DIVERGE-VCR1: Verifier-Supervised Counterexample Revision

Status: completed once on 2026-08-08. The source-disjoint revision gate passed decisively; the conditional product gate failed one conjunct because generated code was 29/40 against a fixed 30/40 floor. Exact VCR1 is closed without a rescue variant.

Hypothesis

PCJ1's 9B joint judge recovered 24 answers over QPT1 but missed its fixed threshold by two answers and remained order-inconsistent. VCR1 does not add another selector. It trains one model-owned revision policy to read the problem plus both complete B1/QPT1 attempts and generate a new corrected solution. This allows recovery when both source attempts are wrong, which the whole-lineage oracle and every selector cannot do.

VCR1 is a practical multi-stage reasoning system, not yet a standalone Shohin architecture claim: its two proposal lineages are exact 4B B1/QPT1 and its revision host is exact pinned Qwen3.5-9B B1.

Runtime Boundary

The model receives one string containing:

1. the complete original task, including code tests where applicable;
2. complete Candidate A and Candidate B attempts;
3. an instruction to solve and repair rather than classify;
4. the original task repeated at the end so bounded left truncation preserves the problem.

It receives no task/benchmark identifier, gold answer, correctness bit, execution result, outcome class, or assessor field. Evaluation code passes only the question runtime field to the model.

Data

The immutable source remains the CVG1 corpus with SHA-256 45f1d66ce5e87dc2a1f4c3594bdde2bae26e9417e879d16eb4eddb228b696afe. VCR1 uses the corrected NUL-delimited PCJ1 split and binds every identity to the independently verified source bank.

Training targets are:

• the verified source candidate when exactly one lineage is correct;
• the shortest verified candidate when both are correct;
• the source-verified answer or execution-verified reference program when both are wrong.

Disagreement rows receive four deterministic A/B presentations; other rows receive one. This produces 9,655 train presentations from 5,824 source pairs: 5,108 verified-candidate, 1,253 shortest-verified-candidate, and 3,294 source-repair targets. Development and holdout remain 1,289 and 1,279 unique identities.

Frozen Fit And Evaluation

VCR1 warm-starts the exact Qwen3.5-9B B1 checkpoint. It trains the existing four-layer rank-8 LoRA owner for exactly 256 AdamW updates, batch 1, accumulation 8, context 4,096, LR 2e-5, cosine decay, train seed 2026080815, and data seed 2026080814. No backbone, head, or source checkpoint is overwritten.

Development and holdout run as independent dependency-released one-H100 jobs with greedy decoding, batch 2, maximum 768 new tokens, and seed 2026080816. Both use the same exact scorer as the source banks. Holdout passes only if all conditions hold:

• generated accuracy beats QPT1 by at least two points;
• math and science/logic each regress by at most two points versus QPT1;
• code solves at least as many examples as QPT1;
• at least one both-wrong source pair is repaired.

On the 1,279 holdout rows, QPT1 solves 471. VCR1 therefore needs at least 497 correct. A holdout failure closes exact VCR1 without prompt, LR, duration, seed, order, context, or decoding variants. Only concordant development and holdout success may open one reconstruction and score of the preserved 568-example product board.

Budget

Projected charge before launch is 3--6 H100-hours including training, both source-disjoint evaluations, and a conditional product evaluation. Current monthly balance before launch is approximately 1,591 H100-hours. No larger campaign is authorized by this gate.

Result

Training job 745618 completed all 256 updates in 00:21:34. The final checkpoint SHA-256 is 28c23825dacec511c8e5a147446a3aad60bf3c2740421db3a7086a17c3bc2f7f; the training report SHA-256 is c5b79653dd4b9a6784c1c9455316f1d9cb0270592f3befb0689e7c0f05b0b9cf.

The independent development and holdout jobs both pass every frozen gate:

Development and holdout result SHA-256 values are respectively 4d04fbc64ad416627a629be6db2bdfa3347df38374c6f84baf47ac2bcf7ae6ad and 942579931cc11b813fa7aab26ec7c61bed5521d51f8e5b9b5551a22d5957dce7. The holdout result is not selection: VCR1 exceeds the two-candidate oracle by 91 answers because it generates corrected solutions for 153 cases where both inputs were wrong.

Both passing splits release one unchanged reconstruction of the preserved 568-example product board. Product-data SHA-256 is c1ebc24bab12e79753797cd14a790d1c5c4f750348412749c9329d2b968f5c4f; its report SHA-256 is f655c9a20493d9f42e19a67880389b6edbbde31e5a2b7b63c48e2ab62eed7170. Job 745624 produces:

VCR1 improves the strongest single lineage by +9.714 macro points and 51 main-board answers, improves four of five domains, stays within one point on GSM8K, and generates 38 correct answers where both source attempts were wrong. It also loses 35 answers that at least one source candidate solved. Every product condition passes except code_at_least_30_of_40; therefore the conjunctive product decision is FAIL, despite the large aggregate gain. Product report SHA-256 is f7a6b8606505dfeb5e0821f04f56436c77ef9ce910847df472975d0f562fafbc; candidate SHA-256 is 013375c8711df7e9e691830418e5239da06d56b82ee6c5a8a4fd3edb48e9587b.

The four scientific GPU jobs consumed 1.040 H100-hours in total, below the projected 3--6 hours. Exact VCR1 receives no prompt, seed, duration, context, decoding, threshold, or code-routing rescue. Retain it as the strongest measured practical reasoning system in this campaign, while keeping the claim bounded: the runtime uses two 4B proposal lineages and a 9B reviser and is not a standalone Shohin architecture result.