Route Context.report_progress() to the originating request stream

Context.report_progress() called send_progress_notification() without
related_request_id, so on Streamable HTTP the progress notification was
routed to the standalone GET stream instead of the originating POST's SSE
response. If the client had not yet opened (or never opens) the GET stream,
the notification was silently dropped.

Context.log(), elicit(), and elicit_url() already pass
related_request_id=self.request_id; this brings report_progress() in line.

Author: maxisbey

src/mcp/server/fastmcp/server.py

@@ -1177,6 +1177,7 @@ async def report_progress(self, progress: float, total: float | None = None, mes
             progress=progress,
             total=total,
             message=message,
+            related_request_id=self.request_id,
         )
 
     async def read_resource(self, uri: str | AnyUrl) -> Iterable[ReadResourceContents]:

tests/issues/test_176_progress_token.py

@@ -36,6 +36,12 @@ async def test_progress_token_zero_first_call():
 
     # Verify progress notifications
     assert mock_session.send_progress_notification.call_count == 3, "All progress notifications should be sent"
-    mock_session.send_progress_notification.assert_any_call(progress_token=0, progress=0.0, total=10.0, message=None)
-    mock_session.send_progress_notification.assert_any_call(progress_token=0, progress=5.0, total=10.0, message=None)
-    mock_session.send_progress_notification.assert_any_call(progress_token=0, progress=10.0, total=10.0, message=None)
+    mock_session.send_progress_notification.assert_any_call(
+        progress_token=0, progress=0.0, total=10.0, message=None, related_request_id="test-request"
+    )
+    mock_session.send_progress_notification.assert_any_call(
+        progress_token=0, progress=5.0, total=10.0, message=None, related_request_id="test-request"
+    )
+    mock_session.send_progress_notification.assert_any_call(
+        progress_token=0, progress=10.0, total=10.0, message=None, related_request_id="test-request"
+    )