meshcheck goes public: an MCP server, a demo you can't scrape clean, a 9.7-second gate

What shipped

Phase 3 made meshcheck usable by someone who isn’t us. meshcheck-mcp is a real npm package (unpublished, by decision): four tools over the official SDK — validate_model, render_model with up to three inline base64 stills, inspect_model (passes through the Phase-4-pending API error verbatim), get_report — with ~/CWD path resolution, plan-cap size routing into the presigned Blob flow, and transparent 2-second job polling so agents never see a 202 envelope.

The API grew its one public unauthenticated route: POST /v1/demo/validate, multipart-only, 5/hour/IP token bucket spent before body parsing, authenticating internally as a demo-plan account via a server-held key. Every rendering path watermarks demo-plan output with a procedural “MESHCHECK DEMO” stamp — a hardcoded 5×7 bitmap font, zero dependencies, applied only after render_hash and RND evidence are computed from the pristine buffer.

The Astro site (landing, five docs pages, two cookbook drafts, the drag-and-drop demo island at 12.99 KB gzipped) deploys inside the same Vercel project as static output. Production was promoted at phase start and redeployed at phase close with everything above; meshcheck.dev and api.meshcheck.dev are attached pending registrar DNS.

Decisions

The frontmatter list is the record; two deserve context. The watermark placement question — route flag vs plan property — looks small but decides whether a leaked demo key matters. We put the invariant on the plan so routes/validate, routes/render, and both async runners all force it from plan.name === 'demo'; the demo route is just another caller. And the site/API cohabitation hinged on one Vercel routing fact: the filesystem wins over rewrites. Rather than trusting ourselves to never add a static llms.txt, the site build fails if any API-owned path appears in its output — the reviewer proved the guard fires by planting one.

What broke

Piping the demo key into vercel env add from PowerShell stored an empty value while reporting success. Diagnosis was doubly masked: vercel env ls lists the variable normally, and vercel env pull writes empty for sensitive-typed vars by design. The deployed route returned “demo not configured” against a provably correct database — the split test that cracked it was using the same key as a normal X-Api-Key header against the same deployment (200) while the env-dependent path 500’d. Re-adding via bash printf fixed it. Two preview deploys were burned bisecting this.

Smaller: astro dev’s on-demand TSX transform intermittently failed to hydrate the demo island, so click-through testing moved to the built bundle behind a same-origin mock; Astro’s default image service wanted sharp (we pass through pre-sized images instead); the first Lighthouse pass scored a11y 0.94 for heading order and an unlabeled file input, fixed to 1.0; and the reviewer’s first demo-gate Playwright run set the file before the client:visible island had hydrated — scroll first, then drop.

Numbers

All four Phase 3 BENCHMARKS rows measured on deployed production. The demo gate is the honest squeaker: 9,675 ms from file-drop to six loaded screenshots for a 3.77 MB texture-heavy PBR asset on a cold render — inside the 10-second target with 3% to spare, and consistent with Phase 2’s sequential full-validate p95 of 6.6 s plus upload and image delivery. Lighthouse came back 100 across all four categories on both the implementer’s preview run and the reviewer’s independent deployed run. The MCP integration suite (21 tests) runs against production in ~9 s and burns ~23 credits per cycle. The e2e transcript gate recorded a four-turn session in which the agent, given only the MCP server, named the planted defect and its exact measurements.

Next

Phase 4 is billing and launch: Paddle sandbox lifecycle against the credit ledger, the /inspect vision endpoint, registry submissions (npm publish unblocks the npx meshcheck-mcp story), and the 48-hour staging soak. The smoke/loadtest accounts and the phase smoke key get revoked before launch.