Sarathi

The teacher's silent co-pilot. An AI-powered desktop overlay that whispers strategy to BrightChamps teachers during live 1:1 classes — completely invisible to students on screen share.

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What it does

Teacher presses a hotkey during class. Sarathi silently screenshots whatever is on screen — slides, code editor, browser — sends it to Claude's vision model with the loaded lesson plan as context, and shows a floating panel with 3 smart suggestions. The teacher picks one, gets a concise answer, and moves on. The student never sees any of it.

Teacher's screen                    Student's screen (Zoom)
+---------------------------+       +---------------------------+
|                           |       |                           |
|   [code.org editor]       |       |   [code.org editor]       |
|                           |       |                           |
|            +----------+   |       |                           |
|            | Sarathi   |   |       |       (nothing here)      |
|            | 1. Fix... |   |       |                           |
|            | 2. Exp... |   |       |                           |
|            | 3. Poi... |   |       |                           |
|            +----------+   |       |                           |
+---------------------------+       +---------------------------+

Key features

• Vision-powered — sees the teacher's screen in real-time via Claude's vision model
• Lesson-grounded — every response anchored to the loaded lesson plan (no hallucination)
• Multi-turn memory — follow-up questions without re-triggering the hotkey
• Screen share safe — OS-level content protection (setContentProtection), not a CSS trick
• Visual pointer — ask "point to the error" and a purple cursor appears on the element
• 2-second response — from hotkey to options on screen

Run it

# 1. Clone and install
git clone https://github.com/loadingpeacefully/sarathi.git
cd sarathi
npm install

# 2. Add your API key
cp .env.example .env
# Edit .env and add your ANTHROPIC_API_KEY

# 3. Launch
npx electron .

Select a lesson from the menu bar icon, then press Cmd+Shift+Space (Mac) or Ctrl+Shift+Space (Windows) during class.

Architecture

sarathi/
├── src/
│   ├── main.js          ← Electron: tray menu, hotkey, screenshot, IPC
│   ├── sarathi.js       ← Claude vision API + lesson context + conversation memory
│   └── overlay.html     ← Floating panel UI + pointer canvas + state machine
├── lessons/
│   ├── lesson1.json     ← App Development (coding)
│   ├── lesson2.json     ← App Development (coding)
│   └── lesson3.json     ← Place Value of Digits (math)
├── assets/
│   └── iconTemplate.png ← Menu bar tray icon
└── docs/
    └── index.html       ← Landing page (GitHub Pages)

3 source files. 0 frameworks. 2 npm dependencies (electron + dotenv).

All Claude calls go through sarathi.js. The overlay is a single HTML file with inline CSS/JS and a state machine: hidden → loading → options → thinking → response → error. The panel follows the cursor, is draggable, and uses smart click-through so apps beneath remain interactive.

How it works

1. Hotkey → main.js captures screenshot via desktopCapturer (1920x1080)
2. Options → sarathi.js sends screenshot + lesson context to Claude, gets 3 suggestions
3. Response → teacher picks one or types a question, Claude responds grounded in the lesson
4. Pointer → if Claude identifies an element, [POINT:x,y] tag draws a purple cursor on the overlay canvas
5. Invisible → overlayWindow.setContentProtection(true) excludes the window from all screen capture APIs

Lessons

Lesson JSON files follow this schema:

{
  "lesson_title": "Place Value of Digits",
  "topics_covered": "Place value, comparing numbers",
  "objective": "Understand how digit value depends on position",
  "tool": "BrightChamps Math Platform",
  "duration_mins": 55,
  "concept_definitions": [{ "concept": "...", "definition": "..." }],
  "warmup_qa": [{ "q": "...", "a": "..." }],
  "checkpoint_qa": [{ "q": "...", "a": "...", "marks": 2 }],
  "common_errors": ["..."]
}

Add a new lesson: drop a .json file in lessons/ — it appears in the tray menu automatically.

Tech stack

Component	Choice	Why
Desktop app	Electron	Cross-platform, desktopCapturer built-in, setContentProtection for screen share exclusion
AI	Claude Sonnet (vision)	Fast enough for live class, vision-capable, follows system prompts precisely
API	Raw https module	No SDK dependency, keeps the app at 2 npm packages total
UI	Vanilla HTML/CSS/JS	No build step, no bundler, instant iteration

License

Internal prototype. Not for distribution.

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Named after Krishna's role as Arjuna's charioteer (sarathi) in the Mahabharata — the strategist who never entered the battlefield himself, but whispered the moves that changed everything.