# Claude Opus 5.5 vs O3

As of Oct 15, 2026, Claude Opus 5.5 leads O3 in 6 of 6 shared categories: General LLM, Reasoning, Science, Long context, Factuality, and Abstraction (ARC).

Claude Opus 5.5: $8.000000000000002 per 1M blended tokens.

O3: $3.5 per 1M blended tokens.

Claude Opus 5.5: closed weights.

O3: closed weights.

- Which to pick, General LLM: As of Oct 15, 2026, Claude Opus 5.5 leads O3 in General LLM at #2 against #78.
- Which to pick, Reasoning: As of Oct 15, 2026, Claude Opus 5.5 leads O3 in Reasoning at #1 against #90.
- Which to pick, Science: As of Oct 15, 2026, Claude Opus 5.5 leads O3 in Science at #31 against #67.
- Which to pick, Long context: As of Oct 15, 2026, Claude Opus 5.5 leads O3 in Long context at #1 against #110.
- Which to pick, Factuality: As of Oct 15, 2026, Claude Opus 5.5 leads O3 in Factuality at #1 against #105.
- Which to pick, Abstraction (ARC): As of Oct 15, 2026, Claude Opus 5.5 leads O3 in Abstraction (ARC) at #1 against #37.

As of Oct 15, 2026, Claude Opus 5.5 is tied for state of the art in Reasoning (since Oct 2, 2026; sources LMArena Text (style-controlled, hard prompts); methodology v1.0).

As of Oct 15, 2026, O3 is a former state-of-the-art holder in General LLM (since Jul 28, 2025; sources LMArena Text (style-controlled, overall); methodology v1.0).