--- title: "rayfin dev" description: "Start a local frontend and optional Functions runtime against a deployed Fabric Rayfin backend with rayfin dev." url: https://rayfin.ai/docs/reference/cli/dev markdown_url: https://rayfin.ai/docs/reference/cli/dev.md section: reference product: Rayfin sdk_version: 1.36.2 cli_version: 1.36.2 last_updated: 2026-10-03T17:23:06-07:00 source: reference/cli/dev.mdx --- # rayfin dev > Start a local frontend and optional Functions runtime against a deployed Fabric Rayfin backend with rayfin dev. Use `rayfin dev` for the local development loop. It provisions or reuses a Fabric AppBackend, applies service settings and Data schema, writes browser-visible environment values, then starts local project code. ```bash npx rayfin dev ``` The Fabric backend remains deployed in Microsoft Fabric. The CLI runs only your frontend, and Functions when enabled, on `localhost`. It never publishes static content. ## What the session does [#what-the-session-does] 1. Finds the Rayfin project from `[project-path]` (default `.`). 2. Authenticates with Fabric, using `-t, --tenant` when provided. 3. Resolves or creates the target Fabric backend. `--workspace`, `--workspace-id`, `RAYFIN_WORKSPACE_ID`, and recorded deployments can all select the workspace. 4. Applies runtime settings from `rayfin.yml`, including connectors. 5. Applies the Data configuration unless `--skip-db-apply` is passed. 6. Reserves the frontend dev port and appends `http://localhost:` and `http://127.0.0.1:` to auth redirect URIs when Auth is enabled. 7. Writes `RAYFIN_PUBLIC_*` values to `rayfin/.env` and regenerates the framework `.env.local` unless `--no-emit-env` is passed. 8. Starts `npm run dev:frontend` when present, otherwise `npm run dev` if it is not recursive. 9. When `services.functions.enabled: true`, builds Functions, writes `rayfin/functions/local.settings.json`, starts type generation and the local Functions host, then starts the frontend with `RAYFIN_PUBLIC_FUNCTIONS_URL` pointing at that host. Press Ctrl+C to stop local runtimes. The Fabric backend is long-lived and is not deleted. ## Options [#options] | Option | Default | Description | | ------------------------------- | ---------------- | ---------------------------------------------------------------------------------------------------------------------------------- | | `[project-path]` | `.` | Path to the project root directory. | | `--skip-db-apply` | `false` | Skip automatic database configuration apply. | | `--env-file ` | `rayfin/.env` | Path to `.env` for `rayfin.yml` interpolation. | | `--provider ` | `fabric` | Backend provider for managed Rayfin services. Use `fabric`. | | `-w, --workspace ` | — | Fabric workspace display name to provision a first-run backend into. | | `--workspace-id ` | — | Fabric workspace GUID to provision a first-run backend into. | | `--capacity-id ` | — | Fabric capacity ID to assign when the target workspace has no usable capacity. [New in 1.36](/docs/reference/changelog#rayfin-136) | | `-t, --tenant ` | signed-in tenant | Entra ID tenant GUID. | | `--encryption-fallback-enabled` | `false` | Allow plaintext token storage when the OS keychain is unavailable. | | `--no-emit-env` | `false` | Leave existing framework `.env.local` untouched. | | `-v, --verbose` | `false` | Enable verbose logging. | ## Files written [#files-written] | File | Written when | | ------------------------------------------------- | ------------------------------------------------------------------------------------------------- | | `rayfin/.deployments.json` | A backend is provisioned or selected. | | `rayfin/.env` | Public backend values, frontend port, retained port aliases, and local Functions URL are updated. | | `.env.local` or `/.env.local` | Framework environment is regenerated unless `--no-emit-env`. | | `rayfin/functions/local.settings.json` | Functions are enabled and run locally. | | `.vscode/launch.json` | Best-effort Functions attach config when Functions debugging is enabled. | ## Ports [#ports] | Port | Behavior | | -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Frontend | Starts from `RAYFIN_PUBLIC_FRONTEND_PORT` or 5173. If occupied, the CLI slides to the next available port and keeps the old occupied value in `RAYFIN_FRONTEND_DEV_PORT_ALIASES` so existing auth redirects keep working. | | Functions | Starts at 7071 and slides forward when occupied. The chosen URL is written to `RAYFIN_PUBLIC_FUNCTIONS_URL`. | | Node inspector | Starts at 9229 and slides forward when Functions debugging is enabled. | ## `dev functions apply` [#dev-functions-apply] [Changed in 1.36](/docs/reference/changelog#rayfin-136) ```bash npx rayfin dev functions apply ``` Use this subcommand when you want to run only the local Functions host against the active Fabric deployment, without starting the frontend. For the full workflow, see [Functions local development](/docs/functions/local-development). | Option | Default | Description | | ----------------------- | ------------- | --------------------------------------------------------------- | | `--port ` | `7071` | Port for the local function host. Slides forward when occupied. | | `--inspect-port ` | `9229` | Port for the Node.js inspector when debug is on. | | `--no-debug` | debug enabled | Disable the Node.js inspector on `func start`. | | `--no-emit-env` | `false` | Skip framework `.env.local` regeneration from `rayfin/.env`. | | `--verbose` | `false` | Show detailed diagnostic output. | | `--json` | `false` | Output result as JSON. | | `-y, --yes` | `false` | Run without interactive prompts. | The subcommand requires `services.functions.enabled: true`, an active deployment from `rayfin up`, Node.js 20 or later, and Azure Functions Core Tools. When Core Tools are missing, an interactive run asks for consent before installing prerequisites; a non-interactive run prints the commands to run and exits. ```prompt title="Start the Rayfin development session" From my Rayfin project root, run `npx rayfin dev --workspace ` to start the Fabric-backed local development session. If Functions are enabled, confirm the chosen Functions URL was written to RAYFIN_PUBLIC_FUNCTIONS_URL and that the frontend started on the port written to RAYFIN_PUBLIC_FRONTEND_PORT. ```