---
title: Structural terminal veto
family: constructive-reservoir
summary: Keeps the four-move search in charge unless a long simulation favors its second choice. Two independent tests still finished behind the unchanged search.
status: rejected
evidence: task-record only
reads: public
---

A safety-first way to use the family's structural planner: never let it choose
a move, only let it *object* to one, and only when two independent panels of
imagined futures agree.

<EvidenceLabel status="rejected" evidence="task-record only" reads="public" />

## The intuition

By this point in the research the pattern was established: the
[constructive planner](/approaches/constructive-reservoir/constructive-spectrum)
knows something about long-term structure, and letting it override the
four-move search damages the search. The natural response is not to abandon the
signal but to make the override rare and expensive to earn.

So: the four-move search picks the move. Its runner-up is allowed to replace it
only if a long simulation says the runner-up survives materially longer — and
only if that conclusion holds up on **two separate sets of imagined futures**,
generated from independent random streams. A conclusion that appears on one
panel and not the other is exactly the kind of noise that made earlier
overrides unstable, and the two-panel rule is designed to catch it.

The word "terminal" here means the simulation runs to the end of the game (or a
long horizon) and cares about *when the game ends*, rather than about points
collected in the next few moves.

## How it works

1. Run the unmodified full-width four-move search with five chance strata. It
   supplies the chosen column and the complete ordering of the others.
2. Take only its top two columns. If there is only one legal column, or the
   search is decisive, nothing else happens.
3. Force each of the two columns, then continue with the frozen constructive
   continuation: the inner rollout policy, deliberately *not* its
   depth-shielded outer form — over a 200-move horizon.
4. Do that on two independent panels of 127 event-stratified public chance
   streams each.
5. Replace the search's choice with the runner-up only if a fixed
   terminal-classifier gate passes independently on **both** panels.

Everything read is public. The search is never modified: with the veto disabled
the program reproduces exact four-move play.

## What happened

**Rejected.** The recorded verdict is that the aggregate fitting result trailed
plain four-move search and could not reach its gate, so no screen was opened.

There are **no retained numbers.** The status exists only as a task record;
[audit 04](/docs/exploratory/audit-04-blind-spots) §B.3 lists this source among
the thirty rejections that cannot be re-derived, with no ledger protocol, no
artifact hash and no per-game data. This page states the verdict as the
[experiment index](/docs/research/experiment-index) words it and quotes no
scores.

The wider pattern it belongs to *is* well recorded. The
[strategy landscape](/docs/strategies) collects the whole family of
conservative overrides — long-outcome vetoes, denoised-value vetoes, root
tail-risk objectives, regenerative panels, and concludes that the gates
themselves work mechanically, while the challengers behind them were "too rare,
poorly calibrated, or unstable across whole games". Its verdict is worth
reading before designing another one: *confidence gates are a safety mechanism,
not a source of new strategic information.*

<TechnicalDetails title="The technical record">

**Status: rejected; task-record only.** From the
[experiment index](/docs/research/experiment-index): "the aggregate fitting
result trailed plain D4 and could not reach its gate." No entry in the
[experiment history](/docs/research/history).

Configuration, from the source: fitting seeds from `0x3d6e4000`, 4 games;
screen seeds from `0x3d6e5000`, 8 games, never opened; 1,000-move cap; two
panels of 127 scenarios; 200-move horizon; 64 events per step; separate random
domains for panel A, panel B, reveals and visible discs. The frozen gates
required, among other things, a 99% lower bound of at least 10,000 points and
2 moves, no material loss beyond −100,000 points or −25 moves, at most a 10%
upper bound on downside, ratios of 1.10 on the fitting quartet with 3 joint
wins and 1.05 on the screen with 5 joint wins.

Note the size of the fitting stage: **four paired games**. Those same four
seeds are the ones the [D4 flow audit](/approaches/baselines-diagnostics/d4-flow)
is licensed to replay. A four-game aggregate can show that a candidate is not
promising; it cannot establish by how much.

Source: `d4-structural-terminal-veto.cpp`.

</TechnicalDetails>

## What this taught us, and what is still open

- Requiring two independent panels to agree is a sound idea and it did its job:
  a weak challenger did not reach a screen.
- A gate cannot manufacture a signal. The underlying comparison — constructive
  continuation versus four-move search on near-tied columns — is the thing that
  was not good enough, which is the same conclusion the horizon experiments
  reached.
- Nothing about the size of the shortfall is recoverable from this repository.
  Re-running it would be a new experiment needing a new lease and a new
  protocol.