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Claude Opus 4.5 vs GPT-5.3 Codex
Comprehensive side-by-side LLM comparison
GPT-5.3 Codex leads with 4.9% higher average benchmark score. Claude Opus 4.5 supports multimodal inputs. Claude Opus 4.5 is available on 3 providers. Both models have their strengths depending on your specific coding needs.
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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-5.3 Codex, released by OpenAI in February 2026, is a coding-specialized large language model from the GPT-5.3 family. It targets software engineering workflows including automated code generation, test writing, and agentic multi-file editing, built on the incremental improvements of the GPT-5.3 generation.
3 months newer
Claude Opus 4.5
Anthropic
2025-11-01
GPT-5.3 Codex
OpenAI
2026-02
Performance Metrics
Context window and performance specifications
Average performance across 1 common benchmarks
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Claude Opus 4.5
Average Score:59.8%
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GPT-5.3 Codex
Average Score:64.7%(+4.9%)
Performance comparison across key benchmark categories
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Claude Opus 4.5
Coding59.8%
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GPT-5.3 Codex
Coding64.7%(+4.9%)
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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-5.3 Codex
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Claude Opus 4.5
Avg Score:59.8%
Providers:3
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GPT-5.3 Codex
Avg Score:64.7%(+4.9%)
Providers:0