diff --git a/.github/workflows/artifact.yaml b/.github/workflows/artifact.yaml
index eae5339d..1d9e6eed 100644
--- a/.github/workflows/artifact.yaml
+++ b/.github/workflows/artifact.yaml
@@ -11,6 +11,7 @@ jobs:
 
   sdist:
     runs-on: ubuntu-22.04
+    timeout-minutes: 10
     strategy:
       fail-fast: false
     env:
@@ -77,7 +78,7 @@ jobs:
           {
             cc: "clang",
             cflags: "-Os -fstrict-aliasing -fno-plt -flto=full -emit-llvm",
-            features: "avx512,no-panic,unstable-simd,yyjson",
+            features: "avx512,unstable-simd,yyjson",
             ldflags: "-fuse-ld=lld -Wl,-plugin-opt=also-emit-llvm -Wl,--as-needed -Wl,-zrelro,-znow",
             rustflags: "-C linker=clang -C link-arg=-fuse-ld=lld -C linker-plugin-lto -C lto=fat -C link-arg=-Wl,-zrelro,-znow -Z mir-opt-level=4 -Z threads=4 -D warnings",
             tag: null,
@@ -85,17 +86,17 @@ jobs:
           },
         ]
     env:
-      PYTHON: "${{ matrix.python.interpreter }}"
-      PYTHON_PACKAGE: "${{ matrix.python.package }}"
-      TARGET: "${{ matrix.arch.target }}"
+      CARGO_TARGET_DIR: "/tmp/orjson"
       CC: "${{ matrix.arch.cc }}"
-      VENV: ".venv"
-      FEATURES: "${{ matrix.arch.features }}"
       CFLAGS: "${{ matrix.arch.cflags }}"
+      COMPATIBILITY: "${{ matrix.python.compatibility }}"
+      FEATURES: "${{ matrix.arch.features }}"
       LDFLAGS: "${{ matrix.arch.ldflags }}"
+      PYTHON: "${{ matrix.python.interpreter }}"
+      PYTHON_PACKAGE: "${{ matrix.python.package }}"
       RUSTFLAGS: "${{ matrix.arch.rustflags }}"
-      CARGO_TARGET_DIR: "/tmp/orjson"
-      COMPATIBILITY: "${{ matrix.python.compatibility }}"
+      TARGET: "${{ matrix.arch.target }}"
+      VENV: ".venv"
     steps:
 
     - name: cpuinfo
@@ -167,7 +168,7 @@ jobs:
           {
             cc: "clang",
             cflags: "-Os -fstrict-aliasing -fno-plt -flto=full -emit-llvm",
-            features: "no-panic,unstable-simd,yyjson",
+            features: "unstable-simd,yyjson",
             ldflags: "-fuse-ld=lld -Wl,-plugin-opt=also-emit-llvm -Wl,--as-needed -Wl,-zrelro,-znow",
             rustflags: "-C linker=clang -C link-arg=-fuse-ld=lld -C linker-plugin-lto -C lto=fat -C link-arg=-Wl,-zrelro,-znow -Z mir-opt-level=4 -Z threads=4 -D warnings",
             tag: "aarch64",
@@ -175,17 +176,17 @@ jobs:
           },
         ]
     env:
-      PYTHON: "${{ matrix.python.interpreter }}"
-      PYTHON_PACKAGE: "${{ matrix.python.package }}"
-      TARGET: "${{ matrix.arch.target }}"
+      CARGO_TARGET_DIR: "/tmp/orjson"
       CC: "${{ matrix.arch.cc }}"
-      VENV: ".venv"
-      FEATURES: "${{ matrix.arch.features }}"
       CFLAGS: "${{ matrix.arch.cflags }}"
+      COMPATIBILITY: "${{ matrix.python.compatibility }}"
+      FEATURES: "${{ matrix.arch.features }}"
       LDFLAGS: "${{ matrix.arch.ldflags }}"
+      PYTHON: "${{ matrix.python.interpreter }}"
+      PYTHON_PACKAGE: "${{ matrix.python.package }}"
       RUSTFLAGS: "${{ matrix.arch.rustflags }}"
-      CARGO_TARGET_DIR: "/tmp/orjson"
-      COMPATIBILITY: "${{ matrix.python.compatibility }}"
+      TARGET: "${{ matrix.arch.target }}"
+      VENV: ".venv"
     steps:
 
     - name: cpuinfo
@@ -241,6 +242,7 @@ jobs:
 
   musllinux:
     runs-on: ubuntu-24.04
+    timeout-minutes: 10
     strategy:
       fail-fast: false
       matrix:
@@ -256,11 +258,11 @@ jobs:
           - target: aarch64-unknown-linux-musl
             arch: aarch64
             platform: linux/arm64
-            features: no-panic,unstable-simd,unwind,yyjson
+            features: unstable-simd,unwind,yyjson
           - target: x86_64-unknown-linux-musl
             arch: x86_64
             platform: linux/amd64
-            features: avx512,no-panic,unstable-simd,unwind,yyjson
+            features: avx512,unstable-simd,unwind,yyjson
     steps:
     - uses: actions/checkout@v4
 
@@ -317,6 +319,7 @@ jobs:
 
   manylinux_non_amd64:
     runs-on: ubuntu-24.04
+    timeout-minutes: 20
     strategy:
       fail-fast: false
       matrix:
@@ -331,28 +334,35 @@ jobs:
           {
             arch: 'aarch64',
             cflags: '-Os -flto=full -fstrict-aliasing',
-            features: 'no-panic,unstable-simd,yyjson',
+            features: 'unstable-simd,yyjson',
             rustflags: '-Z mir-opt-level=4 -C lto=fat -D warnings',
             target: 'aarch64-unknown-linux-gnu',
           },
+          {
+            arch: 'i686',
+            cflags: '-Os -flto -fstrict-aliasing',
+            features: 'unstable-simd,yyjson',
+            rustflags: '-Z mir-opt-level=4 -C lto=fat -D warnings',
+            target: 'i686-unknown-linux-gnu',
+          },
           {
             arch: 'armv7',
             cflags: '-Os -flto=full -fstrict-aliasing',
-            features: 'no-panic,yyjson', # no SIMD
+            features: 'yyjson', # no SIMD
             rustflags: '-Z mir-opt-level=4 -C lto=fat -D warnings -C opt-level=s',
             target: 'armv7-unknown-linux-gnueabihf',
           },
           {
             arch: 'ppc64le',
             cflags: '-Os -flto=full -fstrict-aliasing',
-            features: 'no-panic,unstable-simd,yyjson',
+            features: 'unstable-simd,yyjson',
             rustflags: '-Z mir-opt-level=4 -C lto=fat -D warnings',
             target: 'powerpc64le-unknown-linux-gnu',
           },
           {
             arch: 's390x',
             cflags: '-Os -flto=full -fstrict-aliasing -march=z10',
-            features: 'no-panic,yyjson',
+            features: 'yyjson',
             rustflags: '-Z mir-opt-level=4 -C lto=fat -D warnings -C target-cpu=z10',
             target: 's390x-unknown-linux-gnu',
           },
@@ -389,7 +399,8 @@ jobs:
         retention-days: 1
 
   macos_aarch64:
-    runs-on: macos-14
+    runs-on: macos-15
+    timeout-minutes: 10
     strategy:
       fail-fast: false
       matrix:
@@ -414,7 +425,6 @@ jobs:
     - uses: actions/setup-python@v5
       with:
         python-version: "${{ matrix.python.version }}"
-        allow-prereleases: true
 
     - uses: dtolnay/rust-toolchain@master
       with:
@@ -426,6 +436,8 @@ jobs:
       run: |
         cargo fetch --target aarch64-apple-darwin &
 
+        export PATH=$HOME/.cargo/bin:$HOME/.local/bin:$PATH
+
         curl -LsSf https://astral.sh/uv/install.sh | sh
         uv venv --python python${{ matrix.python.version }}
         uv pip install --upgrade "maturin>=1,<2" -r test/requirements.txt -r integration/requirements.txt
@@ -435,11 +447,12 @@ jobs:
 
     - name: maturin
       run: |
-        PATH=$HOME/.cargo/bin:$PATH \
+        export PATH=$HOME/.cargo/bin:$HOME/.local/bin:$PATH
+
         MACOSX_DEPLOYMENT_TARGET="${{ matrix.python.macosx_target }}" \
         PYO3_CROSS_LIB_DIR=$(python -c "import sysconfig;print(sysconfig.get_config_var('LIBDIR'))") \
         maturin build --release --strip \
-          --features=no-panic,unstable-simd,yyjson \
+          --features=unstable-simd,yyjson \
           --interpreter python${{ matrix.python.version }} \
           --target=universal2-apple-darwin
         uv pip install target/wheels/orjson*.whl
@@ -463,6 +476,7 @@ jobs:
 
   macos_amd64:
     runs-on: macos-13
+    timeout-minutes: 10
     strategy:
       fail-fast: false
       matrix:
@@ -496,6 +510,8 @@ jobs:
       run: |
         cargo fetch --target aarch64-apple-darwin &
 
