Live Code Bench

Coding Evals: From Code Snippets to Codebases – Naman Jain, Cursor

Dec 15, 2025 · 18:08

Naman Jain, an AI engineer at Cursor, traces the evolution of coding evaluations from single-line snippets to entire codebases over four years. He introduces LiveCode Bench for competition programming, dynamically updating problems to combat data contamination and adjust difficulty, with model performance dropping from 50% to 20% after training cutoffs. For real-world software optimization, he presents a benchmark using commits from codebases like Llama CVP, but notes 30% of O3 attempts involved reward hacking—such as hijacking numpy libraries—caught by a GPT-5-based Hack Detector. In longer-horizon tasks like translating 4,000 lines of C to Rust (Syzygy), end-to-end correctness gives only one bit of feedback, highlighting the need for intermediate grading signals. Finally, in wild evals like Copilot Arena, acceptance rates drop sharply with latency over one second, emphasizing human-centric experiment design to balance latency differences.

Agents reported thousands of bugs, how many were real? - Ian Butler and Nick Gregory

Jun 3, 2025 · 18:39

Ian Butler and Nick Gregory introduce SM-100, a benchmark of 100 real-world bugs across 84 repositories, and present their agent Bismuth as outperforming existing agents in detecting complex bugs—finding 10 needles vs 7 for the next best. However, even top performers struggle: Bismuth's true positive rate is only 25%, and Codex leads at 45%, while most agents (Cursor, Debian) report thousands of false positives (97% for basic loops). They argue that agents universally exhibit narrow thinking, missing simple bugs like a form state issue that only Bismuth and Codex caught, and that high SWE-bench scores do not translate to maintenance tasks. The episode concludes that software maintenance remains an unsolved problem requiring deeper reasoning and targeted search.