            }
-        }
-        return true;
-    }
-
-    /// @copydoc close_containers
-    template<typename SAX>
-    JSON_INTERNAL_ALWAYS_INLINE
-    static std::false_type close_containers(SAX* /*sax*/, std::vector<std::uint8_t>& /*states*/, std::false_type /*allow_recovery*/) noexcept
-    {
-        return {};
-    }
-
-    /*!
-    @brief read tokens until one begins a value, skipping everything before
-           the top-level value
-    @return whether a value begins with last_token
-    */
-    bool skip_to_value(std::true_type /*allow_recovery*/)
-    {
-        while (true)
-        {
-            switch (get_token())
-            {
-                case token_type::begin_array:
-                case token_type::begin_object:
-                case token_type::literal_false:
-                case token_type::literal_null:
-                case token_type::literal_true:
-                case token_type::value_float:
-                case token_type::value_integer:
-                case token_type::value_string:
-                case token_type::value_unsigned:
-                    return true;
-
-                case token_type::end_of_input:
-                    return false;
-
-                case token_type::parse_error:
-                    recover_token();
-                    if (last_token != token_type::uninitialized)
-                    {
-                        return true;
-                    }
-                    break;
-
-                case token_type::uninitialized:
-                case token_type::end_array:
-                case token_type::end_object:
-                case token_type::name_separator:
-                case token_type::value_separator:
-                case token_type::literal_or_value:
-                default:
-                    break;
-            }
-        }
-    }
-
-    /*!
-    @brief skip the rest of an object member that cannot be read
-
-    Reads tokens, beginning with last_token, until a ',', '}', or ']' that is
-    not inside a container that begins in the skipped tokens, or the end of
-    the input.
-    */
-    void skip_member()
-    {
-        std::size_t depth = 0;
-        while (true)
-        {
-            switch (last_token)
-            {
-                case token_type::begin_array:
-                case token_type::begin_object:
-                    ++depth;
-                    break;
-
-                case token_type::end_array:
-                case token_type::end_object:
-                    if (depth == 0)
-                    {
-                        return;
-                    }
-                    --depth;
-                    break;
-
-                case token_type::value_separator:
-                    if (depth == 0)
-                    {
-                        return;
-                    }
-                    break;
-
-                case token_type::end_of_input:
-                    return;
-
-                case token_type::parse_error:
-                    recover_token();
-                    break;
-
-                case token_type::uninitialized:
-                case token_type::literal_true:
-                case token_type::literal_false:
-                case token_type::literal_null:
-                case token_type::value_string:
-                case token_type::value_unsigned:
-                case token_type::value_integer:
-                case token_type::value_float:
-                case token_type::name_separator:
-                case token_type::literal_or_value:
-                default:
-                    break;
-            }
-            get_token();
-        }
-    }
-
-    /*!
-    @brief pass a value where it is missing
-
-    last_token is ',', ']', '}', or the end of the input, where a value was
-    expected. In an object, the key gets null; in an array, a ',' where a
-    value is missing stands for null (as in JavaScript), while an array that
-    ends there just ends.
-    */
-    template<typename SAX>
-    bool recover_missing_value(SAX* sax, const std::vector<std::uint8_t>& states, std::true_type /*allow_recovery*/)
-    {
-        JSON_ASSERT(!states.empty());
-        if (states.back() == 0 || last_token == token_type::value_separator)
-        {
-            return sax->null();
-        }
-        return true;
-    }
-
-    /// recover from a missing key; last_token is where it was expected
-    template<typename SAX>
-    next_step recover_key(SAX* sax)
-    {
-        switch (last_token)
-        {
-            case token_type::value_separator:
-            case token_type::end_object:
-            case token_type::end_array:
-            case token_type::end_of_input:
-                // no member: the object's state handles the token
-                return next_step::evaluate_state;
-
-            case token_type::parse_error:
-                recover_token();
-                if (last_token == token_type::value_string)
-                {
-                    // a key that could be repaired
-                    return parse_key(sax);
-                }
-                skip_member();
-                return next_step::evaluate_state;
-
-            case token_type::uninitialized:
-            case token_type::literal_true:
-            case token_type::literal_false:
-            case token_type::literal_null:
-            case token_type::value_string:
-            case token_type::value_unsigned:
-            case token_type::value_integer:
-            case token_type::value_float:
-            case token_type::begin_array:
-            case token_type::begin_object:
-            case token_type::name_separator:
-            case token_type::literal_or_value:
-            default:
-                // a member without a key
-                skip_member();
-                return next_step::evaluate_state;
-        }
-    }
-
-    /// recover from a missing name separator (:) after the key; last_token
-    /// is where it was expected
-    template<typename SAX>
-    next_step recover_name_separator(SAX* sax)
-    {
-        switch (last_token)
-        {
-            case token_type::value_separator:
-            case token_type::end_object:
-            case token_type::end_array:
-            case token_type::end_of_input:
-                // the value is missing as well
-                return sax->null() ? next_step::evaluate_state : next_step::stop;
-
-            case token_type::uninitialized:
-            case token_type::literal_true:
-            case token_type::literal_false:
-            case token_type::literal_null:
-            case token_type::value_string:
-            case token_type::value_unsigned:
-            case token_type::value_integer:
-            case token_type::value_float:
-            case token_type::begin_array:
-            case token_type::begin_object:
-            case token_type::name_separator:
-            case token_type::parse_error:
-            case token_type::literal_or_value:
-            default:
-                // a missing ':'; the value begins here
-                return next_step::parse_value;
-        }
-    }
-
-    /// recover from a token after an object member that is neither ',' nor
-    /// '}' (nor ']' or the end of the input, which the caller handles)
-    template<typename SAX>
-    next_step recover_member(SAX* sax, std::true_type /*allow_recovery*/)
-    {
-        if (last_token == token_type::parse_error)
-        {
-            recover_token();
-        }
-        if (last_token == token_type::value_string)
-        {
-            // a missing ','; the next key begins here
-            return parse_key(sax);
-        }
-        skip_member();
-        return next_step::evaluate_state;
-    }
-
-    /// the parser for parse() and accept() never recovers (and does not come
-    /// here, as report_error() returned false)
-    template<typename SAX>
-    JSON_INTERNAL_ALWAYS_INLINE
-    std::false_type recover_member(SAX* /*sax*/, std::false_type /*allow_recovery*/) const noexcept
-    {
-        return {};
-    }
-
    /// get next token from lexer
    token_type get_token()
    {
@@ -1281,14 +573,7 @@ class parser

    std::string exception_message(const token_type expected, const std::string& context)
    {
-        std::string error_msg = "syntax error ";
-
-        if (!context.empty())
-        {
-            error_msg += concat("while parsing ", context, ' ');
-        }
-
-        error_msg += "- ";
+        std::string error_msg = concat("syntax error while parsing ", context, " - ");

        if (last_token == token_type::parse_error)
        {
@@ -1306,7 +591,7 @@ class parser
        }

        return error_msg;
-    }
+    } // LCOV_EXCL_LINE (exception cleanup only)

  private:
    /// callback function
@@ -1319,12 +604,6 @@ class parser
    const bool allow_exceptions = true;
    /// whether trailing commas in objects and arrays should be ignored (true) or signaled as errors (false)
    const bool ignore_trailing_commas = false;
-    /// whether an error was reported to the SAX parser
-    bool error_reported = false;
-    /// the position of the last reported error
-    std::size_t last_error_position = 0;
-    /// the token of the last reported error
-    token_type last_error_token = token_type::uninitialized;
 };

 }  // namespace detail
@@ -108,6 +108,9 @@ class iter_impl // NOLINT(cppcoreguidelines-special-member-functions,hicpp-speci
    {
        JSON_ASSERT(m_object != nullptr);

+        // m_it is already value-initialized, so this is not needed for
+        // correctness; it is kept because GCC generates faster loops with it
+        // (iterating a parsed document is 0.5-2.7 % slower without it, #6005)
        if (m_object->is_object())
        {
            m_it.object_iterator = typename object_t::iterator();
@@ -304,7 +304,7 @@ class json_pointer
        result.reference_tokens.insert(result.reference_tokens.end(), lhs.reference_tokens.begin(), lhs.reference_tokens.end());
        result.reference_tokens.insert(result.reference_tokens.end(), rhs.reference_tokens.begin(), rhs.reference_tokens.end());
        return result;
-    }
+    } // LCOV_EXCL_LINE (exception cleanup only)

    /// @brief create a new JSON pointer by appending the unescaped token at the end of the JSON pointer
    /// @sa https://json.nlohmann.me/api/json_pointer/operator_slash/
@@ -315,7 +315,7 @@ class json_pointer
        result.reference_tokens.insert(result.reference_tokens.end(), lhs.reference_tokens.begin(), lhs.reference_tokens.end());
        result.reference_tokens.push_back(std::move(token));
        return result;
-    }
+    } // LCOV_EXCL_LINE (exception cleanup only)

    /// @brief create a new JSON pointer by appending the array-index-token at the end of the JSON pointer
    /// @sa https://json.nlohmann.me/api/json_pointer/operator_slash/
@@ -2180,7 +2180,7 @@ class json_pointer
                    {
                        // create an entry in the array
                        current = &current->operator[](array_index<BasicJsonType>(token));
-                        break;
+                        break; // LCOV_EXCL_LINE (needs an array index with 10 or more digits: more than 1e9 elements)
                    }

                    /*
@@ -2217,7 +2217,7 @@ class json_pointer
        json_pointer<string_t> result;
        result.reference_tokens = reference_tokens;
        return result;
-    }
+    } // LCOV_EXCL_LINE (exception cleanup only)

    json_pointer<string_t> convert()&&
    {
@@ -215,17 +215,6 @@
    #define JSON_NO_UNIQUE_ADDRESS
 #endif

-// Inlines small functions even in unoptimized builds, so that they are not
-// emitted. The parsers for parse(), accept(), and from_*() use it for the
-// functions that stand in for the code recovering from errors (see #3989).
-// MSVC is left to decide, as it warns (C4714) where it does not inline a
-// __forceinline function.
-#if defined(_MSC_VER) && !defined(__clang__)
-    #define JSON_INTERNAL_ALWAYS_INLINE
-#else
-    #define JSON_INTERNAL_ALWAYS_INLINE JSON_HEDLEY_ALWAYS_INLINE
-#endif
-
 // Clang targeting MinGW does not survive the thread_local storage the copy
 // constructor uses to bound its descent: every test that copies a value
 // segfaults with clang 11.0.1 and clang 18.1.8, while the same tests pass with
@@ -19,7 +19,6 @@
 #undef NLOHMANN_CAN_CALL_STD_FUNC_IMPL
 #undef JSON_INLINE_VARIABLE
 #undef JSON_NO_UNIQUE_ADDRESS
-#undef JSON_INTERNAL_ALWAYS_INLINE
 #undef JSON_DISABLE_ENUM_SERIALIZATION
 #undef JSON_DISABLE_TUPLE_REFERENCE_CONVERSION
 #undef JSON_UNLOCKED_FILE_IO
@@ -833,7 +833,7 @@ class binary_writer
        while (n != 0);
        std::reverse(result.begin(), result.end());
        return result;
-    }
+    } // LCOV_EXCL_LINE (exception cleanup only)

    /*!
    @brief the decimal digits of the integer @a n, with a leading '-' if it
@@ -860,7 +860,7 @@ class binary_writer
        }
        std::reverse(result.begin(), result.end());
        return result;
-    }
+    } // LCOV_EXCL_LINE (exception cleanup only)

    /*!
    @brief throws because the integer @a j is too large for @a format
@@ -1792,7 +1792,7 @@ class binary_writer
        std::memcpy(out, &n, sizeof(NumberType));
        if (!is_little_endian)
        {
-            std::reverse(out, out + sizeof(NumberType));
+            std::reverse(out, out + sizeof(NumberType)); // LCOV_EXCL_LINE (big-endian hosts only)
        }
    }

@@ -1921,7 +1921,7 @@ class binary_writer
            const string_t& value = *j.m_data.m_value.string;
            if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::int32_t>(value.size() + 1ul)))
            {
-                return false;
+                return false; // LCOV_EXCL_LINE (a string of 2 GiB or more)
            }
            out[0] = to_char_type(0x02);
            store_little_endian<std::int32_t>(p, static_cast<std::int32_t>(value.size() + 1ul));
@@ -2378,7 +2378,7 @@ class binary_writer
        const std::size_t size = oa.written() - pos;
        if (JSON_HEDLEY_UNLIKELY(!value_in_range_of<std::int32_t>(size)))
        {
-            return false;
+            return false; // LCOV_EXCL_LINE (a document of 2 GiB or more)
        }
        const auto le_size = static_cast<std::uint32_t>(size);
        oa.overwrite(pos, is_little_endian ? le_size : byteswap(le_size));
@@ -2422,7 +2422,6 @@ class binary_writer
            nothing large has been written then, and the caller writes the
            document in two passes, which reports that error
    */
-    template<typename SinkType = OutputSinkType, typename std::enable_if<is_detected<sink_written_t, SinkType>::value, int>::type = 0>
    bool write_bson_document_single_pass(const BasicJsonType& document)
    {
        const std::size_t start = oa.written();
@@ -2507,7 +2506,7 @@ class binary_writer
                    {
                        if (JSON_HEDLEY_UNLIKELY(!close_bson_container(nested_size_pos)))
                        {
-                            return false;
+                            return false; // LCOV_EXCL_LINE (a document of 2 GiB or more)
                        }
                        continue;
                    }
@@ -2522,7 +2521,7 @@ class binary_writer

            if (JSON_HEDLEY_UNLIKELY(!close_bson_container(current.size_slot)))
            {
-                return false;
+                return false; // LCOV_EXCL_LINE (a document of 2 GiB or more)
            }
            if (parents.empty())
            {
@@ -2779,10 +2778,10 @@ class binary_writer

    Selected through masks rather than branches, as the type and the sign of
    the values in an array of mixed signs alternate unpredictably (non-negative
-    integers are number_unsigned after parsing). Up to 64 bits, the sign is bit
-    63 of the result (a narrower integer is sign-extended); computing it with
-    masks keeps GCC from branching on the type. A wider integer has to be
-    compared.
+    integers are number_unsigned after parsing). The sign is bit 63 of the
+    result (a narrower integer is sign-extended); computing it with masks keeps
+    GCC from branching on the type. Only called if @ref integers_fit_64_bits();
+    a wider number type is written with range checks on the whole value.
    */
    static std::uint64_t integer_bits(const BasicJsonType& j, std::uint64_t& sign_mask) noexcept
    {
@@ -2790,9 +2789,7 @@ class binary_writer
        const std::uint64_t raw = is_signed
                                  ? static_cast<std::uint64_t>(j.m_data.m_value.number_integer)
                                  : static_cast<std::uint64_t>(j.m_data.m_value.number_unsigned);
-        sign_mask = sizeof(typename BasicJsonType::number_integer_t) <= sizeof(std::uint64_t)
-                    ? (std::uint64_t{0} - static_cast<std::uint64_t>(is_signed)) & (std::uint64_t{0} - (raw >> 63u))
-                    : std::uint64_t{0} - static_cast<std::uint64_t>(is_signed && j.m_data.m_value.number_integer < 0);
+        sign_mask = (std::uint64_t{0} - static_cast<std::uint64_t>(is_signed)) & (std::uint64_t{0} - (raw >> 63u));
        return raw;
    }

@@ -3129,22 +3126,19 @@ class binary_writer
                // negative fixnum
                write_number(static_cast<std::int8_t>(j.m_data.m_value.number_integer));
            }
-            else if (j.m_data.m_value.number_integer >= (std::numeric_limits<std::int8_t>::min)() &&
-                     j.m_data.m_value.number_integer <= (std::numeric_limits<std::int8_t>::max)())
+            else if (j.m_data.m_value.number_integer >= (std::numeric_limits<std::int8_t>::min)())
            {
                // int 8
                oa.write_character(to_char_type(0xD0));
                write_number(static_cast<std::int8_t>(j.m_data.m_value.number_integer));
            }
-            else if (j.m_data.m_value.number_integer >= (std::numeric_limits<std::int16_t>::min)() &&
-                     j.m_data.m_value.number_integer <= (std::numeric_limits<std::int16_t>::max)())
+            else if (j.m_data.m_value.number_integer >= (std::numeric_limits<std::int16_t>::min)())
            {
                // int 16
                oa.write_character(to_char_type(0xD1));
                write_number(static_cast<std::int16_t>(j.m_data.m_value.number_integer));
            }
-            else if (j.m_data.m_value.number_integer >= (std::numeric_limits<std::int32_t>::min)() &&
-                     j.m_data.m_value.number_integer <= (std::numeric_limits<std::int32_t>::max)())
+            else if (j.m_data.m_value.number_integer >= (std::numeric_limits<std::int32_t>::min)())
            {
                // int 32
                oa.write_character(to_char_type(0xD2));
@@ -4060,7 +4054,7 @@ class binary_writer
    Containers, strings, high-precision numbers, booleans and null cannot be
    declared as the single type of an optimized container in BJData; such a
    container is written unoptimized. The reader rejects them with the same
-    list (binary_reader::is_bjd_excluded_optimized_type()).
+    list (binary_reader::is_valid_optimized_type()).
    */
    static constexpr bool is_bjdata_excluded_type_marker(const CharType marker) noexcept
    {
@@ -4159,57 +4153,34 @@ class binary_writer
    }

    /*!
-    @brief validate (dry_run) or write one BJData ND-array element of integer dtype @a T
-    @return whether @a el's value is in range of @a T; always true when @a dry_run is false
-    */
-    template<typename T>
-    bool write_bjdata_ndarray_element(const BasicJsonType& el, const bool dry_run)
-    {
-        if (dry_run)
-        {
-            return bjdata_ndarray_value_in_range<T>(el);
-        }
-        using storage_type = typename std::conditional<std::is_unsigned<T>::value, std::uint64_t, std::int64_t>::type;
-        write_number(static_cast<T>(el.template get<storage_type>()), true);
-        return true;
-    }
-
-    /*!
-    @brief validate (dry_run) or write one BJData ND-array element of dtype 'd' (single precision)
+    @brief whether the BJData ND-array element @a el can be written with dtype 'd' (single precision)
    @return whether @a el's value survives narrowing to float and back without any change
-            (so the ND-array round-trips exactly), or is infinite or NaN; always true when
-            @a dry_run is false
+            (so the ND-array round-trips exactly), or is infinite or NaN
    */
-    bool write_bjdata_ndarray_float_element(const BasicJsonType& el, const bool dry_run)
+    static bool bjdata_ndarray_float_in_range(const BasicJsonType& el) noexcept
    {
        const auto dval = static_cast<double>(el.m_data.m_value.number_float);
-        if (dry_run)
-        {
 #ifdef __GNUC__
-            JSON_HEDLEY_DIAGNOSTIC_PUSH
-            JSON_HEDLEY_PRAGMA(GCC diagnostic ignored "-Wfloat-equal")
+        JSON_HEDLEY_DIAGNOSTIC_PUSH
+        JSON_HEDLEY_PRAGMA(GCC diagnostic ignored "-Wfloat-equal")
 #endif
-            // a value that would be rounded (rather than exactly represented) by the
-            // narrowing to float is treated like an out-of-range integer element; this
-            // is the same criterion write_compact_float() uses for CBOR/MessagePack
-            const bool in_range = std::isnan(dval) ||
-                                  (dval >= static_cast<double>(std::numeric_limits<float>::lowest()) &&
-                                   dval <= static_cast<double>((std::numeric_limits<float>::max)()) &&
-                                   static_cast<double>(static_cast<float>(dval)) == dval) ||
-                                  std::isinf(dval);
+        // a value that would be rounded (rather than exactly represented) by the
+        // narrowing to float is treated like an out-of-range integer element; this
+        // is the same criterion write_compact_float() uses for CBOR/MessagePack
+        return std::isnan(dval) ||
+               (dval >= static_cast<double>(std::numeric_limits<float>::lowest()) &&
+                dval <= static_cast<double>((std::numeric_limits<float>::max)()) &&
+                static_cast<double>(static_cast<float>(dval)) == dval) ||
+               std::isinf(dval);
 #ifdef __GNUC__
-            JSON_HEDLEY_DIAGNOSTIC_POP
+        JSON_HEDLEY_DIAGNOSTIC_POP
 #endif
-            return in_range;
-        }
-        write_number(static_cast<float>(dval), true);
-        return true;
    }

    /*!
    @brief write the elements of an ND-array as the number kind @a dtype names
           (see @ref write_bjdata_ndarray), after they have been found to be
-           in range by a dry run of @ref write_bjdata_ndarray_elements
+           in range by @ref bjdata_ndarray_elements_in_range

    The elements are encoded in blocks into space reserved from the sink.
    */
@@ -4291,20 +4262,13 @@ class binary_writer
    }

