Variable default

default: {
fetch(request, env, ctx): Promise<Response>;
}

Main Worker fetch handler.

Routing behavior:

OPTIONS is treated as a universal CORS preflight.
/mark-session-detection (POST) proxies to a Supabase Edge Function.
/put (POST) writes hostname routing configuration to KV for onboarding.
All other requests are proxied to an upstream base determined by KV config and request path.

Upstream selection:

Preview UI paths (/gtm/debug, /gtm/static, /gtm/preview) route to preview_origin_url when available.
All other paths route to origin_url.

Proxy rewriting:

For non-preview requests under /k/..., attempts to decode the p query param and rewrite the upstream URL.

Incoming downstream request.

Worker environment bindings.

Cloudflare execution context for waitUntil.

Proxied response.

This handler does not explicitly throw; it returns Response objects for error conditions.