Can Qwen3-4B's Internal Entropy Predict Errors?
dasjomsyeet · reddit · 2026-07-13
The author tested concepts related to the Anthropic Jacobian Lens: whether J-space entropy can serve as a signal for model errors.
Research setup:
- Based on Qwen3-4B
- Approximately 11,400 samples
- Covers 7 datasets: TriviaQA, PopQA, NQ-Open, TruthfulQA, HotpotQA, GSM8K, CommonSenseQA
- The repository provides complete methods, raw data, metrics, charts, and notebooks
Main conclusions:
- It complements output confidence in some factual retrieval tasks, particularly improving error routing precision for "high-confidence but potentially wrong" answers.
- It cannot stably identify internalized misconceptions: On TruthfulQA, the internal representation might still look "clean" even when the answer is wrong.
- This signal is heavily task-dependent: For example, a threshold tuned on TriviaQA fails when transferred to GSM8K; multiple-choice formats also weaken the signal.
Overall, the author concludes that it is not a universal "hallucination detector," but rather a supplementary routing signal useful for certain types of factual errors.
Related event: Anthropic Reveals Claude's Hidden Reasoning Space: J-space(16 posts)→
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