Claude Fable 5 vs Gemini 3.1 Pro
Anthropic's Claude Fable 5 and Google's Gemini 3.1 Pro both target production language workloads, but they price and behave differently. Here is the side-by-side.
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The short answer
Gemini 3.1 Pro is the cheaper option — roughly 4.4x less on a blended workload, and it suits best price-to-reasoning ratio. Claude Fable 5 justifies its premium when you need long-horizon agentic engineering.
Anthropic • Claude 5
$10.00 / $50.00
/ 1M tokens (input / output)
Anthropic's most capable widely released model, built for agents that run for hours rather than seconds. Adaptive thinking is always on and cannot be disabled, which is part of why it tops the Artificial Analysis Intelligence Index — and why its cost per task runs roughly triple GPT-5.6 Sol's for a one-point intelligence lead.
Google • Gemini 3.1
$2.00 / $12.00
/ 1M tokens (input / output)
Google's shipping flagship while 3.5 Pro remains unreleased, and the cheapest frontier model by a wide margin. It still tops several hard-reasoning boards including GPQA Diamond and ARC-AGI-2, making it the value choice for research-style workloads — provided you keep prompts under 200K tokens, where the price doubles.
Input price
Gemini 3.1 Pro is 80% cheaper than Claude Fable 5 on input tokens.
Output price
Gemini 3.1 Pro is 76% cheaper than Claude Fable 5 on output tokens — usually the side that dominates the bill.
Monthly cost at three workload sizes
Standard (non-batch, non-cached) rates. Reasoning models will exceed these figures because thinking tokens bill as output.
| Workload | Claude Fable 5 | Gemini 3.1 Pro | Difference |
|---|---|---|---|
| Light — 1M in / 200K out | $20 | $4 | $16 |
| Moderate — 10M in / 2M out | $200 | $44 | $156 |
| Heavy — 100M in / 20M out | $2,000 | $440 | $1,560 |
Specification comparison
| Attribute | Claude Fable 5 | Gemini 3.1 Pro |
|---|---|---|
| Input (/ 1M tokens) | $10.00 | $2.00 |
| Output (/ 1M tokens) | $50.00 | $12.00 |
| Cached input | $1.00 | — |
| Context window | 1,000,000 tokens | 1,048,576 tokens |
| Max output | 128,000 tokens | 65,536 tokens |
| Native reasoning | Yes | Yes |
| Knowledge cutoff | 2026-01 | 2025-06 |
| Relative latency | high | medium |
| Open weights | No | No |
| API model ID | claude-fable-5 | gemini-3.1-pro-preview |
| Status | stable | preview |
Claude Fable 5: 5-minute cache writes $12.50/MTok, 1-hour $20/MTok. Requires 30-day data retention, so not available under zero-data-retention terms.
Gemini 3.1 Pro: Prompts over 200K tokens reprice to $4 input / $18 output per 1M.
Choose Claude Fable 5 if…
- Multi-hour autonomous coding runs
- Large codebase migrations
- Hard scientific workflows
- High-stakes legal and medical analysis
Choose Gemini 3.1 Pro if…
- Hard reasoning and research tasks
- Long-context document and video analysis
- Native multimodal pipelines
- Cost-conscious frontier workloads
Frequently asked
Is Claude Fable 5 or Gemini 3.1 Pro cheaper?
Gemini 3.1 Pro is cheaper. On a blended 3:1 input-to-output workload it costs about 4.4x less than Claude Fable 5.
Which has the larger context window, Claude Fable 5 or Gemini 3.1 Pro?
Gemini 3.1 Pro has the larger window at 1.05M tokens versus 1M.
Should I use Claude Fable 5 or Gemini 3.1 Pro?
Pick Claude Fable 5 for long-horizon agentic engineering. Pick Gemini 3.1 Pro for best price-to-reasoning ratio. If cost dominates the decision, Gemini 3.1 Pro wins; if you need the capability ceiling, benchmark both on your own evals before committing.