Claude Fable 5.1 vs Gemini 3.8 Flash: Specs & Benchmark Comparison
Claude Fable 5.1 is developed by Anthropic, while Gemini 3.8 Flash comes from Google. Both were released in September 2026.
The two models share 3 published benchmarks. Claude Fable 5.1 leads on 3 of them. The widest gaps are on Terminal-Bench 4.0, where Claude Fable 5.1 scores 55.8% against 19.1%; OSWorld 2.0, where Claude Fable 5.1 scores 77.9% against 59.0%. Averaged across everything we track, Claude Fable 5.1 sits at 59.7% and Gemini 3.8 Flash at 59.2%.
Gemini 3.8 Flash is the cheaper API at $0.75 per million input tokens and $3.75 per million output tokens, roughly 13 times cheaper than Claude Fable 5.1 at $10 and $50. Both accept a context window of about 1M tokens. Claude Fable 5.1 accepts text and images as input, while Gemini 3.8 Flash accepts text, images, audio, and video.
| Characteristic | Claude Fable 5.1 | Gemini 3.8 Flash |
|---|---|---|
| Company | Anthropic | |
| Release Date | September 1, 2026 | September 2, 2026 |
| Parameters | — | — |
| Multimodal | Yes | Yes |
| Context (input) | 1.0M | 1.0M |
| Context (output) | 128K | 66K |
| Input Price / 1M | $10.00 | $0.75 |
| Output Price / 1M | $50.00 | $3.75 |
| Average Score | 59.7% | 59.2% |
| Benchmarks | ||
| Terminal-Bench 4.0 | 55.8% | 19.1% |
| OSWorld 2.0 | 77.9% | 59.0% |
| GDPval-AA | 61.8% | 51.5% |
Visual Benchmark Comparison
Verdict
Gemini 3.8 Flash leads in 1 out of 4 comparison categories.
Both models show comparable average scores: Claude Fable 5.1 — 0.6, Gemini 3.8 Flash — 0.6.
Gemini 3.8 Flash is 13.3x cheaper: input $0.75/1M vs $10.00/1M tokens.
Same context size: 1M tokens.
Both models were released around the same time: 9/1/2026 and 9/2/2026.
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Frequently Asked Questions
Which is better for coding — Claude Fable 5.1 or Gemini 3.8 Flash?
Which model is cheaper — Claude Fable 5.1 or Gemini 3.8 Flash?
Which has a larger context window — Claude Fable 5.1 or Gemini 3.8 Flash?
The Claude Fable 5.1 and Gemini 3.8 Flash comparison is updated for 2026. Data includes benchmark results, API pricing, context window size and other specifications. For more detailed information, visit the Claude Fable 5.1 or Gemini 3.8 Flash page. See also the complete list of AI model comparisons.