# Claude Fable 5.1 vs Claude Opus 5.5

URL: https://aistack.sh/compare/claude-fable-5-1-vs-claude-opus-5-5
Last updated: 2026-09-24
Model pages: https://aistack.sh/model/claude-fable-5-1, https://aistack.sh/model/claude-opus-5-5

## Quick answer

Use Claude Opus 5.5 by default: it is Claude Code's default model and costs $4 / $20 per 1M tokens, while Claude Fable 5.1 costs $10 / $50. Reach for Fable 5.1 when a long-running agentic coding, research or knowledge-work job justifies 2.5x the price, and note that on the Claude apps it needs usage credits on Pro or eats into a capped share of Max and Team premium limits.

## Specs

| Spec | Claude Fable 5.1 | Claude Opus 5.5 |
| --- | --- | --- |
| Released | Sep 1, 2026 | Sep 22, 2026 |
| Status | Available | Available |
| API model ID | claude-fable-5-1 | claude-opus-5-5 |
| API price (in / out) | $10 / $50 per 1M tokens | $4 / $20 per 1M tokens |
| Cache read | $0.25 per 1M tokens | $0.20 per 1M tokens |
| Context window | 1M tokens | 1M tokens |
| Plans | Pro (usage credits), Max, Team premium, Enterprise | Pro, Max, Team, Enterprise |
| Platforms | Claude API, Amazon Bedrock, Claude Platform on AWS, Google Cloud, Microsoft Foundry | Claude API, Amazon Bedrock, Claude Platform on AWS, Google Cloud, Microsoft Foundry |
| Runs in | Claude, Claude Code | Claude, Claude Code |

"-" means the value could not be verified on a vendor page.

## FAQ

### How much more does Claude Fable 5.1 cost than Opus 5.5?

2.5x on both sides: $10 / $50 per 1M input/output tokens against $4 / $20. Cache reads are $0.25 against $0.20.

### Which one does Claude Code use by default?

Opus 5.5. Claude Code's docs say neither Fable model is the default on any plan or provider; you select Fable 5.1 with the `fable` alias.

### Can I use Fable 5.1 on the Claude Pro plan?

Only through usage credits. Max and Team premium seats can spend up to 50% of their weekly limits on Fable; Opus is included from Pro up.

### Do they have the same context window?

Yes. Both have a 1M-token context window by default and 128k max output tokens.

## Also compared

- [Claude Opus 5.5 vs GPT-6 Astra](https://aistack.sh/compare/claude-opus-5-5-vs-gpt-6-astra)
- [Claude Opus 5.5 vs GPT-6 Sol](https://aistack.sh/compare/claude-opus-5-5-vs-gpt-6-sol)

## Sources

- [Claude Developer Platform release notes](https://platform.claude.com/docs/en/release-notes/overview), read 2026-09-24
- [Claude API pricing](https://platform.claude.com/docs/en/about-claude/pricing), read 2026-09-24
- [Claude models overview](https://platform.claude.com/docs/en/about-claude/models/overview), read 2026-09-24
- [Claude Code model configuration](https://code.claude.com/docs/en/model-config), read 2026-09-24
- [Claude plans and pricing](https://claude.com/pricing), read 2026-09-24
- [Anthropic: Claude Opus 5.5 launch](https://www.anthropic.com/claude-opus-5-5), read 2026-09-24