SWE-bench Verified Contaminated: OpenAI Stops Reporting After Finding All Frontier Models Trained on Dataset

Morph LLM·high signal

OpenAI has stopped reporting SWE-bench Verified scores after confirming training data contamination across every frontier model. Claude Mythos Preview leads Verified at 93.9% but on the uncontaminated SWE-bench Pro benchmark, the best score drops to 57% (GPT-5.3-Codex) and 45.9% (Claude Opus 4.5 under SEAL standardized scaffolding). The 35-point gap between Verified and Pro scores exposes how contamination inflated the primary coding agent benchmark — SWE-bench Pro is now the reliable measure of actual agent coding capability.