u

docs/api/routes-all.md

@@ -684,7 +684,7 @@ _none_
 - Returns: `200 str`
 #### Execute a virtual filesystem applet — `POST /vfs/{*path}`
 - Params: `path: str, body?: { input?: {}, timeout?: int, max_output?: int }`
-- Returns: `200 { ok: bool, result: any|null, stdout: str, consoleLines: int, durationMs: int, truncated?: bool, truncationNote?: str }`
+- Returns: `200 { ok: bool, result: str, columns: { name: str, type: str }[], rows: int, stdout: str, consoleLines: int, durationMs: int, warnings?: str[], truncated?: bool, truncationNote?: str }`
 #### Create or overwrite a virtual filesystem file — `PUT /vfs/{*path}`
 - Params: `path: str, body: { content: str, mime?: str }`
 - Returns: `200 { success: bool, file: { name: str, size: int, mime: str, updated_at: str } }`

docs/api/routes/vfs/exec.md

@@ -9,10 +9,17 @@ and returns the exported function's result.
 
 The applet file must begin with two metadata lines:
 `// @applet-input-schema {JSON Schema}` followed by
-`// @applet-output-schema {JSON Schema}`. The file exports a function that receives the posted `input`
-as `applet_input`, and execution runs in the same isolated worker sandbox as the `javascript_execute`
-tool — including authenticated `fetch()` against this API, `fs`/`vfs`, `sharp`, ExcelJS, PDFKit and
-WebCrypto globals.
+`// @applet-output-schema {name:type;name:type}`. The input schema describes the GUI form posted as
+`input`. The output line declares the RESULT COLUMNS as typed CSV — `name:type` pairs separated by `;`
+(e.g. `id:integer;name:string;active:boolean`); allowed types are `string`, `integer`, `number`,
+`boolean` and `date`. The applet exports a function that receives the posted `input` as `applet_input`
+and returns a row object (or an array of row objects) keyed by those columns.
+
+Applets return typed CSV, not JSON: `result` is a `;`-separated CSV string with a header row, and the
+response also carries `columns` (name/type) and `rows` (data row count). Only declared columns are
+emitted, in header order; missing values become empty cells. Execution runs in the same isolated worker
+sandbox as the `javascript_execute` tool — including authenticated `fetch()` against this API,
+`fs`/`vfs`, `sharp`, ExcelJS, PDFKit and WebCrypto globals.
 
 The path is taken from the URL (like `DELETE /vfs/{*path}`); the run arguments are the JSON body.
 Path traversal (`..`), null bytes, and backslashes are rejected with HTTP 400, as is a path that does
@@ -52,7 +59,17 @@ Applet executed successfully
 ```json
 {
   "ok": true,
-  "result": null,
+  "result": "id;name\n1;Kaffee",
+  "columns": [
+    {
+      "name": "…",
+      "type": "string"
+    }
+  ],
+  "rows": 1,
+  "warnings": [
+    "…"
+  ],
   "stdout": "…",
   "consoleLines": 1,
   "durationMs": 1,

src/api/index.js

@@ -13,6 +13,7 @@ import { ensureConnection } from '../db/store.js';
 import { closeAll as closeAllSse } from './sse.js';
 import { closeAllManagers } from '../services/conversationManager.js';
 import { shutdownImageCropWorkers } from '../services/imageCrop.js';
+import { shutdownJavascriptSandboxWorkers } from '../services/javascriptSandbox.js';
 import { getOrCreateCert } from '../util/cert.js';
 import { createLogger } from '../util/logger.js';
 import v1Router from '../v1/index.js';
@@ -242,6 +243,8 @@ export async function stopApi() {
     // Pooled image-crop workers are live threads and must be terminated too, or the
     // process stays alive after the last request has been served.
     await shutdownImageCropWorkers();
+    // Same for the pooled sandbox threads that run `javascript_execute` / applets.
+    await shutdownJavascriptSandboxWorkers();
     const closers = [];
     if (server) {
         const s = server;

src/api/routes/vfsExec.js

@@ -72,10 +72,17 @@ export function register(app, basePath = '') {
      *
      *       The applet file must begin with two metadata lines:
      *       `// @applet-input-schema {JSON Schema}` followed by
-     *       `// @applet-output-schema {JSON Schema}`. The file exports a function that receives the posted `input`
-     *       as `applet_input`, and execution runs in the same isolated worker sandbox as the `javascript_execute`
-     *       tool — including authenticated `fetch()` against this API, `fs`/`vfs`, `sharp`, ExcelJS, PDFKit and
-     *       WebCrypto globals.
+     *       `// @applet-output-schema {name:type;name:type}`. The input schema describes the GUI form posted as
+     *       `input`. The output line declares the RESULT COLUMNS as typed CSV — `name:type` pairs separated by `;`
+     *       (e.g. `id:integer;name:string;active:boolean`); allowed types are `string`, `integer`, `number`,
+     *       `boolean` and `date`. The applet exports a function that receives the posted `input` as `applet_input`
+     *       and returns a row object (or an array of row objects) keyed by those columns.
+     *
+     *       Applets return typed CSV, not JSON: `result` is a `;`-separated CSV string with a header row, and the
+     *       response also carries `columns` (name/type) and `rows` (data row count). Only declared columns are
+     *       emitted, in header order; missing values become empty cells. Execution runs in the same isolated worker
+     *       sandbox as the `javascript_execute` tool — including authenticated `fetch()` against this API,
+     *       `fs`/`vfs`, `sharp`, ExcelJS, PDFKit and WebCrypto globals.
      *
      *       The path is taken from the URL (like `DELETE /vfs/{*path}`); the run arguments are the JSON body.
      *       Path traversal (`..`), null bytes, and backslashes are rejected with HTTP 400, as is a path that does
@@ -115,13 +122,34 @@ export function register(app, basePath = '') {
      *           application/json:
      *             schema:
      *               type: object
-     *               required: [ok, result, stdout, consoleLines, durationMs]
+     *               required: [ok, result, columns, rows, stdout, consoleLines, durationMs]
      *               properties:
      *                 ok:
      *                   type: boolean
      *                 result:
-     *                   description: The value returned by the applet's exported function
-     *                   nullable: true
+     *                   type: string
+     *                   description: Typed CSV table (`;`-separated, header row first) built from the returned rows and the declared output columns
+     *                   example: "id;name\n1;Kaffee"
+     *                 columns:
+     *                   type: array
+     *                   description: Declared output columns, in header order
+     *                   items:
+     *                     type: object
+     *                     required: [name, type]
+     *                     properties:
+     *                       name:
+     *                         type: string
+     *                       type:
+     *                         type: string
+     *                         enum: [string, integer, number, boolean, date]
+     *                 rows:
+     *                   type: integer
+     *                   description: Number of data rows in `result` (excludes the header row)
+     *                 warnings:
+     *                   type: array
+     *                   description: Present when cells were dropped for not matching their declared type
+     *                   items:
+     *                     type: string
      *                 stdout:
      *                   type: string
      *                   description: Captured console output

src/services/javascriptSandbox.js

@@ -0,0 +1,406 @@
+import { Worker } from 'worker_threads';
+import { fileURLToPath } from 'url';
+import env from '../config/env.js';
+
+// The sandbox worker pays a large fixed startup cost: importing vm2, sharp, exceljs, pdfkit,
+// react-canvas-label-editor AND `vfs.js` (which pulls in libdashstore) costs ~700 ms in a fresh
+// thread, while the snippet itself runs in ~2 ms. ESM modules are never shared between worker
+// threads, so spawning one thread per applet run re-paid that cost on every request.
