Observability Rewrite with Diagnostics Channels

The observability system has been completely reimplemented using Node.js diagnostics channels, replacing the previous console.log() and custom Observability.emit() interface. The new system is silent by default with zero overhead when no subscribers are listening.

Events are structured with type, payload, and timestamp and routed to seven named channels:

• agents:state — state updates
• agents:rpc — RPC calls and errors
• agents:message — message lifecycle and tool interactions
• agents:schedule — task scheduling and queue events
• agents:lifecycle — agent connection and teardown
• agents:workflow — workflow state transitions
• agents:mcp — MCP client operations

Use the typed subscribe() helper for type-safe event access in development, or automatically forward all diagnostics channel messages to Tail Workers in production without subscription code needed in the agent itself.

keepAlive() Prevents Durable Object Eviction

Durable Objects are evicted after 70–140 seconds of inactivity, which can interrupt long-running operations like LLM streaming or external API calls. The new keepAlive() method creates a 30-second heartbeat schedule that resets the inactivity timer.

Two usage patterns are available:

• Manual control — Call keepAlive() and invoke the returned disposer function when complete
• Automatic cleanup — Use keepAliveWhile(asyncFn) to wrap async operations with automatic heartbeat start/stop

Key details: Multiple concurrent keepAlive() calls operate independently, AIChatAgent calls it automatically during streaming responses, and the heartbeat integrates with the existing scheduling system.

waitForMcpConnections Ensures Tool Availability

AIChatAgent now waits for MCP server connections to settle before invoking onChatMessage, ensuring this.mcp.getAITools() returns the complete tool set. This is especially important after Durable Object hibernation when connections are being restored in the background.

Configure the wait behavior with the waitForMcpConnections property: use the default { timeout: 10_000 } to wait up to 10 seconds, set true to wait indefinitely, or set false to disable waiting entirely.