How do you stream structured logs to a browser alongside agent events?

Category: Observability & Tracing

Answer

A custom LogHandler that reads a ContextVar (request_id, user_id, agent_step, message) and forwards each emitted log record to a per-request asyncio.Queue. The same queue also carries SSE events to the browser; the consumer stream merges them into one wire.

Concrete examples from the fca project context

Example 1

SSELogHandler.emit(record): queue.put_nowait({”type”: “log”, "record": ...});

Example 2

ContextVar ensures the right request_id / agent_step is in scope per async task.

Example 3

The browser sees logs and events interleaved chronologically, no need for a separate log endpoint.

Data flow / flow chart

logger.info(...) -> SSELogHandler -> per-request queue
  queue -> async generator -> SSE events
  (logs + agent events in one browser stream)

Takeaway

Streaming the same logs your SRE sees into the browser debug panel halves diagnosis time.