GPT-6.1 Sol or GPT-6 Astra: which to choose?

Side-by-side comparison

Criterion	GPT-6.1 Sol	GPT-6 Astra
Developer	OpenAI	OpenAI
Released	September 29, 2026	September 4, 2026
Capability index	92.1 / 100	94.7 / 100
Input price	$2	$10
Output price	$10	$50
Cost of a typical task	$0.06	$0.30
Context window	1,050,000 tokens	1,050,000 tokens
Maximum output	128,000 tokens	128,000 tokens
Reasoning mode	Yes	Yes
Tool calling	Yes	Yes
Accepted inputs	text, image, PDF	text, image, PDF
Open weights	No	No
Knowledge cutoff	April 30, 2026	April 30, 2026

The match-up at a glance

This comparison pits two frontier models, the ones you pick when quality comes first against each other: GPT-6.1 Sol and GPT-6 Astra, both built by OpenAI. The first dates from September 29, 2026, the second from September 4, 2026.

All figures below come from public sources checked on October 22, 2026: models.dev and OpenRouter for prices and capabilities, Epoch AI for scores.

What the benchmarks say

On our capability index, GPT-6.1 Sol scores 92.1 out of 100 and GPT-6 Astra 94.7. GPT-6 Astra leads by 2.6 points.

On the 5 benchmarks reported for both, GPT-6.1 Sol wins 0 times and GPT-6 Astra 3:

GPQA Diamond (PhD-level science questions): GPT-6.1 Sol 95.4%, GPT-6 Astra 95.8%
OTIS Mock AIME (competition mathematics problems): GPT-6.1 Sol 100%, GPT-6 Astra 100%
FrontierMath (very hard research-level mathematics): GPT-6.1 Sol 93.7%, GPT-6 Astra 93.7%
FrontierCode (advanced programming tasks): GPT-6.1 Sol 50.2%, GPT-6 Astra 53.3%
APEX-Agents (professional tasks carried out by an agent): GPT-6.1 Sol 60%, GPT-6 Astra 64.7%

Budget

GPT-6.1 Sol costs $2 per million input tokens and $10 per million output tokens; GPT-6 Astra costs $10 and $50.

For a typical agent task (read 20,000 tokens, write 2,000), expect $0.06 with GPT-6.1 Sol versus $0.30 with GPT-6 Astra. GPT-6.1 Sol is 5 times cheaper, a gap that adds up quickly over 1,000 tasks: $240 difference.

Run the numbers with your own volumes in the agent cost calculator.

Features and limits

Both models have the same context window: 1,050,000 tokens, roughly 1,575 pages.

Reasoning mode: GPT-6.1 Sol yes, GPT-6 Astra yes. Tool calling: GPT-6.1 Sol yes, GPT-6 Astra yes. Image input: GPT-6.1 Sol yes, GPT-6 Astra yes.

Neither publishes its weights: both are used through an API.

Knowledge cutoff: April 30, 2026 for GPT-6.1 Sol, April 30, 2026 for GPT-6 Astra.

In short

Our reading of the data:

Choose GPT-6.1 Sol for a lower cost.
Choose GPT-6 Astra for a higher capability index.

This verdict relies on public figures; it does not replace a trial on your own tasks.

Frequently asked questions

GPT-6.1 Sol or GPT-6 Astra: which is better?

On our index (Epoch AI data), GPT-6.1 Sol scores 92.1 and GPT-6 Astra 94.7 out of 100. The best choice also depends on price and on your use case.

Which one is cheaper?

GPT-6.1 Sol. To read 20,000 tokens and write 2,000, expect $0.06 with GPT-6.1 Sol and $0.30 with GPT-6 Astra (prices as of October 22, 2026).

Which one has the larger context window?

Neither: both accept 1,050,000 tokens.

Can I run GPT-6.1 Sol or GPT-6 Astra on my own servers?

No: both are closed models, available through an API.

GPT-6.1 Sol vs GPT-6 Astra