Fix PDF export on Vercel via serverless Chromium fallback

[lukasfehling]

Closes #9.
Closes #7 as duplicate — both issues describe the same root cause (Puppeteer's bundled Chromium not working on Vercel). This PR fixes it in-process instead of outsourcing rendering.

Summary

• Auto-detect serverless runtime (VERCEL / AWS_LAMBDA_FUNCTION_NAME) and fall back to puppeteer-core + @sparticuz/chromium; non-serverless paths (Node / Docker / VPS / Railway / Fly.io) keep the full puppeteer bundle unchanged.
• Keeps the infrastructure single-service — no external PDF renderer required.
• maxDuration = 60 on the PDF route (Vercel Pro / Fluid Compute; Hobby's 10 s is too short).
• Cleaner internal-URL resolution: INTERNAL_APP_URL → VERCEL_URL → NEXT_PUBLIC_APP_URL → localhost, and TLS is only stripped for real localhost hostnames (not for public Vercel URLs).

Root cause (covers #9 and #7)

puppeteer bundles ~170 MB of Chromium. Vercel's function size limit is 50 MB unzipped, so the binary was missing at runtime and every PDF request failed with Serverfehler — bitte versuchen Sie es später erneut.

• PDF Export doesn't work #9 reports the user-visible symptom (Serverfehler on Export).
• Add possibility to outsource pdf generation #7 reports the same underlying constraint (Puppeteer won't run on Vercel) and proposes outsourcing to an external service as a solution.

Both are resolved by swapping in @sparticuz/chromium when the process detects a serverless runtime — no external service needed.

Why this approach (vs. an external renderer as proposed in #7)

Discussed with @JakeLeoDev in-thread — the project's value proposition is a slim stack (Next.js + Supabase). Spinning up a Gotenberg/Browserless service just for PDF is infrastructure bloat at Proposit's target usage volume. @sparticuz/chromium stays single-service, fixes Vercel, and keeps the render target as the app's own /proposals/[id]/pdf page — so PDF output still matches the on-screen preview byte-for-byte.

The external-renderer path from #7 remains reasonable for high-volume / multi-tenant-scale deployments and could be added later as an opt-in (PDF_RENDERER_URL) without disturbing the default. If / when that need materialises, a new issue should be filed with concrete scale numbers.

What changed

• lib/pdf/launch.ts (new) — launchBrowser(), resolveInternalAppUrl(), isServerlessRuntime().
• app/api/proposals/[id]/pdf/route.ts — uses the launcher + maxDuration = 60.
• next.config.ts — serverExternalPackages: ['puppeteer', 'puppeteer-core', '@sparticuz/chromium'].
• lib/pdf/__tests__/launch.test.ts (new) — 11 unit tests covering env precedence + runtime branch selection.
• context/pdf-export-testing.md (new) — manual smoke-test checklist per rendering tier.
• .env.example (new) — was referenced in CLAUDE.md but missing from the repo; .gitignore amended with !.env.example.
• README.md / CLAUDE.md — deployment + convention notes.
• Brings in the minimal vitest setup (config + scripts) that the new unit tests need.

Test plan

@JakeLeoDev — bitte um Testing. Die Tiers sind in context/pdf-export-testing.md dokumentiert. Kurzform:

• pnpm install && pnpm test lib/pdf — 11 unit tests should pass
• pnpm build — should succeed without Chromium/bundler warnings
• Tier 2 (local / VPS path): pnpm dev, open an existing proposal, Export PDF → downloads in ~3-8 s, matches on-screen preview
• Tier 1 (Vercel path): deploy the branch to a Vercel Preview (Pro plan or Fluid Compute), open a non-trivial proposal, Export PDF → downloads within ~20-40 s without Serverfehler
• Verify no [PDF] requestfailed / [PDF] response >=400 in Vercel function logs during the successful export
• Spot-check PDF visuals: fonts, images, collection tables not cut mid-row, light mode enforced

Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com

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Project	Deployment	Actions	Updated (UTC)
proposit	Ready	Preview, Comment	Apr 24, 2026 3:24pm