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Model comparison

Claude Mythos 5.1 vs DeepSeek V4 Pro

Anthropic against DeepSeek, compared on context, price, and attributed benchmark results.

Recorded profile verification October 1, 2026Individual provider fields may changeEvidence confidence: Medium — see receipts below

Anthropic

Claude Mythos 5.1

Frontier

vs

DeepSeek

DeepSeek V4 Pro

Frontier · Open weights

AI model capability comparison
SpecificationClaude Mythos 5.1DeepSeek V4 Pro
ProviderAnthropicDeepSeek
TierFrontierFrontier
Context window1M1M
Max output128KWinner: 384K
Input / 1M tokens$10Winner: $1.32
Output / 1M tokens$50Winner: $3.96
WeightsClosedOpen
ParametersNot verifiedUnverified1.6T total / 49B active (MoE)
Reasoning levelslow, medium, high, xhigh, maxlow, high, max
Modalitiestext, imagetext
LicenseNot verifiedUnverifiedMIT
API model idclaude-mythos-5-1deepseek-v4-pro
ReleasedSeptember 1, 2026April 24, 2026
Artificial Analysis Intelligence Index [max] · source date DeepSeek V4 Pro: 2026-10-01Not verifiedUnverified36
SWE-bench Verified [max] · source date DeepSeek V4 Pro: 2026-04-24Not verifiedUnverified80.6
GPQA Diamond [max] · source date DeepSeek V4 Pro: 2026-04-24Not verifiedUnverified90.1
Humanity's Last Exam [max] · source date DeepSeek V4 Pro: 2026-04-24Not verifiedUnverified48.2
Humanity's Last Exam · source date DeepSeek V4 Pro: 2026-08-13Not verifiedUnverified42.7
Humanity's Last Exam · source date DeepSeek V4 Pro: 2026-08-13Not verifiedUnverified60
MMLU-Pro [max] · source date DeepSeek V4 Pro: 2026-04-24Not verifiedUnverified87.5
Terminal-Bench 2.1 · source date DeepSeek V4 Pro: 2026-08-13Not verifiedUnverified87.9
DeepSWE 1.1 · source date DeepSeek V4 Pro: 2026-08-13Not verifiedUnverified62.7

Dates beside benchmark scores refer to the linked source’s publication or capture date unless that source explicitly states when it measured the result. A shared URL alone does not establish comparable runs; unverified setups are marked. Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

Where each score comes from, and how far it can be compared across models.

Pricing tiers

Claude Mythos 5.1: Standard $10/$50 per MTok, sharing Fable 5.1's specifications/pricing. Cache reads $0.25; 5-minute writes $12.50 and 1-hour writes $20. Batch $5/$25. US-only inference adds 10% where supported. Invite-only for vetted US organisations; API ID claude-mythos-5-1. Retirement not sooner than September 1, 2027; this is a minimum commitment, not an announced shutdown.

DeepSeek V4 Pro: Official peak rates $1.32/$3.96 per MTok; off-peak $0.66/$1.98 (cache-miss). Cache hit $0.044 peak / $0.022 off-peak. Peak hours are weekdays 01:00–04:00 and 06:00–10:00 UTC, excluding Chinese public holidays; weekends, holidays and all other hours are off-peak. Open weights (MIT). 1.6T/49B active MoE.

FrontierRecord checked October 1, 2026

Claude Mythos 5.1

Anthropic describes Claude Mythos 5.1 as its most capable model for cybersecurity and biology research — the Fable 5.1 model with fewer cyber/bio safeguards, restricted to vetted US organisations.

Best for

  • Cyber-defence research
  • Biology research
  • Claude Security workloads

Watch out

Invite-only for vetted US organisations through trusted access programmes, with 30-day retention required by default for safety monitoring. Adaptive thinking cannot be disabled and forced tool use errors. Shared underlying model does not make Fable benchmark results Mythos observations; safeguards and access differ.

FrontierOpen weightsRecord checked October 1, 2026

DeepSeek V4 Pro

DeepSeek V4 Pro is DeepSeek's large open-weight (MIT) MoE with a 1M-token context — DeepSeek says the cheaper V4.1-Flash now beats it.

Best for

  • Cost-sensitive hosted agents
  • Open-weight deployments
  • High-volume coding

Watch out

The current tariff identifies DeepSeek-V4-Pro-0813. DeepSeek's current changelog reverses the earlier September 14 re-route plan and says it will continue serving V4 Pro at unchanged rates until further notice. Original April benchmark/checkpoint results are not the current 0813 evaluation. Self-hosting memory depends on quantization, offloading and hardware.

