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GPT-5.1 Codex High vs GPT-6 Luna

GPT-5.1 Codex High and GPT-6 Luna are closely matched at 29.4 and 44.5 on the LLM Stats Score. GPT-6 Luna is 17.2x cheaper per token.

OpenAI · OpenAI · Updated for 2026

Which is better?

GPT-5.1 Codex High and GPT-6 Luna are closely matched on the overall LLM Stats Score at 29.4 and 44.5.

On price, GPT-6 Luna is roughly 17.2x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

GPT-6 Luna also accepts a larger context window (1,050,000 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 GPT-5.1 Codex High

  • you want predictable pricing at $1.25/M input and $10.00/M output

Choose GPT-6 Luna

  • cost matters — it's about 17.2x cheaper per token
  • you process long inputs — it offers a 1,050,000 token context window
  • you want the most recent training data — it shipped Sep 2026

At a glance

The differences that matter most.

GPT-5.1 Codex High
OpenAI
GPT-6 Luna
OpenAI
Core performance indexes
LLM Stats Score
29.4
#135
44.5
#40
Reasoning
29.2
#128
40.0
#58
Cost, coverage & limits
Benchmark wins
—
—
Input price
$1.25 / M
$0.10 / M
Output price
$10.00 / M
$0.50 / M
Context window
400,000
1,050,000

Individual benchmarks

1 reported for GPT-5.1 Codex High · 5 for GPT-6 Luna

No common benchmarks found

GPT-5.1 Codex High and GPT-6 Lunadon'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-6 Luna costs less

For input processing, GPT-5.1 Codex High ($1.25/1M tokens) is 12.5x more expensive than GPT-6 Luna ($0.10/1M tokens).

For output processing, GPT-5.1 Codex High ($10.00/1M tokens) is 20.0x more expensive than GPT-6 Luna ($0.50/1M tokens).

In conclusion, GPT-5.1 Codex High is more expensive than GPT-6 Luna.*

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

Lowest available price from all providers
Wed Sep 23 2026 • llm-stats.com
OpenAI
GPT-5.1 Codex High
Input tokens$1.25
Output tokens$10.00
Best providerOpenAI
OpenAI
GPT-6 Luna
Input tokens$0.10
Output tokens$0.50
Best providerOpenAI
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

GPT-6 Luna accepts 1,050,000 input tokens compared to GPT-5.1 Codex High's 400,000 tokens. Both models can generate responses up to 128,000 tokens.

OpenAI
GPT-5.1 Codex High
Input400,000 tokens
Output128,000 tokens
OpenAI
GPT-6 Luna
Input1,050,000 tokens
Output128,000 tokens
Wed Sep 23 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both GPT-5.1 Codex High and GPT-6 Luna support multimodal inputs.

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

GPT-5.1 Codex High

Text
Images
Audio
Video

GPT-6 Luna

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.

GPT-5.1 Codex High

Proprietary

Closed source

GPT-6 Luna

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.1 Codex High was released on 2025-11-12, while GPT-6 Luna was released on 2026-09-22.

GPT-6 Luna is 10 months newer than GPT-5.1 Codex High.

GPT-5.1 Codex High

Nov 12, 2025

10 months ago

GPT-6 Luna

Sep 22, 2026

0 days ago

10mo newer

Knowledge Cutoff

When training data ends

GPT-6 Luna has a documented knowledge cutoff of 2026-05-18, while GPT-5.1 Codex High's cutoff date is not specified.

We can confirm GPT-6 Luna's training data extends to 2026-05-18, but cannot make a direct comparison without GPT-5.1 Codex High's cutoff date.

GPT-5.1 Codex High

—

GPT-6 Luna

May 2026

Provider Availability

GPT-5.1 Codex High is available from OpenAI. GPT-6 Luna is available from OpenAI.

GPT-5.1 Codex High

openai logo
OpenAI
Input Price:Input: $1.25/1MOutput Price:Output: $10.00/1M

GPT-6 Luna

openai logo
OpenAI
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against GPT-5.1 Codex High and GPT-6 Luna side-by-side, then vote on the output you prefer.

GPT-5.1 Codex High
✓ Preferred
GPT-6 Luna
Open in Playground

FAQ

Common questions about GPT-5.1 Codex High vs GPT-6 Luna.

Which is better, GPT-5.1 Codex High or GPT-6 Luna?

GPT-5.1 Codex High and GPT-6 Luna are closely matched on the LLM Stats Score at 29.4 and 44.5. GPT-5.1 Codex High is made by OpenAI and GPT-6 Luna is made by OpenAI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does GPT-5.1 Codex High compare to GPT-6 Luna in benchmarks?

GPT-5.1 Codex High scores AIME 2025: 96.7%. GPT-6 Luna scores DeepSWE 1.1: 66.6%, OSWorld 2.0: 52.7%, Agents' Last Exam: 50.9%, FrontierCode 1.1: 42.4%, AutomationBench v1.0.6: 20.7%.

Is GPT-5.1 Codex High cheaper than GPT-6 Luna?

GPT-6 Luna is 12.5x cheaper for input tokens. GPT-5.1 Codex High costs $1.25/M input and $10.00/M output via openai. GPT-6 Luna costs $0.10/M input and $0.50/M output via openai.

What are the context window sizes for GPT-5.1 Codex High and GPT-6 Luna?

GPT-5.1 Codex High supports 400K tokens and GPT-6 Luna supports 1.1M tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-5.1 Codex High and GPT-6 Luna?

Key differences include LLM Stats Score (29.4 vs 44.5), context window (400K vs 1.1M), input pricing ($1.25 vs $0.10/M). See the full comparison above for benchmark-by-benchmark results.

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