---
name: notebooklm-api
description: Expert assistant for the notebooklm-api project — a Puppeteer-based REST/WebSocket server that automates Google NotebookLM. Use when working on browser automation, Puppeteer selectors, API routes, queue logic, or debugging DOM interactions with NotebookLM.
triggers:
  - "notebooklm"
  - "puppeteer"
  - "selector"
  - "notebook"
  - "add source"
  - "chat stream"
  - "browser automation"
---

# NotebookLM API — Project Skill

## What this project is

A Node.js server (`src/server.js`) that drives **Google NotebookLM** (`https://notebooklm.google.com`) through a real Chrome window via Puppeteer with the Stealth plugin. It exposes a REST + WebSocket API so external systems (n8n, Python scripts, ERP, chatbots) can interact with NotebookLM programmatically.

**Key constraint:** NotebookLM has no official API. Every operation — listing notebooks, adding sources, chatting — is done by simulating real user clicks and keystrokes in the browser. The Google Angular UI changes frequently, so DOM selectors may need updating after UI changes.

## Architecture

```
src/
  server.js      — Express app, middleware, debug routes, graceful shutdown
  browser.js     — BrowserManager singleton (puppeteer-extra + stealth)
  nlm.js         — All NotebookLM automation logic (the core)
  queue.js       — AsyncQueue: serialises ALL Puppeteer ops (no concurrency)
  selectors.js   — CSS selectors confirmed from real DOM inspection
  swagger.js     — Swagger/OpenAPI spec
  routes/
    auth.js      — GET /api/auth/status, POST /api/auth/login
    notebooks.js — CRUD for notebooks + sources
    chat-ws.js   — WebSocket streaming chat
```

## The queue — critical invariant

`src/queue.js` is a single-lane async queue. **Every route wraps its nlm call in `queue.add(...)`**. This prevents Puppeteer race conditions — only one browser action runs at a time. Never bypass the queue. If a new route is added, it MUST use the queue.

## Selectors — how to update them

All selectors live in `src/selectors.js`. They were confirmed against the Vietnamese-language NotebookLM UI. When Google updates the UI and a selector breaks:

1. Use the debug endpoints in `server.js` to inspect the live DOM:
   - `GET /debug/home` — lists all visible buttons on the home page (find create/delete buttons)
   - `GET /debug/notebook-menu/:id` — hovers a card, clicks the "..." menu, returns menu items
   - `GET /debug/chat/:id` — lists all textarea/input elements on a notebook page
   - `GET /debug/sources/:id` — inspects the source panel DOM
   - `GET /debug/source-items/:id` — full HTML of source items (buttons, icons, spans)
   - `GET /debug/add-source-dialog/:id` — clicks "Add source" and snapshots the dialog
   - `GET /debug/add-url-flow/:id` — step-by-step trace of the full add-URL flow
   - `GET /debug/page-state/:id` — full overlay/dialog state before+after click
   - `GET /debug/screenshot` — base64 PNG of current Chrome window

2. Key known selectors (confirmed 2026-06-16):
   - Create notebook button: `button[aria-label="Tạo sổ ghi chú mới"], button.create-new-button`
   - Card menu button: `button[aria-label="Trình đơn thao tác trong dự án"]`
   - Delete menu item: find by text `/Xo[áa]/i` inside `.mat-mdc-menu-panel button.mat-mdc-menu-item`
   - Add source button: `.add-source-button`
   - Source items: `div.single-source-container` (NOT `.source-item-menu-button-visible` which is a child)
   - Source title: `button.source-stretched-button[aria-label]` inside each container
   - Source type icon: `mat-icon.source-item-source-icon` text; or "url" if `img.favicon-icon` present
   - Chat textarea: `textarea.query-box-input` (NOT the source search textarea)
   - AI response cards: `mat-card.to-user-message-card-content`
   - User message cards: `mat-card.from-user-message-card-content`
   - Thinking animation: `div.thinking-message, thinking-animation`
   - Dialogs: `mat-dialog-container` (multiple can exist — emoji keyboard occupies one)

3. The UI language is **Vietnamese** — button labels like "Trang web", "Văn bản đã sao chép", "Chèn", "Tạo sổ ghi chú mới".

