cross-agent-blackboard

name	cross-agent-blackboard
description	Use when more than one agent works on the same problem. The blackboard is the shared context — without it, agents duplicate work and contradict each other.
version	1.0.0
author	kbot
license	MIT
metadata	{"kbot":{"tags":["agents","coordination","blackboard","multi-agent"],"related_skills":["specialist-routing","agent-handoff"]}}

Cross-Agent Blackboard

Single-agent sessions use memory. Multi-agent sessions need a blackboard — a shared write-read surface every participating agent sees.

When

• kbot --architect (plan + implement by two agents)
• /team running all 6 specialists against the same change
• agent_handoff passing control with preserved context
• Matrix agents collaborating on a research question

Iron Law

ANY AGENT TAKING OVER MUST READ THE BLACKBOARD BEFORE ACTING.
ANY AGENT LEAVING MUST WRITE TO THE BLACKBOARD BEFORE EXITING.

Protocol

Blackboard entries have four fields: type (decision/finding/blocker/artifact), key (short slug), value (the payload), author (agent id).

• blackboard_write({ type, key, value }) — before handing off or pausing.
• blackboard_read({ keyPrefix?, type? }) — on entry or after a long subagent call.
• blackboard_query() — full dump when context is lost.

Example Flow (from a real session)

1. researcher investigates a library version incompatibility.
2. Writes { type: 'finding', key: 'axios.v1-vs-v2', value: 'v2 breaks the retry middleware' }.
3. Hands off to coder via agent_handoff.
4. coder reads the blackboard, sees the finding, and skips re-researching.
5. Writes { type: 'artifact', key: 'axios-pin', value: 'pinned to 1.6.7 in package.json' }.
6. guardian runs later, reads both entries, confirms no regression, writes { type: 'decision', key: 'axios-pin', value: 'approved' }.

Total time from research to verified fix: 8 minutes. Without the blackboard: each agent would re-derive context, easily 25+ minutes.

Anti-Patterns

• Passing context through the user ("please tell the next agent X"). The user is not a message bus.
• Writing vague entries ("looked into the bug"). Name the finding concretely or don't write it.
• Reading only your own writes. Other agents' entries are the whole point.

What Emerges

With the blackboard habit, specialist chains start behaving like one compound agent. The user types one prompt, three specialists take turns, and the handoffs are invisible — because context never dropped.