Precise Debugging Benchmark: Is Your Model Debugging or Regenerating?

Hugging Face Daily Papers Papers

Summary

This paper introduces the Precise Debugging Benchmark (PDB), a framework that evaluates LLMs on precise fault localization rather than just test pass rates. Results show frontier models like GPT-4.1-Codex and DeepSeek-V3.2-Thinking pass 76%+ of unit tests but achieve less than 45% edit precision, revealing a critical gap between code regeneration and true debugging.

Unlike code completion, debugging requires localizing faults and applying targeted edits. We observe that frontier LLMs often regenerate correct but over-edited solutions during debugging. To evaluate how far LLMs are from precise debugging, we introduce the Precise Debugging Benchmark (PDB) framework, which automatically converts any coding dataset into a debugging benchmark with precision-aware evaluation. PDB generates buggy programs by synthesizing verified atomic bugs and composing them into multi-bug programs. We define two novel metrics, edit-level precision and bug-level recall, which measures how many necessary edits are made and how many bugs are resolved. We release two evaluation benchmarks: PDB-Single-Hard on single-line bugs, and PDB-Multi on multi-line bugs. Experiments show that frontier models, such as GPT-5.1-Codex and DeepSeek-V3.2-Thinking, achieve unit-test pass rates above 76% but exhibit precision below 45%, even when explicitly instructed to perform minimal debugging. Finally, we show that iterative and agentic debugging strategies do not substantially improve precision or recall, highlighting the need to rethink post-training pipelines for coding models.
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Source: https://huggingface.co/papers/2604.17338

Abstract

Frontier LLMs demonstrate high test pass rates but poor precision in debugging tasks, indicating a gap between functional correctness and precise fault localization.

Unlike code completion, debugging requires localizing faults and applying targeted edits. We observe that frontier LLMs often regenerate correct but over-edited solutions during debugging. To evaluate how far LLMs are from precise debugging, we introduce thePrecise Debugging Benchmark(PDB) framework, which automatically converts any coding dataset into a debugging benchmark with precision-aware evaluation. PDB generates buggy programs by synthesizing verifiedatomic bugsand composing them into multi-bug programs. We define two novel metrics,edit-level precisionandbug-level recall, which measures how many necessary edits are made and how many bugs are resolved. We release two evaluation benchmarks: PDB-Single-Hard on single-line bugs, and PDB-Multi on multi-line bugs. Experiments show that frontier models, such as GPT-5.1-Codex and DeepSeek-V3.2-Thinking, achieve unit-test pass rates above 76% but exhibit precision below 45%, even when explicitly instructed to perform minimal debugging. Finally, we show that iterative andagentic debuggingstrategies do not substantially improve precision or recall, highlighting the need to rethink post-training pipelines for coding models.

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#### Precise-Debugging-Benchmarking/PDB-Multi Viewer• Updatedabout 4 hours ago • 256 • 42 #### Precise-Debugging-Benchmarking/PDB-Single-Hard Viewer• Updatedabout 4 hours ago • 5.75k • 38 #### Precise-Debugging-Benchmarking/PDB-Single Viewer• Updatedabout 4 hours ago • 7.59k • 32

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