# DeepSeek V4.1 Flash vs Mellum2.1-12B-A2.5B-Thinking

> Side-by-side benchmark comparison for DeepSeek V4.1 Flash and Mellum2.1-12B-A2.5B-Thinking across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/deepseek-v4-1-flash-vs-mellum2-1-12b-a2-5b-thinking
- Last updated: October 8, 2026

- Shared sourced benchmarks: 2
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Evidence is too thin for a benchmark verdict: DeepSeek V4.1 Flash and Mellum2.1-12B-A2.5B-Thinking share only 2 sourced benchmark rows.

## Summary

- Only 2 shared sourced benchmark rows are available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Mellum2.1-12B-A2.5B-Thinking has the lower published output-token price.
- DeepSeek V4.1 Flash has the larger published context window at 1M.

## Model Snapshot

| Property | DeepSeek V4.1 Flash | Mellum2.1-12B-A2.5B-Thinking |
|----------|----------|----------|
| Creator | DeepSeek | JetBrains |
| Type | Open Weight | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 128K |
| Independent public score (not head-to-head) | 67.79 | null |
| Benchmarks Covered | 27 | 7 |
| Pricing (input/output) | $0.30 / $1.20 | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- DeepSeek V4.1 Flash public-lane score: 61.1 (Supported · #21/122)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | DeepSeek V4.1 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.1 | 90.6% | 17.4% | DeepSeek V4.1 Flash |
| terminalBench3 | 30% | Coming soon | Coming soon |
| Terminal-Bench 4.0 | 31.20% | Coming soon | Coming soon |
| CyberGym | 88.1% | Coming soon | Coming soon |
| ExploitGym | 15.3% | Coming soon | Coming soon |
| HLE w/ tools | 63.9% | Coming soon | Coming soon |
| AutomationBench | 54.8% | Coming soon | Coming soon |
| Agents' Last Exam | 31.8% | Coming soon | Coming soon |
| Terminal-Bench 2.1 (Vals) | 74.5% | Coming soon | Coming soon |
| CWE-bench v1 | 55.0% | Coming soon | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- DeepSeek V4.1 Flash public-lane score: 62 (Supported · #16/146)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | DeepSeek V4.1 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| Codeforces | 3471.0 | Coming soon | Coming soon |
| Terminal-Bench 2.1 | 90.6% | Coming soon | Coming soon |
| terminalBench3 | 30% | Coming soon | Coming soon |
| DeepSWE | 74.2% | Coming soon | Coming soon |
| ProgramBench | 20.3% | Coming soon | Coming soon |
| NL2Repo | 65.4% | Coming soon | Coming soon |
| OpenHarmony Bench | 60.3% | Coming soon | Coming soon |
| Bug Hunt Bench | 21.7 fixes | Coming soon | Coming soon |
| LiveCodeBench v6 | Coming soon | 82.0% | Coming soon |
| SWE-bench Verified | Coming soon | 47% | Coming soon |
| SWE-bench Pro | Coming soon | 28% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- DeepSeek V4.1 Flash public-lane score: 79.6 (Unranked · 4 rankable rows)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | DeepSeek V4.1 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| JevBench 1.4 | 4.77 | Coming soon | Coming soon |
| JevBench 1.5 | 6.65 | Coming soon | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- DeepSeek V4.1 Flash public-lane score: 74.5 (Unranked · 1 rankable row)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | DeepSeek V4.1 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| Chartography (tools) | 78.9% | Coming soon | Coming soon |
| BabyVision w/ Python | 89.6% | Coming soon | Coming soon |
| ZeroBench w/ Python | 49.0% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- DeepSeek V4.1 Flash public-lane score: 64.4 (Supported · #26/174)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | DeepSeek V4.1 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 90.9% | Coming soon | Coming soon |
| GPQA-D | 90.9% | 64.6% | DeepSeek V4.1 Flash |
| HLE | 36.8% | Coming soon | Coming soon |
| MMLU-Redux | Coming soon | 87.8% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- DeepSeek V4.1 Flash public-lane score: Coming soon
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | DeepSeek V4.1 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| IFEval | Coming soon | 90.6% | Coming soon |

### Mathematics

- Winner: Insufficient shared evidence
- DeepSeek V4.1 Flash public-lane score: Coming soon
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | DeepSeek V4.1 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| Apex | 65.6% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between DeepSeek V4.1 Flash and Mellum2.1-12B-A2.5B-Thinking?

Not yet. The models share only 2 sourced benchmark rows, 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

- [DeepSeek V4.1 Flash vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-deepseek-v4-1-flash)
- [Mellum2.1-12B-A2.5B-Thinking vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-mellum2-1-12b-a2-5b-thinking)
- [DeepSeek V4.1 Flash vs GPT-6 Astra](/compare/deepseek-v4-1-flash-vs-gpt-6-astra)
- [Mellum2.1-12B-A2.5B-Thinking vs GPT-6 Astra](/compare/gpt-6-astra-vs-mellum2-1-12b-a2-5b-thinking)

## Explore More

- [DeepSeek V4.1 Flash profile](/models/deepseek-v4-1-flash)
- [Mellum2.1-12B-A2.5B-Thinking profile](/models/mellum2-1-12b-a2-5b-thinking)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)