+        export PATH=$HOME/.cargo/bin:$HOME/.local/bin:$PATH
+
         curl -LsSf https://astral.sh/uv/install.sh | sh
         uv venv --python python${{ matrix.python.version }}
         uv pip install --upgrade "maturin>=1,<2" -r test/requirements.txt -r integration/requirements.txt
@@ -505,11 +521,12 @@ jobs:
 
     - name: maturin
       run: |
-        PATH=$HOME/.cargo/bin:$PATH \
+        export PATH=$HOME/.cargo/bin:$HOME/.local/bin:$PATH
+
         MACOSX_DEPLOYMENT_TARGET="${{ matrix.python.macosx_target }}" \
         PYO3_CROSS_LIB_DIR=$(python -c "import sysconfig;print(sysconfig.get_config_var('LIBDIR'))") \
         maturin build --release --strip \
-          --features=no-panic,unstable-simd,yyjson \
+          --features=unstable-simd,yyjson \
           --interpreter python${{ matrix.python.version }} \
           --target=universal2-apple-darwin
         uv pip install target/wheels/orjson*.whl
@@ -531,9 +548,75 @@ jobs:
         overwrite: true
         retention-days: 1
 
+  windows:
+    runs-on: windows-2022
+    timeout-minutes: 10
+    strategy:
+      fail-fast: false
+      matrix:
+        python: [
+          { version: '3.13' },
+          { version: '3.12' },
+          { version: '3.11' },
+          { version: '3.10' },
+          { version: '3.9' },
+          { version: '3.8' },
+        ]
+        platform: [
+          { arch: "x64", target: "x86_64-pc-windows-msvc" },
+          { arch: "x86", target: "i686-pc-windows-msvc" },
+        ]
+    env:
+      CFLAGS: "-Os"
+      LDFLAGS: "-Wl,--as-needed"
+      RUSTFLAGS: "-C lto=fat -Z mir-opt-level=4 -D warnings"
+    steps:
+
+    - uses: actions/checkout@v4
+
+    - uses: actions/setup-python@v5
+      with:
+        python-version: "${{ matrix.python.version }}"
+        architecture: "${{ matrix.platform.arch }}"
+
+    - uses: dtolnay/rust-toolchain@master
+      with:
+        toolchain: "${{ env.RUST_TOOLCHAIN }}"
+        targets: "${{ matrix.platform.target }}"
+        components: "rust-src"
+
+    - name: Build environment
+      run: |
+        cargo fetch --target "${{ matrix.platform.target }}" &
+
+        python.exe -m pip install --upgrade pip "maturin>=1,<2" wheel
+        python.exe -m pip install -r test\requirements.txt -r integration\requirements.txt
+
+        mkdir .cargo
+        cp ci\config.toml .cargo\config.toml
+
+    - name: maturin
+      run: |
+        maturin.exe build --release --strip --features=unstable-simd,yyjson --target="${{ matrix.platform.target }}"
+        python.exe -m pip install orjson --no-index --find-links target\wheels
+
+    - run: python.exe -m pytest -s -rxX -v test
+      env:
+        PYTHONMALLOC: "debug"
+
+    - name: Store wheels
+      if: "startsWith(github.ref, 'refs/tags/')"
+      uses: actions/upload-artifact@v4
+      with:
+        name: orjson_windows_${{ matrix.platform.arch }}_${{ matrix.python.version }}
+        path: target\wheels
+        overwrite: true
+        retention-days: 1
+
   pypi:
     name: PyPI
     runs-on: ubuntu-24.04
+    timeout-minutes: 10
     if: "startsWith(github.ref, 'refs/tags/')"
     needs: [
       macos_aarch64,
@@ -543,6 +626,7 @@ jobs:
       manylinux_non_amd64,
       musllinux,
       sdist,
+      windows,
     ]
     environment:
       name: pypi
diff --git a/Cargo.lock b/Cargo.lock
index fde9db8d..0910646c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -25,9 +25,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.1.31"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c2e7962b54006dcfcc61cb72735f4d89bb97061dd6a7ed882ec6b8ee53714c6f"
+checksum = "fd9de9f2205d5ef3fd67e685b0df337994ddd4495e2a28d185500d0e1edfea47"
 dependencies = [
  "shlex",
 ]
@@ -89,9 +89,6 @@ name = "itoa"
 version = "1.0.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49f1f14873335454500d59611f1cf4a4b0f786f9ac11f4312a78e4cf2566695b"
-dependencies = [
- "no-panic",
-]
 
 [[package]]
 name = "itoap"
@@ -107,9 +104,9 @@ checksum = "b9d9d414fc817d3e3d62b2598616733f76c4cc74fbac96069674739b881295c8"
 
 [[package]]
 name = "libc"
-version = "0.2.161"
+version = "0.2.162"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8e9489c2807c139ffd9c1794f4af0ebe86a828db53ecdc7fea2111d0fed085d1"
+checksum = "18d287de67fe55fd7e1581fe933d965a5a9477b38e949cfa9f8574ef01506398"
 
 [[package]]
 name = "memchr"
@@ -117,17 +114,6 @@ version = "2.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
 
-[[package]]
-name = "no-panic"
-version = "0.1.30"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8540b7d99a20166178b42a05776aef900cdbfec397f861dfc7819bf1d7760b3d"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
-
 [[package]]
 name = "once_cell"
 version = "1.20.2"
@@ -206,24 +192,21 @@ name = "ryu"
 version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f3cb5ba0dc43242ce17de99c180e96db90b235b8a9fdc9543c96d2209116bd9f"
-dependencies = [
- "no-panic",
-]
 
 [[package]]
 name = "serde"
-version = "1.0.214"
+version = "1.0.215"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f55c3193aca71c12ad7890f1785d2b73e1b9f63a0bbc353c08ef26fe03fc56b5"
+checksum = "6513c1ad0b11a9376da888e3e0baa0077f1aed55c17f50e7b2397136129fb88f"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.214"
+version = "1.0.215"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "de523f781f095e28fa605cdce0f8307e451cc0fd14e2eb4cd2e98a355b147766"
+checksum = "ad1e866f866923f252f05c889987993144fb74e722403468a4ebd70c3cd756c0"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -268,9 +251,9 @@ checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
 
 [[package]]
 name = "syn"
-version = "2.0.86"
+version = "2.0.87"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e89275301d38033efb81a6e60e3497e734dfcc62571f2854bf4b16690398824c"
+checksum = "25aa4ce346d03a6dcd68dd8b4010bcb74e54e62c90c573f394c46eae99aba32d"
 dependencies = [
  "proc-macro2",
  "quote",
diff --git a/Cargo.toml b/Cargo.toml
index 516f4d0e..418df3f1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -38,11 +38,6 @@ unstable-simd = []
 # Include runtime-detected functions that use AVX512VL. Requires unstable-simd and amd64.
 avx512 = []
 
-no-panic = [
-    "itoa/no-panic",
-    "ryu/no-panic",
-]
-
 # Avoid bundling libgcc on musl.
 unwind = ["unwinding"]
 
@@ -51,6 +46,7 @@ unwind = ["unwinding"]
 yyjson = []
 
 # Features detected by build.rs. Do not specify.
+assert_unchecked = []
 inline_int = []
 intrinsics = []
 optimize = []
diff --git a/README.md b/README.md
index 942597ef..b8f84bbb 100644
--- a/README.md
+++ b/README.md
@@ -34,8 +34,8 @@ file-like objects
 
 orjson supports CPython 3.8, 3.9, 3.10, 3.11, 3.12, 3.13, and 3.14.
 