+//
+// This pool keeps threads alive and hands them one job at a time. Threads are keyed by VFS root
+// (`data/vfs/<companyId>`), so a reused thread always has the right `vfsDir` baked in and two
+// companies can never share a thread.
+const WORKER_PATH = fileURLToPath(new URL('../tools/javascript-worker.js', import.meta.url));
+const ROOT_DIR = fileURLToPath(new URL('../..', import.meta.url));
+const WORKER_BOOT_TIMEOUT_MS = 15000;
+
+// Two threads per company rides out the common "run it, then run it again" loop without queueing.
+const MAX_WORKERS_PER_COMPANY = 2;
+// ...but the process is shared by every company, so the total stays bounded. Each thread holds
+// sharp/libvips plus a NodeVM, so 5 is a deliberate memory ceiling rather than a core count.
+const MAX_WORKERS_TOTAL = 5;
+
+const DEFAULT_BUFFER_LIMIT = 32 * 1024 * 1024;
+
+/**
+ * @typedef {object} PoolEntry
+ * @property {Worker} worker
+ * @property {number} id        Monotonic thread id, used to tag job ids.
+ * @property {string} poolKey   VFS root this thread was spawned for.
+ * @property {boolean} busy
+ * @property {number} lastUsed  `Date.now()` of the last job handoff (eviction order).
+ */
+
+/** @type {Array<PoolEntry>} */
+const pool = [];
+/** @type {Array<{ resolve: Function, reject: Function, timer: NodeJS.Timeout, poolKey: string, job: object, timeoutMs: number }>} */
+const queue = [];
+let workerSeq = 0;
+let jobSeq = 0;
+let shuttingDown = false;
+/** Serializes pool growth so concurrent callers cannot overshoot either cap. */
+let growing = Promise.resolve();
+
+function countFor(poolKey) {
+    return pool.filter((entry) => entry.poolKey === poolKey).length;
+}
+
+function findIdle(poolKey) {
+    return pool.find((entry) => !entry.busy && entry.poolKey === poolKey);
+}
+
+function dropWorker(entry) {
+    const index = pool.indexOf(entry);
+    if (index !== -1) pool.splice(index, 1);
+}
+
+/**
+ * Reclaims an idle thread belonging to a DIFFERENT company so a queued job can be served.
+ *
+ * Without this the total cap would deadlock: with 5 threads spread over three companies, a
+ * fourth company's job could never be dispatched (no thread for it) and never spawn (cap hit).
+ * Only genuinely idle threads are evicted, and preferentially ones whose own company has
+ * nothing waiting.
+ *
+ * @param {string} poolKey
+ * @returns {boolean} whether a thread was reclaimed
+ */
+function evictIdleOtherCompany(poolKey) {
+    const candidates = pool.filter((entry) => !entry.busy && entry.poolKey !== poolKey);
+    if (candidates.length === 0) return false;
+
+    const idleOthers = new Set(
+        queue.filter((item) => item.poolKey !== poolKey).map((item) => item.poolKey)
+    );
+    candidates.sort((a, b) => {
+        const aWanted = idleOthers.has(a.poolKey) ? 1 : 0;
+        const bWanted = idleOthers.has(b.poolKey) ? 1 : 0;
+        return aWanted - bWanted || a.lastUsed - b.lastUsed;
+    });
+
+    const victim = candidates[0];
+    dropWorker(victim);
+    try { victim.worker.terminate(); } catch { /* already closed */ }
+    return true;
+}
+
+/**
+ * Spawns a thread for `vfsRoot` and resolves once it has reported `{ ready: true }`.
+ *
+ * The worker signals readiness only after its module body (and therefore every import) has
+ * finished, so a thread is never handed a job while it is still booting — which is what makes
+ * the reuse actually cheap.
+ *
+ * @param {string} vfsRoot  VFS root of the company this thread serves (the pool key).
+ * @param {number} googleAuthId
+ * @returns {Promise<PoolEntry>}
+ */
+function spawnWorker(vfsRoot, googleAuthId) {
+    const entry = { worker: null, id: ++workerSeq, poolKey: vfsRoot, busy: false, lastUsed: Date.now() };
+
+    return new Promise((resolve, reject) => {
+        const bootTimer = setTimeout(() => {
+            cleanup();
+            try { entry.worker?.terminate(); } catch { /* already closed */ }
+            reject(new Error(`Sandbox worker failed to start within ${WORKER_BOOT_TIMEOUT_MS} ms`));
+        }, WORKER_BOOT_TIMEOUT_MS);
+
+        function cleanup() {
+            clearTimeout(bootTimer);
+            entry.worker?.off('message', onBooted);
+            entry.worker?.off('error', onError);
+            entry.worker?.off('exit', onExit);
+        }
+
+        function onBooted(msg) {
+            if (!msg || msg.ready !== true) return;
+            cleanup();
+            resolve(entry);
+        }
+
+        function onError(err) {
+            cleanup();
+            reject(err instanceof Error ? err : new Error(err?.message || 'Sandbox worker failed to start'));
+        }
+
+        function onExit(code) {
+            cleanup();
+            reject(new Error(`Sandbox worker exited before becoming ready (code ${code})`));
+        }
+
+        try {
+            entry.worker = new Worker(WORKER_PATH, {
+                workerData: {
+                    root: ROOT_DIR,
+                    bufferLimit: DEFAULT_BUFFER_LIMIT,
+                    dashbackUrl: `http://127.0.0.1:${env.port}/api`,
+                    vfsDir: vfsRoot,
+                    googleAuthId,
+                },
+            });
+        } catch (err) {
+            cleanup();
+            reject(err);
+            return;
+        }
+
+        entry.worker.on('message', onBooted);
+        entry.worker.on('error', onError);
+        entry.worker.on('exit', onExit);
+    });
+}
+
+/**
+ * Returns an idle thread for `poolKey`, spawning (or evicting) to grow the pool when allowed.
