docs(901): a quotation that resolves to nothing, and a universal over three pins that holds for two

Two review findings, both the class this record is about: prose that claims
more than the artifact says.

The neighbour-record citation presented a paraphrase in quotation marks.
`testing.guard-derives-population-from-source` line 96-97 reads "when the
authoritative source is missing, the answer is to create one, never to
approximate it with a predicate over text"; the record quoted it without "the
answer is to" and without the second "to", so a fixed-string lookup of the
quoted span found nothing anywhere under docs/ — #812's second defect, which
`testing.mutation-claims-are-executed` names explicitly. The quote marks are
gone rather than repaired: the source sentence spans a line break, so any
single-line verbatim quotation of it would still not resolve by grep, and an
open paraphrase claims only what it is.

The `mechanics:` field said the image-build pins fail with a message naming
the constant to update. Measured against
scripts/tests/test_image_build_delegates_the_spa_suite.py: PINNED_STAGE_COMMANDS
(line 589) and PINNED_VITE_CONFIG (line 798) name themselves,
PINNED_PACKAGE_SCRIPTS (lines 757-763) does not — it names the FILE and prints
both maps. 423bf94e7 corrected this same sentence for the hook half after
verifying it and left the image-build half an unverified universal.

The first replacement drafted here read "all four faults ask for the reason in
the same commit", which is false a second way: the hook-preamble fault
(test_hook_fire_log.py lines 162-167) asks for no reason at all, it reports
got={mentions}. The shipped sentence is scoped to the three pins whose fault
messages were read.

