Claude Mythos Preview vs Gemini 3.1 Flash-Lite

Claude Mythos Preview (2026) and Gemini 3.1 Flash-Lite (2026) are frontier reasoning models from Anthropic and Google DeepMind. Claude Mythos Preview ships a 1m-token context window, while Gemini 3.1 Flash-Lite ships a 1.05m-token context window. On Google-Proof Q&A, Claude Mythos Preview leads by 7.7 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.

Gemini 3.1 Flash-Lite is ~9900% cheaper at $0.25/1M; pay for Claude Mythos Preview only for coding workflow support.

Decision scorecard

Local evidence first
SignalClaude Mythos PreviewGemini 3.1 Flash-Lite
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 window1m1.05m
Cheapest output$125/1M tokens$1.50/1M tokens
Provider routes2 tracked3 tracked
Shared benchmarksGoogle-Proof Q&A leader1 shared

Decision tradeoffs

Choose Claude Mythos Preview when...
  • Claude Mythos Preview holds a shared-benchmark lead on Google-Proof Q&A, ahead by 7.7 points.
  • Claude Mythos Preview uniquely exposes Reasoning in local model data.
  • Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
Choose Gemini 3.1 Flash-Lite when...
  • Gemini 3.1 Flash-Lite has the larger context window for long prompts, retrieval packs, or transcript analysis.
  • Gemini 3.1 Flash-Lite has the lower cheapest tracked output price at $1.50/1M tokens.
  • Gemini 3.1 Flash-Lite has broader tracked provider coverage for fallback and route flexibility.
  • Local decision data tags Gemini 3.1 Flash-Lite 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 Flash-Lite

Claude Mythos Preview

$51,250

Cheapest tracked route/tier: Anthropic

Gemini 3.1 Flash-Lite

$575

Cheapest tracked route/tier: Google AI Studio

Estimated monthly gap: $50,675. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Mythos Preview -> Gemini 3.1 Flash-Lite
  • No overlapping tracked provider route is sourced for Claude Mythos Preview and Gemini 3.1 Flash-Lite; plan for SDK, billing, or endpoint changes.
  • Gemini 3.1 Flash-Lite is $124/1M 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 Flash-Lite -> Claude Mythos Preview
  • No overlapping tracked provider route is sourced for Gemini 3.1 Flash-Lite and Claude Mythos Preview; plan for SDK, billing, or endpoint changes.
  • Claude Mythos Preview is $124/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Claude Mythos Preview adds Reasoning in local capability data.

Specs

Specification
Released2026-05-012026-05-07
Context window1m1.05m
Parameters——
ArchitectureDecoder OnlyDecoder Only
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-122025-01

Pricing and availability

Pricing attributeClaude Mythos PreviewGemini 3.1 Flash-Lite
Input price$25/1M tokens$0.25/1M tokens
Output price$125/1M tokens$1.50/1M tokens
Providers
AnthropicMicrosoft Foundry
Google AI StudioOpenRouterVercel AI Gateway

Capabilities

CapabilityClaude Mythos PreviewGemini 3.1 Flash-Lite
VisionYesYes
MultimodalYesYes
ReasoningYesNo
JSON / Tool useYesYes
Structured outputsYesYes
Code executionYesYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkClaude Mythos PreviewGemini 3.1 Flash-Lite
Google-Proof Q&A94.686.9

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