+ * Resolves to `null` when every permitted thread is busy — the caller then queues.
+ *
+ * @param {string} poolKey
+ * @param {number} googleAuthId
+ * @returns {Promise<PoolEntry | null>}
+ */
+async function acquireWorker(poolKey, googleAuthId) {
+    const idle = findIdle(poolKey);
+    // Reserve SYNCHRONOUSLY, before any `await`. Otherwise two concurrent callers both pass
+    // this check while the thread is still unmarked, and both post to the same worker.
+    if (idle) {
+        idle.busy = true;
+        idle.lastUsed = Date.now();
+        return idle;
+    }
+
+    if (countFor(poolKey) < MAX_WORKERS_PER_COMPANY) {
+        growing = growing.then(async () => {
+            // Re-check inside the serialized block: another caller may have grown the pool.
+            if (countFor(poolKey) >= MAX_WORKERS_PER_COMPANY) return;
+            if (pool.length >= MAX_WORKERS_TOTAL && !evictIdleOtherCompany(poolKey)) return;
+            try {
+                pool.push(await spawnWorker(poolKey, googleAuthId));
+            } catch (err) {
+                // Fail the oldest queued job for this company rather than leaving it waiting on
+                // a thread that will never arrive, which would deadlock the queue instead of
+                // surfacing the boot failure to the caller.
+                const index = queue.findIndex((item) => item.poolKey === poolKey);
+                if (index === -1) throw err;
+                const waiting = queue.splice(index, 1)[0];
+                clearTimeout(waiting.timer);
+                waiting.reject(err);
+            }
+        });
+        try {
+            await growing;
+        } catch {
+            // Already reported to the queued job; continue so this caller still queues.
+        }
+        // Reserve the freshly booted thread atomically; a concurrent waiter that wakes after us
+        // finds none and queues instead.
+        const after = findIdle(poolKey);
+        if (after) {
+            after.busy = true;
+            after.lastUsed = Date.now();
+            return after;
+        }
+    }
+
+    return null;
+}
+
+/**
+ * Hands one job to one thread and resolves with the worker's report.
+ *
+ * Always RESOLVES with a report-shaped object — it never rejects. The tool layer distinguishes
+ * outcomes by shape (`timedOut`, `error`, or a `result` key), matching what the old one-shot
+ * worker returned, so timeout/error mapping in the routes keeps working unchanged.
+ *
+ * @param {PoolEntry} entry
+ * @param {object} job        Forwarded to the worker verbatim.
+ * @param {number} timeoutMs
+ * @returns {Promise<object>}
+ */
+function runJobOnWorker(entry, job, timeoutMs) {
+    return new Promise((resolve) => {
+        const jobId = `${entry.id}:${++jobSeq}`;
+        let settled = false;
+
+        const timer = setTimeout(() => {
+            // Terminate first, then report. A snippet stuck in a native call (libvips, fetch)
+            // would otherwise keep burning the thread after the caller has moved on, and its
+            // eventual reply would arrive against an already-settled job.
+            try { entry.worker.terminate(); } catch { /* already closed */ }
+            dropWorker(entry);
+            finish({ result: null, stdout: '', consoleLineCount: 0, timedOut: true, timeoutMs });
+        }, timeoutMs);
+
+        function cleanup() {
+            clearTimeout(timer);
+            entry.worker.off('message', onMessage);
+            entry.worker.off('error', onError);
+            entry.worker.off('exit', onExit);
+        }
+
+        function finish(payload) {
+            if (settled) return;
+            settled = true;
+            cleanup();
+            resolve(payload);
+        }
+
+        function onMessage(msg) {
+            // Ignore anything that is not THIS job's report. Under `node --watch` the dev
+            // server's module-loader hook posts `watch:import` notices on the same channel, so
+            // the first message is not necessarily our reply; job ids are matched, not order.
+            if (!msg || msg.__sandboxReport !== true || msg.id !== jobId) return;
+            finish(msg);
+        }
+
+        function onError(err) {
+            dropWorker(entry);
+            finish({
+                result: null,
+                stdout: '',
+                consoleLineCount: 0,
+                error: (err && err.message) ? err.message : `Sandbox worker failed: ${err?.stack || err?.name || 'unknown error'}`,
+                errorName: (err && err.name) || 'Error',
+                stack: err && typeof err.stack === 'string' ? err.stack : undefined,
+            });
+        }
+
+        function onExit(code) {
+            dropWorker(entry);
+            // Reaching here means the thread died WITHOUT reporting — a hard failure, never a
+            // silent empty success.
+            console.error(`[sandbox] worker exited without reporting (code ${code})`);
+            finish({
+                result: null,
+                stdout: '',
+                consoleLineCount: 0,
+                error: `Sandbox worker exited unexpectedly without reporting a result (code ${code}).`,
+                errorName: 'WorkerExit',
+            });
+        }
+
+        entry.worker.on('message', onMessage);
+        entry.worker.on('error', onError);
+        entry.worker.on('exit', onExit);
+
+        try {
+            entry.worker.postMessage({ ...job, id: jobId });
+        } catch (err) {
+            finish({
+                result: null,
+                stdout: '',
+                consoleLineCount: 0,
+                error: (err && err.message) || 'Failed to post job to sandbox worker',
+                errorName: 'PostMessageError',
+            });
+        }
+    });
+}
+
+/**
+ * Starts as many queued jobs as there are idle threads for their company.
+ */
+function drainQueue() {
+    for (;;) {
+        const index = queue.findIndex((item) => findIdle(item.poolKey));
+        if (index === -1) return;
+
+        const item = queue.splice(index, 1)[0];
+        clearTimeout(item.timer);
+        const entry = findIdle(item.poolKey);
+        entry.busy = true;
+        entry.lastUsed = Date.now();
+
+        runJobOnWorker(entry, item.job, item.timeoutMs)
+            .then(item.resolve, item.reject)
+            .finally(() => {
+                entry.busy = false;
+                drainQueue();
+            });
+    }
+}
+
+/**
+ * Runs one sandbox job on a pooled thread, spawning a thread if the caps allow and otherwise
+ * queueing until one frees up.
+ *
+ * @param {object} options
+ * @param {string} options.poolKey      VFS root; identifies the company (and the thread).
+ * @param {number} options.googleAuthId
+ * @param {string} options.code         Source to run.
+ * @param {number} options.timeoutMs
+ * @param {string} options.dashbackToken Per-run JWT for the sandbox's `fetch()`.
