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HEAD TO HEAD · UPDATED NOV 6, 2026
Claude Fable 5.1 vs Gemini 3.8 Flash
Anthropic against Google DeepMind, on sourced numbers only. Green marks the higher (or cheaper) value on each row; the text below only calls a lead when the gap is bigger than measurement noise.
| Claude Fable 5.1 | Gemini 3.8 Flash | |
|---|---|---|
| Arena Elo | 1504 source ↗ | 1496 source ↗ |
| GPQA Diamond | not published | 95.4% source ↗ |
| $ per 1M in / out | $10 / $50 source ↗ | $0.75 / $3.75 source ↗ |
| Blended $ per 1M (3:1) | $20.00 source ↗ | $1.50 source ↗ |
| Context window | 1M source ↗ | 1M source ↗ |
| Output speed | not published | 117 tok/s source ↗ |
| Released | Sep 1, 2026 source ↗ | Sep 2, 2026 source ↗ |
| Open weights | No source ↗ | No source ↗ |
| Reasoning effort tiers | low · medium · high · xhigh · max (default: high) | low · medium · high (default: medium) |
| API effort control | output_config={"effort": "low" | "medium" | "high" | "xhigh" | "max"} source ↗ | thinking_config={"thinking_level": "low" | "medium" | "high"} source ↗ |
| Additional benchmarks | Terminal-Bench 4.0: 55.8% source ↗ GDPval-AA v2.1: 1735 source ↗ AA Intelligence Index v5.0.1: 50 source ↗ | DeepSWE v1.1: 73.7% source ↗ |
| Best for (workload) | Anthropic's most capable generally available model, for demanding reasoning and long-horizon agentic work (Anthropic). source ↗ | 95.4% on GPQA Diamond (Epoch AI) and 117 tok/s output (Artificial Analysis) at a Flash-tier price. source ↗ |
Arena Elo from the arena.ai text leaderboard as of Oct 27, 2026 source ↗. Speed measured by Artificial Analysis and varies by provider.
Which one should I use?
For high-volume work where cost matters most, Gemini 3.8 Flash is about 13.3 times cheaper per token. On release timing, Anthropic is at day 30 of a typical ~15-day gap (PAST TYPICAL GAP), and Google DeepMind is at day 24 of a typical ~32-day gap (MID-CYCLE).
Key differences from the sourced numbers
- Gemini 3.8 Flash is the cheaper option: $1.50 vs $20.00 per 1M tokens at a 3:1 input-to-output mix (about 13.3 times less).
- On the Arena text leaderboard they are close (1504 vs 1496): a gap under 20 points is within the leaderboard's margin of error.
- Claude Fable 5.1 pricing note: Same rate across the full 1M context window.
- Gemini 3.8 Flash pricing note: Until Dec 31, 2026; $1.50 / $7.50 from Jan 1, 2027. No higher rate for long prompts.
Frequently asked questions
Is Claude Fable 5.1 or Gemini 3.8 Flash better?
Gemini 3.8 Flash is the cheaper option: $1.50 vs $20.00 per 1M tokens at a 3:1 input-to-output mix (about 13.3 times less). On the Arena text leaderboard they are close (1504 vs 1496): a gap under 20 points is within the leaderboard's margin of error. Claude Fable 5.1 pricing note: Same rate across the full 1M context window. Gemini 3.8 Flash pricing note: Until Dec 31, 2026; $1.50 / $7.50 from Jan 1, 2027. No higher rate for long prompts.
Which one should I use: Claude Fable 5.1 or Gemini 3.8 Flash?
For high-volume work where cost matters most, Gemini 3.8 Flash is about 13.3 times cheaper per token. On release timing, Anthropic is at day 30 of a typical ~15-day gap (PAST TYPICAL GAP), and Google DeepMind is at day 24 of a typical ~32-day gap (MID-CYCLE).
How much does Claude Fable 5.1 cost compared with Gemini 3.8 Flash?
Claude Fable 5.1 lists at $10 / $50 per 1M input/output tokens ($20.00/1M blended at 3:1). Gemini 3.8 Flash lists at $0.75 / $3.75 per 1M input/output tokens ($1.50/1M blended at 3:1).
Facts checked Nov 5, 2026 against official sources. Every number links to its source. Spotted an error? Email [email protected].