When the cheaper one wins

DeepSeek V4 Pro is cheaper on output at $3.96 per million tokens against $50 for Claude Mythos 5.1 — about 13×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. This compares standard short-context token rates, not total cost per accepted task. Include input, cache, context tiers, schedules, retries and review in your pilot.

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Evidence confidence: Medium

How strong and complete the evidence behind this comparison is — not a prediction of which model is better.

  • Pricing verified on both sides — Input and output rates are verified for both models.
  • 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
  • No directly aligned benchmark setup — No benchmark has matching cited sources, source dates, units, effort and recorded run details on both models.
  • Verified within the last 90 days — Older of the two catalog checks was 25 days ago.
  • Both models carry source citations — Each side has at least two catalog sources on record.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

Related comparisons

Diving deeper on one model? Claude Mythos 5.1 · DeepSeek V4 Pro

Common questions

Claude Mythos 5.1 vs DeepSeek V4 Pro

Answered from the verified figures on this page rather than general guidance.

Is Claude Mythos 5.1 or DeepSeek V4 Pro cheaper for input?
DeepSeek V4 Pro is cheaper at $1.32 per million input tokens, against $10 for Claude Mythos 5.1 — roughly 7.6× the price. Estimate both input and output token volume for your workload. These are base rates; Claude Mythos 5.1: Standard $10/$50 per MTok, sharing Fable 5.1's specifications/pricing. Cache reads $0.25; 5-minute writes $12.50 and 1-hour writes $20. Batch $5/$25. US-only inference adds 10% where supported. Invite-only for vetted US organisations; API ID claude-mythos-5-1. Retirement not sooner than September 1, 2027; this is a minimum commitment, not an announced shutdown. DeepSeek V4 Pro: Official peak rates $1.32/$3.96 per MTok; off-peak $0.66/$1.98 (cache-miss). Cache hit $0.044 peak / $0.022 off-peak. Peak hours are weekdays 01:00–04:00 and 06:00–10:00 UTC, excluding Chinese public holidays; weekends, holidays and all other hours are off-peak. Open weights (MIT). 1.6T/49B active MoE.
Is Claude Mythos 5.1 or DeepSeek V4 Pro cheaper for output?
DeepSeek V4 Pro is cheaper at $3.96 per million output tokens, against $50 for Claude Mythos 5.1 — roughly 13× the price. Estimate both input and output token volume for your workload. These are base rates; Claude Mythos 5.1: Standard $10/$50 per MTok, sharing Fable 5.1's specifications/pricing. Cache reads $0.25; 5-minute writes $12.50 and 1-hour writes $20. Batch $5/$25. US-only inference adds 10% where supported. Invite-only for vetted US organisations; API ID claude-mythos-5-1. Retirement not sooner than September 1, 2027; this is a minimum commitment, not an announced shutdown. DeepSeek V4 Pro: Official peak rates $1.32/$3.96 per MTok; off-peak $0.66/$1.98 (cache-miss). Cache hit $0.044 peak / $0.022 off-peak. Peak hours are weekdays 01:00–04:00 and 06:00–10:00 UTC, excluding Chinese public holidays; weekends, holidays and all other hours are off-peak. Open weights (MIT). 1.6T/49B active MoE.
Which has the larger context window, Claude Mythos 5.1 or DeepSeek V4 Pro?
Both accept about 1M tokens of context, so document length will not decide between them.
Do Claude Mythos 5.1 and DeepSeek V4 Pro support the same reasoning levels?
Claude Mythos 5.1 exposes low, medium, high, xhigh, max, while DeepSeek V4 Pro exposes low, high, max.
Should I use Claude Mythos 5.1 or DeepSeek V4 Pro?
Both are classified in our frontier tier; this editorial grouping does not imply equal capability. Claude Mythos 5.1 is a candidate for cyber-defence research; DeepSeek V4 Pro is a candidate for cost-sensitive hosted agents. Compare accuracy, tool reliability, latency and cost on representative tasks.
Can I self-host Claude Mythos 5.1 or DeepSeek V4 Pro?
DeepSeek V4 Pro publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. Claude Mythos 5.1 is a closed model whose supported access paths are controlled by its provider.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

  • Input price: DeepSeek V4 Pro costs $1.32 per 1M tokens versus $10 for Claude Mythos 5.1 — a 7.6x difference at the headline tier.
  • Deployment: DeepSeek V4 Pro publishes weights you can self-host; the other is API-only.
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