Blended rate
Same for both
$20.00 per 1M each
Cheaper on long prompts
Claude Fable 5.1
above 272,000 input tokens
Higher benchmark scores
Claude Fable 5.1
leads on 8 of 11 figures
Bigger context window
GPT-6 Astra
1,050,000 vs 1,000,000 tokens
Cheaper cached input
Claude Fable 5.1
$0.25 vs $1.00, 75% less
Where each one wins
GPT-6 Astra
- Larger context window 1,050,000 tokens
- Higher graduate-level science (GPQA Diamond) 96.1 vs 93.7
- Higher physics research reasoning (CritPt) 31.7 vs 29.7
- Higher answer reliability (Omniscience Non-Hallucination) 48.7 vs 27.4
- Offers Flex and Priority pricing not listed for Claude Fable 5.1
Claude Fable 5.1
- Cheaper cached input $0.25 vs $1.00, 75% less
- Cheaper on all four workloads
- Cheaper on long prompts above 272,000 input tokens
- Higher overall intelligence (Intelligence Index) 53.4 vs 52.7
- Higher coding ability (Coding Index) 81.6 vs 76.9
- Higher multi-step tool use (Agentic Index) 57.9 vs 51
- Ahead on 5 more benchmark figures
What four workloads cost
One run, and the same run a thousand times.
They cost the same on a chat turn and a RAG answer, so the difference only shows up further down: on an agent loop, Claude Fable 5.1 costs $1.25 against $1.70.
| Workload | GPT-6 Astra | Claude Fable 5.1 | ×1,000 | Difference |
|---|---|---|---|---|
| Chat turn 1,000 in / 500 out | $0.0350 | $0.0350 | $35.00 / $35.00 | Same |
| RAG answer 10,000 in / 800 out | $0.1400 | $0.1400 | $140.00 / $140.00 | Same |
| Agent loop 32,000 in / 700 out × 20 calls | $1.70 | $1.25 | $1,700.00 / $1,250.00 | Claude Fable 5.1 is 26% cheaper |
| Long document 400,000 in / 3,000 out | $8.23 | $4.15 | $8,225.00 / $4,150.00 | Claude Fable 5.1 is 50% cheaper |
Price per 1M tokens
Above 272,000 input tokens the rates change, and the new rate applies to the whole request, not just the tokens past that point: GPT-6 Astra's input goes from $10.00 to $20.00. That is where the cheaper model changes.
| Context band | Price | GPT-6 Astra | Claude Fable 5.1 | Difference |
|---|---|---|---|---|
| Prompts up to 272,000 tokens | Input | $10.00 | $10.00 | Same |
| Prompts up to 272,000 tokens | Cached input | $1.00 | $0.25 | Claude Fable 5.1 is 75% cheaper |
| Prompts up to 272,000 tokens | Output | $50.00 | $50.00 | Same |
| Prompts over 272,000 tokens | Input | $20.00 | $10.00 | Claude Fable 5.1 is 50% cheaper |
| Prompts over 272,000 tokens | Cached input | $2.00 | $0.25 | Claude Fable 5.1 is 88% cheaper |
| Prompts over 272,000 tokens | Output | $75.00 | $50.00 | Claude Fable 5.1 is 33% cheaper |
Blended: GPT-6 Astra $20.00, Claude Fable 5.1 $20.00 per 1M — one rate at 3:1 input to output, for comparing two models at a glance.
GPT-6 Astra priced by OpenAI, Claude Fable 5.1 by Anthropic. Standard tier, pay-as-you-go.
Other pricing tiers
Both models offer Batch, worth up to 50% off their standard rates, and the cheaper model is the same one on every tier — so the tier you buy changes the bill rather than the choice. Only GPT-6 Astra lists Flex and Priority, at up to 50% off its own standard rate; Claude Fable 5.1 offers none of them.
