diff --git a/.github/workflows/_checks.yml b/.github/workflows/_checks.yml
index d1b5853..5726aa1 100644
--- a/.github/workflows/_checks.yml
+++ b/.github/workflows/_checks.yml
@@ -37,6 +37,8 @@ jobs:
           - "3.13"
           - "3.14"
           - "3.14t"
+          - "3.15"
+          - "3.15t"
     steps:
       - uses: actions/checkout@v6
       - uses: extractions/setup-just@v4
@@ -48,7 +50,7 @@ jobs:
       - run: uv python pin ${{ matrix.python-version }}
       - run: just install
       - name: Confirm the interpreter is free-threaded
-        if: matrix.python-version == '3.14t'
+        if: endsWith(matrix.python-version, 't')
         run: uv run --no-sync python -c "import sys; assert not sys._is_gil_enabled(), 'GIL is enabled'"
       - run: just test-ci
   floors:
diff --git a/AGENTS.md b/AGENTS.md
index 611586e..09e9e9c 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -65,7 +65,7 @@ Transport mocking is `httpx2.MockTransport` passed as `transport=`, never `respx
 targets `httpx` rather than `httpx2` and patches its internals. Concurrency-sensitive components carry
 Hypothesis property tests in `test_*_props.py`, and `stress`-marked tests drive real thread
 parallelism: they run under the GIL for coverage, but the proof comes from the free-threaded
-`3.14t` CI job.
+`3.14t` and `3.15t` CI jobs.
 
 ## Workflow
 
diff --git a/pyproject.toml b/pyproject.toml
index 48d641a..ac22ed7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,6 +25,7 @@ classifiers = [
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
+    "Programming Language :: Python :: 3.15",
     "Programming Language :: Python :: Free Threading :: 2 - Beta",
     "Typing :: Typed",
     "Topic :: Software Development :: Libraries",