# Terminal Emulator - Verifiable Prototype

## Checkpoint 1: 2025-12-08 - Test Harness

### Goal
Create a test harness that can verify terminal emulator output against expected screen state.

### Verification
```bash
npm run test:emulator
```

### Results
- Test runner reads `.cast` files (asciicast v2 format)
- Compares rendered output to `expected.txt` (80x24 grid)
- Naive renderer passes simple echo test

### Feedback
- Test format works: input.cast + expected.txt
- Naive renderer won't handle cursor movement, TUI apps
- Need real terminal emulator (avt WASM) for complex cases

### Next Steps
1. Add a test case that requires real terminal emulation (cursor movement)
2. Integrate avt WASM to replace naive renderer
3. Verify avt passes both simple and complex tests

---

## Checkpoint 2: 2025-12-09 - Terminal Emulator Integration

### Goal
Integrate terminal emulator to pass cursor movement test.

### Verification
```bash
npm run test:emulator
```

### Results
- Integrated `@xterm/headless` (from xterm.js project) instead of avt WASM
- Both tests pass: 01-echo and 02-cursor
- Added `shell_snapshot` tool returning rendered screen grid
- MCP server now properly emulates terminal state

### Feedback
- @xterm/headless works in Node.js (unlike regular xterm.js)
- Requires `allowProposedApi: true` for buffer access
- Write is async - need to await completion
- Much simpler than compiling Rust avt to WASM

### Next Steps
1. Test with real TUI application (vim)
2. Verify shell_snapshot returns correct screen state via MCP
3. Consider image rendering (PNG export)

---

## Checkpoint 3: 2025-12-09 - Vim Test

### Goal
Test terminal emulator with real vim session (insert mode, new line, exit).

### Verification
```bash
npm run test:emulator
```

### Results
- Recorded actual vim session using node-pty
- Terminal emulator correctly renders vim screen:
  - Text lines ("Hello vim!", "Second line")
  - Vim's `~` markers for empty lines
  - Status bar with cursor position
  - Command line with `:q!`
- All 3 tests pass: 01-echo, 02-cursor, 03-vim

### Feedback
- @xterm/headless handles vim's complex escape sequences
- Recording real sessions produces accurate test fixtures
- Alternate screen buffer handled correctly

### Next Steps
1. Test with k9s or other TUI app
2. Verify MCP server integration end-to-end
3. Consider image rendering (PNG export via agg)

---

## Checkpoint 4: 2025-12-09 - K9s Integration Test

### Goal
Test terminal emulator with real k9s TUI application.

### Verification
```bash
npm run test:k9s
# Output in tests/04-k9s/output/
```

### Results
- k9s renders correctly with full TUI:
  - Box drawing characters (─, │, ┌, └, etc.)
  - Table columns with data
  - k9s logo with emojis
  - Navigation between views works
- Screenshots capture correct screen state
- Output files: step-01-k9s.txt, step-02-deployments.txt

### Feedback
- @xterm/headless handles complex TUI apps flawlessly
- Box drawing and unicode render correctly
- This validates the terminal emulator for production use

### Next Steps
1. Verify MCP server shell_snapshot works end-to-end
2. Consider adding image export (PNG via agg or canvas)
3. Add shell_wait_for tool for AI agent use