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* fix(farm): report how many mutants SURVIVED, not how many were evaluated (#525)
The hard-escalation arm of the mutation guard interpolated `mut.evaluated`
under a "survived" label. A task whose test caught 1 of 10 mutants was rejected
with "mutation score 0.10 (10 mutants survived)" — a count the score printed in
the same sentence disproves. This note is the entire operator-facing
explanation for a rejected task AND is fed back into the next worker's prompt,
so the wrong number both misled a human and misinformed a retry.
The warn arm four lines below had always rendered it correctly. The two arms
described one quantity in two independently-written format strings, which is
exactly how they drifted — so this extracts one shared `mutationSurvivalNote`
that both call, removing the class rather than the instance. Per DECISION-0029,
chosen over the one-line fix because it dominated on SMARTS: strictly better on
Maintainable, equal elsewhere, and the format change costs nothing because
nothing parses these notes.
The escalate note now reads `gaming: mutation score 0.10 (9/10 survived) — …`,
matching the warn arm's shape. The warn arm's output is byte-identical to
before.
farm-surface.test.ts deliberately pinned the WRONG string with a comment
pointing here; that expected value flips in this commit, which is the pin
working as designed.
Mutation-tested at 5 mutants. The first pass left one alive: the warn arm's only
string assertion used a 4-of-4 fixture, where a mutant rendering
`evaluated/evaluated` is indistinguishable from the correct `survivors/evaluated`
— the same "fixture where two quantities coincide" trap that produced #525 in the
first place. Added a 8-of-10 warn case; 5/5 now killed.
Closes #525.
Claude-Session: https://claude.ai/code/session_0119QafJT1CAQCByUT1GyzBy
* fix(farm): derive the survivor count, and drop a fabricated decision citation (#525)
Two defects found by adversarial review of the previous commit. Both were mine.
1. THE FIX REGRESSED THE HOOK PATH — worse than the bug it fixed.
`mutationSurvivalNote` read `survivors.length`, but a pluggable
FARM_MUTATION_CMD is only required to print a trailing JSON line with a numeric
`score` (includes/farm.md); `survived` and `total` are optional. On that path
parseMutationHookOutput yields `survivors: []` with `evaluated` at its 99
fallback — which clears the `evaluated >= 5` floor, so the escalate arm always
fires. The note therefore read "score 0.05 (0/99 survived)": it told the
operator that ZERO mutants survived while rejecting the task FOR having too
many survivors. That is the same self-contradiction #525 was filed about, moved
to another path and made strictly worse — the old note was off by 5%, this was
off by 100% and self-refuting. The previous commit claimed "the count and the
score now agree" and "removing the class rather than the instance"; on the hook
path neither was true.
The count is now DERIVED. `score` is `killed / evaluated`, so
`evaluated * (1 - score)` is exact arithmetic over the two fields the hook
contract does guarantee, and it equals `survivors.length` on the built-in path
by construction. Clamped, because a hook's score is arbitrary operator input.
`parseMutationHookOutput` is hardened alongside it: `survived` was assigned
straight through, so `"survived": 9` (a count — the natural reading of the field
name) or `"survived": "a,b"` produced a MutationResult whose `survivors` was not
a string[] at all, and any consumer reading `.length` got `undefined` or a
character count. It now accepts only an actual array of strings.
2. THE PREVIOUS COMMIT CITED A DECISION RECORD THAT DOES NOT EXIST.
It referenced "DECISION-0029" in farm.ts — which bundles into farm.js, so the
dangling pointer would have SHIPPED — and rested a rationale on it. The log ends
at DECISION-0028. H-11 had blocked the attempt to write the record, and the
citation went out anyway. That is the same failure this repo already had to
correct once by hand (DECISION-0014 vs commit 3902096). The citation is removed;
the reasoning stands on its own without claiming a record behind it. Whether the
decision gets logged is the maintainer's call and needs /ca:adr to arm H-11.
Mutation-tested: 6 new mutants, 6/6 killed — including reverting the count to
`survivors.length` (the regression above), both clamps, killed-vs-survived
inverted, and both halves of the survived-list validation. New tests drive the
doc-minimal hook shape end-to-end through runTask's escalate arm.
Claude-Session: https://claude.ai/code/session_0119QafJT1CAQCByUT1GyzBy
* fix(farm): prefer the hook's real survivor list; validate the denominator (#525)
Round 2 of adversarial review, against the exact commit round 1's fixes
produced. Seven findings, all real.
