Claude Opus 4.8 vs GPT-5.5 — the two most capable frontier models of 2026, head to head. Below is the full side-by-side: specifications, API pricing, context window, local hardware requirements, and a clear, data-driven recommendation on which to pick.
| Spec | Claude Opus 4.8 | GPT-5.5 |
|---|---|---|
| Developer | Anthropic | OpenAI |
| Type | LLM (reasoning) | LLM (reasoning) |
| Parameters | Undisclosed | Undisclosed |
| Context window | 1M | 1.05M |
| Modality | Text, Vision → Text | Text, Vision → Text |
| License | Proprietary | Proprietary |
| Open weights | ❌ No | ❌ No |
| Input price ($/1M) | $5.00 | $5.00 |
| Output price ($/1M) | $25.00 | $30.00 |
| VRAM (4-bit) | — | — |
| Min GPU (local) | — | — |
| Released | 2026 | 2026 |
Key differences
- Cost: Claude Opus 4.8 and GPT-5.5 are priced within ~15% of each other.
- Context: GPT-5.5 wins on context window (1.05M vs 1M) — better for long documents, large codebases and big RAG inputs.
- Openness: both are proprietary, API-only models — no self-hosting option for either.
Which should you choose?
Choose Claude Opus 4.8 if you want the lower per-token cost for high-volume workloads.
Choose GPT-5.5 if you need the larger context window.
→ Estimate real costs in the API cost calculator · check local hardware in the VRAM calculator · browse all 30+ models.
All specs and prices are pulled live from our AI models database and kept current. Compare either model against others, or estimate your own monthly spend with the free calculators above.