AgentTeams: SendMessage crossing — no sequence / ack — causes redundant re-briefs

Observed

Lead and teammate SendMessages can cross in flight:

1. Lead sends task A to teammate.
2. Teammate, still processing an earlier task B, completes B and sends a report.
3. Reports cross: lead sees teammate's B-report after sending A; teammate receives A after sending B-report.
4. Teammate then processes A and responds, but the output is confusing because it's about A, not the B-report lead just saw.

In one session, the inspector teammate reported the same task PASS three separate times because my "proceed with X" messages crossed their "X already done" replies.

Impact

• Redundant re-briefing wastes teammate context.
• Lead spends turns disambiguating which message answers which.
• In some cases, teammate repeats completed work because crossed messages read as a new assignment.

Suggested

• Attach sequence IDs to each SendMessage. Responses include the id they're answering.
• Or: surface "N messages ahead of you in the teammate's inbox" in the SendMessage ack, so the sender knows their message isn't next.
• Or: block lead's next SendMessage to the same teammate until the prior one has been processed.

Env

Claude Code CLI (macOS). CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1. Skill: swarm-team.