Development Experience

Local development uses two composable processes — the worker runtime and the client dev server — that run concurrently.

What runs

npm run dev

The project template runs both processes via concurrently:

1. vite dev — Client dev server with HMR. Changes to Lit components reflect instantly in the browser. Configured in client/vite.config.ts.
2. bkper app dev — The worker runtime:
   • Miniflare — Simulates the single Cloudflare Worker locally.
   • Cloudflare tunnel — Exposes /events via a public URL so Bkper can route webhook events to your machine.
   • File watching — Server changes trigger automatic rebuilds via esbuild.

You can also run them independently: npm run dev:client for just the UI, or npm run dev:server for the local Worker.

URLs

Endpoint	URL
Client (Vite dev server)	http://localhost:5173
Server Worker (Miniflare)	http://localhost:8787
App API routes	http://localhost:8787/api/*
App OpenAPI spec	http://localhost:5173/openapi.json
Events (via tunnel to the same Worker)	https://<random>.trycloudflare.com/events

The Vite dev server proxies /api and /openapi.json requests to http://localhost:8787 through client/vite.config.ts, so the client and OpenAPI spec share the same local origin just as they do in production. The spec also remains available directly from the Worker at http://localhost:8787/openapi.json. The tunnel URL is automatically registered as webhookUrlDev, so development-mode events are routed to your local machine.

Configuration flags

There is one local Worker. Override its port when needed:

bkper app dev --sp 8787

Client configuration

The client dev server is configured in client/vite.config.ts. This standard Vite configuration registers local auth middleware and proxies /api and /openapi.json requests to the Worker.

Local development authentication

During local development, the Vite dev server runs createBkperAuthMiddleware() from bkper/dev. It serves the local /auth/refresh endpoint used by @bkper/web-auth, obtaining OAuth tokens from your CLI credentials.

The separate Vite proxy configuration forwards /api and /openapi.json requests to the Miniflare Worker.

Before starting development, run:

bkper auth login   # one-time setup

Then npm run dev handles local authentication. Direct bkper-js calls use auth.getAccessToken(), while the typed app API client uses auth.authenticatedFetch() to attach and refresh bearer authentication.

Local outbound uses your CLI credentials when the app server or event handler calls Bkper.

If you see authentication errors in the browser, verify you’re logged in:

bkper auth token   # should print a token

This is the canonical pattern for local development. Do not manually pass tokens or implement custom auth flows.

Local secrets

Environment variables for local development live in a .dev.vars file at the project root:

# .dev.vars (gitignored)
EXTERNAL_SERVICE_TOKEN=your-token-here

Copy from the provided template:

cp .dev.vars.example .dev.vars

These variables are available as c.env.SECRET_NAME in your Hono handlers during development.

KV storage

KV data persists locally in the .mf/kv/ directory during development. This means your data survives restarts — useful for testing caching and state patterns.

// Read
const value = await c.env.KV.get('my-key');

// Write with TTL
await c.env.KV.put('my-key', 'value', { expirationTtl: 3600 });

See the Cloudflare KV documentation for more usage patterns.

Type generation

The env.d.ts file provides TypeScript types for the Worker environment — KV bindings, secrets, and other platform services. It’s auto-generated based on your bkper.yaml configuration and checked into version control.

Rebuild it after changing services or secrets in bkper.yaml:

bkper app build

The development loop

1. Run npm run dev.
2. Edit client code and use Vite HMR.
3. Edit server code and let the Worker reload.
4. Trigger events in Bkper and inspect handler responses in the activity stream.
5. Run npm run check before considering the change complete.

Debugging

• Server errors — Check the terminal output from bkper app dev. Worker runtime errors appear here.
• Event handler errors — Check the Bkper activity stream. Click on an event handler response to see the result or error, and replay failed events.
• Client errors — Use browser DevTools. The Vite dev server provides source maps.