-It distributes amd64/x86_64, aarch64/armv8, arm7, POWER/ppc64le, and s390x
-wheels for Linux, amd64 and aarch64 wheels for macOS, and amd64
+It distributes amd64/x86_64, i686/x86, aarch64/armv8, arm7, POWER/ppc64le,
+and s390x wheels for Linux, amd64 and aarch64 wheels for macOS, and amd64
 and i686/x86 wheels for Windows.
 
 orjson does not and will not support PyPy, embedded Python builds for
@@ -72,8 +72,7 @@ available in the repository.
 3. [Testing](https://github.com/ijl/orjson?tab=readme-ov-file#testing)
 4. [Performance](https://github.com/ijl/orjson?tab=readme-ov-file#performance)
     1. [Latency](https://github.com/ijl/orjson?tab=readme-ov-file#latency)
-    2. [Memory](https://github.com/ijl/orjson?tab=readme-ov-file#memory)
-    3. [Reproducing](https://github.com/ijl/orjson?tab=readme-ov-file#reproducing)
+    2. [Reproducing](https://github.com/ijl/orjson?tab=readme-ov-file#reproducing)
 5. [Questions](https://github.com/ijl/orjson?tab=readme-ov-file#questions)
 6. [Packaging](https://github.com/ijl/orjson?tab=readme-ov-file#packaging)
 7. [License](https://github.com/ijl/orjson?tab=readme-ov-file#license)
@@ -1120,64 +1119,13 @@ format, containing floats and arrays, indented.
 | simplejson |                            16.8 |                      59 |                  5.6 |
 | json       |                            18.2 |                      55 |                  6.1 |
 
-### Memory
-
-orjson as of 3.7.0 has higher baseline memory usage than other libraries
-due to a persistent buffer used for parsing. Incremental memory usage when
-deserializing is similar to the standard library and other third-party
-libraries.
-
-This measures, in the first column, RSS after importing a library and reading
-the fixture, and in the second column, increases in RSS after repeatedly
-calling `loads()` on the fixture.
-
-#### twitter.json
-
-| Library    |   import, read() RSS (MiB) |   loads() increase in RSS (MiB) |
-|------------|----------------------------|---------------------------------|
-| orjson     |                       15.7 |                             3.4 |
-| ujson      |                       16.4 |                             3.4 |
-| rapidjson  |                       16.6 |                             4.4 |
-| simplejson |                       14.5 |                             1.8 |
-| json       |                       13.9 |                             1.8 |
-
-#### github.json
-
-| Library    |   import, read() RSS (MiB) |   loads() increase in RSS (MiB) |
-|------------|----------------------------|---------------------------------|
-| orjson     |                       15.2 |                             0.4 |
-| ujson      |                       15.4 |                             0.4 |
-| rapidjson  |                       15.7 |                             0.5 |
-| simplejson |                       13.7 |                             0.2 |
-| json       |                       13.3 |                             0.1 |
-
-#### citm_catalog.json
-
-| Library    |   import, read() RSS (MiB) |   loads() increase in RSS (MiB) |
-|------------|----------------------------|---------------------------------|
-| orjson     |                       16.8 |                            10.1 |
-| ujson      |                       17.3 |                            10.2 |
-| rapidjson  |                       17.6 |                            28.7 |
-| simplejson |                       15.8 |                            30.1 |
-| json       |                       14.8 |                            20.5 |
-
-#### canada.json
-
-| Library    |   import, read() RSS (MiB) |   loads() increase in RSS (MiB) |
-|------------|----------------------------|---------------------------------|
-| orjson     |                       17.2 |                            22.1 |
-| ujson      |                       17.4 |                            18.3 |
-| rapidjson  |                       18   |                            23.5 |
-| simplejson |                       15.7 |                            21.4 |
-| json       |                       15.4 |                            20.4 |
-
 ### Reproducing
 
 The above was measured using Python 3.11.9 on Linux (amd64) with
 orjson 3.10.6, ujson 5.10.0, python-rapidson 1.18, and simplejson 3.19.2.
 
 The latency results can be reproduced using the `pybench` and `graph`
-scripts. The memory results can be reproduced using the `pymem` script.
+scripts.
 
 ## Questions
 
@@ -1226,10 +1174,11 @@ example using clang and LTO.
 
 The project's own CI tests against `nightly-2024-09-25` and stable 1.72. It
 is prudent to pin the nightly version because that channel can introduce
-breaking changes.
+breaking changes. There is a significant performance benefit to using
+nightly.
 
-orjson is tested for amd64 on Linux and cross-compiles for aarch64, arm7,
-ppc64le, and s390x. It is tested for either aarch64 or amd64 on macOS and
+orjson is tested for amd64, aarch64, and i686 on Linux and cross-compiles for
+arm7, ppc64le, and s390x. It is tested for either aarch64 or amd64 on macOS and
 cross-compiles for the other, depending on version. For Windows it is
 tested on amd64 and i686.
 
diff --git a/build.rs b/build.rs
index ad6d5b9c..c6a82e67 100644
--- a/build.rs
+++ b/build.rs
@@ -36,6 +36,10 @@ fn main() {
         println!("cargo:rustc-cfg=feature=\"optimize\"");
     }
 
+    if let Some(true) = version_check::supports_feature("hint_assert_unchecked") {
+        println!("cargo:rustc-cfg=feature=\"assert_unchecked\"");
+    }
+
     #[cfg(any(target_arch = "x86_64", target_arch = "aarch64"))]
     if env::var("ORJSON_DISABLE_SIMD").is_err() {
         // auto build unstable SIMD on nightly
@@ -51,12 +55,10 @@ fn main() {
         }
     }
 
