ci: test Python 3.15 and 3.15t as supported versions

.github/workflows/_checks.yml

@@ -55,6 +55,8 @@ jobs:
           - "3.13"
           - "3.14"
           - "3.14t"
+          - "3.15"
+          - "3.15t"
     services:
       postgres:
         image: postgres:17
@@ -80,7 +82,7 @@ jobs:
       - run: uv python pin ${{ matrix.python-version }}
       - run: just install
       - name: Assert the GIL is actually disabled
-        if: matrix.python-version == '3.14t'
+        if: endsWith(matrix.python-version, 't')
         run: uv run --no-sync python -c "import sys, asyncpg, sqlalchemy, pydantic_core, faststream, faststream_outbox; assert not sys._is_gil_enabled(), 'GIL re-enabled - a dependency lacks free-threaded support'"
       - run: just test-ci
         env:

docs/introduction/installation.md

@@ -32,7 +32,7 @@
 ## Free-threaded Python
 
 `faststream-outbox` supports free-threaded (no-GIL) CPython. CI runs the full
-test suite on the 3.14t interpreter, and a separate CI step asserts that
+test suite on the 3.14t and 3.15t interpreters, and a separate CI step asserts that
 importing the outbox and its runtime dependencies keeps the GIL disabled. The
 package is pure-Python
 asyncio, so nothing in it depends on the GIL; installing on a `python3.14t`
@@ -58,7 +58,7 @@ process. To use more cores, run more subscriber processes, the same scaling
 lever as on a GIL build.
 
 Free-threaded wheels for the compiled dependencies currently exist for 3.14t
-only (there are no `cp313t` wheels), so 3.13t is not a supported target.
+and 3.15t only (there are no `cp313t` wheels), so 3.13t is not a supported target.
 
 ## Postgres
 

pyproject.toml

@@ -16,6 +16,7 @@ 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",