The prior measurement (docs/2026-09-08-blindsone-below-k-k2.md SS 3) found that
the budget, not the ranking, is the second lock on a mandate-shaped cost
question -- and that the same mechanism was a REGRESSION on the question that
works: raising `--k` to 16 evicted the gold concept, because the exact knapsack
maximises a SUM of fused scores and has no opinion about rank, so twenty small
excerpts out-value one that costs 56.5 % of the budget.
Measured here on the same 629-concept bundle, with the three known-positive
figures from `4c699fd` reproduced first:
- Corpus distribution, denominator 629: median excerpt 857 B, max 223 391 B,
3 concepts over the limit alone.
- Candidate rule (b), a corpus-derived budget, is FALSIFIED by two numbers: two
defensible derivations are 49x apart on the same corpus, the small one turns
the gold concept into `over_budget_alone` (13 refusals against 2), the large
one changes nothing at the default k. A budget is the consumer's constraint,
not a property of the corpus; `--limit` already belongs to the caller.
- Built instead, behind `--reserve-top-rank` (default OFF): the top-ranked
candidate gets its bytes before the pack runs, AFTER the `over_budget_alone`
pre-exclusion and never before, and the payload declares `budget.reserved`.
- It fixes the eviction: k=16 and k=24 deliver the gold concept at rank 1,
costing one and two excerpts, and 20.4 % / 27.3 % FEWER o200k tokens.
- It changes the delivered list in 2 of 24 measured combinations -- both of them
that eviction. In the other 22 the list, its order and `spent` are identical.
- It does NOT close the mandate-shaped blind spot: that concept ranks 10, not 1.
The one delivering command is `--cost-vocabulary --k 12 --limit 160000`
(62 149 tokens against 58 401), and that is a consumer's decision.
11 new tests (RED first), 7 mutations 7 red with an unmutated negative control
green before and after; two of the seven survived the first test set and the
tests were strengthened. Default payload byte-identical, both goldens unchanged.
Report: docs/2026-09-08-blindsone-laas2-budsjett-k2.md
Suite 1279 green, mypy --strict clean over 28 files, ruff clean.
Co-Authored-By: Claude <claude-opus-5>
Kjell Tore Guttormsen
6776c37d23