GPT-5.6 Luna vs GPT-6 Luna: price, scores, context

Side-by-side comparison

Criterion	GPT-5.6 Luna	GPT-6 Luna
Developer	OpenAI	OpenAI
Released	July 9, 2026	September 22, 2026
Capability index	79.6 / 100	80.3 / 100
Input price	$0.20	$0.10
Output price	$1.2	$0.50
Cost of a typical task	$0.006	$0.003
Context window	1,050,000 tokens	1,050,000 tokens
Maximum output	128,000 tokens	128,000 tokens
Reasoning mode	Yes	Yes
Tool calling	Yes	Yes
Accepted inputs	text, image, PDF	text, image, PDF
Open weights	No	No
Knowledge cutoff	February 16, 2026	May 18, 2026

The match-up at a glance

GPT-5.6 Luna and GPT-6 Luna are two budget models, built for high volumes at a low price, both built by OpenAI. GPT-5.6 Luna was released on July 9, 2026, GPT-6 Luna on September 22, 2026.

All figures below come from public sources checked on October 22, 2026: models.dev and OpenRouter for prices and capabilities, Epoch AI for scores.

What the benchmarks say

On our capability index, GPT-5.6 Luna scores 79.6 out of 100 and GPT-6 Luna 80.3. The gap is too small to separate them.

On the 5 benchmarks reported for both, GPT-5.6 Luna wins 2 times and GPT-6 Luna 3:

GPQA Diamond (PhD-level science questions): GPT-5.6 Luna 91.6%, GPT-6 Luna 90.5%
OTIS Mock AIME (competition mathematics problems): GPT-5.6 Luna 98.3%, GPT-6 Luna 98.9%
FrontierMath (very hard research-level mathematics): GPT-5.6 Luna 82.1%, GPT-6 Luna 78.9%
FrontierCode (advanced programming tasks): GPT-5.6 Luna 39.8%, GPT-6 Luna 42.4%
APEX-Agents (professional tasks carried out by an agent): GPT-5.6 Luna 43%, GPT-6 Luna 44.3%

Pricing

GPT-5.6 Luna costs $0.20 per million input tokens and $1.2 per million output tokens; GPT-6 Luna costs $0.10 and $0.50.

For a typical agent task (read 20,000 tokens, write 2,000), expect $0.006 with GPT-5.6 Luna versus $0.003 with GPT-6 Luna. GPT-6 Luna is 2.1 times cheaper, a gap that adds up quickly over 1,000 tasks: $3.4 difference.

Run the numbers with your own volumes in the agent cost calculator.

Features and limits

Both models have the same context window: 1,050,000 tokens, roughly 1,575 pages.

Reasoning mode: GPT-5.6 Luna yes, GPT-6 Luna yes. Tool calling: GPT-5.6 Luna yes, GPT-6 Luna yes. Image input: GPT-5.6 Luna yes, GPT-6 Luna yes.

Neither publishes its weights: both are used through an API.

Knowledge cutoff: February 16, 2026 for GPT-5.6 Luna, May 18, 2026 for GPT-6 Luna.

In short

Our reading of the data:

Choose GPT-6 Luna for a lower cost and a more recent release.

This verdict relies on public figures; it does not replace a trial on your own tasks.

Frequently asked questions

GPT-5.6 Luna or GPT-6 Luna: which is better?

On our index (Epoch AI data), GPT-5.6 Luna scores 79.6 and GPT-6 Luna 80.3 out of 100. The best choice also depends on price and on your use case.

Which one is cheaper?

GPT-6 Luna. To read 20,000 tokens and write 2,000, expect $0.006 with GPT-5.6 Luna and $0.003 with GPT-6 Luna (prices as of October 22, 2026).

Which one has the larger context window?

Neither: both accept 1,050,000 tokens.

Can I run GPT-5.6 Luna or GPT-6 Luna on my own servers?

No: both are closed models, available through an API.

GPT-5.6 Luna vs GPT-6 Luna