# GPT-6 Luna

GPT-6 Luna is the small, cost-efficient tier of OpenAI's GPT-6 family, sitting below GPT-6 Sol and GPT-6 Astra. It targets high-volume, latency-sensitive work such as chat, classification and lightweight agents, and at higher reasoning effort it takes on tasks that previously needed a Sol-tier model. Its published context window is 1,050,000 tokens. The advertised input rate is $0.10 per million input tokens. The advertised output rate is $0.50 per million output tokens. Additional pricing brackets apply when the input exceeds a published context threshold.

- Model identifier: ` openai/gpt-6-luna `
- Creator: OpenAI
- Providers: OpenAI
- Model type: Text generation
- Canonical model page: [GPT-6 Luna](<https://impossibl.com/openai/gpt-6-luna>)
- API availability: Listed as serving through Impossibl.
- Creator release date: 2026-09-22

## Providers

OpenAI hosts GPT-6 Luna. Impossibl routes your request intelligently and handles failover automatically when a provider is down.

| Provider | Endpoint location | Routes | Verified context window | Tool calling |
| --- | --- | --- | --- | --- |
| OpenAI | Not specified | 1 | Not verified | Not verified |

The model price applies whichever provider serves the request. Endpoint locations do not guarantee inference residency.

## Specs and Capabilities

- Context window: 1,050,000 tokens
- Maximum output tokens: Not published in the public catalog; this is separate from the context window.
- Inputs: text, image
- Outputs: text
- Tool calling: Not published

## API access

Use ` openai/gpt-6-luna ` as the model identifier through the Impossibl API.

Published API endpoints:

- ` /v1/chat/completions `

[API quickstart](<https://impossibl.com/docs/agent-quickstart>) · [Models and billing documentation](<https://impossibl.com/docs/models>)

## Published API prices

All rates are in USD. An unpublished rate is unknown, not zero. Workspace-specific pricing, taxes, balance-purchase fees, billing adjustments, and tool charges can affect the amount paid.

| Usage | Published base rate | Billing unit |
| --- | --- | --- |
| Input | $0.10 | per million input tokens |
| Output | $0.50 | per million output tokens |
| Cache read | $0.01 | per million cached input tokens |
| Cache write (default retention) | $0.125 | per million tokens |
| Cache write (one-hour retention) | Not published | per million tokens |
| Audio input | Not published | per million audio input tokens |

### Long-context pricing

Base rates apply through 272,000 total input tokens per request. If total input, including cached input, strictly exceeds a threshold, use the highest qualifying threshold. Its rates apply to the whole request, not only the tokens above the threshold.

All rates below are USD per million tokens. Unpublished tier cache rates remain unknown; do not substitute the base cache rate.

| Total input tokens per request | Input | Output | Cache read | Cache write (default retention) | Cache write (one-hour retention) |
| --- | --- | --- | --- | --- | --- |
| Over 272,000 | $0.20 | $0.75 | $0.02 | $0.25 | Not published |

## Availability and retirement

The model is listed as serving. No retirement is announced in the current public catalog.

## Frequently asked questions

### What is GPT-6 Luna?

GPT-6 Luna is the small, cost-efficient tier of OpenAI's GPT-6 family, sitting below GPT-6 Sol and GPT-6 Astra. It targets high-volume, latency-sensitive work such as chat, classification and lightweight agents, and at higher reasoning effort it takes on tasks that previously needed a Sol-tier model.

Sources: [OpenAI model documentation](<https://developers.openai.com/api/docs/models/gpt-6-luna>); [OpenAI API changelog](<https://developers.openai.com/api/docs/changelog>); [OpenRouter model listing](<https://openrouter.ai/openai/gpt-6-luna>)

### How much does GPT-6 Luna cost?

GPT-6 Luna costs $0.10 per million input tokens and $0.50 per million output tokens through the Impossibl API. Cache reads cost $0.01 per million tokens; cache writes cost $0.125 per million tokens. These base rates apply through 272,000 total input tokens per request. Above 272,000 input tokens, the long-context rates in the pricing table apply to the whole request. All rates are in USD.

### What is the context length of GPT-6 Luna?

GPT-6 Luna has a 1,050,000-token context window through the Impossibl API.

### What inputs and outputs does GPT-6 Luna support?

GPT-6 Luna accepts text and image as input. GPT-6 Luna returns text.

### How do I use GPT-6 Luna through an API?

GPT-6 Luna is available through the Impossibl API. Use openai/gpt-6-luna as the model identifier with /v1/chat/completions. The quickstart explains how to create an API key and send your first request.

### When was GPT-6 Luna released?

OpenAI released GPT-6 Luna on September 22, 2026.

Sources: [Creator release announcement](<https://developers.openai.com/api/docs/changelog>)

## Sources and related links

Prices, limits, capabilities, endpoints, and availability come from the public Impossibl catalog. Creator documentation supplies descriptions and release dates where available; it does not override the published API offering.

- [Public Impossibl model catalog](<https://api.impossibl.com/v1/models>)
- [Full model directory as JSON](<https://impossibl.com/models.json>)
- [GPT-6 Luna: model details and pricing](<https://impossibl.com/openai/gpt-6-luna>)
- [Model directory](<https://impossibl.com/models>)
- [OpenAI model documentation](<https://developers.openai.com/api/docs/models/gpt-6-luna>)
- [OpenAI API changelog](<https://developers.openai.com/api/docs/changelog>)
- [OpenRouter model listing](<https://openrouter.ai/openai/gpt-6-luna>)