What it means
Whatever an advisor is — an API, a client tool, a local runtime, a mesh peer — talking to
it ends in one of the same results: a normalised answer, or a typed failure (timeout,
rate_limited, auth_failed, malformed, empty, unavailable, cancelled, error)
with a diagnostic that carries no secret. Provider quirks stop at the adapter.
How it works
scripts/lib/advisors/contract.mjs defines the failure type, the classification of HTTP
statuses and process exits, the prompt (evidence, the executor's hypothesis and prior
advice marked as opinions), the normalisation of an answer, and consultOne, which runs
an adapter under a deadline and a cancellation signal and turns any failure into a result.
contract.test.mjs runs every adapter against a fake fetch or a fake process.
How to see it
node --test scripts/lib/advisors/contract.test.mjstest/cases/731_advisor_transport_contract.sh runs the suite with no credential in the
environment.
What it does not cover
It does not prove a live vendor behaves as the fakes do; that is learned at the first consultation and recorded. It does not test a live mesh of two runtimes; the peer adapter is tested against a fake server.
Why it exists
An adapter that throws a vendor's own error into the workflow makes every caller learn that vendor. One contract, tested without the vendor, is what keeps CI free of live models (ADR 0098).