clay-borg/decisions/ADR-0008-instrument-corrections.md

# ADR-0008: retire SH-3 as a gate; correct AM-4a to count what ships

status: accepted
date: 2026-08-02
decided by: agent, under the standing loop authorization. One item is
reserved for the maintainer — see §Reserved.
tier: M (structural M — changes how the loop constrains its own operation:
a gate floor and a budget instrument, InnerLoop v1.6 / ADR-0006 D5;
chaos d4=3 → no override). Tier M merges survey and ADR into one document,
which this is; the adversarial review is optional and was not run.
references: [CB-WP-0013](../workplans/CB-WP-0013-instrument-corrections.md),
[SessionShape.md](../specs/SessionShape.md) §4,
[ADR-0006](ADR-0006-adaptive-control-gates.md) D1/D2/D4,
[ADR-0007](ADR-0007-render-html-not-a-port.md) D4,
[CB-EV-0010](../evidence/CB-EV-0010-render-port.md) §5

## Context

Two instruments were found wrong by the passes that used them. Neither
error was in the direction that flattered us, and one of them has been
producing a standing breach report for seven passes.

---

## Decision 1 — SH-3 is retired as a gate and kept as a diagnostic

### The survey: three defects, each deeper than the last

**First (CB-WP-0013 T01): the sample.** `--shape-budget` windows since the
last commit and is read while writing the evidence file — right after a
commit, when the window holds one or two responses. SH-1/SH-2 are location
statistics and survive that. SH-3 is a rate; at n=2 its only values are
0%, 50%, 100%. Six evidence files quoted the resulting `0.0%` as a
measurement. Fixed: below a derived minimum of 14 the tool now prints
`insufficient sample` and no verdict.

**Second: the claimed decline was also an artifact.** This workplan's own
Purpose stated that batching *"has got worse"* — pinned history 7.8–8.6%
against per-pass windows of 1.1–6.3%. **That was wrong**, and by the same
class of error it was written to correct. The two figures come from
differently-placed windows, not from different behaviour. Withdrawn.

**Third, and the one that decides this: the window and the metric are
systematically anti-correlated.** Measured, by re-deriving batching
independently of `cb-cost` from the raw transcripts:

| window | responses with tools | batched | rate |
|---|---:|---:|---:|
| CB-WP-0011 pass | 54 | 0 | **0.0%** |
| gap → next declaration | 16 | 6 | **37.5%** |
| CB-WP-0012 pass | 86 | 0 | **0.0%** |
| gap → next declaration | 10 | 1 | **10.0%** |
| CB-WP-0013 so far | 10 | 0 | **0.0%** |

**Zero batched turns in 150 in-pass responses across three passes, and
37.5% in the gap between two of them** — comfortably above the 20% floor.

The cause is not discipline. Batching requires two tool calls whose inputs
are both known at once. Orientation and survey work is full of those: read
four files, run three probes. Implementation has almost none, because each
step consumes the previous step's result — read, edit, test, read the
failure, fix. **So SH-3 measures what kind of work is happening.**

And SH-3's window is *since the last commit*, which during a pass is
always in-pass work. **The metric is structurally incapable of reading
above ~0% in the window it is gated on.** It is not a strict gate — it can
only be met by not working.

### The decision

**SH-3 stops being a gate.** The 20% floor and the `[SOFT]` verdict are
removed. `cb-cost` continues to report the batching rate as a diagnostic,
over the whole session, where it reads 5.8% (57 batched of 984 responses
with tool calls).

Four reasons, strongest first:

1. **It cannot report what it gates on.** §above. A floor that the
   measurement window structurally excludes is not a target.
2. **It measures composition, not waste.** Penalising an implementation
   pass for not batching penalises it for being an implementation pass.
3. **Its own spec bounds its value.** `specs/SessionShape.md` §4:
   *"eliminating every avoidable single-call turn would remove at most a
   few percent of turns, worth roughly $2–4 on a $93 pass"*, and *"batch
   because it is free, not because it is the lever."* It also calls SH-3
   *"the least valuable"* of the three.
4. **Seven passes, seven breach reports, zero actions.** ADR-0006 D4:
   rituals cash out or go.

### This is not retargeting to match the measurement

`specs/SessionShape.md` forbids that explicitly, and CB-WP-0003 T07 exists
to prevent it, so the distinction has to be stated rather than assumed:

- **Retargeting** would be moving the floor from 20% to 6% because 6% is
  what we measure. That is not done and is still forbidden.
- **This** removes the gate on the argument that the *quantity* does not
  deserve one — established before the disposition, from the window
  structure and from the spec's own valuation.

And the obvious objection — *retiring a metric right when it shows a
regression looks like burying it* — is answered by the second defect: the
regression was an artifact of window placement and has been withdrawn.
There is no established decline to bury. The number is still reported;
only the verdict is gone.

## Decision 2 — AM-4a counts `--edges normal,no-proc-macro`

ADR-0007 D4, owed. AM-4a's figure includes proc-macro crates that run in
the compiler and never reach a binary: **89,048 lines, 36.2%** of the
shipped-runtime figure, `syn` alone 66,916.

`tools/dep-weight.py` measures `--edges normal,no-proc-macro` for the
shipped-runtime configuration.

## Decision 3 — the target moves down with the instrument

Correcting the metric from 246,250 to 157,202 while leaving the target at
250,000 would hand this project **89,048 lines of headroom it did not
earn**, in the same commit that reveals the error. That is the shape of
change this repo has twice refused, and refusing it here costs nothing:

> **AM-4a's shipped-runtime target moves from 250,000 to 161,000.**

161,000 preserves the *ratio* the ratified target expressed — 250,000 was
set against a 246,250 measurement, i.e. ~1.5% of headroom; 161,000 against
157,202 is ~2.4%. Rounding to a round number slightly *above* strict
proportionality is deliberate and is the only place this decision gives
anything back, because a target that leaves 1.5% of room is a target that
fails on a dependency's patch release.

**AM-4b (dev-toolchain) is left alone**, at 350,000 against a 317,021
measurement. It is not corrected in this pass because its proc-macro share
has not been measured, and correcting a second instrument on the strength
of the first one's ratio is exactly the error this ADR exists to fix.
Filed as owed.

## Reserved for the maintainer

**AM-4a still cannot survive INTENT stage 2**, and this decision makes that
worse rather than better. `wgpu` + `winit` is 1,741,979 marginal lines
against a target now proposed at 161,000 — **10.8×**, up from 7×. ADR-0007
raised it; nothing here settles it. The correction below is honest
book-keeping, not headroom for stage 2, and it should not be read as
having made the stage-2 problem smaller.

## Consequences

- One fewer gate, and the gate registry gets its first retirement. That is
  also **`GATE-REVIEW`'s first `caught` entry** — the registry's
  `retire_if` says it must have *"retired, tightened, or forced the
  re-justification of"* something by its review date, and it now has.
- Every AM-4a figure in this repo's history overstates the load by 36%.
  Those documents are history and are not rewritten; the correction lives
  in `specs/GameKernel.md` §4 and here.
- The batching diagnostic stays visible, so if in-pass batching ever
  becomes possible the number will show it without a gate having to be
  re-litigated first.