    /*!
-    @brief validate or write every element of a BJData ND-array's `_ArrayData_`
+    @brief whether every element of a BJData ND-array's `_ArrayData_` is in range for its dtype
    @param[in] array_data  the `_ArrayData_` array
    @param[in] dtype       the ND-array dtype marker, as returned by bjdata_ndarray_type_marker()
-    @param[in] dry_run     true to only range-check each element, false to write it
-    @return whether every element is in range for @a dtype (always true when @a dry_run is false)
+    @return whether every element is in range for @a dtype
    */
-    bool write_bjdata_ndarray_elements(const BasicJsonType& array_data, const CharType dtype, const bool dry_run)
+    static bool bjdata_ndarray_elements_in_range(const BasicJsonType& array_data, const CharType dtype)
    {
-        if (!dry_run)
-        {
-            write_bjdata_ndarray_values(array_data, dtype);
-            return true;
-        }
-
        for (const auto& el : array_data)
        {
            bool ok = true;
@@ -4312,43 +4276,39 @@ class binary_writer
            {
                case 'U':
                case 'B':
-                    ok = write_bjdata_ndarray_element<std::uint8_t>(el, dry_run);
+                    ok = bjdata_ndarray_value_in_range<std::uint8_t>(el);
                    break;
                case 'C':
                    // BJData limits a char to 0..127 (the intersection of the int8 and uint8 ranges)
                    ok = bjdata_ndarray_value_in_range<std::int8_t>(el) && bjdata_ndarray_value_in_range<std::uint8_t>(el);
                    break;
                case 'i':
-                    ok = write_bjdata_ndarray_element<std::int8_t>(el, dry_run);
+                    ok = bjdata_ndarray_value_in_range<std::int8_t>(el);
                    break;
                case 'u':
-                    ok = write_bjdata_ndarray_element<std::uint16_t>(el, dry_run);
+                    ok = bjdata_ndarray_value_in_range<std::uint16_t>(el);
                    break;
                case 'I':
-                    ok = write_bjdata_ndarray_element<std::int16_t>(el, dry_run);
+                    ok = bjdata_ndarray_value_in_range<std::int16_t>(el);
                    break;
                case 'm':
-                    ok = write_bjdata_ndarray_element<std::uint32_t>(el, dry_run);
+                    ok = bjdata_ndarray_value_in_range<std::uint32_t>(el);
                    break;
                case 'l':
-                    ok = write_bjdata_ndarray_element<std::int32_t>(el, dry_run);
+                    ok = bjdata_ndarray_value_in_range<std::int32_t>(el);
                    break;
                case 'M':
-                    ok = write_bjdata_ndarray_element<std::uint64_t>(el, dry_run);
+                    ok = bjdata_ndarray_value_in_range<std::uint64_t>(el);
                    break;
                case 'L':
-                    ok = write_bjdata_ndarray_element<std::int64_t>(el, dry_run);
+                    ok = bjdata_ndarray_value_in_range<std::int64_t>(el);
                    break;
                case 'd':
-                    ok = write_bjdata_ndarray_float_element(el, dry_run);
+                    ok = bjdata_ndarray_float_in_range(el);
                    break;
                case 'D':
                default:
                    // 'D' (double) already spans the full range of number_float_t
-                    if (!dry_run)
-                    {
-                        write_number(el.template get<double>(), true);
-                    }
                    break;
            }
            if (!ok)
@@ -4435,7 +4395,7 @@ class binary_writer
            const auto dim = el.template get<std::uint64_t>();
            if (!value_in_range_of<std::size_t>(dim))
            {
-                return true;
+                return true; // LCOV_EXCL_LINE (size_t is narrower than 64 bits)
            }
            const auto dim_size = static_cast<std::size_t>(dim);

@@ -4485,7 +4445,7 @@ class binary_writer
        // wrap (integers) or overflow to infinity (the "single" precision
        // float) instead of being reported, so such an object falls back to
        // a plain object encoding as well
-        if (!write_bjdata_ndarray_elements(array_data, dtype, true))
+        if (!bjdata_ndarray_elements_in_range(array_data, dtype))
        {
            return true;
        }
@@ -4497,7 +4457,7 @@ class binary_writer

        write_ubjson(array_size, use_count, use_type, true,  true, bjdata_version);

-        write_bjdata_ndarray_elements(array_data, dtype, false);
+        write_bjdata_ndarray_values(array_data, dtype);
        return false;
    }

@@ -4823,8 +4783,8 @@ class binary_writer
    run are encoded into space reserved from the sink, as in
    @ref write_array_elements; an integer that BON8 cannot write (an unsigned
    one above the int64 range, or one of a number type wider than 64 bits) throws
-    from write_bon8_value, like any other value that is not a number. Kept out
-    of line, like @ref write_cbor_array.
+    out_of_range.407, as write_bon8_value does. Kept out of line, like
+    @ref write_cbor_array.
    */
    template<typename ArrayType>
    JSON_HEDLEY_NEVER_INLINE
@@ -4874,10 +4834,10 @@ class binary_writer
                string_open = false;
            }

-            if (unencodable)
+            if (JSON_HEDLEY_UNLIKELY(unencodable))
            {
-                write_bon8_value(*it, string_open, depth + 1);
-                ++it;
+                // an integer beyond the int64 range, as write_bon8_value would report it
+                throw_integer_out_of_range(*it, input_format_t::bon8, "int64");
            }
        }
    }
@@ -4912,14 +4872,13 @@ class binary_writer
                    break;

                case value_t::number_integer:
-                    if (JSON_HEDLEY_LIKELY(integer_fits<std::int64_t>(value.m_data.m_value.number_integer)))
+                    if (JSON_HEDLEY_UNLIKELY(!integer_fits<std::int64_t>(value.m_data.m_value.number_integer)))
                    {
-                        write_bon8_integer(static_cast<std::int64_t>(value.m_data.m_value.number_integer));
-                        string_open = false;
-                        break;
+                        // beyond 64 bits (number types wider than that)
+                        throw_integer_out_of_range(value, input_format_t::bon8, "int64");
                    }
-                    // beyond 64 bits (number types wider than that): throws
-                    write_bon8_value(value, string_open, depth + 1);
+                    write_bon8_integer(static_cast<std::int64_t>(value.m_data.m_value.number_integer));
+                    string_open = false;
                    break;

                case value_t::number_float:
@@ -4928,14 +4887,13 @@ class binary_writer
                    break;

                case value_t::number_unsigned:
-                    if (JSON_HEDLEY_LIKELY(integer_fits_max<std::int64_t>(value.m_data.m_value.number_unsigned)))
+                    if (JSON_HEDLEY_UNLIKELY(!integer_fits_max<std::int64_t>(value.m_data.m_value.number_unsigned)))
                    {
-                        write_bon8_integer(static_cast<std::int64_t>(value.m_data.m_value.number_unsigned));
-                        string_open = false;
-                        break;
+                        // too large for BON8
+                        throw_integer_out_of_range(value, input_format_t::bon8, "int64");
                    }
-                    // too large for BON8: throws
-                    write_bon8_value(value, string_open, depth + 1);
+                    write_bon8_integer(static_cast<std::int64_t>(value.m_data.m_value.number_unsigned));
+                    string_open = false;
                    break;

                case value_t::object:
@@ -116,6 +116,10 @@ inline void copy_short(CharType* dst, const CharType* src, const std::size_t len
 /// the number of characters an empty vector is grown to by output_vector_sink
 constexpr std::size_t min_vector_sink_capacity = 64;

+/// the number of characters output_vector_sink makes writable ahead of its
+/// position at a time: 64 KiB of the vector's capacity, not all of it
+constexpr std::size_t vector_sink_window = 65536;
+
 /// @brief non-virtual output sink writing into a std::vector
 ///
 /// This sink is not part of the virtual output_adapter_protocol hierarchy: it is
@@ -129,7 +133,8 @@ constexpr std::size_t min_vector_sink_capacity = 64;
 /// encoding them: insert() is an out-of-line call into a routine that can insert
 /// anywhere, and resize() is one as well with libstdc++. The sink therefore keeps
 /// its own write position: it grows the vector geometrically ahead of the
-/// position and copies each write to it, so a write is a capacity check and a
+/// position (making @ref vector_sink_window characters of it writable at a
+/// time) and copies each write to it, so a write is a capacity check and a
 /// short copy. The destructor shrinks the vector to the bytes actually written,
 /// also when a write throws; shrinking a vector never allocates. The sink owns
 /// that trim, so it can be moved but not copied, and the vector must not be used
@@ -277,9 +282,17 @@ class output_vector_sink
        // reallocate for every few bytes
        const std::size_t written = position();
        const std::size_t needed = written + length;
-        v->resize((std::max)(min_vector_sink_capacity, needed <= v->capacity()
-                             ? v->capacity()
-                             : (std::max)(needed, v->capacity() * 2)));
+        const std::size_t capacity = (std::max)(min_vector_sink_capacity, needed <= v->capacity()
+                                                ? v->capacity()
+                                                : (std::max)(needed, v->capacity() * 2));
+        v->reserve(capacity);
+        // resize() zeroes the characters it adds. Zeroing all of a doubled
+        // capacity, megabytes of a fresh allocation, at once faults in its
+        // pages and evicts them from the cache before the writer gets there,
+        // so its stores miss again; a window ahead of the position is still
+        // cached when they come (the binary writers on a long array of
+        // numbers: 4-26 % faster on x86, 1-2.5 % on Apple M1)
+        v->resize((std::min)(capacity, (std::max)(needed, written + vector_sink_window)));
        cursor = v->data() + written;
        limit = v->data() + v->size();
    }
@@ -8,7 +8,7 @@

 #pragma once

-#include <algorithm> // remove, fill, find, none_of, min
+#include <algorithm> // copy, none_of, min, search
 #include <array> // array
 #include <clocale> // localeconv, lconv
 #include <cmath> // isfinite
@@ -1113,36 +1113,21 @@ class serializer
                {
                    // the code point is at least 0x60 (smaller ones are handled
                    // above) and is not printable ASCII (which the scanner
-                    // copies): it is DEL (0x7F) under EnsureAscii or a non-ASCII
-                    // character
+                    // copies). Under EnsureAscii it is DEL (0x7F): every
+                    // well-formed multi-byte character is escaped by
+                    // write_u_escapes() above, so decode() only ever accepts a
+                    // single byte here, and nothing of it was buffered
                    if (EnsureAscii)
                    {
-                        JSON_ASSERT(codepoint >= 0x7F);
-                        if (error_handler == error_handler_t::keep)
-                        {
-                            // this character was buffered as raw bytes below
-                            // in case it turned out to be part of an
-                            // ill-formed sequence (which is kept as is); now
-                            // that it decoded to a well-formed code point,
-                            // undo that and \u-escape it like any other
-                            // character instead
-                            bytes = bytes_after_last_accept;
-                        }
-                        if (codepoint <= 0xFFFF)
-                        {
-                            write_u_escape(bytes, static_cast<std::uint16_t>(codepoint));
-                        }
-                        else
-                        {
-                            write_u_escape(bytes, static_cast<std::uint16_t>(0xD7C0u + (codepoint >> 10u)));
-                            write_u_escape(bytes, static_cast<std::uint16_t>(0xDC00u + (codepoint & 0x3FFu)));
-                        }
+                        JSON_ASSERT(codepoint == 0x7F);
+                        JSON_ASSERT(bytes == bytes_after_last_accept);
+                        write_u_escape(bytes, static_cast<std::uint16_t>(codepoint));
                    }
                    else
                    {
                        // copy byte to buffer (all previous bytes of the
                        // sequence have been copied in the default case below)
-                        string_buffer[bytes++] = s[i];
+                        string_buffer[bytes++] = s[i]; // LCOV_EXCL_LINE (well-formed sequences are copied in runs)
                    }

                    reserve_string_buffer(bytes);
@@ -2095,31 +2080,35 @@ class serializer
        // check if the buffer was large enough
        JSON_ASSERT(static_cast<std::size_t>(len) < number_buffer.size());

-        // look up the locale's thousands separator and decimal point now,
-        // matching what snprintf_float() just used (see lexer::get_decimal_point())
+        // look up the locale's decimal point now, matching what
+        // snprintf_float() just used (see get_decimal_point() in
+        // number_parse.hpp); it is a string, which can be longer than one
+        // byte (U+066B in ps_AF, #5993).
+        // A thousands separator needs no handling: %g never groups digits.
        const auto* loc = std::localeconv();
        JSON_ASSERT(loc != nullptr);
-        const char thousands_sep = (loc->thousands_sep == nullptr) ? '\0' : *loc->thousands_sep;
-        const char decimal_point = (loc->decimal_point == nullptr) ? '\0' : *loc->decimal_point;
-
-        // erase thousands separators
-        if (thousands_sep != '\0')
-        {
-            // NOLINTNEXTLINE(readability-qualified-auto,llvm-qualified-auto): std::remove returns an iterator, see https://github.com/nlohmann/json/issues/3081
-            const auto end = std::remove(number_buffer.begin(), number_buffer.begin() + len, thousands_sep);
-            std::fill(end, number_buffer.end(), '\0');
-            JSON_ASSERT((end - number_buffer.begin()) <= len);
-            len = (end - number_buffer.begin());
-        }
+        const char* const decimal_point = (loc->decimal_point == nullptr) ? "" : loc->decimal_point;
+        const std::size_t decimal_point_len = std::char_traits<char>::length(decimal_point);

        // convert decimal point to '.'
-        if (decimal_point != '\0' && decimal_point != '.')
+        if ((decimal_point_len > 1) || (decimal_point_len == 1 && decimal_point[0] != '.'))
        {
-            // NOLINTNEXTLINE(readability-qualified-auto,llvm-qualified-auto): std::find returns an iterator, see https://github.com/nlohmann/json/issues/3081
-            const auto dec_pos = std::find(number_buffer.begin(), number_buffer.end(), decimal_point);
-            if (dec_pos != number_buffer.end())
+            const auto first = number_buffer.begin();
+            const auto last = first + len;
+            // NOLINTNEXTLINE(readability-qualified-auto,llvm-qualified-auto): std::search returns an iterator, see https://github.com/nlohmann/json/issues/3081
+            const auto dec_pos = std::search(first, last, decimal_point, decimal_point + decimal_point_len);
+            if (dec_pos != last)
            {
                *dec_pos = '.';
+                if (decimal_point_len > 1)
+                {
+                    // move the fraction and exponent behind the '.' (std::copy
+                    // allows the overlap, as the destination is before the source)
+                    // NOLINTNEXTLINE(readability-qualified-auto,llvm-qualified-auto): std::copy returns an iterator, see https://github.com/nlohmann/json/issues/3081
+                    const auto end = std::copy(dec_pos + static_cast<std::ptrdiff_t>(decimal_point_len), last, dec_pos + 1);
+                    *end = '\0';
+                    len = end - first;
+                }
            }
        }

@@ -139,7 +139,7 @@ inline OutStringType concat(Args && ... args)
    str.reserve(concat_length(args...));
    concat_into(str, std::forward<Args>(args)...);
    return str;
-}
+} // LCOV_EXCL_LINE (exception cleanup only)

 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
@@ -83,10 +83,6 @@ template<typename StringType>
 inline void unescape(StringType& s)
 {
    auto pos = s.find_first_of('~', 0);
-    if (pos == StringType::npos)
-    {
-        return;
-    }

    StringType result;
    result.reserve(s.size());
@@ -13,7 +13,6 @@
 #include <cstddef> // size_t
 #include <cstdint> // uint8_t, uint32_t
 #include <string> // string, to_string
-#include <utility> // move

 #include <nlohmann/detail/abi_macros.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
@@ -37,7 +36,7 @@ StringType to_string(std::size_t value)
    StringType result;
    int_to_string(result, value);
    return result;
-}
+} // LCOV_EXCL_LINE (exception cleanup only)

 /// @return a byte as two uppercase hexadecimal digits
 inline std::string hex_byte(const std::uint8_t byte)
@@ -47,7 +46,7 @@ inline std::string hex_byte(const std::uint8_t byte)
    result[0] = nibble_to_hex[byte / 16];
    result[1] = nibble_to_hex[byte % 16];
    return result;
-}
+} // LCOV_EXCL_LINE (exception cleanup only)

 /*!
@brief write a UTF-16 code unit as four lowercase hexadecimal digits
@@ -391,7 +390,7 @@ inline StringType sanitize_utf8(const StringType& s, const error_handler_t error
    }

    return result;
-}
+} // LCOV_EXCL_LINE (exception cleanup only)

 }  // namespace detail
 NLOHMANN_JSON_NAMESPACE_END
@@ -1168,19 +1168,20 @@ indent_done:
            if (negative)
            {
                ++p;
+                if (NLOHMANN_VIEW_UNLIKELY(cur() < '0' || cur() > '9'))
+                {
+                    return fail(error_code::number_after_minus);
+                }
            }
            const unsigned char* const int_start = p;
            if (cur() == '0')
            {
                ++p;
            }
-            else if (NLOHMANN_VIEW_LIKELY(cur() >= '1' && cur() <= '9'))
-            {
-                p = skip_digits(p + 1, e);
-            }
            else
            {
-                return fail(error_code::number_after_minus);
+                // (a digit: the dispatch or the check after the sign saw it)
+                p = skip_digits(p + 1, e);
            }
            const auto int_digits = static_cast<std::size_t>(p - int_start);
            std::size_t frac_digits = 0;
@@ -397,9 +397,9 @@ class view_side
        return m_view.size();
    }

-    string_view_t string() const
+    string_view_t string() const noexcept
    {
-        return m_view.get_string();
+        return {m_view.m_doc->str(*m_view.m_node), m_view.m_node->len};
    }

    bool boolean() const noexcept
@@ -428,28 +428,19 @@ class view_side
        return string_view_t(m_view.m_doc->str(*m_view.m_node), m_view.m_node->len);
    }

-    /// a number, boolean, or null as a basic_json value (no allocation)
+    /// a number as a basic_json value (no allocation); only called for numbers
    BasicJsonType scalar() const
    {
-        switch (m_view.type())
+        const value_t t = m_view.type();
+        if (t == value_t::number_integer)
        {
-            case value_t::number_integer:
-                return BasicJsonType(m_view.template get<typename BasicJsonType::number_integer_t>());
-            case value_t::number_unsigned:
-                return BasicJsonType(m_view.template get<typename BasicJsonType::number_unsigned_t>());
-            case value_t::number_float:
-                return BasicJsonType(m_view.template get<typename BasicJsonType::number_float_t>());
-            case value_t::boolean:
-                return BasicJsonType(m_view.template get<bool>());
-            case value_t::null:
-            case value_t::object:
-            case value_t::array:
-            case value_t::string:
-            case value_t::binary:
-            case value_t::discarded:
-            default:
-                return BasicJsonType(nullptr);
+            return BasicJsonType(m_view.template get<typename BasicJsonType::number_integer_t>());
        }
+        if (t == value_t::number_unsigned)
+        {
+            return BasicJsonType(m_view.template get<typename BasicJsonType::number_unsigned_t>());
+        }
+        return BasicJsonType(m_view.template get<typename BasicJsonType::number_float_t>());
    }

    /// start at the first element of this array
@@ -531,9 +522,9 @@ class json_side
        return m_json->size();
    }

-    string_view_t string() const
+    string_view_t string() const noexcept
    {
-        const auto& s = m_json->template get_ref<const typename BasicJsonType::string_t&>();
+        const auto& s = *m_json->template get_ptr<const typename BasicJsonType::string_t*>();
        return string_view_t(s.data(), s.size());
    }

@@ -96,11 +96,11 @@ NLOHMANN_VIEW_NOINLINE inline void check_utf8_scan(const unsigned char* p, std::
        }
        if (*q >= 0x80)
        {
-            check_utf8_bytewise(p, n, static_cast<std::size_t>(q - p));
-            return; // not reached: the scan stopped at ill-formed UTF-8
+            break; // ill-formed UTF-8: reported below
        }
        ++q; // a quote, backslash, or control character
    }
+    check_utf8_bytewise(p, n, static_cast<std::size_t>(q - p));
 }

 inline void check_utf8(const char* s, std::size_t n)
@@ -158,7 +158,7 @@ inline void set_moved(document_data& d, node* n, node* seq, std::size_t cap)
        e.moved_cap[n->off] = cap;
        return;
    }
-    reserve_moved(d);
+    // every caller has called reserve_moved() (see above), so neither push_back() can throw
    e.moved.push_back(seq);
    e.moved_cap.push_back(cap);
    n->off = static_cast<std::uint32_t>(e.moved.size() - 1);
@@ -243,7 +243,7 @@ inline node* find_parent(const document_data& d, const node* target)
    }
    if (target == lo)
    {
-        return nullptr;
+        return nullptr; // LCOV_EXCL_LINE (the root, or a new value's root, which is linked)
    }
    for (;;)
    {
@@ -185,10 +185,6 @@ void value_range(const document_data& d, const node* n, std::size_t& start, std:
        end = p.end;
        return;
    }
-    if ((n->flags & node_flags::is_new) != 0 || n->off >= d.size)
-    {
-        return;
-    }
    // the open brackets: n, then the last element as long as it is a non-empty container
    std::size_t closing = 0;
    std::size_t pos = std::string::npos;
@@ -234,8 +230,7 @@ void value_range(const document_data& d, const node* n, std::size_t& start, std:

 /// the context basic_json puts in front of the message of an exception about
 /// a value: "(/path) " with JSON_DIAGNOSTICS (none for the root), then
-/// "(bytes a-b) " with JSON_DIAGNOSTIC_POSITIONS (with JSON_DIAGNOSTICS, only
-/// if there is a path)
+/// "(bytes a-b) " with JSON_DIAGNOSTIC_POSITIONS (also for the root)
 ///
 /// This and the throw helpers that take an error_site are templates, so that
 /// the path and range code is instantiated only where an exception can be
@@ -257,18 +252,22 @@ std::string diagnostics(const error_site site)
 #if JSON_DIAGNOSTICS
    std::vector<std::string> tokens;
    const bool found = edited ? value_path<true>(d, site.value(), tokens) : value_path<false>(d, site.value(), tokens);
-    if (!found || tokens.empty())
+    if (!found)
    {
-        // context is still empty; returning it keeps the copy elided (-Wnrvo)
+        // a value that is not found has no path, and with it no bytes
        return context;
    }
-    std::string path;
-    for (const std::string& token : tokens)
+    if (!tokens.empty())
    {
-        path.push_back('/');
-        path += detail::escape(token);
+        // the root value has no path, but still has a byte range
+        std::string path;
+        for (const std::string& token : tokens)
+        {
+            path.push_back('/');
+            path += detail::escape(token);
+        }
+        context = concat('(', path, ") ");
    }
-    context = concat('(', path, ") ");
 #endif
 #if JSON_DIAGNOSTIC_POSITIONS
    std::size_t start = 0;
@@ -420,10 +419,12 @@ struct throwing_sax
        return true;
    }

+    // LCOV_EXCL_START (throw_parse_failure parses JSON only)
    bool binary(binary_t& /*unused*/)
    {
        return true;
    }
+    // LCOV_EXCL_STOP

    bool start_object(std::size_t /*unused*/)
    {
@@ -452,21 +453,11 @@ struct throwing_sax

