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name: server-backends-and-async description: "Use for Dash backend selection, async callbacks, WebSocket callbacks, background callbacks, hooks, and MCP server configuration." disable-model-invocation: true metadata: disco-role: operating license: MIT

Dash Server Backends and Async Workflows

Use this sub-skill when a task depends on Dash's server runtime rather than the layout/callback API alone: backend selection, async callbacks, background callbacks, WebSocket callbacks, hooks, or MCP exposure.

Start here

1. Read references/backend-workflows.md for backend selection, adapters, and constructor/runtime facts.
2. Read references/background-and-websocket-callbacks.md for async, background, and WebSocket behavior.
3. Read references/mcp-and-hooks.md for hooks and MCP configuration.
4. Read references/troubleshooting.md when a backend import or optional-extra path fails.
5. Run scripts/inspect_backends.py for a safe optional-backend diagnostic before promising backend coverage.

Main routes

Choose or inspect a backend

Dash defaults to Flask but can also run on FastAPI or Quart. Use this sub-skill when you need to know which backend constructor to use, which extras are needed, or how to create a Dash app around an existing server instance.

Write async or background callbacks

Use this sub-skill for async def callbacks, background=True, DiskcacheManager, CeleryManager, progress, running, cancel, and cache keys.

Use WebSocket callbacks

Route WebSocket tasks here when the callback depends on websocket_callbacks, websocket=True, persistent=True, ctx.websocket, set_props, or browser/ server disconnect behavior. FastAPI is the backend surface that exposes the WebSocket path in Dash.

Expose hooks or MCP content

Use this sub-skill for hooks.setup, hooks.layout, hooks.route, hooks.error, hooks.callback, hooks.websocket_connect, hooks.websocket_message, configure_mcp_server, and mcp_enabled.

Route elsewhere

• Plain callback, layout, page, asset, and clientside app behavior: app callback workflows.
• Component wrapper generation, dash-renderer, and resource loading: component renderer development.
• Test selection and browser command strategy: testing and maintenance.

Validation checklist

Before marking a backend workflow solved:

• The installed extra or backend package is present.
• If the workflow requires Flask async, dash[async] is installed.
• If the workflow requires FastAPI or Quart, the relevant extra is installed and a safe app/backend construction check passes.
• If the workflow requires Diskcache or Celery, the corresponding dependency set is installed and the service requirement is called out when applicable.
• If the workflow uses WebSocket callbacks, the backend and browser/runtime prerequisites are explicitly named.
• If a hook or MCP change alters route exposure, the sub-skill references explain the request/session/content-type rules and the expected failure modes.