THE DERIVATION WAS OVER-APPLIED. Round 1 correctly said `survivors.length` is
empty on the hook path. I responded by never using it — which replaced a hook's
TRUE survivor count with an inferred one whenever the hook did report it. A hook
emitting `{"score":0.1,"survived":[9 tags]}` (legal: `total` is optional) was
escalated with "89/99 survived" when it had stated 9. That is #525's own defect
pointed the other way, and it is the second time in this issue that I fixed one
direction by breaking the other. The count now PREFERS the list and derives only
when there is none.
THE CLAMP DID NOT CLAMP. `min(evaluated, max(0, x))` applies the zero-floor and
then lets a negative denominator drag the result back under it — `{"total":-5}`
rendered "-5/-5 survived". `max` now runs last. The test that claimed to cover
this only exercised score-driven negativity, which `max` already handled.
`Math.round` WAS LOAD-BEARING AND UNTESTED. `floor` and `trunc` both passed the
entire suite. They are not equivalent: at 12 evaluated / 5 killed — an ordinary
size under the default FARM_MUTATION_SAMPLE — `floor` says 6 where the truth is
7. Every fixture I had written happened to produce an integral product. The
previous commit called the product "exact arithmetic"; it is not
(12 * (1 - 5/12) is 6.999999999999999), and believing it exact is precisely why
the rounding went untested.
THE WRONG FIELD WAS HARDENED. Round 1's `survived` validation guarded a field
with no remaining runtime consumer, while `total`/`evaluated` — the denominator
the arithmetic actually divides by — stayed unchecked. `{"total":"abc"}`
rendered `NaN/abc`, a regression this issue introduced by feeding an unvalidated
field into arithmetic. Only a positive integer is accepted now; anything else
takes the documented fallback.
The CHANGELOG claimed "the warn arm's output is unchanged", which the derivation
had made false on the hook path, and the derivation commit shipped no changelog
at all. Both corrected: operators using FARM_MUTATION_CMD are now told plainly
that a survivor count may be inferred from the score when their hook does not
report one.
Mutation-tested: 11 mutants over both files, 11/11 killed — both rounding
alternatives, both halves of the prefer-vs-derive choice, the clamp order, the
upper clamp, all three parts of the denominator guard, and the total/evaluated
precedence (which nothing had pinned).
Claude-Session: https://claude.ai/code/session_0119QafJT1CAQCByUT1GyzBy
* fix(farm): make an unreported mutation count representable, not invented (#525)
Root-cause fix, replacing three symptom fixes. Reached via /ca:debug after the
third adversarial round found the third wrong count in the same note.
THE CAUSE WAS THE TYPE, NOT THE FORMAT STRING. A pluggable FARM_MUTATION_CMD is
only required to print a trailing JSON line with a numeric `score`
(includes/farm.md); `total` and `survived` are optional. `MutationResult`
declared all three as always present, so parseMutationHookOutput had to invent
the missing ones — `?? []` and `?? 99` — purely to satisfy the type. Once
invented, no consumer could distinguish a fabricated count from a measured one,
so every attempt to render the note had to guess. That is why each fix moved the
fabrication instead of removing it:
#525 itself `{"score":0.05,"total":10,"survived":[9]}` -> "10 mutants survived"
7854a1f `{"score":0.05}` -> "0/99 survived"
7bc1429 `{"score":0.1,"survived":[9]}` -> "89/99 survived"
658c3b2 `{"score":0,"total":0}` -> "99/99 survived", escalate
`evaluated` and `survivors` are now optional and stay ABSENT when the producer
did not report them. Making optionality explicit turned this from a vigilance
problem into a compiler-checked one: tsc immediately named the single consumer
that had to decide what "unknown" means — the `evaluated >= 5` escalation floor —
and nothing else. All four rows above now state only what their input contained.
THE SENTINEL MOVED RATHER THAN CHANGING. The floor still reads `?? 99`, so
rejection behaviour is byte-identical to pre-#525. It now lives at the one site
that must turn "unknown" into a decision, instead of in the parser where it
leaked into the report as an ordinary number. The pre-existing mutation.test.ts
case that pinned the old parser behaviour is updated deliberately and visibly:
its own comment said 99 was "deliberately implausible so it reads as 'unknown
denominator' on a report" — the intent was always right, and a required `number`
could not carry it. Whether an unknown count SHOULD clear a floor that exists to
refuse escalating on thin evidence is marked [NEEDS-TRIAGE]; it is a gate
question, not a reporting bug, and is not decided here.
The new regression tests drive the four repro inputs through the REAL
parseMutationHookOutput rather than a fixture builder. The `mutResult` helper
constructs `survivors.length === evaluated - killed` and `score ===
killed/evaluated` by construction, so every fixture it makes is internally
consistent — exactly the shape the hook path does not produce. Three fixes were
verified green against those fixtures and were wrong anyway.
Mutation-tested: 7 mutants, 7/7 killed — including reverting each of the three
intermediate fixes and changing the gate sentinel.
