Claude Opus 4.8 vs GPT-5.5 Instant
Claude Opus 4.8 is cheaper on output tokens, while Claude Opus 4.8 offers a larger context window. Choose Claude Opus 4.8 or GPT-5.5 Instant based on the trade-off between cost, context, and the benchmarks that matter for your use case.
| Spec | Claude Opus 4.8 | GPT-5.5 Instant |
|---|---|---|
| Provider | Anthropic | ZenMux |
| Input / 1M tokens | $5.00 | $5.00 |
| Output / 1M tokens | $25.00 | $30.00 |
| Context window | 1M | 400K |
| Parameters | — | — |
| Open weights | — | No |
| Released | — | May 2026 |
| LMArena (Chatbot Arena) Elo score | 1461 | 1419 |
| LMArena WebDev Elo score | 1556 | — |
| LMArena Vision Elo score | 1294 | 1250 |
| Epoch Capabilities Index score | 158 | 142 |
| GPQA Diamond score | 91.0 | 82.5 |
| FrontierMath score | 47.2 | — |
FAQ
Is Claude Opus 4.8 or GPT-5.5 Instant cheaper?
Claude Opus 4.8 is cheaper on output tokens ($25.00 vs $30.00 per 1M).
Which has the larger context window, Claude Opus 4.8 or GPT-5.5 Instant?
Claude Opus 4.8 has the larger context window (1M tokens).
Pricing is indicative — confirm with the provider before production use. Highlighted values indicate the better figure for that row.