# MACP Phase 2A — Event Bridge + Notification System

**Branch:** `feat/macp-phase2a`
**Repo worktree:** `~/src/mosaic-bootstrap-worktrees/macp-phase2a`

---

## Objective

Build the event bridge that makes MACP events consumable by external systems (OpenClaw, Discord, webhooks). This is the observability layer — the controller already writes events to `events.ndjson`, but nothing reads them yet.

---

## Task 1: Event File Watcher (`tools/orchestrator-matrix/events/event_watcher.py`)

New Python module that tails `events.ndjson` and fires callbacks on new events.

### Requirements:
- Watch `.mosaic/orchestrator/events.ndjson` for new lines (use file polling, not inotify — keeps it portable)
- Parse each new line as JSON
- Call registered callback functions with the parsed event
- Support filtering by event type (e.g., only `task.completed` and `task.failed`)
- Maintain a cursor (last read position) so restarts don't replay old events
- Cursor stored in `.mosaic/orchestrator/event_cursor.json`

### Key Functions:
```python
class EventWatcher:
    def __init__(self, events_path: Path, cursor_path: Path, poll_interval: float = 2.0):
        ...
    
    def on(self, event_types: list[str], callback: Callable[[dict], None]) -> None:
        """Register a callback for specific event types."""
    
    def poll_once(self) -> list[dict]:
        """Read new events since last cursor position. Returns list of new events."""
    
    def run(self, max_iterations: int = 0) -> None:
        """Polling loop. max_iterations=0 means infinite."""
```

### Constraints:
- Python 3.10+ stdlib only (no pip dependencies)
- Must handle truncated/corrupt lines gracefully (skip, log warning)
- File might not exist yet — handle gracefully
- Thread-safe cursor updates (atomic write via temp file rename)

---

## Task 2: Webhook Adapter (`tools/orchestrator-matrix/events/webhook_adapter.py`)

POST events to a configurable URL. This is how the OC plugin will consume MACP events.

### Requirements:
- Accept an event dict, POST it as JSON to a configured URL
- Support optional `Authorization` header (bearer token)
- Configurable from `.mosaic/orchestrator/config.json` under `macp.webhook`:
  ```json
  {
    "macp": {
      "webhook": {
        "enabled": false,
        "url": "http://localhost:8080/macp/events",
        "auth_token": "",
        "timeout_seconds": 10,
        "retry_count": 2,
        "event_filter": ["task.completed", "task.failed", "task.escalated"]
      }
    }
  }
  ```
- Retry with exponential backoff on failure (configurable count)
- Log failures but don't crash the watcher
- Return success/failure status

### Key Functions:
```python
def send_webhook(event: dict, config: dict) -> bool:
    """POST event to webhook URL. Returns True on success."""

def create_webhook_callback(config: dict) -> Callable[[dict], None]:
    """Factory that creates a watcher callback from config."""
```

### Constraints:
- Use `urllib.request` only (no `requests` library)
- Must not block the event watcher for more than `timeout_seconds` per event
- Log to stderr on failure

---

## Task 3: Discord Notification Formatter (`tools/orchestrator-matrix/events/discord_formatter.py`)

Format MACP events into human-readable Discord messages.

### Requirements:
- Format functions for each event type:
  - `task.completed` → "✅ **Task TASK-001 completed** — Implement user auth (attempt 1/1, 45s)"
  - `task.failed` → "❌ **Task TASK-001 failed** — Build error: exit code 1 (attempt 2/3)"
  - `task.escalated` → "🚨 **Task TASK-001 escalated** — Gate failures after 3 attempts. Human review needed."
  - `task.gated` → "🔍 **Task TASK-001 gated** — Quality gates running..."
  - `task.started` → "⚙️ **Task TASK-001 started** — Worker: codex, dispatch: yolo"
- Include task metadata: runtime, dispatch type, attempt count, duration (if available)
- Keep messages concise — Discord has character limits
- Return plain strings (the caller decides where to send them)

### Key Functions:
```python
def format_event(event: dict) -> str | None:
    """Format an MACP event for Discord. Returns None for unformattable events."""

def format_summary(events: list[dict]) -> str:
    """Format a batch summary (e.g., daily digest)."""
```

---

## Wiring: CLI Integration

Add to `bin/mosaic-macp`:
```bash
mosaic macp watch [--webhook] [--once]
```
- `watch`: Start the event watcher with configured callbacks
- `--webhook`: Enable webhook delivery (reads config from `.mosaic/orchestrator/config.json`)
- `--once`: Poll once and exit (useful for cron)

---

## Verification

1. Create a test `events.ndjson` with sample events, run `event_watcher.poll_once()`, verify all events returned
2. Run watcher with webhook pointing to a local echo server, verify POST payload
3. Format each event type through `discord_formatter`, verify output strings
4. `mosaic macp watch --once` processes events without error
5. Cursor persistence: run twice, second run returns no events

## File Map
```
tools/orchestrator-matrix/
├── events/
│   ├── __init__.py               ← NEW
│   ├── event_watcher.py          ← NEW
│   ├── webhook_adapter.py        ← NEW
│   └── discord_formatter.py      ← NEW
```

## Ground Rules
- Python 3.10+ stdlib only
- No async/threads — synchronous polling
- Commit: `feat: add MACP event bridge — watcher, webhook, Discord formatter`
- Push to `feat/macp-phase2a`