CB-WP-0019-T05: what the meta budget is for, at 80/20

InnerLoop v1.7. The purpose is written first and the number follows from
it: most spend on the task at hand, some on control, review and
improving the process. make status prints it above the figure, because a
threshold with no stated purpose is what let this number be argued three
times.

Soft 20% over a trailing 5, and the self-test enforces that the ratio and
the window are a PAIR: META_SOFT_PCT == 100 / TRAILING_PASSES. One meta
pass among n at parity cost reads 1/n, so 80/20 is one pass in five at
normal cost -- a five-pass window. The same 20% over three would have
silently also demanded the meta pass be half-price, which makes meta work
rushed rather than rare. Moving the ratio without the window goes red.

The phase setting is declared, argued and expiring in gates.toml, and
reverts on review_by unless re-argued. Verified live at 35%. One with no
reason or no expiry is refused rather than honoured, because a threshold
anyone may move is not a threshold.

Measured: the last five passes read 7% against the new line.

InnerLoop.md crossed the 400-line limit three times while this was
written and was fixed structurally each time -- the arithmetic, the
cost-per-response basis and the two review case studies moved to
InnerLoopReference.md. The limit was not raised.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

specs/InnerLoopReference.md

@@ -227,3 +227,73 @@ So window 2 carries a falsifier: **if it produces no override at all, that
 is evidence the rate went too far**, not evidence the mechanism is
 healthy. A window that cannot fire cannot be evaluated, which is the exact
 failure d10 had.
+
+## Meta budget — why 20% goes with a five-pass window
+
+*(CB-WP-0019 T05, 2026-08-03, at the maintainer's instruction: "the main
+budget should be spent on the task at hand while some of the budget should
+be spent on control, review and improvement… 80/20 to start with".)*
+
+The ratio and the window are a pair. With one meta pass among `n` at the
+same cost `P` as each product pass, the measured share is `P / (n·P)`, so:
+
+| window | one meta pass at parity reads | what a 20% line then demands |
+|---:|---:|---|
+| 3 | 33% | the meta pass must cost **half** a product pass |
+| 4 | 25% | ~80% of one |
+| **5** | **20%** | **parity — one pass in five, normal cost** |
+| 6 | 17% | 20% is slack |
+
+So 80/20 over a **trailing 5** is the literal reading of the instruction:
+one pass in five is meta, and it may cost what a pass costs. The same 20%
+over a trailing 3 would silently also require it to be half-price, which
+does not make meta work rarer — it makes it rushed, and this project's
+meta passes are where its instruments get repaired.
+
+**Why not simply keep 25% over three?** Because 25% over three is *"one in
+four at three-quarters cost"*, which is a ratio nobody chose; it was
+inherited from ADR-0006 without the window being considered alongside it.
+Stating the pair is the correction.
+
+**The phase setting.** `meta_phase` in `gates.toml` carries `pct`,
+`reason`, and `review_by`. It exists because stage 0 and a stabilisation
+phase do not deserve the same ratio — but it expires, because a threshold
+anyone may move is not a threshold. The failure it guards against is the
+one this project has refused four times: raising a limit to pass a breach
+rather than fixing the breach.
+
+## Loop work cashes out — the measured basis
+
+*(ADR-0006 D4, moved out of `InnerLoop.md` by CB-WP-0019 T05 when that file
+crossed the loadability limit. Limits get fixed structurally here.)*
+
+Cost per response across five passes ran **0.123, 0.228, 0.362, 0.298,
+0.123** dollars. The reading that survived the data is that **cost tracks
+distance from a runnable check**: the passes that shipped a command were
+cheap; the passes that argued about what a number means were not
+(CB-EV-0007 §5).
+
+**Refuted if** a prose-only meta pass lowers cost per response, or catches
+a class no command could.
+
+## Why review is adversarial execution, not re-derivation
+
+*(Moved out of `InnerLoop.md` by CB-WP-0019 T05 at the loadability limit.
+Two cases, three passes apart, with the same shape.)*
+
+**v1.1, from CB-WP-0002 — the same-sample blind spot (SSB).** The dedup
+invariant was verified on the main transcript by the survey (206/206
+groups) and independently re-verified by the reviewer, who used the same
+transcript. It is **false** in the 8-response `subagents/` tree neither
+examined. Two independent checks, one blind spot, because both sampled the
+same way. Only an assertion running over all the data at execution time
+caught it.
+
+**v1.4, from CB-WP-0005 — re-derivation is not enough.**
+`evidence/CB-EV-0001` reported `AM-7 replay | met, 2,290×` for a clause
+that asserts nothing: the hash reaches only a `println!`. The reviewer
+found it by opening a test out of curiosity and said so; **no systematic
+step pointed there.** Mutating it settled it in one command.
+
+Both are verification steps that inherited the author's blindness, and
+both fixes replace re-derivation with **adversarial execution**.