OpenAI says it can keep up on ARC-AGI-3. After Anthropic's Claude Opus 5 quadrupled the record score on the logic benchmark, OpenAI is now showing that GPT-5.6 Sol hits 38.3 percent with two API settings, beating Opus 5's 30.2 percent.
OpenAI isn't using the official test environment, though. Instead, it runs GPT-5.6 Sol through its own Responses API with "Retained Reasoning," which keeps the model's chain of thought between steps, and "Compaction," which summarizes old context instead of truncating it. In the official harness, GPT-5.6 Sol scored just 7.8 percent because the model's reasoning gets discarded after each action.
OpenAI argues that benchmarks never measure just the model but also the technical setup around it. That's fair, and it's precisely why ARC-AGI-3 deliberately tests pure model performance without external aids. Opus 5 hit its 30 percent under those same constraints and would likely score even higher inside Claude Code.