AI / Claude Models Basics Interview Questions
What is Claude Fable 5 and what makes it different from Claude Opus 4.8?
Claude Fable 5 (claude-fable-5) is Anthropic's most capable widely-released model as of mid-2026, positioned above the Opus tier. It is designed for long-running agents, frontier intelligence tasks, and complex enterprise work.
| Feature | Claude Fable 5 | Claude Opus 4.8 |
|---|---|---|
| API ID | claude-fable-5 | claude-opus-4-8 |
| Context window | 1 million tokens | 1 million tokens |
| Max output tokens | 128,000 | 128,000 |
| Thinking | Always-on adaptive thinking | Adaptive thinking (configurable) |
| Pricing (input) | $10 / MTok | $5 / MTok |
| Pricing (output) | $50 / MTok | $25 / MTok |
| Data retention | 30-day minimum (no ZDR) | Available under ZDR |
| Availability | GA on Claude API, Bedrock, Vertex, Foundry | GA on all platforms |
Key differences to be aware of:
- Fable 5 is priced at 2× Opus 4.8 for both input and output tokens
- Fable 5 requires a minimum 30-day data retention period and is not available under zero data retention (ZDR) arrangements — organisations with ZDR requirements should use Opus 4.8
- Fable 5 uses always-on adaptive thinking, meaning it automatically applies extended reasoning to every request
- Migration from Opus 4.8 to Fable 5 is described as mostly drop-in since both use the same Messages API and tool use patterns
What data retention requirement makes Claude Fable 5 unsuitable for organisations with zero data retention (ZDR) agreements?
Which thinking mode does Claude Fable 5 use?
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