GPT-6 Luna (Reasoning)
by OpenAI
GPT-6 Luna (Reasoning) is a reasoning model from OpenAI, released on September 22, 2026. It has a 1.1M-token context window and can generate up to 128K output tokens. API pricing is $0.1 per 1M input tokens and $0.5 per 1M output tokens. It ranks #35 of 220 models by Intelligence Score with a score of 43.6.
GPT-6 Luna is OpenAI's GPT-6 model for focused, high-volume tasks. It supports text and image input with text output, a 1,050,000-token context window (maximum input 922,000 tokens), and 128,000 output tokens. Reasoning effort supports none, low, medium (API default), high, xhigh, and max. Responses API supports reasoning with function calling and built-in tools; Chat Completions function calling requires reasoning effort none. Standard per-million-token pricing is $0.1 input, $0.01 cached input, $0.125 cache writes, and $0.5 output. Prompts above 272K input tokens cost 2x input/cache and 1.5x output across the full request. Batch and Flex cost 50% of Standard; Fast costs 2x applicable rates. Regional processing adds 10% where available. Launch benchmarks are OpenAI-reported; effort, cost per task, and evaluation variants are recorded with each score.
Key specs
| Provider | OpenAI |
|---|---|
| Release date | 2026-09-22 |
| License | proprietary |
| Context window | 1.1M tokens |
| Max output | 128K tokens |
| Input price | $0.1 / 1M tokens |
| Output price | $0.5 / 1M tokens |
| Intelligence Score | 43.6 |
| Coding index | 29.6 |
Quick answers
What is the context window of GPT-6 Luna (Reasoning)?
GPT-6 Luna (Reasoning) has a context window of 1.1M tokens, with a maximum output of 128K tokens per response.
How much does GPT-6 Luna (Reasoning) cost?
GPT-6 Luna (Reasoning) costs $0.1 per 1M input tokens and $0.5 per 1M output tokens through the API.
Is GPT-6 Luna (Reasoning) open source?
No. GPT-6 Luna (Reasoning) is a proprietary model from OpenAI (proprietary license).
When was GPT-6 Luna (Reasoning) released?
OpenAI released GPT-6 Luna (Reasoning) on September 22, 2026.
How does GPT-6 Luna (Reasoning) compare to Claude Opus 5.5 (Reasoning)?
GPT-6 Luna (Reasoning) scores 43.6 on the Intelligence Score versus 60.5 for Claude Opus 5.5 (Reasoning), the current #1. Input pricing is $0.1 vs $4 per 1M tokens.
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