functions-local-dev

Functions local dev

Use this skill when you are asked to:

• Start the backend Functions host locally.
• Switch local persistence modes (memory vs cosmos).
• Debug common “func won’t start” / config issues.

Canonical local loop

Preferred options:

1. VS Code tasks (recommended):
   • npm watch (functions)
   • func: host start
2. Single command dev loop:
   • npm run dev in backend/

Helper scripts

• scripts/start-backend-dev.mjs — starts backend dev loop with a stable entrypoint.

Environment notes

• Backend expects local.settings.json in backend/.
• Use the existing npm helpers:
  • npm run use:memory (backend)
  • npm run use:cosmos (backend)

If Azure Functions Core Tools (func) isn’t installed, the host start step will fail; prefer VS Code task output for diagnosis.

Last reviewed: 2026-01-15