+ * @param {object} [options.appletInput]
+ * @param {string} [options.appletFile]
+ * @returns {Promise<object>} Worker report (`result` / `timedOut` / `error` shape).
+ */
+export async function runSandboxJob(options) {
+    if (shuttingDown) {
+        throw new Error('Sandbox worker pool is shutting down');
+    }
+
+    const { poolKey, googleAuthId, code, timeoutMs, dashbackToken, appletInput, appletFile } = options;
+    const job = { code, timeoutMs, dashbackToken, appletInput, appletFile, poolKey, googleAuthId };
+
+    const entry = await acquireWorker(poolKey, googleAuthId);
+    if (entry) {
+        try {
+            return await runJobOnWorker(entry, job, timeoutMs);
+        } finally {
+            entry.busy = false;
+            drainQueue();
+        }
+    }
+
+    return new Promise((resolve, reject) => {
+        // The queue wait is bounded by the same timeout budget as execution, so a caller cannot
+        // wait forever behind other companies' jobs.
+        const timer = setTimeout(() => {
+            const index = queue.findIndex((item) => item.timer === timer);
+            if (index !== -1) queue.splice(index, 1);
+            resolve({
+                result: null,
+                stdout: '',
+                consoleLineCount: 0,
+                error: `Sandbox queue timed out after ${timeoutMs} ms (all workers busy).`,
+                errorName: 'SandboxQueueTimeout',
+            });
+        }, timeoutMs);
+
+        queue.push({ resolve, reject, timer, poolKey, job, timeoutMs });
+    });
+}
+
+/**
+ * Terminates every pooled thread and fails anything still queued.
+ *
+ * Mirrors `shutdownImageCropWorkers`: live worker threads keep the process alive after the last
+ * request, so `node --watch` hangs on "Waiting for graceful termination..." without this.
+ *
+ * @returns {Promise<void>}
+ */
+export async function shutdownJavascriptSandboxWorkers() {
+    shuttingDown = true;
+
+    while (queue.length > 0) {
+        const pending = queue.shift();
+        clearTimeout(pending.timer);
+        pending.resolve({
+            result: null,
+            stdout: '',
+            consoleLineCount: 0,
+            error: 'Sandbox worker pool is shutting down',
+            errorName: 'SandboxShutdown',
+        });
+    }
+
+    const entries = pool.splice(0, pool.length);
+    await Promise.all(
+        entries.map((entry) =>
+            Promise.resolve()
+                .then(() => entry.worker.terminate())
+                .catch(() => { /* already closed */ })
+        )
+    );
+
+    shuttingDown = false;
+}

src/tools/javascript-worker.js

@@ -10,18 +10,15 @@ import ExcelJS from 'exceljs';
 import PDFDocument from 'pdfkit';
 import { createVfs } from './vfs.js';
 
+// Static, per-THREAD configuration. A pooled thread serves many jobs, so per-job values
+// (`code`, `appletInput`, `appletFile`, the request-scoped token and timeout) arrive as
+// `runJob` messages instead — see the job loop at the bottom of this file.
 const {
-    code,
     root,
-    vmTimeout,
     bufferLimit,
-    network,
     dashbackUrl,
-    dashbackToken,
     vfsDir,
     googleAuthId,
-    appletInput,
-    appletFile,
 } = workerData;
 
 function resolveDashbackUrl(inputUrl, baseApiUrl) {
@@ -425,7 +422,6 @@ function bridgePDFKit(vfs) {
 }
 
 const NETWORK_GLOBALS = {
- fetch: createSandboxFetch(dashbackUrl, dashbackToken),
     // WebCrypto globals (bridged across the vm2 realm boundary — see bridgeCrypto above).
     // Node's `crypto` MODULE is deliberately not exposed.
     ...(bridgedCrypto ? { crypto: bridgedCrypto } : {}),
@@ -448,46 +444,71 @@ const NETWORK_GLOBALS = {
     clearTimeout,
 };
 
-const lines = [];
-const push = (prefix) => (...args) => {
-    let text;
-    try {
-        text = args
-            .map((a) => {
-                if (typeof a === 'string') return a;
-                if (Buffer.isBuffer(a) || ArrayBuffer.isView(a) || (a && a.constructor && a.constructor.name === 'Buffer')) {
-                    return `<Buffer ${(a.byteLength ?? a.length ?? 0)} bytes>`;
-                }
-                try {
-                    return JSON.stringify(a, (k, v) => {
-                        if (v && typeof v === 'object') {
-                            if (v.type === 'Buffer' && Array.isArray(v.data)) {
-                                return `<Buffer ${v.data.length} bytes>`;
+/**
+ * Builds the sandbox `fetch` for ONE job.
+ *
+ * `fetch` signs its `Authorization` header with the JWT minted for that job's `googleAuthId`,
+ * so it must not live in a module-level object shared across every company a pooled thread
+ * happens to serve.
+ *
+ * @param {string} dashbackToken
+ */
+function createRunGlobals(dashbackToken) {
+    return {
+        fetch: createSandboxFetch(dashbackUrl, dashbackToken),
+        ...NETWORK_GLOBALS,
+    };
+}
+
+/**
+ * Builds a console that appends to the given per-job line buffer.
+ *
+ * A pooled thread runs many applets, so each job needs its OWN sink — otherwise job N's stdout
+ * would include job N-1's output.
+ *
+ * @param {Array<string>} lines
+ */
+function createSandboxConsole(lines) {
+    const push = (prefix) => (...args) => {
+        let text;
+        try {
+            text = args
+                .map((a) => {
+                    if (typeof a === 'string') return a;
+                    if (Buffer.isBuffer(a) || ArrayBuffer.isView(a) || (a && a.constructor && a.constructor.name === 'Buffer')) {
+                        return `<Buffer ${(a.byteLength ?? a.length ?? 0)} bytes>`;
+                    }
+                    try {
+                        return JSON.stringify(a, (k, v) => {
+                            if (v && typeof v === 'object') {
+                                if (v.type === 'Buffer' && Array.isArray(v.data)) {
+                                    return `<Buffer ${v.data.length} bytes>`;
+                                }
+                                if (Buffer.isBuffer(v) || ArrayBuffer.isView(v) || (v.constructor && v.constructor.name === 'Buffer')) {
+                                    return `<Buffer ${(v.byteLength ?? v.length ?? 0)} bytes>`;
+                                }
                             }
-                            if (Buffer.isBuffer(v) || ArrayBuffer.isView(v) || (v.constructor && v.constructor.name === 'Buffer')) {
-                                return `<Buffer ${(v.byteLength ?? v.length ?? 0)} bytes>`;
-                            }
-                        }
-                        return v;
-                    });
-                } catch {
-                    return String(a);
-                }
-            })
-            .join(' ');
-    } catch {
-        text = String(args);
-    }
-    lines.push(prefix + text);
-};
-const sandboxConsole = {
-    log: push(''),
-    info: push(''),
-    debug: push(''),
-    warn: push('warn: '),
-    error: push('error: '),
-    trace: push('trace: '),
-};
+                            return v;
+                        });
+                    } catch {
+                        return String(a);
+                    }
+                })
+                .join(' ');
+        } catch {
+            text = String(args);
+        }
+        lines.push(prefix + text);
+    };
+    return {
+        log: push(''),
+        info: push(''),
+        debug: push(''),
+        warn: push('warn: '),
+        error: push('error: '),
+        trace: push('trace: '),
+    };
+}
 
 const MAX_ITEMS = 200;
 
@@ -527,37 +548,53 @@ function sanitize(value, depth = 0) {
     return { type: t };
 }
 
-// Every genuine sandbox report is tagged with `__sandboxReport: true`.
