Claude Fable 5.1 or Claude Haiku 5.5?
Choose Claude Fable 5.1 when ambitious coding, research and long-running asynchronous projects is the closer match. Choose Claude Haiku 5.5 when real-time user assistants, high-speed document triage and background data parsing matters more. Test both on the same real tasks before moving a production workflow.
Ambitious coding, research and long-running asynchronous projects
Real-time user assistants, high-speed document triage and background data parsing
Claude Fable 5.1
Anthropic's frontier model for demanding reasoning and long-horizon agentic work.
Official specification ↗Claude Haiku 5.5
Anthropic's ultra-responsive reasoning model designed for high-concurrency applications.
Official specification ↗Side-by-side comparison
| Category | Claude Fable 5.1 | Claude Haiku 5.5 |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Type | Model · Frontier reasoning model | Model · Fast model |
| Pricing summary | $10 input, $0.25 cache read and $50 output per 1M tokens | $0.80 input, $0.08 cache read and $4 output per 1M tokens |
| Input price | $10 / 1M tokens | $0.80 / 1M tokens |
| Cached input | $0.25 / 1M tokens | $0.08 / 1M tokens |
| Output price | $50 / 1M tokens | $4 / 1M tokens |
| Context window | 1M tokens | 500K tokens |
| Maximum output | 128K tokens | 64K tokens |
| Knowledge cutoff | June 2026 | July 2026 |
| Reasoning | Adaptive, always on; high default effort | Fast extended thinking |
| Relative speed | Slower | Instantaneous |
| Input modalities | Text and image | Text and image |
| Output modalities | Text | Text |
| Tools and integrations | Claude API tool use, computer use and agent workflows | Claude API tool use and computer use |
| API / access | Claude Messages API | Claude Messages API |
| Best fit | Ambitious coding, research and long-running asynchronous projects | Real-time user assistants, high-speed document triage and background data parsing |
| Company | Anthropic | Anthropic |
| Product category | Model · Frontier reasoning model | Model · Fast model |
| Current pricing note | $10 input, $0.25 cache read and $50 output per 1M tokens | $0.80 input, $0.08 cache read and $4 output per 1M tokens |
| Best suited to | Ambitious coding, research and long-running asynchronous projects | Real-time user assistants, high-speed document triage and background data parsing |
| Key capabilities | Long-horizon agents; Repository-scale coding; Multistep research; Vision and document work | 500K context; Ultra-low latency; Extended thinking; Cost-efficient triage |
| Last verified | 2026-09-08 | 2026-10-15 |
| Official product source | https://platform.claude.com/docs/en/models/fable-5-1/overview | https://platform.claude.com/docs/en/models/haiku-5-5/overview |
How we reached this verdict
We looked at the things that affect everyday use: what each product can do, how its plans are structured, where it fits into your existing workflow, and what the provider currently documents. Benchmark results are useful context, but they are not a universal winner score because test settings and tools vary.
Common questions
Claude Fable 5.1 or Claude Haiku 5.5: which should I choose?
Choose Claude Fable 5.1 for ambitious coding, research and long-running asynchronous projects. Choose Claude Haiku 5.5 for real-time user assistants, high-speed document triage and background data parsing. Validate the decision with your own prompts and total task cost.
Is Claude Fable 5.1 cheaper than Claude Haiku 5.5?
Pricing units can differ. Claude Fable 5.1: $10 input, $0.25 cache read and $50 output per 1M tokens. Claude Haiku 5.5: $0.80 input, $0.08 cache read and $4 output per 1M tokens. Check tool charges, plan limits, caching and long-context rules before comparing totals.
Which is better for coding and agent work?
Capability depends on the selected product surface, tools and harness. Claude Fable 5.1 is positioned for ambitious coding, research and long-running asynchronous projects; Claude Haiku 5.5 is positioned for real-time user assistants, high-speed document triage and background data parsing. Run the same repository task on both.
How do their context windows compare?
Claude Fable 5.1 lists 1M tokens; Claude Haiku 5.5 lists 500K tokens. A larger limit does not by itself guarantee better retrieval or lower cost.
Official sources
Use these provider pages to confirm current features, pricing and availability.
AI tools change quickly. We checked this page on 2026-09-08. Before you subscribe, confirm the latest price, regional availability and usage limits on the provider website.