fix(mcp-server): make Vercel deployment actually work#79
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Vercel was running our Docker-oriented "bun run build" (which produces dist/) and then erroring with "No Output Directory named 'public' found" because no public/ exists. The MCP server on Vercel only needs the serverless function at api/index.ts — the @vercel/node builder compiles it automatically; we don't need a separate build step. Removing buildCommand, installCommand, and framework lets Vercel auto-detect bun (via bun.lock) and treat the project as serverless-only, which is what we actually want. This change was part of #78 but was dropped during the squash-merge. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The previous setup had api/index.ts with heavy imports from @modelcontextprotocol/sdk. @vercel/node's TypeScript compilation hung indefinitely on it (the SDK types OOM tsc even locally with a 4 GB heap). Move the handler to src/vercel-handler.ts so it's compiled to plain JavaScript by our existing `bun run build` step, and replace api/index.ts with a one-line ESM wrapper that re-exports the compiled default from ../dist/vercel-handler.js. @vercel/node now sees only plain JS in api/ and bundles in milliseconds. vercel.json: - Add buildCommand: "bun run build" so dist/ is produced before functions are bundled - Add outputDirectory: "." so Vercel stops expecting public/ - Register the function under its new path (api/index.js) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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The Vercel handler is only ever used for HTTP transport, but loadConfig() defaults to stdio mode when MCP_TRANSPORT is unset, which then errors on the missing CAL_API_KEY. Set MCP_TRANSPORT=http on the process env before loading so operators do not have to remember to configure it in the Vercel dashboard. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
`export const sql = pool.sql;` destructured the tagged-template method off the pool, losing the `this` binding. On Vercel that surfaced as "Cannot read properties of undefined (reading 'connectionString')" because @vercel/postgres reads `this.config.connectionString` lazily at call time. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Cal.com's OAuthClient (user-facing) rejects authorize requests that omit the scope parameter: "scope parameter is required for this OAuth client". Add a new CAL_OAUTH_SCOPES env var (space-separated) that defaults to the full set of User-level scopes the MCP tools rely on (event types, bookings, schedules, apps, profile — read + write). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Browsers reject Access-Control-Allow-Origin: * when the request carries an Authorization header (credentialed request). Echo the request's Origin header instead and add Access-Control-Allow-Credentials. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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…meout The default StreamableHTTP transport uses SSE streaming (ReadableStream that stays open until all events are flushed). On Vercel serverless, that stream never closes naturally, causing every POST /mcp to time out after the 60-second function limit. Setting enableJsonResponse: true switches to plain-JSON mode: the transport resolves immediately after processing each JSON-RPC request and writes a single JSON body, which completes well within the function time limit. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…GET SSE on Vercel Two issues caused the MCP client to get stuck after OAuth: 1. CORS preflight failure: the MCP client sends `mcp-protocol-version` and `last-event-id` as custom headers on every request after initialization. These were missing from Access-Control-Allow-Headers, so the browser's preflight rejected any request that included them (CORS error in DevTools). 2. Pending GET /mcp forever: after the `initialized` notification is acknowledged, the MCP client opens a GET SSE stream for server-initiated messages. On Vercel, that stream can never close (no persistent connections), so it stayed pending until the 60 s function timeout. Per the MCP spec, a 405 response to GET tells the client "SSE not supported here" and it falls back gracefully to POST-only mode — no error thrown. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…tadata URL Claude.ai sends MCP requests directly to the URL the user enters. If the user enters "https://mcp.cal.com" (no /mcp suffix), all MCP POSTs land at "/" and our handler returned 404 because it only matched "/mcp". Two fixes: 1. The /mcp handler now also matches "/" so both base URL and explicit /mcp endpoint work transparently. 2. buildProtectedResourceMetadata now sets resource to "${serverUrl}/mcp" (the canonical MCP endpoint) so that clients that derive the endpoint from the resource field also get the correct path. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…tadata
Changing resource to "${serverUrl}/mcp" was wrong. Per RFC 9728 §3,
the client constructs the discovery URL by inserting
/.well-known/oauth-protected-resource before any path segment:
resource "https://mcp.cal.com/mcp"
→ discovery URL: https://mcp.cal.com/.well-known/oauth-protected-resource/mcp
That path doesn't exist, so Claude.ai got a 404 and authorization failed.
Keep resource as the plain base URL so discovery stays at the working path:
https://mcp.cal.com/.well-known/oauth-protected-resource
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…s Vercel timeout StreamableHTTPServerTransport internally uses @hono/node-server's adapter, which converts the response body to a Web ReadableStream and then awaits `reader.closed`. On Vercel serverless functions that promise never resolves, causing every POST /mcp request to hang until the 60 s hard limit. Replace it with a minimal in-process Transport: read the body with plain Node.js streams, wire a trivial Transport object directly to McpServer, drive messages in and collect responses out, then write JSON to `res` with res.writeHead/res.end. No ReadableStream, no Hono adapter, no reader.closed. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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The "Apply suggestions from code review" commit (5370168) accidentally added an extra `},` after the `send()` method's closing brace, producing a syntax error that broke Lint, Type Check and the Vercel build. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The combination of the MCP SDK types and zod-schema tool definitions pushes tsc past the default 2 GB heap on CI's 2-vCPU Blacksmith runner, failing Type Check with 'Ineffective mark-compacts near heap limit'. Raising the limit via NODE_OPTIONS keeps the check green without restructuring the type graph. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The Vercel handler is an entry point that imports registerTools, which transitively drags in the MCP SDK + every zod tool schema. Running tsc over it blows past even a 4 GB heap on CI, same reason src/index.ts, src/register-tools.ts and src/http-server.ts are already excluded. Treating vercel-handler.ts the same way fixes the CI OOM without touching the type graph. Reverts the NODE_OPTIONS heap bump from the previous commit since it wasn't enough anyway. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
Fixes the Vercel deployment that was hanging at TypeScript compilation of
api/index.ts. The root cause:@vercel/noderuns TypeScript over the function's dep graph, which OOMs on@modelcontextprotocol/sdk's large types.Fix
src/vercel-handler.tsso it's compiled by our existingbun run buildstep intodist/vercel-handler.jsapi/index.tswith a one-line JS wrapper (api/index.js) that re-exports from the compiled output@vercel/nodenow sees only plain JS inapi/— no TypeScript compilation, no OOMvercel.json:buildCommand: "bun run build"sodist/exists before functions are bundledoutputDirectory: "."so Vercel stops demanding apublic/folderapi/index.jsVercel dashboard
With
vercel.jsonnow controlling build + output, Framework Settings overrides can all be turned off. Only settings that still matter in the dashboard:apps/mcp-serverDATABASE_URL,CAL_OAUTH_CLIENT_ID,CAL_OAUTH_CLIENT_SECRET,TOKEN_ENCRYPTION_KEY,MCP_SERVER_URL,MCP_TRANSPORT=httpTest plan
bun run build— producesdist/vercel-handler.jsbun run test— 203 tests pass/health🤖 Generated with Claude Code