Claude Opus 4.8 (Fast) vs gpt-oss-120b
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-oss-120b.
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-oss-120b
gpt-oss-120b is an open-weight, 117B-parameter Mixture-of-Experts (MoE) language model from OpenAI designed for high-reasoning, agentic, and general-purpose production use cases. It activates 5.1B parameters per forward pass and is optimized...
Technical Specifications
| Specification | Claude Opus 4.8 (Fast) | gpt-oss-120b |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Context Window | 1,000,000 tokens | 131,072 tokens |
| Agent Suitability | N/A | N/A |
| Time to First Token (TTFT) | N/A | N/A |
| Deployment Model | managed api | managed api |
| Production Stability | beta | stable |
| API Available | Yes | Yes |
| Released Date | 2026-05-27 | 2025-08-05 |
API Pricing Comparison
Input Price per Million Tokens
Claude Opus 4.8 (Fast)
$10.00
gpt-oss-120b
$0.03
Output Price per Million Tokens
Claude Opus 4.8 (Fast)
$50.00
gpt-oss-120b
$0.15
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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-oss-120b Quirks & Gotchas
No developer gotchas reported.