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Claude Sonnet 5.5 vs GPT-5.1 Codex High

Claude Sonnet 5.5 leads the LLM Stats Score 58.4 to 29.1. GPT-5.1 Codex High is 1.2x cheaper per token.

Anthropic · OpenAI · Updated for 2026

Which is better?

Claude Sonnet 5.5 leads the overall LLM Stats Score 58.4 to 29.1, ranking #2 overall.

On price, GPT-5.1 Codex High is roughly 1.2x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Sonnet 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 Sonnet 5.5

  • overall performance matters — it scores 58.4 and ranks #2 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 High

  • cost matters — it's about 1.2x cheaper per token

At a glance

The differences that matter most.

Claude Sonnet 5.5
Anthropic
GPT-5.1 Codex High
OpenAI
Core performance indexes
LLM Stats Score
58.4
#2
29.1
#153
Reasoning
57.2
#3
28.9
#145
Cost, coverage & limits
Benchmark wins
—
—
Input price
$2.00 / M
$1.25 / M
Output price
$10.00 / M
$10.00 / M
Context window
1,000,000
400,000

Individual benchmarks

47 reported for Claude Sonnet 5.5 · 1 for GPT-5.1 Codex High

No common benchmarks found

Claude Sonnet 5.5 and GPT-5.1 Codex Highdon'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 High costs less

For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) is 1.6x more expensive than GPT-5.1 Codex High ($1.25/1M tokens).

For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) costs the same as GPT-5.1 Codex High ($10.00/1M tokens).

In conclusion, Claude Sonnet 5.5 is more expensive than GPT-5.1 Codex High.*

* 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 Sonnet 5.5
Input tokens$2.00
Output tokens$10.00
Best providerAnthropic
OpenAI
GPT-5.1 Codex High
Input tokens$1.25
Output tokens$10.00
Best providerOpenAI
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

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

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

Input capabilities

Documented input modalities across available providers

Both Claude Sonnet 5.5 and GPT-5.1 Codex High support multimodal inputs.

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

Claude Sonnet 5.5

Text
Images
Audio
Video

GPT-5.1 Codex High

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 Sonnet 5.5

Proprietary

Closed source

GPT-5.1 Codex High

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Sonnet 5.5 was released on 2026-09-28, while GPT-5.1 Codex High was released on 2025-11-12.

Claude Sonnet 5.5 is 11 months newer than GPT-5.1 Codex High.

Claude Sonnet 5.5

Sep 28, 2026

3 weeks ago

10mo newer
GPT-5.1 Codex High

Nov 12, 2025

11 months ago

Knowledge Cutoff

When training data ends

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

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

Claude Sonnet 5.5

Jun 2026

GPT-5.1 Codex High

—

Provider Availability

Claude Sonnet 5.5 is available from Anthropic. GPT-5.1 Codex High is available from OpenAI.

Claude Sonnet 5.5

anthropic logo
Anthropic
Input Price:Input: $2.00/1MOutput Price:Output: $10.00/1M

GPT-5.1 Codex High

openai logo
OpenAI
Input Price:Input: $1.25/1MOutput Price:Output: $10.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

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

Claude Sonnet 5.5
✓ Preferred
GPT-5.1 Codex High
Open in Playground

FAQ

Common questions about Claude Sonnet 5.5 vs GPT-5.1 Codex High.

Which is better, Claude Sonnet 5.5 or GPT-5.1 Codex High?

Claude Sonnet 5.5 leads the LLM Stats Score 58.4 to 29.1. Claude Sonnet 5.5 is made by Anthropic and GPT-5.1 Codex High 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 Sonnet 5.5 compare to GPT-5.1 Codex High in benchmarks?

Claude Sonnet 5.5 scores BenchCAD (with Python tool): 96.3%, ArXivMath (with tools): 95.2%, Global-MMLU: 92.1%, MILU: 91.6%, SWE-bench Multilingual: 90.3%. GPT-5.1 Codex High scores AIME 2025: 96.7%.

Is Claude Sonnet 5.5 cheaper than GPT-5.1 Codex High?

GPT-5.1 Codex High is 1.6x cheaper for input tokens. Claude Sonnet 5.5 costs $2.00/M input and $10.00/M output via anthropic. GPT-5.1 Codex High costs $1.25/M input and $10.00/M output via openai.

What are the context window sizes for Claude Sonnet 5.5 and GPT-5.1 Codex High?

Claude Sonnet 5.5 supports 1.0M tokens and GPT-5.1 Codex High 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 Sonnet 5.5 and GPT-5.1 Codex High?

Key differences include LLM Stats Score (58.4 vs 29.1), context window (1.0M vs 400K), input pricing ($2.00 vs $1.25/M). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Sonnet 5.5 and GPT-5.1 Codex High?

Claude Sonnet 5.5 is developed by Anthropic and GPT-5.1 Codex High is developed by OpenAI.

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