Marco Sadjadi 092290bb38
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fix(preview/stream): await onSpec/onError handlers
The llm package called the user-supplied onSpec/onError handlers
without awaiting them. In the /preview/stream route onSpec is async
(it does `await cacheSpec(...)` then writes the SSE `spec` event), so
the api handler's `await streamSpecFromAnthropic(...)` returned BEFORE
the terminal event had been written. The route's finally block then
ran `reply.raw.end()`, the queued `send('spec', ...)` hit a closed
stream and silently no-op'd, and the browser saw zero terminal
events — frontend ran into the "Spec generation failed." fallback
even though Anthropic had delivered a perfectly valid spec.

Verified against prod log: req-8 ran 66s with 200 and produced no
preview_spec_* log line, which is exactly the success-but-event-lost
signature.

Fix:
- StreamHandlers.onSpec / onError typed as Promise<void> | void
- Both call sites in streamSpecFromAnthropic now `await` them
- /preview/stream sets `resolved = true` at the END of each handler
  (after the SSE write completes) so the post-stream "unresolved"
  fallback only fires on a genuine programming bug
- Added preview_spec_ready info log on the happy path so future
  diagnosis doesn't have to infer success from the absence of error
  logs
2026-05-28 22:00:03 +02:00

BuildMyMCPServer

Describe your tool. We host the server. AI uses it.

Prompt-to-production MCP servers with OAuth 2.1 and Streamable HTTP. Production-grade infrastructure for hosting Model Context Protocol servers your AI clients (Claude Desktop, Cursor, ChatGPT) can install with a copy-paste snippet.

Quick start

# 1. Install
pnpm install

# 2. Copy env. Defaults work for local dev. Set ANTHROPIC_API_KEY if you want real generation.
cp .env.example .env

# 3. Boot everything
pnpm dev

pnpm dev will:

  1. Load .env.
  2. docker compose up -d --wait postgres + redis.
  3. Push the Drizzle schema (drizzle-kit push --force).
  4. Start the full stack in parallel: web (Next.js, :3000), api (Fastify, :4000), generator (BullMQ worker).

Then open:

Click Start building, enter your email, copy the magic-link URL printed to the api terminal output, paste it in your browser. You land on /dashboard. Click New server, paste a prompt, and watch the build stream live over WebSocket.

If ANTHROPIC_API_KEY is unset, the generator returns a deterministic mock spec (an echo and a now tool) so the full end-to-end flow stays demoable.

If Docker is unavailable, the build will fail at the deploy step with a clear error. Otherwise: a fresh container is launched on a host port from RUNNER_PORT_RANGE_START…RUNNER_PORT_RANGE_END, the server is marked live, and the dashboard renders install snippets for Claude Desktop, Cursor and ChatGPT.

Architecture

See BuildMyMCPServer_MASTER_PROMPT.md for the full specification and CHOICES.md for decisions made during this Sprints 13 build.

apps/
  web/              Next.js 15 dashboard + marketing landing
  api/              Fastify control plane (auth, server CRUD, OAuth 2.1 AS, JWKS, WS stream)
  generator/        BullMQ worker — Claude → spec → render → docker build → local deploy
  runner-template/  Hosted MCP server template (Streamable HTTP + OAuth 2.1 RS)
packages/
  db/               Drizzle schema + client
  auth/             Magic-link + session
  types/            Shared Zod contracts

Scripts

Command Effect
pnpm dev Bootstrap + parallel dev for web, api, generator
pnpm dev:no-docker Skip docker-compose (assumes postgres + redis already up)
pnpm build Turbo build all apps
pnpm typecheck Turbo typecheck all apps
pnpm lint Biome check
pnpm lint:fix Biome check --write
pnpm db:push Push schema to postgres (drizzle-kit)
pnpm db:generate Generate SQL migration files
pnpm db:migrate Apply pending migrations
pnpm stop docker compose down

Acceptance check

After pnpm dev is up:

  • http://localhost:3000 renders the landing page.
  • http://localhost:4000/health returns { "ok": true }.
  • Sign in via magic link (URL printed in the api terminal).
  • New Server → paste prompt → live WebSocket stream queued → generating → building → deploying → live.
  • If Docker is running, a container is launched and http://localhost:<port>/mcp responds 401 + WWW-Authenticate without a token, 200 with a valid token issued by /oauth/token.
  • Install snippets render with copy buttons for Claude Desktop, Cursor, ChatGPT.

Repo conventions

  • TypeScript strict, zero any (Biome lints noExplicitAny as error).
  • ESM-only, Node 20 LTS.
  • Conventional commits.
  • Tailwind v4 (@import 'tailwindcss').
  • Geist + Geist Mono.
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