# Handler Pattern Every app deployed on onvibe runs inside a managed server. Your code must export a default handler function — do NOT call Deno.serve() yourself. ## Correct pattern ```typescript export default async function handler(req: Request): Promise { const url = new URL(req.url); if (url.pathname === "/") { return new Response("Hello from onvibe!", { headers: { "content-type": "text/plain" }, }); } return new Response("Not found", { status: 404 }); } ``` ## With context (env vars) ```typescript interface Context { env: Readonly>; } export default async function handler(req: Request, ctx: Context): Promise { const appURL = ctx.env.APP_URL; return new Response("Running at " + appURL); } ``` ## HTML responses — always use template literals Use backtick template literals (`` ` ``) for HTML. They support multiline content, avoid quote escaping inside attributes, and allow `${expression}` interpolation: ```typescript export default async function handler(req: Request): Promise { const name = "world"; const html = ` My App

Hello, ${name}!

About `; return new Response(html, { headers: { "content-type": "text/html; charset=utf-8" }, }); } ``` With regular strings you would need to escape every `"` inside attributes (`class=\"title\"`). With template literals there is no escaping at all — use `"` for HTML attributes and `'` or `${...}` inside them freely. ## Rules - File must be named **main.ts** - Must have **export default** — named exports are ignored - The function receives (Request, Context?) and returns Promise - **Never call Deno.serve()** — causes a crash on startup (status 0 in check_app) - **Never call Deno.exit()** — terminates the server - Top-level await is allowed (e.g. for DB pool initialization) ## Available env vars (injected automatically) | Variable | Value | |---|---| | APP_URL | Public URL of this app | | APP_ID | Internal app identifier | | DATABASE_URL | PostgreSQL connection string (provisioned automatically for every project) |