# OpenAI claims GPT-5.6 Sol beats Opus 5 on ARC-AGI-3 but only with its own custom test harness

> Source: <https://the-decoder.com/openai-claims-gpt-5-6-sol-beats-opus-5-on-arc-agi-3-but-only-with-its-own-custom-test-harness/>
> Published: 2026-07-30 07:40:11+00:00

OpenAI counters Anthropic's ARC-AGI-3 record: GPT-5.6 Sol scores 38.3 percent, but only through its own API with retained reasoning and context compaction. In the official test environment, the model managed just 7.8 percent. Opus 5 hit its 30.2 percent without such aids.

The article [OpenAI claims GPT-5.6 Sol beats Opus 5 on ARC-AGI-3 but only with its own custom test harness](https://the-decoder.com/openai-claims-gpt-5-6-sol-beats-opus-5-on-arc-agi-3-but-only-with-its-own-custom-test-harness/) appeared first on [The Decoder](https://the-decoder.com).