Agent Observability & Event Streaming

Add structured event logging and streaming for agent work sessions, enabling real-time observation in the web UI and future interactive chat.

Goals

• Full visibility into agent reasoning and tool usage
• Real-time streaming to web UI via SSE
• Persistent event log for debugging and learning
• Design supports future interactive chat

Architecture

Engine.hs                    Event Store              Web UI
    │                            │                      │
    ├─ onAssistantMessage ──────►│ INSERT event         │
    │                            │──── SSE push ───────►│ render
    ├─ onToolCall ──────────────►│ INSERT event         │
    │                            │──── SSE push ───────►│ render  
    ├─ onToolResult ────────────►│ INSERT event         │
    │                            │──── SSE push ───────►│ render

Schema

CREATE TABLE agent_events (
  id INTEGER PRIMARY KEY,
  task_id TEXT NOT NULL,
  session_id TEXT NOT NULL,
  timestamp DATETIME,
  event_type TEXT,  -- assistant, tool_call, tool_result, user, cost, error, complete
  content TEXT,     -- JSON payload
  FOREIGN KEY (task_id) REFERENCES tasks(id)
);

Event Types

data AgentEvent
  = EventAssistant Text
  | EventToolCall Text Value
  | EventToolResult Text Bool Text
  | EventUserMessage Text
  | EventCost Int Int
  | EventError Text
  | EventComplete