# Gemini 1.5 Flash vs Mellum2.1-12B-A2.5B-Thinking

> Side-by-side benchmark comparison for Gemini 1.5 Flash and Mellum2.1-12B-A2.5B-Thinking across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gemini-1-5-flash-vs-mellum2-1-12b-a2-5b-thinking
- Last updated: October 14, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Evidence is too thin for a benchmark verdict: Gemini 1.5 Flash and Mellum2.1-12B-A2.5B-Thinking 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.
- Gemini 1.5 Flash has the larger published context window at 1M.

## Model Snapshot

| Property | Gemini 1.5 Flash | Mellum2.1-12B-A2.5B-Thinking |
|----------|----------|----------|
| Creator | Google | JetBrains |
| Type | Proprietary | Open Weight |
| Reasoning | Non-Reasoning | Reasoning |
| Context | 1M | 128K |
| Independent public score (not head-to-head) | null | null |
| Benchmarks Covered | 5 | 7 |
| Pricing (input/output) | N/A | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Gemini 1.5 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.1 | Coming soon | 17.4% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Gemini 1.5 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Verified | 9.6% | 47% | Mellum2.1-12B-A2.5B-Thinking |
| LiveCodeBench v6 | Coming soon | 82.0% | Coming soon |
| SWE-bench Pro | Coming soon | 28% | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Gemini 1.5 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| MMMU | 58.3% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Gemini 1.5 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 50% | Coming soon | Coming soon |
| SimpleQA | 8.6% | Coming soon | Coming soon |
| MMLU-Redux | Coming soon | 87.8% | Coming soon |
| GPQA-D | Coming soon | 64.6% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Gemini 1.5 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| IFEval | Coming soon | 90.6% | Coming soon |

### Mathematics

- Winner: Insufficient shared evidence
- Gemini 1.5 Flash public-lane score: Coming soon
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | Gemini 1.5 Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| AIME 2025 | 14.7% | Coming soon | Coming soon |

## FAQ

### Is there enough evidence to pick between Gemini 1.5 Flash and Mellum2.1-12B-A2.5B-Thinking?

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

- [Gemini 1.5 Flash vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-gemini-1-5-flash)
- [Mellum2.1-12B-A2.5B-Thinking vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-mellum2-1-12b-a2-5b-thinking)
- [Gemini 1.5 Flash vs GPT-6.1 Sol](/compare/gemini-1-5-flash-vs-gpt-6-1-sol)
- [Mellum2.1-12B-A2.5B-Thinking vs GPT-6.1 Sol](/compare/gpt-6-1-sol-vs-mellum2-1-12b-a2-5b-thinking)

## Explore More

- [Gemini 1.5 Flash profile](/models/gemini-1-5-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)