Claude Fable 5.1 vs Gemini 4 Argon vs GPT-6 Astra
Gemini 4 Argon comes out ahead, 74 to 68 and 66 on our weighted score, and it is the cheaper option too.
AnthropicClaude Fable 5.1
66/100- ECI166.4
- Price$10.00 / $50.00
- Context1M
- Our pick
GoogleGemini 4 Argon
74/100- ECI166.1
- Price$2.00 / $10.00
- Context1.05M
OpenAIGPT-6 Astra
68/100- ECI169.1
- Price$10.00 / $50.00
- Context1.05M
Gemini 4 Argon is our pick
Gemini 4 Argon is the better all-round choice, scoring 74/100 against GPT-6 Astra (68) and Claude Fable 5.1 (66). It leads on price and inputs & features. GPT-6 Astra wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGPT-6 AstraCapabilities Index (ECI): GPT-6 Astra 169.1 · Claude Fable 5.1 166.4 · Gemini 4 Argon 166.1
- Lowest priceGemini 4 ArgonGemini 4 Argon $4.00 · Claude Fable 5.1 $20.00 · GPT-6 Astra $20.00 per 1M tokens (3:1 blend)
- Longest contextGPT-6 Astra and Gemini 4 ArgonGPT-6 Astra 1,050,000 · Gemini 4 Argon 1,048,576 · Claude Fable 5.1 1,000,000 tokens
- Widest inputsGemini 4 ArgonClaude Fable 5.1: Text, Images, PDFs · Gemini 4 Argon: Text, Images, PDFs, Audio, Video · GPT-6 Astra: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Claude Fable 5.1 | Gemini 4 Argon | GPT-6 Astra |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 97 | 96 | 100 |
| Price | 25% | 0 | 20 | 0 |
| Inputs & features | 15% | 80 | 100 | 80 |
| Context window | 10% | 60 | 61 | 61 |
| Overall | 100% | 66/100 | 74/100 | 68/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Claude Fable 5.1Anthropic | Gemini 4 ArgonGoogle | GPT-6 AstraOpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 166.4 | 166.1 | 169.1 (best) |
| ECI rank | #6 of 165 | #7 of 165 | #1 of 165 (best) |
| GPQA DiamondGraduate-level science questions | — | 96.4% (best) | 95.8% |
| FrontierMath Tiers 1–3Research-level mathematics | 90.2% | 86.0% | 93.7% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% | 100% | 100% |
| SimpleQA VerifiedShort factual questions | 70.8% | 76.0% (best) | 75.6% |
| Price per million tokens | |||
| Input | $10.00 | $2.00 (best) | $10.00 |
| Output | $50.00 | $10.00 (best) | $50.00 |
| Cached input | $0.25 | $0.10 (best) | $1.00 |
| Blended (3:1) | $20.00 | $4.00 (best) | $20.00 |
| Long-context rate | Same rate | Same rate | Over 272K: $20.00 / $75.00 |
| Price source | Official Anthropic API | Official Google API | Official OpenAI API |
| Limits | |||
| Context window | 1,000,000 tokens | 1,048,576 tokens | 1,050,000 tokens (best) |
| Max output | 128,000 tokens (best) | 65,536 tokens | 128,000 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | No | Yes | No |
| Video | No | Yes | No |
| Reasoning | Yeslow · medium · high · xhigh · max | Yeslow · medium · high | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | claude-fable-5-1 | gemini-4-argon | gpt-6-astra |
| API providers | 37 (best) | 24 | 37 (best) |
| Released | Sep 1, 2026 | Oct 13, 2026 | Sep 4, 2026 |
| Knowledge cutoff | Jun 2026 | Mar 2026 | Apr 30, 2026 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Claude Fable 5.1$200.00
- Gemini 4 Argon$40.00
- GPT-6 Astra$200.00
Which should you choose?
Which is better: Claude Fable 5.1, Gemini 4 Argon or GPT-6 Astra?
Gemini 4 Argon is the better all-round choice, scoring 74/100 against GPT-6 Astra (68) and Claude Fable 5.1 (66). It leads on price and inputs & features. GPT-6 Astra wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Claude Fable 5.1, Gemini 4 Argon or GPT-6 Astra?
Gemini 4 Argon is cheaper at $2.00 input / $10.00 output per million tokens (official Google API price). Claude Fable 5.1 costs $10.00 input / $50.00 output per million tokens (official Anthropic API price); GPT-6 Astra costs $10.00 input / $50.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $4.00 per million tokens for Gemini 4 Argon versus $20.00 for Claude Fable 5.1 (5× as much) and $20.00 for GPT-6 Astra (5× as much).
Which scores higher on benchmarks?
GPT-6 Astra scores higher on the Capabilities Index (ECI): GPT-6 Astra 169.1 (#1 of 165), Claude Fable 5.1 166.4 (#6 of 165) and Gemini 4 Argon 166.1 (#7 of 165). The confidence ranges of the top two overlap (165.9–174.3 vs 163.6–170.8), so treat the gap as small. On individual benchmarks: FrontierMath Tiers 1–3 — GPT-6 Astra 93.7%, Claude Fable 5.1 90.2%, Gemini 4 Argon 86.0%; OTIS Mock AIME 2024–2025 — Claude Fable 5.1 100%, Gemini 4 Argon 100%, GPT-6 Astra 100%; SimpleQA Verified — Gemini 4 Argon 76.0%, GPT-6 Astra 75.6%, Claude Fable 5.1 70.8%.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Fable 5.1, Gemini 4 Argon and GPT-6 Astra yet, so there is no like-for-like coding score. On overall capability, GPT-6 Astra leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
GPT-6 Astra and Gemini 4 Argon have the largest context windows (1,050,000 and 1,048,576 tokens), against 1,000,000 for Claude Fable 5.1. Maximum output per response: Claude Fable 5.1 up to 128,000, Gemini 4 Argon up to 65,536, GPT-6 Astra up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Claude Fable 5.1 accepts text, images and PDFs; Gemini 4 Argon accepts text, images, PDFs, audio and video; GPT-6 Astra accepts text, images and PDFs. Gemini 4 Argon handles the widest range of inputs.
Are any of these open source?
No. Claude Fable 5.1, Gemini 4 Argon and GPT-6 Astra are proprietary and only available through APIs and apps.
Which is newer?
Gemini 4 Argon is the newest, released Oct 13, 2026. GPT-6 Astra came out Sep 4, 2026; Claude Fable 5.1 came out Sep 1, 2026. Knowledge cutoff: Claude Fable 5.1 Jun 2026, Gemini 4 Argon Mar 2026, GPT-6 Astra Apr 30, 2026.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Nov 2, 2026.
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