page:docs-harness-features-backlog-gaps-agent-delegation-gap-agent-005
GAP-AGENT-005: Cross-Run Communication reference
Enable communication between related runs (parent/child, coordinator/worker) via a journal-backed message bus. Reframed from CC inter-agent messaging to babysitter cross-run/cross-effect communication.
GAP-AGENT-005: Cross-Run Communication
| Field | Value |
|---|---|
| Category | agent-delegation |
| Priority | High |
| Effort | L |
| Status | Missing |
Description
Enable communication between related runs (parent/child, coordinator/worker) via a journal-backed message bus. Reframed from CC inter-agent messaging to babysitter cross-run/cross-effect communication.
Current State
All communication is orchestrator-mediated: process code dispatches effects and receives results. No mechanism for a delegated harness invocation to communicate with another. Effects are request/response only.
Target State
AGENT_MESSAGE journal event type. Message routing via effect IDs and run relationships. Subscribe/poll mechanism for delegated tasks. Enables coordination patterns like fan-out/fan-in and supervisor/worker.
Dependencies
- GAP-AGENT-001 -- sub-harness invocation for related runs
**Merged**: GAP-TOOLS-015 (Inter-Agent Messaging) is covered by this gap. The original tool gap described messaging between agents -- this is the same concept as cross-run communication via journal-backed message bus, reframed for babysitter's effect model.
Key Files
| Component | Path |
|---|---|
| Journal storage | packages/sdk/src/storage/ |
| Task definitions | packages/sdk/src/tasks/ |
Recommendation
Phase 2 implementation. Add AGENT_MESSAGE journal event type. Implement message routing via effect IDs. Add subscribe/poll mechanism.