QA: MCP Apps — LangGraph (Python)

Prerequisites

Demo is deployed and accessible at /demos/mcp-apps on the dashboard host
Agent backend is healthy; OPENAI_API_KEY is set on Railway; LANGGRAPH_DEPLOYMENT_URL points at a LangGraph deployment exposing the mcp_apps graph (registered as agent name mcp-apps — see src/app/api/copilotkit-mcp-apps/route.ts)
MCP server target: the public Excalidraw MCP app at https://mcp.excalidraw.com (override via MCP_SERVER_URL). Pinned serverId: "excalidraw" so URL changes don't silently break persisted activities
Note: the demo source contains no data-testid attributes and registers no custom activity renderer — CopilotKit's built-in MCPAppsActivityRenderer handles the sandboxed iframe automatically. Checks below rely on verbatim visible text, network traffic, and the iframe DOM

Navigate to /demos/mcp-apps; verify the page renders within 3s and a single CopilotChat pane is centered (max-width ~896px, rounded-2xl, full-height)
Verify the chat is wired to runtimeUrl="/api/copilotkit-mcp-apps" and agent="mcp-apps" (DevTools → Network: sending a message hits that endpoint)
Verify both suggestion pills are visible with verbatim titles:
- "Draw a flowchart"
- "Sketch a system diagram"
Send "Hello" and verify an assistant text response appears within 10s (no MCP activity iframe for plain text)

Send the first flow-chart prompt; in DevTools → Network, verify the POST to /api/copilotkit-mcp-apps succeeds (status 200) and the server-side runtime resolves tools from https://mcp.excalidraw.com (watch the server logs for the MCP Apps middleware attaching the Excalidraw tool set — notably create_view)
Verify no console errors mentioning the MCP server URL, auth, or tool-schema parse failures

Click "Draw a flowchart"; within 60s verify the agent calls the create_view MCP tool exactly ONCE (per SYSTEM_PROMPT in src/agents/mcp_apps_agent.py: "Call create_view ONCE with 3-5 elements total") — confirm via DevTools → Network stream or backend logs
Verify the tool payload contains 3-5 Excalidraw elements (shapes + arrows + optional title text), each with a unique string id, and ends with ONE cameraUpdate sized 600x450 or 800x600

Within 60s of the tool call, verify a sandboxed <iframe> renders inline in the chat transcript (activity-message slot) pointed at the Excalidraw MCP UI resource
Verify the iframe has a sandbox attribute (CopilotKit's built-in renderer always sandboxes MCP UI resources)
Verify the iframe paints a flow-chart-shaped diagram: at least 3 shape nodes (rectangles, ellipses, or diamonds with text labels) connected by arrows, framed within the viewport (camera-update step from the system prompt)
Verify the assistant text below the iframe is a single short sentence describing what was drawn (per system prompt)

Without reloading, send the second suggestion "Sketch a system diagram"; within 60s verify a new activity iframe renders in-transcript containing a client → server → database layout (3 labeled shapes + 2 arrows)
Verify the previous flow-chart iframe is still present and un-stale in the scrollback (activity messages persist, matching the rationale for the pinned serverId: "excalidraw" in the runtime config)

Send an explicit prompt: "Use Excalidraw to draw exactly 2 rectangles labelled 'A' and 'B' connected by one arrow from A to B."
Within 60s verify: (1) create_view is called ONCE with exactly 3 elements (2 rectangles + 1 arrow) plus the trailing cameraUpdate; (2) an iframe renders showing two labelled rectangles with a connecting arrow; (3) the assistant reply is one short sentence; (4) no duplicate create_view invocations or retries appear in network / logs

Send an empty message; verify it is a no-op (no user bubble, no assistant response)
Send "What is 2+2?"; verify the agent replies in plain text without invoking create_view (no iframe, no MCP activity in the stream)
DevTools → Console: walk through all flows above; verify no uncaught errors, no CORS failures referencing mcp.excalidraw.com, and no "sandbox" / iframe-permission warnings

Chat loads within 3s; plain-text response within 10s; MCP-backed iframe renders within 60s of prompt (bias is "correct-enough diagram fast" per system prompt, one create_view call)
MCP server connection to https://mcp.excalidraw.com succeeds and the Excalidraw tool set (including create_view) is advertised to the agent at request time
At least one concrete end-to-end MCP interaction completes: user prompt → create_view tool call → activity event → sandboxed iframe painting the requested diagram
The built-in MCPAppsActivityRenderer is used (no app-side useRenderActivityMessage / renderActivityMessages registration exists in page.tsx — per the @region[no-frontend-renderer-needed] contract)
No UI layout breaks, no uncaught console errors, no duplicate create_view invocations within a single prompt turn