    /// (a template, as in json_sax_dom_parser: the parser passes the concrete
    /// exception type, which is thrown as is)
-    ///
-    /// It is not [[noreturn]]: sax_parse() recovers from an error if
-    /// parse_error() returns true, and MSVC reports that code as unreachable
-    /// (C4702) for a handler that never returns. The flag hides that from it.
    template<class Exception>
-    bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const Exception& ex)
+    [[noreturn]] bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const Exception& ex)
    {
-        if (throwing)
-        {
-            NLOHMANN_VIEW_THROW(ex);
-        }
-        return false; // LCOV_EXCL_LINE
+        NLOHMANN_VIEW_THROW(ex);
    }
-
-    bool throwing = true;
 };

 /*!
@@ -787,10 +787,6 @@ inline void load_image(document_data& d, const std::uint8_t* image, std::size_t
    d.edits.reset();
    d.base[2] = nullptr;
    d.owned.clear();
-    if (d.owned_image.empty() || image != d.owned_image.data())
-    {
-        d.owned_image.clear();
-    }
    d.arena.clear();
    d.indexes.clear();
    d.index_slots.clear();
@@ -65,14 +65,9 @@ struct position_source
        return token{end - start};
    }

-    /// the range [first, last), or none if either is npos
+    /// the range [first, last)
    void set(std::size_t first, std::size_t last) noexcept
    {
-        if (first == std::string::npos || last == std::string::npos)
-        {
-            clear();
-            return;
-        }
        start = first;
        end = last;
    }
@@ -191,11 +186,11 @@ struct position_source
                first = n.off;
                last = n.off + 4u;
                break;
-            case node_kind::object:
+            case node_kind::object: // LCOV_EXCL_LINE
            case node_kind::array:
            case node_kind::link:
            default:
-                break;
+                break; // LCOV_EXCL_LINE
        }
        // (a crafted image can point past the text)
        if (last == std::string::npos || last > d.size)
@@ -47,6 +47,7 @@ class output_buffer
        : m_out(sized(out, estimate))
        , m_pos(&m_out[0])
        , m_end(m_pos + m_out.size())
+        , m_reserved((std::max)(estimate, m_out.size()))
    {}

    void finish()
@@ -116,11 +117,12 @@ class output_buffer
        const auto used = static_cast<std::size_t>(m_pos - m_out.data());
        // (a step does not go beyond the reserved estimate, so that a good
        // estimate is never copied to a larger allocation; not a clamp: the
-        // lower bound used + n + 256 can exceed capacity(), and then it must win)
-        const std::size_t size = (std::max)((std::min)(m_out.size() + step, m_out.capacity()), used + n + 256);
-        if (size > m_out.capacity())
+        // lower bound used + n + 256 can exceed m_reserved, and then it must win)
+        const std::size_t size = (std::max)((std::min)(m_out.size() + step, m_reserved), used + n + 256);
+        if (size > m_reserved)
        {
-            m_out.reserve((std::max)(m_out.capacity() * 2, size));
+            m_reserved = (std::max)(m_reserved * 2, size);
+            m_out.reserve(m_reserved);
        }
        m_out.resize(size);
        m_pos = &m_out[0] + used;
@@ -130,6 +132,9 @@ class output_buffer
    StringType& m_out;
    char* m_pos;
    char* m_end;
+    /// what was last passed to reserve(), a lower bound of the capacity
+    /// (StringType need not have a capacity() member)
+    std::size_t m_reserved;
 };

 /// The length of the run at s that dump() writes unchanged without
@@ -641,7 +646,7 @@ class view_serializer
            {
                invalid_utf8(s, n.len); // (the scan stopped at ill-formed UTF-8)
            }
-            write_codepoint<false>(s[i], s + i, 1); // a quote, a backslash, or a control character
+            write_escaped(s[i]); // a quote, a backslash, or a control character
            ++i;
        }
        m_out.put('"');
@@ -1389,20 +1394,10 @@ class view_serializer
    /// a float node as dump() writes it
    void write_float_node(const node& n)
    {
-        write_float_node(n, fast_double {});
-    }
-
-    void write_float_node(const node& n, std::false_type /*other*/)
-    {
+        // (only for types other than double: doubles go through write_double_ahead())
        write_float(float_value<number_float_t>(m_doc, n));
    }

-    void write_float_node(const node& n, std::true_type /*double*/)
-    {
-        m_out.reserve(64);
-        m_out.set_cursor(write_double_at(m_out.cursor(), n));
-    }
-
    /*!
    @brief (doubles) the float at n as dump() writes it, at w (64 bytes of room)

@@ -1497,10 +1492,11 @@ class view_serializer
    {
        const string_t dumped = BasicJsonType(string_t(reinterpret_cast<const char*>(s), n)).dump(); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
        static_cast<void>(dumped);
-    }
+    } // LCOV_EXCL_LINE (dump() throws: the callers pass only ill-formed UTF-8)

-    template<bool EnsureAscii>
-    void write_codepoint(std::uint32_t codepoint, const unsigned char* bytes, std::size_t len)
+    /// write the escape sequence of a quote, a backslash or a control
+    /// character (the only bytes a run of plain output stops at)
+    void write_escaped(std::uint32_t codepoint)
    {
        switch (codepoint)
        {
@@ -1528,20 +1524,7 @@ class view_serializer
            default:
                break;
        }
-        if (codepoint <= 0x1F || (EnsureAscii && codepoint >= 0x7F))
-        {
-            if (codepoint <= 0xFFFF)
-            {
-                write_u_escape(codepoint);
-            }
-            else
-            {
-                write_u_escape(0xD7C0u + (codepoint >> 10u));
-                write_u_escape(0xDC00u + (codepoint & 0x3FFu));
-            }
-            return;
-        }
-        m_out.put(reinterpret_cast<const char*>(bytes), len); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast) LCOV_EXCL_LINE (printable characters are copied in runs)
+        write_u_escape(codepoint); // (a control character)
    }

    void write_u_escape(std::uint32_t u)
@@ -33,12 +33,37 @@ namespace view
 template<typename T>
 struct value_tag {};

+/// whether basic_json reads T with a dedicated from_json() overload that does
+/// not accept a boolean: exactly number_integer_t, number_unsigned_t and
+/// number_float_t (the other arithmetic types convert a boolean to 0 or 1)
+template<typename T, typename BasicJsonType>
+struct rejects_boolean : std::integral_constant < bool,
+    std::is_same<T, typename BasicJsonType::number_integer_t>::value
+    || std::is_same<T, typename BasicJsonType::number_unsigned_t>::value
+    || std::is_same<T, typename BasicJsonType::number_float_t>::value >
+{};
+
+/// a boolean as T: 0 or 1
+template<typename T>
+NLOHMANN_VIEW_ALWAYS_INLINE T boolean_as(const document_data& /*d*/, const node& n, std::false_type /*rejects*/)
+{
+    return static_cast<T>((n.flags & node_flags::is_true) != 0);
+}
+
+/// a boolean as number_integer_t, number_unsigned_t or number_float_t: type_error.302, as in basic_json
+template<typename T>
+[[noreturn]] NLOHMANN_VIEW_ALWAYS_INLINE T boolean_as(const document_data& d, const node& n, std::true_type /*rejects*/)
+{
+    throw_type_error(error_site(&d, &n), exception_id::type_mismatch, "type must be number, but is ", value_type_name(static_cast<value_t>(n.kind)));
+}
+
 /*!
@brief the number or boolean of a node converted to an arithmetic type

 As basic_json's get<T>() for arithmetic types: integers and floats are
-converted with static_cast, booleans give 0 or 1, and other types throw
-type_error.302.
+converted with static_cast, booleans give 0 or 1 (but throw type_error.302 for
+number_integer_t, number_unsigned_t and number_float_t, as basic_json does),
+and other types throw type_error.302.
 */
 template<typename T, typename BasicJsonType>
 NLOHMANN_VIEW_ALWAYS_INLINE T arithmetic_value(const document_data& d, const node& n)
@@ -52,7 +77,7 @@ NLOHMANN_VIEW_ALWAYS_INLINE T arithmetic_value(const document_data& d, const nod
        case value_t::number_float:
            return static_cast<T>(float_value<typename BasicJsonType::number_float_t>(d, n));
        case value_t::boolean:
-            return static_cast<T>((n.flags & node_flags::is_true) != 0);
+            return boolean_as<T>(d, n, rejects_boolean<T, BasicJsonType> {});
        case value_t::null:
        case value_t::object:
        case value_t::array:
@@ -157,7 +157,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    friend class ::nlohmann::detail::iter_impl;
    template<typename BasicJsonType, typename CharType, typename OutputSinkType>
    friend class ::nlohmann::detail::binary_writer;
-    template<typename BasicJsonType, typename InputType, typename SAX, bool AllowRecovery>
+    template<typename BasicJsonType, typename InputType, typename SAX>
    friend class ::nlohmann::detail::binary_reader;
    template<typename BasicJsonType, typename InputAdapterType, bool Collect, typename LexerType>
    friend class ::nlohmann::detail::json_sax_dom_parser;
@@ -400,7 +400,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
        result["compiler"] = {{"family", "clang"}, {"version", __clang_version__}};
 #elif defined(__GNUC__) || defined(__GNUG__)
        result["compiler"] = {{"family", "gcc"}, {"version", detail::concat<string_t>(
-                    detail::to_string<string_t>(static_cast<std::size_t>(__GNUC__)), '.',
+                    detail::to_string<string_t>(static_cast<std::size_t>(__GNUC__)), '.', // LCOV_EXCL_LINE
                    detail::to_string<string_t>(static_cast<std::size_t>(__GNUC_MINOR__)), '.',
                    detail::to_string<string_t>(static_cast<std::size_t>(__GNUC_PATCHLEVEL__)))
            }
@@ -543,6 +543,10 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
    ////////////////////////

  JSON_PRIVATE_UNLESS_TESTED:
+    // the type and value of a basic_json without its base class (defined
+    // below); the destruction helpers of json_value use it as a stand-in
+    struct data;
+
    /*!
    @brief a JSON value

@@ -672,14 +676,14 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                case value_t::binary:
                    binary = create<binary_t>();
                    break;
-                case value_t::null:
+                case value_t::null: // LCOV_EXCL_LINE
                case value_t::boolean:
                case value_t::number_integer:
                case value_t::number_unsigned:
                case value_t::number_float:
                case value_t::discarded:
                default:
-                    break;
+                    break; // LCOV_EXCL_LINE
            }
        }

@@ -719,27 +723,28 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
        explicit json_value(array_t* value) noexcept : array(value) {}

 private:
-        // raw, allocation-free transfer of m_data from src to dst: no
-        // set_parents()/assert_invariant() (the former is O(#children) per
-        // call under JSON_DIAGNOSTICS, which would make the walk below
-        // quadratic); dst takes ownership, src is left as value_t::null.
-        static void take(basic_json& dst, basic_json& src) noexcept
+        // raw, allocation-free transfer of the type and value from src to
+        // dst: no set_parents()/assert_invariant() (the former is
+        // O(#children) per call under JSON_DIAGNOSTICS, which would make the
+        // walk below quadratic); dst takes ownership, src is left as
+        // value_t::null.
+        static void take(data& dst, data& src) noexcept
        {
-            dst.m_data.m_type = src.m_data.m_type;
-            dst.m_data.m_value = src.m_data.m_value;
-            src.m_data.m_type = value_t::null;
+            dst.m_type = src.m_type;
+            dst.m_value = src.m_value;
+            src.m_type = value_t::null;
        }

        // true if v is not an array/object, or is an already-empty one
-        static bool has_no_children(const basic_json& v) noexcept
+        static bool has_no_children(const data& v) noexcept
        {
-            if (v.m_data.m_type == value_t::array)
+            if (v.m_type == value_t::array)
            {
-                return v.m_data.m_value.array->empty();
+                return v.m_value.array->empty();
            }
-            if (v.m_data.m_type == value_t::object)
+            if (v.m_type == value_t::object)
            {
-                return v.m_data.m_value.object->empty();
+                return v.m_value.object->empty();
            }
            return true;
        }
@@ -748,21 +753,21 @@ private:
        // its own, i.e. v can be freed in one go (its destructor then
        // destroys scalars and empty containers only, so it recurses at most
        // one level deep); stops at the first structured child it meets
-        static bool all_children_leaves(const basic_json& v) noexcept
+        static bool all_children_leaves(const data& v) noexcept
        {
            // array_t only needs forward iterators (see custom_array_type)
-            if (v.m_data.m_type == value_t::array)
+            if (v.m_type == value_t::array)
            {
-                const auto& a = *v.m_data.m_value.array;
+                const auto& a = *v.m_value.array;
                return std::all_of(a.begin(), a.end(), [](const basic_json & el)
                {
-                    return has_no_children(el);
+                    return has_no_children(el.m_data);
                });
            }
-            const auto& o = *v.m_data.m_value.object;
+            const auto& o = *v.m_value.object;
            return std::all_of(o.begin(), o.end(), [](const typename object_t::value_type & el)
            {
-                return has_no_children(el.second);
+                return has_no_children(el.second.m_data);
            });
        }

@@ -794,30 +799,30 @@ private:

        // the child of a non-empty array/object v that the walk in
        // destroy_container() continues with (see walk_child_it() above)
-        static basic_json& walk_child(basic_json& v)
+        static data& walk_child(data& v)
        {
-            if (v.m_data.m_type == value_t::array)
+            if (v.m_type == value_t::array)
            {
-                return v.m_data.m_value.array->back();
+                return v.m_value.array->back().m_data;
            }
-            JSON_ASSERT(v.m_data.m_type == value_t::object);
-            return walk_child_it(*v.m_data.m_value.object)->second;
+            JSON_ASSERT(v.m_type == value_t::object);
+            return walk_child_it(*v.m_value.object)->second.m_data;
        }

        // removes walk_child(v) from a non-empty array/object v; this never
        // allocates, and since it is only ever called when that child is a
        // scalar or an already-empty array/object, destroying it never
        // recurses more than one level deep (see destroy() below)
-        static void pop_walk_child(basic_json& v)
+        static void pop_walk_child(data& v)
        {
-            if (v.m_data.m_type == value_t::array)
+            if (v.m_type == value_t::array)
            {
-                v.m_data.m_value.array->pop_back();
+                v.m_value.array->pop_back();
            }
            else
            {
-                JSON_ASSERT(v.m_data.m_type == value_t::object);
-                v.m_data.m_value.object->erase(walk_child_it(*v.m_data.m_value.object));
+                JSON_ASSERT(v.m_type == value_t::object);
+                v.m_value.object->erase(walk_child_it(*v.m_value.object));
            }
        }

@@ -826,23 +831,23 @@ private:
        // recurses at most one level deep); this is the same allocator-based
        // free the old recursive implementation used, just factored out so
        // every level of the walk in destroy() can share it
-        static void free_container(basic_json& v) noexcept
+        static void free_container(data& v) noexcept
        {
            JSON_ASSERT(has_no_children(v) || all_children_leaves(v));
-            if (v.m_data.m_type == value_t::array)
+            if (v.m_type == value_t::array)
            {
                AllocatorType<array_t> alloc;
-                std::allocator_traits<decltype(alloc)>::destroy(alloc, v.m_data.m_value.array);
-                std::allocator_traits<decltype(alloc)>::deallocate(alloc, v.m_data.m_value.array, 1);
+                std::allocator_traits<decltype(alloc)>::destroy(alloc, v.m_value.array);
+                std::allocator_traits<decltype(alloc)>::deallocate(alloc, v.m_value.array, 1);
            }
            else
            {
-                JSON_ASSERT(v.m_data.m_type == value_t::object);
+                JSON_ASSERT(v.m_type == value_t::object);
                AllocatorType<object_t> alloc;
-                std::allocator_traits<decltype(alloc)>::destroy(alloc, v.m_data.m_value.object);
-                std::allocator_traits<decltype(alloc)>::deallocate(alloc, v.m_data.m_value.object, 1);
+                std::allocator_traits<decltype(alloc)>::destroy(alloc, v.m_value.object);
+                std::allocator_traits<decltype(alloc)>::deallocate(alloc, v.m_value.object, 1);
            }
-            v.m_data.m_type = value_t::null; // avoid a double free if v is later destructed
+            v.m_type = value_t::null; // avoid a double free if v is later destructed
        }

 public:
@@ -873,14 +878,15 @@ public:

            // This json_value is not itself a basic_json, so the top-level
            // container is first moved into a local stand-in ("cur"); a
-            // default-constructed basic_json has a null pointer in its
-            // m_value (see data::m_value's initializer), so swapping it
-            // with *this leaves this union's own pointer null, and it is
-            // never looked at or freed a second time.
-            basic_json cur;
-            cur.m_data.m_type = t;
-            using std::swap;
-            swap(cur.m_data.m_value, *this);
+            // default-constructed data has a null pointer in its m_value
+            // (see data::m_value's initializer), so swapping it with *this
+            // leaves this union's own pointer null, and it is never looked
+            // at or freed a second time. The stand-ins are data, not
+            // basic_json, so that destroying a value never constructs a
+            // CustomBaseClass, whose constructor may allocate (#5995).
+            data cur;
+            cur.m_type = t;
+            std::swap(cur.m_value, *this);

            destroy_bounded(cur, 0);
        }
@@ -889,7 +895,7 @@ public:
        // The first recursion_depth_limit() levels are destroyed by plain
        // recursion, which is the fastest way and cannot throw; anything
        // nested deeper is handed to destroy_walk(), which uses no call stack.
-        static void destroy_bounded(basic_json& v, std::size_t depth) noexcept
+        static void destroy_bounded(data& v, std::size_t depth) noexcept
        {
            if (JSON_HEDLEY_UNLIKELY(depth >= detail::recursion_depth_limit()))
            {
@@ -897,23 +903,23 @@ public:
                return;
            }

-            if (v.m_data.m_type == value_t::array)
+            if (v.m_type == value_t::array)
            {
-                for (auto& child : *v.m_data.m_value.array)
+                for (auto& child : *v.m_value.array)
                {
                    if (child.m_data.m_type == value_t::array || child.m_data.m_type == value_t::object)
                    {
-                        destroy_bounded(child, depth + 1);
+                        destroy_bounded(child.m_data, depth + 1);
                    }
                }
            }
            else
            {
-                for (auto& child : *v.m_data.m_value.object)
+                for (auto& child : *v.m_value.object)
                {
                    if (child.second.m_data.m_type == value_t::array || child.second.m_data.m_type == value_t::object)
                    {
-                        destroy_bounded(child.second, depth + 1);
+                        destroy_bounded(child.second.m_data, depth + 1);
                    }
                }
            }
@@ -940,18 +946,15 @@ public:
        // array/object, which neither allocates nor recurses more
        // than one level deep.
        //
-        // This json_value is not itself a basic_json, so the
-        // top-level container is first moved into a local stand-in
-        // ("cur"); a default-constructed basic_json has a null
-        // pointer in its m_value (see data::m_value's initializer),
-        // so swapping it with *this leaves this union's own pointer
-        // null, and it is never looked at or freed a second time.
-        static void destroy_walk(basic_json& top) noexcept
+        // Like destroy_container(), the walk keeps the containers it
+        // holds in data stand-ins (cur, prev, gp, tmp), which never
+        // construct a CustomBaseClass.
+        static void destroy_walk(data& top) noexcept
        {
-            basic_json cur;
+            data cur;
            take(cur, top);

-            basic_json prev; // value_t::null: no parent
+            data prev; // value_t::null: no parent

            // true right after cur was entered: its children have not been
            // looked at yet. If none of them has children of its own, cur is
@@ -965,7 +968,7 @@ public:
                fresh = false;
                if (has_no_children(cur) || (fresh_now && all_children_leaves(cur)))
                {
-                    if (prev.m_data.m_type == value_t::null)
+                    if (prev.m_type == value_t::null)
                    {
                        free_container(cur);
                        return; // back at the top with nothing left to do
@@ -974,7 +977,7 @@ public:
                    // ascend: detach the grandparent link from prev's
                    // walk_child() slot, drop that (now null) slot, free cur
                    // (it is empty), then move up one level
-                    basic_json gp;
+                    data gp;
                    take(gp, walk_child(prev));
                    pop_walk_child(prev);

@@ -985,7 +988,7 @@ public:
                    continue;
                }

-                basic_json& cur_child_ref = walk_child(cur);
+                data& cur_child_ref = walk_child(cur);

                if (has_no_children(cur_child_ref))
                {
@@ -997,7 +1000,7 @@ public:
                // descend into the non-empty child, reversing the
                // link: its slot takes over prev, and the child becomes
                // the new cur
-                basic_json tmp;
+                data tmp;
                take(tmp, cur_child_ref);
                take(cur_child_ref, prev);
                take(prev, cur);
@@ -1034,14 +1037,14 @@ public:
                    destroy_container(t);
                    break;

-                case value_t::null:
+                case value_t::null: // LCOV_EXCL_LINE
                case value_t::boolean:
                case value_t::number_integer:
                case value_t::number_unsigned:
                case value_t::number_float:
                case value_t::discarded:
                default:
-                    break;
+                    break; // LCOV_EXCL_LINE
            }
        }
    };
@@ -1214,9 +1217,9 @@ public:
        return is_array() ? array_capacity() : object_capacity();
    }
 #else
-    static constexpr std::size_t container_capacity() noexcept
+    static constexpr std::size_t container_capacity() noexcept // LCOV_EXCL_LINE
    {
-        return detail::unknown_size();
+        return detail::unknown_size(); // LCOV_EXCL_LINE
    }
 #endif

@@ -1402,7 +1405,7 @@ public:
    ///       into this switch is worth a few percent when copying a value made
    ///       mostly of numbers
    JSON_HEDLEY_ALWAYS_INLINE
-    static void copy_leaf_value(const basic_json& src, basic_json& dst)
+    static void copy_leaf_value(const basic_json& src, basic_json& dst) // LCOV_EXCL_LINE
    {
        switch (src.m_data.m_type)
        {
@@ -1576,7 +1579,7 @@ public:
        auto src_it = src_object.cbegin();
        for (auto& element : *dst.m_data.m_value.object)
        {
-            if (JSON_HEDLEY_LIKELY(src_it != src_object.cend() && copy_keys_equal(src_it->first, element.first)))
+            if (JSON_HEDLEY_LIKELY(copy_keys_equal(src_it->first, element.first)))
            {
                copy_shallow(src_it->second, element.second, worklist);
                ++src_it;
@@ -3134,8 +3137,7 @@ public:
        {
            return parser(std::move(ia), nullptr, true, ignore_comments, ignore_trailing_commas).sax_parse(sax, strict);
        }
-        // the SAX parser may recover from errors (see parse_error())
-        return detail::binary_reader<basic_json, InputAdapterType, SAX, true>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
+        return detail::binary_reader<basic_json, InputAdapterType, SAX>(std::move(ia), format).sax_parse(sax, strict, tag_handler);
    }

    /// serialize @a j into a new vector; @a write receives the vector-backed writer
@@ -4915,6 +4917,30 @@ public:
        return {it, res.second};
    }

+  private:
+    /// Sets the parents of a value when it goes out of scope, also when an
+    /// exception is thrown: a container insertion that throws may already
+    /// have added elements, whose parents must be set for the value to stay
+    /// valid (basic exception guarantee). Does nothing without JSON_DIAGNOSTICS.
+    class set_parents_on_exit
+    {
+      public:
+        explicit set_parents_on_exit(basic_json* v) noexcept : m_value(v) {}
+        set_parents_on_exit(const set_parents_on_exit&) = delete;
+        set_parents_on_exit& operator=(const set_parents_on_exit&) = delete;
+        set_parents_on_exit(set_parents_on_exit&&) = delete;
+        set_parents_on_exit& operator=(set_parents_on_exit&&) = delete;
+
+        ~set_parents_on_exit()
+        {
+            m_value->set_parents();
+        }
+
+      private:
+        basic_json* m_value;
+    };
+
+  public:
    /// Helper for insertion of an iterator
    /// @note: This uses std::distance to support GCC 4.8,
    ///        see https://github.com/nlohmann/json/pull/1257
@@ -4924,6 +4950,7 @@ public:
        iterator result(this);
        JSON_ASSERT(m_data.m_value.array != nullptr);

+        const set_parents_on_exit parents(this);
        auto insert_pos = std::distance(m_data.m_value.array->begin(), pos.m_it.array_iterator);
        m_data.m_value.array->insert(pos.m_it.array_iterator, std::forward<Args>(args)...);
        result.m_it.array_iterator = m_data.m_value.array->begin() + insert_pos;
@@ -4932,7 +4959,6 @@ public:
        // result.m_it.array_iterator = m_data.m_value.array->insert(pos.m_it.array_iterator, cnt, val);
        // but the return value of insert is missing in GCC 4.8, so it is written this way instead.

