Model comparison
Claude Mythos 5.1 vs DeepSeek V4 Pro
Anthropic against DeepSeek, compared on context, price, and verified benchmark results.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: Medium — see receipts below
Anthropic
Claude Mythos 5.1
Frontier
DeepSeek
DeepSeek V4 Pro
Frontier · Open weights
| Specification | Claude Mythos 5.1 | DeepSeek V4 Pro |
|---|---|---|
| Provider | Anthropic | DeepSeek |
| Tier | Frontier | Frontier |
| Context window | Not verifiedUnverified | 1M |
| Max output | Not verifiedUnverified | 384K |
| Input / 1M tokens | $10 | Winner: $1.32 |
| Output / 1M tokens | $50 | Winner: $3.96 |
| Weights | Closed | Open |
| Parameters | cyber/bio research variant of Fable 5.1 | 1.6T total / 49B active (MoE) |
| Reasoning levels | adaptive | low, high, max |
| Modalities | text, image | text |
| License | Not disclosedUnverified | MIT |
| API model id | claude-mythos-5 | deepseek-v4-pro |
| Released | September 1, 2026 | April 24, 2026 |
| Artificial Analysis Intelligence Index (2026-08-14) | Not verifiedUnverified | 53 |
| SWE-bench Verified (2026-04-24) | Not verifiedUnverified | 80.6 |
| GPQA Diamond (2026-04-24) | Not verifiedUnverified | 90.1 |
| Humanity's Last Exam (2026-04-24) | Not verifiedUnverified | 48.2 |
| MMLU-Pro (2026-04-24) | Not verifiedUnverified | 87.5 |
Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.
Benchmark receipts
- 2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
- 2026-04-24: DeepSeek V4 Pro HF model card (vendor, Think Max, exact match)Real GitHub issue resolution: does the model's patch pass the hidden tests. Comparability: comparable with caveat — Post-audit vendor claims and pre-audit scores sit on different task trust levels; scaffolding (agent harness, compute budget) also dominates results. Never aggregate across scaffolds.
Pricing tiers: Claude Mythos 5.1: Starts at $10/$50 per MTok — priced with Fable 5.1, which shares the same underlying model. API id claude-mythos-5 replaced the deprecated claude-mythos-preview. · DeepSeek V4 Pro: Official peak rates $1.32/$3.96 per MTok; off-peak $0.66/$1.98 (cache-miss). Open weights (MIT). 1.6T/49B active MoE.
Claude Mythos 5.1
Claude Mythos 5.1 is Anthropic's 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 (vetted US organisations, verification programmes); 30-day data retention applies by default. Same underlying model as Fable 5.1 — most teams should just use Fable.
DeepSeek V4 Pro
DeepSeek V4 Pro is the open-weight (MIT) flagship with a 1M-token context at a fraction of frontier API cost.
Best for
- Cost-sensitive hosted agents
- Open-weight deployments
- High-volume coding
Watch out
Self-hosting needs datacentre VRAM; hosted rates vary by provider. Price single-source — verify.
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. These are standard-tier API rates, excluding batch and cache discounts.
Run the model pickerEvidence 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.
- 3/5 core specs verified on both sides — Not published for at least one side: context window, max output.
- No shared named benchmark — No benchmark has been measured on both models.
- Verified within the last 90 days — Newest catalog check was 8 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.
- Claude Mythos 5.1: Anthropic — Claude Mythos (accessed 2026-09-03)
- Claude Mythos 5.1: Anthropic — model deprecations (claude-mythos-5) (accessed 2026-09-03)
- DeepSeek V4 Pro: DeepSeek — V4 news (accessed 2026-08-29)
- DeepSeek V4 Pro: DeepSeek API pricing (accessed 2026-08-29)
Related comparisons
- Claude Fable 5.1 vs Claude Mythos 5.1
- Claude Fable 5.1 vs DeepSeek V4 Pro
- Claude Fable 5 vs Claude Mythos 5.1
- Claude Fable 5 vs DeepSeek V4 Pro
- Claude Haiku 4.5 vs Claude Mythos 5.1
- Claude Mythos 5.1 vs Claude Opus 5
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. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Mythos 5.1 has tiered pricing: Starts at $10/$50 per MTok — priced with Fable 5.1, which shares the same underlying model. API id claude-mythos-5 replaced the deprecated claude-mythos-preview. DeepSeek V4 Pro has tiered pricing: Official peak rates $1.32/$3.96 per MTok; off-peak $0.66/$1.98 (cache-miss). 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. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Mythos 5.1 has tiered pricing: Starts at $10/$50 per MTok — priced with Fable 5.1, which shares the same underlying model. API id claude-mythos-5 replaced the deprecated claude-mythos-preview. DeepSeek V4 Pro has tiered pricing: Official peak rates $1.32/$3.96 per MTok; off-peak $0.66/$1.98 (cache-miss). Open weights (MIT). 1.6T/49B active MoE.
Do Claude Mythos 5.1 and DeepSeek V4 Pro support the same reasoning levels?
Claude Mythos 5.1 exposes adaptive, while DeepSeek V4 Pro exposes low, high, max.
Should I use Claude Mythos 5.1 or DeepSeek V4 Pro?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Mythos 5.1 suits cyber-defence research; DeepSeek V4 Pro suits cost-sensitive hosted agents.
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.
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.