GPT-6 Astra and GPT-5.6 Sol occupy the top of OpenAI’s model hierarchy, but they are not interchangeable. Astra is the more expensive agent model, with OpenAI’s broad hosted-tool set and a 128K output ceiling. Sol remains the lower-cost frontier option for coding and agent workloads.
The practical default is Sol when it meets your quality target; Astra when evaluations show that its extra capability reduces failures or human intervention enough to justify the premium. Astra is still in a staged rollout, so availability is also part of the decision.
Astra vs Sol at a glance
| GPT-6 Astra | GPT-5.6 Sol | |
|---|---|---|
| Status | Rolling out; Trusted Access enterprises first | Publicly available |
| API model | gpt-6-astra | gpt-5.6-sol |
| Context | 1.05M | 1.05M |
| Maximum output | 128K | Verify for your endpoint |
| Standard price | $10 input / $50 output | $5 input / $30 output list |
| Cached input | $1 | $0.50 list |
| Reasoning | low, medium, high, xhigh, max | Includes advanced reasoning modes |
| Best fit | Hard agent tasks, computer use, long tool workflows | Coding agents and frontier work at lower cost |
Prices are per million tokens. Sol’s qualifying promotional price is currently $4/M input, $0.40/M cached input and $20/M output through at least November 21, 2026, which widens the near-term cost gap.
The price difference
At list price, Astra costs twice as much as Sol for input and about 67% more for output. A request using 100,000 input tokens and 10,000 output tokens costs roughly $1.50 on Astra versus $0.80 on Sol list pricing, before caching or processing-mode discounts.
Astra requests above 272K input tokens receive OpenAI’s long-context multiplier on the entire request: 2× input/cache and 1.5× output. Long context is therefore a capability, not a reason to fill the window by default.
Both models may be cheaper through Batch or Flex where supported. Compare end-to-end job cost, including retries, tool loops and review—not just the first request.
Where Astra is differentiated
OpenAI documents Astra with web and file search, code interpreter, hosted shell, computer use, MCP, tool search, skills, apply patch and image generation on the Responses API. That is a strong fit for agents that move across code, terminals, documents, browsers and external systems.
Sol is still a serious coding and agent model. If your workflow primarily edits code, runs tests and calls ordinary functions, the added Astra premium needs to prove itself in your evaluation set.
Availability changes the answer
OpenAI describes Astra as rolling out first to enterprises in the Trusted Access Program, with broader API and ChatGPT availability in the coming days. Do not remove a working Sol deployment until Astra appears in your project and passes production-like tests.
OpenAI’s documentation did not establish a separate universal Codex availability promise for Astra when this comparison was published. Product availability and API model availability should be checked independently.
Choose Astra when
- complex computer-use or hosted-tool workflows are central;
- 128K maximum output materially matters;
- max reasoning improves success on your own difficult tasks;
- fewer failed attempts offset the higher token price;
- your account already has documented access.
Choose Sol when
- coding and repository work dominate;
- it already meets your quality and reliability target;
- throughput and cost matter more than the newest capability ceiling;
- you need a broadly available production model today;
- the temporary promotional price applies to your usage.
How to evaluate the two
Build a representative set of real tasks and measure:
- successful completion without intervention;
- tool-call and structured-output validity;
- latency to a usable result;
- input, cached-input and output cost;
- retries and recovery behavior;
- reviewer time and rollback rate.
Our AI testing and evaluation guide explains how to build these gates, while AI operations covers production fallbacks and monitoring.
Verdict
GPT-6 Astra is the capability choice; GPT-5.6 Sol is the value choice. Start with Sol for ordinary frontier coding and agent work, then promote only the tasks where Astra produces a measurable reliability or autonomy gain. Read the full GPT-6 Astra guide for pricing modes and rollout details.