Claude Fable 5.1 vs GPT-6 Astra: API price, context and cost per task
The two most expensive general-purpose models on the market. Fable 5.1 is Anthropic's August refresh of the Fable 5 line; GPT-6 Astra is OpenAI's flagship from 3 September 2026.
Today both list at $10 per million input tokens and $50 per million output tokens. GPT-6 Astra reads more per request: 1,050,000 tokens against 1,000,000.
Data updated 2026-11-11 - source: public OpenRouter model list, refreshed daily. Prices in USD, excluding VAT.
Specs and prices side by side
| Claude Fable 5.1 | GPT-6 Astra | |
|---|---|---|
| Vendor | Anthropic | OpenAI |
| Input, per 1M tokens | $10 | $10 |
| Output, per 1M tokens | $50 | $50 |
| Cached input, per 1M | $0.25 | $1 |
| Batch (input / output) | $5 / $25 | $5 / $25 |
| Context window | 1,000,000 | 1,050,000 |
| Max output | 128,000 | 128,000 |
| Input types | text, images, files | text, images, files |
| Reasoning | Yes | Yes |
| Tool calling | Yes | Yes |
| On OpenRouter since | 1 Sep 2026 | 4 Sep 2026 |
Highlighted: the cheaper price or the larger limit. "Not published" means the figure is not in the public model listing yet.
What a month of work costs
Four typical workloads at today's list prices. Reasoning models also bill their thinking as output tokens, so treat output-heavy numbers as a floor.
| Workload | Claude Fable 5.1 | GPT-6 Astra | Difference |
|---|---|---|---|
| Support chatbot10,000 conversations a month, about 1,500 input and 400 output tokens each | $350 | $350 | same |
| Coding agent300 tasks a month, about 80,000 input tokens (code context re-read across steps) and 8,000 output tokens each | $360 | $360 | same |
| Coding agent with caching70% of input served from the prompt cache | $196 | $209 | |
| Long-document analysis1,000 documents a month, about 50,000 tokens in and a 1,500-token summary out | $575 | $575 | same |
| Content drafting600 articles a month, about 3,000 tokens of brief in and 2,500 tokens of draft out | $93 | $93 | same |
Price stability over the last 30 days
- Claude Fable 5.1: no change in the last 30 days.
- GPT-6 Astra: no change in the last 30 days.
What the vendors and benchmarks say
Claude Fable 5.1
"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..."model card on OpenRouter
- A refresh of the Fable 5 line, released on 20 August 2026. Anthropic withdrew Fable 5 in June 2026 and restored it on 1 July. Source: Anthropic
- Terminal-Bench 4.0: 55.8%; GDPval-AA v2.1: 1735 Elo. Source: Anthropic's Claude Opus 5.5 launch comparison
GPT-6 Astra
"GPT-6 Astra is OpenAI's flagship model for demanding end-to-end work."model card on OpenRouter
- OpenAI's flagship, presented on 3 September 2026 and rolled out in stages. Source: OpenAI
- Terminal-Bench 4.0: 57.9% (figure reported by OpenAI); GDPval-AA v2.1: 1542 Elo. Source: Anthropic's Claude Opus 5.5 launch comparison
Which one to pick
With list prices this close, the choice comes down to results and ecosystem rather than cost. Anthropic's Opus 5.5 comparison puts the two close on Terminal-Bench 4.0 (55.8% for Fable 5.1, 57.9% for Astra) and Fable ahead on GDPval-AA v2.1 (1735 vs 1542). Before paying flagship rates for either, check whether Claude Opus 5.5 - cheaper, and ahead of both on those same tests - already covers your task.
Cheaper models with a similar context window
Models from our comparison set that cost less than both on a blended basis and support tool calling. They are not equivalent in quality - test before switching.
- Claude Opus 5 (Anthropic): $5 / $25 per million tokens, 1M context
- Claude Opus 5.5 (Anthropic): $4 / $20 per million tokens, 1M context
- Kimi K3 (Moonshot AI): $0.192 / $16 per million tokens, 1.05M context
Related reading
- Muse Wonder vs Claude Opus 5.5, Fable 5.1 and GPT-6 Astra: Benchmarks
- Fable 5.1 vs Mythos 5.1: One Model, Two Rule Sets
- Claude Fable 5.1: Pricing, Features & Review (2026)
- Claude Fable 5.2 vs GPT-6 Astra and Gemini 4 Carbon
- Claude Opus 5.5 vs GPT-6 Astra: Plan or API?
- GPT-6.2 Astra: Leaks, Status and Rumours Before Launch
How we calculate
Prices are the public per-token list rates from OpenRouter's model list, which match the vendors' own API prices for first-party models and show the current routed price for open-weight models served by several hosts. Monthly costs multiply those rates by the token volumes in each workload; caching assumes the stated share of input is billed at the cached-input rate. Benchmarks and claims are quoted from the named sources, mostly the vendors themselves - treat them as a guide and test on your own tasks. See also the AI cost calculator and all tracked model prices.
Frequently asked questions
Which is cheaper, Claude Fable 5.1 or GPT-6 Astra?
As of 11 Nov 2026, Claude Fable 5.1 costs $10 per million input tokens and $50 per million output tokens; GPT-6 Astra costs $10 and $50. Claude Fable 5.1 is cheaper in 0 of the 4 monthly workloads we price on this page. The real bill also depends on how many reasoning tokens each model writes.
Which has the larger context window?
Claude Fable 5.1 reads up to 1,000,000 tokens and can write up to 128,000; GPT-6 Astra reads up to 1,050,000 and writes up to 128,000.
How much does a support chatbot cost on each model?
For 10,000 conversations a month (about 15 million input and 4 million output tokens) you would pay about $350 on Claude Fable 5.1 and $350 on GPT-6 Astra at list prices, before any caching or batch discounts.
Do they offer prompt caching or batch discounts?
Claude Fable 5.1 lists cached input at $0.25 per million and a batch rate of $5 / $25. GPT-6 Astra lists cached input at $1 per million and a batch rate of $5 / $25. Caching matters most for agents and chatbots that resend the same context on every turn.
// follow
New tests and price changes, straight to your feed reader
Free RSS, no account and no email needed.
Follow Quantslant →