Every tier either model sells is here, so this is the whole price sheet. A saving is measured against that model's own standard rate — how we read tiers.
| Tier | GPT-6 Astra | Claude Fable 5.1 | Cheaper |
|---|---|---|---|
| Batch | $5.00 in / $25.00 out 50% off Standard | $5.00 in / $25.00 out 50% off Standard | Same |
| Flex only on GPT-6 Astra | $5.00 in / $25.00 out 50% off Standard | Not offered | — |
| Priority only on GPT-6 Astra | $20.00 in / $100.00 out | Not offered | — |
Benchmarks
They share 11 figures: GPT-6 Astra leads on 3, Claude Fable 5.1 on 8. The widest gap is 21.3 points, on answer reliability (Omniscience Non-Hallucination).
Overall intelligence
Intelligence Index — Overall intelligence across reasoning, knowledge & math evals
Claude Fable 5.1 ahead by 0.7
Coding ability
Coding Index — Coding ability across software-engineering evals
Claude Fable 5.1 ahead by 4.7
Multi-step tool use
Agentic Index — Tool use & multi-step agent task performance
Claude Fable 5.1 ahead by 6.9
Graduate-level science
GPQA Diamond — Graduate-level questions in biology, chemistry & physics
GPT-6 Astra ahead by 2.4
Expert-exam performance
Humanity's Last Exam — Expert-level questions across many academic domains
Claude Fable 5.1 ahead by 4.4
Long-context reasoning
AA-LCR — Long-context reasoning across large inputs
Claude Fable 5.1 ahead by 4.6
Scientific coding
SciCode — Research-level scientific coding tasks
Claude Fable 5.1 ahead by 6.6
Physics research reasoning
CritPt — Unpublished physics research reasoning problems
GPT-6 Astra ahead by 2
Real-world task performance
GDPval — Economically valuable, real-world knowledge work
Claude Fable 5.1 ahead by 9.6
Factual accuracy
Omniscience Accuracy — Breadth of factual knowledge across domains
Claude Fable 5.1 ahead by 4.6
Answer reliability
Omniscience Non-Hallucination — How reliably the model avoids fabricated answers
GPT-6 Astra ahead by 21.3
Each figure is that model's best published run, with the effort level named beside it — where these scores come from.
Specifications
GPT-6 Astra holds 50,000 more input tokens in one request. Only GPT-6 Astra lists web search.
| Specification | GPT-6 Astra | Claude Fable 5.1 |
|---|---|---|
| Context window | 1,050,000 tokens | 1,000,000 tokens |
| Max output | 128,000 tokens | 128,000 tokens |
| Takes in | Text, image, file | Text, image, file |
| Puts out | Text | Text |
| Knowledge cutoff | 30 Apr 2026 | 30 Jun 2026 |
| Released | 3 Sep 2026 | 1 Sep 2026 |
| Status | Active | Active |
| Sold by | OpenAI | Anthropic |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Web search | Yes | Not listed |
| Prompt caching | Yes | Yes |
| Code execution | Yes | Yes |
| Computer use | Yes | Yes |
| Open weights | Not listed | Not listed |
| Reasoning | Yes | Yes |
FAQs
- Is GPT-6 Astra cheaper than Claude Fable 5.1?
- They cost the same on a typical exchange: 1,000 input tokens with a 500-token reply comes to $0.0350 on either.
- How much do GPT-6 Astra and Claude Fable 5.1 cost per 1M tokens?
- GPT-6 Astra costs $10.00 for input and $50.00 for output. Claude Fable 5.1 costs $10.00 and $50.00. Standard pay-as-you-go rates, as of 3 Sep 2026.
- Which is better, GPT-6 Astra or Claude Fable 5.1?
- On published benchmarks, Claude Fable 5.1. It leads on 8 of the 11 figures both models report, including overall intelligence (Intelligence Index), where it scores 53.4 against 52.7.
- Is GPT-6 Astra or Claude Fable 5.1 cheaper for long prompts?
- Claude Fable 5.1, above 272,000 input tokens. A rate that changes at a context length applies to the whole request, not only the tokens past it, so the switch is sharp rather than gradual.
- Is Batch pricing cheaper for GPT-6 Astra or Claude Fable 5.1?
- Batch input costs $5.00 on GPT-6 Astra and $5.00 on Claude Fable 5.1, 50% below the standard rate on both.
- Does GPT-6 Astra or Claude Fable 5.1 have a bigger context window?
- GPT-6 Astra, at 1,050,000 tokens against 1,000,000. That is 50,000 more input tokens in a single request.