The AI arena is free today

Open Superagent

Claude Opus 5.5 vs GPT-5 Codex

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 26.6.

Anthropic · OpenAI · Updated for 2026

Which is better?

Claude Opus 5.5 leads the overall LLM Stats Score 59.7 to 26.6, ranking #1 overall.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Opus 5.5

  • overall performance matters — it scores 59.7 and ranks #1 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you want the most recent training data — it shipped Sep 2026

Choose GPT-5 Codex

  • you are already invested in the OpenAI ecosystem

At a glance

The differences that matter most.

Claude Opus 5.5
Anthropic
GPT-5 Codex
OpenAI
Core performance indexes
LLM Stats Score
59.7
#1
26.6
#155
Reasoning
57.8
#1
26.5
#152
Coding
51.7
#1
19.3
#112
Cost, coverage & limits
Benchmark wins
—
—
Input price
$4.00 / M
— / M
Output price
$20.00 / M
— / M
Context window
1,000,000
—

Individual benchmarks

31 reported for Claude Opus 5.5 · 1 for GPT-5 Codex

No common benchmarks found

Claude Opus 5.5 and GPT-5 Codexdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Context Window

Maximum input and output token capacity

Only Claude Opus 5.5 specifies input context (1,000,000 tokens). Only Claude Opus 5.5 specifies output context (128,000 tokens).

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
OpenAI
GPT-5 Codex
Input- tokens
Output- tokens
Tue Sep 22 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Opus 5.5 supports multimodal inputs, whereas GPT-5 Codex does not.

Claude Opus 5.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Opus 5.5

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 5.5

Proprietary

Closed source

GPT-5 Codex

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while GPT-5 Codex was released on 2025-09-15.

Claude Opus 5.5 is 12 months newer than GPT-5 Codex.

Claude Opus 5.5

Sep 22, 2026

0 days ago

1.0yr newer
GPT-5 Codex

Sep 15, 2025

1.0 years ago

Knowledge Cutoff

When training data ends

Claude Opus 5.5 has a knowledge cutoff of 2026-06-01, while GPT-5 Codex has a cutoff of 2024-09-30.

Claude Opus 5.5 has more recent training data (up to 2026-06-01), making it potentially better informed about events through that date compared to GPT-5 Codex (2024-09-30).

Claude Opus 5.5

Jun 2026

1.8 yr newer
GPT-5 Codex

Sep 2024

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Opus 5.5 and GPT-5 Codex side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
GPT-5 Codex
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs GPT-5 Codex.

Which is better, Claude Opus 5.5 or GPT-5 Codex?

Claude Opus 5.5 leads the LLM Stats Score 59.7 to 26.6. Claude Opus 5.5 is made by Anthropic and GPT-5 Codex is made by OpenAI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Opus 5.5 compare to GPT-5 Codex in benchmarks?

Claude Opus 5.5 scores BenchCAD (with Python tool): 96.2%, Global-MMLU: 94.3%, SWE-bench Multilingual: 93.9%, MILU: 93.1%, ArXivMath: 91.2%. GPT-5 Codex scores SWE-Bench Verified: 74.5%.

What are the context window sizes for Claude Opus 5.5 and GPT-5 Codex?

Claude Opus 5.5 supports 1.0M 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 5.5 and GPT-5 Codex?

Key differences include LLM Stats Score (59.7 vs 26.6), multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 5.5 and GPT-5 Codex?

Claude Opus 5.5 is developed by Anthropic and GPT-5 Codex is developed by OpenAI.

Related comparisons