Embed Excalidraw MCP App via interactive iframe and emit excalidraw_view SSE

[Amer-alsayed]

Motivation

• The previous static/mock Excalidraw scene did not follow the Excalidraw MCP README and prevented interactive in-chat editing and fullscreen/open UX.
• We need the server to emit an MCP app payload so clients that support MCP Apps can render a live Excalidraw canvas.
• The UI should persist the app card in history and provide safe open/fullscreen controls for environments that allow iframes.

Description

• Server: added isExcalidrawIntent, extractUserText, and buildExcalidrawEventPayload in api/chat.js and emit an excalidraw_view SSE event that contains an app payload with iframeUrl, openUrl, fallbackUrl, remoteServer, and prompt for Excalidraw MCP.
• Client: updated assets/js/app.js to render an interactive Excalidraw MCP iframe card (with safeExternalUrl checks), Open and Fullscreen controls, handle incoming excalidraw_view SSE events during streaming, and persist excalidrawView in conversation history.
• Styles: added card and fullscreen CSS in assets/css/style.css to style the embedded app container and fullscreen behavior.
• Tests: added test/excalidraw-mcp-event.test.js to validate intent detection and the new MCP app iframe payload contract.

Testing

• Ran the test suite with node --test and all tests passed.
• Performed a local smoke run with node server.js to verify the app serves and the SSE path triggers UI rendering successfully.
• Executed a Playwright rendering script that produced a screenshot artifact showing the iframe-based Excalidraw MCP card (artifact saved during the run and used to validate UI rendering).

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Codex Task

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Project	Deployment	Actions	Updated (UTC)
chaqgpt	Ready	Preview, Comment	Feb 19, 2026 0:57am

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