Claude Fable 5 or GPT-6.1 Sol: which to choose?

Side-by-side comparison

Criterion	Claude Fable 5	GPT-6.1 Sol
Developer	Anthropic	OpenAI
Released	June 9, 2026	September 29, 2026
Capability index	90.8 / 100	92.1 / 100
Input price	$10	$2
Output price	$50	$10
Cost of a typical task	$0.30	$0.06
Context window	1,000,000 tokens	1,050,000 tokens
Maximum output	50,000 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	January 31, 2026	April 30, 2026

Two models head to head

Claude Fable 5 and GPT-6.1 Sol are two frontier models, the ones you pick when quality comes first, one from Anthropic, the other from OpenAI. Claude Fable 5 was released on June 9, 2026, GPT-6.1 Sol on September 29, 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 Fable 5 scores 90.8 out of 100 and GPT-6.1 Sol 92.1. GPT-6.1 Sol leads by 1.3 points.

On the 5 benchmarks reported for both, Claude Fable 5 wins 2 times and GPT-6.1 Sol 2:

GPQA Diamond (PhD-level science questions): Claude Fable 5 85.9%, GPT-6.1 Sol 95.4%
OTIS Mock AIME (competition mathematics problems): Claude Fable 5 100%, GPT-6.1 Sol 100%
FrontierMath (very hard research-level mathematics): Claude Fable 5 87%, GPT-6.1 Sol 93.7%
FrontierCode (advanced programming tasks): Claude Fable 5 53.5%, GPT-6.1 Sol 50.2%
APEX-Agents (professional tasks carried out by an agent): Claude Fable 5 63.6%, GPT-6.1 Sol 60%

Budget

Claude Fable 5 costs $10 per million input tokens and $50 per million output tokens; GPT-6.1 Sol costs $2 and $10.

For a typical agent task (read 20,000 tokens, write 2,000), expect $0.30 with Claude Fable 5 versus $0.06 with GPT-6.1 Sol. 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.

Context and capabilities

GPT-6.1 Sol reads more in one go: 1,050,000 tokens of context (roughly 1,575 pages), versus 1,000,000 for Claude Fable 5.

Reasoning mode: Claude Fable 5 yes, GPT-6.1 Sol yes. Tool calling: Claude Fable 5 yes, GPT-6.1 Sol yes. Image input: Claude Fable 5 yes, GPT-6.1 Sol yes.

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

Knowledge cutoff: January 31, 2026 for Claude Fable 5, April 30, 2026 for GPT-6.1 Sol.

In short

Our reading of the data:

Choose GPT-6.1 Sol for a higher capability index, a lower cost and a more recent release.

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

Frequently asked questions

Claude Fable 5 or GPT-6.1 Sol: which is better?

On our index (Epoch AI data), Claude Fable 5 scores 90.8 and GPT-6.1 Sol 92.1 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 $0.30 with Claude Fable 5 and $0.06 with GPT-6.1 Sol (prices as of October 22, 2026).

Which one has the larger context window?

GPT-6.1 Sol, with 1,050,000 tokens versus 1,000,000.

Can I run Claude Fable 5 or GPT-6.1 Sol on my own servers?

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

Claude Fable 5 versus GPT-6.1 Sol