Test against Python 3.14

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

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

@@ -25,14 +25,17 @@ 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 +70,7 @@ 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