Symptom: in Chrome on certain networks the scene <img> renders row-by-row
from top to bottom — "层层加载" — instead of appearing atomically.
Root cause (confirmed via DevTools):
- Chrome opportunistically opens HTTP/3 (QUIC) to im.runware.ai.
- QUIC streams to Runware sometimes error mid-transfer:
net::ERR_QUIC_PROTOCOL_ERROR
HTTP-level status stays 200 (response headers received), but bytes are
truncated. The browser paints whatever PNG bytes it has so far → visible
row-by-row decode.
- The earlier preloadImage()+decode() trick can't fix this — neither
HTTP-cache reuse nor sync decode helps when the bytes themselves were
never fully delivered.
Two-tier fix:
1. Client: fetch → Blob → URL.createObjectURL() (app/play/page.tsx)
- <img src> only ever points to a blob: URL whose bytes are 100%
resident in the JS heap. No network-backed src = no possibility of
progressive paint.
- Module-level blobUrlCache keys by original URL so speculative
prefetch + the eventual commit share one fetch.
- Old blobs are URL.revokeObjectURL()'d on scene swap + unmount to
release memory.
2. Network: optional Cloudflare Worker proxy (worker/)
- Browser ↔ Worker is HTTP/2 over CF edge (extremely stable).
- Worker ↔ Runware is a server-to-server fetch (no QUIC fragility,
Cloudflare's backbone handles transit).
- Worker buffers the full upstream response → client never sees a
half-stream.
- Bonus: CF edge cache (cacheEverything, 1y TTL) on Runware UUIDs;
Access-Control-Allow-Origin: * so client fetch() can't hit CORS.
- Hardened: only proxies im.runware.ai, only GET/HEAD/OPTIONS, all
other hosts/methods → 403/405.
Wired via NEXT_PUBLIC_IMAGE_PROXY_URL (inlined at build). Empty → no proxy
→ direct fetch (which still uses the blob path, just exposed to QUIC).
──────────────────────────────────────────────────────────────────────
Deploy steps (one-time, do this AFTER pulling this commit):
1. Install wrangler globally:
npm i -g wrangler
2. Log in to Cloudflare (opens browser for OAuth):
wrangler login
3. From the worker/ directory, deploy:
cd worker
wrangler deploy
wrangler will print the deployed URL, e.g.
https://infiplot-image-proxy.<your-cf-username>.workers.dev
4. Paste that URL into .env.local for local dev:
NEXT_PUBLIC_IMAGE_PROXY_URL=https://infiplot-image-proxy.<...>.workers.dev
…and into Vercel project settings (Environment Variables) for prod.
NEXT_PUBLIC_ vars are inlined at build time, so the URL bakes into
the bundle on the next deploy/dev-server restart.
5. Restart dev server (pnpm dev) so the new env baked in. Generate a
scene; Network tab should show requests going to *.workers.dev
instead of im.runware.ai, no ERR_QUIC_PROTOCOL_ERROR, image renders
atomically.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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