feat: Add agent-bus power for multi-agent collaboration

[zanewebb]

Summary

Adds a new Kiro Power that enables multiple agent sessions to discover each other, exchange messages, and coordinate work via a filesystem-backed message bus.

Motivation

When running multiple Kiro sessions in parallel (e.g., via cmux for oncall triage, parallel development, or research+implementation pipelines), agents have no way to communicate. This power provides the missing coordination layer.

Real-world use case: During AWS Firewall Manager oncall, we had 34 open sev-2 tickets. We spawned 3 parallel Kiro investigators via cmux, each working a different ticket. The coordinator session needed to read findings, prevent duplicate work, and synthesize priorities — but agents had no awareness of each other.

What's included

MCP Tools (5)

Tool	Description
agent_post_message	Send messages between agents
agent_read_messages	Read inbox with optional sender filter
agent_signal	Emit named coordination signals
agent_wait_signal	Check for signal completion
agent_list_agents	Discover registered agents

Steering Files (2)

• workflows.md — Cooperation patterns: oncall triage, parallel development, pipeline, status dashboard
• cmux-integration.md — Using Agent Bus with cmux terminal multiplexer

Architecture

• Filesystem-backed transport at /tmp/kiro-agent-bus/
• No daemon process required
• Inspectable and debuggable
• Configurable via KIRO_AGENT_BUS_DIR env var

Power Structure

agent-bus/
├── POWER.md                          # Full documentation with examples
├── mcp.json                          # MCP server configuration
├── steering/
│   ├── workflows.md                  # Cooperation patterns
│   └── cmux-integration.md           # cmux integration guide
└── server/
    ├── src/index.ts                  # MCP server (TypeScript)
    ├── src/test.ts                   # Tests
    ├── package.json
    └── tsconfig.json

Related

• Feature request: https://github.com/kirodotdev/Kiro/issues/TBD (inter-agent message bus for kiro-cli)
• Works with cmux terminal multiplexer