-        set_parents();
        return result;
    }

@@ -4952,8 +4978,16 @@ public:
            throw_iterator_from_other_value(this);
        }

-        // insert to array and return iterator
-        return insert_iterator(pos, val);
+        // vector::insert has no effects if copying a single element to the
+        // end throws; elsewhere, it may already have shifted the elements, so
+        // copy first and insert by move, which cannot throw but by allocating
+        if (pos.m_it.array_iterator == m_data.m_value.array->end())
+        {
+            return insert_iterator(pos, val);
+        }
+
+        basic_json tmp(val);
+        return insert_iterator(pos, std::move(tmp));
    }

    /// @brief inserts element into array
@@ -5085,8 +5119,8 @@ public:
            detail::throw_literal<invalid_iterator>(detail::exception_id::iterator_from_other_value, "iterators first and last must point to objects", this);
        }

+        const set_parents_on_exit parents(this);
        m_data.m_value.object->insert(first.m_it.object_iterator, last.m_it.object_iterator);
-        set_parents();
    }

    /// @brief updates a JSON object from another object, overwriting existing keys
@@ -5354,8 +5388,7 @@ public:
    /// @name lexicographical comparison operators
    /// @{

-    // the same-type cases for non-owning scalars, shared by JSON_IMPLEMENT_OPERATOR
-    // and JSON_IMPLEMENT_SCALAR_FAST
+    // the same-type cases for non-owning scalars, used by JSON_IMPLEMENT_SCALAR_FAST
 #define JSON_IMPLEMENT_SCALAR_CASES(op, null_result)                                                     \
  case value_t::null:                                                                                  \
        return (null_result);                                                                            \
@@ -5377,7 +5410,7 @@ public:
    // because any negative signed value is smaller than any unsigned value.
    // Otherwise, the non-negative signed value is cast to unsigned before the
    // comparison to avoid wraparound.
-#define JSON_IMPLEMENT_OPERATOR(op, null_result, unordered_result, default_result, deep_result, may_descend) \
+#define JSON_IMPLEMENT_OPERATOR(op, unordered_result, default_result, deep_result, may_descend)          \
    const auto lhs_type = lhs.type();                                                                    \
    const auto rhs_type = rhs.type();                                                                    \
    \
@@ -5405,8 +5438,15 @@ public:
                return (*lhs.m_data.m_value.object) op (*rhs.m_data.m_value.object);                                   \
            }                                                                                            \
            \
-            JSON_IMPLEMENT_SCALAR_CASES(op, null_result)                                                 \
-            \
+                /* same-type scalars never get here: the inline fast path of the operator handles them */ \
+            case value_t::null:                                                                          \
+            case value_t::boolean:                                                                       \
+            case value_t::number_integer:                                                                \
+            case value_t::number_unsigned:                                                               \
+            case value_t::number_float:                                                                  \
+                JSON_ASSERT(false); /* NOLINT(cert-dcl03-c,hicpp-static-assert,misc-static-assert) */ \
+                return (unordered_result);                                                               \
+                \
            case value_t::string:                                                                        \
                return (*lhs.m_data.m_value.string) op (*rhs.m_data.m_value.string);                                   \
                \
@@ -5446,7 +5486,7 @@ public:
               ? (number_integer_t(-1) op number_integer_t(1))                                           \
               : (static_cast<number_unsigned_t>(lhs.m_data.m_value.number_integer) op rhs.m_data.m_value.number_unsigned); \
    }                                                                                             \
-    else if(compares_unordered(lhs, rhs))\
+    else if(lhs_type == value_t::discarded || rhs_type == value_t::discarded)\
    {\
        return (unordered_result);\
    }\
@@ -5514,7 +5554,7 @@ public:
        JSON_HEDLEY_DIAGNOSTIC_PUSH
        JSON_HEDLEY_PRAGMA(GCC diagnostic ignored "-Wfloat-equal")
 #endif
-        JSON_IMPLEMENT_OPERATOR( ==, true, false, false,
+        JSON_IMPLEMENT_OPERATOR( ==, false, false,
                                 compare_iteratively<false>(lhs, rhs, false) == compare_result::equal, true)
 #ifdef __GNUC__
        JSON_HEDLEY_DIAGNOSTIC_POP
@@ -5528,7 +5568,6 @@ public:
        // default_result is used if we cannot compare values. In that case,
        // we compare types.
        JSON_IMPLEMENT_OPERATOR(<=>, // *NOPAD*
-                                std::partial_ordering::equivalent,
                                std::partial_ordering::unordered,
                                lhs_type <=> rhs_type, // *NOPAD*
                                to_partial_ordering(compare_iteratively<true>(lhs, rhs, false)), true)
@@ -5540,7 +5579,7 @@ public:
        // default_result is used if we cannot compare values. In that case,
        // we compare types. Note we have to call the operator explicitly,
        // because MSVC has problems otherwise.
-        JSON_IMPLEMENT_OPERATOR( <, false, false, operator<(lhs_type, rhs_type),
+        JSON_IMPLEMENT_OPERATOR( <, false, operator<(lhs_type, rhs_type),
                                 compare_iteratively<true>(lhs, rhs, true) == compare_result::less, false)
    }
 #endif
@@ -5555,7 +5594,7 @@ public:
    ///       their inlined code at each call site small. Binary values are
    ///       rare and left to equal_general().
    JSON_HEDLEY_ALWAYS_INLINE
-    static int equal_leaf(const_reference lhs, const_reference rhs) noexcept
+    static int equal_leaf(const_reference lhs, const_reference rhs) noexcept // LCOV_EXCL_LINE
    {
 #ifdef __GNUC__
        JSON_HEDLEY_DIAGNOSTIC_PUSH
@@ -6864,7 +6903,7 @@ public:
        basic_json result(value_t::object);
        json_pointer::flatten("", *this, result);
        return result;
-    }
+    } // LCOV_EXCL_LINE (exception cleanup only)

    /// @brief unflatten a previously flattened JSON value
    /// @sa https://json.nlohmann.me/api/basic_json/unflatten/
@@ -7577,7 +7616,7 @@ public:
        result.append(path.data(), path.size());
        diff_append_key(result, key);
        return result;
-    }
+    } // LCOV_EXCL_LINE (exception cleanup only)

    /// @brief the path of the element @a index of the value at @a path
    static string_t diff_index_path(const string_t& path, const std::size_t index)
@@ -7587,7 +7626,7 @@ public:
        result.append(path.data(), path.size());
        diff_append_index(result, index);
        return result;
-    }
+    } // LCOV_EXCL_LINE (exception cleanup only)

    /// @brief append the "remove" operations for the elements of array
    ///        @a source from @a index on, and the "add" operations for the
@@ -7747,7 +7786,7 @@ public:
        // operations
        if (source == target)
        {
-            return false;
+            return false; // LCOV_EXCL_LINE (equal objects with the same members in the same order return early)
        }

        // slow path: the common keys are in a different relative
@@ -1705,9 +1705,11 @@ class basic_json_document
        {
            // (as before: the library's adapter decides what a null stream yields)
            detail::view::append_adapter(buf, detail::input_adapter(file));
-            return;
        }
-        detail::view::append_file(buf, file);
+        else
+        {
+            detail::view::append_file(buf, file);
+        }
    }
 #endif

@@ -2473,19 +2473,20 @@ indent_done:
            if (negative)
            {
                ++p;
+                if (NLOHMANN_VIEW_UNLIKELY(cur() < '0' || cur() > '9'))
+                {
+                    return fail(error_code::number_after_minus);
+                }
            }
            const unsigned char* const int_start = p;
            if (cur() == '0')
            {
                ++p;
            }
-            else if (NLOHMANN_VIEW_LIKELY(cur() >= '1' && cur() <= '9'))
-            {
-                p = skip_digits(p + 1, e);
-            }
            else
            {
-                return fail(error_code::number_after_minus);
+                // (a digit: the dispatch or the check after the sign saw it)
+                p = skip_digits(p + 1, e);
            }
            const auto int_digits = static_cast<std::size_t>(p - int_start);
            std::size_t frac_digits = 0;
@@ -3549,9 +3550,9 @@ class view_side
        return m_view.size();
    }

-    string_view_t string() const
+    string_view_t string() const noexcept
    {
-        return m_view.get_string();
+        return {m_view.m_doc->str(*m_view.m_node), m_view.m_node->len};
    }

    bool boolean() const noexcept
@@ -3580,28 +3581,19 @@ class view_side
        return string_view_t(m_view.m_doc->str(*m_view.m_node), m_view.m_node->len);
    }

-    /// a number, boolean, or null as a basic_json value (no allocation)
+    /// a number as a basic_json value (no allocation); only called for numbers
    BasicJsonType scalar() const
    {
-        switch (m_view.type())
+        const value_t t = m_view.type();
+        if (t == value_t::number_integer)
        {
-            case value_t::number_integer:
-                return BasicJsonType(m_view.template get<typename BasicJsonType::number_integer_t>());
-            case value_t::number_unsigned:
-                return BasicJsonType(m_view.template get<typename BasicJsonType::number_unsigned_t>());
-            case value_t::number_float:
-                return BasicJsonType(m_view.template get<typename BasicJsonType::number_float_t>());
-            case value_t::boolean:
-                return BasicJsonType(m_view.template get<bool>());
-            case value_t::null:
-            case value_t::object:
-            case value_t::array:
-            case value_t::string:
-            case value_t::binary:
-            case value_t::discarded:
-            default:
-                return BasicJsonType(nullptr);
+            return BasicJsonType(m_view.template get<typename BasicJsonType::number_integer_t>());
        }
+        if (t == value_t::number_unsigned)
+        {
+            return BasicJsonType(m_view.template get<typename BasicJsonType::number_unsigned_t>());
+        }
+        return BasicJsonType(m_view.template get<typename BasicJsonType::number_float_t>());
    }

    /// start at the first element of this array
@@ -3683,9 +3675,9 @@ class json_side
        return m_json->size();
    }

-    string_view_t string() const
+    string_view_t string() const noexcept
    {
-        const auto& s = m_json->template get_ref<const typename BasicJsonType::string_t&>();
+        const auto& s = *m_json->template get_ptr<const typename BasicJsonType::string_t*>();
        return string_view_t(s.data(), s.size());
    }

@@ -4478,14 +4470,9 @@ struct position_source
        return token{end - start};
    }

-    /// the range [first, last), or none if either is npos
+    /// the range [first, last)
    void set(std::size_t first, std::size_t last) noexcept
    {
-        if (first == std::string::npos || last == std::string::npos)
-        {
-            clear();
-            return;
-        }
        start = first;
        end = last;
    }
@@ -4604,11 +4591,11 @@ struct position_source
                first = n.off;
                last = n.off + 4u;
                break;
-            case node_kind::object:
+            case node_kind::object: // LCOV_EXCL_LINE
            case node_kind::array:
            case node_kind::link:
            default:
-                break;
+                break; // LCOV_EXCL_LINE
        }
        // (a crafted image can point past the text)
        if (last == std::string::npos || last > d.size)
@@ -5027,10 +5014,6 @@ void value_range(const document_data& d, const node* n, std::size_t& start, std:
        end = p.end;
        return;
    }
-    if ((n->flags & node_flags::is_new) != 0 || n->off >= d.size)
-    {
-        return;
-    }
    // the open brackets: n, then the last element as long as it is a non-empty container
    std::size_t closing = 0;
    std::size_t pos = std::string::npos;
@@ -5076,8 +5059,7 @@ void value_range(const document_data& d, const node* n, std::size_t& start, std:

 /// the context basic_json puts in front of the message of an exception about
 /// a value: "(/path) " with JSON_DIAGNOSTICS (none for the root), then
-/// "(bytes a-b) " with JSON_DIAGNOSTIC_POSITIONS (with JSON_DIAGNOSTICS, only
-/// if there is a path)
+/// "(bytes a-b) " with JSON_DIAGNOSTIC_POSITIONS (also for the root)
 ///
 /// This and the throw helpers that take an error_site are templates, so that
 /// the path and range code is instantiated only where an exception can be
@@ -5099,18 +5081,22 @@ std::string diagnostics(const error_site site)
 #if JSON_DIAGNOSTICS
    std::vector<std::string> tokens;
    const bool found = edited ? value_path<true>(d, site.value(), tokens) : value_path<false>(d, site.value(), tokens);
-    if (!found || tokens.empty())
+    if (!found)
    {
-        // context is still empty; returning it keeps the copy elided (-Wnrvo)
+        // a value that is not found has no path, and with it no bytes
        return context;
    }
-    std::string path;
-    for (const std::string& token : tokens)
+    if (!tokens.empty())
    {
-        path.push_back('/');
-        path += detail::escape(token);
+        // the root value has no path, but still has a byte range
+        std::string path;
+        for (const std::string& token : tokens)
+        {
+            path.push_back('/');
+            path += detail::escape(token);
+        }
+        context = concat('(', path, ") ");
    }
-    context = concat('(', path, ") ");
 #endif
 #if JSON_DIAGNOSTIC_POSITIONS
    std::size_t start = 0;
@@ -5262,10 +5248,12 @@ struct throwing_sax
        return true;
    }

+    // LCOV_EXCL_START (throw_parse_failure parses JSON only)
    bool binary(binary_t& /*unused*/)
    {
        return true;
    }
+    // LCOV_EXCL_STOP

    bool start_object(std::size_t /*unused*/)
    {
@@ -5294,21 +5282,11 @@ struct throwing_sax

    /// (a template, as in json_sax_dom_parser: the parser passes the concrete
    /// exception type, which is thrown as is)
-    ///
-    /// It is not [[noreturn]]: sax_parse() recovers from an error if
-    /// parse_error() returns true, and MSVC reports that code as unreachable
-    /// (C4702) for a handler that never returns. The flag hides that from it.
    template<class Exception>
-    bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const Exception& ex)
+    [[noreturn]] bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const Exception& ex)
    {
-        if (throwing)
-        {
-            NLOHMANN_VIEW_THROW(ex);
-        }
-        return false; // LCOV_EXCL_LINE
+        NLOHMANN_VIEW_THROW(ex);
    }
-
-    bool throwing = true;
 };

 /*!
@@ -5498,7 +5476,7 @@ inline void set_moved(document_data& d, node* n, node* seq, std::size_t cap)
        e.moved_cap[n->off] = cap;
        return;
    }
-    reserve_moved(d);
+    // every caller has called reserve_moved() (see above), so neither push_back() can throw
    e.moved.push_back(seq);
    e.moved_cap.push_back(cap);
    n->off = static_cast<std::uint32_t>(e.moved.size() - 1);
@@ -5583,7 +5561,7 @@ inline node* find_parent(const document_data& d, const node* target)
    }
    if (target == lo)
    {
-        return nullptr;
+        return nullptr; // LCOV_EXCL_LINE (the root, or a new value's root, which is linked)
    }
    for (;;)
    {
@@ -6204,11 +6182,11 @@ NLOHMANN_VIEW_NOINLINE inline void check_utf8_scan(const unsigned char* p, std::
        }
        if (*q >= 0x80)
        {
-            check_utf8_bytewise(p, n, static_cast<std::size_t>(q - p));
-            return; // not reached: the scan stopped at ill-formed UTF-8
+            break; // ill-formed UTF-8: reported below
        }
        ++q; // a quote, backslash, or control character
    }
+    check_utf8_bytewise(p, n, static_cast<std::size_t>(q - p));
 }

 inline void check_utf8(const char* s, std::size_t n)
@@ -7802,10 +7780,6 @@ inline void load_image(document_data& d, const std::uint8_t* image, std::size_t
    d.edits.reset();
    d.base[2] = nullptr;
    d.owned.clear();
-    if (d.owned_image.empty() || image != d.owned_image.data())
-    {
-        d.owned_image.clear();
-    }
    d.arena.clear();
    d.indexes.clear();
    d.index_slots.clear();
@@ -8521,6 +8495,7 @@ class output_buffer
        : m_out(sized(out, estimate))
        , m_pos(&m_out[0])
        , m_end(m_pos + m_out.size())
+        , m_reserved((std::max)(estimate, m_out.size()))
    {}

    void finish()
@@ -8590,11 +8565,12 @@ class output_buffer
        const auto used = static_cast<std::size_t>(m_pos - m_out.data());
        // (a step does not go beyond the reserved estimate, so that a good
        // estimate is never copied to a larger allocation; not a clamp: the
-        // lower bound used + n + 256 can exceed capacity(), and then it must win)
-        const std::size_t size = (std::max)((std::min)(m_out.size() + step, m_out.capacity()), used + n + 256);
-        if (size > m_out.capacity())
+        // lower bound used + n + 256 can exceed m_reserved, and then it must win)
+        const std::size_t size = (std::max)((std::min)(m_out.size() + step, m_reserved), used + n + 256);
+        if (size > m_reserved)
        {
-            m_out.reserve((std::max)(m_out.capacity() * 2, size));
+            m_reserved = (std::max)(m_reserved * 2, size);
+            m_out.reserve(m_reserved);
        }
        m_out.resize(size);
        m_pos = &m_out[0] + used;
@@ -8604,6 +8580,9 @@ class output_buffer
    StringType& m_out;
    char* m_pos;
    char* m_end;
+    /// what was last passed to reserve(), a lower bound of the capacity
+    /// (StringType need not have a capacity() member)
+    std::size_t m_reserved;
 };

 /// The length of the run at s that dump() writes unchanged without
@@ -9115,7 +9094,7 @@ class view_serializer
            {
                invalid_utf8(s, n.len); // (the scan stopped at ill-formed UTF-8)
            }
-            write_codepoint<false>(s[i], s + i, 1); // a quote, a backslash, or a control character
+            write_escaped(s[i]); // a quote, a backslash, or a control character
            ++i;
        }
        m_out.put('"');
@@ -9863,20 +9842,10 @@ class view_serializer
    /// a float node as dump() writes it
    void write_float_node(const node& n)
    {
-        write_float_node(n, fast_double {});
-    }
-
-    void write_float_node(const node& n, std::false_type /*other*/)
-    {
+        // (only for types other than double: doubles go through write_double_ahead())
        write_float(float_value<number_float_t>(m_doc, n));
    }

-    void write_float_node(const node& n, std::true_type /*double*/)
-    {
-        m_out.reserve(64);
-        m_out.set_cursor(write_double_at(m_out.cursor(), n));
-    }
-
    /*!
    @brief (doubles) the float at n as dump() writes it, at w (64 bytes of room)

@@ -9971,10 +9940,11 @@ class view_serializer
    {
        const string_t dumped = BasicJsonType(string_t(reinterpret_cast<const char*>(s), n)).dump(); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
        static_cast<void>(dumped);
-    }
+    } // LCOV_EXCL_LINE (dump() throws: the callers pass only ill-formed UTF-8)

-    template<bool EnsureAscii>
-    void write_codepoint(std::uint32_t codepoint, const unsigned char* bytes, std::size_t len)
+    /// write the escape sequence of a quote, a backslash or a control
+    /// character (the only bytes a run of plain output stops at)
+    void write_escaped(std::uint32_t codepoint)
    {
        switch (codepoint)
        {
@@ -10002,20 +9972,7 @@ class view_serializer
            default:
                break;
        }
-        if (codepoint <= 0x1F || (EnsureAscii && codepoint >= 0x7F))
-        {
-            if (codepoint <= 0xFFFF)
-            {
-                write_u_escape(codepoint);
-            }
-            else
-            {
-                write_u_escape(0xD7C0u + (codepoint >> 10u));
-                write_u_escape(0xDC00u + (codepoint & 0x3FFu));
-            }
-            return;
-        }
-        m_out.put(reinterpret_cast<const char*>(bytes), len); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast) LCOV_EXCL_LINE (printable characters are copied in runs)
+        write_u_escape(codepoint); // (a control character)
    }

    void write_u_escape(std::uint32_t u)
@@ -10077,12 +10034,37 @@ namespace view
 template<typename T>
 struct value_tag {};

