Mid-server transforms: tests we expect before merge

Mid-server transforms earn trust when tests cover null payloads, slow downstreams, and duplicate deliveries. We supply a mock downstream that can be flipped into failure modes without editing production secrets.

Cohorts document the matrix of retries and idempotency keys before writing clever branching. Clever branching without that matrix is how silent duplication sneaks into operational logs.

We end the lab with a chaos drill scoring rubric focused on operator readability, not vanity uptime numbers. Readable errors beat opaque retries every time.