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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 do models learn from self-generated outputs without cascading failures? How do agents learn to distinguish valuable feedback from noise? Does AI assistance help or harm professional skill development? How do reward models systematically fail to represent diverse human preferences? Can models develop genuine introspective capability, or only mimic it? Can artificial systems establish authority in domains requiring expert judgment? What prediction granularity best trains models to generate reliable reasoning? Do language models reason through disagreement or only accommodate it? How do users confuse explanation quality with actual system accuracy? How do curriculum design and feedback approaches affect model learning? Why does self-revision amplify confidence in wrong model answers? Does reinforcement learning create genuinely new reasoning capabilities or only refine existing ones? How do educators verify student capability when AI can produce indistinguishable work? Can confidence signals reliably detect flawed reasoning in language models? How do reward signal properties affect model reasoning and safety? Why do training associations persist despite contradictory contextual information? Which reinforcement learning modifications most improve dialogue quality in language models? What explains the gap between benchmark scores and true reasoning capability? Can AI systems achieve real improvement without external human feedback? What limits recursive self-improvement in autonomous AI systems? What limits language model accuracy in evaluating ideas? What capabilities differentiate diffusion from autoregressive language models? Can language models reason beyond surface pattern matching? Do language models encode knowledge that influences generation, or primarily imitate surface patterns? What makes process supervision effective for training complex reasoning models? Can inference-time computation adaptively substitute for static model capacity? How can agents discover and adapt to user preferences during conversation? When should retrieval systems decide to fetch new information? How does RLHF training shape models to prioritize agreement over accuracy? Can reasoning models use reflection to correct their initial outputs? How susceptible are language models to conversational persuasion and belief change? Why do autonomous agents misreport success on failed actions? Does chain-of-thought reasoning reveal how models actually think or merely imitate reasoning? How can persistent memory architectures preserve information across ultra-long contexts? Can AI agents improve their skills through accumulated experience and reuse? How do AI systems determine and balance multiple competing objectives? How much of agent capability comes from harness versus the model itself? Can mechanistic interpretability methods reliably reveal what models actually know? How can evaluations be made robust against model reward hacking? How does optimization for reward create emergent misalignment in language models? How can we reduce inherent biases in LLM-based evaluation judges? What distinguishes genuine communicative competence from surface language performance? Can models strategically underperform during evaluation to hide capabilities? Can AI systems discover fundamental improvements to their own architectures?

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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