Refs #901

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015QqCpYFsKgnAnx6jVwrKiV

docs/decisions/records/testing/guard-pins-the-artifact-not-a-shape.md

@@ -7,7 +7,7 @@ supersedes: none
 superseded-by: none
 rule: 'A predicate that decides something by matching a SHAPE inside an artifact whose GRAMMAR it does not implement pins the artifact WHOLE instead — the whole file, or a whole named span, compared for equality under a STATED normalisation. The boundary is the grammar and never the file type: shell source, a workflow `run:` body, TOML, YAML, a jq expression and JSON5 all qualify, and a shape matched over the OUTPUT of a real parser for that grammar does not. Extracting a `run:` value with a real YAML parser and then matching shell inside it IS in the class, because the shell is the unparsed half. THE PIN IS THE DEFAULT FOR A NEW PREDICATE; REJECTED is the alternative of writing the shape-matcher and pinning only once it has been defeated. The defeat a remedy policy waits for is a false GREEN, so it is found by a reviewer or by an incident and never by the guard: "not defeated yet" is a statement about who has looked, not about the input space. A SHAPE-MATCHER IS THE EXCEPTION, and its argument carries FOUR things, written where the predicate is and re-read whenever a clause of it is widened. (1) The GRAMMAR named, and the parser that implements it — if the shape is matched over a real parse there is no exception to write. (2) The INPUT SPACE as a CLOSED enumeration with the reason it is closed: a generator whose output form is fixed, or a canonicaliser the guard itself runs. A list of the spellings the author thought of is not that reason, and is the thing that was defeated nine, seven and five times. (3) The FAILURE DIRECTION measured rather than asserted: each defeat the matcher claims to catch is a DECLARED, executed mutation under `testing.mutation-claims-are-executed`, because a shape-matcher''s miss is a false green and an unrun claim about a fail direction is not evidence. (4) WHAT IT BUYS over the pin, priced in a cost the pin actually charges — the artifact is edited routinely or written by tooling, so a pin would redden as background noise and train its readers to ignore it; or the artifact''s population is DISCOVERED rather than fixed, so there is nothing to pin. Fewer than four is a refusal, and neither elegance nor an unwillingness to update a constant is one of the four. TWO OTHER BARS ARE REJECTED for this exception: a NUMERIC one ("survives N adversarial spellings"), which measures the reviewer''s imagination rather than the input space and would have licensed the parser above through most of nine rounds; and a REVIEWER SIGN-OFF, which makes the exception depend on the very signal the threshold below says arrives late. THE THRESHOLD for withdrawing a shape-matcher already shipped is not a count of spellings: it is the moment the NEXT spelling is found by the REVIEWER rather than by the author, which is evidence that the author''s model of the input space is not the input space. TWO RIDERS, both measured. A pin assumes it is pinning the artifact that still DECIDES — ask what else could decide this and whether the pin would still match: another FILE that outranks it, another OCCURRENCE in the same file, another WORKFLOW, or a HOOK the pinned command invokes. And WIDENING A CLAUSE RETIRES THE PROOFS CALIBRATED AGAINST THE NARROW ONE: a canary asserting that a finer mutation still SURVIVES has as its precondition that the guard is deliberately coarse there, so widening the main clause turns the canary into a tautology, which reads exactly like a passing proof — re-derive every proof calibrated against the narrow clause in the same commit that widens it. THE COST IS STATED RATHER THAN DISCOVERED LATER: any edit to a pinned artifact reddens, and the pin is updated deliberately in the same commit, with a reason. That red IS the review trigger the pin exists to be. A pin also declares its NORMALISATION and what the normalisation cannot see, because "pinned whole" invites a reader to assume byte equality.'
 signals: 'pin the artifact whole · shape-matcher is the exception that argues for itself · the boundary is the grammar not the file type · predicate does not implement the grammar it parses · defeated by the next spelling · the reviewer found the next spelling · false RED versus false GREEN · nine defects one mechanism · seven respellings of a partial config match · five spellings of a lexical preamble rule · the four-part exception argument: grammar and parser, closed input space, measured fail direction, what it buys · authority moves where the pin is not looking · an outranking config file · a decoy occurrence · an npm lifecycle hook · widening a clause retires its own canary · a survived-clause canary becomes a tautology · a pin declares its normalisation · instances: `ci.image-build-delegates-the-spa-suite`, `process.hook-resolves-inputs-from-repo-root` · paths: `scripts/tests/test_image_build_delegates_the_spa_suite.py`, `scripts/tests/test_hook_fire_log.py`, `docs/guard-inventory.md`, `docs/defect-shapes-773.md` · issues: #901, #887, #891, #774, #790, #881, #773'
-mechanics: 'Two worked pins. `scripts/tests/test_image_build_delegates_the_spa_suite.py` pins command TEXT (`PINNED_STAGE_COMMANDS`), `web/package.json`''s script map (`PINNED_PACKAGE_SCRIPTS`) and `web/vite.config.ts` entire (`PINNED_VITE_CONFIG`), the last two after a SELECTION and then a partial match were defeated; its comparison runs through `_normalise_lines`, which drops blank lines and collapses whitespace within a line, and the test states that residual rather than claiming byte equality. `scripts/tests/test_hook_fire_log.py` pins the hook preamble''s two lines byte for byte (`CANONICAL_SINK_ASSIGNMENT`, `CANONICAL_SINK_SOURCE`), named once so the checker, the mutation proofs and the hooks cannot come to mean different strings. The image-build pins fail with a message naming the constant to update and asking for the reason in the same commit; the hook-preamble fault reports the divergent lines instead, since the two canonical strings ARE what a deliberate change edits.'
+mechanics: 'Two worked pins. `scripts/tests/test_image_build_delegates_the_spa_suite.py` pins command TEXT (`PINNED_STAGE_COMMANDS`), `web/package.json`''s script map (`PINNED_PACKAGE_SCRIPTS`) and `web/vite.config.ts` entire (`PINNED_VITE_CONFIG`), the last two after a SELECTION and then a partial match were defeated; its comparison runs through `_normalise_lines`, which drops blank lines and collapses whitespace within a line, and the test states that residual rather than claiming byte equality. `scripts/tests/test_hook_fire_log.py` pins the hook preamble''s two lines byte for byte (`CANONICAL_SINK_ASSIGNMENT`, `CANONICAL_SINK_SOURCE`), named once so the checker, the mutation proofs and the hooks cannot come to mean different strings. Each of the three image-build pins faults with a request for the reason in the same commit, and two of them name the CONSTANT to update (`PINNED_STAGE_COMMANDS`, `PINNED_VITE_CONFIG`) while the script-map fault names the FILE and prints both maps. The hook-preamble fault asks for neither: it reports the divergent lines, since the two canonical strings ARE what a deliberate change edits.'
 ---
 
 **The class, and what approximating it costs.** A predicate over an artifact with a grammar is a
@@ -59,9 +59,9 @@ only while the precondition that made it survive still holds.
 **Where this sits against its neighbours, so it is not read as a duplicate.** The two incidents keep
 their own records — `ci.image-build-delegates-the-spa-suite` and
 `process.hook-resolves-inputs-from-repo-root` — and this is the class they instantiate.
-`testing.guard-derives-population-from-source` ends at "when the authoritative source is missing,
-create one, never approximate it with a predicate over text"; this record answers the case that one
-does not, where the artifact IS present and authoritative and what is approximated is its GRAMMAR.
+`testing.guard-derives-population-from-source` answers the case where the authoritative source is
+MISSING — create one, never approximate it with a predicate over text — and this record answers the
+case where the artifact IS present and authoritative and what is approximated is its GRAMMAR.
 `docs/defect-shapes-773.md` §4 argues the general form. What was missing is a rule resolvable BY
 TOPIC: `docs/guard-inventory.md` carries its precedent per incident, findable only from inside one.