cowart-open-canvas

Cowart Open Canvas

The actual canvas-opening capability is the cowart_mcp MCP server and its render_cowart_canvas_widget tool. Use this skill when the user asks to open, reopen, or explicitly refresh the canvas. A bare @Cowart invocation with no other actionable request may also open the canvas. Do not use this skill as a prerequisite for image generation, annotation editing, HTML, Slides, or follow-up requests sent from an already-open Cowart widget.

Workflow

1. Ensure the cowart_mcp MCP server is loaded or discoverable and that its render_cowart_canvas_widget tool is available. The host may expose the complete tool name as mcp__cowart_mcp__render_cowart_canvas_widget. Call the tool once for the user's open, reopen, or explicit refresh request. Pass the user's active Codex workspace as projectDir; do not pass the Cowart plugin repository directory.

{
  "projectDir": "/absolute/path/to/user/codex-project"
}

The tool returns openai/outputTemplate: ui://widget/cowart/canvas.html, which tells Codex to render the widget directly. Do not start scripts/start-canvas.sh or open a localhost URL for normal use.

Cowart also declares an OpenAI MCP Extensions global entrypoint, so supported hosts can show it in navigation and let the user pin it. Clicking that entrypoint sends {} and opens the canvas directly at <system Documents>/Cowart/canvas/. This is one shared local canvas with multiple pages; the first page is created only when none exists. There is no project picker. Empty arguments never infer a workspace from the MCP process directory. When a workspace is known in chat, keep passing projectDir to open its canvas directly. Cowart declares only the fullscreen display mode; in a conversation, the host may place fullscreen apps in the content side panel.

For follow-ups from the global app, use the projectDir and canvasDir supplied in Cowart's model context or follow-up message. Do not substitute the global app thread's own working directory for the open canvas.

2. Confirm the widget opens for the user. The canvas data is stored in the active project:

canvas/pages/<page-id>/cowart-canvas.json
canvas/pages/<page-id>/assets/

3. If the MCP tool is not visible in the current turn, use tool discovery for Cowart widget/render capabilities and retry within the same task after an explicit Cowart canvas invocation. Do not claim that a new task is required merely because one turn did not expose the tool. Only suggest a new Codex task when the plugin was just installed or upgraded and the MCP schema is still unavailable after discovery and an explicit retry.

Constraints

Do not call render_cowart_canvas_widget again merely because another Cowart skill applies or an existing widget sends a follow-up request. The existing widget synchronizes MCP-backed canvas changes itself. Do not launch the old local web service, inspect canvas files, run builds, check storage layout, take screenshots, or perform other validation steps unless opening the widget fails or the user explicitly asks for those checks. The scripts/start-canvas.sh path is now only a local-development fallback.