-    #[cfg(all(
-        target_pointer_width = "64",
-        any(target_arch = "x86_64", target_arch = "aarch64")
-    ))]
-    println!("cargo:rustc-cfg=feature=\"inline_int\"");
-
+    #[cfg(any(target_arch = "x86_64", target_arch = "aarch64"))]
+    if let Some(64) = python_config.pointer_width {
+        println!("cargo:rustc-cfg=feature=\"inline_int\"");
+    }
     if env::var("ORJSON_DISABLE_YYJSON").is_ok() {
         if env::var("CARGO_FEATURE_YYJSON").is_ok() {
             panic!("ORJSON_DISABLE_YYJSON and --features=yyjson both enabled.")
diff --git a/ci/azure-pipelines.yml b/ci/azure-pipelines.yml
deleted file mode 100644
index 8382734e..00000000
--- a/ci/azure-pipelines.yml
+++ /dev/null
@@ -1,196 +0,0 @@
-variables:
-  toolchain: nightly-2024-09-25
-
-jobs:
-
-- job: win_python313_amd64
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.13.0\x64\python.exe
-    rustup: https://win.rustup.rs/x86_64
-    target: x86_64-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.13.0'
-      addToPath: true
-      architecture: 'x64'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python312_amd64
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.12.2\x64\python.exe
-    rustup: https://win.rustup.rs/x86_64
-    target: x86_64-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.12.2'
-      addToPath: true
-      architecture: 'x64'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python311_amd64
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.11.4\x64\python.exe
-    rustup: https://win.rustup.rs/x86_64
-    target: x86_64-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.11.4'
-      addToPath: true
-      architecture: 'x64'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python310_amd64
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.10.8\x64\python.exe
-    rustup: https://win.rustup.rs/x86_64
-    target: x86_64-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.10.8'
-      addToPath: true
-      architecture: 'x64'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python39_amd64
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.9.13\x64\python.exe
-    rustup: https://win.rustup.rs/x86_64
-    target: x86_64-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.9.13'
-      addToPath: true
-      architecture: 'x64'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python38_amd64
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.8.10\x64\python.exe
-    rustup: https://win.rustup.rs/x86_64
-    target: x86_64-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.8.10'
-      addToPath: true
-      architecture: 'x64'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python313_x86
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.13.0\x86\python.exe
-    rustup: https://win.rustup.rs/x86
-    target: i686-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.13.0'
-      addToPath: true
-      architecture: 'x86'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python312_x86
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.12.2\x86\python.exe
-    rustup: https://win.rustup.rs/x86
-    target: i686-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.12.2'
-      addToPath: true
-      architecture: 'x86'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python311_x86
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.11.4\x86\python.exe
-    rustup: https://win.rustup.rs/x86
-    target: i686-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.11.4'
-      addToPath: true
-      architecture: 'x86'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python310_x86
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.10.8\x86\python.exe
-    rustup: https://win.rustup.rs/x86
-    target: i686-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.10.8'
-      addToPath: true
-      architecture: 'x86'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python39_x86
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.9.13\x86\python.exe
-    rustup: https://win.rustup.rs/x86
-    target: i686-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.9.13'
-      addToPath: true
-      architecture: 'x86'
-  - checkout: self
-  - template: ./azure-win.yml
-
-- job: win_python38_x86
-  pool:
-    vmImage: windows-2022
-  variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.8.10\x86\python.exe
-    rustup: https://win.rustup.rs/x86
-    target: i686-pc-windows-msvc
-  steps:
-  - task: UsePythonVersion@0
-    inputs:
-      versionSpec: '3.8.10'
-      addToPath: true
-      architecture: 'x86'
-  - checkout: self
-  - template: ./azure-win.yml
diff --git a/ci/azure-win.yml b/ci/azure-win.yml
deleted file mode 100644
index 655eab96..00000000
--- a/ci/azure-win.yml
+++ /dev/null
@@ -1,41 +0,0 @@
-parameters:
-  interpreter: ''
-  rustup: ''
-  target: ''
-  toolchain: ''
-
-steps:
-- script: |
-    curl $(rustup) -o rustup-init.exe
-    rustup-init.exe -y --default-host $(target) --default-toolchain $(toolchain)-$(target) --profile minimal
-    set PATH=%PATH%;%USERPROFILE%\.cargo\bin
-    rustup default $(toolchain)-$(target)
-    rustup component add rust-src
-    mkdir .cargo
-    cp ci/config.toml .cargo/config.toml
-    echo "##vso[task.setvariable variable=PATH;]%PATH%;%USERPROFILE%\.cargo\bin"
-  displayName: rustup
-- script: python.exe -m pip install --upgrade pip "maturin>=1,<2" wheel
-  displayName: build dependencies
-- script: python.exe -m pip install -r test\requirements.txt -r integration\requirements.txt
-  displayName: test dependencies
-- script: maturin.exe build --release --features=no-panic,unstable-simd,yyjson --strip --interpreter $(interpreter) --target $(target)
-  displayName: build
-  env:
-    CFLAGS: "-Os -flto"
-    LDFLAGS: "-Wl,--as-needed"
-    RUSTFLAGS: "-C lto=fat -Z mir-opt-level=4 -D warnings"
-    CARGO_UNSTABLE_SPARSE_REGISTRY: "true"
-    UNSAFE_PYO3_SKIP_VERSION_CHECK: "1"
-- script: python.exe -m pip install orjson --no-index --find-links=D:\a\1\s\target\wheels
-  displayName: install
-- script: python.exe -m pytest -s -rxX -v test
-  env:
-    PYTHONMALLOC: "debug"
-  displayName: pytest
-- script: python.exe integration\thread
-  displayName: thread
-- script: python.exe integration\init
-  displayName: init
-- bash: ./ci/deploy /d/a/1/s/target/wheels/*.whl
-  displayName: deploy
diff --git a/ci/deploy b/ci/deploy
deleted file mode 100755
index 1b34b539..00000000
--- a/ci/deploy
+++ /dev/null
@@ -1,18 +0,0 @@
-#!/usr/bin/env bash
-
-set -eou pipefail
-
-if [ -z ${DRONE_TAG+x} ]; then
-    tag=$(git name-rev --tags --name-only $(git rev-parse HEAD))
-else
-    tag="$DRONE_TAG"
-fi
-
-echo "$tag"
-
-if [[ "$tag" == "undefined" ]]; then
-    echo "not on a tag"
-    exit 0
-fi
-
-maturin upload --skip-existing "$1"
diff --git a/include/pyo3/pyo3-build-config/src/impl_.rs b/include/pyo3/pyo3-build-config/src/impl_.rs
index ec652591..6d232642 100644
--- a/include/pyo3/pyo3-build-config/src/impl_.rs
+++ b/include/pyo3/pyo3-build-config/src/impl_.rs
@@ -248,6 +248,7 @@ print("executable", sys.executable)
 print("calcsize_pointer", struct.calcsize("P"))
 print("mingw", get_platform().startswith("mingw"))
 print("ext_suffix", get_config_var("EXT_SUFFIX"))
+print("gil_disabled", get_config_var("Py_GIL_DISABLED"))
 "#;
         let output = run_python_script(interpreter.as_ref(), SCRIPT)?;
         let map: HashMap<String, String> = parse_script_output(&output);
@@ -290,6 +291,13 @@ print("ext_suffix", get_config_var("EXT_SUFFIX"))
 
         let implementation = map["implementation"].parse()?;
 
+        let gil_disabled = match map["gil_disabled"].as_str() {
+            "1" => true,
+            "0" => false,
+            "None" => false,
+            _ => panic!("Unknown Py_GIL_DISABLED value"),
+        };
+
         let lib_name = if cfg!(windows) {
             default_lib_name_windows(
                 version,
@@ -300,12 +308,14 @@ print("ext_suffix", get_config_var("EXT_SUFFIX"))
                 // on Windows from sysconfig - e.g. ext_suffix may be
                 // `_d.cp312-win_amd64.pyd` for 3.12 debug build
                 map["ext_suffix"].starts_with("_d."),
+                gil_disabled,
             )
         } else {
             default_lib_name_unix(
                 version,
                 implementation,
                 map.get("ld_version").map(String::as_str),
+                gil_disabled,
             )
         };
 
@@ -375,10 +385,15 @@ print("ext_suffix", get_config_var("EXT_SUFFIX"))
             _ => false,
         };
         let lib_dir = get_key!(sysconfigdata, "LIBDIR").ok().map(str::to_string);
+        let gil_disabled = match sysconfigdata.get_value("Py_GIL_DISABLED") {
+            Some(value) => value == "1",
+            None => false,
+        };
         let lib_name = Some(default_lib_name_unix(
             version,
             implementation,
             sysconfigdata.get_value("LDVERSION"),
+            gil_disabled,
         ));
         let pointer_width = parse_key!(sysconfigdata, "SIZEOF_VOID_P")
             .map(|bytes_width: u32| bytes_width * 8)
@@ -1106,10 +1121,15 @@ impl BuildFlags {
     /// the interpreter and printing variables of interest from
     /// sysconfig.get_config_vars.
     fn from_interpreter(interpreter: impl AsRef<Path>) -> Result<Self> {
-        // sysconfig is missing all the flags on windows, so we can't actually
-        // query the interpreter directly for its build flags.
+        // sysconfig is missing all the flags on windows for Python 3.12 and
+        // older, so we can't actually query the interpreter directly for its
+        // build flags on those versions.
         if cfg!(windows) {
-            return Ok(Self::new());
+            let script = String::from("import sys;print(sys.version_info < (3, 13))");
+            let stdout = run_python_script(interpreter.as_ref(), &script)?;
+            if stdout.trim_end() == "True" {
+                return Ok(Self::new());
+            }
         }
 
