Model Comparison

Claude Opus 4.5 vs GPT-5 CodexWhich is better in 2026?

Claude Opus 4.5 significantly outperforms across most benchmarks.

Verdict: Claude Opus 4.5 vs GPT-5 Codex — which is better?

Claude Opus 4.5 (by Anthropic) and GPT-5 Codex (by OpenAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

Claude Opus 4.5 outperforms in 1 benchmarks (SWE-Bench Verified), while GPT-5 Codex is better at 0 benchmarks. Claude Opus 4.5 significantly outperforms across most benchmarks.

Choose Claude Opus 4.5 if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
  • you want the most recent training data — it shipped Nov 2025

Choose GPT-5 Codex if…

  • you are already invested in the OpenAI ecosystem
Want to compare interactively?Try the playground

Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

Claude Opus 4.5 outperforms in 1 benchmarks (SWE-Bench Verified), while GPT-5 Codex is better at 0 benchmarks.

Claude Opus 4.5 significantly outperforms across most benchmarks.

Sun Jun 07 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Claude Opus 4.5 specifies input context (200,000 tokens). Only Claude Opus 4.5 specifies output context (64,000 tokens).

Anthropic
Claude Opus 4.5
Input200,000 tokens
Output64,000 tokens
OpenAI
GPT-5 Codex
Input- tokens
Output- tokens
Sun Jun 07 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Claude Opus 4.5 supports multimodal inputs, whereas GPT-5 Codex does not.

Claude Opus 4.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Opus 4.5

Text
Images
Audio
Video

GPT-5 Codex

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

Claude Opus 4.5

Proprietary

Closed source

GPT-5 Codex

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 4.5 was released on 2025-11-24, while GPT-5 Codex was released on 2025-09-15.

Claude Opus 4.5 is 2 months newer than GPT-5 Codex.

Claude Opus 4.5

Nov 24, 2025

6 months ago

2mo newer
GPT-5 Codex

Sep 15, 2025

8 months ago

Knowledge Cutoff

When training data ends

Claude Opus 4.5 has a knowledge cutoff of 2025-03-31, while GPT-5 Codex has a cutoff of 2024-09-30.

Claude Opus 4.5 has more recent training data (up to 2025-03-31), making it potentially better informed about events through that date compared to GPT-5 Codex (2024-09-30).

Claude Opus 4.5

Mar 2025

6 mo newer
GPT-5 Codex

Sep 2024

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

Anthropic
Larger context window (200,000 tokens)
Supports multimodal inputs
Higher SWE-Bench Verified score (80.9% vs 74.5%)
OpenAI

No standout differentiators in the data we have for this pair.

Detailed Comparison

AI Model Comparison Table
Feature
Anthropic
Claude Opus 4.5
OpenAI
GPT-5 Codex

FAQ

Common questions about Claude Opus 4.5 vs GPT-5 Codex.

Which is better, Claude Opus 4.5 or GPT-5 Codex?

Claude Opus 4.5 significantly outperforms across most benchmarks. Claude Opus 4.5 is made by Anthropic and GPT-5 Codex is made by OpenAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does Claude Opus 4.5 compare to GPT-5 Codex in benchmarks?

Claude Opus 4.5 scores Tau2 Telecom: 98.2%, MMMLU: 90.8%, Tau2 Retail: 88.9%, GPQA: 87.0%, SWE-Bench Verified: 80.9%. GPT-5 Codex scores SWE-Bench Verified: 74.5%.

What are the context window sizes for Claude Opus 4.5 and GPT-5 Codex?

Claude Opus 4.5 supports 200K tokens and GPT-5 Codex supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Opus 4.5 and GPT-5 Codex?

Key differences include multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 4.5 and GPT-5 Codex?

Claude Opus 4.5 is developed by Anthropic and GPT-5 Codex is developed by OpenAI.

Related comparisons