GPT-6 Astra or Claude Fable 5.1?
Choose GPT-6 Astra when complex coding, research and multi-step agent work with a configurable model is the closer match. Choose Claude Fable 5.1 when ambitious coding, research and long-running asynchronous projects matters more. Test both on the same real tasks before moving a production workflow.
Complex coding, research and multi-step agent work with a configurable model
Ambitious coding, research and long-running asynchronous projects
GPT-6 Astra
Complex coding, research and multi-step agent work with a configurable model
Official specification ↗Claude Fable 5.1
Anthropic's frontier model for demanding reasoning and long-horizon agentic work.
Official specification ↗Side-by-side comparison
| Category | GPT-6 Astra | Claude Fable 5.1 |
|---|---|---|
| Provider | OpenAI | Anthropic |
| Type | Product · Reasoning Model | Model · Frontier reasoning model |
| Pricing summary | API / 1M tokens: $10 input, $1 cached input, $50 output; long-context/tool charges extra | $10 input, $0.25 cache read and $50 output per 1M tokens |
| Input price | Product or plan pricing | $10 / 1M tokens |
| Cached input | Not directly comparable | $0.25 / 1M tokens |
| Output price | Product or plan pricing | $50 / 1M tokens |
| Context window | Varies by included model and plan | 1M tokens |
| Maximum output | Varies by included model and surface | 128K tokens |
| Knowledge cutoff | Model-dependent; web access may add current information | June 2026 |
| Reasoning | Varies by selected model or mode | Adaptive, always on; high default effort |
| Relative speed | Varies by model, plan and workload | Slower |
| Input modalities | See documented product features | Text and image |
| Output modalities | See documented product features | Text |
| Tools and integrations | 1.05M-token context; up to 128K output; Text/image input and text output; Async tools and mid-turn steering; Reasoning effort from low to max | Claude API tool use, computer use and agent workflows |
| API / access | Product surface; see official source for API availability | Claude Messages API |
| Best fit | Complex coding, research and multi-step agent work with a configurable model | Ambitious coding, research and long-running asynchronous projects |
| Company | OpenAI | Anthropic |
| Product category | Product · Reasoning Model | Model · Frontier reasoning model |
| Current pricing note | API / 1M tokens: $10 input, $1 cached input, $50 output; long-context/tool charges extra | $10 input, $0.25 cache read and $50 output per 1M tokens |
| Best suited to | Complex coding, research and multi-step agent work with a configurable model | Ambitious coding, research and long-running asynchronous projects |
| Key capabilities | 1.05M-token context; up to 128K output; Text/image input and text output; Async tools and mid-turn steering; Reasoning effort from low to max | Long-horizon agents; Repository-scale coding; Multistep research; Vision and document work |
| Last verified | 2026-09-07 | 2026-09-08 |
| Official product source | https://developers.openai.com/api/docs/models/gpt-6-astra | https://platform.claude.com/docs/en/models/fable-5-1/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
GPT-6 Astra or Claude Fable 5.1: which should I choose?
Choose GPT-6 Astra for complex coding, research and multi-step agent work with a configurable model. Choose Claude Fable 5.1 for ambitious coding, research and long-running asynchronous projects. Validate the decision with your own prompts and total task cost.
Is GPT-6 Astra cheaper than Claude Fable 5.1?
Pricing units can differ. GPT-6 Astra: API / 1M tokens: $10 input, $1 cached input, $50 output; long-context/tool charges extra. Claude Fable 5.1: $10 input, $0.25 cache read and $50 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. GPT-6 Astra is positioned for complex coding, research and multi-step agent work with a configurable model; Claude Fable 5.1 is positioned for ambitious coding, research and long-running asynchronous projects. Run the same repository task on both.
How do their context windows compare?
GPT-6 Astra lists Varies by included model and plan; Claude Fable 5.1 lists 1M 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.