A brief names what it supersedes; a lane that cannot spawn says so

[HackTuah]

One convention, appended to CONVENTIONS.md. Documentation only.

Why

A coordinator was told to spawn subagents and run two review lanes. Both lane briefs it wrote still carried an earlier "do not spawn further subagents", copied forward from a message that had already been superseded, and neither brief said which instruction won. Both lanes then ran as two scoped passes by one reader.

The instruction was stale, not conflicting — which is exactly why it survived. A superseded sentence sitting beside a current one reads like a current one. That is the same defect class as a superseded claim surviving into a record, and worse in one respect: an instruction is acted on, not merely read.

The second half

Both lanes reported the limitation in their own verdicts, unprompted, rather than letting "two lanes" imply independence they did not have. That is the only reason it was caught before the record shipped. Independence is the entire content of a second lane — a second pass by the same reader shares its assumptions, its blind spots, and whatever the first pass concluded.

The rule

• A brief states which instruction it supersedes.
• A lane that cannot spawn says so in its verdict, not in a footnote elsewhere.

The failure cost nothing this time, which is the argument for writing it down rather than against it: the phrase that would have shipped — "two lanes, three rounds" — reads identically whether it is true or not.

Verification

format pass, compile pass, test pass, credo pass, optional deps pass, docs pass,
reuse pass (168 tracked; 55 in scope, 53 headered + 2 sidecar), licence files pass
Gate OK.  GATE_EXIT=0