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Can models learn to evaluate their own work during training?

Explores whether language models can internalize reward function computation as part of training, transforming external feedback into internal self-assessment capability without slowing inference.

Synthesis note · 2026-02-23 · sourced from Novel Architectures

Current training paradigms terminate learning at the end-of-sequence token, wasting the entire sequence space after model output completion. Post-Completion Learning (PCL) systematically exploits this neglected space. A temporary termination marker (<-- post-completion -->) creates a "post-thinking" space where models continue generating self-assessments and reward predictions during training, while inference stops at the marker — zero additional cost at deployment.

The core innovation is white-box reinforcement learning: the model explicitly learns to understand and compute reward functions, internalizing the reward model as its own evaluation capability. This transforms the model from "passive reward acceptance" (external reward signal tells it what's good) to "active self-evaluation" (it learns to compute quality assessments itself).

Implementation uses dual-track SFT: one track optimizes reasoning, the other optimizes evaluation capability. These are mixed with RL training for multi-objective hybrid optimization. The model learns both to solve problems and to assess its own solutions — but critically, only the problem-solving capability is active during inference. The self-evaluation is internalized during training, shaping the model's generation without requiring explicit self-assessment at inference time.

This addresses three limitations simultaneously:

  1. SFT's passive learning — models learn to mimic demonstrations without developing self-assessment ability
  2. RL's external dependency — reward models are opaque external components; PCL internalizes the evaluation
  3. Self-correction's inference cost — methods like Self-Refine require additional generation passes; PCL's self-evaluation is absorbed into training

The parallel with human cognition is direct: "Humans, after completing a task, often engage in self-reflection and quality assessment — this post-thinking process is crucial for improving future performance." PCL operationalizes this for LLMs.

This connects to What limits how much models can improve themselves? — PCL attempts to close the gap by training the verifier and generator as the same model, with the verification capability internalized rather than external. It also complements Does reflection in reasoning models actually correct errors? — PCL's self-evaluation is trained against ground-truth reward functions, not against the model's own prior outputs, potentially avoiding the confirmatory pattern.

Inquiring lines that read this note 132

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What are the consequences of models training on synthetic data? Why do reward structures fail to shape long-term agent learning? How do training priors constrain what context information can override? How do aggregate reward models systematically exclude minority user preferences? How do evaluation biases undermine LLM quality assessment systems? Does AI fluency substitute for verifiable accuracy in human judgment? How does AI adoption affect human skill development and labor equality? Can alternative training methods improve on supervised fine-tuning for language models? Can next-token prediction alone produce genuine language understanding? Why do language models reinforce false assumptions instead of correcting them? How do we evaluate AI systems when user perception misleads actual performance? How do self-generated feedback mechanisms enable effective model learning? Why does self-revision increase model confidence while degrading accuracy? What pretraining choices and baseline capability constrain reinforcement learning gains? Does self-reflection enable models to reliably correct their errors? Can model confidence signals reliably improve reasoning quality and calibration? What properties determine whether reward signals teach genuine reasoning? Can single-axis benchmarks accurately predict agent deployment success? Does conversational format create illusions of genuine AI communication? How does objective evolution guide discovery better than fixed planning? How do language models inherit human biases from training data? How do transformer attention mechanisms implement memory and algorithmic functions? Do language models develop causal world models or rely on statistical patterns? Which computational strategies best support reasoning in language models? Can self-supervised signals enable process supervision without human annotation? How should inference compute be adaptively allocated based on prompt difficulty? How should conversational agents balance goal-driven initiative with user control? How should iterative research systems allocate reasoning per search step? Does reinforcement learning teach reasoning or just when to reason? What makes weaker teacher models effective for stronger student training? Do language models learn genuine linguistic structure or just surface patterns? Can ensemble evaluation methods reduce bias more than single judges? Why do agents confidently report success despite actually failing tasks? How can AI agents autonomously learn and transfer skills across tasks? How can process reward models supervise complex reasoning traces? Is model self-awareness based on genuine introspection or pattern matching? What capability tradeoffs emerge when scaling model reasoning abilities? What constrains reinforcement learning's ability to expand model reasoning? How does example difficulty affect learning efficiency in language models? Does externalizing cognitive work and state improve agent reliability? What memory architectures best support persistent reasoning across extended interactions? How can identical external performance mask different internal representations? Can language model RL training avoid reward hacking and misalignment?

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Original note title

post-completion learning uses the ignored post-eos space to internalize self-evaluation during training with zero inference cost