Review approach signal — saying when the approach, not the patch, is the open question

The problem, as measured

One change to extractAndStripMeta took three attempts across two pull requests before it landed:

PR	approach	rounds	findings	source diff
#9097	add a `timeout` to the vm call	3	18 (9 Critical)	grew ~5x
#9136	run the walk inside the vm, then a child process per call	6	56 (12 Critical)	grew ~4x
#9325	stop evaluating; parse the literal	1	—	—

Every one of those 74 findings was individually correct. Each round found a real hole the previous patch did not cover: a getter deferring its work to the host, a serializer sharing a lexical scope with the literal it walked, a promise reaction under microtaskMode, unbounded allocation. The review was not wrong at any point.

It was, however, structurally unable to reach the conclusion that mattered. Every finding is anchored to a file:line inside the current diff — that is what a finding is. So the review could say where an approach leaks, but never that a different approach would retire all of the leaks at once. The fix that worked deleted the mechanism, and all 74 findings went with it.

The signal that something was structurally wrong did exist. did not converge within the reverse-audit round cap was emitted four times across the two PRs. It is filed as a coverage gap — "we did not finish looking" — rather than as a conclusion about the change. Nothing was responsible for reading it as "stop patching".

What this adds

One advisory paragraph, and one clause on the terminal verdict line, when a PR has taken enough rounds and grown enough since the review first measured it.

It fires when all of:

this round confirmed at least one finding (the pre-cap verdict, baseEvent, is not APPROVE)
the round is at or past the threshold (default 5; review.approachRounds)
a baseline exists from an earlier round
the source diff is past the module's existing non-trivial floor (100 lines)
the diff has grown by at least APPROACH_GROWTH_FACTOR (3x) since the baseline

This round's reverse-audit round-cap stop rides along as a corroborating clause when present. It is never a trigger on its own.

Design decisions

It is not a finding. Findings are what the autofix loop consumes, and the loop patching each finding in turn is the pattern being interrupted. A finding here would be fixed rather than read. This addresses the human deciding what happens next, so it is a body paragraph and a verdict-line clause.

It never moves the verdict. No cap, no event change, no blocker. A PR that is legitimately large and legitimately iterated must pay nothing for a false positive beyond one paragraph. This mirrors lowSignal, the existing disclosure-only field it is modelled on.

It never fires on APPROVE. An approve is convergence. The convergence posture composes a deferrals-only late Approve deliberately, as the loop's stop signal; telling that PR to reconsider itself would contradict the outcome the loop is steering toward, in the same body.

The baseline is a baseline, not the previous round's size. #9136 went 228 → 920 source lines across six rounds — about 1.3x per round, which no per-round delta would notice, but 4.0x cumulatively. Ledger.src0 records the first round's measurement and is carried forward unchanged, so a diff that shrinks cannot rewrite its own baseline and erase the growth already on record.

One setting, not two. review.approachRounds is the knob an operator would reach for — it maps to a policy number the repo already uses, and raising it far enough silences the signal. The growth factor stays a module constant beside LOW_SIGNAL_SRC_DIFF_LINES, which is exactly how the sibling disclosure's own threshold is expressed.

What this does not do

It cannot see across pull requests. Every cross-round mechanism is keyed to one PR: the marker rides that PR's review bodies, the side file is named for its number, and recovery walks only its reviews. #9097 → #9136 → #9325 as three attempts at one fix is not detectable by any extension of this machinery. Of the motivating incident, only #9136's own six rounds and 4x growth would have fired. #9097, at three rounds, would not have.

It does not count repeated non-convergence. The round-cap marker is written per run and fenced to that run's plan epoch, precisely so a stale stop cannot cap a verdict that did not stop. Summing it across rounds needs a second persisted counter — a forgeable monotone tally with no code to re-assert it against. The paragraph therefore claims only what is true of this round.

It is retroactively blank. No PR in flight carries a baseline, and unknown marker keys are dropped on read. The signal stays silent until a PR has posted two rounds after this ships. The src0 > 0 arm is what makes the absent case degrade to silence rather than to a false "no growth".

The round counter fails open. Any failure recovering the side file reads as round 1, so a force-push or an account switch silently disarms the signal. That direction is deliberate: an advisory signal should fail toward silence.

Growth is measured in source lines, excluding tests. This is consistent with lowSignal and the topology metric, and it means a PR that balloons purely in test code will not trip the growth arm. This is the one genuinely contestable metric choice here; diffLines would catch more and also fire more often.

Trust

src0 is untrusted body data, like every other marker field. Unlike a finding, a bare number has nothing to re-assert it against: a forged small value fires the paragraph, a forged large one silences it. The entire blast radius is one advisory paragraph — it never reaches a verdict, a cap, or an event.