fix: output serverless function to dist/api/index.js to match Vercel outputDirectory

The bundle-api.mjs script was emitting api/index.js at the project root, but
vercel.json sets outputDirectory: "dist" — so Vercel could not discover the
serverless function and fell back to the SPA HTML route for all /api/* requests.

- Change esbuild outfile from api/index.js to dist/api/index.js
- Add explicit functions config in vercel.json with @vercel/node@3 runtime
- Remove obsolete .gitignore entries for api/index.js (now under dist/)
- Update changeset and CHANGELOG

Fixes #1002

Agent-Logs-Url: https://github.com/objectstack-ai/spec/sessions/24bf6f10-3ca1-4cff-a9cb-c6c0905d1845

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

.changeset/fix-vercel-api-html-response.md

@@ -4,15 +4,14 @@
 
 Fix Vercel deployment API endpoints returning HTML instead of JSON.
 
-Replace the custom `getRequestListener` export in `server/index.ts` with the
-standard `handle()` adapter from `@hono/node-server/vercel` and the
-outer→inner Hono delegation pattern (`inner.fetch(c.req.raw)`).
+The `bundle-api.mjs` script was emitting the serverless function to `api/index.js`
+at the project root, but `vercel.json` sets `outputDirectory: "dist"` — causing
+Vercel to never find the function entrypoint and fall back to the SPA HTML route
+for all `/api/*` requests.
 
-- The `handle()` adapter correctly wraps the Hono app with the
-  `(IncomingMessage, ServerResponse) => Promise<void>` signature that
-  Vercel's Node.js runtime expects for serverless functions in `api/`.
-- `@hono/node-server/vercel`'s `getRequestListener()` already handles
-  Vercel's pre-buffered `rawBody` natively, removing the need for the
-  custom body-extraction helper.
-- The outer→inner delegation pattern matches the documented ObjectStack
-  Vercel deployment guide and the `@objectstack/hono` adapter test suite.
+- Change esbuild `outfile` from `api/index.js` to `dist/api/index.js` so the
+  bundled serverless function lands inside the Vercel output directory.
+- Add explicit `functions` config in `vercel.json` pointing to `api/index.js`
+  (relative to `outputDirectory`) with `@vercel/node@3` runtime.
+- Remove obsolete `.gitignore` entries for `api/index.js` and `api/index.js.map`
+  (now emitted under `dist/` which is already git-ignored).

CHANGELOG.md

@@ -39,6 +39,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   to `:memory:` (ephemeral SQLite). This ensures data persistence across serverless function
   invocations on Vercel. The browser MSW mock kernel remains unchanged (InMemoryDriver).
 
+### Fixed
+- **Vercel API always returns HTML — serverless function entrypoint not found** — The `bundle-api.mjs`
+  script was emitting `api/index.js` at the project root, but `vercel.json` sets `outputDirectory: "dist"`,
+  so Vercel could not discover the serverless function and fell back to the SPA HTML route for all
+  `/api/*` requests. Changed esbuild `outfile` to `dist/api/index.js` and added explicit `functions`
+  config in `vercel.json` with `@vercel/node@3` runtime.
+
 ### Added
 - **Batch schema sync for remote DDL in kernel bootstrap** — `ObjectQLPlugin.syncRegisteredSchemas()`
   now groups objects by driver and uses `syncSchemasBatch()` when the driver advertises

apps/studio/.gitignore

@@ -6,8 +6,6 @@ pnpm-lock.yaml
 dist
 build
 *.tsbuildinfo
-api/index.js
-api/index.js.map
 
 # Development
 .vite

apps/studio/scripts/bundle-api.mjs

@@ -37,11 +37,11 @@ await build({
   platform: 'node',
   format: 'esm',
   target: 'es2020',
-  outfile: 'api/index.js',
+  outfile: 'dist/api/index.js',
   sourcemap: true,
   external: EXTERNAL,
   // Silence warnings about optional/unused require() calls in knex drivers
   logOverride: { 'require-resolve-not-external': 'silent' },
 });
 
-console.log('[bundle-api] Bundled server/index.ts → api/index.js');
+console.log('[bundle-api] Bundled server/index.ts → dist/api/index.js');

apps/studio/vercel.json

@@ -4,6 +4,11 @@
   "installCommand": "cd ../.. && pnpm install",
   "buildCommand": "cd ../.. && pnpm turbo run build --filter=@objectstack/studio && cd apps/studio && node scripts/bundle-api.mjs",
   "outputDirectory": "dist",
+  "functions": {
+    "api/index.js": {
+      "runtime": "@vercel/node@3"
+    }
+  },
   "build": {
     "env": {
       "VITE_RUNTIME_MODE": "server",