Critical risk

Be cautious only when the board is actually in trouble — play the ordinary way on a healthy board, and switch to worst-case thinking when height, crowding, or a backlog of covered discs says the game is close to ending.

The intuition

Playing cautiously all the time is measurably bad. The risk-sensitive page records the version of that idea that was tested properly inside the reference search: it lost score, survival and flow at once. One plausible reading of that failure is that caution was applied everywhere, including on boards where there was nothing to be cautious about, so it mostly spent good moves avoiding imaginary disasters.

This lab tests the obvious repair. Leave the policy alone almost all the time, and turn on worst-case aggregation only at critical states — boards where three specific things say the game is genuinely close to ending:

• the tallest column has reached a threshold height;
• the board is crowded, or
• there is a cover backlog: more closed gray discs than the remaining drops before the rise can plausibly open, computed as covers − 1.4 × drops until the rise — the same 1.4-reveals-per-move arithmetic used across this family.

Everywhere else, the policy is the ordinary averaging one.

How it works, step by step

1. Read the public position — board, next disc, rise clock.
2. Test whether this position is critical using one of two threshold sets: an early trigger (height 5, occupancy 20, backlog 4) that fires sooner, or a late one (height 6, occupancy 24, backlog 6) that waits longer.
3. If it is not critical, choose the column by the ordinary average over sampled chance outcomes.
4. If it is critical, rank the columns instead by a blend of that average and the average of the worst 40% of their sampled outcomes, with the blend controlled by a risk weight of 0.25 or 0.5.
5. Record how often the trigger fired and how often it changed the move — separately for critical and non-critical positions.

Five profiles are played on identical paired games: a control with the trigger disabled, and early/late triggers at each of the two risk weights.

What is known, in plain English

That the experiment is designed to answer a sharper question than its predecessor did. Because the control profile is included in the same paired run, and because switch counts are recorded separately for critical and non-critical positions, a completed run would show not just whether the idea helps but how often it intervened — which is the number that the conservative-override family has repeatedly needed and repeatedly lacked.

What is not known is any of that. The run is not recorded.

The technical record

The experiment index records this as unknown, repository-verified: "no durable outcome was located." Repository-verified means the source is present and its purpose is clear from reading it; it is not a claim that a run occurred.

Repository-verified from the source: critical-risk-lab.cpp defines five profiles — control (risk weight 0), early-cvar25, early-cvar50 (height 5, occupancy 20, backlog 4.0) and late-cvar25, late-cvar50 (height 6, occupancy 24, backlog 6.0) — a fixed tail fraction of 0.4, and a root aggregate of mean × (1 − w) + CVaR × w. Screen and confirmation cohorts are eight games each, from 0x3d700500… and 0x3d700600…, at a 500-move cap. The underlying policy is the shared bounded phase-safety behaviour search; the profiles change only the root aggregation and only at states the trigger selects.

Eight games is a small cohort, and this design has five arms.

Related evidence that does exist. The strategy catalog's conservative- override section reports that gates of this kind "successfully prevented many weak policies from reaching protected tests, but the admitted switches were usually too rare, poorly calibrated, or unstable across whole games", and that "mean-only gains often hid damage to the lower tail." The nearest ledger-recorded measurement is the root-CVaR ablation described on the risk-sensitive page, which applied caution unconditionally and regressed on every measure.

What this taught us, and what is still open

• The unanswered question is a good one. "Was unconditional caution the problem, or was caution the problem?" is exactly the follow-up the recorded root-CVaR failure invites, and this program is built to answer it on paired games with a control arm.
• A completed run would still be a screen. Sixteen games across five arms cannot establish an improvement over the reference search; it can only decide whether the idea is worth a larger, preregistered comparison.
• The standing conclusion is unchanged until then. Confidence gates are a safety mechanism, not a source of strategic information. Selective caution is a cheaper hypothesis than most in this repository, and it is untested.