-//
-// This is REQUIRED, not cosmetic: when the server runs under `node --watch` (see the `dev`
-// script), Node installs a module-loader hook that posts `watch:import` notices over the SAME
-// parentPort channel the worker reports on. Without this tag the parent cannot tell a real
-// report apart from loader chatter and will resolve on the wrong message.
-function report(payload) {
-    const message = { __sandboxReport: true, ...payload };
+/**
+ * Posts a job report back to the pool.
+ *
+ * Every report is tagged with the job id it answers AND `__sandboxReport: true`.
+ *
+ * The tag is REQUIRED, not cosmetic: when the server runs under `node --watch` (see the `dev`
+ * script), Node installs a module-loader hook that posts `watch:import` notices over the SAME
+ * parentPort channel the worker reports on. The pool matches the `id` to route a reply to the
+ * right job; without the tag it cannot tell a real report apart from loader chatter.
+ *
+ * @param {string} id
+ * @param {object} payload
+ */
+function report(id, payload) {
     try {
-        parentPort.postMessage(message);
+        parentPort.postMessage({ __sandboxReport: true, id, ...payload });
     } catch {
         try {
-            parentPort.postMessage({
-                __sandboxReport: true,
-                result: null,
-                error: 'Sandbox produced a result that could not be serialized.',
-                errorName: 'SerializationError',
-                stdout: lines.join('\n'),
-                consoleLineCount: lines.length,
-            });
+            parentPort.postMessage({ __sandboxReport: true, id, result: null, error: 'Sandbox produced a result that could not be serialized.', errorName: 'SerializationError' });
         } catch { /* thread exiting */ }
     }
 }
 
-void (async () => {
-try {
+/**
+ * Runs ONE job posted by the pool. Never throws: every outcome is reported via {@link report}.
+ *
+ * @param {object} job
+ * @param {string} job.id                  Opaque job id; echoed back on the report.
+ * @param {string} job.code                Source to run.
+ * @param {string} job.dashbackToken       Per-job JWT used to sign sandbox `fetch()` calls.
+ * @param {object} [job.appletInput]       Value passed as `applet_input` when `appletFile` is set.
+ * @param {string} [job.appletFile]        VFS path of the applet, which switches on the applet protocol.
+ */
+async function runJob(job) {
+    const code = job.code;
+    const appletInput = job.appletInput;
+    const appletFile = job.appletFile;
+
     const vfs = createVfs(vfsDir, { googleAuthId });
 
     const bridgedExcel = bridgeExcelJS(vfs);
     const bridgedPDF = bridgePDFKit(vfs);
 
+    // One console sink per job so pooled runs cannot see each other's stdout.
+    const lines = [];
+    const sandboxConsole = createSandboxConsole(lines);
+
     const vm = new NodeVM({
         console: 'off',
         sandbox: {
@@ -572,7 +609,7 @@ try {
             pdfkit: bridgedPDF,
             validateLabelObjects: (objects) => validateObjects(JSON.parse(JSON.stringify(objects))),
             validateLabelObject: (object) => validateObject(JSON.parse(JSON.stringify(object))),
-            ...NETWORK_GLOBALS,
+            ...createRunGlobals(job.dashbackToken),
         },
         require: {
             root,
@@ -581,7 +618,7 @@ try {
         },
         nesting: false,
         bufferAllocLimit: bufferLimit,
-        timeout: vmTimeout,
+        timeout: job.timeoutMs,
     });
 
     const started = Date.now();
@@ -602,52 +639,67 @@ try {
             value = value(appletInput);
         }
         if (value && typeof value.then === 'function') {
-            const settleTimeout = Math.max(1000, vmTimeout - 500);
+            const settleTimeout = Math.max(1000, job.timeoutMs - 500);
             value = await Promise.race([
-    value,
-          new Promise((_, reject) =>
-           setTimeout(() => reject(new Error('Async snippet did not settle before the timeout.')), settleTimeout)
-        ),
+                value,
+                new Promise((_, reject) =>
+                    setTimeout(() => reject(new Error('Async snippet did not settle before the timeout.')), settleTimeout)
+                ),
             ]);
         }
     } catch (err) {
         const rawMsg = (err && err.message) || String(err);
         failed = {
-          error: rawMsg,
+            error: rawMsg,
             errorName: (err && err.name) || 'Error',
             cause: err && err.cause ? ((err.cause && err.cause.message) || String(err.cause)) : undefined,
-  stack: err && typeof err.stack === 'string' ? err.stack : undefined,
+            stack: err && typeof err.stack === 'string' ? err.stack : undefined,
         };
         // Snippets run in a CommonJS wrapper, so bare top-level `await` is a syntax error.
-    // That is the single most common mistake, so say exactly how to fix it.
+        // That is the single most common mistake, so say exactly how to fix it.
         if (err instanceof SyntaxError && /await is only valid|Unexpected reserved word/i.test(rawMsg)) {
-   failed.error =
-         'Top-level `await` is not allowed: snippets run in a CommonJS (non-ESM) wrapper. ' +
-            'Wrap async code in an async IIFE and assign the promise to module.exports:\n' +
-          '  module.exports = (async () => { const res = await fetch("/company"); return res.json(); })();';
-}
+            failed.error =
+                'Top-level `await` is not allowed: snippets run in a CommonJS (non-ESM) wrapper. ' +
+                'Wrap async code in an async IIFE and assign the promise to module.exports:\n' +
+                '  module.exports = (async () => { const res = await fetch("/company"); return res.json(); })();';
+        }
     }
 
     if (failed) {
         console.error('[javascript-worker] snippet threw:', failed.error, '\n', failed.stack || '(no stack)');
-        report({ result: null, ...done(), ...failed });
+        report(job.id, { result: null, ...done(), ...failed });
     } else {
         // `result` MUST always be present: if the key were absent, the parent's
         // JSON.stringify() drops it and the tool response degenerates to a bare
         // echo of the submitted source with no sign of execution.
