Teacher-Free Self-Training Amplifies but Does Not Compound: A Pass@K Crossover on a Free-Verifier Domain
On the map: Synthetic data and self-improvement for LLMs → Self-rewarding alignment and self-training
Abstract (arXiv)
When a language model trains on its own verified outputs, does it acquire capability beyond its base, or merely get better at expressing capability the base already had? We make the question decidable with a teacher-free "constellation" -- a generator, a learned critic, and a free exact verifier -- on a FlashFill-style "trapdoor" DSL, where verified (problem, solution) pairs are cheap to synthesize, hard to invert, and free to check exactly. Everything runs on one 4-bit Qwen3-4B on a single 24 GB GPU, with no model in the loop larger than the base. We report three findings. (i) Critic-guided selection beats verifier-filtered best-of-k by +9.1 pp (6/6 seeds), with the entire gain localized to tasks where candidates disagree on held-out inputs. (ii) Per-round STaR self-training raises the ceiling but never accelerates -- the gain tracks remaining headroom and decelerates across K=4 independent training trajectories. (iii) The domain has no clean zero-capability frontier, so the usual "0% → climb = emergence" test is invalid here. A measured pass@K crossover settles the diagnosis: the trained model wins at the operating budget (pass@8) but the base overtakes it at a large budget (pass@64) on every trajectory, so self-training concentrates probability mass rather than expanding reach. This is amplification, not compounding. (K=4 is indicative, not yet a robust across-trajectory CI.)
Key facts. Cited by 4 papers in the map (data through 14 Oct 2026). Placed in Self-rewarding alignment and self-training, one of 13 directions in Synthetic data and self-improvement for LLMs. Builds on 10 of its 14 references that are in the map. First posted on arXiv 5 Jun 2026.
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10 of 14 references.
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Other references · 9
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- 2025Jointly Reinforcing Diversity and Quality in Language Model Generationscited by 80
- 2025Weight Ensembling Improves Reasoning in Language Modelscited by 38
- 2025Differential Smoothing Mitigates Sharpening and Improves LLM Reasoningcited by 22
Built on by
Citing papers per year: 2026: 4.
4 papers.
- 2026The Verifier is the Curriculum: Precision Sets the Return on Search in Code Self-Distillationcited by 3
- 2026Phantom Gains: Auditing Self-Improvement Against a Measured Nullcited by 2
- 2026When Correct Solutions Repeat: Rarity-Aware Credit Redistribution for GRPOcited by 1
- 2026RLVR is a Kernel, Not a Function: Statistical Inference for pass@k Crossoverscited by 1
- 2026RLVR is a Kernel, Not a Function: Statistical Inference for pass@k Crossovers18 Sep 2026
- 2026Phantom Gains: Auditing Self-Improvement Against a Measured Null20 Aug 2026
- 2026When Correct Solutions Repeat: Rarity-Aware Credit Redistribution for GRPO4 Aug 2026
- 2026The Verifier is the Curriculum: Precision Sets the Return on Search in Code Self-Distillation23 Jun 2026
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- 2026Proof-Carrying Cognition: Closing the Verification Gap with Reality-Settled Reward
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- 2026Improving Few-Step Language Flows with Untied Self-Conditioning