+/// whether basic_json reads T with a dedicated from_json() overload that does
+/// not accept a boolean: exactly number_integer_t, number_unsigned_t and
+/// number_float_t (the other arithmetic types convert a boolean to 0 or 1)
+template<typename T, typename BasicJsonType>
+struct rejects_boolean : std::integral_constant < bool,
+    std::is_same<T, typename BasicJsonType::number_integer_t>::value
+    || std::is_same<T, typename BasicJsonType::number_unsigned_t>::value
+    || std::is_same<T, typename BasicJsonType::number_float_t>::value >
+{};
+
+/// a boolean as T: 0 or 1
+template<typename T>
+NLOHMANN_VIEW_ALWAYS_INLINE T boolean_as(const document_data& /*d*/, const node& n, std::false_type /*rejects*/)
+{
+    return static_cast<T>((n.flags & node_flags::is_true) != 0);
+}
+
+/// a boolean as number_integer_t, number_unsigned_t or number_float_t: type_error.302, as in basic_json
+template<typename T>
+[[noreturn]] NLOHMANN_VIEW_ALWAYS_INLINE T boolean_as(const document_data& d, const node& n, std::true_type /*rejects*/)
+{
+    throw_type_error(error_site(&d, &n), exception_id::type_mismatch, "type must be number, but is ", value_type_name(static_cast<value_t>(n.kind)));
+}
+
 /*!
@brief the number or boolean of a node converted to an arithmetic type

 As basic_json's get<T>() for arithmetic types: integers and floats are
-converted with static_cast, booleans give 0 or 1, and other types throw
-type_error.302.
+converted with static_cast, booleans give 0 or 1 (but throw type_error.302 for
+number_integer_t, number_unsigned_t and number_float_t, as basic_json does),
+and other types throw type_error.302.
 */
 template<typename T, typename BasicJsonType>
 NLOHMANN_VIEW_ALWAYS_INLINE T arithmetic_value(const document_data& d, const node& n)
@@ -10096,7 +10078,7 @@ NLOHMANN_VIEW_ALWAYS_INLINE T arithmetic_value(const document_data& d, const nod
        case value_t::number_float:
            return static_cast<T>(float_value<typename BasicJsonType::number_float_t>(d, n));
        case value_t::boolean:
-            return static_cast<T>((n.flags & node_flags::is_true) != 0);
+            return boolean_as<T>(d, n, rejects_boolean<T, BasicJsonType> {});
        case value_t::null:
        case value_t::object:
        case value_t::array:
@@ -11809,9 +11791,11 @@ class basic_json_document
        {
            // (as before: the library's adapter decides what a null stream yields)
            detail::view::append_adapter(buf, detail::input_adapter(file));
-            return;
        }
-        detail::view::append_file(buf, file);
+        else
+        {
+            detail::view::append_file(buf, file);
+        }
    }
 #endif

@@ -629,6 +629,22 @@ static json make_containers()
    return j;
 }

+/// many arrays of one number each: one-element arrays are left to the general
+/// path (CBOR and MessagePack), which reads a lone number slower than the loop
+/// for arrays of scalars would
+static json make_singles()
+{
+    json data = json::array();
+    for (std::size_t i = 0; i < 100000; ++i)
+    {
+        data.push_back(json::array({i}));
+    }
+
+    json j = json::object();
+    j["data"] = std::move(data);
+    return j;
+}
+
 /// one flat array of numbers: the scalar decoding path, which must not move
 static json make_scalars()
 {
@@ -676,6 +692,8 @@ BENCHMARK_CAPTURE(FromBinaryShape, containers / ubjson_optimized, make_container
 BENCHMARK_CAPTURE(FromBinaryShape, containers / bjdata, make_containers, binary_format::bjdata);
 BENCHMARK_CAPTURE(FromBinaryShape, containers / bson, make_containers, binary_format::bson);
 BENCHMARK_CAPTURE(FromBinaryShape, containers / bon8, make_containers, binary_format::bon8);
+BENCHMARK_CAPTURE(FromBinaryShape, singles / cbor, make_singles, binary_format::cbor);
+BENCHMARK_CAPTURE(FromBinaryShape, singles / msgpack, make_singles, binary_format::msgpack);
 // BSON names every array element, so a large array measures key generation
 // rather than scalar decoding and is left out here
 BENCHMARK_CAPTURE(FromBinaryShape, scalars / cbor, make_scalars, binary_format::cbor);
@@ -47,10 +47,6 @@ dumps is stable under exactly the same values that break operator==.
 The unit tests run the same checks on a fixed corpus (see the "BJData round-trip
 invariants" test case), so keep both in sync.

-Furthermore, it reads data with a SAX parser that recovers from every error
-and checks that the events are balanced, that reading ends, and that it
-reports an error exactly when from_bjdata() fails (see #3989).
-
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -61,7 +57,6 @@ drivers.
 */

 #include "fuzzer_common.hpp"
-#include "fuzzer-recovering_checker.hpp"

 namespace
 {
@@ -86,9 +81,6 @@ static bool is_value_stable(const json& lhs, const json& rhs)
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
-    // recover from all errors, reading from memory and from a stream
-    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::bjdata).errors == 0;
-
    std::vector<uint8_t> const vec1(data, data + size);

    // step 0: parse input without exceptions
@@ -107,9 +99,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
        // without exceptions, the same input must give the same value
        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));

-        // the recovering parser must not have reported an error either
-        assert(recovered_without_errors);
-
        try
        {
            // step 2.1: round trip without adding size annotations to container types
@@ -143,7 +132,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // parse errors are ok, because input may be random bytes
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }
    catch (const json::type_error&)
    {
@@ -154,7 +142,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // out of range errors may happen if provided sizes are excessive
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }

    // step 3: the other input adapters must read the data alike
@@ -17,10 +17,6 @@ array data, it performs the following steps:
 - j2 = from_bon8(vec)
 - assert(to_bon8(j2) == vec)

-Furthermore, it reads data with a SAX parser that recovers from every error
-and checks that the events are balanced, that reading ends, and that it
-reports an error exactly when from_bon8() fails (see #3989).
-
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -31,7 +27,6 @@ drivers.
 */

 #include "fuzzer_common.hpp"
-#include "fuzzer-recovering_checker.hpp"

 namespace
 {
@@ -49,9 +44,6 @@ struct read_bon8
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
-    // recover from all errors, reading from memory and from a stream
-    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::bon8).errors == 0;
-
    std::vector<uint8_t> const vec1(data, data + size);

    // step 0: parse input without exceptions
@@ -70,9 +62,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
        // without exceptions, the same input must give the same value
        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));

-        // the recovering parser must not have reported an error either
-        assert(recovered_without_errors);
-
        try
        {
            // step 2: round trip
@@ -94,7 +83,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // parse errors are ok, because input may be random bytes
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }
    catch (const json::type_error&)
    {
@@ -105,7 +93,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // out of range errors may happen if provided sizes are excessive
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }

    // step 3: the other input adapters must read the data alike
@@ -17,10 +17,6 @@ array data, it performs the following steps:
 - j2 = from_bson(vec)
 - assert(to_bson(j2) == vec)

-Furthermore, it reads data with a SAX parser that recovers from every error
-and checks that the events are balanced, that reading ends, and that it
-reports an error exactly when from_bson() fails (see #3989).
-
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -31,7 +27,6 @@ drivers.
 */

 #include "fuzzer_common.hpp"
-#include "fuzzer-recovering_checker.hpp"

 namespace
 {
@@ -49,9 +44,6 @@ struct read_bson
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
-    // recover from all errors, reading from memory and from a stream
-    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::bson).errors == 0;
-
    std::vector<uint8_t> const vec1(data, data + size);

    // step 0: parse input without exceptions
@@ -70,9 +62,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
        // without exceptions, the same input must give the same value
        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));

-        // the recovering parser must not have reported an error either
-        assert(recovered_without_errors);
-
        try
        {
            // step 2: round trip
@@ -94,7 +83,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // parse errors are ok, because input may be random bytes
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }
    catch (const json::type_error&)
    {
@@ -105,7 +93,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // out of range errors can occur during parsing, too
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }

    // step 3: the other input adapters must read the data alike
@@ -17,10 +17,6 @@ array data, it performs the following steps:
 - j2 = from_cbor(vec)
 - assert(to_cbor(j2) == vec)

-Furthermore, it reads data with a SAX parser that recovers from every error
-and checks that the events are balanced, that reading ends, and that it
-reports an error exactly when from_cbor() fails (see #3989).
-
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -31,7 +27,6 @@ drivers.
 */

 #include "fuzzer_common.hpp"
-#include "fuzzer-recovering_checker.hpp"

 namespace
 {
@@ -49,9 +44,6 @@ struct read_cbor
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
-    // recover from all errors, reading from memory and from a stream
-    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::cbor).errors == 0;
-
    std::vector<uint8_t> const vec1(data, data + size);

    // step 0: parse input without exceptions
@@ -70,9 +62,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
        // without exceptions, the same input must give the same value
        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));

-        // the recovering parser must not have reported an error either
-        assert(recovered_without_errors);
-
        try
        {
            // step 2: round trip
@@ -94,7 +83,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // parse errors are ok, because input may be random bytes
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }
    catch (const json::type_error&)
    {
@@ -105,7 +93,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // out of range errors can occur during parsing, too
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }

    // step 3: the other input adapters must read the data alike
@@ -24,16 +24,11 @@ array data, it performs the following steps:
 The pointer range takes the bulk fast paths, the other input adapters read byte
 by byte; see check_input_adapters().

-Furthermore, it parses data with a SAX parser that recovers from every error
-and checks that the events are balanced, that parsing ends, and that valid
-input is parsed without errors (see #3989).
-
 The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
 drivers.
 */

 #include "fuzzer_common.hpp"
-#include "fuzzer-recovering_checker.hpp"

 namespace
 {
@@ -64,13 +59,6 @@ struct accept_json
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
-    // recover from all errors, reading from memory and from a stream
-    {
-        const auto checker = check_recovering_parse(data, size, json::input_format_t::json);
-        assert(checker.events <= (4 * size) + 4);
-        assert((checker.errors == 0) == json::accept(data, data + size));
-    }
-
    // step 0: parse input without exceptions
    bool noexcept_threw = false;
    json const j_noexcept = parse_without_exceptions([&] { return json::parse(data, data + size, nullptr, false); }, noexcept_threw);
@@ -17,10 +17,6 @@ array data, it performs the following steps:
 - j2 = from_msgpack(vec)
 - assert(to_msgpack(j2) == vec)

-Furthermore, it reads data with a SAX parser that recovers from every error
-and checks that the events are balanced, that reading ends, and that it
-reports an error exactly when from_msgpack() fails (see #3989).
-
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -31,7 +27,6 @@ drivers.
 */

 #include "fuzzer_common.hpp"
-#include "fuzzer-recovering_checker.hpp"

 namespace
 {
@@ -49,9 +44,6 @@ struct read_msgpack
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
-    // recover from all errors, reading from memory and from a stream
-    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::msgpack).errors == 0;
-
    std::vector<uint8_t> const vec1(data, data + size);

    // step 0: parse input without exceptions
@@ -70,9 +62,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
        // without exceptions, the same input must give the same value
        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));

-        // the recovering parser must not have reported an error either
-        assert(recovered_without_errors);
-
        try
        {
            // step 2: round trip
@@ -94,7 +83,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // parse errors are ok, because input may be random bytes
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }
    catch (const json::type_error&)
    {
@@ -105,7 +93,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // out of range errors may happen if provided sizes are excessive
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }

    // step 3: the other input adapters must read the data alike
@@ -26,10 +26,6 @@ array data, it performs the following steps:
 The unit tests run the same checks on a fixed corpus (see the "UBJSON round-trip
 invariants" test case), so keep both in sync.

-Furthermore, it reads data with a SAX parser that recovers from every error
-and checks that the events are balanced, that reading ends, and that it
-reports an error exactly when from_ubjson() fails (see #3989).
-
 Finally, it reads the data from a stream, a non-contiguous iterator range, and
 a FILE*, which read byte by byte, and checks that each gives the same value or
 error (id, message, byte position) as the pointer range, which takes the bulk
@@ -40,7 +36,6 @@ drivers.
 */

 #include "fuzzer_common.hpp"
-#include "fuzzer-recovering_checker.hpp"

 namespace
 {
@@ -58,9 +53,6 @@ struct read_ubjson
 // see http://llvm.org/docs/LibFuzzer.html
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
-    // recover from all errors, reading from memory and from a stream
-    const bool recovered_without_errors = check_recovering_parse(data, size, json::input_format_t::ubjson).errors == 0;
-
    std::vector<uint8_t> const vec1(data, data + size);

    // step 0: parse input without exceptions
@@ -79,9 +71,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
        // without exceptions, the same input must give the same value
        assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));

-        // the recovering parser must not have reported an error either
-        assert(recovered_without_errors);
-
        try
        {
            // step 2.1: round trip without adding size annotations to container types
@@ -113,7 +102,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // parse errors are ok, because input may be random bytes
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }
    catch (const json::type_error&)
    {
@@ -124,7 +112,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
    {
        // out of range errors may happen if provided sizes are excessive
        assert(parsed || noexcept_threw || j_noexcept.is_discarded());
-        assert(parsed || !recovered_without_errors);
    }

    // step 3: the other input adapters must read the data alike
@@ -1,154 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#pragma once
-
-#include <cassert>
-#include <cstddef>
-#include <cstdint>
-#include <sstream>
-#include <string>
-#include <vector>
-#include <nlohmann/json.hpp>
-
-namespace
-{
-// a SAX parser that recovers from every error and checks that the events are
-// balanced and that every key is followed by exactly one value
-class recovering_checker : public nlohmann::json_sax<nlohmann::json>
-{
-  public:
-    bool null() override
-    {
-        return value();
-    }
-
-    bool boolean(bool /*val*/) override
-    {
-        return value();
-    }
-
-    bool number_integer(number_integer_t /*val*/) override
-    {
-        return value();
-    }
-
-    bool number_unsigned(number_unsigned_t /*val*/) override
-    {
-        return value();
-    }
-
-    bool number_float(number_float_t /*val*/, const string_t& /*s*/) override
-    {
-        return value();
-    }
-
-    bool string(string_t& /*val*/) override
-    {
-        return value();
-    }
-
-    bool binary(binary_t& /*val*/) override
-    {
-        return value();
-    }
-
-    bool start_object(std::size_t /*elements*/) override
-    {
-        value();
-        stack.push_back('o');
-        return true;
-    }
-
-    bool key(string_t& /*val*/) override
-    {
-        ++events;
-        assert(!stack.empty() && stack.back() == 'o');
-        stack.back() = 'v';
-        return true;
-    }
-
-    bool end_object() override
-    {
-        ++events;
-        assert(!stack.empty() && stack.back() == 'o');
-        stack.pop_back();
-        return true;
-    }
-
-    bool start_array(std::size_t /*elements*/) override
-    {
-        value();
-        stack.push_back('a');
-        return true;
-    }
-
-    bool end_array() override
-    {
-        ++events;
-        assert(!stack.empty() && stack.back() == 'a');
-        stack.pop_back();
-        return true;
-    }
-
-    bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const nlohmann::detail::exception& /*ex*/) override
-    {
-        ++errors;
-        return true;
-    }
-
-    bool complete() const
-    {
-        return stack.empty();
-    }
-
-    std::size_t events = 0;
-    std::size_t errors = 0;
-
-  private:
-    bool value()
-    {
-        ++events;
-        if (!stack.empty())
-        {
-            // an array element, or the value of a key
-            assert(stack.back() != 'o');
-            if (stack.back() == 'v')
-            {
-                stack.back() = 'o';
-            }
-        }
-        return true;
-    }
-
-    // 'a' for an array, 'o' for an object that expects a key, 'v' for an
-    // object that expects the value of a key
-    std::vector<char> stack {}; // NOLINT(readability-redundant-member-init)
-};
-
-/// parses @a data with a recovering_checker from memory and from a stream,
-/// checks that both see the same, that the events are balanced, and that the
-/// number of errors is bounded, and returns the checker (see #3989)
-inline recovering_checker check_recovering_parse(const std::uint8_t* data, const std::size_t size, const nlohmann::json::input_format_t format)
-{
-    recovering_checker checker;
-    const bool ok = nlohmann::json::sax_parse(data, data + size, &checker, format);
-    assert(checker.complete());
-    assert(checker.errors <= size + 1);
-    assert(ok == (checker.errors == 0));
-
-    std::istringstream stream(std::string(reinterpret_cast<const char*>(data), size));
-    recovering_checker stream_checker;
-    assert(nlohmann::json::sax_parse(stream, &stream_checker, format) == ok);
-    assert(stream_checker.complete());
-    assert(stream_checker.events == checker.events);
-    assert(stream_checker.errors == checker.errors);
-
-    return checker;
-}
-} // namespace
@@ -131,13 +131,11 @@ struct SaxEventLogger : public nlohmann::json_sax<nlohmann::json>
    {
        errored = true;
        events.push_back("parse_error(" + std::to_string(position) + ")");
-        return recover;
+        return false;
    }

    std::vector<std::string> events {}; // NOLINT(readability-redundant-member-init)
    bool errored = false;
-    /// whether parse_error() asks the parser to recover from the error (see #3989)
-    bool recover = false;
 };

 struct SaxEventLoggerExitAfterStartObject : public SaxEventLogger
@@ -97,3 +97,23 @@ TEST_CASE("CBOR")
        }
    }
 }
+
+TEST_CASE("MessagePack")
+{
+    SECTION("parse errors")
+    {
+        SECTION("array/map size equal to the unknown-size sentinel")
+        {
+            // on 32-bit platforms an array 32/map 32 length of 0xFFFFFFFF aliases unknown_size()
+            std::vector<uint8_t> const varr = {0xDD, 0xFF, 0xFF, 0xFF, 0xFF};
+            std::vector<uint8_t> const vmap = {0xDF, 0xFF, 0xFF, 0xFF, 0xFF};
+
+            json _;
+            CHECK_THROWS_WITH_AS(_ = json::from_msgpack(varr), "[json.exception.out_of_range.408] syntax error while parsing MessagePack size: excessive array size", json::out_of_range&);
+            CHECK(json::from_msgpack(varr, true, false).is_discarded());
+
+            CHECK_THROWS_WITH_AS(_ = json::from_msgpack(vmap), "[json.exception.out_of_range.408] syntax error while parsing MessagePack size: excessive map size", json::out_of_range&);
+            CHECK(json::from_msgpack(vmap, true, false).is_discarded());
+        }
+    }
+}
@@ -12,6 +12,8 @@
 #include <nlohmann/json.hpp>
 using nlohmann::json;

