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Claude Opus 4.5 vs GPT-OSS-120B
Comprehensive side-by-side LLM comparison
Claude Opus 4.5 leads with 37.5% higher average benchmark score. Claude Opus 4.5 offers 131.9K more tokens in context window than GPT-OSS-120B. Claude Opus 4.5 is $Infinity cheaper per million tokens. Claude Opus 4.5 supports multimodal inputs. Claude Opus 4.5 is available on 3 providers. Overall, Claude Opus 4.5 is the stronger choice for coding tasks.
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Anthropic
Claude Opus 4.5, released by Anthropic in November 2025, is a large language model from the Claude 4.5 family built for demanding reasoning tasks, advanced code generation, and complex agentic workflows. It features a 200K token context window, 64K maximum output tokens, native image understanding, and extended thinking with configurable effort levels. Opus 4.5 targets deep analytical work, multi-step tool orchestration, and applications requiring sustained reasoning across long, complex tasks.
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OpenAI
GPT-OSS-120B, released by OpenAI in August 2025, is an open-weight large language model with 120 billion parameters distributed under the Apache 2.0 license. It represents OpenAI's entry into the open-source model space, enabling developers to self-host and fine-tune a GPT-5-generation-class model. GPT-OSS-120B targets research applications, on-premises deployments, and custom fine-tuning workflows requiring a large open-weight base model.
3 months newer
GPT-OSS-120B
OpenAI
2025-08
Claude Opus 4.5
Anthropic
2025-11-01
Pricing Comparison
Cost per million tokens (USD)
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Claude Opus 4.5
Input:$5.00
Output:$25.00($Infinity cheaper)
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GPT-OSS-120B
Input:$Infinity
Output:$Infinity
Performance Metrics
Context window and performance specifications
Average performance across 2 common benchmarks
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Claude Opus 4.5
Average Score:77.4%(+37.5%)
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GPT-OSS-120B
Average Score:39.9%
Performance comparison across key benchmark categories
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Claude Opus 4.5
Science87.0%(+8.7%)
Agents67.8%(+66.2%)
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GPT-OSS-120B
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Knowledge Cutoff
Training data recency comparison
Claude Opus 4.5
2025-05
More recent knowledge cutoff means awareness of newer technologies and frameworks
Provider Availability & Performance
Available providers and their performance metrics
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Claude Opus 4.5
3 providers
Anthropic
AWS Bedrock
Google Cloud Vertex AI
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GPT-OSS-120B
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Claude Opus 4.5
Avg Score:77.4%(+37.5%)
Providers:3
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GPT-OSS-120B
Avg Score:39.9%
Providers:1