Sub-agent handoffs lose the case

A Polylane-style handoff can look complete because the next agent receives a task, a status line, and a confident summary. The case still gets lost when the evidence — failing test, exact file, trace, reproduction, or artifact path — never reaches the fixer who has to act on it.

That is the handoff tax: every boundary compresses context, and the compression usually keeps the story while dropping the proof. Multi-agent systems need evidence as a first-class payload, not an optional appendix to the delegation message. Pass the artifact, the failing assertion, the reproduction, and the acceptance check together; otherwise the fixer starts by rediscovering the case.

A successful delegation is not a successful transfer until the fixer can open the evidence and close the loop.