Support Python 3.14

Add the 3.14 trove classifier, add 3.14 to the CI test matrix, and make
the dependency floors installable there:

- pydantic >=2.12.0 and starlette >=0.48.0 on 3.14 only (older floors
  pin pydantic-core 2.33.0 / predate 3.14 support and have no cp314
  wheels); floors for <3.14 are unchanged
- pywin32 >=311 on 3.14 only (310 ships no cp314 wheels)
- mkdocs-material[imaging] >=9.6.19: the 9.5.45 imaging extra pins
  pillow~=10.2, which has no cp314 wheels and fails to install on the
  3.14 lowest-direct lane; 9.6.19 allows pillow 11.x
- backport the coverage workarounds from #1834 (coveragepy#1987 branch
  misreporting on 3.14), plus one no-branch pragma for a nested
  async-with arc in test_sse_security.py
- regenerate uv.lock with the 3.14 resolution fork

The README badge lists supported versions from the classifiers of the
latest PyPI release, so the badge updates at the next v1.x release.

Update CONTRIBUTING.md to say 3.10 through 3.14.

Author: maxisbey

.github/workflows/shared.yml

@@ -35,7 +35,7 @@ jobs:
     continue-on-error: true
     strategy:
       matrix:
-        python-version: ["3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
         dep-resolution:
           - name: lowest-direct
             install-flags: "--upgrade --resolution lowest-direct"

CONTRIBUTING.md

@@ -72,7 +72,7 @@ When bumping a dependency version manually, update the constraint in `pyproject.
 
 Security-relevant dependency updates (P0) are applied within 7 days of public disclosure and backported to active release branches.
 
-The SDK currently supports Python 3.10 through 3.13. New CPython releases are supported within one minor SDK release of their stable release date.
+The SDK currently supports Python 3.10 through 3.14. New CPython releases are supported within one minor SDK release of their stable release date.
 
 ## Triage Process
 

pyproject.toml

@@ -20,19 +20,23 @@ classifiers = [
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
 ]
 dependencies = [
     "anyio>=4.5",
     "httpx>=0.27.1,<1.0.0",
     "httpx-sse>=0.4",
-    "pydantic>=2.11.0,<3.0.0",
-    "starlette>=0.27",
+    "pydantic>=2.12.0,<3.0.0; python_version >= '3.14'",
+    "pydantic>=2.11.0,<3.0.0; python_version < '3.14'",
+    "starlette>=0.48.0; python_version >= '3.14'",
+    "starlette>=0.27; python_version < '3.14'",
     "python-multipart>=0.0.9",
     "sse-starlette>=1.6.1",
     "pydantic-settings>=2.5.2",
     "uvicorn>=0.31.1; sys_platform != 'emscripten'",
     "jsonschema>=4.20.0",
-    "pywin32>=310; sys_platform == 'win32'",
+    "pywin32>=311; sys_platform == 'win32' and python_version >= '3.14'",
+    "pywin32>=310; sys_platform == 'win32' and python_version < '3.14'",
     "pyjwt[crypto]>=2.10.1",
     "typing-extensions>=4.9.0",
     "typing-inspection>=0.4.1",
@@ -67,7 +71,7 @@ dev = [
 docs = [
     "mkdocs>=1.6.1",
     "mkdocs-glightbox>=0.4.0",
-    "mkdocs-material[imaging]>=9.5.45",
+    "mkdocs-material[imaging]>=9.6.19",
     "mkdocstrings-python>=1.12.2",
 ]
 

src/mcp/server/fastmcp/utilities/context_injection.py

@@ -25,7 +25,8 @@ def find_context_parameter(fn: Callable[..., Any]) -> str | None:
     # Get type hints to properly resolve string annotations
     try:
         hints = typing.get_type_hints(fn)
-    except Exception:
+    # TODO(Marcelo): Drop the pragma once https://github.com/coveragepy/coveragepy/issues/1987 is fixed.
+    except Exception:  # pragma: no cover
         # If we can't resolve type hints, we can't find the context parameter
         return None
 

src/mcp/server/session.py

@@ -685,7 +685,5 @@ async def _handle_incoming(self, req: ServerRequestResponder) -> None:
         await self._incoming_message_stream_writer.send(req)
 
