Problem

When using sessions_spawn to run long tasks (research, code generation, multi-step workflows), the parent session has no visibility into progress. The only options are:

• Wait for completion (could be 10-30+ minutes)
• Poll sessions_list repeatedly (wasteful, not push-based)

This makes it difficult to build reliable multi-agent pipelines where the orchestrator needs to track worker status.

Current Behavior

Parent spawns sub-agent → waits → sub-agent completes → result delivered
(no intermediate status updates)

Proposed Solution

Two complementary approaches:

Option A: Periodic status pings

Sub-agents emit lightweight status updates to the parent every N minutes:

{ "type": "progress", "sessionKey": "...", "status": "running", "lastActivity": "...", "stepCount": 3 }

Option B: sessions_list improvements

Add last_activity_at and current_step fields to the sessions list response, so orchestrators can check status without waiting for full completion.

Use Case

Multi-agent automation systems where:

• A main agent spawns 3-5 worker sub-agents
• Workers run for 10-30 minutes each
• Main agent needs to know if workers are stuck, failed, or progressing

Reported by a user running a 24/7 multi-agent automation system with nightly workshop sub-agents