-        report({ result: sanitize(value), ...done() });
+        report(job.id, { result: sanitize(value), ...done() });
     }
-} catch (err) {
-    // Setup-level failure (bad VFS dir, thrown import, etc.) — log it here too, because the
-    // parent only sees a message and the worker's stderr is otherwise swallowed.
-    console.error('[javascript-worker] fatal setup error:', (err && err.message) || String(err), '\n', (err && err.stack) || '(no stack)');
-    report({
-        result: null,
-        stdout: lines.join('\n'),
-        consoleLineCount: lines.length,
-        error: (err && err.message) || String(err),
-        errorName: (err && err.name) || 'Error',
-        stack: err && typeof err.stack === 'string' ? err.stack : undefined,
-    });
 }
-})();
+
+// Pooled job loop. Imports (sharp, exceljs, pdfkit, libdashstore, …) are paid ONCE for the
+// lifetime of the thread; each subsequent job only builds a fresh NodeVM and runs the snippet,
+// which is the ~2 ms part. Jobs are serialized (one `await` per message) so a pooled thread
+// never interleaves two applets against the same VFS.
+parentPort.on('message', (job) => {
+    void (async () => {
+        try {
+            await runJob(job);
+        } catch (err) {
+            // Setup-level failure (bad VFS dir, thrown bridge, etc.) — log it here too, because
+            // the pool only sees a message and this thread's stderr is otherwise swallowed.
+            console.error('[javascript-worker] fatal setup error:', (err && err.message) || String(err), '\n', (err && err.stack) || '(no stack)');
+            report(job?.id, {
+                result: null,
+                stdout: '',
+                consoleLineCount: 0,
+                error: (err && err.message) || String(err),
+                errorName: (err && err.name) || 'Error',
+                stack: err && typeof err.stack === 'string' ? err.stack : undefined,
+            });
+        }
+    })();
+});
+
+// Ready handshake. All imports above have resolved by the time this module body executes, so
+// signalling now tells the pool it can hand this thread a job without racing the import phase.
+parentPort.postMessage({ ready: true });

src/tools/javascript.js

@@ -1,109 +1,198 @@
-import { Worker } from 'worker_threads';
-import { fileURLToPath } from 'url';
 import fs from 'fs';
 import path from 'path';
 import jwt from 'jsonwebtoken';
 import { defineTool, ToolError } from 'libllmorbiter';
 import env from '../config/env.js';
 import { createVfs, prepareVfs, syncVfsToDb } from './vfs.js';
-
-const __dirname = path.dirname(fileURLToPath(import.meta.url));
-const ROOT_DIR = path.resolve(__dirname, '../..');
-const WORKER_PATH = fileURLToPath(new URL('./javascript-worker.js', import.meta.url));
+import { runSandboxJob } from '../services/javascriptSandbox.js';
 
 const DEFAULT_TIMEOUT_MS = 20_000;
 const MAX_TIMEOUT_MS = 60_000;
 const DEFAULT_MAX_OUTPUT = 20_000;
-const DEFAULT_BUFFER_LIMIT = 32 * 1024 * 1024;
 
-// Keys already logged as benign non-sandbox worker chatter. Under `node --watch` the loader
-// emits `watch:import` / `watch:require` notices on the worker's parentPort for EVERY import,
-// so warning per message floods the log. We warn once per distinct key instead.
-const WATCH_NOISE_WARNED = new Set();
+// Column types an applet may declare in its `@applet-output-schema` header. Kept deliberately
+// small: each one maps to a JS-coercion rule the applet author can reason about, and the
+// frontend can render without guessing.
+const APPLET_COLUMN_TYPES = new Set(['string', 'integer', 'number', 'boolean', 'date']);
 
-function runInWorker({ code, timeoutMs, vfsRoot, googleAuthId, appletInput, appletFile }) {
-    return new Promise((resolve) => {
-        let settled = false;
-        const token = jwt.sign({ id: googleAuthId }, env.jwtSecret, { expiresIn: '5m' });
+// Semicolon-separated columns, matching the spreadsheet exports in `src/util/*Csv.js`.
+const APPLET_CSV_SEPARATOR = ';';
 
-        const worker = new Worker(WORKER_PATH, {
-            workerData: {
-                code,
-                root: ROOT_DIR,
-                vmTimeout: timeoutMs,
-                bufferLimit: DEFAULT_BUFFER_LIMIT,
-                dashbackUrl: `http://127.0.0.1:${env.port}/api`,
-                dashbackToken: token,
-                vfsDir: vfsRoot,
-                googleAuthId,
-                appletInput,
-                appletFile,
-            },
-        });
+/**
+ * Parse the applet output header into typed CSV columns.
+ *
+ * The header carries the COLUMN NAMES AND TYPES, e.g. `id:integer;name:string;active:boolean`.
+ * A bare `name` (no `:type`) is accepted and defaults to `string`. Types are limited to
+ * {@link APPLET_COLUMN_TYPES} so a typo surfaces here instead of at render time.
+ *
+ * @param {string} header raw text after the `// @applet-output-schema ` marker
+ * @returns {Array<{ name: string, type: string }>}
+ */
+function parseTypedCsvColumns(header) {
+    const text = String(header || '').trim();
+    if (!text) {
+        throw new ToolError(
+            'Applet output schema must declare typed CSV columns, e.g. ' +
+            '`@applet-output-schema id:integer;name:string`.'
+        );
+    }
 
-        const finish = (payload) => {
-            if (settled) return;
-            settled = true;
-            clearTimeout(timer);
-            try { worker.terminate(); } catch { /* already closed */ }
-            resolve(payload);
-        };
+    const columns = [];
+    const seen = new Set();
+    for (const raw of text.split(APPLET_CSV_SEPARATOR)) {
+        const field = raw.trim();
+        if (!field) continue;
 
-        const timer = setTimeout(() => {
-            console.error(`[javascript_execute] sandbox worker timed out after ${timeoutMs} ms`);
-            finish({ result: null, stdout: '', consoleLineCount: 0, timedOut: true, timeoutMs });
-        }, timeoutMs);
+        const sep = field.lastIndexOf(':');
+        const name = (sep === -1 ? field : field.slice(0, sep)).trim();
+        const type = (sep === -1 ? 'string' : field.slice(sep + 1).trim().toLowerCase());
 
-        worker.on('message', (msg) => {
-            // Ignore anything that is not a genuine sandbox report. Running the server under
-            // `node --watch` (the `dev` script) installs a module-loader hook that posts
-            // `watch:import` notices on this same channel; treating the first message as the
-            // result made the sandbox appear to run for 0ms and return nothing.
