fix: resolve Vercel ERR_MODULE_NOT_FOUND for api/_kernel

- Inline _kernel.ts into api/index.ts to eliminate bare extensionless
  relative import ('./_kernel') that broke Node ESM resolver at Vercel runtime
- Move hono from devDependencies to dependencies (needed at serverless runtime)
- Use explicit .js extensions for relative imports (create-broker-shim.js,
  objectstack.config.js) per ESM best practice
- Delete api/_kernel.ts (content is now co-located in api/index.ts)
- Update CHANGELOG.md with 3.2.10 patch entry

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

Author: Copilot

apps/studio/CHANGELOG.md

@@ -1,5 +1,15 @@
 # @objectstack/studio
 
+## 3.2.10
+
+### Patch Changes
+
+- Fix Vercel deployment crash (`ERR_MODULE_NOT_FOUND` for `api/_kernel`)
+  - Inline `_kernel.ts` content into `api/index.ts` to eliminate the bare extensionless relative import that broke Node's ESM resolver
+  - Move `hono` from `devDependencies` to `dependencies` so it is available in the Vercel serverless runtime
+  - Use explicit `.js` file extensions for relative imports in the API entrypoint (`create-broker-shim.js`, `objectstack.config.js`) per ESM best practice
+  - Delete `api/_kernel.ts` — all kernel/service initialisation is now co-located in `api/index.ts`
+
 ## 3.2.9
 
 ### Minor Changes

apps/studio/api/_kernel.ts

@@ -3,19 +3,152 @@
 /**
  * Vercel Serverless API Entrypoint (Hono + Vercel Node Adapter)
  *
- * Top-level Hono app that delegates all /api/* requests to the
- * ObjectStack Hono application. The kernel boots lazily on the first
- * request and persists across warm invocations.
+ * Top-level Hono app that boots the ObjectStack kernel lazily on the first
+ * request and delegates all /api/* traffic to the ObjectStack Hono adapter.
  *
- * Vercel's `vercel.json` rewrites route all `/api/*` traffic to this
- * single function — no catch-all `[...path].ts` is needed.
+ * All kernel/service initialisation is co-located here so there are no
+ * extensionless relative module imports — which would break Node's ESM
+ * resolver when deployed to Vercel (`"type": "module"` package).
  *
  * @see https://hono.dev/docs/getting-started/vercel
  */
 
