Pyyan / Compare / o3 / o4-mini vs Claude Opus 5.5
o3 / o4-mini vs Claude Opus 5.5
2 of 5Language Models · verified 24 Sept 2026
o3 / o4-miniOpenAIretiredClaude Opus 5.5Anthropiccurrent
| Specification | o3 / o4-mini | Claude Opus 5.5 |
|---|---|---|
| Summary | The o-series reasoning line, retired Feb 2026. | Fable 5.1's level of work on most tasks, at 40% less to run than Opus 5. |
| Context | — | 1M |
| Input ($/Mtok) | — | $4 |
| Output ($/Mtok) | — | $20 |
| Licence | Proprietary | Proprietary |
| Max output | — | 128K |
| Parameters | — | Not published |
| Released | — | 22 Sep 2026 |
| Model ID | — | claude-opus-5-5 |
| Category | Language Models | Language Models |
| Official | OpenAI ↗ | Anthropic ↗ |
Highlighted rows are where these differ.
o3 / o4-mini
- Reasoning is now an effort setting on GPT-5.x, not a separate model
Best for nothing — migrate.
Claude Opus 5.5
- 66.4% on Terminal-Bench 4.0 against 52.3% for Opus 5, on Anthropic's own harness
- Cache reads cut 60% to $0.20, and output more than 30% faster than Opus 5
- Attempts to work around its boundaries 85% less often than Opus 5, Anthropic reports
Best for agentic coding at flagship quality.