+#include <functional>
+#include <limits>
 #include <valarray>
 #if JSON_HAS_RANGES
    #include <ranges>
@@ -790,7 +792,7 @@ TEST_CASE("a failed allocation leaves the value unchanged")
 #if JSON_HAS_RANGES && !defined(__MINGW32__)
        const std::vector<int> numbers = {1, 2};
        next_construct_fails = true;
-        CHECK_THROWS_AS(nlohmann::to_json(j, numbers | std::views::filter([](int /*unused*/)
+        CHECK_THROWS_AS(nlohmann::to_json(j, numbers | std::views::filter([](int /*unused*/) noexcept
        {
            return true;
        })), std::bad_alloc&);
@@ -804,3 +806,405 @@ TEST_CASE("a failed allocation leaves the value unchanged")
 #endif
 }
 #endif
+
+// the no-exceptions CI job has no std::bad_alloc to catch; with iterator
+// debugging (MSVC STL debug builds) containers allocate inside noexcept
+// functions, so failing an allocation there terminates the program
+#if !defined(JSON_NOEXCEPTION) && !(defined(_ITERATOR_DEBUG_LEVEL) && _ITERATOR_DEBUG_LEVEL > 0)
+namespace
+{
+// whether every child of j names j as its parent (always true without
+// JSON_DIAGNOSTICS, where no parents are stored)
+template<class BasicJsonType>
+bool children_name_their_parent(const BasicJsonType& j)
+{
+#if JSON_DIAGNOSTICS
+    if (j.is_array())
+    {
+        for (const auto& element : *j.m_data.m_value.array)
+        {
+            if (element.m_parent != &j)
+            {
+                return false;
+            }
+        }
+    }
+    else if (j.is_object())
+    {
+        for (const auto& element : *j.m_data.m_value.object)
+        {
+            if (element.second.m_parent != &j)
+            {
+                return false;
+            }
+        }
+    }
+#else
+    static_cast<void>(j);
+#endif
+    return true;
+}
+
+enum class guarantee
+{
+    basic, // the value stays valid and keeps its type
+    strong // the value is unchanged
+};
+
+// Runs op on a fresh value make() with the 0th, 1st, 2nd, ... allocation made
+// by the library failing in turn, until op completes. Every failed attempt
+// must have thrown std::bad_alloc and left the value valid, with all parent
+// pointers intact (copying a value asserts the invariant), and for the strong
+// guarantee exactly as it was.
+template<class BasicJsonType>
+void check_exception_guarantee(guarantee g,
+                               const std::function<BasicJsonType()>& make,
+                               const std::function<void(BasicJsonType&)>& op)
+{
+    fail_at_alloc_call = -1;
+
+    bool completed = false;
+    std::size_t failures = 0;
+    for (std::size_t n = 0; !completed; ++n)
+    {
+        CAPTURE(n)
+        REQUIRE(n < 1000);
+
+        BasicJsonType j = make();
+        const std::string before = j.dump();
+        const auto type_before = j.type();
+
+        alloc_call_count = 0;
+        fail_at_alloc_call = static_cast<long>(n);
+        try
+        {
+            op(j);
+            completed = true;
+        }
+        catch (const std::bad_alloc&)
+        {
+            ++failures;
+        }
+        fail_at_alloc_call = -1;
+
+        if (!completed)
+        {
+            CHECK((j.type() == type_before));
+            CHECK(children_name_their_parent(j));
+            const BasicJsonType copy(j); // NOLINT(performance-unnecessary-copy-initialization): the copy is the point, it allocates
+            CHECK(copy.dump() == j.dump());
+            if (g == guarantee::strong)
+            {
+                CHECK(j.dump() == before);
+            }
+        }
+    }
+
+    // the operation allocates, so at least one attempt must have failed
+    CHECK(failures > 0);
+}
+
+template<class BasicJsonType>
+void check_insert_exception_guarantees()
+{
+    using json_t = BasicJsonType;
+    using make_t = std::function<json_t()>;
+
+    // strings of this length do not fit into the small string buffer, so
+    // copying them allocates
+    const json_t val = std::string(64, 'x');
+    const json_t source = json_t::array({std::string(64, 'p'), std::string(64, 'q'), std::string(64, 'r')});
+
+    for (const bool spare_capacity :
+            {
+                false, true
+            })
+    {
+        CAPTURE(spare_capacity)
+
+        // [ "aaa...", "bbb...", "ccc..." ], with a spare slot if requested
+        const make_t make = [spare_capacity]()
+        {
+            json_t j = json_t::array({std::string(64, 'a'), std::string(64, 'b'), std::string(64, 'c')});
+            if (spare_capacity)
+            {
+                j.push_back(std::string(64, 'd'));
+                j.erase(3);
+            }
+            return json_t(std::move(j));
+        };
+
+        for (const bool at_end :
+                {
+                    false, true
+                })
+        {
+            CAPTURE(at_end)
+
+            SECTION("insert(pos, const basic_json&)")
+            {
+                check_exception_guarantee<json_t>(guarantee::strong, make, [&](json_t& j)
+                {
+                    j.insert(at_end ? j.end() : j.begin() + 1, val);
+                });
+            }
+
+            SECTION("insert(pos, basic_json&&)")
+            {
+                check_exception_guarantee<json_t>(guarantee::strong, make, [&](json_t& j)
+                {
+                    j.insert(at_end ? j.end() : j.begin() + 1, json_t(val));
+                });
+            }
+
+            SECTION("insert(pos, size_type, const basic_json&)")
+            {
+                check_exception_guarantee<json_t>(guarantee::basic, make, [&](json_t& j)
+                {
+                    j.insert(at_end ? j.end() : j.begin() + 1, 3, val);
+                });
+            }
+
+            SECTION("insert(pos, const_iterator, const_iterator)")
+            {
+                check_exception_guarantee<json_t>(guarantee::basic, make, [&](json_t& j)
+                {
+                    j.insert(at_end ? j.end() : j.begin() + 1, source.begin(), source.end());
+                });
+            }
+
+            SECTION("insert(pos, initializer_list_t)")
+            {
+                check_exception_guarantee<json_t>(guarantee::basic, make, [&](json_t& j)
+                {
+                    j.insert(at_end ? j.end() : j.begin() + 1, {val, val});
+                });
+            }
+        }
+    }
+
+    SECTION("insert(const_iterator, const_iterator) for objects")
+    {
+        const json_t members = {{"m", std::string(64, 'm')}, {"n", std::string(64, 'n')}, {"o", std::string(64, 'o')}};
+
+        SECTION("no member exists yet")
+        {
+            check_exception_guarantee<json_t>(guarantee::basic, []()
+            {
+                return json_t({{"a", 1}});
+            }, [&](json_t& j)
+            {
+                j.insert(members.begin(), members.end());
+            });
+        }
+
+        SECTION("some members exist already")
+        {
+            check_exception_guarantee<json_t>(guarantee::basic, []()
+            {
+                return json_t({{"a", 1}, {"n", std::string(64, 'x')}});
+            }, [&](json_t& j)
+            {
+                j.insert(members.begin(), members.end());
+            });
+        }
+    }
+}
+} // namespace
+
+TEST_CASE("insert() provides its documented exception guarantees (#5986)")
+{
+    SECTION("std::map-backed object_t")
+    {
+        check_insert_exception_guarantees<nlohmann::json::with_allocator_t<nth_alloc_fails_allocator>>();
+    }
+
+    SECTION("ordered_map-backed object_t")
+    {
+        check_insert_exception_guarantees<nlohmann::ordered_json::with_allocator_t<nth_alloc_fails_allocator>>();
+    }
+}
+#endif
+
+#if !defined(JSON_NOEXCEPTION)
+namespace
+{
+// the allocation numbered sweep_fail_at (counted from 1) throws; 0 never fails
+std::size_t sweep_allocations = 0;
+std::size_t sweep_fail_at = 0;
+std::ptrdiff_t sweep_live = 0;
+
+template<class T>
+struct sweep_allocator
+{
+    using value_type = T;
+    // GCC 4.8's std::map takes these from the allocator instead of from
+    // std::allocator_traits
+    using pointer = T*;
+    using const_pointer = const T*;
+    using reference = T&;
+    using const_reference = const T&;
+    using size_type = std::size_t;
+    using difference_type = std::ptrdiff_t;
+
+    sweep_allocator() = default;
+    template<class U> sweep_allocator(const sweep_allocator<U>& /*unused*/) noexcept {}
+
+    T* allocate(std::size_t n)
+    {
+        if (sweep_fail_at != 0 && ++sweep_allocations == sweep_fail_at)
+        {
+            throw std::bad_alloc();
+        }
+        ++sweep_live;
+        return std::allocator<T>().allocate(n);
+    }
+
+    void deallocate(T* p, std::size_t n) noexcept
+    {
+        --sweep_live;
+        std::allocator<T>().deallocate(p, n);
+    }
+
+    // GCC 4.8's std::map calls these on the allocator directly instead of
+    // going through std::allocator_traits
+    std::size_t max_size() const noexcept
+    {
+        return (std::numeric_limits<std::size_t>::max)() / sizeof(T);
+    }
+
+    template<class U, class... Args>
+    void construct(U* p, Args&& ... args) noexcept(noexcept(::new (static_cast<void*>(p)) U(std::forward<Args>(args)...)))
+    {
+        ::new (static_cast<void*>(p)) U(std::forward<Args>(args)...);
+    }
+
+    template<class U>
+    void destroy(U* p) noexcept
+    {
+        static_cast<void>(p); // unused for trivially destructible types
+        p->~U();
+    }
+
+    template <class U>
+    struct rebind
+    {
+        using other = sweep_allocator<U>;
+    };
+
+    bool operator==(const sweep_allocator& /*unused*/) const noexcept
+    {
+        return true;
+    }
+    bool operator!=(const sweep_allocator& /*unused*/) const noexcept
+    {
+        return false;
+    }
+};
+
+// run make() with the allocation numbered k failing, for k = 1, 2, ...: every
+// failure must be a std::bad_alloc and must not leave anything behind, and
+// the first k without a failure must yield the value made without failures
+template<class BasicJsonType, class Make>
+void sweep_allocations_of(const Make& make)
+{
+    sweep_fail_at = 0;
+    const BasicJsonType expected = make();
+    const std::ptrdiff_t live_before = sweep_live;
+
+    std::size_t failures = 0;
+    for (std::size_t k = 1; k < 10000; ++k)
+    {
+        sweep_allocations = 0;
+        sweep_fail_at = k;
+        try
+        {
+            const BasicJsonType result = make();
+            sweep_fail_at = 0;
+            CHECK(result == expected);
+            break;
+        }
+        catch (const std::bad_alloc&)
+        {
+            sweep_fail_at = 0;
+            ++failures;
+        }
+        CHECK(sweep_live == live_before);
+    }
+    sweep_fail_at = 0;
+    CHECK(failures > 10);
+    CHECK(sweep_live == live_before);
+}
+} // namespace
+
+TEST_CASE("parse() survives a failing allocation at every point (#5985)")
+{
+    // strings beyond the small string buffer, nested objects and arrays
+    const std::string text = R"({"a":"a long string that does not fit into the small string buffer1","b":[1,2,[3,{"k":"another string that is longer than any small string buffer"}]],"c":{"x":1,"y":{"z":[]},"w":"yet another string that does not fit into a small buffer"},"d":1,"b":[[],{}]})";
+
+    using sweep_json = nlohmann::json::with_allocator_t<sweep_allocator>;
+    using sweep_ordered_json = nlohmann::ordered_json::with_allocator_t<sweep_allocator>;
+
+    SECTION("json")
+    {
+        sweep_allocations_of<sweep_json>([&]
+        {
+            return sweep_json::parse(text);
+        });
+    }
+
+    SECTION("ordered_json")
+    {
+        sweep_allocations_of<sweep_ordered_json>([&]
+        {
+            return sweep_ordered_json::parse(text);
+        });
+    }
+
+    // With iterator debugging (MSVC STL debug builds, also used by clang-cl),
+    // containers allocate a debug proxy through the allocator inside their
+    // noexcept default and move constructors, so failing that allocation
+    // terminates the program instead of throwing std::bad_alloc. Nothing to
+    // check there.
+#if !(defined(_ITERATOR_DEBUG_LEVEL) && _ITERATOR_DEBUG_LEVEL > 0)
+    // Clang 3.4 and 3.5 leak memory when an element constructor throws
+    // inside libstdc++'s containers (a std::map copy, a std::vector
+    // reallocation), without any json value involved.
+#if !(defined(__clang__) && !defined(__apple_build_version__) && __clang_major__ == 3 && __clang_minor__ < 6)
+    SECTION("parser callback")
+    {
+        const auto keep_all = [](int /*depth*/, sweep_json::parse_event_t /*event*/, sweep_json& /*parsed*/) noexcept
+        {
+            return true;
+        };
+        sweep_allocations_of<sweep_json>([&]
+        {
+            return sweep_json::parse(text, keep_all);
+        });
+
+        const auto drop_d = [](int /*depth*/, sweep_json::parse_event_t event, sweep_json & parsed)
+        {
+            return event != sweep_json::parse_event_t::key || parsed != "d";
+        };
+        sweep_allocations_of<sweep_json>([&]
+        {
+            return sweep_json::parse(text, drop_d);
+        });
+    }
+
+    SECTION("sax_parse into an existing value")
+    {
+        // a failed parse leaves the target in a state that is safe to destroy
+        using sax_t = nlohmann::detail::json_sax_dom_parser<sweep_json, nlohmann::detail::iterator_input_adapter<const char*>>;
+        sweep_allocations_of<sweep_json>([&]() -> sweep_json
+        {
+            sweep_json value;
+            sax_t sax(value, false);
+            static_cast<void>(sweep_json::sax_parse(text, &sax));
+            return value;
+        });
+    }
+#endif
+#endif
+}
+#endif
@@ -10,6 +10,7 @@
 #include "doctest_compatibility.h"

 #include <nlohmann/json.hpp>
+#include <nlohmann/json_view.hpp>

 #include <cstdint>
 #include <string>
@@ -432,46 +433,6 @@ TEST_CASE("alternative string type")
        CHECK(j2.dump() == R"({"/foo/0":"bar","/foo/1":"baz"})");
    }

-    SECTION("error recovery")
-    {
-        // a SAX parser that recovers from every error (see #3989)
-        struct recovering_parser : nlohmann::detail::json_sax_dom_parser<alt_json>
-        {
-            explicit recovering_parser(alt_json& j)
-                : nlohmann::detail::json_sax_dom_parser<alt_json>(j, false)
-            {}
-
-            // sax_parse() calls the SAX parser's own parse_error(), so hiding
-            // the one of the base class is what recovering takes
-            // NOLINTNEXTLINE(bugprone-derived-method-shadowing-base-method)
-            bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const nlohmann::detail::exception& /*unused*/)
-            {
-                ++errors;
-                return true;
-            }
-
-            std::size_t errors = 0;
-        };
-
-        alt_json j;
-        recovering_parser sax(j);
-        // not inside CHECK(): MSVC reads the escape in a stringized raw string
-        const std::string input = R"([1., "a\qb", tru, {"k" 2}])";
-        CHECK(!alt_json::sax_parse(input, &sax));
-        CHECK(sax.errors == 4);
-        CHECK(j.dump() == R"([1,"aqb",null,{"k":2}])");
-
-        // a UBJSON high-precision number, a CBOR key that is not a string
-        alt_json u;
-        recovering_parser ubjson_sax(u);
-        CHECK(!alt_json::sax_parse(std::vector<std::uint8_t> {'[', 'H', 'i', 2, '1', '.', ']'}, &ubjson_sax, alt_json::input_format_t::ubjson));
-        CHECK(u.dump() == "[1]");
-        alt_json c;
-        recovering_parser cbor_sax(c);
-        CHECK(!alt_json::sax_parse(std::vector<std::uint8_t> {0xA2, 0x01, 0x02, 0x61, 'a', 0x03}, &cbor_sax, alt_json::input_format_t::cbor));
-        CHECK(c.dump() == R"({"a":3})");
-    }
-
    SECTION("conversion between basic_json specializations (#2649)")
    {
        // explicit conversions are always possible
@@ -523,4 +484,56 @@ TEST_CASE("alternative string type")
    }
 }

+TEST_CASE("alternative string type with json_view")
+{
+    // regression test for #5994: basic_json_view::dump() called
+    // StringType::capacity(), which alt_string (and the documented StringType
+    // requirements) do not provide
+    using alt_document = nlohmann::basic_json_document<alt_json, nlohmann::view_mode::read_only>;
+    using alt_editable_document = nlohmann::basic_json_document<alt_json, nlohmann::view_mode::editable>;
+
+    const char* text = R"({"a":[1,"x\u00e4"],"b":{"c":true,"d":null},"e":2.5})";
+    const alt_json j = alt_json::parse(text);
+
+    SECTION("read-only document")
+    {
+        const alt_document d = alt_document::parse(text);
+        CHECK(d.root().dump() == j.dump());
+        CHECK(d.root().dump(2) == j.dump(2));
+        CHECK(d.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
+        CHECK(d.root().materialize() == j);
+        CHECK(d.root().contains(alt_string("b")));
+        CHECK(d.root()[alt_string("b")][alt_string("c")].dump() == "true");
+    }
+
+    SECTION("long output")
+    {
+        // more than one growth step of the output buffer
+        alt_json big = alt_json::array();
+        for (int i = 0; i < 20000; ++i)
+        {
+            big.push_back(alt_json::parse(text));
+        }
+        const alt_string big_text = big.dump();
+        const alt_document d = alt_document::parse(big_text);
+        CHECK(d.root().dump() == big_text);
+        CHECK(d.root().dump(4) == big.dump(4));
+    }
+
+    SECTION("editable document")
+    {
+        alt_editable_document d = alt_editable_document::parse(text);
+        d.set(d.root(), "f", "new");
+        d.push_back(d.root()[alt_string("a")], 3);
+        alt_json expected = j;
+        expected["f"] = "new";
+        expected["a"].push_back(3);
+        CHECK(d.root().materialize() == expected);
+        CHECK(alt_json::parse(d.root().dump()) == expected);
+
+        const alt_editable_document loaded = alt_editable_document::load(d.save());
+        CHECK(loaded.root().materialize() == expected);
+    }
+}
+
 DOCTEST_CLANG_SUPPRESS_WARNING_POP
@@ -14,7 +14,9 @@ using nlohmann::json;
 #include <array>
 #include <cstdint>
 #include <limits>
+#include <memory>
 #include <sstream>
+#include <stdexcept>
 #include <string>
 #include <vector>

@@ -48,6 +50,14 @@ std::vector<json> test_values()
        large_payloads.push_back(json::binary(std::vector<std::uint8_t>(static_cast<std::size_t>(100 * i), static_cast<std::uint8_t>(i))));
    }

+    // several times vector_sink_window characters in every format: the vector
+    // sink makes the capacity it grows to writable a window at a time
+    json many_windows = json::array();
+    for (std::uint64_t i = 0; i < 30000; ++i)
+    {
+        many_windows.push_back((i * 0x9E3779B97F4A7C15u) >> 1u);
+    }
+
    return
    {
        json(nullptr), json(true), json(false),
@@ -59,7 +69,7 @@ std::vector<json> test_values()
        json::array(), json::object(),
        json::array({1, 2, 3}), json({{"a", 1}, {"b", nullptr}}),
        json({{"nested", {{"deep", json::array({1, "two", 3.0, nullptr})}}}}),
-        big_array, big_object, large_payloads,
+        big_array, big_object, large_payloads, many_windows,
        json::binary(std::vector<std::uint8_t>(5000, 0x42))
    };
 }
@@ -767,3 +777,69 @@ TEST_CASE("a write that throws leaves the same bytes in every kind of output")
    }
 }
 #endif
+
+#if !defined(JSON_NOEXCEPTION)
+namespace
+{
+
+// an adapter whose every write fails
+class failing_adapter : public nlohmann::detail::output_adapter_protocol<char>
+{
+  public:
+    [[noreturn]] void write_character(char /*c*/) override
+    {
+        throw std::runtime_error("write failed");
+    }
+
+    [[noreturn]] void write_characters(const char* /*s*/, std::size_t /*length*/) override
+    {
+        throw std::runtime_error("write failed");
+    }
+};
+
+} // namespace
+#endif
+
+TEST_CASE("output adapters")
+{
+    SECTION("writing a single character")
+    {
+        // the writers pass whole buffers on, but an adapter takes single
+        // characters as well
+        std::vector<char> as_vector;
+        nlohmann::detail::output_vector_adapter<char> vector_adapter(as_vector);
+        vector_adapter.write_character('a');
+        vector_adapter.write_character('b');
+        CHECK(as_vector == std::vector<char>({'a', 'b'}));
+
+        std::ostringstream as_stream;
+        nlohmann::detail::output_stream_adapter<char> stream_adapter(as_stream);
+        stream_adapter.write_character('c');
+        stream_adapter.write_character('d');
+        CHECK(as_stream.str() == "cd");
+
+        std::string as_string;
+        nlohmann::detail::output_string_adapter<char> string_adapter(as_string);
+        string_adapter.write_character('e');
+        string_adapter.write_character('f');
+        CHECK(as_string == "ef");
+    }
+
+#if !defined(JSON_NOEXCEPTION)
+    SECTION("a sink that is destroyed with characters left over")
+    {
+        // the destructor passes the pending characters on, as a write that
+        // threw leaves them there; the adapter failing then must not escape
+        {
+            nlohmann::detail::output_adapter_sink<char> sink(std::make_shared<failing_adapter>());
+            sink.write_character('x');
+        }
+
+        // while flush() reports the failure
+        nlohmann::detail::output_adapter_sink<char> sink(std::make_shared<failing_adapter>());
+        sink.write_character('x');
+        CHECK_THROWS_AS(sink.flush(), std::runtime_error&);
+        // (the character counts as written, so there is nothing left for the destructor)
+    }
+#endif
+}
@@ -78,23 +78,25 @@ TEST_CASE("BJData")
 {
    SECTION("binary_reader BJData lookup tables")
    {
-        // both lookups are static member functions
+        // bjd_type_name() is static; is_valid_optimized_type() needs a BJData reader
        std::vector<std::uint8_t> const data;
        using reader_t = nlohmann::detail::binary_reader<json, decltype(nlohmann::detail::input_adapter(data))>;

-        // the excluded optimized-type markers must match binary_writer's
-        // is_bjdata_excluded_type_marker(), which encodes the same 8 markers
+        // the markers BJData excludes as optimized types must match
+        // binary_writer's is_bjdata_excluded_type_marker(), which encodes the
+        // same 8 markers
+        const reader_t reader(nlohmann::detail::input_adapter(data), json::input_format_t::bjdata);
        for (const char marker :
-                {'[', '{', 'S', 'H', 'T', 'F', 'N', 'Z'
+                {'[', '{', 'S', 'H', 'T', 'F', 'N', 'Z', 'x'
                })
        {
-            CHECK(reader_t::is_bjd_excluded_optimized_type(static_cast<unsigned char>(marker)));
+            CHECK(!reader.is_valid_optimized_type(static_cast<unsigned char>(marker)));
        }
        for (const char marker :
-                {'U', 'i', 'u', 'I', 'm', 'l', 'M', 'L', 'd', 'D', 'C', 'B', 'x'
+                {'U', 'i', 'u', 'I', 'm', 'l', 'M', 'L', 'd', 'D', 'C', 'B', 'h'
                })
        {
-            CHECK(!reader_t::is_bjd_excluded_optimized_type(static_cast<unsigned char>(marker)));
+            CHECK(reader.is_valid_optimized_type(static_cast<unsigned char>(marker)));
        }

        // every dtype marker must round-trip to its ND-array type name
@@ -2312,6 +2314,23 @@ TEST_CASE("BJData")
            CHECK_FALSE(json::sax_parse(v, &scp, json::input_format_t::bjdata));
        }

+        SECTION("every event of an ndarray of chars")
+        {
+            // the elements of an ndarray of 'C' are read one by one
+            std::vector<uint8_t> const v = {'[', '$', 'C', '#', '[', '$', 'U', '#', 'U', 2, 2, 2, 'a', 'b', 'c', 'd'};
+            // start_object, key, string, key, start_array, 2 numbers, end_array,
+            // key, start_array, 4 chars, end_array, end_object
+            constexpr int events = 16;
+            for (int allowed = 0; allowed < events; ++allowed)
+            {
+                CAPTURE(allowed)
+                SaxCountdown scp(allowed);
+                CHECK_FALSE(json::sax_parse(v, &scp, json::input_format_t::bjdata));
+            }
+            SaxCountdown scp(events);
+            CHECK(json::sax_parse(v, &scp, json::input_format_t::bjdata));
+        }
+
        SECTION("start_array() in ndarray _ArrayData_")
        {
            std::vector<uint8_t> const v = {'[', '$', 'U', '#', '[', 'i', 2, 'i', 3, ']', 6, 5, 4, 3, 2, 1};
@@ -3095,6 +3114,15 @@ TEST_CASE("BJData")
                json _;
                CHECK_THROWS_WITH(_ = json::from_bjdata(v), "[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing BJData char: byte after 'C' must be in range 0x00..0x7F; last byte: 0x82");
            }
+
+            SECTION("ndarray of chars cut off by the end of the input")
+            {
+                // 2x2 chars announced, three present
+                std::vector<uint8_t> const v = {'[', '$', 'C', '#', '[', '$', 'U', '#', 'U', 2, 2, 2, 'a', 'b', 'c'};
+                json _;
+                CHECK_THROWS_WITH_AS(_ = json::from_bjdata(v), "[json.exception.parse_error.110] parse error at byte 16: syntax error while parsing BJData char: unexpected end of input", json::parse_error&);
+                CHECK(json::from_bjdata(v, true, false).is_discarded());
+            }
        }

