Claude Fable 5 or GPT-5.5 Pro: which to choose?
Claude Fable 5 (Anthropic) and GPT-5.5 Pro (OpenAI) compared point by point: measured performance, pricing, context and capabilities.
Data as of October 22, 2026
Side-by-side comparison
| Criterion | Claude Fable 5 | GPT-5.5 Pro |
|---|---|---|
| Developer | Anthropic | OpenAI |
| Released | June 9, 2026 | April 23, 2026 |
| Capability index | 90.8 / 100 | 96.9 / 100 |
| Input price | $10 | $30 |
| Output price | $50 | $180 |
| Cost of a typical task | $0.30 | $0.96 |
| Context window | 1,000,000 tokens | 1,050,000 tokens |
| Maximum output | 50,000 tokens | 100,000 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 | December 1, 2025 |
The match-up at a glance
Claude Fable 5 and GPT-5.5 Pro 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-5.5 Pro on April 23, 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-5.5 Pro 96.9. GPT-5.5 Pro leads by 6.1 points.
On the 3 benchmarks reported for both, Claude Fable 5 wins 0 times and GPT-5.5 Pro 2:
- GPQA Diamond (PhD-level science questions): Claude Fable 5 85.9%, GPT-5.5 Pro 93.9%
- OTIS Mock AIME (competition mathematics problems): Claude Fable 5 100%, GPT-5.5 Pro 100%
- FrontierMath (very hard research-level mathematics): Claude Fable 5 87%, GPT-5.5 Pro 87.7%
Budget
Claude Fable 5 costs $10 per million input tokens and $50 per million output tokens; GPT-5.5 Pro costs $30 and $180.
For a typical agent task (read 20,000 tokens, write 2,000), expect $0.30 with Claude Fable 5 versus $0.96 with GPT-5.5 Pro. Claude Fable 5 is 3.2 times cheaper, a gap that adds up quickly over 1,000 tasks: $660 difference.
Run the numbers with your own volumes in the agent cost calculator.
Features and limits
GPT-5.5 Pro 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-5.5 Pro yes. Tool calling: Claude Fable 5 yes, GPT-5.5 Pro yes. Image input: Claude Fable 5 yes, GPT-5.5 Pro yes.
Neither publishes its weights: both are used through an API.
Knowledge cutoff: January 31, 2026 for Claude Fable 5, December 1, 2025 for GPT-5.5 Pro.
In short
Our reading of the data:
- Choose Claude Fable 5 for a lower cost and a more recent release.
- Choose GPT-5.5 Pro for a higher capability index.
This verdict relies on public figures; it does not replace a trial on your own tasks.
Other comparisons
Frequently asked questions
Claude Fable 5 or GPT-5.5 Pro: which is better?
On our index (Epoch AI data), Claude Fable 5 scores 90.8 and GPT-5.5 Pro 96.9 out of 100. The best choice also depends on price and on your use case.
Which one is cheaper?
Claude Fable 5. To read 20,000 tokens and write 2,000, expect $0.30 with Claude Fable 5 and $0.96 with GPT-5.5 Pro (prices as of October 22, 2026).
Which one has the larger context window?
GPT-5.5 Pro, with 1,050,000 tokens versus 1,000,000.
Can I run Claude Fable 5 or GPT-5.5 Pro on my own servers?
No: both are closed models, available through an API.
Data sources
- Models.dev — Model data: models.dev (open-source project)
- OpenRouter — Market prices cross-checked with OpenRouter
- Epoch AI — AI Benchmarking Hub — Epoch AI, “AI Benchmarking Hub”, epoch.ai, CC BY 4.0
Data as of October 22, 2026
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