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Gemini 3.8 Flash vs Claude Fable 5.1
Claude Fable 5.1 scores higher than Gemini 3.8 Flash on all 5 public leaderboards that rate both. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, Gemini 3.8 Flash is at 50 and Claude Fable 5.1 at 96.3 (out of 100).
Scores as published by each board; table composed September 28, 2026.
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Leaderboard by leaderboard
| Board | Gemini 3.8 Flash | Claude Fable 5.1 | Higher |
|---|---|---|---|
| LMArena Elo (community votes) | 1,580 | 1,751.5 | Claude Fable 5.1 |
| LiveBench global average (0-100) | 75.8 | 83.4 | Claude Fable 5.1 |
| SimpleBench AVG@5 % (private set) | 82.4 | 86.6 | Claude Fable 5.1 |
| Vals AI Vals Index accuracy % · weighted finance + coding tasks | 62.3 | 68.8 | Claude Fable 5.1 |
| Artificial Analysis intelligence index · measured runs only | 40.9 | 53.4 | Claude Fable 5.1 |
Raw scores are each board's own scale, so compare within a row, not across rows. Full table: the bench index.
For coding
On the ArtificialWatch coding index, Gemini 3.8 Flash is at 50 (#15 of 31) and Claude Fable 5.1 at 93.3 (#3). Gemini 3.8 Flash scores higher on 1 of the 3 coding boards that rate both and Claude Fable 5.1 on 2.
| Coding board | Gemini 3.8 Flash | Claude Fable 5.1 |
|---|---|---|
| LMArena · Coding | 1,532.1 | 1,529.1 |
| LiveBench · Coding | 63.4 | 76.2 |
| Vals Vibe Code Bench | 78.7 | 90.3 |
Gemini 3.8 Flash at a glance
- Developer
- Status
- Live since September 2, 2026
- API price
- $0.75 input / $3.75 output per 1M tokens · Google, gemini-3.8-flash
- Context window
- 1.05M tokens
Live — GA Sep 2 · $0.75/$3.75 per 1M introductory through Dec 31, identical to 3.7 · 1M in / 64K out · 'our most intelligent Flash model' · 20 days after 3.7.
Gemini 3.8 Flash is GA — same price as 3.7, twenty days later
2026-09-02 · Google released Gemini 3.8 Flash today. The Gemini API changelog for September 2 reads: "Gemini 3.8 Flash generally available (GA): Released gemini-3.8-flash, our most intelligent Flash model, engineered for long-horizon software engineering, autonomous agents, and complex enterprise workflows."
Claude Fable 5.1 at a glance
- Developer
- Anthropic
- Status
- Live since September 1, 2026
- API price
- $10 input / $50 output per 1M tokens · Anthropic, claude-fable-5-1
- Context window
- 1M tokens
Live - sticker price held at $10/$50, but cache reads cut 75% to $0.25 = ~25% cheaper typical, up to ~45% agentic · 1M ctx · effort low-max.
Claude Fable 5.1 is live — the sticker price never moved, and the cache read fell 75%
2026-09-01 · Claude Fable 5.1 shipped today, alongside Claude Mythos 5.1. Our radar detected it at 17:52:22 UTC and confirmed it on the next sweep 60 seconds later.
Fable 5.1's August window has closed — the market now prices September at 78%, and one claim in the leak can't be checked at all
2026-08-20 · A claim going round today says Fable 5.1 is in pre-release testing, targeted at September, and running inside Anthropic's own products under the Fable 5 name. One part of that is checkable, one part is checkable and slipping, and one part is — by construction — invisible to anything we can measure.
Gemini 3.8 Flash vs Claude Fable 5.1: quick answers
Which is better, Gemini 3.8 Flash or Claude Fable 5.1?
It depends on what you measure. Claude Fable 5.1 scores higher than Gemini 3.8 Flash on all 5 public leaderboards that rate both. Claude Fable 5.1's widest lead is on LiveBench. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, Gemini 3.8 Flash is at 50 and Claude Fable 5.1 at 96.3 (out of 100).
Which is newer, Gemini 3.8 Flash or Claude Fable 5.1?
Gemini 3.8 Flash. It went live on September 2, 2026, 1 day after Claude Fable 5.1 (September 1, 2026).
Which is cheaper, Gemini 3.8 Flash or Claude Fable 5.1?
Gemini 3.8 Flash is cheaper on both input and output. On each vendor's own API, Gemini 3.8 Flash is $0.75 input / $3.75 output per million tokens and Claude Fable 5.1 is $10 input / $50 output per million tokens. Prices as published in the models.dev catalog, as of 2026-09-27.
Which has the bigger context window, Gemini 3.8 Flash or Claude Fable 5.1?
Gemini 3.8 Flash, at 1.05M tokens against Claude Fable 5.1's 1M, as each vendor lists it.
How do Gemini 3.8 Flash and Claude Fable 5.1 compare for coding?
On the ArtificialWatch coding index, Gemini 3.8 Flash is at 50 (#15 of 31) and Claude Fable 5.1 at 93.3 (#3). Gemini 3.8 Flash scores higher on 1 of the 3 coding boards that rate both and Claude Fable 5.1 on 2.
Who makes Gemini 3.8 Flash and Claude Fable 5.1?
Gemini 3.8 Flash is from Google; Claude Fable 5.1 is from Anthropic.
Where do these numbers come from?
Each score is the leaderboard's own published figure, read by ArtificialWatch (table composed September 28, 2026). Boards measure different things, so raw scores are only comparable within a row.
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Also: the bench index · API pricing · the wire