     @property
-    def incoming_messages(
-        self,
-    ) -> MemoryObjectReceiveStream[ServerRequestResponder]:
+    def incoming_messages(self) -> MemoryObjectReceiveStream[ServerRequestResponder]:
         return self._incoming_message_stream_reader

tests/experimental/tasks/server/test_server.py

@@ -312,7 +312,8 @@ async def run_server():
             async with anyio.create_task_group() as tg:
 
                 async def handle_messages():
-                    async for message in server_session.incoming_messages:
+                    # TODO(Marcelo): Drop the pragma once https://github.com/coveragepy/coveragepy/issues/1987 is fixed.
+                    async for message in server_session.incoming_messages:  # pragma: no cover
                         await server._handle_message(message, server_session, {}, False)
 
                 tg.start_soon(handle_messages)
@@ -391,8 +392,8 @@ async def run_server():
             ),
         ) as server_session:
             async with anyio.create_task_group() as tg:
-
-                async def handle_messages():
+                # TODO(Marcelo): Drop the pragma once https://github.com/coveragepy/coveragepy/issues/1987 is fixed.
+                async def handle_messages():  # pragma: no cover
                     async for message in server_session.incoming_messages:
                         await server._handle_message(message, server_session, {}, False)
 

tests/server/test_lowlevel_input_validation.py

@@ -70,7 +70,8 @@ async def run_server():
             async with anyio.create_task_group() as tg:
 
                 async def handle_messages():
-                    async for message in server_session.incoming_messages:
+                    # TODO(Marcelo): Drop the pragma once https://github.com/coveragepy/coveragepy/issues/1987 is fixed.
+                    async for message in server_session.incoming_messages:  # pragma: no cover
                         await server._handle_message(message, server_session, {}, False)
 
                 tg.start_soon(handle_messages)

tests/server/test_lowlevel_output_validation.py

@@ -71,7 +71,8 @@ async def run_server():
             async with anyio.create_task_group() as tg:
 
                 async def handle_messages():
-                    async for message in server_session.incoming_messages:
+                    # TODO(Marcelo): Drop the pragma once https://github.com/coveragepy/coveragepy/issues/1987 is fixed.
+                    async for message in server_session.incoming_messages:  # pragma: no cover
                         await server._handle_message(message, server_session, {}, False)
 
                 tg.start_soon(handle_messages)

tests/server/test_lowlevel_tool_annotations.py

@@ -67,7 +67,8 @@ async def run_server():
             async with anyio.create_task_group() as tg:
 
                 async def handle_messages():
-                    async for message in server_session.incoming_messages:
+                    # TODO(Marcelo): Drop the pragma once https://github.com/coveragepy/coveragepy/issues/1987 is fixed.
+                    async for message in server_session.incoming_messages:  # pragma: no cover
                         await server._handle_message(message, server_session, {}, False)
 
                 tg.start_soon(handle_messages)

tests/server/test_session.py

@@ -410,11 +410,9 @@ async def test_create_message_tool_result_validation():
 
             # Case 8: empty messages list - skips validation entirely
             # Covers the `if messages:` branch (line 280->302)
-            with anyio.move_on_after(0.01):
-                await session.create_message(
-                    messages=[],
-                    max_tokens=100,
-                )
+            # TODO(Marcelo): Drop the pragma once https://github.com/coveragepy/coveragepy/issues/1987 is fixed.
+            with anyio.move_on_after(0.01):  # pragma: no cover
+                await session.create_message(messages=[], max_tokens=100)
 
 
 @pytest.mark.anyio