Claude Fable 5 vs Gemini 3.5 Flash
Anthropic's Claude Fable 5 and Google's Gemini 3.5 Flash 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 3.5 Flash is the cheaper option — roughly 5.9x less on a blended workload, and it suits agentic loops and sub-agent fleets. 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 3.5
$1.50 / $9.00
/ 1M tokens (input / output)
Google's most capable Flash model, tuned for the agentic era: sub-agent deployment, multi-step workflows, and rapid coding iterations at scale. Supports search grounding, function calling, structured outputs, and computer use in preview. Note that it is pricier than the Gemini 3 Flash preview it replaced.
Input price
Gemini 3.5 Flash is 85% cheaper than Claude Fable 5 on input tokens.
Output price
Gemini 3.5 Flash is 82% 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 3.5 Flash | Difference |
|---|---|---|---|
| Light — 1M in / 200K out | $20 | $3 | $17 |
| Moderate — 10M in / 2M out | $200 | $33 | $167 |
| Heavy — 100M in / 20M out | $2,000 | $330 | $1,670 |
Specification comparison
| Attribute | Claude Fable 5 | Gemini 3.5 Flash |
|---|---|---|
| Input (/ 1M tokens) | $10.00 | $1.50 |
| Output (/ 1M tokens) | $50.00 | $9.00 |
| 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 | 2025-01 |
| Relative latency | high | low |
| Open weights | No | No |
| API model ID | claude-fable-5 | gemini-3.5-flash |
| Status | stable | stable |
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 3.5 Flash: Flat rate at any context length, unlike Gemini 3.1 Pro's 200K cliff.
Choose Claude Fable 5 if…
- Multi-hour autonomous coding runs
- Large codebase migrations
- Hard scientific workflows
- High-stakes legal and medical analysis
Choose Gemini 3.5 Flash if…
- Sub-agent fleets and orchestration
- Fast coding iteration loops
- Search-grounded answers
- Multimodal ingestion at scale
Frequently asked
Is Claude Fable 5 or Gemini 3.5 Flash cheaper?
Gemini 3.5 Flash is cheaper. On a blended 3:1 input-to-output workload it costs about 5.9x less than Claude Fable 5.
Which has the larger context window, Claude Fable 5 or Gemini 3.5 Flash?
Gemini 3.5 Flash has the larger window at 1.05M tokens versus 1M.
Should I use Claude Fable 5 or Gemini 3.5 Flash?
Pick Claude Fable 5 for long-horizon agentic engineering. Pick Gemini 3.5 Flash for agentic loops and sub-agent fleets. If cost dominates the decision, Gemini 3.5 Flash wins; if you need the capability ceiling, benchmark both on your own evals before committing.