> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kymaapi.com/llms.txt
> Use this file to discover all available pages before exploring further.

# GPT-6 Astra

> GPT-6 Astra is OpenAI's GPT-6 flagship for the hardest reasoning and long-horizon agentic work. Reach for it when a task needs the strongest OpenAI model available and a 1.05M-token window.

## Overview

GPT-6 Astra went GA on 2026-09-04. OpenAI's model page lists a 1,050,000-token context window, 128,000 max output tokens, an April 30, 2026 knowledge cutoff and reasoning token support. Text is input and output; images are input only; audio and video are not supported.

On Kyma it is served through the OpenAI-compatible endpoint with exact cost reporting in the usage.cost field. Prompt caching is supported at this model's cached input rate. The rate doubles above 272K prompt tokens, exactly as OpenAI prices it.

It is a closed model available by API only. It is the successor to GPT-5.6 Sol in OpenAI's line-up and is priced above it.

## Specs

| Field              | Value                                           |
| ------------------ | ----------------------------------------------- |
| Model ID           | `gpt-6-astra`                                   |
| Best for           | Hardest reasoning and long-horizon agentic work |
| Context window     | 1.05M                                           |
| Max output tokens  | 128K                                            |
| Input modalities   | Text, Image                                     |
| Output modalities  | Text                                            |
| Tool calling       | Yes                                             |
| Structured outputs | Yes                                             |
| Prompt caching     | Yes                                             |
| Speed              | Medium                                          |
| Cost band          | Premium                                         |
| Release stage      | Stable                                          |

## Pricing

|        | Per 1M tokens |
| ------ | :-----------: |
| Input  |    \$13.50    |
| Output |    \$67.50    |

Above a long prompt this model costs more per token, because the infrastructure
serving it charges more there. The threshold is on the **prompt**, so you know which
rate applies before you send.

| Prompt length        |  Input  |  Output  |
| -------------------- | :-----: | :------: |
| Standard             | \$13.50 |  \$67.50 |
| Above 272,000 tokens | \$27.00 | \$101.25 |

## Use this when

* **Hardest reasoning** — Multi-step analysis, proofs and planning where the strongest OpenAI model is the point.
* **Long-horizon agents** — A 1.05M-token window and 128K output cap keep long agent sessions in one context.
* **Document and image understanding** — Image input plus the long window for contracts, decks and screenshots.

## Not ideal for

Cost-sensitive or high-volume traffic — this is a flagship rate, and prompts above 272K tokens bill at twice it.

## Pick something else when

* You want the previous OpenAI flagship at a lower rate: use [`gpt-5.6-sol`](https://kymaapi.com/models/gpt-5.6-sol).
* You want the best general default overall: use [`qwen-3.6-plus`](/models/qwen-3.6-plus).

## Example

```python theme={null}
from openai import OpenAI

client = OpenAI(base_url="https://kymaapi.com/v1", api_key="kyma-...")

response = client.chat.completions.create(
    model="gpt-6-astra",
    messages=[{"role": "user", "content": "..."}],
    tools=[...],  # function calling supported
)
```

## Agent query example

Ask the API which models fit, instead of hardcoding an id:

```bash theme={null}
curl "https://kymaapi.com/v1/models?recommended_for=chat&tools=true&quality_tier=frontier-open"
```

## FAQ

**How does GPT-6 Astra compare with GPT-5.6 Sol?**

It is OpenAI's next flagship after Sol: the same 1.05M context and 128K output cap, a newer knowledge cutoff (April 30, 2026), and a higher rate. The Pricing table on this page has the current numbers.

**Why does the price double above 272K prompt tokens?**

OpenAI bills prompts above 272K tokens at its long-context rate, and Kyma passes that band through. The Pricing table on this page shows both rates.

**Why use GPT-6 Astra through Kyma?**

One API key and one OpenAI-compatible endpoint cover this and every other model on the platform, with prompt caching at the cached input rate and the exact cost of every request in usage.cost.