ADR 0123 — Terminal output is accepted before commit and tool rounds keep causal order

Context

A provider stop with no content was committed as success even when the application protocol required an answer. The only downstream remedy was to rewrite an already terminal durable record. Separately, one persisted assistant can contain several tool steps, but projection grouped every call before every result. A dependent call therefore appeared parallel with the call whose result created its input, and final text appeared before its evidence.

Decision

• A protocol may declare terminalAcceptance. The built-in require-output rule accepts non-blank text, generated files, structured provider parts and an explicit tool-only policy stop; a callback may define another rule.
• Acceptance runs only for would-be completed outcomes and before terminal CAS. Interrupted, cancelled and failed records retain their actual reason.
• Canonical parts are projected in their persisted order. Adjacent assistant parts form one assistant message and adjacent results form one tool message; changing role flushes the current round.
• Tool chronology is valid only when every unique call is followed by exactly one result. Parallel calls before their results remain one legitimate round.

Consequences

• Protocols that permit empty completion keep the default allow-empty path.
• A rejected candidate is a failed assistant and is never exposed as successful durable output.
• A runtime can feed its own multi-step terminal record into the next provider call without consumer-side history rewriting.