         let mut script = String::from("import sysconfig\n");
@@ -1528,6 +1548,7 @@ fn default_abi3_config(host: &Triple, version: PythonVersion) -> InterpreterConf
             abi3,
             false,
             false,
+            false,
         ))
     } else {
         None
@@ -1604,9 +1625,10 @@ fn default_lib_name_for_target(
             abi3,
             false,
             false,
+            false,
         ))
     } else if is_linking_libpython_for_target(target) {
-        Some(default_lib_name_unix(version, implementation, None))
+        Some(default_lib_name_unix(version, implementation, None, false))
     } else {
         None
     }
@@ -1618,16 +1640,26 @@ fn default_lib_name_windows(
     abi3: bool,
     mingw: bool,
     debug: bool,
+    gil_disabled: bool,
 ) -> String {
     if debug {
         // CPython bug: linking against python3_d.dll raises error
         // https://github.com/python/cpython/issues/101614
-        format!("python{}{}_d", version.major, version.minor)
+        if gil_disabled {
+            format!("python{}{}t_d", version.major, version.minor)
+        } else {
+            format!("python{}{}_d", version.major, version.minor)
+        }
     } else if abi3 && !(implementation.is_pypy() || implementation.is_graalpy()) {
         WINDOWS_ABI3_LIB_NAME.to_owned()
     } else if mingw {
+        if gil_disabled {
+            panic!("MinGW free-threaded builds are not currently tested or supported")
+        }
         // https://packages.msys2.org/base/mingw-w64-python
         format!("python{}.{}", version.major, version.minor)
+    } else if gil_disabled {
+        format!("python{}{}t", version.major, version.minor)
     } else {
         format!("python{}{}", version.major, version.minor)
     }
@@ -1637,6 +1669,7 @@ fn default_lib_name_unix(
     version: PythonVersion,
     implementation: PythonImplementation,
     ld_version: Option<&str>,
+    gil_disabled: bool,
 ) -> String {
     match implementation {
         PythonImplementation::CPython => match ld_version {
@@ -1644,7 +1677,11 @@ fn default_lib_name_unix(
             None => {
                 if version > PythonVersion::PY37 {
                     // PEP 3149 ABI version tags are finally gone
-                    format!("python{}.{}", version.major, version.minor)
+                    if gil_disabled {
+                        format!("python{}.{}t", version.major, version.minor)
+                    } else {
+                        format!("python{}.{}", version.major, version.minor)
+                    }
                 } else {
                     // Work around https://bugs.python.org/issue36707
                     format!("python{}.{}m", version.major, version.minor)
@@ -2351,6 +2388,7 @@ mod tests {
                 false,
                 false,
                 false,
+                false,
             ),
             "python39",
         );
@@ -2361,6 +2399,7 @@ mod tests {
                 true,
                 false,
                 false,
+                false,
             ),
             "python3",
         );
@@ -2371,6 +2410,7 @@ mod tests {
                 false,
                 true,
                 false,
+                false,
             ),
             "python3.9",
         );
@@ -2381,6 +2421,7 @@ mod tests {
                 true,
                 true,
                 false,
+                false,
             ),
             "python3",
         );
@@ -2391,6 +2432,7 @@ mod tests {
                 true,
                 false,
                 false,
+                false,
             ),
             "python39",
         );
@@ -2401,6 +2443,7 @@ mod tests {
                 false,
                 false,
                 true,
+                false,
             ),
             "python39_d",
         );
@@ -2413,6 +2456,7 @@ mod tests {
                 true,
                 false,
                 true,
+                false,
             ),
             "python39_d",
         );
@@ -2423,16 +2467,31 @@ mod tests {
         use PythonImplementation::*;
         // Defaults to python3.7m for CPython 3.7
         assert_eq!(
-            super::default_lib_name_unix(PythonVersion { major: 3, minor: 7 }, CPython, None),
+            super::default_lib_name_unix(
+                PythonVersion { major: 3, minor: 7 },
+                CPython,
+                None,
+                false
+            ),
             "python3.7m",
         );
         // Defaults to pythonX.Y for CPython 3.8+
         assert_eq!(
-            super::default_lib_name_unix(PythonVersion { major: 3, minor: 8 }, CPython, None),
+            super::default_lib_name_unix(
+                PythonVersion { major: 3, minor: 8 },
+                CPython,
+                None,
+                false
+            ),
             "python3.8",
         );
         assert_eq!(
-            super::default_lib_name_unix(PythonVersion { major: 3, minor: 9 }, CPython, None),
+            super::default_lib_name_unix(
+                PythonVersion { major: 3, minor: 9 },
+                CPython,
+                None,
+                false
+            ),
             "python3.9",
         );
         // Can use ldversion to override for CPython
@@ -2440,19 +2499,25 @@ mod tests {
             super::default_lib_name_unix(
                 PythonVersion { major: 3, minor: 9 },
                 CPython,
-                Some("3.7md")
+                Some("3.7md"),
+                false
             ),
             "python3.7md",
         );
 
         // PyPy 3.9 includes ldversion
         assert_eq!(
-            super::default_lib_name_unix(PythonVersion { major: 3, minor: 9 }, PyPy, None),
+            super::default_lib_name_unix(PythonVersion { major: 3, minor: 9 }, PyPy, None, false),
             "pypy3.9-c",
         );
 
         assert_eq!(
-            super::default_lib_name_unix(PythonVersion { major: 3, minor: 9 }, PyPy, Some("3.9d")),
+            super::default_lib_name_unix(
+                PythonVersion { major: 3, minor: 9 },
+                PyPy,
+                Some("3.9d"),
+                false
+            ),
             "pypy3.9d-c",
         );
     }
diff --git a/include/pyo3/pyo3-build-config/src/lib.rs b/include/pyo3/pyo3-build-config/src/lib.rs
index 6e295c99..66f52031 100644
--- a/include/pyo3/pyo3-build-config/src/lib.rs
+++ b/include/pyo3/pyo3-build-config/src/lib.rs
@@ -138,6 +138,10 @@ fn resolve_cross_compile_config_path() -> Option<PathBuf> {
 pub fn print_feature_cfgs() {
     let rustc_minor_version = rustc_minor_version().unwrap_or(0);
 
+    if rustc_minor_version >= 70 {
+        println!("cargo:rustc-cfg=rustc_has_once_lock");
+    }
+
     // invalid_from_utf8 lint was added in Rust 1.74
     if rustc_minor_version >= 74 {
         println!("cargo:rustc-cfg=invalid_from_utf8_lint");
@@ -175,6 +179,7 @@ pub fn print_expected_cfgs() {
     println!("cargo:rustc-check-cfg=cfg(pyo3_leak_on_drop_without_reference_pool)");
     println!("cargo:rustc-check-cfg=cfg(diagnostic_namespace)");
     println!("cargo:rustc-check-cfg=cfg(c_str_lit)");
+    println!("cargo:rustc-check-cfg=cfg(rustc_has_once_lock)");
 
     // allow `Py_3_*` cfgs from the minimum supported version up to the
     // maximum minor version (+1 for development for the next)
diff --git a/include/pyo3/pyo3-ffi/src/compat/py_3_13.rs b/include/pyo3/pyo3-ffi/src/compat/py_3_13.rs
index 9f44ced6..59289cb7 100644
--- a/include/pyo3/pyo3-ffi/src/compat/py_3_13.rs
+++ b/include/pyo3/pyo3-ffi/src/compat/py_3_13.rs
@@ -83,3 +83,24 @@ compat_function!(
         1
     }
 );
+
+compat_function!(
+    originally_defined_for(Py_3_13);
+
+    #[inline]
+    pub unsafe fn PyList_Extend(
+        list: *mut crate::PyObject,
+        iterable: *mut crate::PyObject,
+    ) -> std::os::raw::c_int {
+        crate::PyList_SetSlice(list, crate::PY_SSIZE_T_MAX, crate::PY_SSIZE_T_MAX, iterable)
+    }
+);
+
+compat_function!(
+    originally_defined_for(Py_3_13);
+
+    #[inline]
+    pub unsafe fn PyList_Clear(list: *mut crate::PyObject) -> std::os::raw::c_int {
+        crate::PyList_SetSlice(list, 0, crate::PY_SSIZE_T_MAX, std::ptr::null_mut())
+    }
+);
diff --git a/include/pyo3/pyo3-ffi/src/cpython/critical_section.rs b/include/pyo3/pyo3-ffi/src/cpython/critical_section.rs
index 97b2f5e0..3760d224 100644
--- a/include/pyo3/pyo3-ffi/src/cpython/critical_section.rs
+++ b/include/pyo3/pyo3-ffi/src/cpython/critical_section.rs
@@ -9,6 +9,27 @@ pub struct PyCriticalSection {
     _cs_mutex: *mut PyMutex,
 }
 
+// #[cfg(Py_GIL_DISABLED)]
+// impl Default for PyCriticalSection {
+//     fn default() -> Self {
+//         let mut mutex = crate::PyMutex::new();
+//         PyCriticalSection {
+//             _cs_prev: 0,
+//             _cs_mutex: core::ptr::addr_of_mut!(mutex),
+//         }
+//     }
+// }
+
+#[cfg(Py_GIL_DISABLED)]
+impl Default for PyCriticalSection {
+    fn default() -> Self {
+        PyCriticalSection {
+            _cs_prev: 0,
+            _cs_mutex: core::ptr::null_mut(),
+        }
+    }
+}
+
 #[repr(C)]
 #[cfg(Py_GIL_DISABLED)]
 pub struct PyCriticalSection2 {
diff --git a/include/pyo3/pyo3-ffi/src/cpython/dictobject.rs b/include/pyo3/pyo3-ffi/src/cpython/dictobject.rs
index 79dcbfdb..f67a7725 100644
--- a/include/pyo3/pyo3-ffi/src/cpython/dictobject.rs
+++ b/include/pyo3/pyo3-ffi/src/cpython/dictobject.rs
@@ -36,6 +36,15 @@ extern "C" {
         item: *mut PyObject,
         hash: crate::Py_hash_t,
     ) -> c_int;
+
+    #[cfg(Py_3_13)]
+    pub fn _PyDict_SetItem_KnownHash_LockHeld(
+        mp: *mut PyDictObject,
+        name: *mut PyObject,
+        value: *mut PyObject,
+        hash: crate::Py_hash_t,
+    ) -> c_int;
+
     // skipped _PyDict_DelItem_KnownHash
     // skipped _PyDict_DelItemIf
     // skipped _PyDict_NewKeysForClass
diff --git a/include/pyo3/pyo3-ffi/src/datetime.rs b/include/pyo3/pyo3-ffi/src/datetime.rs
index 7283b6d4..76d12151 100644
--- a/include/pyo3/pyo3-ffi/src/datetime.rs
+++ b/include/pyo3/pyo3-ffi/src/datetime.rs
@@ -4,16 +4,17 @@
 //! and covers the various date and time related objects in the Python `datetime`
 //! standard library module.
 
