verify_on_stop / pre_verify append a synthetic assistant "done" plus a
synthetic user nudge to keep the agent going one more turn before it can
claim completion. Both were flagged (_verification_stop_synthetic on the
nudge only), but the flags were never registered in
_EPHEMERAL_SCAFFOLDING_FLAGS, so the central _is_ephemeral_scaffolding()
filter that guards both persistence sinks (SQLite flush + JSON snapshot)
let them through. The resumed transcript then inherited loop-only
scaffolding, invalidating the prompt-prefix cache on later turns.
- add _verification_stop_synthetic and _pre_verify_synthetic to
_EPHEMERAL_SCAFFOLDING_FLAGS (the single chokepoint both sinks use)
- flag the blocked attempt assistant message too, not just the nudge, so
the whole synthetic pair drops together and persistence does not keep a
premature done with the nudge stripped (assistant to assistant adjacency)
The API-payload leak claimed in the report is already handled: the
chat_completions transport strips every underscore-prefixed message key
before the wire, so the marker never reaches strict providers.
Reported by patppham.
