Found by the operator reviewing **my own** shipped fix (#2823). It
belongs in this document because it is the only shape so far that every
instrument in the program reported as done.
## The defect
`clearNearDuplicateReferencesTo` was converted to resolve the
canonical's column flags, and my test proved that by supplying `column:
"shipped"`. Both production call sites in `moves.ts` gated on the
**resolved** complete lane and then passed the literal `column: "done"`.
The consumer was correct; the producer was never converted; and the
hand-supplied fixture value is exactly what hid it.
Why nothing caught it:
- the **census** counts comparisons — a value passed as an argument is
not a comparison;
- the **seam check** asks whether callers *supply* the argument — these
did, with a literal;
- the **test** supplied the interesting value itself, so it exercised
the consumer and never the producer.
And the part I would have got wrong: driving the flow end to end still
does **not** distinguish them. The consumer looks the passed column up
in the canonical's IR, finds nothing for `done` on a renamed board, and
falls through to the legacy predicate where `done` *is* terminal — right
answer, wrong reason. It only bites on a board that declares a `done`
column **without** the complete trait.
## The rule
> A differential test must vary the value the **production** code
computes, not one the test hands in.
If the fixture passes the lane name, it has tested the consumer. Who
computes that argument in production, and do they compute it or spell
it, is a separate question — and the one that was wrong here.
## Measured, so nobody builds the wrong instrument
An AST probe for call arguments shaped `{ column: "<legacy id>" }` finds
**79 sites** across `packages/`. It correctly flags the two real
`moves.ts` offenders — but most of the rest are legitimate: `set({
column: "archived" })` writing the archive state, `listTasks({ column:
"todo" })` filtering a query.
So a blocking gate on this shape needs a curated list of consumers that
interpret a column as a **role**, as opposed to storing or filtering it
— a per-consumer judgment call, not a mechanical check. **Recorded
rather than built**, and deliberately not attempted on top of five
unmerged PRs in packages I do not own.
I also verified one nearby call site that a naive version of this probe
flags and which is **not** a defect: `archive-lifecycle-2.ts:353` passes
`column: "archived"`, but that path sets `task.column = "archived"`
unconditionally, so it is passing the column the card actually reached.
Exactly what the operator's fix is about.
Docs only — no changeset.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
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