+#[cfg(not(PyPy))]
+use crate::PyCapsule_Import;
 #[cfg(GraalPy)]
 use crate::{PyLong_AsLong, PyLong_Check, PyObject_GetAttrString, Py_DecRef};
 use crate::{PyObject, PyObject_TypeCheck, PyTypeObject, Py_TYPE};
-use std::cell::UnsafeCell;
 #[cfg(not(GraalPy))]
 use std::os::raw::c_char;
 use std::os::raw::c_int;
 use std::ptr;
-#[cfg(not(PyPy))]
-use {crate::PyCapsule_Import, std::ffi::CString};
+use std::sync::Once;
+use std::{cell::UnsafeCell, ffi::CStr};
 #[cfg(not(any(PyPy, GraalPy)))]
 use {crate::Py_hash_t, std::os::raw::c_uchar};
 // Type struct wrappers
@@ -593,6 +594,8 @@ pub struct PyDateTime_CAPI {
 // Python already shares this object between threads, so it's no more evil for us to do it too!
 unsafe impl Sync for PyDateTime_CAPI {}
 
+pub const PyDateTime_CAPSULE_NAME: &CStr = c_str!("datetime.datetime_CAPI");
+
 /// Returns a pointer to a `PyDateTime_CAPI` instance
 ///
 /// # Note
@@ -600,33 +603,38 @@ unsafe impl Sync for PyDateTime_CAPI {}
 /// `PyDateTime_IMPORT` is called
 #[inline]
 pub unsafe fn PyDateTimeAPI() -> *mut PyDateTime_CAPI {
-    *PyDateTimeAPI_impl.0.get()
-}
-
-#[inline]
-pub unsafe fn PyDateTime_TimeZone_UTC() -> *mut PyObject {
-    (*PyDateTimeAPI()).TimeZone_UTC
+    *PyDateTimeAPI_impl.ptr.get()
 }
 
 /// Populates the `PyDateTimeAPI` object
 pub unsafe fn PyDateTime_IMPORT() {
-    // PyPy expects the C-API to be initialized via PyDateTime_Import, so trying to use
-    // `PyCapsule_Import` will behave unexpectedly in pypy.
-    #[cfg(PyPy)]
-    let py_datetime_c_api = PyDateTime_Import();
-
-    #[cfg(not(PyPy))]
-    let py_datetime_c_api = {
-        // PyDateTime_CAPSULE_NAME is a macro in C
-        let PyDateTime_CAPSULE_NAME = CString::new("datetime.datetime_CAPI").unwrap();
-
-        PyCapsule_Import(PyDateTime_CAPSULE_NAME.as_ptr(), 1) as *mut PyDateTime_CAPI
-    };
+    if !PyDateTimeAPI_impl.once.is_completed() {
+        // PyPy expects the C-API to be initialized via PyDateTime_Import, so trying to use
+        // `PyCapsule_Import` will behave unexpectedly in pypy.
+        #[cfg(PyPy)]
+        let py_datetime_c_api = PyDateTime_Import();
+
+        #[cfg(not(PyPy))]
+        let py_datetime_c_api =
+            PyCapsule_Import(PyDateTime_CAPSULE_NAME.as_ptr(), 1) as *mut PyDateTime_CAPI;
+
+        if py_datetime_c_api.is_null() {
+            return;
+        }
 
-    *PyDateTimeAPI_impl.0.get() = py_datetime_c_api;
+        // Protect against race conditions when the datetime API is concurrently
+        // initialized in multiple threads. UnsafeCell.get() cannot panic so this
+        // won't panic either.
+        PyDateTimeAPI_impl.once.call_once(|| {
+            *PyDateTimeAPI_impl.ptr.get() = py_datetime_c_api;
+        });
+    }
 }
 
-// skipped non-limited PyDateTime_TimeZone_UTC
+#[inline]
+pub unsafe fn PyDateTime_TimeZone_UTC() -> *mut PyObject {
+    (*PyDateTimeAPI()).TimeZone_UTC
+}
 
 /// Type Check macros
 ///
@@ -739,8 +747,13 @@ extern "C" {
 
 // Rust specific implementation details
 
-struct PyDateTimeAPISingleton(UnsafeCell<*mut PyDateTime_CAPI>);
+struct PyDateTimeAPISingleton {
+    once: Once,
+    ptr: UnsafeCell<*mut PyDateTime_CAPI>,
+}
 unsafe impl Sync for PyDateTimeAPISingleton {}
 
