GPT-6 Astra — OpenAI's most capable model for hard problems
GPT-6 Astra is built for the hardest end-to-end work: reasoning, coding and research, with a 1.05M-token context. $1.00 / 1M input, $5.00 / 1M output per 1M tokens.
- Reasoning effort control
- 1.05M-token context
- Image input
- Prompt caching
- Streaming
Try GPT-6 Astra
Chat with GPT-6 Astra, attach images, and see the tokens and cost of every answer.
gpt-6-astra$1.00 in · $5.00 out per 1M tokensTemperature and Top P work only with reasoning effort none.
Try one of these prompts
Messages are billed from your balance at the rates below, like an API call. Failed requests are free.
Real GPT-6 Astra output
One prompt, sent to GPT-6 Astra at low reasoning effort. Unedited.
Explain the difference between a mutex and a semaphore in two short paragraphs, and say when to use each.
A mutex is a lock that lets only one thread access a shared resource at a time. It has ownership: the thread that locks it must unlock it. Use a mutex to protect shared data or a critical section, such as updating a shared counter. A semaphore maintains a count of available permits: a thread acquires a permit to proceed and releases one when appropriate. Unlike a mutex, it has no ownership requirement, so one thread can release a permit for another. Use a semaphore to limit concurrent access to a resource pool or to signal that work is available.
Generated 2026-09-28. Answers vary from run to run.
GPT-6 Astra pricing
GPT-6 Astra is billed per token from your balance. Rates below are live, the same ones your account is charged.
Example sizes are for illustration. Your bill follows the tokens each request reports.
| Category | Defaultgpt-6-astra | gpt officialgpt-6-astra:gpt-0.7 | ||
|---|---|---|---|---|
| ≤ 272,000 input tokensPrice · 1M tokens | > 272,000 input tokensPrice · 1M tokens | ≤ 272,000 input tokensPrice · 1M tokens | > 272,000 input tokensPrice · 1M tokens | |
| Input | $1.00 | $2.00 | $7.00 | $14.00 |
| Output | $5.00 | $7.50 | $35.00 | $52.50 |
| Cached input | $0.10 | $0.20 | $0.70 | $1.40 |
| Cache write | $1.25 | $2.50 | $8.75 | $17.50 |
Total input includes cache reads and writes. The selected tier applies to every token category in the request. Examples use the standard tier.
What is GPT-6 Astra?
GPT-6 Astra is OpenAI's most capable model, built for the hardest end-to-end work: complex reasoning, coding, research and document creation. GPT-6 Astra reads up to 1.05M tokens of context and writes up to 128K tokens per request.
GPT-6 Astra always reasons: effort runs from low to max, and none is not supported. Raise the effort for deeper work and lower it when you need a faster, cheaper answer.
Model ID: gpt-6-astra · Input: text, images · Output: text · Formats: OpenAI Responses, OpenAI Chat Completions, Anthropic Messages.
Two ways to use GPT-6 Astra
Call it from your code, or let your coding agent do it for you.
Call it from your backend
Point the official OpenAI SDK at SeedRouter and keep your code. GPT-6 Astra answers both the Responses and Chat Completions formats.
- 1Create an API key
- 2Set the base URL to https://api.seedrouter.ai/v1
- 3Send gpt-6-astra as the model
Hand it to your coding agent
Copy a ready prompt. Your agent shows the request and cost before anything is spent.
- 1Copy the prompt
- 2Paste it into your agent
- 3Approve the request
What GPT-6 Astra is good at
GPT-6 Astra is for tasks where getting it right matters more than getting it fast.
Complex reasoning
GPT-6 Astra works through multi-step problems that simpler models get wrong.
Hard coding tasks
Design systems, untangle tricky bugs and plan large refactors.
Research and analysis
Feed it reports and papers and get careful, grounded comparisons.
Document creation
GPT-6 Astra drafts design docs, specs and reports you can ship.
Images in the prompt
GPT-6 Astra reads diagrams, charts and screenshots alongside your text.
Cheaper repeat context
Cached input on GPT-6 Astra costs 10% of the input rate.
What teams build with GPT-6 Astra
Architecture reviews
Have GPT-6 Astra check a design before your team builds it.
Long agent runs
Let an agent plan and carry out multi-step work with the whole context in view.
Analyst reports
Turn raw research into structured findings with a text.format schema.
Start using GPT-6 Astra in four steps
- 01
Create a key
Sign in and create an API key. Add credit whenever you need it; there is no subscription.
- 02
Change the base URL
Point the OpenAI SDK at https://api.seedrouter.ai/v1. Your code stays the same.
- 03
Pick GPT-6 Astra
Send gpt-6-astra as the model. Set reasoning effort from low to max to trade depth for speed and cost.
- 04
Check the bill
Every request shows its tokens and charge in your usage records.
GPT-6 Astra on SeedRouter at a glance
What you can use today.
- OpenAI Responses
- Yes, official format
- OpenAI Chat Completions
- Yes
- Anthropic Messages
- Yes
- Image input
- Yes, by URL
- Streaming
- Yes
- Prompt caching
- Yes, cached input and cache writes billed apart
- Reasoning effort none
- No, the lowest effort is low
- Failed requests
- Not charged
Batch, Flex, background mode and service tiers are not offered.
GPT-6 Astra limits
1.05M-token context
On GPT-6 Astra, prompt, images and history share one 1.05M-token window; input is capped at 922K.
128K tokens out
One GPT-6 Astra request can return up to 128K tokens, reasoning included.
Long prompts cost more
Above 272K input tokens, the whole GPT-6 Astra request is billed at the higher long-context rates.
