Does reasoning_effort improve arena performance? — predeclared plan

Date: 2026-08-17 (declared BEFORE launch) Question: Does raising reasoning_effort make an LLM perform better on the desk's golden-workflow arena — and is the relationship monotonic?

Design

• Model (fixed): gpt-5-6-luna (openai/gpt-5.6-luna, zenmux route). Measured ladder (2026-08-14 probe): none, low, medium, high, xhigh, max; minimal rejected.
• Arms (4): none, low, high, max — both ends of the ladder plus the common contrast pair. One contestant per arm ((model_id, reasoning_effort) identity, migration 0058).
• Workflows (5, all current): risk-manager-control-day, high-board-portfolio-review-day, trader-rfq-booking-day, risk-limit-breach-day, ops-settlement-day. Each workflow is a paired block: every arm faces the same fixtures, truth values, and scorer.
• Trials: 2 per (workflow, arm) → 40 trials, folded per-cell by fold_trial_breakdowns. Run #107 vs #108 showed a 6.6-point swing at identical config, so single trials cannot support a conclusion.
• Jury: off (default). Objective-only scoring — deterministic.
• Route sanity (pre-launch, measured): trivial prompt at high spends 0 reasoning tokens (adaptive); a snowball-payoff question spends 0 at none (answer muddled) vs 1,034 at high (answer correct). The knob is live on this route.

Predeclared metrics

1. Primary: objective score (%) per (workflow, arm) cell, compared across arms paired by workflow. Hypothesis under test: score is non-decreasing in effort.
2. Secondary: ability-card axes (GRD/ADH/SYN/PRC/EFF, OVR), tool calls per trial, per-cell trial stdev (consistency), error counts, wall-clock per trial (match timestamps + transcript timing), reasoning/completion token spend where recorded.
3. Mechanism: per-check pass-rate tally across arms (the validity-audit instrument) to locate WHERE effort helps or hurts (grounding vs adherence vs synthesis vs procedural vs efficiency).

Predeclared validity rules

• Trials that die infra (invalid, _is_infra_blank / infra-contaminated) are excluded; a cell with 0 clean trials is reported missing, never imputed.
• If more than ~20% of trials are infra-dead, stop and --resume rather than conclude from a swept board.
• This board is pinned-effort and therefore not comparable to historical boards (#8–#104) on EFF/CON; all comparisons are within-board.
• Arms run sequentially in one process, so arm order is confounded with time-of-day/provider load; we report per-trial timing so a drift would be visible, and we do not interpret sub-point score differences.
• n = 5 workflow blocks × 2 trials. We report signs and means of paired differences; no significance theater beyond what n supports.

Cost accounting (predeclared as a first-class result)

Higher effort that buys +1 point at 3× wall-clock and token cost is a finding, not a footnote. Cost per arm is reported beside score.