text2cypher_lora_v6_shaped

Overnight experiment, 2026-08-25/26: GRPO on top of BeastxD/text2cypher_lora_v7, using a shaped, partial-credit reward instead of the binary +1/0/-0.5 reward the first GRPO attempt (BeastxD/text2cypher_lora_v6_grpo) used.

Result — a real improvement in signal, not yet a statistically confirmed win

comparison	execution accuracy	delta	McNemar p	verdict
v7 → v6_shaped, Neo4j 2024v1	55.66% → 56.84%	+1.18pp	0.0890	not significant (p<0.05)
v6_grpo (binary) → v6_shaped	56.21% → 56.78%	+0.57pp	0.3100	not significant

Do not read this as "shaped reward beats v7" — p=0.089 does not clear the 0.05 bar this project uses everywhere else. What is worth reading into it: the original binary-reward run scored p=0.42 against v7 after 1,201 steps. This run reached p=0.089 after only 782 steps (65% as much training, from an earlier checkpoint-600, not even its own final state). That is a materially stronger signal on less compute, which is evidence in favor of running the shaped reward longer -- not proof it already works.

Why a shaped reward

The binary reward gives an identical 0.0 to every wrong-but-executing rollout, regardless of how close it is. GRPO only learns from within-group variance, so two rollouts that are both wrong in different ways score the same and produce zero gradient. Measured on the original run: usable-groups-per-step decayed 1.35 → 0.85 over its lifetime, and held-out accuracy never moved (p=0.42).

+1.0     exact result-set match (unchanged)
0.8×J    wrong, J = Jaccard overlap between predicted and gold result multisets
-0.5     execution error (unchanged)

See v6/code/grpo_reward_shaped.py for the implementation and validation.

What this run actually did

Fresh from v7 (not resumed from the binary run, to isolate reward as the only variable). Self-limiting deadline (timezone for when results were needed was unknown), stopped after 782 steps / ~2h of training -- short of the 5,311-step epoch and short of the original run's 1,201 steps. frac_reward_zero_std still rose over the run (0.320 → 0.480), similar in shape to the binary run, so the shaping did not eliminate the flat-group problem -- it appears to have made the non-flat groups more informative instead.

This is a partial run merging an early checkpoint (step 600 of 782 reached). A longer, properly-scheduled continuation is the natural next step, not a verdict on the method.

Usage

Same prompt/pruning contract as v7 and v6_grpo -- v7's ~618-char system prompt with exact-match schema pruning.