Claude Opus 4.5 vs gpt-oss-20b
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 4.5 and gpt-oss-20b.
Claude Opus 4.5
Claude Opus 4.5 is Anthropic’s frontier reasoning model optimized for complex software engineering, agentic workflows, and long-horizon computer use. It offers strong multimodal capabilities, competitive performance across real-world coding and...
gpt-oss-20b
gpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license. It uses a Mixture-of-Experts (MoE) architecture with 3.6B active parameters per forward pass, optimized for...
Technical Specifications
| Specification | Claude Opus 4.5 | gpt-oss-20b |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Context Window | 200,000 tokens | 131,072 tokens |
| Agent Suitability | 93/100 | N/A |
| Time to First Token (TTFT) | 550 ms | N/A |
| Deployment Model | managed api | managed api |
| Production Stability | stable | stable |
| API Available | Yes | Yes |
| Released Date | 2025-11-24 | 2025-08-05 |
API Pricing Comparison
Input Price per Million Tokens
Claude Opus 4.5
$5.00
gpt-oss-20b
$0.03
Output Price per Million Tokens
Claude Opus 4.5
$25.00
gpt-oss-20b
$0.14
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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 4.5 Quirks & Gotchas
- ▸Deep analytical reasoning — best for structured problem-solving
- ▸200K context is limiting compared to 1M of Opus 4.6+ — upgrade for long-document tasks
gpt-oss-20b Quirks & Gotchas
No developer gotchas reported.