Claude Opus 4.8 vs GPT-5.5: Anthropic's latest flagship takes on OpenAI's best
Anthropic's refreshed flagship versus OpenAI's frontier reasoning engine.
Claude Opus 4.8 is Anthropic's latest flagship, refining Opus 4.7's reasoning with better instruction following and deeper multi-step planning. GPT-5.5 is OpenAI's top-tier reasoning model. Both target the same premium tier at $5/M input tokens, but Opus 4.8 undercuts GPT-5.5 on output pricing by $5 per million tokens.
Cost Comparison
Based on 100,000 input tokens (50% cached), 5,000 output tokens, and 100 requests.
Side-by-side specs
| Spec | Claude Opus 4.8 | GPT-5.5 |
|---|---|---|
| Input Cost (per M) | $5.00 | $5.00 |
| Output Cost (per M) | $25.00 (better on this spec) | $30.00 |
| Cached Input (per M) | $0.50 | $0.50 |
| Batch Discount | 50% | 50% |
How they differ
Claude Opus 4.8 costs $5.00 per million input tokens and $25.00 per million output tokens, with a 90% caching discount. GPT-5.5 costs $5.00 per million input tokens and $30.00 per million output tokens, also with a 90% caching discount. Both support a 50% batch discount. At 1M output tokens per day, Opus 4.8 saves roughly $1,825 per year compared to GPT-5.5 on output alone.
Verdict
Claude Opus 4.8 edges out GPT-5.5 on pure pricing thanks to cheaper output tokens. For long-form generation, report writing, and deep code synthesis, Opus 4.8 is the more economical premium pick. GPT-5.5 remains competitive for OpenAI-ecosystem teams who value its tool integrations and structured output features.
Which should you pick?
Choose Claude Opus 4.8
Long-form content generation, deep code synthesis, multi-step autonomous agents where output token volume dominates your bill. Anthropic's tool-use and prompt caching ecosystem.
Choose GPT-5.5
OpenAI-native workflows, Assistants API integration, structured outputs, and teams already invested in the OpenAI SDK and monitoring toolchain.