Dash Repo Skill

Dash is Plotly's Python framework for building reactive web applications with Python layouts, React component bundles, and server-side or clientside callbacks. Use this repo skill when a task involves Dash application code, callback routing, Dash server backends, component wrapper generation, the Dash renderer, or Dash repo test/build workflows.

Read first

• Read references/package-overview.md for the installed package shape, public imports, optional extras, CLIs, and major subsystems.
• Read references/troubleshooting.md for cross-cutting install/import, generated component, optional dependency, Node, browser, and stale-skill failures.
• Read references/repo-provenance.md before deciding whether this skill matches a current Dash checkout.
• Run scripts/check_dash_install.py when you need a safe import/optional-backend/CLI diagnostic before using deeper routes.

Quick install and smoke check

For ordinary app use:

python -m pip install dash
python - <<'PY'
import dash
from dash import Dash, html, dcc, Input, Output
print(dash.__version__)
app = Dash(__name__)
app.layout = html.Div([dcc.Input(id="name"), html.Div(id="out")])
@app.callback(Output("out", "children"), Input("name", "value"))
def update(value):
    return value or ""
print(app.layout.to_plotly_json()["type"], len(app.callback_map))
PY

Choose extras only when the workflow needs them:

Need	Install
Selenium/browser testing fixtures	python -m pip install "dash[testing]"
Diskcache background callbacks	python -m pip install "dash[diskcache]"
Celery background callbacks	python -m pip install "dash[celery]" plus a broker/result backend
FastAPI backend and WebSocket callbacks	python -m pip install "dash[fastapi]"
Quart backend	python -m pip install "dash[quart]"
async def callbacks on Flask	python -m pip install "dash[async]"
Component generation helpers	install Dash from a checkout with the development dependencies needed by the component package

Route by task

Build or debug a Dash app

Use sub-skills/app-callback-workflows/SKILL.md when the task mentions:

• Dash(...), layout trees, html, dcc, dash_table, component IDs, assets, URL prefixes, Jupyter display, CSP hashes, or pages.
• @app.callback, @dash.callback, Input, Output, State, MATCH, ALL, ALLSMALLER, ctx, callback_context, PreventUpdate, no_update, or Patch.
• Clientside callbacks or window.dash_clientside.

Start with its callbacks and layouts reference, then use its smoke scripts for layout/callback/page checks.

Select backends, async, WebSocket, background callbacks, hooks, or MCP

Use sub-skills/server-backends-and-async/SKILL.md when the task mentions:

• Flask, FastAPI, Quart, ASGI, backend adapters, custom backends, or route handling.
• async def callbacks, dash[async], websocket_callbacks, websocket=True, persistent=True, ctx.websocket, set_props, or WebSocket disconnects.
• background=True, DiskcacheManager, CeleryManager, progress, running, cancel, or callback caching.
• Dash hooks, WebSocket connection hooks, MCP resources/tools, or configure_mcp_server.

Run its backend inspection script for a safe optional-extra report before promising backend coverage.

Work on custom components, built-in components, resources, or renderer

Use sub-skills/component-renderer-development/SKILL.md when the task mentions:

• dash-generate-components, dash-update-components, renderer, component metadata, generated Python wrappers, R/Julia wrapper generation, or built-in component packages.
• Component, to_plotly_json, _children_props, _js_dist, _css_dist, serve_locally, external_url, dev_package_path, or resource fingerprints.
• dash-renderer, callback queues, setProps, crawlLayout, paths, window.dash_component_api, SharedWorker/WebSocket client, React versions, or JSX runtime problems.

Use its CLI-check scripts before running heavier Node or component builds.

Choose tests, build/lint commands, or repo-maintenance workflow

Use sub-skills/testing-and-maintenance/SKILL.md when the task mentions:

• pytest, dash_duo, Selenium, ChromeDriver, Percy, renderer tests, component tests, npm run build, npm run lint, Black/flake8/pylint/eslint/prettier, or contribution policy.
• A patch to Dash source where you need a focused native test plan.

Follow its rule: never run all integration tests by default. Use focused files and preserve enough output to see tracebacks and assertion context.

Important boundaries

• Do not claim FastAPI, Quart, Diskcache, Celery, browser, renderer, or component build workflows are available until the relevant extra/tool/service is installed and checked.
• Do not use a CPU import check as proof of browser, Node, Celery broker, or WebSocket runtime behavior.
• For package-use tasks, prefer public APIs and bundled references/scripts in this skill. For repo-maintenance tasks, the testing sub-skill may tell you how to run focused commands in a current Dash checkout.
• If the current checkout commit, generated component wrapper state, or package version differs from references/repo-provenance.md, treat this skill as potentially stale and refresh it before relying on maintainer-specific details.