# Claude Mythos 5.1 vs DeepSeek V4.1 Flash

> Side-by-side benchmark comparison for Claude Mythos 5.1 and DeepSeek V4.1 Flash across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-mythos-5-1-vs-deepseek-v4-1-flash
- Last updated: September 10, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Evidence is too thin for a benchmark verdict: Claude Mythos 5.1 and DeepSeek V4.1 Flash share only 1 sourced benchmark row.

## Summary

- Only 1 shared sourced benchmark row is available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Claude Mythos 5.1 has the lower published output-token price.

## Model Snapshot

| Property | Claude Mythos 5.1 | DeepSeek V4.1 Flash |
|----------|----------|----------|
| Creator | Anthropic | DeepSeek |
| Type | Proprietary | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 1M |
| Independent public score (not head-to-head) | null | null |
| Benchmarks Covered | 1 | 21 |
| Pricing (input/output) | Pricing unavailable / Pricing unavailable | $0.30 / $1.20 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- DeepSeek V4.1 Flash public-lane score: Coming soon

| Benchmark | Claude Mythos 5.1 | DeepSeek V4.1 Flash | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 4.0 | 60.90% | 31.20% | Claude Mythos 5.1 |
| Terminal-Bench 2.1 | Coming soon | 90.6% | Coming soon |
| terminalBench3 | Coming soon | 30% | Coming soon |
| CyberGym | Coming soon | 88.1% | Coming soon |
| ExploitGym | Coming soon | 15.3% | Coming soon |
| HLE w/ tools | Coming soon | 63.9% | Coming soon |
| AutomationBench | Coming soon | 54.8% | Coming soon |
| Agents' Last Exam | Coming soon | 31.8% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- DeepSeek V4.1 Flash public-lane score: Coming soon

| Benchmark | Claude Mythos 5.1 | DeepSeek V4.1 Flash | Winner |
|-----------|-----------|-----------|--------|
| Codeforces | Coming soon | 3471.0 | Coming soon |
| Terminal-Bench 2.1 | Coming soon | 90.6% | Coming soon |
| terminalBench3 | Coming soon | 30% | Coming soon |
| DeepSWE | Coming soon | 74.2% | Coming soon |
| ProgramBench | Coming soon | 20.3% | Coming soon |
| NL2Repo | Coming soon | 65.4% | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- DeepSeek V4.1 Flash public-lane score: Coming soon

| Benchmark | Claude Mythos 5.1 | DeepSeek V4.1 Flash | Winner |
|-----------|-----------|-----------|--------|
| Chartography (tools) | Coming soon | 78.9% | Coming soon |
| BabyVision w/ Python | Coming soon | 89.6% | Coming soon |
| ZeroBench w/ Python | Coming soon | 49.0% | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- DeepSeek V4.1 Flash public-lane score: Coming soon

| Benchmark | Claude Mythos 5.1 | DeepSeek V4.1 Flash | Winner |
|-----------|-----------|-----------|--------|
| GPQA | Coming soon | 90.9% | Coming soon |
| GPQA-D | Coming soon | 90.9% | Coming soon |
| HLE | Coming soon | 36.8% | Coming soon |

### Mathematics

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- DeepSeek V4.1 Flash public-lane score: Coming soon

| Benchmark | Claude Mythos 5.1 | DeepSeek V4.1 Flash | Winner |
|-----------|-----------|-----------|--------|
| Apex | Coming soon | 65.6% | Coming soon |

## FAQ

### Is there enough evidence to pick between Claude Mythos 5.1 and DeepSeek V4.1 Flash?

Not yet. The models share only 1 sourced benchmark row, so this mirror reports the available measurements and metadata without naming a broad winner.

### What can I compare safely on this page?

Published pricing, context windows, model type, and individual shared benchmark rows are directly comparable. Independent overall scores and non-overlapping benchmark coverage are labeled separately and should not be read as a controlled head-to-head result.

## Related Comparisons

- [Claude Mythos 5.1 vs Claude Mythos 5](/compare/claude-mythos-5-vs-claude-mythos-5-1)
- [DeepSeek V4.1 Flash vs Claude Mythos 5](/compare/claude-mythos-5-vs-deepseek-v4-1-flash)
- [Claude Mythos 5.1 vs Claude Mythos Preview](/compare/claude-mythos-5-1-vs-claude-mythos-preview)
- [DeepSeek V4.1 Flash vs Claude Mythos Preview](/compare/claude-mythos-preview-vs-deepseek-v4-1-flash)

## Explore More

- [Claude Mythos 5.1 profile](/models/claude-mythos-5-1)
- [DeepSeek V4.1 Flash profile](/models/deepseek-v4-1-flash)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)