fix: use StreamableHTTPSessionManager in stateless mode

The previous per-request transport implementation couldn't maintain
session state. Using the SDK's built-in SessionManager with stateless=True
means sessions start pre-initialized — tool calls work immediately
without the init handshake, avoiding the reconnection race condition.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/claude_memory/api/app.py

@@ -15,7 +15,7 @@ from fastapi.responses import Response
 from fastapi.staticfiles import StaticFiles
 from mcp.server.fastmcp import FastMCP
 from mcp.server.sse import SseServerTransport
-from mcp.server.streamable_http import StreamableHTTPServerTransport
+from mcp.server.streamable_http_manager import StreamableHTTPSessionManager
 from starlette.routing import Mount, Route
 from starlette.types import ASGIApp, Receive, Scope, Send
 
@@ -42,7 +42,8 @@ _current_user: ContextVar[str] = ContextVar("_current_user", default="default")
 @asynccontextmanager
 async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
     await init_pool()
-    yield
+    async with streamable_session_mgr.run():
+        yield
     await close_pool()
 
 
@@ -1297,12 +1298,17 @@ class HandleSSE:
             )
 
 
-# Streamable HTTP transport — stateless, no persistent SSE connection needed.
-# Each request carries its own init+tool call. More reliable through proxies.
+# Streamable HTTP transport — session manager handles lifecycle automatically.
+# More reliable through proxies than SSE since responses come in HTTP body.
+streamable_session_mgr = StreamableHTTPSessionManager(
+    app=mcp_server._mcp_server,
+    json_response=True,
+    stateless=True,
+)
+
+
 class HandleStreamableHTTP:
-    """ASGI app for streamable-http MCP connections."""
-    def __init__(self) -> None:
-        self._transport: StreamableHTTPServerTransport | None = None
+    """ASGI wrapper that sets _current_user before delegating to the session manager."""
 
     async def __call__(self, scope: Any, receive: Any, send: Any) -> None:
         user_id = "default"
@@ -1314,29 +1320,7 @@ class HandleStreamableHTTP:
                     user_id = resolved
                 break
         _current_user.set(user_id)
-
-        session_id = None
-        for name, value in scope.get("headers", []):
-            if name == b"mcp-session-id":
-                session_id = value.decode()
-                break
-
-        transport = StreamableHTTPServerTransport(
-            mcp_session_id=session_id,
-            is_json_response_enabled=True,
-        )
-        async with transport.connect() as (read_stream, write_stream):
-            import anyio
-            async with anyio.create_task_group() as tg:
-                async def run_server() -> None:
-                    await mcp_server._mcp_server.run(
-                        read_stream, write_stream,
-                        mcp_server._mcp_server.create_initialization_options(),
-                    )
-
-                tg.start_soon(run_server)
-                await transport.handle_request(scope, receive, send)
-                tg.cancel_scope.cancel()
+        await streamable_session_mgr.handle_request(scope, receive, send)
 
 
 streamable_handler = HandleStreamableHTTP()