        SECTION("byte")
@@ -3211,14 +3239,34 @@ TEST_CASE("BJData")
 #endif
                CHECK(json::from_bjdata(vM, true, false).is_discarded());

-#if SIZE_MAX != 0xffffffff
-                CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vMX), "[json.exception.out_of_range.408] syntax error while parsing BJData size: excessive ndarray size caused overflow", json::out_of_range&);
-#else
+                // the first dimension is 2^64-1, which is rejected as a count (see below)
                CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vMX), "[json.exception.out_of_range.408] syntax error while parsing BJData size: integer value overflow", json::out_of_range&);
-#endif
                CHECK(json::from_bjdata(vMX, true, false).is_discarded());
            }

+            SECTION("optimized array: count equal to SIZE_MAX")
+            {
+                // the reader marks a container without a count by SIZE_MAX, so
+                // a count of that value must not be read as "no count"
+                // (it used to parse as [1])
+                json _;
+#if SIZE_MAX != 0xffffffff
+                std::vector<uint8_t> const vM = {'[', '#', 'M', 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 'i', 0x01, ']'};
+                CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vM), "[json.exception.out_of_range.408] syntax error while parsing BJData size: integer value overflow", json::out_of_range&);
+                CHECK(json::from_bjdata(vM, true, false).is_discarded());
+                // one less is an ordinary excessive count
+                std::vector<uint8_t> const vM1 = {'[', '#', 'M', 0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 'i', 0x01, ']'};
+                CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vM1), "[json.exception.out_of_range.408] excessive array size: 18446744073709551614", json::out_of_range&);
+#else
+                std::vector<uint8_t> const vm = {'[', '#', 'm', 0xFF, 0xFF, 0xFF, 0xFF, 'i', 0x01, ']'};
+                CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vm), "[json.exception.out_of_range.408] syntax error while parsing BJData size: integer value overflow", json::out_of_range&);
+                CHECK(json::from_bjdata(vm, true, false).is_discarded());
+                std::vector<uint8_t> const vL = {'[', '#', 'L', 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 'i', 0x01, ']'};
+                CHECK_THROWS_WITH_AS(_ = json::from_bjdata(vL), "[json.exception.out_of_range.408] syntax error while parsing BJData size: integer value overflow", json::out_of_range&);
+                CHECK(json::from_bjdata(vL, true, false).is_discarded());
+#endif
+            }
+
            SECTION("optimized array: integer value overflow")
            {
 #if SIZE_MAX == 0xffffffff
@@ -329,6 +329,9 @@ TEST_CASE("BON8")
            check_bon8({false, nullptr, true}, {0x83, 0xF8, 0xFA, 0xF9});
            check_bon8({false, nullptr, true, 1.0}, {0x84, 0xF8, 0xFA, 0xF9, 0xFD});
            check_bon8({false, nullptr, true, 1.0, json::array(), 0.0}, {0x85, 0xF8, 0xFA, 0xF9, 0xFD, 0x80, 0xFC, 0xFE});
+            // an array that starts with a number: -1, 0, and 1 have bytes of their own
+            check_bon8({-1.0, 0.0, 1.0}, {0x83, 0xFB, 0xFC, 0xFD});
+            check_bon8({1.0, -1.0, -0.0}, {0x83, 0xFD, 0xFB, 0x8E, 0x80, 0x00, 0x00, 0x00});
            check_bon8({{{1}}}, {0x81, 0x81, 0x81, 0x91});
            check_bon8({{{"foo"}}}, {0x81, 0x81, 0x81, 'f', 'o', 'o', 0xFF});
            check_bon8({{{""}}}, {0x81, 0x81, 0x81, 0xFF});
@@ -82,8 +82,20 @@ class huge_string_t : public std::string
        return result;
    }

+    // returns a copy of @a s whose size() pretends to be @a n
+    static huge_string_t as_size(const std::string& s, const size_type n)
+    {
+        huge_string_t result(s);
+        result.fake_size = n;
+        return result;
+    }
+
    size_type size() const noexcept
    {
+        if (fake_size != 0)
+        {
+            return fake_size;
+        }
        if (pretend_huge)
        {
            // one byte more than the BSON length field can represent
@@ -94,6 +106,7 @@ class huge_string_t : public std::string

  private:
    bool pretend_huge = false;
+    size_type fake_size = 0;
 };

 using huge_string_json = nlohmann::json::with_string_t<huge_string_t>;
@@ -268,6 +281,17 @@ TEST_CASE("BSON")
            CHECK_THROWS_WITH_AS(huge_string_json::to_bson(j), "[json.exception.out_of_range.412] BSON length 2147483661 exceeds maximum of 2147483647", huge_string_json::out_of_range&);
        }

+        SECTION("an array element that no longer fits the document")
+        {
+            // the string fits the length field, but not the document that
+            // holds it; nothing of it is written
+            const auto limit = static_cast<std::string::size_type>((std::numeric_limits<std::int32_t>::max)());
+            huge_string_json j;
+            j["a"] = huge_string_json::array({huge_string_t::as_size("value", limit - 8)});
+
+            CHECK_THROWS_AS(huge_string_json::to_bson(j), huge_string_json::out_of_range&);
+        }
+
        SECTION("document")
        {
            // an oversized string nested one level deep makes the
@@ -899,6 +923,38 @@ TEST_CASE("BSON")
            CHECK_THROWS_AS(_ = json::from_bson(input), json::parse_error&);
        }

+        SECTION("binary member with subtype 0x02 (old binary) with a truncated inner length")
+        {
+            // the inner length field is cut off by the end of the input
+            std::vector<std::uint8_t> const input =
+            {
+                0x0F, 0x00, 0x00, 0x00, // size (little endian)
+                0x05, 'a', 0x00, // entry: binary
+                0x08, 0x00, 0x00, 0x00, // size of binary (little endian)
+                0x02, // "old binary" subtype
+                0x01 // first byte of the inner length
+            };
+
+            json _;
+            CHECK_THROWS_WITH_AS(_ = json::from_bson(input), "[json.exception.parse_error.110] parse error at byte 14: syntax error while parsing BSON number: unexpected end of input", json::parse_error&);
+            CHECK(json::from_bson(input, true, false).is_discarded());
+        }
+
+        SECTION("string member that is cut off by the end of the input")
+        {
+            std::vector<std::uint8_t> const input =
+            {
+                0x0F, 0x00, 0x00, 0x00, // size (little endian)
+                0x02, 'a', 0x00, // entry: string
+                0x0A, 0x00, 0x00, 0x00, // size of the string (little endian)
+                'b', 'c' // the string ends early
+            };
+
+            json _;
+            CHECK_THROWS_WITH_AS(_ = json::from_bson(input), "[json.exception.parse_error.110] parse error at byte 14: syntax error while parsing BSON string: unexpected end of input", json::parse_error&);
+            CHECK(json::from_bson(input, true, false).is_discarded());
+        }
+
        SECTION("Some more complex document")
        {
            json const j =
@@ -2174,6 +2230,25 @@ value = depth % 2 == 0 ? json{{"a", std::move(value)}, {"b", {1, "x"}}} :
        CHECK(output.empty());
    }

+#if !defined(JSON_NOEXCEPTION)
+    SECTION("U+0000 in a long key is found at any position")
+    {
+        // the key is searched eight characters at a time
+        for (const std::string& key :
+                {
+                    std::string("abc\0defghijkl", 12), std::string("abcdefgh\0ijkl", 13), std::string("abcdefghijklmnop\0", 17), std::string("\0abcdefghijkl", 13),
+                    std::string("abcdefghijklmno\0", 16)
+                })
+        {
+            CAPTURE(key)
+            const json value = json::object({{key, 1}});
+            std::vector<std::uint8_t> output;
+            CHECK_THROWS_AS(json::to_bson(value, output), json::out_of_range&);
+            CHECK(output.empty());
+        }
+    }
+#endif
+
    SECTION("a binary subtype that doesn't fit a byte is rejected before anything is written (#5675)")
    {
        // the offending value is nested, so this also covers that the check
@@ -1809,6 +1809,30 @@ TEST_CASE("CBOR")
            CHECK(json::from_cbor(std::vector<uint8_t>({0xa1, 0xff, 0x01}), true, false).is_discarded());
        }

+        SECTION("tag in front of a key that is cut off by the end of the input")
+        {
+            // 0xD8: the tag number is in the next byte, which is missing
+            const std::vector<std::uint8_t> input = {0xA1, 0xD8};
+            json _;
+            for (const auto handler :
+                    {
+                        json::cbor_tag_handler_t::ignore, json::cbor_tag_handler_t::store
+                    })
+            {
+                CHECK_THROWS_WITH_AS(_ = json::from_cbor(input, true, true, handler), "[json.exception.parse_error.110] parse error at byte 3: syntax error while parsing CBOR number: unexpected end of input", json::parse_error&);
+                CHECK(json::from_cbor(input, true, false, handler).is_discarded());
+            }
+        }
+
+        SECTION("chunk of an indefinite-length string that is cut off by the end of the input")
+        {
+            // the second byte announces a chunk of three bytes, but two follow
+            const std::vector<std::uint8_t> input = {0x7F, 0x63, 'a', 'b'};
+            json _;
+            CHECK_THROWS_WITH_AS(_ = json::from_cbor(input), "[json.exception.parse_error.110] parse error at byte 5: syntax error while parsing CBOR string: unexpected end of input", json::parse_error&);
+            CHECK(json::from_cbor(input, true, false).is_discarded());
+        }
+
        SECTION("tag in front of a key")
        {
            const auto ignore = json::cbor_tag_handler_t::ignore;
@@ -2520,6 +2544,34 @@ TEST_CASE("CBOR arrays of scalars from contiguous and non-contiguous input")
    }
 }

+TEST_CASE("CBOR arrays of one element from contiguous and non-contiguous input")
+{
+    // contiguous input leaves an array of one element to the general path
+    // rather than to the loop that reads arrays of scalars; both inputs must
+    // still give the same events, value, or error for the complete document
+    // and for every truncation of it, with enough bytes after each array that
+    // the loop could have been entered
+    const json j = json::parse(R"({"a": [[[[1.5]]]], "b": [7], "c": [{"x": 2.5}], "d": ["s"], "e": [[1, 2]], "f": [null], "g": 1.25})");
+    const std::vector<std::uint8_t> bytes = json::to_cbor(j);
+
+    CHECK(json::from_cbor(bytes) == j);
+
+    for (std::size_t length = 0; length <= bytes.size(); ++length)
+    {
+        CAPTURE(length)
+        const std::vector<std::uint8_t> contiguous(bytes.begin(), bytes.begin() + static_cast<std::ptrdiff_t>(length));
+        const std::list<std::uint8_t> bytewise(contiguous.begin(), contiguous.end());
+
+        CHECK(json::from_cbor(contiguous, true, false).dump() == json::from_cbor(bytewise.begin(), bytewise.end(), true, false).dump());
+
+        SaxEventLogger from_contiguous;
+        SaxEventLogger from_bytewise;
+        CHECK(json::sax_parse(contiguous, &from_contiguous, json::input_format_t::cbor, true, false)
+              == json::sax_parse(bytewise.begin(), bytewise.end(), &from_bytewise, json::input_format_t::cbor, true, false));
+        CHECK(from_contiguous.events == from_bytewise.events);
+    }
+}
+
 TEST_CASE("CBOR indefinite-length strings do not recurse per chunk")
 {
    // Reading an indefinite-length string or byte array used to call itself
@@ -2092,6 +2092,12 @@ TEST_CASE("UTF-8 validators accept the same sequences")
        }
    };

+    // an ASCII byte is a sequence of its own
+    for (unsigned lead = 0; lead < 0x80; ++lead)
+    {
+        CHECK(nlohmann::detail::utf8_shape(static_cast<std::uint8_t>(lead)).length == 1);
+    }
+
    for (unsigned lead = 0x80; lead <= 0xFF; ++lead)
    {
        const auto shape = nlohmann::detail::utf8_shape(static_cast<std::uint8_t>(lead));
@@ -2157,3 +2163,73 @@ TEST_CASE("UTF-8 validators accept the same sequences")
        }
    }
 }
+
+TEST_CASE("float_bigint")
+{
+    // the big integer of the exact comparison of a float token with the
+    // midpoint between two floats (digit_comparison())
+    using nlohmann::detail::float_bigint;
+
+    SECTION("zero")
+    {
+        // shifting zero keeps it zero, whatever the distance
+        float_bigint zero(0);
+        zero.shift_left(0);
+        zero.shift_left(5);
+        zero.shift_left(64);
+        CHECK(zero.compare(float_bigint(0)) == 0);
+        CHECK(zero.compare(float_bigint(1)) == -1);
+        CHECK(float_bigint(1).compare(zero) == 1);
+    }
+
+    SECTION("compare numbers of different lengths")
+    {
+        // the number with more 32-bit limbs is the greater one
+        const float_bigint small(0xFFFFFFFFu);
+        const float_bigint large(std::uint64_t{1} << 32u);
+        CHECK(small.compare(large) == -1);
+        CHECK(large.compare(small) == 1);
+        CHECK(large.compare(large) == 0);
+
+        // a shift can add a limb
+        float_bigint shifted(1);
+        shifted.shift_left(32);
+        CHECK(shifted.compare(large) == 0);
+        shifted.shift_left(1);
+        CHECK(shifted.compare(large) == 1);
+        CHECK(large.compare(shifted) == -1);
+    }
+
+    SECTION("compare numbers of the same length")
+    {
+        CHECK(float_bigint(2).compare(float_bigint(3)) == -1);
+        CHECK(float_bigint(3).compare(float_bigint(2)) == 1);
+        CHECK(float_bigint(3).compare(float_bigint(3)) == 0);
+        CHECK(float_bigint((std::uint64_t{3} << 32u) | 1u).compare(float_bigint((std::uint64_t{3} << 32u) | 2u)) == -1);
+    }
+}
+
+TEST_CASE("serialization of short strings")
+{
+    // the serializer takes strings of up to 32 characters that need no
+    // escaping by a table lookup of its own where the scan is not vectorized
+    // (this file is built that way, too, with JSON_NO_SIMD)
+    for (const std::string& s :
+            {
+                std::string(), std::string("a"), std::string("hello"), std::string("0123456789abcdef"), std::string("0123456789abcdef0123456789abcdef"),
+                std::string("0123456789abcdef0123456789abcdef0")
+            })
+    {
+        CAPTURE(s)
+        const json j = s;
+        const std::string quoted = "\"" + s + "\""; // NOLINT(performance-inefficient-string-concatenation)
+        CHECK(j.dump() == quoted);
+        CHECK(j.dump(-1, ' ', true) == quoted);
+        CHECK(json({{s, s}}).dump() == "{" + quoted + ":" + quoted + "}"); // NOLINT(performance-inefficient-string-concatenation)
+    }
+
+    // a character that needs an escape
+    CHECK(json("a\"b").dump() == "\"a\\\"b\"");
+    CHECK(json("caf\xC3\xA9").dump() == "\"caf\xC3\xA9\"");
+    CHECK(json("caf\xC3\xA9").dump(-1, ' ', true) == "\"caf\\u00e9\"");
+}
@@ -2953,651 +2953,6 @@ TEST_CASE("diagnostic positions: value lifetime, input adapters, and SAX")
 }
 #endif

