diff --git a/pyproject.toml b/pyproject.toml
index aa379d4e..54d0f420 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -108,6 +108,11 @@ markers = [
     "e2e_recovery: opt-in end-to-end SSE recovery harness (real server + real SSE consumers, scripted provider — NOT live, no LLM backend needed); tens of seconds each. CI lanes run ``-m 'not live and not e2e_recovery'``; select with ``-m e2e_recovery``.",
 ]
 filterwarnings = [
+    # The MCP v1 FastMCP integration fixture rebuilds its incomplete generic
+    # Settings model before construction. Keep the new pydantic-settings 2.15
+    # diagnostic fatal so removing that compatibility step cannot regress
+    # into a warning hidden in the full-suite summary.
+    "error:Field 'lifespan' has an incomplete definition",
     # mcp v1 deprecates streamablehttp_client for an entry point whose call
     # shape only settles in v2 — adoption rides the deliberate v2 migration
     # (pin capped <2); silence exactly this message until then.
diff --git a/tests/conftest.py b/tests/conftest.py
index e6493602..53258715 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -15,6 +15,20 @@ from unittest.mock import MagicMock
 import pytest
 
 
+def pytest_sessionstart(session: pytest.Session) -> None:
+    """Resolve MCP v1's generic FastMCP settings model for test servers.
+
+    MCP 1.29.0 defines ``Settings`` before ``FastMCP``, so its ``lifespan``
+    annotation remains an unresolved forward reference after import. Rebuild
+    once, after the module is fully loaded, before any integration fixture
+    constructs a FastMCP server. Pydantic's public hook is a no-op once the SDK
+    ships a complete model.
+    """
+    from mcp.server.fastmcp.server import Settings as FastMCPSettings
+
+    FastMCPSettings.model_rebuild()
+
+
 def stop_loop_thread(loop: asyncio.AbstractEventLoop, thread: threading.Thread) -> None:
     """Fully tear down a ``loop.run_forever``-in-a-thread test loop.