-            if (!msg || msg.__sandboxReport !== true) {
-                // Those loader notices fire many times per run, so warn ONCE per key rather
-                // than on every message — expected, benign noise while running under --watch.
-                for (const key of Object.keys(msg || {})) {
-                    if (!WATCH_NOISE_WARNED.has(key)) {
-                        WATCH_NOISE_WARNED.add(key);
-                        console.warn(
-                            `[javascript_execute] ignoring non-sandbox worker message "${key}" ` +
-                            '(expected under `node --watch`; logged once per key).'
-                        );
-                    }
+        if (!name) {
+            throw new ToolError(`Applet output column name is empty in "${field}".`);
+        }
+        if (!APPLET_COLUMN_TYPES.has(type)) {
+            throw new ToolError(
+                `Applet output column "${name}" has unknown type "${type}". ` +
+                `Use one of: ${[...APPLET_COLUMN_TYPES].join(', ')}.`
+            );
+        }
+        if (seen.has(name)) {
+            throw new ToolError(`Applet output column "${name}" is declared twice.`);
+        }
+        seen.add(name);
+        columns.push({ name, type });
+    }
+
+    if (columns.length === 0) {
+        throw new ToolError('Applet output schema must declare at least one column.');
+    }
+    return columns;
+}
+
+/**
+ * Quote one CSV field (RFC 4180): wrap when it contains the separator, a quote, or a newline.
+ * @param {unknown} value
+ * @returns {string}
+ */
+function encodeCsvField(value) {
+    const text = value == null ? '' : String(value);
+    if (text.includes(APPLET_CSV_SEPARATOR) || text.includes('"') || /[\r\n]/.test(text)) {
+        return `"${text.replace(/"/g, '""')}"`;
+    }
+    return text;
+}
+
+/**
+ * Coerce a returned cell to its declared type and report what happened.
+ *
+ * Returns `null` when the value cannot be coerced (`undefined`, `null`, `NaN`, unparseable
+ * date). The caller turns that into an empty CSV cell, so a missing value never aborts the run.
+ *
+ * @param {unknown} value
+ * @param {string} type
+ * @returns {{ ok: true, value: string | number | boolean } | { ok: false }}
+ */
+function coerceAppletCell(value, type) {
+    if (value === undefined || value === null) return { ok: false };
+
+    switch (type) {
+        case 'string':
+            return { ok: true, value: typeof value === 'object' ? JSON.stringify(value) : String(value) };
+        case 'boolean':
+            if (typeof value === 'boolean') return { ok: true, value };
+            if (value === 1 || value === 0) return { ok: true, value: value === 1 };
+            if (typeof value === 'string' && /^(true|false)$/i.test(value.trim())) {
+                return { ok: true, value: value.trim().toLowerCase() === 'true' };
+            }
+            return { ok: false };
+        case 'integer':
+        case 'number': {
+            const num = typeof value === 'number' ? value : Number(String(value).trim());
+            if (!Number.isFinite(num)) return { ok: false };
+            return { ok: true, value: type === 'integer' ? Math.trunc(num) : num };
+        }
+        case 'date': {
+            const date = value instanceof Date ? value : new Date(value);
+            if (Number.isNaN(date.getTime())) return { ok: false };
+            return { ok: true, value: date.toISOString() };
+        }
+        default:
+            return { ok: false };
+    }
+}
+
+/**
+ * Serialize an applet's return value into typed CSV keyed by its declared columns.
+ *
+ * The applet returns rows as objects (or arrays). Only declared columns are emitted, in header
+ * order; unknown keys are dropped and missing ones become empty cells. Scalars and key
+ * information that belong to the row itself are surfaced as `warnings` rather than failing.
+ *
+ * @param {unknown} result    value returned by the applet's exported function
+ * @param {Array<{ name: string, type: string }>} columns
+ * @returns {{ csv: string, rows: number, columns: Array<{ name: string, type: string }>, warnings: string[] }}
+ */
+function toTypedCsv(result, columns) {
+    const warnings = [];
+
+    let rows;
+    if (result === undefined || result === null) {
+        rows = [];
+    } else if (Array.isArray(result)) {
+        rows = result;
+    } else if (typeof result === 'object') {
+        // A single object is one row — the common "return the totals" case.
+        rows = [result];
+    } else {
+        rows = [result];
+        warnings.push(
+            `Applet returned a ${typeof result}, which has no columns to map onto; ` +
+            'the value was placed in the first column.'
+        );
+    }
+
+    let coercions = 0;
+    const body = rows.map((row) => {
+        const isContainer = row && typeof row === 'object' && !Array.isArray(row);
+        return columns
+            .map((column, index) => {
+                const value = isContainer ? row[column.name] : index === 0 ? row : undefined;
+                const coerced = coerceAppletCell(value, column.type);
+                if (!coerced.ok) {
+                    if (value !== undefined && value !== null) coercions += 1;
+                    return '';
                 }
-                return;
-            }
-            finish(msg);
-        });
-        // A worker 'error' fires BEFORE any message when the thread fails to boot (e.g. an
-        // import throws at startup). ALWAYS send a truthy `error` plus the full stack so the
-        // parent can throw with something actionable; an empty `err.message` must never
-        // degrade into a silent, result-less success payload.
-        worker.on('error', (err) => finish({
-            result: null,
-            stdout: '',
-            consoleLineCount: 0,
-            error: (err && err.message)
-                ? err.message
-                : `Sandbox worker failed to start: ${err?.stack || err?.name || 'unknown error'}`,
-            errorName: (err && err.name) || 'Error',
-            stack: err && typeof err.stack === 'string' ? err.stack : undefined,
-        }));
-        worker.on('exit', (code) => {
-            // `finish` is idempotent via `settled`, so a message that already resolved the
-            // promise is never overwritten. Reaching here means the worker died WITHOUT
-            // reporting — that is a hard failure, so log it and always carry a truthy error.
-            if (!settled) {
-                console.error(`[javascript_execute] sandbox worker exited without reporting (code ${code})`);
-            }
-            finish({
-                result: null,
-                stdout: '',
-                consoleLineCount: 0,
-                error: `Sandbox worker exited unexpectedly without reporting a result (code ${code}).`,
-                errorName: 'WorkerExit',
-            });
-        });
+                return encodeCsvField(coerced.value);
+            })
+            .join(APPLET_CSV_SEPARATOR);
+    });
+
+    if (coercions > 0) {
+        warnings.push(`${coercions} cell(s) did not match their declared column type and were left empty.`);
+    }
+
+    const csv = [columns.map((c) => encodeCsvField(c.name)).join(APPLET_CSV_SEPARATOR), ...body].join('\n');
+    return { csv, rows: body.length, columns, warnings };
+}
+
+/**
+ * Runs one snippet/applet on the shared sandbox pool.
