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Claude Fable 5.1 vs GPT-5 Codex

Claude Fable 5.1 leads the LLM Stats Score 56.8 to 26.8.

Anthropic · OpenAI · Updated for 2026

Which is better?

Claude Fable 5.1 leads the overall LLM Stats Score 56.8 to 26.8, ranking #2 overall.

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

Choose Claude Fable 5.1

  • overall performance matters — it scores 56.8 and ranks #2 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 Fable 5.1
Anthropic
GPT-5 Codex
OpenAI
Core performance indexes
LLM Stats Score
56.8
#2
26.8
#138
Reasoning
53.9
#5
26.7
#137
Coding
36.0
#23
19.4
#99
Cost, coverage & limits
Benchmark wins
—
—
Input price
$10.00 / M
— / M
Output price
$50.00 / M
— / M
Context window
1,000,000
—

Individual benchmarks

7 reported for Claude Fable 5.1 · 1 for GPT-5 Codex

No common benchmarks found

Claude Fable 5.1 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 Fable 5.1 specifies input context (1,000,000 tokens). Only Claude Fable 5.1 specifies output context (128,000 tokens).

Anthropic
Claude Fable 5.1
Input1,000,000 tokens
Output128,000 tokens
OpenAI
GPT-5 Codex
Input- tokens
Output- tokens
Sat Sep 05 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Fable 5.1 supports multimodal inputs, whereas GPT-5 Codex does not.

Claude Fable 5.1 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Fable 5.1

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 Fable 5.1

Proprietary

Closed source

GPT-5 Codex

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Fable 5.1 was released on 2026-09-01, while GPT-5 Codex was released on 2025-09-15.

Claude Fable 5.1 is 12 months newer than GPT-5 Codex.

Claude Fable 5.1

Sep 1, 2026

3 days ago

11mo newer
GPT-5 Codex

Sep 15, 2025

11 months ago

Knowledge Cutoff

When training data ends

GPT-5 Codex has a documented knowledge cutoff of 2024-09-30, while Claude Fable 5.1's cutoff date is not specified.

We can confirm GPT-5 Codex's training data extends to 2024-09-30, but cannot make a direct comparison without Claude Fable 5.1's cutoff date.

Claude Fable 5.1

—

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 Fable 5.1 and GPT-5 Codex side-by-side, then vote on the output you prefer.

Claude Fable 5.1
✓ Preferred
GPT-5 Codex
Open in Playground

FAQ

Common questions about Claude Fable 5.1 vs GPT-5 Codex.

Which is better, Claude Fable 5.1 or GPT-5 Codex?

Claude Fable 5.1 leads the LLM Stats Score 56.8 to 26.8. Claude Fable 5.1 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 Fable 5.1 compare to GPT-5 Codex in benchmarks?

Claude Fable 5.1 scores OSWorld 2.0: 77.9%, CursorBench v3.2: 73.4%, Humanity's Last Exam: 65.0%, GDPval-AA: 61.8%, Terminal-Bench 4.0: 55.8%. GPT-5 Codex scores SWE-Bench Verified: 74.5%.

What are the context window sizes for Claude Fable 5.1 and GPT-5 Codex?

Claude Fable 5.1 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 Fable 5.1 and GPT-5 Codex?

Key differences include LLM Stats Score (56.8 vs 26.8), multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Fable 5.1 and GPT-5 Codex?

Claude Fable 5.1 is developed by Anthropic and GPT-5 Codex is developed by OpenAI.

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