LLM Reference

Claude Fable 5 vs Gemini 3.1 Pro Preview

Claude Fable 5 (2026) and Gemini 3.1 Pro Preview (2026) are frontier reasoning models from Anthropic and Google DeepMind. Claude Fable 5 ships a 1m-token context window, while Gemini 3.1 Pro Preview ships a 1m-token context window. On SWE-bench Verified, Claude Fable 5 leads by 15.4 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.

Claude Fable 5 is safer overall; choose Gemini 3.1 Pro Preview when coding workflow support matters.

Decision scorecard

Local evidence first
SignalClaude Fable 5Gemini 3.1 Pro Preview
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentsmultimodal apps, tool-calling agents, and long-context analysis
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window1m1m
Cheapest output$50/1M tokens$12/1M tokens
Provider routes8 tracked5 tracked
Shared benchmarksSWE-bench Verified leader2 shared

Decision tradeoffs

Choose Claude Fable 5 when...
  • Claude Fable 5 holds a shared-benchmark lead on SWE-bench Verified, ahead by 15.4 points.
  • Claude Fable 5 has broader tracked provider coverage for fallback and route flexibility.
  • Claude Fable 5 uniquely exposes Reasoning in local model data.
  • Local decision data tags Claude Fable 5 for Coding, RAG, and Agents.
Choose Gemini 3.1 Pro Preview when...
  • Gemini 3.1 Pro Preview has the lower cheapest tracked output price at $12/1M tokens.
  • Gemini 3.1 Pro Preview uniquely exposes Code execution in local model data.
  • Local decision data tags Gemini 3.1 Pro Preview for Coding, RAG, and Agents.

Monthly cost at traffic

Estimate token spend from the cheapest tracked input and output route or tier on this page.

Lower estimate Gemini 3.1 Pro Preview

Claude Fable 5

$20,500

Cheapest tracked route/tier: Anthropic

Gemini 3.1 Pro Preview

$4,600

Cheapest tracked route/tier: Google AI Studio

Estimated monthly gap: $15,900. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Fable 5 -> Gemini 3.1 Pro Preview
  • Provider overlap exists on GCP Vertex AI, OpenRouter, and Replicate API; start route-level A/B tests there.
  • Gemini 3.1 Pro Preview is $38/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Reasoning before moving production traffic.
  • Gemini 3.1 Pro Preview adds Code execution in local capability data.
Gemini 3.1 Pro Preview -> Claude Fable 5
  • Provider overlap exists on GCP Vertex AI, OpenRouter, and Vercel AI Gateway; start route-level A/B tests there.
  • Claude Fable 5 is $38/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Check replacement coverage for Code execution before moving production traffic.
  • Claude Fable 5 adds Reasoning in local capability data.

Specs

Specification
Released2026-06-092026-02-19
Context window1m1m
Parameters——
ArchitectureDecoder OnlyDecoder Only
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff-2025-01

Pricing and availability

Pricing attributeClaude Fable 5Gemini 3.1 Pro Preview
Input price$10/1M tokens
0-200,001t
$2/1M tokens
200,001t+
$4/1M tokens
Output price$50/1M tokens
0-200,001t
$12/1M tokens
200,001t+
$18/1M tokens
Providers
AnthropicAWS BedrockGCP Vertex AIMicrosoft FoundryOpenRouterVercel AI Gateway
Google AI StudioGCP Vertex AIOpenRouterReplicate APIVercel AI Gateway

Capabilities

CapabilityClaude Fable 5Gemini 3.1 Pro Preview
VisionYesYes
MultimodalYesYes
ReasoningYesNo
JSON / Tool useYesYes
Structured outputsYesYes
Code executionNoYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkClaude Fable 5Gemini 3.1 Pro Preview
SWE-bench Verified96.080.6
SWE-bench Pro80.354.2

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Last reviewed: 2026-07-26. Data sourced from public model cards and provider documentation.