Claude Fable 5.1 vs GPT-6 Astra
Claude Fable 5.1 (2026) and GPT-6 Astra (2026) are frontier-tier reasoning models from Anthropic and OpenAI. Claude Fable 5.1 ships a 1M-token context window, while GPT-6 Astra ships a 1.05M-token context window. On FrontierMath Tier 4, GPT-6 Astra leads by 9.8 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Pick GPT-6 Astra for math; token pricing is tied, so keep Claude Fable 5.1 only for already-validated prompts or route constraints.
Decision scorecard
Local evidence first| Signal | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1M | 1.05M |
| Cheapest output | $50/1M tokens | $50/1M tokens |
| Provider routes | 5 tracked | 2 tracked |
| Shared benchmarks | 3 shared | FrontierMath Tier 4 leader |
Decision tradeoffs
- Claude Fable 5.1 has broader tracked provider coverage for fallback and route flexibility.
- Local decision data tags Claude Fable 5.1 for Coding, RAG, and Agents.
- GPT-6 Astra holds a shared-benchmark lead on FrontierMath Tier 4, ahead by 9.8 points.
- GPT-6 Astra has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-6 Astra uniquely exposes Code execution in local model data.
- Local decision data tags GPT-6 Astra for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Claude Fable 5.1
$20,500
Cheapest tracked route/tier: Anthropic
GPT-6 Astra
$20,500
Cheapest tracked route/tier: OpenAI API
Estimated monthly gap: $0.00. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Cheapest tracked output pricing is tied, so migration risk shifts to quality, latency, and provider packaging.
- GPT-6 Astra adds Code execution in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Cheapest tracked output pricing is tied, so migration risk shifts to quality, latency, and provider packaging.
- Check replacement coverage for Code execution before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-09-01 | 2026-09-03 |
| Context window | 1M | 1.05M |
| Parameters | — | — |
| Architecture | Decoder Only | - |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2026-06 | 2026-04 |
Pricing and availability
| Pricing attribute | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| Input price | $10/1M tokens | $10/1M tokens |
| Output price | $50/1M tokens | $50/1M tokens |
| Providers |
Capabilities
| Capability | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| JSON / Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Claude Fable 5.1 | GPT-6 Astra |
|---|---|---|
| FrontierMath Tier 4 | 87.8 | 97.6 |
| ARC-AGI-2 | 90.0 | 95.0 |
| FrontierCode 1.1 Main | 50.9 | 53.3 |
Deep dive
On shared benchmark coverage, FrontierMath Tier 4 has Claude Fable 5.1 at 87.8 and GPT-6 Astra at 97.6, with GPT-6 Astra ahead by 9.8 points; ARC-AGI-2 has Claude Fable 5.1 at 90 and GPT-6 Astra at 95, with GPT-6 Astra ahead by 5 points; FrontierCode 1.1 Main has Claude Fable 5.1 at 50.9 and GPT-6 Astra at 53.3, with GPT-6 Astra ahead by 2.4 points. The largest visible gap is 9.8 points on FrontierMath Tier 4, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on code execution: GPT-6 Astra. Both models share vision, multimodal input, reasoning mode, and JSON / Tool use, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Claude Fable 5.1 lists $10/1M input and $50/1M output tokens on the cheapest tracked provider, while GPT-6 Astra lists $10/1M input and $50/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend is tied on the cheapest tracked routes. Availability is 5 providers versus 2, so concentration risk also matters.
Choose Claude Fable 5.1 when vision-heavy evaluation and broader provider choice are central to the workload. Choose GPT-6 Astra when coding workflow support and larger context windows are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, Claude Fable 5.1 or GPT-6 Astra?
GPT-6 Astra supports 1.05M tokens, while Claude Fable 5.1 supports 1M tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Claude Fable 5.1 or GPT-6 Astra?
Neither is cheaper on tracked token pricing. Both list $10/1M input and $50/1M output tokens on the cheapest tracked route. Provider discounts, batch pricing, or route-specific tiers can still change the final bill.
Is Claude Fable 5.1 or GPT-6 Astra open source?
Claude Fable 5.1 is listed under Proprietary. GPT-6 Astra is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Claude Fable 5.1 or GPT-6 Astra?
Both Claude Fable 5.1 and GPT-6 Astra expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Claude Fable 5.1 or GPT-6 Astra?
Both Claude Fable 5.1 and GPT-6 Astra expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Where can I run Claude Fable 5.1 and GPT-6 Astra?
Claude Fable 5.1 is available on Anthropic, AWS Bedrock, GCP Vertex AI, Microsoft Foundry, and OpenRouter. GPT-6 Astra is available on OpenAI API and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-10-07. Data sourced from public model cards and provider documentation.