Claude Opus 4.8 (Fast) vs GPT-5.5
How do these models stack up? Below is an expert side-by-side comparison of specifications, context window capacity, live pricing per million tokens, and standardized benchmark scores for Claude Opus 4.8 (Fast) and GPT-5.5.
Claude Opus 4.8 (Fast)
Fast-mode variant of [Opus 4.8](/anthropic/claude-opus-4.8) - identical capabilities with higher output speed at 2x pricing relative to regular Opus 4.8. Learn more in Anthropic's docs: https://platform.claude.com/docs/en/build-with-claude/fast-mode
GPT-5.5
GPT-5.5 is OpenAI’s frontier model designed for complex professional workloads, building on GPT-5.4 with stronger reasoning, higher reliability, and improved token efficiency on hard tasks. It features a 1M+ token...
Technical Specifications
| Specification | Claude Opus 4.8 (Fast) | GPT-5.5 |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Context Window | 1,000,000 tokens | 1,050,000 tokens |
| Agent Suitability | N/A | 95/100 |
| Time to First Token (TTFT) | N/A | 380 ms |
| Deployment Model | managed api | managed api |
| Production Stability | beta | stable |
| API Available | Yes | Yes |
| Released Date | 2026-05-27 | 2026-04-24 |
API Pricing Comparison
Input Price per Million Tokens
Claude Opus 4.8 (Fast)
$10.00
GPT-5.5
$5.00
Output Price per Million Tokens
Claude Opus 4.8 (Fast)
$50.00
GPT-5.5
$30.00
Want to test both models live?
Run side-by-side prompt prompts in our dynamic Sandbox. Check execution speeds, latency metrics, and compute actual costs in real-time.
Benchmark Performance Metrics
Scores show the raw performance percentages verified across key evaluation suites. Higher bars indicate superior accuracy and capability in that domain.
Claude Opus 4.8 (Fast) Quirks & Gotchas
No developer gotchas reported.
GPT-5.5 Quirks & Gotchas
- ▸Best for JSON schema adherence — strict mode available via response_format parameter
- ▸Requires explicit tool_choice for deterministic function calling