A client-callback throw only becomes a JSON-RPC error RESPONSE to the
agent's session/request_permission — runScenario itself kept going, so a
tolerant agent could treat the error as a denial and the scenario would
pass, or worse, record: the impossible click baked into fixture and
golden, green on every replay. The mismatch is now captured as a harness
error while the agent is answered plain cancelled (a well-defined path
it cannot reinterpret), and the step loop rejects the run on it as soon
as the in-flight step settles. The spec asserts the rejection instead of
the agent-side error echo.
The package, coverage, and permission scripting all shipped on this
branch, so the RFC moves to implemented/ with the lifecycle rewrite:
Proposal becomes a present-tense Decision, Acceptance criteria and Risks
fold into Testing/Consequences with what actually pinned each one (the
zero-byte extraction parity, the 100% per-file coverage via the fake
bin, the vitest-in-src caveat, the per-suite pin cost).
Tianyi Cui