Claude Mythos Preview vs DeepSeek V4 Flash

Claude Mythos Preview (2026) and DeepSeek V4 Flash (2026) are frontier-tier reasoning models from Anthropic and DeepSeek. Both ship a 1m-token context window. On SWE-bench Verified, Claude Mythos Preview leads by 14.9 pts. On pricing, Claude Mythos Preview costs $25/1M input tokens; DeepSeek V4 Flash ranges from $0.22 to $0.44/1M input tokens by tier. 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 DeepSeek V4 Flash when provider fit matters.

Decision scorecard

Local evidence first
SignalClaude Mythos PreviewDeepSeek V4 Flash
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentsreasoning-heavy apps, tool-calling agents, and long-context analysis
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window1m1m
Cheapest output$125/1M tokens$0.12/1M tokens
Provider routes2 tracked5 tracked
Shared benchmarksSWE-bench Verified leader2 shared

Decision tradeoffs

Choose Claude Mythos Preview when...
  • Claude Mythos Preview holds a shared-benchmark lead on SWE-bench Verified, ahead by 14.9 points.
  • Claude Mythos Preview uniquely exposes Vision, Multimodal, and Code execution in local model data.
  • Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
Choose DeepSeek V4 Flash when...
  • DeepSeek V4 Flash has the lower cheapest tracked output price at $0.12/1M tokens.
  • DeepSeek V4 Flash has broader tracked provider coverage for fallback and route flexibility.
  • Local decision data tags DeepSeek V4 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 DeepSeek V4 Flash

Claude Mythos Preview

$51,250

Cheapest tracked route/tier: Anthropic

DeepSeek V4 Flash

$76.26

Cheapest tracked route/tier: OpenRouter

Estimated monthly gap: $51,174. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Mythos Preview -> DeepSeek V4 Flash
  • Provider overlap exists on Microsoft Foundry; start route-level A/B tests there.
  • DeepSeek V4 Flash is $125/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Vision, Multimodal, and Code execution before moving production traffic.
DeepSeek V4 Flash -> Claude Mythos Preview
  • Provider overlap exists on Microsoft Foundry; start route-level A/B tests there.
  • Claude Mythos Preview is $125/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Claude Mythos Preview adds Vision, Multimodal, and Code execution in local capability data.

Specs

Specification
Released2026-05-012026-04-24
Context window1m1m
Parameters—284B
ArchitectureDecoder OnlyMixture of Experts
LicenseProprietaryMITOSI-approved
OpennessProprietaryOpen source
WeightsNot releasedAvailable
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: permitted
Knowledge cutoff2025-12-

Pricing and availability

Pricing attributeClaude Mythos PreviewDeepSeek V4 Flash
Input price$25/1M tokens
Off-peak
$0.22/1M tokens
All UTC hours outside DeepSeek's peak windows. Cache-hit input: $0.007 per 1M tokens; cache-miss input: $0.22 per 1M; output: $0.66 per 1M.
Peak
$0.44/1M tokens
01:00-04:00 and 06:00-10:00 UTC. Cache-hit input: $0.014 per 1M tokens; cache-miss input: $0.44 per 1M; output: $1.32 per 1M.
Output price$125/1M tokens
Off-peak
$0.66/1M tokens
All UTC hours outside DeepSeek's peak windows. Cache-hit input: $0.007 per 1M tokens; cache-miss input: $0.22 per 1M; output: $0.66 per 1M.
Peak
$1.32/1M tokens
01:00-04:00 and 06:00-10:00 UTC. Cache-hit input: $0.014 per 1M tokens; cache-miss input: $0.44 per 1M; output: $1.32 per 1M.
Providers
AnthropicMicrosoft Foundry
DeepSeek PlatformOpenRouterMicrosoft FoundryVercel AI GatewayNovita AI

Capabilities

CapabilityClaude Mythos PreviewDeepSeek V4 Flash
VisionYesNo
MultimodalYesNo
ReasoningYesYes
JSON / Tool useYesYes
Structured outputsYesYes
Code executionYesNo
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkClaude Mythos PreviewDeepSeek V4 Flash
SWE-bench Verified93.979.0
Google-Proof Q&A94.688.1

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