-namespace
-{
-/// builds a value like json::parse(), but asks the parser to recover from
-/// errors (see #3989), and checks that the events it receives are balanced
-class RecoveringDomParser
-{
-  public:
-    explicit RecoveringDomParser(json& j, std::size_t max_errors_ = static_cast<std::size_t>(-1))
-        : dom(j, false)
-        , max_errors(max_errors_)
-    {}
-
-    bool null()
-    {
-        value();
-        return dom.null();
-    }
-
-    bool boolean(bool val)
-    {
-        value();
-        return dom.boolean(val);
-    }
-
-    bool number_integer(json::number_integer_t val)
-    {
-        value();
-        return dom.number_integer(val);
-    }
-
-    bool number_unsigned(json::number_unsigned_t val)
-    {
-        value();
-        return dom.number_unsigned(val);
-    }
-
-    bool number_float(json::number_float_t val, const std::string& s)
-    {
-        value();
-        return dom.number_float(val, s);
-    }
-
-    bool string(std::string& val)
-    {
-        value();
-        return dom.string(val);
-    }
-
-    bool binary(json::binary_t& val)
-    {
-        value();
-        return dom.binary(val);
-    }
-
-    bool start_object(std::size_t elements)
-    {
-        value();
-        stack.push_back('o');
-        return dom.start_object(elements);
-    }
-
-    bool key(std::string& val)
-    {
-        ++events;
-        if (stack.empty() || stack.back() != 'o')
-        {
-            well_formed = false;
-            return false;
-        }
-        stack.back() = 'v';
-        return dom.key(val);
-    }
-
-    bool end_object()
-    {
-        ++events;
-        if (stack.empty() || stack.back() != 'o')
-        {
-            well_formed = false;
-            return false;
-        }
-        stack.pop_back();
-        return dom.end_object();
-    }
-
-    bool start_array(std::size_t elements)
-    {
-        value();
-        stack.push_back('a');
-        return dom.start_array(elements);
-    }
-
-    bool end_array()
-    {
-        ++events;
-        if (stack.empty() || stack.back() != 'a')
-        {
-            well_formed = false;
-            return false;
-        }
-        stack.pop_back();
-        return dom.end_array();
-    }
-
-    bool parse_error(std::size_t /*unused*/, const std::string& /*unused*/, const json::exception& ex)
-    {
-        errors.emplace_back(ex.what());
-        return errors.size() < max_errors;
-    }
-
-    /// whether the events were balanced and every key was followed by a value
-    bool balanced() const
-    {
-        return well_formed && stack.empty();
-    }
-
-    /// builds the value
-    nlohmann::detail::json_sax_dom_parser<json> dom;
-    std::vector<std::string> errors {}; // NOLINT(readability-redundant-member-init)
-    std::size_t events = 0;
-    /// the open containers: 'a' for an array, 'o' for an object that expects
-    /// a key, 'v' for an object that expects the value of a key
-    std::vector<char> stack {}; // NOLINT(readability-redundant-member-init)
-    bool well_formed = true;
-    std::size_t max_errors;
-
-  private:
-    /// a value is passed: it is an array element, or the value of a key
-    void value()
-    {
-        ++events;
-        if (!stack.empty())
-        {
-            if (stack.back() == 'v')
-            {
-                stack.back() = 'o';
-            }
-            else if (stack.back() == 'o')
-            {
-                // a value without a key
-                well_formed = false;
-            }
-        }
-    }
-
-};
-
-struct RecoveryResult
-{
-    json value;
-    std::vector<std::string> errors;
-    std::size_t events;
-    bool ok;
-    bool balanced;
-};
-
-template<typename InputType>
-RecoveryResult parse_recovering(InputType&& input, const bool strict = true,
-                                const bool ignore_comments = false, const bool ignore_trailing_commas = false)
-{
-    json j;
-    RecoveringDomParser sax(j);
-    const bool ok = json::sax_parse(std::forward<InputType>(input), &sax, json::input_format_t::json,
-                                    strict, ignore_comments, ignore_trailing_commas);
-    return {j, sax.errors, sax.events, ok, sax.balanced()};
-}
-
-/// stops after a number of events, but recovers from errors
-class RecoveringCountdown
-{
-  public:
-    explicit RecoveringCountdown(const int count)
-        : countdown(count)
-    {}
-
-    bool null()
-    {
-        return countdown.null();
-    }
-
-    bool boolean(bool val)
-    {
-        return countdown.boolean(val);
-    }
-
-    bool number_integer(json::number_integer_t val)
-    {
-        return countdown.number_integer(val);
-    }
-
-    bool number_unsigned(json::number_unsigned_t val)
-    {
-        return countdown.number_unsigned(val);
-    }
-
-    bool number_float(json::number_float_t val, const std::string& s)
-    {
-        return countdown.number_float(val, s);
-    }
-
-    bool string(std::string& val)
-    {
-        return countdown.string(val);
-    }
-
-    bool binary(json::binary_t& val)
-    {
-        return countdown.binary(val);
-    }
-
-    bool start_object(std::size_t elements)
-    {
-        return countdown.start_object(elements);
-    }
-
-    bool key(std::string& val)
-    {
-        return countdown.key(val);
-    }
-
-    bool end_object()
-    {
-        return countdown.end_object();
-    }
-
-    bool start_array(std::size_t elements)
-    {
-        return countdown.start_array(elements);
-    }
-
-    bool end_array()
-    {
-        return countdown.end_array();
-    }
-
-    bool parse_error(std::size_t /*position*/, const std::string& /*last_token*/, const json::exception& /*ex*/) // NOLINT(readability-convert-member-functions-to-static)
-    {
-        return true;
-    }
-
-  private:
-    SaxCountdown countdown;
-};
-
-/// a repaired input: the value it is repaired to, and the number of errors
-struct Repair
-{
-    const char* input;
-    const char* expected;
-    std::size_t errors;
-};
-} // namespace
-
-TEST_CASE("parser error recovery (#3989)")
-{
-    SECTION("repairs")
-    {
-        const std::vector<Repair> repairs =
-        {
-            // a missing separator is inserted
-            {"[1 2]", "[1,2]", 1},
-            {R"({"a":1 "b":2})", R"({"a":1,"b":2})", 1},
-            {R"({"a" 1})", R"({"a":1})", 1},
-            {"[1 tru 2]", "[1,null,2]", 2},
-            {R"({"a" "b": 1})", R"({"a":"b"})", 2},
-
-            // a missing value is null in an object; in an array, a ',' stands
-            // for null, while an array that ends there just ends
-            {R"({"a":})", R"({"a":null})", 1},
-            {R"({"a"})", R"({"a":null})", 1},
-            {R"({"a","b":1})", R"({"a":null,"b":1})", 1},
-            {"[1,,2]", "[1,null,2]", 1},
-            {"[,1]", "[null,1]", 1},
-            {"[1,]", "[1]", 1},
-            {"[1,2,3,]", "[1,2,3]", 1},
-            {R"({"a":1,})", R"({"a":1})", 1},
-
-            // a broken string keeps what can be read
-            {R"(["a\qb"])", R"(["aqb"])", 1},
-            {R"({"na\me":1})", R"({"name":1})", 1},
-            {"[\"\xFF\"]", R"(["\uFFFD"])", 1},
-            {"[\"a\xC3(\"]", R"(["a\uFFFD("])", 1},
-            {"[\"\xE2\x82\"]", R"(["\uFFFD"])", 1},
-            {"[\"\xC3\\\\\", 1]", R"(["\uFFFD\\",1])", 1},
-            {R"(["\u12"])", R"(["\uFFFD"])", 1},
-            {R"(["\u12G4"])", R"(["\uFFFDG4"])", 1},
-            {R"(["\uDC00x"])", R"(["\uFFFDx"])", 1},
-            {R"(["\uD800x"])", R"(["\uFFFDx"])", 1},
-            {R"(["\uD800\u0041"])", R"(["\uFFFDA"])", 1},
-            {R"(["\uD800\uD800\uDC00"])", R"(["\uFFFD\uD800\uDC00"])", 1},
-            {R"(["\uD800\uD800\uD800x"])", R"(["\uFFFD\uFFFD\uFFFDx"])", 1},
-            {
-                R"(["\uD800\"x", 1])", R"(["\uFFFD\"x",1])", 1
-            },
-            {R"(["\uD800\q"])", R"(["\uFFFDq"])", 1},
-            {"[\"a\tb\"]", R"(["a\tb"])", 1},
-            {R"(["a\qb\u0041\x"])", R"(["aqbAx"])", 1},
-
-            // a broken number keeps its longest valid prefix
-            {"[1.]", "[1]", 1},
-            {"[-2.]", "[-2]", 1},
-            {"[1.5e]", "[1.5]", 1},
-            {"[1e+]", "[1]", 1},
-            {"[1.x2, 3]", "[1,3]", 1},
-
-            // what cannot be read at all is null
-            {"[1,NaN,3]", "[1,null,3]", 1},
-            {"[tru]", "[null]", 1},
-            {"[-]", "[null]", 1},
-            {R"({"a":Infinity})", R"({"a":null})", 1},
-
-            // a stray token is dropped
-            {"[:1]", "[1]", 1},
-            {R"(["a":1])", R"(["a",1])", 1},
-            {R"({"a"::1})", R"({"a":1})", 1},
-
-            // a member that cannot be read is skipped
-            {R"({1:2,"b":3})", R"({"b":3})", 1},
-            {R"({"a":1 2})", R"({"a":1})", 1},
-            {R"({,"a":1})", R"({"a":1})", 1},
-            {R"({"a":1,,"b":2})", R"({"a":1,"b":2})", 1},
-            {"{a:1}", "{}", 1},
-            {R"({"a":1 [1,{"b":2}], "c":3})", R"({"a":1,"c":3})", 1},
-            {R"([{1}, "a"])", R"([{},"a"])", 1},
-
-            // a wrong closing bracket closes the innermost container
-            {R"({"a":[1,2}, "b":3})", R"({"a":[1,2],"b":3})", 1},
-            {R"([{"a":1], 2])", R"([{"a":1},2])", 1},
-            {"{]", "{}", 1},
-            {"[}", "[]", 1},
-
-            // the end of the input closes all containers
-            {R"({"a":[1,2)", R"({"a":[1,2]})", 1},
-            {"[", "[]", 1},
-            {"{", "{}", 1},
-            {R"({"a")", R"({"a":null})", 1},
-            {R"({"a":)", R"({"a":null})", 1},
-            {"[1,", "[1]", 1},
-            {"[[[1", "[[[1]]]", 1},
-            {
-                R"(["abc)", R"(["abc"])", 2
-            },
-            {"[1,tr", "[1,null]", 2},
-            {"\"abc", "\"abc\"", 1},
-            {"[\"ab\ncd\"]", R"(["ab",null,"]"])", 4},
-
-            // what comes before the top-level value is skipped
-            {")]}'\n{\"a\":1}", R"({"a":1})", 1},
-            {R"(data: {"a":1})", R"({"a":1})", 1},
-            {"\xEF\xBB[1]", "[1]", 1},
-
-            // what comes after it is an error that ends parsing
-            {R"({"a":1}})", R"({"a":1})", 1},
-            {"[1}]", "[1]", 2},
-            {"[1] [2]", "[1]", 1},
-        };
-
-        for (const auto& repair : repairs)
-        {
-            CAPTURE(repair.input)
-            const auto result = parse_recovering(std::string(repair.input));
-            CHECK(!result.ok);
-            CHECK(result.balanced);
-            CHECK(result.value == json::parse(repair.expected));
-            CHECK(result.errors.size() == repair.errors);
-        }
-    }
-
-    SECTION("number overflow")
-    {
-        const auto result = parse_recovering(std::string("[1e999,-1e999]"));
-        CHECK(!result.ok);
-        CHECK(result.balanced);
-        CHECK(result.errors.size() == 2);
-        CHECK(result.errors[0] == "[json.exception.out_of_range.406] number overflow parsing '1e999'");
-        REQUIRE(result.value.size() == 2);
-        CHECK(result.value[0].is_number_float());
-        CHECK(result.value[0].get<double>() == std::numeric_limits<double>::infinity());
-        CHECK(result.value[1].get<double>() == -std::numeric_limits<double>::infinity());
-
-        // the SAX parser gets the number's text
-        SaxEventLogger logger;
-        logger.recover = true;
-        CHECK(!json::sax_parse("1e999", &logger));
-        CHECK(logger.events == std::vector<std::string>({"parse_error(5)", "number_float(1e999)"}));
-    }
-
-    SECTION("nothing to recover")
-    {
-        for (const std::string s :
-                {
-                    "", "   ", "]", "tru", "NaN", ",:", "/* comment"
-                })
-        {
-            CAPTURE(s)
-            const auto result = parse_recovering(s, true, true);
-            CHECK(!result.ok);
-            CHECK(result.balanced);
-            CHECK(result.events == 0);
-            CHECK(result.value == nullptr);
-            CHECK(result.errors.size() == 1);
-        }
-    }
-
-    SECTION("error messages")
-    {
-        // the first error is reported as without recovery
-        for (const std::string s :
-                {
-                    "[1 2]", R"({"a":1 "b":2})", R"({"a" 1})", R"({"a":})", "[1,]", "[1.]",
-                    R"(["a\qb"])", "[1e999]", "{1:2}", R"({"a":[1,2}})", "[1,", "[1] [2]", "{a:1}"
-                })
-        {
-            CAPTURE(s)
-            const auto result = parse_recovering(s);
-            REQUIRE(!result.errors.empty());
-            json _;
-            CHECK_THROWS_WITH_STD_STR(_ = json::parse(s), result.errors.front());
-        }
-
-        // the token of an error begins where the previous error was
-        const auto result = parse_recovering(std::string("[tru, fals, nul]"));
-        CHECK(result.errors == std::vector<std::string>(
-        {
-            "[json.exception.parse_error.101] parse error at line 1, column 5: syntax error while parsing value - invalid literal; last read: '[tru,'",
-            "[json.exception.parse_error.101] parse error at line 1, column 11: syntax error while parsing value - invalid literal; last read: ', fals,'",
-            "[json.exception.parse_error.101] parse error at line 1, column 16: syntax error while parsing value - invalid literal; last read: ', nul]'"
-        }));
-        CHECK(result.value == json::parse("[null,null,null]"));
-    }
-
-    SECTION("events")
-    {
-        // see #4522
-        SaxEventLogger logger;
-        logger.recover = true;
-        CHECK(!json::sax_parse(R"([{1}, "a"])", &logger));
-        CHECK(logger.events == std::vector<std::string>(
-        {
-            "start_array()", "start_object()", "parse_error(3)", "end_object()", "string(a)", "end_array()"
-        }));
-    }
-
-    SECTION("options")
-    {
-        SECTION("strict")
-        {
-            const auto result = parse_recovering(std::string("[1 2] [3]"), false);
-            CHECK(!result.ok);
-            CHECK(result.value == json::parse("[1,2]"));
-            CHECK(result.errors.size() == 1);
-        }
-
-        SECTION("ignore_trailing_commas")
-        {
-            for (const std::string s :
-                    {
-                        "[1,]", R"({"a":1,})", "[[1,],]"
-                    })
-            {
-                CAPTURE(s)
-                const auto result = parse_recovering(s, true, false, true);
-                CHECK(result.ok);
-                CHECK(result.errors.empty());
-            }
-
-            auto result = parse_recovering(std::string("[1,,]"), true, false, true);
-            CHECK(result.value == json::parse("[1,null]"));
-            CHECK(result.errors.size() == 1);
-
-            result = parse_recovering(std::string(R"({"a":1,,})"), true, false, true);
-            CHECK(result.value == json::parse(R"({"a":1})"));
-            CHECK(result.errors.size() == 1);
-        }
-
-        SECTION("ignore_comments")
-        {
-            auto result = parse_recovering(std::string("[1 /* one */ 2]"), true, true);
-            CHECK(result.value == json::parse("[1,2]"));
-            CHECK(result.errors.size() == 1);
-
-            // a comment that is not closed runs to the end of the input, which
-            // is not reported again
-            result = parse_recovering(std::string("[1, 2 /* unterminated"), true, true);
-            CHECK(result.balanced);
-            CHECK(result.value == json::parse("[1,2]"));
-            CHECK(result.errors.size() == 1);
-
-            // a '/' that does not begin a comment is garbage
-            result = parse_recovering(std::string("[1, /x, 2]"), true, true);
-            CHECK(result.balanced);
-            CHECK(result.value == json::parse("[1,null,2]"));
-            CHECK(result.errors.size() == 1);
-        }
-    }
-
-    SECTION("null bytes")
-    {
-        // a null byte ends the input, unless JSON_STRICT_NUL_HANDLING is set
-        const auto result = parse_recovering(std::string("[1,\0x", 5));
-        CHECK(result.balanced);
-        CHECK(!result.ok);
-#ifdef JSON_TEST_STRICT_NUL_HANDLING_ENABLED
-        CHECK(result.value == json::parse("[1,null]"));
-#else
-        CHECK(result.value == json::parse("[1]"));
-        CHECK(result.errors.size() == 1);
-#endif
-
-        const auto in_string = parse_recovering(std::string("[\"a\0b\"]", 7));
-        CHECK(in_string.balanced);
-#ifdef JSON_TEST_STRICT_NUL_HANDLING_ENABLED
-        CHECK(in_string.value == json::array({std::string("a\0b", 3)}));
-#else
-        CHECK(in_string.value == json::parse(R"(["a"])"));
-#endif
-    }
-
-    SECTION("the SAX parser stops recovering")
-    {
-        json j;
-        RecoveringDomParser sax(j, 2);
-        CHECK(!json::sax_parse("[1 2 3 4 5]", &sax));
-        CHECK(sax.errors.size() == 2);
-
-        // an error at a delimiter that an invalid token consumed is reported
-        // to the SAX parser, too
-        json j2;
-        RecoveringDomParser sax2(j2, 2);
-        CHECK(!json::sax_parse("[tru}, 1]", &sax2));
-        CHECK(sax2.errors.size() == 2);
-    }
-
-    SECTION("an event stops parsing during a repair")
-    {
-        // start_object() and key() are passed, then null() for the missing
-        // value returns false
-        RecoveringCountdown countdown(2);
-        CHECK(!json::sax_parse(R"({"a":})", &countdown));
-
-        // the end of the input: end_array() for the second array returns false
-        RecoveringCountdown countdown2(4);
-        CHECK(!json::sax_parse("[[1", &countdown2));
-    }
-
-    SECTION("input adapters")
-    {
-        // the lexer reads contiguous and streaming input differently, and it
-        // puts back a character that ended an invalid token
-        for (const std::string s :
-                {
-                    "[1 2]", "[tru}, 1]", R"({"a" "b\q", "c":[1.x, 2}})", "[\"\xFF\xC3(\", -, 1e+]", "{a:1,\"b\":2", ")]}' [1]"
-                })
-        {
-            CAPTURE(s)
-            const auto reference = parse_recovering(s);
-            CHECK(reference.balanced);
-
-            const auto from_c_string = parse_recovering(s.c_str());
-            CHECK(from_c_string.value == reference.value);
-            CHECK(from_c_string.errors == reference.errors);
-
-            const std::list<char> l(s.begin(), s.end());
-            json j;
-            RecoveringDomParser sax(j);
-            CHECK(!json::sax_parse(l.begin(), l.end(), &sax));
-            CHECK(j == reference.value);
-            CHECK(sax.errors == reference.errors);
-
-            std::istringstream ss(s);
-            const auto from_stream = parse_recovering(ss);
-            CHECK(from_stream.value == reference.value);
-            CHECK(from_stream.errors == reference.errors);
-        }
-    }
-
-    SECTION("long runs of errors")
-    {
-        // no error may copy all the input read before it
-        const auto closing = parse_recovering("[" + std::string(100000, '}'));
-        CHECK(closing.balanced);
-        CHECK(closing.value == json::array());
-
-        const auto garbage = parse_recovering("[" + std::string(100000, 'x') + "]");
-        CHECK(garbage.balanced);
-        CHECK(garbage.errors.size() == 1);
-
-        const auto commas = parse_recovering("{" + std::string(100000, ',') + "}");
-        CHECK(commas.balanced);
-        CHECK(commas.value == json::object());
-    }
-
-    SECTION("mutations of valid input")
-    {
-        // whatever the input, the events are balanced, every error is reported
-        // at most once, and valid input is parsed as usual
-        const std::vector<std::string> documents =
-        {
-            R"({"name": "value", "list": [1, -2.5, true, null, {"x": [[]]}], "e": "\u00e9"})",
-            R"([{"a": [1, 2, {"b": "c"}]}, [], {}, "\ud83d\ude00", 1e10])",
-            "{\"\xC3\xA9\": \"\xF0\x9F\x98\x80\"}",
-            R"(  {"k" : [ "v" , 0 ] }  )",
-        };
-        // each character that can be inserted, including a null byte
-        const std::string insertions("[]{},:\"x\\\0\xFF", 11);
-
-        std::vector<std::string> inputs;
-        for (const auto& doc : documents)
-        {
-            for (std::size_t i = 0; i <= doc.size(); ++i)
-            {
-                inputs.push_back(doc.substr(0, i));
-                if (i < doc.size())
-                {
-                    inputs.push_back(doc.substr(0, i) + doc.substr(i + 1));
-                }
-                for (const char c : insertions)
-                {
-                    inputs.push_back(doc.substr(0, i) + c + doc.substr(i));
-                }
-            }
-        }
-
-        for (const auto& s : inputs)
-        {
-            CAPTURE(s)
-            const auto result = parse_recovering(s);
-            CHECK(result.balanced);
-            CHECK(result.errors.size() <= s.size() + 1);
-            CHECK(result.events <= (4 * s.size()) + 4);
-            if (json::accept(s))
-            {
-                CHECK(result.ok);
-                CHECK(result.errors.empty());
-                CHECK(result.value == json::parse(s));
-            }
-            else
-            {
-                CHECK(!result.ok);
-                CHECK(!result.errors.empty());
-            }
-        }
-    }
-}
-
 TEST_CASE("accept() agrees with parse() on floats around the overflow limit")
 {
    // accept() does not convert a float that cannot overflow; the tokens
@@ -1260,6 +1260,44 @@ TEST_CASE("value conversion")
    #undef JSON_HAS_CPP_17
 #endif

+TEST_CASE("get<T>() of a boolean (#5988)")
+{
+    // a boolean converts to 0/1 for every arithmetic type except number_integer_t, number_unsigned_t and
+    // number_float_t, whose dedicated from_json() overloads throw
+    const json t = true;
+    const json f = false;
+
+    SECTION("0 and 1")
+    {
+        // long and unsigned long are left out: they are std::int64_t and std::uint64_t on some platforms
+        CHECK(t.get<bool>() == true);
+        CHECK(f.get<bool>() == false);
+        CHECK(t.get<char>() == 1);
+        CHECK(t.get<signed char>() == 1);
+        CHECK(t.get<unsigned char>() == 1);
+        CHECK(t.get<short>() == 1); // NOLINT(google-runtime-int)
+        CHECK(t.get<unsigned short>() == 1); // NOLINT(google-runtime-int)
+        CHECK(t.get<int>() == 1);
+        CHECK(t.get<unsigned>() == 1);
+        CHECK(t.get<float>() == 1.0F);
+        CHECK(t.get<long double>() == 1.0L);
+        CHECK(f.get<int>() == 0);
+        CHECK(f.get<float>() == 0.0F);
+    }
+
+#if !defined(JSON_NOEXCEPTION)
+    SECTION("number_integer_t, number_unsigned_t and number_float_t throw")
+    {
+        CHECK_THROWS_WITH_AS(t.get<json::number_integer_t>(), "[json.exception.type_error.302] type must be number, but is boolean", json::type_error&);
+        CHECK_THROWS_WITH_AS(t.get<json::number_unsigned_t>(), "[json.exception.type_error.302] type must be number, but is boolean", json::type_error&);
+        CHECK_THROWS_WITH_AS(t.get<json::number_float_t>(), "[json.exception.type_error.302] type must be number, but is boolean", json::type_error&);
+        CHECK_THROWS_WITH_AS(f.get<json::number_integer_t>(), "[json.exception.type_error.302] type must be number, but is boolean", json::type_error&);
+        CHECK_THROWS_WITH_AS(f.get<json::number_unsigned_t>(), "[json.exception.type_error.302] type must be number, but is boolean", json::type_error&);
+        CHECK_THROWS_WITH_AS(f.get<json::number_float_t>(), "[json.exception.type_error.302] type must be number, but is boolean", json::type_error&);
+    }
+#endif
+}
+
 #ifdef JSON_HAS_CPP_14
    #undef JSON_HAS_CPP_14
 #endif
@@ -210,3 +210,23 @@ TEST_CASE("regression test #5476 - array type without reserve()")
        CHECK(json::from_cbor(truncated, true, false).is_discarded());
    }
 }
+
+TEST_CASE("array type with std::deque nested beyond the recursion limit")
+{
+    // the binary writers finish a value nested deeper than
+    // recursion_depth_limit() with an explicit stack of frames; with the
+    // iterators of std::deque, these frames are copied and moved through
+    // their own special members
+    deque_json j = 1;
+    for (int i = 0; i < 200; ++i)
+    {
+        deque_json outer = deque_json::array();
+        outer.push_back(std::move(j));
+        j = std::move(outer);
+    }
+
+    // 200 arrays of one element each (0x81) around the integer 1
+    std::vector<std::uint8_t> expected(200, 0x81);
+    expected.push_back(0x01);
+    CHECK(deque_json::to_cbor(j) == expected);
+}
@@ -7,6 +7,7 @@
 // SPDX-License-Identifier: MIT

 #include <algorithm>
+#include <memory>
 #include <set>
 #include <sstream>
 #include <string>
@@ -495,3 +496,92 @@ TEST_CASE("Regression test for issue #5674 - copy construction must not require
        CHECK(*c == 1);
    }
 }
+
+// counts the constructions and destructions of the base class (#5995)
+struct counting_base
+{
+    static std::size_t constructions;
+    static std::size_t destructions;
+
+    counting_base() noexcept
+    {
+        ++constructions;
+    }
+    counting_base(const counting_base& /*unused*/) noexcept
+    {
+        ++constructions;
+    }
+    counting_base(counting_base&& /*unused*/) noexcept
+    {
+        ++constructions;
+    }
+    counting_base& operator=(const counting_base& /*unused*/) noexcept = default;
+    counting_base& operator=(counting_base&& /*unused*/) noexcept = default;
+    ~counting_base()
+    {
+        ++destructions;
+    }
+
+    static void reset() noexcept
+    {
+        constructions = 0;
+        destructions = 0;
+    }
+};
+
+std::size_t counting_base::constructions = 0;
+std::size_t counting_base::destructions = 0;
+
+using json_with_counting_base = nlohmann::json::with_base_class_t<counting_base>;
+
+TEST_CASE("destroying a value does not construct the custom base class")
+{
+    // regression test for #5995: destroying an array or object used a
+    // default-constructed basic_json as a stand-in, which constructed a base
+    // class that belonged to no value (and could allocate in the noexcept
+    // destructor); now every destroyed value destroys exactly its own base
+    // object, and none is constructed
+    const auto check_destroy = [](std::unique_ptr<json_with_counting_base> j, std::size_t values)
+    {
+        counting_base::reset();
+        j = nullptr;
+        CHECK(counting_base::constructions == 0);
+        CHECK(counting_base::destructions == values);
+    };
+
+    SECTION("scalar")
+    {
+        check_destroy(std::unique_ptr<json_with_counting_base>(new json_with_counting_base(42)), 1);
+    }
+
+    SECTION("array and object")
+    {
+        check_destroy(std::unique_ptr<json_with_counting_base>(new json_with_counting_base(json_with_counting_base::parse(R"({"a":[1,2,3],"b":{"c":true}})"))), 7);
+        check_destroy(std::unique_ptr<json_with_counting_base>(new json_with_counting_base(json_with_counting_base::array())), 1);
+    }
+
+    SECTION("nested deeper than the recursion depth limit")
+    {
+        // alternating arrays and objects, so both kinds of container are
+        // walked by destroy_walk()
+        constexpr std::size_t depth = 1000;
+        std::unique_ptr<json_with_counting_base> j(new json_with_counting_base(json_with_counting_base::array({1, 2})));
+        for (std::size_t i = 0; i < depth; ++i)
+        {
+            json_with_counting_base outer = (i % 2 == 0) ? json_with_counting_base::object() : json_with_counting_base::array();
+            if (outer.is_object())
+            {
+                outer["x"] = std::move(*j);
+                outer["y"] = nullptr;
+            }
+            else
+            {
+                outer.push_back(std::move(*j));
+                outer.push_back(true);
+            }
+            *j = std::move(outer);
+        }
+        // the innermost array with its two elements, and two values per level
+        check_destroy(std::move(j), 3 + (2 * depth));
+    }
+}