## Dialog handling — the tricky part

The Add Source dialog now has a **2-stage flow**:

**Stage 1 (initial):** Shows source-type buttons + a search textarea (`placeholder="Tìm nguồn mới trên web"`, class `query-box-textarea`). This textarea is always present and must be EXCLUDED from URL/text input detection.

**Stage 2 (after clicking type button):** Dialog transitions in-place to show:
- URL mode: a TEXTAREA with `aria-label="Nhập URL"` and `placeholder="Dán liên kết bất kỳ"`
- Text mode: a large textarea without the `query-box-textarea` class

**Submit button:** `"Chèn"` button with `type="button"` (NOT `type="submit"` — that's the back/close buttons).

Pattern in `nlm.addSourceUrl()` — wait for dialog to TRANSITION before finding URL input:
```javascript
// Click "Trang web" button
await page.evaluate(() => {
  const d = [...document.querySelectorAll('mat-dialog-container')].pop();
  const btn = [...d.querySelectorAll('button')].find(b => /Trang web/i.test(b.textContent));
  btn?.click();
});

// Wait for URL input to appear (not the search textarea)
await page.waitForFunction(() => {
  const d = [...document.querySelectorAll('mat-dialog-container')].pop();
  return [...d.querySelectorAll('input, textarea')].some(el =>
    el.offsetParent !== null &&
    (el.getAttribute('aria-label')?.toLowerCase().includes('url') ||
     /liên kết|link|paste|http/i.test(el.placeholder))
  );
}, { timeout: 10_000, polling: 200 });

// Click submit — use "Chèn" text, NOT type="submit"
await page.evaluate(() => {
  const d = [...document.querySelectorAll('mat-dialog-container')].pop();
  const btn = [...d.querySelectorAll('button')].find(b =>
    b.offsetParent !== null && !b.disabled && /Ch[eè]n/i.test(b.textContent)
  );
  btn?.click();
});
```

## Chat streaming (WebSocket)

`src/routes/chat-ws.js` handles `WS /api/notebooks/:id/chat/stream`.

The streaming works by **polling the DOM** every 300ms during the AI response, diffing against the last known text, and emitting `{ type: "chunk", data: "..." }` messages. This is not true server-sent streaming — it's DOM polling.

Message types the server emits:
- `{ type: "connected", notebookId }` — on WS open
- `{ type: "chunk", data: string }` — incremental text
- `{ type: "done", data: { answer } }` — response complete
- `{ type: "error", data: string }` — on failure

## waitForAiResponse — response completion detection

`nlm.waitForAiResponse(page, prevCount, timeout)` in `src/nlm.js` uses a 3-step approach:
1. Wait for `div.thinking-message` / `thinking-animation` to disappear
2. Wait for a new `mat-card.to-user-message-card-content` to appear (count > prevCount)
3. Wait for the text to be **stable for 1.5s** (no changes in 4 consecutive 400ms polls)

This handles streaming responses that may still be updating after the spinner disappears.

## Browser session persistence

Chrome profile is stored at `./chrome-profile/`. Google login cookies persist between server restarts. On startup, `browser.isAuthenticated()` navigates to `https://notebooklm.google.com` and checks if the URL stays there (not redirected to `accounts.google.com`).

**Important:** Always stop the server with `Ctrl+C` (SIGTERM/SIGINT) — the graceful shutdown handler calls `browser.close()` to flush Chrome's cookie store. Using `kill -9` may corrupt the session.

## File upload (`addSourceFile`) — xap uploader quirks

NotebookLM's "Tải tệp lên" button uses Google's internal **xap scotty uploader** (`[xapscottyuploadertrigger]` attribute). Key findings from 2026-06-16 debugging:

1. **Trigger button is in the INITIAL dialog** — drop zone + "Tải tệp lên" button appear as soon as the add-source dialog opens. No need to click a secondary button to reveal the drop zone.

