Cloudflare Worker

The edge worker is a reverse proxy in front of your origin: it assigns visitors, transforms the HTML stream, and beacons exposures — with zero changes to your application.

One command

npx shiftzero deploy

The CLI scaffolds a worker wired to your dashboard, prompts for your publishable API key (stored as a Wrangler secret, never in a file), and deploys it to your Cloudflare account.

Manual setup

wrangler.jsonc

{
  "name": "shiftzero-edge",
  "main": "src/worker.ts",
  "compatibility_date": "2024-12-30",
  "vars": {
    "DASHBOARD_URL": "https://your-dashboard.example.com",
    "ORIGIN_URL": "https://origin.example.com",
    "COLLECTOR_URL": "https://collector.example.com",
    "CONFIG_TTL_MS": "30000"
  },
  // Same-account worker-to-worker calls must use a service binding:
  "services": [{ "binding": "COLLECTOR", "service": "your-collector-worker" }]
}

wrangler secret put SZ_API_KEY          # publishable dashboard key (sz_live_…)
wrangler secret put SZ_COLLECTOR_KEY    # collector write key
wrangler deploy

Configuration

Setting	Purpose
`DASHBOARD_URL`	Control plane. The worker pulls running experiments, audiences and the holdout on a 30s TTL, serving the last-good config through any control-plane blip.
`ORIGIN_URL`	Your real site. The worker proxies every request to it and transforms HTML responses.
`COLLECTOR_URL`	Where exposure + patch-health beacons go (out-of-band, never blocking the response).
`COOKIE_DOMAIN`	Optional. Set .example.com so identity persists across subdomains.
`SZ_API_KEY`	Secret. Authenticates every control-plane pull.
`SZ_COLLECTOR_KEY`	Secret. Write key stamped on every beacon so the collector only accepts authenticated events.

Cloudflare blocks a Worker from fetching another Worker’s workers.dev URL on the same account (error 1042) — and the failure is silent for fire-and-forget beacons. If your collector is a Worker on the same account, the services binding above is required, not optional.

Other platforms

The same engine runs on any JS edge: createEdgeApp from @shiftzero/edge/app with bufferingResponseTransform works on Vercel Edge and Netlify Edge Functions — the dashboard’s Setup page shows a ready-to-paste snippet with your values filled in.