-static PyDateTimeAPI_impl: PyDateTimeAPISingleton =
-    PyDateTimeAPISingleton(UnsafeCell::new(ptr::null_mut()));
+static PyDateTimeAPI_impl: PyDateTimeAPISingleton = PyDateTimeAPISingleton {
+    once: Once::new(),
+    ptr: UnsafeCell::new(ptr::null_mut()),
+};
diff --git a/include/pyo3/pyo3-ffi/src/lib.rs b/include/pyo3/pyo3-ffi/src/lib.rs
index c6157401..2d0436ab 100644
--- a/include/pyo3/pyo3-ffi/src/lib.rs
+++ b/include/pyo3/pyo3-ffi/src/lib.rs
@@ -43,10 +43,39 @@
 //! PyO3 uses `rustc`'s `--cfg` flags to enable or disable code used for different Python versions.
 //! If you want to do this for your own crate, you can do so with the [`pyo3-build-config`] crate.
 //!
-//! - `Py_3_7`, `Py_3_8`, `Py_3_9`, `Py_3_10`: Marks code that is only enabled when
-//!  compiling for a given minimum Python version.
+//! - `Py_3_7`, `Py_3_8`, `Py_3_9`, `Py_3_10`, `Py_3_11`, `Py_3_12`, `Py_3_13`: Marks code that is
+//!    only enabled when compiling for a given minimum Python version.
 //! - `Py_LIMITED_API`: Marks code enabled when the `abi3` feature flag is enabled.
+//! - `Py_GIL_DISABLED`: Marks code that runs only in the free-threaded build of CPython.
 //! - `PyPy` - Marks code enabled when compiling for PyPy.
+//! - `GraalPy` - Marks code enabled when compiling for GraalPy.
+//!
+//! Additionally, you can query for the values `Py_DEBUG`, `Py_REF_DEBUG`,
+//! `Py_TRACE_REFS`, and `COUNT_ALLOCS` from `py_sys_config` to query for the
+//! corresponding C build-time defines. For example, to conditionally define
+//! debug code using `Py_DEBUG`, you could do:
+//!
+//! ```rust,ignore
+//! #[cfg(py_sys_config = "Py_DEBUG")]
+//! println!("only runs if python was compiled with Py_DEBUG")
+//! ```
+//!
+//! To use these attributes, add [`pyo3-build-config`] as a build dependency in
+//! your `Cargo.toml`:
+//!
+//! ```toml
+//! [build-dependencies]
+#![doc = concat!("pyo3-build-config =\"", env!("CARGO_PKG_VERSION"),  "\"")]
+//! ```
+//!
+//! And then either create a new `build.rs` file in the project root or modify
+//! the existing `build.rs` file to call `use_pyo3_cfgs()`:
+//!
+//! ```rust,ignore
+//! fn main() {
+//!     pyo3_build_config::use_pyo3_cfgs();
+//! }
+//! ```
 //!
 //! # Minimum supported Rust and Python versions
 //!
@@ -79,101 +108,23 @@
 //! [dependencies.pyo3-ffi]
 #![doc = concat!("version = \"", env!("CARGO_PKG_VERSION"),  "\"")]
 //! features = ["extension-module"]
+//!
+//! [build-dependencies]
+//! # This is only necessary if you need to configure your build based on
+//! # the Python version or the compile-time configuration for the interpreter.
+#![doc = concat!("pyo3_build_config = \"", env!("CARGO_PKG_VERSION"),  "\"")]
 //! ```
 //!
-//! **`src/lib.rs`**
-//! ```rust
-//! use std::os::raw::c_char;
-//! use std::ptr;
-//!
-//! use pyo3_ffi::*;
-//!
-//! static mut MODULE_DEF: PyModuleDef = PyModuleDef {
-//!     m_base: PyModuleDef_HEAD_INIT,
-//!     m_name: c_str!("string_sum").as_ptr(),
-//!     m_doc: c_str!("A Python module written in Rust.").as_ptr(),
-//!     m_size: 0,
-//!     m_methods: unsafe { METHODS.as_mut_ptr().cast() },
-//!     m_slots: std::ptr::null_mut(),
-//!     m_traverse: None,
-//!     m_clear: None,
-//!     m_free: None,
-//! };
-//!
-//! static mut METHODS: [PyMethodDef; 2] = [
-//!     PyMethodDef {
-//!         ml_name: c_str!("sum_as_string").as_ptr(),
-//!         ml_meth: PyMethodDefPointer {
-//!             PyCFunctionFast: sum_as_string,
-//!         },
-//!         ml_flags: METH_FASTCALL,
-//!         ml_doc: c_str!("returns the sum of two integers as a string").as_ptr(),
-//!     },
-//!     // A zeroed PyMethodDef to mark the end of the array.
-//!     PyMethodDef::zeroed()
-//! ];
-//!
-//! // The module initialization function, which must be named `PyInit_<your_module>`.
-//! #[allow(non_snake_case)]
-//! #[no_mangle]
-//! pub unsafe extern "C" fn PyInit_string_sum() -> *mut PyObject {
-//!     PyModule_Create(ptr::addr_of_mut!(MODULE_DEF))
-//! }
+//! If you need to use conditional compilation based on Python version or how
+//! Python was compiled, you need to add `pyo3-build-config` as a
+//! `build-dependency` in your `Cargo.toml` as in the example above and either
+//! create a new `build.rs` file or modify an existing one so that
+//! `pyo3_build_config::use_pyo3_cfgs()` gets called at build time:
 //!
-//! pub unsafe extern "C" fn sum_as_string(
-//!     _self: *mut PyObject,
-//!     args: *mut *mut PyObject,
-//!     nargs: Py_ssize_t,
-//! ) -> *mut PyObject {
-//!     if nargs != 2 {
-//!         PyErr_SetString(
-//!             PyExc_TypeError,
-//!             c_str!("sum_as_string() expected 2 positional arguments").as_ptr(),
-//!         );
-//!         return std::ptr::null_mut();
-//!     }
-//!
-//!     let arg1 = *args;
-//!     if PyLong_Check(arg1) == 0 {
-//!         PyErr_SetString(
-//!             PyExc_TypeError,
-//!             c_str!("sum_as_string() expected an int for positional argument 1").as_ptr(),
-//!         );
-//!         return std::ptr::null_mut();
-//!     }
-//!
-//!     let arg1 = PyLong_AsLong(arg1);
-//!     if !PyErr_Occurred().is_null() {
-//!         return ptr::null_mut();
-//!     }
-//!
-//!     let arg2 = *args.add(1);
-//!     if PyLong_Check(arg2) == 0 {
-//!         PyErr_SetString(
-//!             PyExc_TypeError,
-//!             c_str!("sum_as_string() expected an int for positional argument 2").as_ptr(),
-//!         );
-//!         return std::ptr::null_mut();
-//!     }
-//!
-//!     let arg2 = PyLong_AsLong(arg2);
-//!     if !PyErr_Occurred().is_null() {
-//!         return ptr::null_mut();
-//!     }
-//!
-//!     match arg1.checked_add(arg2) {
-//!         Some(sum) => {
-//!             let string = sum.to_string();
-//!             PyUnicode_FromStringAndSize(string.as_ptr().cast::<c_char>(), string.len() as isize)
-//!         }
-//!         None => {
-//!             PyErr_SetString(
-//!                 PyExc_OverflowError,
-//!                 c_str!("arguments too large to add").as_ptr(),
-//!             );
-//!             std::ptr::null_mut()
-//!         }
-//!     }
+//! **`build.rs`**
+//! ```rust,ignore
+//! fn main() {
+//!     pyo3_build_config::use_pyo3_cfgs()
 //! }
 //! ```
 //!
@@ -201,6 +152,12 @@
 //! [manually][manual_builds]. Both offer more flexibility than `maturin` but require further
 //! configuration.
 //!
+//! This example stores the module definition statically and uses the `PyModule_Create` function
+//! in the CPython C API to register the module. This is the "old" style for registering modules
+//! and has the limitation that it cannot support subinterpreters. You can also create a module
+//! using the new multi-phase initialization API that does support subinterpreters. See the
+//! `sequential` project located in the `examples` directory at the root of the `pyo3-ffi` crate
+//! for a worked example of how to this using `pyo3-ffi`.
 //!
 //! # Using Python from Rust
 //!
@@ -226,7 +183,7 @@
 #![doc = concat!("[manual_builds]: https://pyo3.rs/v", env!("CARGO_PKG_VERSION"), "/building-and-distribution.html#manual-builds \"Manual builds - Building and Distribution - PyO3 user guide\"")]
 //! [setuptools-rust]: https://github.com/PyO3/setuptools-rust "Setuptools plugin for Rust extensions"
 //! [PEP 384]: https://www.python.org/dev/peps/pep-0384 "PEP 384 -- Defining a Stable ABI"
-#![doc = concat!("[Features chapter of the guide]: https://pyo3.rs/v", env!("CARGO_PKG_VERSION"), "/features.html#features-reference \"Features Reference - PyO3 user guide\"")]
+#![doc = concat!("[Features chapter of the guide]: https://pyo3.rs/v", env!("CARGO_PKG_VERSION"), "/features.html#features-reference \"Features eference - PyO3 user guide\"")]
 #![allow(
     missing_docs,
     non_camel_case_types,
diff --git a/include/pyo3/pyo3-ffi/src/listobject.rs b/include/pyo3/pyo3-ffi/src/listobject.rs
index 9d8b7ed6..881a8a87 100644
--- a/include/pyo3/pyo3-ffi/src/listobject.rs
+++ b/include/pyo3/pyo3-ffi/src/listobject.rs
@@ -50,6 +50,10 @@ extern "C" {
         arg3: Py_ssize_t,
         arg4: *mut PyObject,
     ) -> c_int;
+    #[cfg(Py_3_13)]
+    pub fn PyList_Extend(list: *mut PyObject, iterable: *mut PyObject) -> c_int;
+    #[cfg(Py_3_13)]
+    pub fn PyList_Clear(list: *mut PyObject) -> c_int;
     #[cfg_attr(PyPy, link_name = "PyPyList_Sort")]
     pub fn PyList_Sort(arg1: *mut PyObject) -> c_int;
     #[cfg_attr(PyPy, link_name = "PyPyList_Reverse")]
diff --git a/include/pyo3/pyo3-ffi/src/methodobject.rs b/include/pyo3/pyo3-ffi/src/methodobject.rs
index bd214409..37e1e206 100644
--- a/include/pyo3/pyo3-ffi/src/methodobject.rs
+++ b/include/pyo3/pyo3-ffi/src/methodobject.rs
@@ -50,7 +50,7 @@ pub type PyCFunctionFast = unsafe extern "C" fn(
 ) -> *mut PyObject;
 
 #[cfg(any(Py_3_10, not(Py_LIMITED_API)))]
-#[deprecated(note = "renamed to `PyCFunctionFast`")]
+#[cfg_attr(Py_3_10, deprecated(note = "renamed to `PyCFunctionFast`"))]
 pub type _PyCFunctionFast = PyCFunctionFast;
 
 pub type PyCFunctionWithKeywords = unsafe extern "C" fn(
@@ -68,6 +68,7 @@ pub type PyCFunctionFastWithKeywords = unsafe extern "C" fn(
 ) -> *mut PyObject;
 
 #[cfg(any(Py_3_10, not(Py_LIMITED_API)))]
+#[cfg_attr(Py_3_10, deprecated(note = "renamed to `PyCFunctionFastWithKeywords`"))]
 pub type _PyCFunctionFastWithKeywords = PyCFunctionFastWithKeywords;
 
 #[cfg(all(Py_3_9, not(Py_LIMITED_API)))]
@@ -152,7 +153,7 @@ pub union PyMethodDefPointer {
 
     /// This variant corresponds with [`METH_FASTCALL`].
     #[cfg(any(Py_3_10, not(Py_LIMITED_API)))]
-    #[deprecated(note = "renamed to `PyCFunctionFast`")]
+    #[cfg_attr(Py_3_10, deprecated(note = "renamed to `PyCFunctionFast`"))]
     pub _PyCFunctionFast: PyCFunctionFast,
 
     /// This variant corresponds with [`METH_FASTCALL`].
@@ -161,6 +162,7 @@ pub union PyMethodDefPointer {
 
     /// This variant corresponds with [`METH_FASTCALL`] | [`METH_KEYWORDS`].
     #[cfg(any(Py_3_10, not(Py_LIMITED_API)))]
+    #[cfg_attr(Py_3_10, deprecated(note = "renamed to `PyCFunctionFastWithKeywords`"))]
     pub _PyCFunctionFastWithKeywords: PyCFunctionFastWithKeywords,
 
