Local development commands

Run your project locally with helix dev, pick a port and a log format, and see how local storage and auth differ from production.

helix dev runs your project on your machine with hot reload, serving on http://localhost:3000 by default. It’s the only local-development command in the CLI: everything else you’d do while building (adding functions, testing routes, reading logs) happens in your editor, in Claude, or with an HTTP client.

helix dev

helix dev

Starts the local dev server and watches your files, reloading as you save. Stop it with Ctrl+C.

Flag	What it does
`-p, --port <number>`	Serve on this port instead of 3000
`--pretty-logs`	Format logs for humans. This is the default
`--raw-logs`	Print raw OpenTelemetry JSON instead of formatted logs

helix dev --port 4000
helix dev --raw-logs

Use --raw-logs when you want the full structured record: trace and span IDs, severity, and every attribute, exactly as the platform receives it. --pretty-logs shows the same records formatted to read at a glance.

Testing routes locally

Send requests to the dev server with any HTTP client:

curl http://localhost:3000/api/v1/users

How local differs from production

Local runs are close to production but not identical. Two differences matter while you’re building:

Key-value storage is in memory. Local KV lives in the dev server’s process and resets every time you restart helix dev. Data you write locally does not persist between runs, and it never reaches the deployed project. To read and write the project’s provisioned, persistent KV, set the project ID first with helix project set <id>. See the key-value store guide.

Authentications resolve differently. How the local dev server resolves an auth alias to a credential is not the same path a deployed function takes. Aliases that work locally can behave differently once deployed, so test authenticated calls against a real deploy before you rely on them.