## What
Continuing the #2979 discipline — probe a ratchet with shapes its author
did *not* have in mind — applied to my own inert-seam gate. Four probes,
three got through. Two turned out to be the sibling gate's job. This is
the one that's nobody's:
```ts
resolveSomething("KB-1", undefined)
```
The seam is a trailing optional parameter, so the gate asked how many
**arguments** a call site passes. Spelling the omission out satisfies
that count while the callee receives exactly what it received before:
nothing. The parameter is still inert, the board still reads the legacy
vocabulary — the gate just stops saying so.
Not an exotic spelling. It's what a partial wiring-up produces when
flags are threaded through an intermediate that has none to pass, and
what a mechanical positional edit produces when it fills argument slots.
## Missed by both gates — checked before touching anything
`check-lane-wiring` (#2966) covers the default-valued and options-object
shapes this gate is structurally blind to. I probed it first, and it
caught **both**, so the two remain genuinely complementary rather than
overlapping. But it counts arguments the same way here, so this shape
was uncovered by either.
| probe | inert-seam (before) | lane-wiring |
|---|---|---|
| omitted entirely | caught | — |
| default-valued param | missed | **caught** |
| options-object flags | missed | **caught** |
| explicit `undefined` | missed | **missed** ← this PR |
## The trim is trailing-only
A **middle** `undefined` still positions the arguments after it, so
those are real answers. That's the case that keeps the trim honest, and
it's pinned as a test.
## Measured
| check | result |
|---|---|
| clean `main` | exit 0, unchanged |
| now caught | explicit `undefined` · `void 0` · several trailing
undefineds |
| correctly **not** flagged | a real trailing value · a middle
`undefined` with a real value after it |
| gate's own suite | **12 → 18 tests**, all green |
| reverting to the raw argument count | fails **exactly** the 3
positives; the negatives hold |
## One note on the fourth gate
`check-fnxc-future-dates` went red on this branch — on my own comments.
I'd stamped them `2026-07-31`, which is tomorrow. Fixed by correcting
the stamps to today, not by re-recording the baseline; the baseline
already tolerates some pre-existing future stamps and adding mine to it
would have been appeasement. Worth noting that the gate earned its keep
against the person who has been writing the other gates.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
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