Claude Fable 5.1 vs Gemini 4 Argon vs Claude Sonnet 5.5
Too close to call on our weighted score (Gemini 4 Argon 74, Claude Sonnet 5.5 72, Claude Fable 5.1 66). The right pick depends on what you value most.
AnthropicClaude Fable 5.1
66/100- ECI166.4
- Price$10.00 / $50.00
- Context1M
GoogleGemini 4 Argon
74/100- ECI166.1
- Price$2.00 / $10.00
- Context1.05M
- Anthropic
Claude Sonnet 5.5
72/100- ECI166.7
- Price$2.00 / $10.00
- Context1M
Too close to call
It is close. Our weighted score puts them within 3 points (Gemini 4 Argon 74/100, Claude Sonnet 5.5 72/100, Claude Fable 5.1 66/100), so choose by what matters most for your work: Claude Sonnet 5.5 for raw capability, Gemini 4 Argon on price and Gemini 4 Argon for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityClaude Sonnet 5.5Capabilities Index (ECI): Claude Sonnet 5.5 166.7 · Claude Fable 5.1 166.4 · Gemini 4 Argon 166.1
- Lowest priceGemini 4 Argon and Claude Sonnet 5.5Gemini 4 Argon $4.00 · Claude Sonnet 5.5 $4.00 · Claude Fable 5.1 $20.00 per 1M tokens (3:1 blend)
- Longest contextGemini 4 ArgonGemini 4 Argon 1,048,576 · Claude Fable 5.1 1,000,000 · Claude Sonnet 5.5 1,000,000 tokens
- Widest inputsGemini 4 ArgonClaude Fable 5.1: Text, Images, PDFs · Gemini 4 Argon: Text, Images, PDFs, Audio, Video · Claude Sonnet 5.5: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Claude Fable 5.1 | Gemini 4 Argon | Claude Sonnet 5.5 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 97 | 96 | 97 |
| Price | 25% | 0 | 20 | 20 |
| Inputs & features | 15% | 80 | 100 | 80 |
| Context window | 10% | 60 | 61 | 60 |
| Overall | 100% | 66/100 | 74/100 | 72/100 |
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 | Claude Sonnet 5.5Anthropic |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 166.4 | 166.1 | 166.7 (best) |
| ECI rank | #6 of 165 | #7 of 165 | #5 of 165 (best) |
| GPQA DiamondGraduate-level science questions | — | 96.4% (best) | 95.6% |
| FrontierMath Tiers 1–3Research-level mathematics | 90.2% (best) | 86.0% | 88.8% |
| OTIS Mock AIME 2024–2025Competition mathematics | 100% | 100% | 100% |
| SimpleQA VerifiedShort factual questions | 70.8% | 76.0% (best) | 46.5% |
| Price per million tokens | |||
| Input | $10.00 | $2.00 (best) | $2.00 (best) |
| Output | $50.00 | $10.00 (best) | $10.00 (best) |
| Cached input | $0.25 | $0.10 (best) | $0.10 (best) |
| Blended (3:1) | $20.00 | $4.00 (best) | $4.00 (best) |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Official Anthropic API | Official Google API | Official Anthropic API |
| Limits | |||
| Context window | 1,000,000 tokens | 1,048,576 tokens (best) | 1,000,000 tokens |
| 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 | claude-sonnet-5-5 |
| API providers | 37 (best) | 24 | 34 |
| Released | Sep 1, 2026 | Oct 13, 2026 | Sep 28, 2026 |
| Knowledge cutoff | Jun 2026 | Mar 2026 | Jun 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
- Claude Sonnet 5.5$40.00
Which should you choose?
Which is better: Claude Fable 5.1, Gemini 4 Argon or Claude Sonnet 5.5?
It is close. Our weighted score puts them within 3 points (Gemini 4 Argon 74/100, Claude Sonnet 5.5 72/100, Claude Fable 5.1 66/100), so choose by what matters most for your work: Claude Sonnet 5.5 for raw capability, Gemini 4 Argon on price and Gemini 4 Argon for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Claude Fable 5.1, Gemini 4 Argon or Claude Sonnet 5.5?
Gemini 4 Argon is cheaper at $2.00 input / $10.00 output per million tokens (official Google API price). Claude Sonnet 5.5 costs $2.00 input / $10.00 output per million tokens (official Anthropic API price); Claude Fable 5.1 costs $10.00 input / $50.00 output per million tokens (official Anthropic 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 $4.00 for Claude Sonnet 5.5 (1× as much) and $20.00 for Claude Fable 5.1 (5× as much).
Which scores higher on benchmarks?
Claude Sonnet 5.5 scores higher on the Capabilities Index (ECI): Claude Sonnet 5.5 166.7 (#5 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 (163.6–171.3 vs 163.6–170.8), so treat the gap as small. On individual benchmarks: FrontierMath Tiers 1–3 — Claude Fable 5.1 90.2%, Claude Sonnet 5.5 88.8%, Gemini 4 Argon 86.0%; OTIS Mock AIME 2024–2025 — Claude Fable 5.1 100%, Gemini 4 Argon 100%, Claude Sonnet 5.5 100%; SimpleQA Verified — Gemini 4 Argon 76.0%, Claude Fable 5.1 70.8%, Claude Sonnet 5.5 46.5%.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Fable 5.1, Gemini 4 Argon and Claude Sonnet 5.5 yet, so there is no like-for-like coding score. On overall capability, Claude Sonnet 5.5 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?
Gemini 4 Argon has the largest context window at 1,048,576 tokens, against 1,000,000 for Claude Fable 5.1 and 1,000,000 for Claude Sonnet 5.5. Maximum output per response: Claude Fable 5.1 up to 128,000, Gemini 4 Argon up to 65,536, Claude Sonnet 5.5 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; Claude Sonnet 5.5 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 Claude Sonnet 5.5 are proprietary and only available through APIs and apps.
Which is newer?
Gemini 4 Argon is the newest, released Oct 13, 2026. Claude Sonnet 5.5 came out Sep 28, 2026; Claude Fable 5.1 came out Sep 1, 2026. Knowledge cutoff: Claude Fable 5.1 Jun 2026, Gemini 4 Argon Mar 2026, Claude Sonnet 5.5 Jun 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.
