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Claude Opus 5.5 vs GPT-5.1 Codex Mini

Claude Opus 5.5 leads the LLM Stats Score 60.4 to -3.1. GPT-5.1 Codex Mini is 11.6x cheaper per token.

Anthropic · OpenAI · Updated for 2026

Which is better?

Claude Opus 5.5 leads the overall LLM Stats Score 60.4 to -3.1, ranking #1 overall.

On price, GPT-5.1 Codex Mini is roughly 11.6x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Opus 5.5 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.

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

Choose Claude Opus 5.5

  • overall performance matters — it scores 60.4 and ranks #1 on LLM Stats
  • your work emphasizes reasoning — it leads those capability indexes
  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Sep 2026

Choose GPT-5.1 Codex Mini

  • cost matters — it's about 11.6x cheaper per token

At a glance

The differences that matter most.

Claude Opus 5.5
Anthropic
GPT-5.1 Codex Mini
OpenAI
Core performance indexes
LLM Stats Score
60.4
#1
-3.1
#366
Reasoning
59.5
#1
-3.0
#358
Cost, coverage & limits
Benchmark wins
—
—
Input price
$4.00 / M
$0.25 / M
Output price
$20.00 / M
$2.00 / M
Context window
1,000,000
400,000

Individual benchmarks

31 reported for Claude Opus 5.5 · 1 for GPT-5.1 Codex Mini

No common benchmarks found

Claude Opus 5.5 and GPT-5.1 Codex Minidon'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

Pricing Analysis

Price comparison per million tokens

GPT-5.1 Codex Mini costs less

For input processing, Claude Opus 5.5 ($4.00/1M tokens) is 16.0x more expensive than GPT-5.1 Codex Mini ($0.25/1M tokens).

For output processing, Claude Opus 5.5 ($20.00/1M tokens) is 10.0x more expensive than GPT-5.1 Codex Mini ($2.00/1M tokens).

In conclusion, Claude Opus 5.5 is more expensive than GPT-5.1 Codex Mini.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Fri Oct 23 2026 • llm-stats.com
Anthropic
Claude Opus 5.5
Input tokens$4.00
Output tokens$20.00
Best providerAnthropic
OpenAI
GPT-5.1 Codex Mini
Input tokens$0.25
Output tokens$2.00
Best providerOpenAI
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

Claude Opus 5.5 accepts 1,000,000 input tokens compared to GPT-5.1 Codex Mini's 400,000 tokens. Both models can generate responses up to 128,000 tokens.

Anthropic
Claude Opus 5.5
Input1,000,000 tokens
Output128,000 tokens
OpenAI
GPT-5.1 Codex Mini
Input400,000 tokens
Output128,000 tokens
Fri Oct 23 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Opus 5.5 and GPT-5.1 Codex Mini support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

Claude Opus 5.5

Text
Images
Audio
Video

GPT-5.1 Codex Mini

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-5.1 Codex Mini

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 5.5 was released on 2026-09-22, while GPT-5.1 Codex Mini was released on 2025-11-12.

Claude Opus 5.5 is 10 months newer than GPT-5.1 Codex Mini.

Claude Opus 5.5

Sep 22, 2026

4 weeks ago

10mo newer
GPT-5.1 Codex Mini

Nov 12, 2025

11 months ago

Knowledge Cutoff

When training data ends

Claude Opus 5.5 has a documented knowledge cutoff of 2026-06-01, while GPT-5.1 Codex Mini's cutoff date is not specified.

We can confirm Claude Opus 5.5's training data extends to 2026-06-01, but cannot make a direct comparison without GPT-5.1 Codex Mini's cutoff date.

Claude Opus 5.5

Jun 2026

GPT-5.1 Codex Mini

—

Provider Availability

Claude Opus 5.5 is available from Anthropic. GPT-5.1 Codex Mini is available from OpenAI.

Claude Opus 5.5

anthropic logo
Anthropic
Input Price:Input: $4.00/1MOutput Price:Output: $20.00/1M

GPT-5.1 Codex Mini

openai logo
OpenAI
Input Price:Input: $0.25/1MOutput Price:Output: $2.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against Claude Opus 5.5 and GPT-5.1 Codex Mini side-by-side, then vote on the output you prefer.

Claude Opus 5.5
✓ Preferred
GPT-5.1 Codex Mini
Open in Playground

FAQ

Common questions about Claude Opus 5.5 vs GPT-5.1 Codex Mini.

Which is better, Claude Opus 5.5 or GPT-5.1 Codex Mini?

Claude Opus 5.5 leads the LLM Stats Score 60.4 to -3.1. Claude Opus 5.5 is made by Anthropic and GPT-5.1 Codex Mini 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-5.1 Codex Mini 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-5.1 Codex Mini scores AIME 2025: 42.1%.

Is Claude Opus 5.5 cheaper than GPT-5.1 Codex Mini?

GPT-5.1 Codex Mini is 16.0x cheaper for input tokens. Claude Opus 5.5 costs $4.00/M input and $20.00/M output via anthropic. GPT-5.1 Codex Mini costs $0.25/M input and $2.00/M output via openai.

What are the context window sizes for Claude Opus 5.5 and GPT-5.1 Codex Mini?

Claude Opus 5.5 supports 1.0M tokens and GPT-5.1 Codex Mini supports 400K 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-5.1 Codex Mini?

Key differences include LLM Stats Score (60.4 vs -3.1), context window (1.0M vs 400K), input pricing ($4.00 vs $0.25/M). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Opus 5.5 and GPT-5.1 Codex Mini?

Claude Opus 5.5 is developed by Anthropic and GPT-5.1 Codex Mini is developed by OpenAI.

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