+ *
+ * Threads are keyed by VFS root so a reused thread keeps the right company's `vfsDir`, and the
+ * per-run JWT is minted here because it is scoped to THIS `googleAuthId`.
+ *
+ * @param {{ code: string, timeoutMs: number, vfsRoot: string, googleAuthId: number, appletInput?: object, appletFile?: string }} ctx
+ */
+function runInWorker({ code, timeoutMs, vfsRoot, googleAuthId, appletInput, appletFile }) {
+    const dashbackToken = jwt.sign({ id: googleAuthId }, env.jwtSecret, { expiresIn: '5m' });
+    return runSandboxJob({
+        poolKey: vfsRoot,
+        googleAuthId,
+        code,
+        timeoutMs,
+        dashbackToken,
+        appletInput,
+        appletFile,
     });
 }
 
@@ -145,27 +234,24 @@ function readApplet(vfsRoot, appletvfsfile) {
         throw new ToolError(
             'Applet metadata must be on the first two lines: ' +
             '`// @applet-input-schema {JSON Schema}` followed by ' +
-            '`// @applet-output-schema {JSON Schema}`.'
+            '`// @applet-output-schema name:type;name:type` (typed CSV columns).'
         );
     }
 
     let inputSchema;
-    let outputSchema;
     try {
         inputSchema = JSON.parse(inputHeader[1]);
-        outputSchema = JSON.parse(outputHeader[1]);
     } catch (err) {
-        throw new ToolError(`Applet metadata must contain valid JSON schemas: ${err.message}`);
+        throw new ToolError(`Applet input schema must be valid JSON: ${err.message}`);
     }
     if (!inputSchema || typeof inputSchema !== 'object' || Array.isArray(inputSchema) ||
         inputSchema.type !== 'object') {
         throw new ToolError('Applet input schema must be a JSON Schema with type "object".');
     }
-    if (!outputSchema || typeof outputSchema !== 'object' || Array.isArray(outputSchema)) {
-        throw new ToolError('Applet output schema must be a JSON Schema object.');
-    }
 
-    return source;
+    const outputColumns = parseTypedCsvColumns(outputHeader[1]);
+
+    return { source, outputColumns };
 }
 
 function formatSandboxError(code, report) {
@@ -188,7 +274,9 @@ export function createJavascriptExecuteTool({ googleAuthId }) {
         description:
             'Execute JS in an isolated worker sandbox using either inline `code` or a VFS applet. Provide exactly one of `code` and `appletvfsfile`. ' +
             'Applets are the preferred method when the first execution may throw: save a `.applet.js` file in the VFS so it can be inspected and further edited with `patch`, then call it by VFS path. ' +
-            'Applet files must start with `// @applet-input-schema {JSON Schema}` and `// @applet-output-schema {JSON Schema}` on their first two lines. The input schema describes the GUI form passed as `applet_input`; the output schema describes the exported function result. Export a function that receives `applet_input`. ' +
+            'Applet files must start with `// @applet-input-schema {JSON Schema}` on line 1 and `// @applet-output-schema <columns>` on line 2. ' +
+            'The input schema describes the GUI form passed as `applet_input`. The output line declares the RESULT COLUMNS as typed CSV: `name:type` pairs separated by `;` (e.g. `id:integer;name:string;active:boolean`); a bare `name` defaults to string, and the allowed types are string, integer, number, boolean and date. ' +
+            'Applets return typed CSV, NOT JSON: export a function that receives `applet_input` and returns a row object, or an array of row objects, whose keys are the declared columns (e.g. `return [{ id: 1, name: "Kaffee" }]`). Only declared columns are emitted, in header order; missing keys become empty cells. The tool result then carries `result` as a `;`-separated CSV string with a header row, plus `columns` (name/type) and `rows` (data row count). Returning a single object yields one data row. ' +
             'Inline code: assign `module.exports` to return value (sync value or Promise; wrap async in IIFE: `module.exports = (async () => { ... })()`). ' +
             'REST API: `await fetch("/path")` (authenticated). ' +
             'VFS: directly use global `fs.readFileSync`/`writeFileSync` for binary artifacts/buffers/images (`image/` is read-only; paths must be relative paths, root is not allowed). VFS can host a static website (HTML, CSS, JS, images, etc.). ' +
@@ -209,11 +297,11 @@ export function createJavascriptExecuteTool({ googleAuthId }) {
                 },
                 appletvfsfile: {
                     type: 'string',
-                    description: 'Optional VFS-relative path to a .applet.js file. Provide exactly one of this and code. The file must begin with the two applet JSON Schema metadata lines described in the tool description.',
+                    description: 'Optional VFS-relative path to a .applet.js file. Provide exactly one of this and code. The file must begin with the two applet metadata lines (`@applet-input-schema` JSON Schema, then `@applet-output-schema` typed CSV columns like `id:integer;name:string`).',
                 },
                 applet_input: {
                     type: 'object',
-                    description: 'Input values passed to the exported function when running appletvfsfile. Omit to pass an empty object.',
+                    description: 'Input values passed to the exported function when running appletvfsfile. Omit to pass an empty object. The applet returns typed CSV rows mapped onto its `@applet-output-schema` columns.',
                     additionalProperties: true,
                 },
                 timeout: {
@@ -257,7 +345,8 @@ export function createJavascriptExecuteTool({ googleAuthId }) {
 
             const vfsRoot = await prepareVfs({ googleAuthId });
             const isApplet = hasApplet;
-            const source = isApplet ? readApplet(vfsRoot, appletvfsfile) : code;
+            const applet = isApplet ? readApplet(vfsRoot, appletvfsfile) : null;
+            const source = isApplet ? applet.source : code;
             let report;
             try {
                 report = await runInWorker({
@@ -314,6 +403,15 @@ export function createJavascriptExecuteTool({ googleAuthId }) {
                 // Always present, even when empty, so callers can rely on the shape.
                 stdout,
             };
+            // Applets return typed CSV, not JSON: the declared columns turn the returned rows
+            // into a `;`-separated table. Inline code keeps returning its raw value.
+            if (isApplet) {
+                const table = toTypedCsv(report.result, applet.outputColumns);
+                result.result = table.csv;
+                result.rows = table.rows;
+                result.columns = table.columns;
+                if (table.warnings.length) result.warnings = table.warnings;
+            }
             if (truncated) {
                 result.truncated = true;
                 result.truncationNote = `Console output longer than ${maxOutput} chars was capped.`;