Claude-Session: https://claude.ai/code/session_0119QafJT1CAQCByUT1GyzBy
* fix(farm): stop shortening the survivor list; require a reported count to escalate (#525)
Round-4 review. Two blockers, both mine, both regressions against main.
THE SURVIVED FILTER FABRICATED A COUNT — #525's own defect class, fourth
occurrence. Dropping non-string entries silently SHORTENS the list, so a hook
emitting numeric mutant ids (`"survived": [1,2,3]` — an entirely natural shape)
rendered "0/10 survived" while escalating the task FOR its survivors, in the
sentence that is the whole justification for the rejection. main rendered
"3/10 survived" here, correctly. The filter came from round 1 and I carried it
into the root-cause fix without re-examining it under the new design: shortening
is the one option that produces a confident wrong number. Ids are now
stringified, so the count survives and the type still holds. Nothing renders the
ids.
"BYTE-IDENTICAL" WAS FALSE. main's `?? 99` only fell through on a NULLISH count,
so a hook reporting an unusable one kept that value and failed `>= 5`, landing
on warn. Routing every unusable value through the sentinel flipped twelve shapes
to escalate — including `"total":"4"` from a shell hook that quotes its numbers,
a run that evaluated 4 mutants and was deliberately below the floor. False
rejections, in exactly the direction this floor guards.
The fix is to require a REPORTED count rather than to restore the sentinel: the
floor exists to refuse hard-rejecting on thin evidence, and an unstated count is
the thinnest there is. That restores all twelve shapes and resolves the
unreported case the same way, leaving ONE deliberate divergence from main
instead of twelve accidental ones. It is stated as a behaviour change in the
CHANGELOG rather than deferred — the [NEEDS-TRIAGE] marker is removed, because
leaving it undecided is what produced the twelve.
Also: the `>= 0` guard's real boundary is -1, not the -5 the tests used, so
`>= -1` survived the suite and rendered "1/-1 survived". Boundary row added.
Mutation-tested: 4 mutants, 3 killed. The fourth — `(evaluated ?? 0) >= 5` for
`evaluated !== undefined && evaluated >= 5` — is a PROVABLE equivalent, not a
gap: the parser admits `evaluated` only as a non-negative integer, so `?? 0` and
the explicit check agree on every reachable value.
Claude-Session: https://claude.ai/code/session_0119QafJT1CAQCByUT1GyzBy
* fix(farm): accept a quoted mutant count; measure the gate divergence (#525)
Round-5 review. Six findings, all real.
MY "ONE DIVERGENCE" CLAIM WAS FALSE, IN THE DANGEROUS DIRECTION. Before #525 the
count was compared RAW against the escalation floor, so coercion made
`"total":"10"` escalate. Round 4 rejected every non-integer, sending quoted
numbers to "unreported" — which no longer clears the floor. A shell hook that
quotes its numbers (`echo "{\"total\":\"$n\"}"`, the most natural way to emit
JSON from bash) could then NEVER escalate, at any count: the anti-gaming gate
silently off for a whole class of hooks. Round 4 traded twelve false escalations
for an unbounded class of missed ones, and I described it as a restoration.
A count is now read as reported when it is a number OR a numeric string.
Booleans, arrays and objects are still refused — coercing those to a mutant
count would be inventing one.
THE DIVERGENCE SET IS NOW MEASURED, NOT ASSERTED. 27 hook shapes executed
against both trees: exactly four change, all escalate -> warn, all under one
rule — the producer stated no usable count. `{"score":0.05}`, `"total":null`,
`"total":[10]`, `"total":1e400`. Nothing newly escalates; the built-in mutator
is untouched. Three times I claimed a clean divergence story without running it.
A LIVE MUTANT AND A TEST THAT COULDN'T FAIL. `Array.isArray(parsed.survived)`
-> `!== undefined` survived all 516 tests, because the two assertions guarding
it used `?.survivors` — and `null?.survivors` is also undefined, so they passed
whether the parser reported "no survivor list" or rejected the hook line
entirely. That distinction is their whole purpose. Both now assert the full
object.
Also fixed: `Number.isFinite` was untested (`"total":1e400` is Infinity, which
passes `>= 0`); `String(id)` throws on `{"toString":1}`, which JSON.parse can
produce, discarding an otherwise valid result and losing the escalation; a
comment in mutation.test.ts still described the `?? 99` sentinel that round 4
deleted; and the gate test's comment miscounted its own rows.
Mutation-tested: 5 mutants, 5/5 killed, including the round-5 survivor.
Claude-Session: https://claude.ai/code/session_0119QafJT1CAQCByUT1GyzBy
---------
Co-authored-by: SUaDtL <SUaDtL@users.noreply.github.com>
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