@sigx/vercel

Vercel deployment adapter for SignalX — Build Output API v3 generation, per the deployment RFC (docs/rfc-deploy.md §4.4). A pack riding @sigx/vite's public SigxAdapter seam with no privileged access; the runtime story is createFetchHandler (WinterCG-clean, CI-enforced) — everything here is build glue.

Install

pnpm add -D @sigx/vercel

Usage

// vite.config.vercel.ts
import { defineConfig } from 'vite';
import sigx from '@sigx/vite';
import { vercel } from '@sigx/vercel';

export default defineConfig({
    plugins: [sigx({ ssr: { entry: 'src/entry-server.tsx', adapter: vercel() } })]
});

vite build --app produces a fully bundled function and then generates the complete .vercel/output layout — unlike wrangler-style tools, the Build Output API is a generation contract: hand-writing it has no copyability value, so the layout is regenerated every build:

.vercel/output/
├── config.json                # routes: fn prefix → filesystem → catch-all
├── static/                    # the client outDir (minus index.html, .vite)
└── functions/_render.func/    # the bundled server + .vc-config.json

Deploy with vercel deploy --prebuilt (link the project first). Two layout choices are load-bearing:

• static/ omits index.html — the filesystem handle serves static/index.html for /, which would shadow the document render with the raw outlet template.
• The server-fn route precedes the filesystem handle — POSTs to /_sigx/fn/* must never be shadowed by files. The prefix follows sigxServer({ base }) rather than the default (#563): config.json is regenerated every build, so a moved mount would otherwise have no user-side fix on this platform.

The platform entry — yours, scaffolded once

The first build scaffolds src/entry.vercel.ts iff absent and never touches it again. The export default { fetch } shape is load-bearing on the Node runtime: Vercel's launcher detects a web handler by the fetch method on the default export — a bare default function would be treated as a legacy (req, res) handler. The composition order stays visible in your file:

static assets  →  server functions  →  document render

Options

vercel({
    // 'node' (default — Vercel's current guidance; Fluid compute) | 'edge'
    runtime: 'node',
    // .vc-config.json runtime string for the node runtime
    nodeVersion: 'nodejs22.x',
    // the platform entry, scaffolded iff absent
    entry: 'src/entry.vercel.ts'
})

For runtime: 'edge' the build resolves the edge-light/worker conditions and generate() emits a tiny wrapper entrypoint (the edge contract is a bare default fetch function; your entry keeps the { fetch } shape, identical across platforms).

Verification posture

Structural, not emulation (there is no official Build Output API emulator): CI asserts the generated layout and invokes the function's fetch export directly under Node with real Requests — exactly what Vercel's launcher calls. The reference wiring lives at examples/resume (vite.config.vercel.ts + the committed src/entry.vercel.ts).

License

MIT