     /// This variant corresponds with [`METH_FASTCALL`] | [`METH_KEYWORDS`].
diff --git a/include/pyo3/pyo3-ffi/src/moduleobject.rs b/include/pyo3/pyo3-ffi/src/moduleobject.rs
index ff6458f4..2417664a 100644
--- a/include/pyo3/pyo3-ffi/src/moduleobject.rs
+++ b/include/pyo3/pyo3-ffi/src/moduleobject.rs
@@ -88,6 +88,10 @@ pub const Py_mod_create: c_int = 1;
 pub const Py_mod_exec: c_int = 2;
 #[cfg(Py_3_12)]
 pub const Py_mod_multiple_interpreters: c_int = 3;
+#[cfg(Py_3_13)]
+pub const Py_mod_gil: c_int = 4;
+
+// skipped private _Py_mod_LAST_SLOT
 
 #[cfg(Py_3_12)]
 pub const Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED: *mut c_void = 0 as *mut c_void;
@@ -96,7 +100,15 @@ pub const Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED: *mut c_void = 1 as *mut c_void
 #[cfg(Py_3_12)]
 pub const Py_MOD_PER_INTERPRETER_GIL_SUPPORTED: *mut c_void = 2 as *mut c_void;
 
-// skipped non-limited _Py_mod_LAST_SLOT
+#[cfg(Py_3_13)]
+pub const Py_MOD_GIL_USED: *mut c_void = 0 as *mut c_void;
+#[cfg(Py_3_13)]
+pub const Py_MOD_GIL_NOT_USED: *mut c_void = 1 as *mut c_void;
+
+#[cfg(all(not(Py_LIMITED_API), Py_GIL_DISABLED))]
+extern "C" {
+    pub fn PyUnstable_Module_SetGIL(module: *mut PyObject, gil: *mut c_void) -> c_int;
+}
 
 #[repr(C)]
 pub struct PyModuleDef {
diff --git a/integration/requirements.txt b/integration/requirements.txt
index e5b290de..2f47d3a7 100644
--- a/integration/requirements.txt
+++ b/integration/requirements.txt
@@ -1,3 +1,3 @@
 flask;sys_platform!="win"
 gunicorn;sys_platform!="win"
-httpx==0.24.1;sys_platform!="win"
+httpx==0.27.2;sys_platform!="win"
diff --git a/requirements.txt b/requirements.txt
index 9981cc8c..d211c555 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,4 +3,4 @@
 -r test/requirements.txt
 maturin
 mypy==1.13.0
-ruff==0.7.1
+ruff==0.7.3
diff --git a/script/install-fedora b/script/install-fedora
index 19a5a455..6d14860e 100755
--- a/script/install-fedora
+++ b/script/install-fedora
@@ -14,7 +14,7 @@ export CARGO_TARGET_DIR="${CARGO_TARGET_DIR:-target}"
 
 rm /etc/yum.repos.d/fedora-cisco-openh264.repo || true
 
-dnf install --setopt=install_weak_deps=false -y rustup clang lld "${PYTHON_PACKAGE}"
+dnf install --setopt=install_weak_deps=false -y rustup clang lld "${PYTHON_PACKAGE}" python3-uv
 
 rustup-init --default-toolchain "${RUST_TOOLCHAIN}-${TARGET}" --profile minimal --component rust-src -y
 source "${HOME}/.cargo/env"
@@ -24,7 +24,6 @@ cp ci/config.toml .cargo/config.toml
 
 cargo fetch --target="${TARGET}" &
 
-curl -LsSf https://astral.sh/uv/install.sh | sh
 rm -rf "${VENV}"
 uv venv --python "${PYTHON}" "${VENV}"
 source "${VENV}/bin/activate"
diff --git a/script/lint b/script/lint
index 22f5742e..94a46b1c 100755
--- a/script/lint
+++ b/script/lint
@@ -2,7 +2,7 @@
 
 set -eou pipefail
 
-to_lint="./bench/*.py ./pysrc/orjson/__init__.pyi ./test/*.py script/pydataclass script/pymem
+to_lint="./bench/*.py ./pysrc/orjson/__init__.pyi ./test/*.py script/pydataclass
 script/pysort script/pynumpy script/pynonstr script/pycorrectness script/graph integration/init
 integration/wsgi.py integration/typestubs.py integration/thread"
 
diff --git a/script/pymem b/script/pymem
deleted file mode 100755
index 6b97bb0d..00000000
--- a/script/pymem
+++ /dev/null
@@ -1,34 +0,0 @@
-#!/usr/bin/env python3
-# SPDX-License-Identifier: (Apache-2.0 OR MIT)
-
-import io
-import subprocess
-
-from tabulate import tabulate
-
-buf = io.StringIO()
-
-headers = ("Library", "import, read() RSS (MiB)", "loads() increase in RSS (MiB)")
-
-LIBRARIES = ("orjson", "ujson", "rapidjson", "simplejson", "json")
-
-FIXTURES = ("canada.json", "citm_catalog.json", "github.json", "twitter.json")
-
-for fixture in sorted(FIXTURES, reverse=True):
-    table = []
-    buf.write("\n" + "#### " + fixture + "\n\n")
-    for lib_name in LIBRARIES:
-        proc = subprocess.Popen(
-            ("bench/run_mem", f"data/{fixture}.xz", lib_name), stdout=subprocess.PIPE
-        )
-        output = proc.stdout.readline().decode("utf-8").strip().split(",")
-        mem_base = int(output[0]) / 1024 / 1024
-        mem_diff = int(output[1]) / 1024 / 1024
-        correct = bool(int(output[2]))
-        if correct:
-            table.append((lib_name, f"{mem_base:,.1f}", f"{mem_diff:,.1f}"))
-        else:
-            table.append((lib_name, "", ""))
-    buf.write(tabulate(table, headers, tablefmt="github") + "\n")
-
-print(buf.getvalue())
diff --git a/src/lib.rs b/src/lib.rs
index 64ace9e1..e65cd7f5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,6 +4,7 @@
 #![cfg_attr(feature = "intrinsics", feature(core_intrinsics))]
 #![cfg_attr(feature = "optimize", feature(optimize_attribute))]
 #![cfg_attr(feature = "unstable-simd", feature(portable_simd))]
+#![allow(unknown_lints)]
 #![allow(internal_features)] // core_intrinsics
 #![allow(non_camel_case_types)]
 #![allow(static_mut_refs)]
diff --git a/src/util.rs b/src/util.rs
index 8add0f75..2958d287 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -267,7 +267,11 @@ macro_rules! reserve_pretty {
 macro_rules! assume {
     ($expr:expr) => {
         debug_assert!($expr);
-        #[cfg(feature = "intrinsics")]
+        #[cfg(feature = "assert_unchecked")]
+        unsafe {
+            core::hint::assert_unchecked($expr);
+        };
+        #[cfg(all(not(feature = "assert_unchecked"), feature = "intrinsics"))]
         unsafe {
             core::intrinsics::assume($expr);
         };
diff --git a/test/requirements.txt b/test/requirements.txt
index 2c04102f..f2791df7 100644
--- a/test/requirements.txt
+++ b/test/requirements.txt
@@ -7,4 +7,3 @@ psutil;(sys_platform=="linux" or sys_platform == "macos") and platform_machine==
 pytest
 pytz
 typing_extensions;python_version<"3.8"
-xxhash==1.4.3;sys_platform=="linux" and platform_machine=="x86_64" and python_version<"3.9" # creates non-compact ASCII for test_str_ascii
diff --git a/test/test_type.py b/test/test_type.py
index 81c89307..3a3f7a56 100644
--- a/test/test_type.py
+++ b/test/test_type.py
@@ -5,11 +5,6 @@
 
 import pytest
 
-try:
-    import xxhash
-except ImportError:
-    xxhash = None
-
 import orjson
 
 
@@ -260,17 +255,6 @@ def test_str_surrogates_dumps(self):
             orjson.JSONEncodeError, orjson.dumps, b"\xed\xa0\xbd\xed\xba\x80"
         )  # \ud83d\ude80
 
-    @pytest.mark.skipif(
-        xxhash is None, reason="xxhash install broken on win, python3.9, Azure"
-    )
-    def test_str_ascii(self):
-        """
-        str is ASCII but not compact
-        """
-        digest = xxhash.xxh32_hexdigest("12345")
-        for _ in range(2):
-            assert orjson.dumps(digest) == b'"b30d56b4"'
-
     def test_bytes_dumps(self):
         """
         bytes dumps not supported