LLM Reference

Claude Mythos Preview vs Gemini 3 Flash

Claude Mythos Preview (2026) and Gemini 3 Flash (2025) are frontier reasoning models from Anthropic and Google DeepMind. Claude Mythos Preview ships a 1m-token context window, while Gemini 3 Flash ships a 1m-token context window. On SWE-bench Verified, Claude Mythos Preview leads by 15.9 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.

Claude Mythos Preview is safer overall; choose Gemini 3 Flash when coding workflow support matters.

Decision scorecard

Local evidence first
SignalClaude Mythos PreviewGemini 3 Flash
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$125/1M tokens$3/1M tokens
Provider routes2 tracked4 tracked
Shared benchmarksSWE-bench Verified leader3 shared

Decision tradeoffs

Choose Claude Mythos Preview when...
  • Claude Mythos Preview holds a shared-benchmark lead on SWE-bench Verified, ahead by 15.9 points.
  • Claude Mythos Preview uniquely exposes Reasoning and Structured outputs in local model data.
  • Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
Choose Gemini 3 Flash when...
  • Gemini 3 Flash has the lower cheapest tracked output price at $3/1M tokens.
  • Gemini 3 Flash has broader tracked provider coverage for fallback and route flexibility.
  • Local decision data tags Gemini 3 Flash 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 Flash

Claude Mythos Preview

$51,250

Cheapest tracked route/tier: Anthropic

Gemini 3 Flash

$1,150

Cheapest tracked route/tier: Replicate API

Estimated monthly gap: $50,100. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Mythos Preview -> Gemini 3 Flash
  • No overlapping tracked provider route is sourced for Claude Mythos Preview and Gemini 3 Flash; plan for SDK, billing, or endpoint changes.
  • Gemini 3 Flash is $122/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Reasoning and Structured outputs before moving production traffic.
Gemini 3 Flash -> Claude Mythos Preview
  • No overlapping tracked provider route is sourced for Gemini 3 Flash and Claude Mythos Preview; plan for SDK, billing, or endpoint changes.
  • Claude Mythos Preview is $122/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Claude Mythos Preview adds Reasoning and Structured outputs in local capability data.

Specs

Specification
Released2026-05-012025-12-17
Context window1m1m
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 Flash
Input price$25/1M tokens
0-200,001t
$0.50/1M tokens
200,001t+
$0.50/1M tokens
Output price$125/1M tokens
0-200,001t
$3/1M tokens
200,001t+
$3/1M tokens
Providers
AnthropicMicrosoft Foundry
Replicate APIGCP Vertex AIGoogle AI StudioVercel AI Gateway

Capabilities

CapabilityClaude Mythos PreviewGemini 3 Flash
VisionYesYes
MultimodalYesYes
ReasoningYesNo
JSON / Tool useYesYes
Structured outputsYesNo
Code executionYesYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkClaude Mythos PreviewGemini 3 Flash
SWE-bench Verified93.978.0
Google-Proof Q&A94.690.4
τ-bench89.271.5

Continue comparing

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