Claude Sonnet 5.5 vs GPT-6 Sol: price, scores, context

Side-by-side comparison

Criterion	Claude Sonnet 5.5	GPT-6 Sol
Developer	Anthropic	OpenAI
Released	September 28, 2026	September 22, 2026
Capability index	95.9 / 100	89.2 / 100
Input price	$2	$2
Output price	$10	$10
Cost of a typical task	$0.06	$0.06
Context window	1,000,000 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	June 2026	April 20, 2026

Two models head to head

This comparison pits two frontier models, the ones you pick when quality comes first against each other: Claude Sonnet 5.5 and GPT-6 Sol, one from Anthropic, the other from OpenAI. The first dates from September 28, 2026, the second from September 22, 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.

Performance

On our capability index, Claude Sonnet 5.5 scores 95.9 out of 100 and GPT-6 Sol 89.2. Claude Sonnet 5.5 leads by 6.7 points.

On the 5 benchmarks reported for both, Claude Sonnet 5.5 wins 3 times and GPT-6 Sol 1:

GPQA Diamond (PhD-level science questions): Claude Sonnet 5.5 95.6%, GPT-6 Sol 94.3%
OTIS Mock AIME (competition mathematics problems): Claude Sonnet 5.5 100%, GPT-6 Sol 100%
FrontierMath (very hard research-level mathematics): Claude Sonnet 5.5 88.8%, GPT-6 Sol 89.8%
FrontierCode (advanced programming tasks): Claude Sonnet 5.5 52.1%, GPT-6 Sol 49.3%
APEX-Agents (professional tasks carried out by an agent): Claude Sonnet 5.5 75.5%, GPT-6 Sol 54.3%

Pricing

Claude Sonnet 5.5 costs $2 per million input tokens and $10 per million output tokens; GPT-6 Sol costs $2 and $10.

For a typical agent task (read 20,000 tokens, write 2,000), expect $0.06 with Claude Sonnet 5.5 versus $0.06 with GPT-6 Sol. The cost is almost the same.

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

Under the hood

GPT-6 Sol reads more in one go: 1,050,000 tokens of context (roughly 1,575 pages), versus 1,000,000 for Claude Sonnet 5.5.

Reasoning mode: Claude Sonnet 5.5 yes, GPT-6 Sol yes. Tool calling: Claude Sonnet 5.5 yes, GPT-6 Sol yes. Image input: Claude Sonnet 5.5 yes, GPT-6 Sol yes.

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

Knowledge cutoff: June 2026 for Claude Sonnet 5.5, April 20, 2026 for GPT-6 Sol.

In short

Our reading of the data:

Choose Claude Sonnet 5.5 for a higher capability index.

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

Frequently asked questions

Claude Sonnet 5.5 or GPT-6 Sol: which is better?

On our index (Epoch AI data), Claude Sonnet 5.5 scores 95.9 and GPT-6 Sol 89.2 out of 100. The best choice also depends on price and on your use case.

Which one is cheaper?

Claude Sonnet 5.5. To read 20,000 tokens and write 2,000, expect $0.06 with Claude Sonnet 5.5 and $0.06 with GPT-6 Sol (prices as of October 22, 2026).

Which one has the larger context window?

GPT-6 Sol, with 1,050,000 tokens versus 1,000,000.

Can I run Claude Sonnet 5.5 or GPT-6 Sol on my own servers?

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

Claude Sonnet 5.5 versus GPT-6 Sol