No temperature or top_p
GPT-6 Astra always reasons, so it does not accept temperature, top_p or logprobs.
Why call GPT-6 Astra through SeedRouter
One key, three formats
Call GPT-6 Astra with OpenAI Responses, Chat Completions or Anthropic Messages, using the same key.
Pay per token
Top up once and spend it on any model. No plan, no monthly fee.
Failures are free
A request that errors is not charged.
Live prices
The rates on this page are the rates your account pays.
Prompt caching
Repeated prompt prefixes are read from the cache at a lower GPT-6 Astra rate.
Image input
Send diagrams, charts and screenshots by URL with your prompt.
Streaming
Stream GPT-6 Astra tokens as they arrive with stream: true.
Related models
Other models you can call with the same key.
Call GPT-6 Luna with the OpenAI SDK. The lowest-cost GPT-6 model, with a 1.05M-token context, live per-token pricing and a playground you can try right now.
View pricingCall GPT-6 Sol with the OpenAI SDK. 1.05M-token context, reasoning effort from none to max, live per-token pricing and a playground you can try right now.
View pricingCall GPT-6.1 Sol with the OpenAI SDK: near-Astra coding and agent work at a fifth of the price, 1.05M-token context, 95% off cached input. Try it now.
View pricingCall Claude Fable 5 with the Anthropic or OpenAI SDK. Deep reasoning, 1M-token context, forced tool use, live per-token pricing and a playground to test it.
View pricingCall Claude Fable 5.1 with the Anthropic or OpenAI SDK. Deep reasoning, 1M-token context, cheap cached reads, live pricing and a playground to try it today.
View pricingTry Claude Fable 5.2 for coding and problem solving with a 1M-token context. Compare live token prices and model tiers, then test it in the playground.
View pricingGPT-6 Astra guides
Walkthroughs and comparisons for this model.
GPT-6.1 Sol pricing explained: input, cached input, cache write and output rates, the 272K long-context rule, worked request costs and how to spend less.
Which GPT-6.1 Sol reasoning effort to use: real timings, token counts and costs at low, medium, high, xhigh and max, why it feels slow, and where to start.
GPT-6.1 Sol vs GPT-6 Astra and GPT-6 Sol: specs, prices, the benchmark gaps OpenAI published, what changed from GPT-6 Sol and which model to use.
An OpenRouter alternative for GPT-6, Claude and DeepSeek: per-token prices compared, the 5.5% credit fee, free model limits and how to switch your base URL.
How to run GPT-6 Astra, Sol and Luna in OpenAI Codex CLI with a SeedRouter key: the config.toml, the context window setting, test results and common errors.
When was GPT-6 released? GPT-6 Astra launched on September 3, 2026, and GPT-6 Sol and Luna on September 22. How the rollout went and where to use GPT-6 today.
Is GPT-6 free? Free and Go users get GPT-6 Luna in the ChatGPT desktop app. GPT-6 Astra needs a paid plan, and the API is paid per token.
How to access the GPT-6 API: get a key, call GPT-6 Astra, Sol or Luna with the OpenAI SDK, set reasoning effort, stream, send images and avoid common errors.
GPT-6 API pricing for Astra, Sol and Luna per million tokens: input, output, cached input, cache writes and the 272K long-context rate, with worked examples.
GPT-6 Astra vs Sol vs Luna compared: specs, prices, OpenAI benchmark results, reasoning effort and a clear pick for coding, agents and high-volume work.
GPT-6 Astra, Sol and Luna vs Claude Opus 5.5: specs, token prices, the benchmark results both labs published, and which model fits coding, agents and cost.
GPT-6 vs GPT-5.6 compared: Sol and Luna at half the price, the same 1.05M context, newer knowledge, OpenAI benchmark gains and what to change when you migrate.
Connect your tools
- Codex
Find configuration guides for using text models in Codex and check the API format your setup requires.
GPT-6 Astra FAQ
What is GPT-6 Astra?+
GPT-6 Astra is OpenAI's most capable model, built for the hardest end-to-end work: complex reasoning, coding, research and document creation. It has a 1.05M-token context window and writes up to 128K tokens per request.
Should I use GPT-6 Astra or GPT-6 Sol?+
Use GPT-6 Astra when a task is hard and mistakes are costly. GPT-6 Sol handles demanding coding and agent work at a lower price, and GPT-6 Luna suits focused, high-volume jobs.
How much does GPT-6 Astra cost?+
GPT-6 Astra is billed at $1.00 / 1M input and $5.00 / 1M output per 1M tokens. Cached input costs 10% of the input rate. Prompts above 272K tokens use the long-context rates shown in the pricing table.
Which reasoning effort levels does GPT-6 Astra support?+
GPT-6 Astra supports low, medium, high, xhigh and max. It does not support none, so it always reasons and does not accept temperature or top_p.
What is the knowledge cutoff of GPT-6 Astra?+
GPT-6 Astra has a knowledge cutoff of April 30, 2026. For newer facts, pass them in the prompt.
What is the GPT-6 Astra model ID and how do I call it?+
The model ID is gpt-6-astra. Create a SeedRouter API key, point the OpenAI SDK at https://api.seedrouter.ai/v1 and send gpt-6-astra as the model with the Responses or Chat Completions API.
Can GPT-6 Astra read images?+
Yes. GPT-6 Astra accepts images alongside text, sent by URL in the request. It returns text only.
Am I charged if a GPT-6 Astra request fails?+
No. A GPT-6 Astra request that returns an error is not charged. You pay only for the tokens a finished request reports.
Try GPT-6 Astra now
Send your first GPT-6 Astra request from the playground or your own code in minutes.