2. **Must use trusted (CDP) click** — `trigger.click()` inside `page.evaluate()` generates `isTrusted: false`. The xap uploader silently ignores untrusted clicks. Use `page.mouse.click(x, y)` (Puppeteer's CDP method) to generate trusted clicks.

3. **Two upload paths** — depending on browser context, xap uploader may use either:
   - **Native file chooser** (`input[type=file]`) → caught by `page.waitForFileChooser()` + `fileChooser.accept([path])`
   - **`showOpenFilePicker()`** → override it BEFORE clicking: `window.showOpenFilePicker = async () => [{ getFile: () => file, ... }]`

4. **No "Chèn" button** — after file upload, dialog auto-closes. No confirmation click needed.

5. **Wait for network idle** after upload (the scotty upload finishes asynchronously).

```javascript
// Pattern (from nlm.addSourceFile):
const chooser = page.waitForFileChooser({ timeout: 8_000 }).catch(() => null);
await page.mouse.click(triggerX, triggerY);           // trusted click
const fc = await chooser;
if (fc) await fc.accept([absPath]);                   // native file chooser path
// else showOpenFilePicker override handles it
await page.waitForNetworkIdle({ timeout: 60_000 });   // wait for scotty upload
```

### Debugging "add source button not found" error

The add-source button (`button[aria-label="Thêm nguồn"]`) only exists on notebooks the USER OWNS. Public/shared notebooks (shown with "Công khai" badge) don't have this button. Always test with a user-owned notebook.

## Common tasks

### Adding a new API endpoint
1. Create or edit a route file in `src/routes/`
2. Add automation logic to `src/nlm.js`
3. Register the route in `src/server.js` with `app.use()`
4. Wrap the nlm call in `queue.add(() => nlm.myFn(), 'label')`
5. Add to the Swagger spec in `src/swagger.js`
6. Update `API.md`

### Fixing a broken selector
1. Start the server: `npm start`
2. Hit the relevant `/debug/*` endpoint to see the live DOM (`/debug/home`, `/debug/source-items/:id`, `/debug/add-url-flow/:id`, etc.)
3. Update `src/selectors.js` with the corrected selector
4. If logic (not just selector) is wrong (e.g. timing, wrong element), update `src/nlm.js`
5. Test via the actual API endpoint

### Debugging "nút xác nhận không tìm thấy" in add source flow
- The Add Source dialog has a 2-stage flow. If you get "nút xác nhận", it likely means:
  1. The URL was typed into the WRONG textarea (the search box `query-box-textarea`)
  2. The dialog never transitioned to stage 2, so "Chèn" button never appeared
- Use `GET /debug/add-url-flow/:id` to trace each step and see what happened
- Key filter: exclude `el.placeholder?.includes('Tìm nguồn')` and `el.className?.includes('query-box-textarea')`

### Debugging a "dialog not found" error
- Use `GET /debug/notebook-menu/:id` to see what menu appears after hover+click
- Use `GET /debug/add-source-dialog/:id` to see the full overlay HTML after clicking add source

### Understanding queue state
`GET /health` returns `{ queue: { busy: boolean, pending: number } }`. If `busy` is always true, a previous operation is stuck (possibly waiting for a DOM element that never appeared). Restart the server.

## Environment variables

| Variable | Default | Notes |
|---|---|---|
| `PORT` | `3456` | HTTP/WS port |
| `HEADLESS` | `false` | Set `true` for CI (may break Google login) |
| `CHROME_PATH` | auto-detect | Prefers system Chrome over bundled Chromium |
| `API_KEY` | _(empty)_ | If set, all requests need `x-api-key` header |

## Running locally

```bash
npm install    # first time only
npm start      # starts at http://localhost:3456
npm run dev    # same but with --watch (auto-restarts on file change)
```

Swagger UI: `http://localhost:3456/docs`

## Files NOT to modify carelessly

- `chrome-profile/` — Google session data. Do not delete. Do not gitignore the entire directory (the profile must persist).
- `src/queue.js` — Changing the queue to allow concurrency will cause race conditions in Puppeteer.
- `src/nlm.js:waitForAiResponse` — The stability detection logic is tuned for NotebookLM's streaming behaviour; don't simplify it.