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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 156

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How effectively can models learn from their own generated feedback? Can agents actually improve through deployment and real-world feedback? What interface and interaction patterns preserve skill development in AI-assisted learning? How can reward models better represent diverse individual human preferences? How do external feedback and self-assessment affect model improvement? Can users accurately assess AI output quality despite polished presentation? Does AI assistance help professionals develop and retain expertise over time? Do reasoning tokens exhibit diminishing returns beyond a critical computational threshold? Can language models develop genuine communicative grounding through interaction? What drives generalization in language models beyond scale and training data? Why does self-revision in reasoning models increase confidence while degrading accuracy? Does pretraining quality determine the ceiling for reinforcement learning gains? Why do model confidence signals often mislead users about accuracy? How do spurious reward signals influence model reasoning and behavior? Do benchmark improvements actually reflect real capability gains? How do granular vs. aggregate reward signals affect model learning and output? Does AI creativity constitute genuine novelty or sophisticated pattern recombination? How does recursive self-improvement manifest and scale in AI systems? Can language models genuinely understand human psychology beyond surface pattern matching? How vulnerable are language models to adopting false beliefs in conversation? Why does semantic similarity diverge from task relevance in vector search? Do language models build internal models or rely on surface patterns? Does encoded knowledge in language models actually influence their outputs? How can process supervision better guide reasoning than outcome rewards? How should test-time compute allocation adapt based on problem difficulty? How can conversational agents move from purely reactive responses to proactive engagement? How should information retrieval adapt across different multi-step reasoning needs? What does reinforcement learning actually teach models about reasoning? How does RLHF training affect model truthfulness and accuracy? Can language models access genuine introspection or only mimic self-awareness? Can AI systems autonomously determine and refine their own research objectives? Can evaluation metrics recognize meaningful disagreement as signal rather than noise? Does awareness of evaluation change what models reveal about themselves? What causes models to develop emergent misalignment during training? Does chain-of-thought reasoning faithfully reveal how models actually think and decide? What enables language models to handle ultra-long contexts reliably? Can benchmark improvements mask actual reasoning quality degradation? How much does harness optimization versus model scaling drive capability improvements? Do models verbalize the knowledge that actually influences their outputs? How can we detect and prevent model reward hacking? What systematic biases affect LLM-based evaluation systems? How can we distinguish genuine understanding from correct outputs in language models? How do fine-tuning and retrieval trade efficiency against capability gains? Can models learn to intentionally hide their true capabilities?

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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