[v1.x] Scope experimental tasks to the session that created them (#2720)

tests/experimental/tasks/test_request_context.py

@@ -3,6 +3,7 @@
 import pytest
 
 from mcp.server.experimental.request_context import Experimental
+from mcp.server.experimental.task_context import ServerTaskContext
 from mcp.shared.exceptions import McpError
 from mcp.types import (
     METHOD_NOT_FOUND,
@@ -11,6 +12,7 @@ from mcp.types import (
     TASK_REQUIRED,
     ClientCapabilities,
     ClientTasksCapability,
+    Result,
     TaskMetadata,
     Tool,
     ToolExecution,
@@ -164,3 +166,30 @@ def test_can_use_tool_forbidden_without_task_support() -> None:
 def test_can_use_tool_none_without_task_support() -> None:
     exp = Experimental(_client_capabilities=ClientCapabilities())
     assert exp.can_use_tool(None) is True
+
+
+@pytest.mark.anyio
+async def test_run_task_with_an_explicit_task_id_emits_a_deprecation_warning() -> None:
+    """An explicitly provided task ID is not associated with the creating session, so passing one is deprecated."""
+    exp = Experimental(task_metadata=TaskMetadata(ttl=60000))
+
+    async def work(task: ServerTaskContext) -> Result:
+        raise AssertionError("unreachable")  # pragma: no cover
+
+    with pytest.warns(DeprecationWarning, match="not associated with the session"):
+        # Task support is not configured, so the call fails after the
+        # deprecated argument has been reported.
+        with pytest.raises(RuntimeError, match="Task support not enabled"):
+            # The deliberate use of the deprecated overload is the point of this test.
+            await exp.run_task(work, task_id="explicitly-chosen")  # pyright: ignore[reportDeprecated]
+
+
+@pytest.mark.anyio
+async def test_run_task_without_a_task_id_does_not_warn() -> None:
+    exp = Experimental(task_metadata=TaskMetadata(ttl=60000))
+
+    async def work(task: ServerTaskContext) -> Result:
+        raise AssertionError("unreachable")  # pragma: no cover
+
+    with pytest.raises(RuntimeError, match="Task support not enabled"):
+        await exp.run_task(work)