From 3d0352384b9a3b8fe87dd27d30e015c34f39e2be Mon Sep 17 00:00:00 2001
From: b3nw <b3nw@duck.com>
Date: Sat, 25 Apr 2026 05:20:20 +0000
Subject: [PATCH] fix: monkey-patch mcp cancellation race crash (SDK issue
 #2416)

Patch RequestResponder.respond() and cancel() at startup to handle
the race where a notifications/cancelled arrives between handler
return and respond(), which crashes the session with
"AssertionError: Request already responded to".

Also improve build.sh to handle registry push failures gracefully
and auto-restart the container after building.
---
 scripts/build.sh | 12 ++++++++++--
 server.py        | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/scripts/build.sh b/scripts/build.sh
index df614ad..7b3872d 100755
--- a/scripts/build.sh
+++ b/scripts/build.sh
@@ -6,6 +6,7 @@ PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
 SCRAPER_DIR="/home/b3nw/projects/financial/schwab-scraper"
 IMAGE="gitea.ext.ben.io/b3nw/schwab-mcp-custom:latest"
 BUILD_HOST="${BUILD_HOST:-docker-test}"
+COMPOSE_DIR="/opt/schwab-mcp-custom"
 
 cd "$PROJECT_DIR"
 
@@ -28,10 +29,17 @@ echo "==> Building Docker image on $BUILD_HOST..."
 ssh "$BUILD_HOST" "cd /tmp/schwab-mcp-build && docker build -t $IMAGE ."
 
 echo "==> Pushing image to registry..."
-ssh "$BUILD_HOST" "docker push $IMAGE"
+if ssh "$BUILD_HOST" "docker push $IMAGE" 2>/dev/null; then
+    echo "    Image pushed to registry."
+else
+    echo "    Registry push failed (auth?), image available locally only."
+fi
+
+echo "==> Restarting container..."
+ssh "$BUILD_HOST" "cd $COMPOSE_DIR && docker compose up -d --force-recreate --pull never --no-deps schwab-mcp"
 
 echo "==> Cleaning up..."
 rm -rf vendor/schwab-scraper
 ssh "$BUILD_HOST" "rm -rf /tmp/schwab-mcp-build"
 
-echo "==> Done! Image pushed: $IMAGE"
+echo "==> Done! Container restarted with new image."
diff --git a/server.py b/server.py
index b595b3d..f6f0797 100644
--- a/server.py
+++ b/server.py
@@ -1,4 +1,5 @@
 import json
+import logging
 import os
 from typing import Optional, Any
 
@@ -11,6 +12,40 @@ import uvicorn
 # Import the unified API from the schwab_scraper dependency
 import schwab_scraper.unified_api as api
 
+# ---------------------------------------------------------------------------
+# Monkey-patch mcp.shared.session.RequestResponder to work around a
+# cancellation race in mcp==1.27.0 (github.com/modelcontextprotocol/
+# python-sdk/issues/2416).  A concurrent notifications/cancelled can set
+# _completed=True between handler return and respond(), crashing the session
+# with "AssertionError: Request already responded to".
+# Remove once upstream ships a fix (likely mcp>=1.28).
+# ---------------------------------------------------------------------------
+def _patch_request_responder():
+    from mcp.shared.session import RequestResponder
+
+    _orig_respond = RequestResponder.respond
+
+    async def _safe_respond(self, response):
+        if self._completed:
+            logging.debug(
+                "respond() skipped for request %s — already completed (race with cancel)",
+                self.request_id,
+            )
+            return
+        return await _orig_respond(self, response)
+
+    _orig_cancel = RequestResponder.cancel
+
+    async def _safe_cancel(self):
+        if self._completed:
+            return
+        return await _orig_cancel(self)
+
+    RequestResponder.respond = _safe_respond
+    RequestResponder.cancel = _safe_cancel
+
+_patch_request_responder()
+
 # Initialize FastMCP
 mcp = FastMCP("SchwabScraper")