AI model comparison
Claude Fable 5.1 vs Claude Sonnet 4.5
Side by side comparison of Claude Fable 5.1 and Claude Sonnet 4.5 on pricing, benchmark scores, context window, and more.
Claude Fable 5.1 improves on Claude Fable 5 across the board, with the biggest gains in agentic coding, long-running agentic workflows, and knowledge work: long code refactors, front-end and visual
- Input / 1M
- $10
- Output / 1M
- $50
- Context
- 1M
Claude Sonnet 4.5 is Anthropic’s most advanced Sonnet model to date, optimized for real-world agents and coding workflows.
- Input / 1M
- $3
- Output / 1M
- $15
- Context
- 1M
Comparing image generators? Compare image models
At a glance
Quick verdict
How the two models stack up on the things people ask about most.
Lower price
Claude Sonnet 4.5
3.3x cheaper for a typical chat
Higher intelligence score
Not available
Not enough benchmark data
Larger context window
Tie
1M vs 1M tokens
Newer release
Claude Fable 5.1
Released September 1, 2026
Benchmarks
Benchmark scores
Independent scores from Artificial Analysis. Higher is better.
Intelligence index
Claude Fable 5.149.7Claude Sonnet 4.5Not availableCoding index
Claude Fable 5.180.7Claude Sonnet 4.552.1Agentic index
Claude Fable 5.157.2Claude Sonnet 4.515.8Pricing
Claude Fable 5.1 vs Claude Sonnet 4.5 API pricing
Per-token API rates. Cheaper option highlighted.
| Metric | Claude Fable 5.1 | Claude Sonnet 4.5 |
|---|---|---|
| Input tokensPer 1M tokens | $10 | $3 |
| Output tokensPer 1M tokens | $50 | $15 |
| Cached input (read)Per 1M tokens | $0.25 | $0.30 |
| Cache writePer 1M tokens | $12.50 | $3.75 |
| Long-context pricingPer 1M tokens, for very long prompts | Same rate at any length | $6 in / $22.50 out above 200K |
| Web searchPer request | $0.01 | $0.01 |
What it costs in practice
Estimated cost per 1,000 requests at standard rates. Coding and long-document figures also show the cost when the input is already cached.
Chat message
2K in, 500 out
Claude Fable 5.1$45Claude Sonnet 4.5$13.50Coding task
30K in, 4K out
Claude Fable 5.1$500$207.50 cachedClaude Sonnet 4.5$150$69 cachedLong document summary
150K in, 2K out
Claude Fable 5.1$1600$137.50 cachedClaude Sonnet 4.5$480$75 cachedSpecs
Context window and capabilities
How much each model can read, how much it can write, and what it accepts as input.
| Metric | Claude Fable 5.1 | Claude Sonnet 4.5 |
|---|---|---|
| Context window | 1M tokens | 1M tokens |
| Max output | 128K tokens | 64K tokens |
| Input types | File, Image, Text | File, Image, Text |
| Output types | Text | Text |
| Reasoning effort levels | Max, Extra high, High, Medium, Low | Not available |
| Default reasoning effort | High | Not available |
| Release date | September 1, 2026 | September 29, 2025 |
Features
Supported features
API features available for each model.
| Metric | Claude Fable 5.1 | Claude Sonnet 4.5 |
|---|---|---|
| Tool calling | Supported | Supported |
| Structured outputs | Supported | Supported |
| JSON mode | Supported | Supported |
| Reasoning | Supported | Supported |
| Temperature | Not supported | Supported |
| Stop sequences | Supported | Supported |
| Deterministic seed | Not supported | Not supported |
| Verbosity control | Supported | Not supported |
Keep exploring
More on these models
Other head-to-heads, the full model page, and the alternatives list for each model.
Claude Fable 5.1View full model details- Claude Fable 5.1 vs Claude Opus 5.5
- Claude Fable 5.1 vs GPT-6 Astra
- Claude Fable 5.1 vs GPT-6.1 Sol
- Claude Fable 5.1 vs Claude Sonnet 5.5
- Claude Fable 5.1 vs GPT-6.1 Terra
- Claude Fable 5.1 vs Gemini 4 Argon
- Claude Fable 5.1 vs Kimi K3.1 Pro
- Claude Fable 5.1 vs Muse Spark 1.3
- Claude Fable 5.1 vs Claude Haiku 5.5
- Claude Fable 5.1 vs Claude Opus 5
- Claude Fable 5.1 vs Claude Opus 4.8
Claude Sonnet 4.5View full model details- Claude Sonnet 4.5 vs Claude Opus 5.5
- Claude Sonnet 4.5 vs GPT-6.1 Sol
- Claude Sonnet 4.5 vs Claude Sonnet 5.5
- Claude Sonnet 4.5 vs Kimi K3
- Claude Sonnet 4.5 vs Kimi K3.1 Pro
- Claude Sonnet 4.5 vs Gemini 4 Argon
- Claude Sonnet 4.5 vs Claude Sonnet 5
- Claude Sonnet 4.5 vs Claude Opus 5
- Claude Sonnet 4.5 vs Claude Sonnet 4.6
- Claude Sonnet 4.5 vs Claude Opus 4.8
- Claude Sonnet 4.5 vs Muse Wonder
Our take
Claude Sonnet 4.5 is 3.3x cheaper for a typical chat. The right pick depends on your workload, so the quickest way to settle it is to send the same prompt to both and compare.
FAQ
Frequently asked questions
Is Claude Fable 5.1 or Claude Sonnet 4.5 cheaper?
Claude Sonnet 4.5 is cheaper for a typical chat (2K input tokens and 500 output tokens). Claude Sonnet 4.5 costs $3 per 1M input tokens and $15 per 1M output tokens, while Claude Fable 5.1 costs $10 per 1M input tokens and $50 per 1M output tokens.
Which has a bigger context window, Claude Fable 5.1 or Claude Sonnet 4.5?
Claude Fable 5.1 supports up to 1M tokens of context, compared with 1M for Claude Sonnet 4.5.
Can I use Claude Fable 5.1 and Claude Sonnet 4.5 at the same time?
Yes. Shortcut Chat sends one prompt to multiple models at once, so you can see Claude Fable 5.1 and Claude Sonnet 4.5 answer side by side and keep the better response.
Why choose? Ask both.
Send one prompt to Claude Fable 5.1 and Claude Sonnet 4.5 at the same time. Compare the answers side by side and keep the best one.