+import { ObjectKernel, DriverPlugin, AppPlugin } from '@objectstack/runtime';
+import { ObjectQLPlugin } from '@objectstack/objectql';
+import { InMemoryDriver } from '@objectstack/driver-memory';
+import { createHonoApp } from '@objectstack/hono';
 import { Hono } from 'hono';
 import { handle } from 'hono/vercel';
-import { ensureApp } from './_kernel';
+import { createBrokerShim } from '../src/lib/create-broker-shim.js';
+import studioConfig from '../objectstack.config.js';
+
+// ---------------------------------------------------------------------------
+// Singleton state — persists across warm Vercel invocations
+// ---------------------------------------------------------------------------
+
+let _kernel: ObjectKernel | null = null;
+let _app: Hono | null = null;
+
+/** Shared boot promise — prevents concurrent cold-start races. */
+let _bootPromise: Promise<ObjectKernel> | null = null;
+
+// ---------------------------------------------------------------------------
+// Kernel bootstrap
+// ---------------------------------------------------------------------------
+
+/**
+ * Boot the ObjectStack kernel (one-time cold-start cost).
+ *
+ * Uses a shared promise so that concurrent requests during a cold start
+ * wait for the same boot sequence rather than starting duplicates.
+ */
+async function ensureKernel(): Promise<ObjectKernel> {
+    if (_kernel) return _kernel;
+    if (_bootPromise) return _bootPromise;
+
+    _bootPromise = (async () => {
+        console.log('[Vercel] Booting ObjectStack Kernel (server mode)...');
+
+        try {
+            const kernel = new ObjectKernel();
+
+            await kernel.use(new ObjectQLPlugin());
+            await kernel.use(new DriverPlugin(new InMemoryDriver(), 'memory'));
+            await kernel.use(new AppPlugin(studioConfig));
+
+            // Broker shim — bridges HttpDispatcher → ObjectQL engine
+            (kernel as any).broker = createBrokerShim(kernel);
+
+            await kernel.bootstrap();
+
+            // Validate broker attachment
+            if (!(kernel as any).broker) {
+                console.warn('[Vercel] Broker shim lost during bootstrap — reattaching.');
+                (kernel as any).broker = createBrokerShim(kernel);
+            }
+
+            // Seed data from config (non-fatal — the kernel is usable without seed data)
+            try {
+                await seedData(kernel, [studioConfig]);
+            } catch (seedErr: any) {
+                console.warn('[Vercel] Seed data failed (non-fatal):', seedErr?.message || seedErr);
+            }
+
+            _kernel = kernel;
+            console.log('[Vercel] Kernel ready.');
+            return kernel;
+        } catch (err) {
+            // Clear the lock so the next request can retry
+            _bootPromise = null;
+            console.error('[Vercel] Kernel boot failed:', (err as any)?.message || err);
+            throw err;
+        }
+    })();
+
+    return _bootPromise;
+}
+
+/**
+ * Seed records defined in app configs into the ObjectQL engine.
+ */
+async function seedData(kernel: ObjectKernel, configs: any[]) {
+    const ql = (kernel as any).context?.getService('objectql');
+    if (!ql) return;
+
+    const RESERVED_NS = new Set(['base', 'system']);
+    const toFQN = (name: string, namespace?: string) => {
+        if (name.includes('__') || !namespace || RESERVED_NS.has(namespace)) return name;
+        return `${namespace}__${name}`;
+    };
+
+    for (const appConfig of configs) {
+        const namespace = (appConfig.manifest || appConfig)?.namespace as string | undefined;
+
+        const seedDatasets: any[] = [];
+        if (Array.isArray(appConfig.data)) {
+            seedDatasets.push(...appConfig.data);
+        }
+        if (appConfig.manifest && Array.isArray(appConfig.manifest.data)) {
+            seedDatasets.push(...appConfig.manifest.data);
+        }
+
+        for (const dataset of seedDatasets) {
+            if (!dataset.records || !dataset.object) continue;
+
+            const objectFQN = toFQN(dataset.object, namespace);
+
+            let existing = await ql.find(objectFQN);
+            if (existing && (existing as any).value) existing = (existing as any).value;
+
+            if (!existing || existing.length === 0) {
+                console.log(`[Vercel] Seeding ${dataset.records.length} records for ${objectFQN}`);
+                for (const record of dataset.records) {
+                    await ql.insert(objectFQN, record);
+                }
+            }
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Hono app factory
+// ---------------------------------------------------------------------------
+
+/**
+ * Get (or create) the Hono application backed by the ObjectStack kernel.
+ * The prefix `/api/v1` matches the client SDK's default API path.
+ */
+async function ensureApp(): Promise<Hono> {
+    if (_app) return _app;
+
+    const kernel = await ensureKernel();
+    _app = createHonoApp({ kernel, prefix: '/api/v1' });
+    return _app;
+}
+
+// ---------------------------------------------------------------------------
+// Vercel handler
+// ---------------------------------------------------------------------------
 
 const app = new Hono();
 
@@ -38,3 +171,4 @@ app.all('*', async (c) => {
 });
 
 export default handle(app);
+

apps/studio/api/index.ts

@@ -26,6 +26,7 @@
     "@objectstack/plugin-msw": "workspace:*",
     "@objectstack/runtime": "workspace:*",
     "@objectstack/spec": "workspace:*",
+    "hono": "^4.12.8",
     "@radix-ui/react-avatar": "^1.1.11",
     "@radix-ui/react-checkbox": "^1.3.3",
     "@radix-ui/react-collapsible": "^1.1.12",
@@ -57,7 +58,6 @@
     "@vitejs/plugin-react": "^6.0.1",
     "autoprefixer": "^10.4.27",
     "happy-dom": "^20.8.4",
-    "hono": "^4.12.8",
     "msw": "^2.12.13",
     "postcss": "^8.5.8",
     "tailwindcss": "^4.2.1",