Code Correctness Is Linearly Decodable from LLM Hidden States Before Generation
Large language models encode rich information in their hidden states. This work asks whether the correctness of code that Qwen3-4B-Instruct-2507 has not yet generated is already legible in its hidden states, evaluated on a set of 444 tasks from LiveCodeBench. The correctness of the model's first-attempt code is linearly decodable from the hidden state at the final prompt token, captured before any output token is generated, with a leakage-free held-out AUC of 0.881 +/- 0.008 across 50 outer splits. To assess whether this signal is explained by prompt length, each hidden state dimension is residualized with respect to its linear effect. The probe still achieves an AUC of 0.842 +/- 0.010, s...
| Authors | Carlo Di Cicco |
|---|---|
| Primary category | cs.LG |
| Published | 12 June 2026 |
| Last updated at source | 16 July 2026 |
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