# GLM-5.3-Flash vs Mellum2.1-12B-A2.5B-Thinking

> Side-by-side benchmark comparison for GLM-5.3-Flash and Mellum2.1-12B-A2.5B-Thinking across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/glm-5-3-flash-vs-mellum2-1-12b-a2-5b-thinking
- Last updated: October 8, 2026

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

## Quick Verdict

Evidence is too thin for a benchmark verdict: GLM-5.3-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.
- GLM-5.3-Flash has the larger published context window at 1M.

## Model Snapshot

| Property | GLM-5.3-Flash | Mellum2.1-12B-A2.5B-Thinking |
|----------|----------|----------|
| Creator | Z.AI | JetBrains |
| Type | Open Weight | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 128K |
| Independent public score (not head-to-head) | 57.3 | null |
| Benchmarks Covered | 21 | 7 |
| Pricing (input/output) | $0.00 / $0.00 | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GLM-5.3-Flash public-lane score: 55.9 (Supported · #34/122)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | GLM-5.3-Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.1 | 84.3% | 17.4% | GLM-5.3-Flash |
| Toolathlon-Verified | 78.4% | Coming soon | Coming soon |
| AutomationBench | 48.8% | Coming soon | Coming soon |
| Agents' Last Exam | 26.3% | Coming soon | Coming soon |
| HLE w/ tools | 55.3% | Coming soon | Coming soon |
| Terminal-Bench 2.1 (Vals) | 62.9% | Coming soon | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GLM-5.3-Flash public-lane score: 49.6 (Supported · #42/146)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | GLM-5.3-Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.1 | 84.3% | Coming soon | Coming soon |
| DeepSWE | 63.4% | Coming soon | Coming soon |
| NL2Repo | 56.3% | Coming soon | Coming soon |
| LiveCodeBench (Vals) | 80.5% | Coming soon | Coming soon |
| SWE-bench (Vals) | 92.0% | Coming soon | Coming soon |
| OpenHarmony Bench | 57.3% | Coming soon | Coming soon |
| FrontierSWE v2 | 18.1% | Coming soon | Coming soon |
| Bug Hunt Bench | 17.7 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
- GLM-5.3-Flash public-lane score: 77.3 (#11/28)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GLM-5.3-Flash public-lane score: 80.4 (#12/49)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | GLM-5.3-Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| OfficeQA Pro | 62.4% | Coming soon | Coming soon |
| CharXiv | 89.4% | Coming soon | Coming soon |
| Chartography (tools) | 78.0% | Coming soon | Coming soon |
| BabyVision | 53.4% | Coming soon | Coming soon |
| MMVU | 80.5% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- GLM-5.3-Flash public-lane score: 59.3 (Supported · #43/174)
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | GLM-5.3-Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| GPQA Diamond (Vals) | 86.4% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 86.1% | 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
- GLM-5.3-Flash public-lane score: Coming soon
- Mellum2.1-12B-A2.5B-Thinking public-lane score: Coming soon

| Benchmark | GLM-5.3-Flash | Mellum2.1-12B-A2.5B-Thinking | Winner |
|-----------|-----------|-----------|--------|
| IFEval | Coming soon | 90.6% | Coming soon |

## FAQ

### Is there enough evidence to pick between GLM-5.3-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

- [GLM-5.3-Flash vs GLM-5.3](/compare/glm-5-3-vs-glm-5-3-flash)
- [Mellum2.1-12B-A2.5B-Thinking vs GLM-5.3](/compare/glm-5-3-vs-mellum2-1-12b-a2-5b-thinking)
- [GLM-5.3-Flash vs GLM-5.2](/compare/glm-5-2-vs-glm-5-3-flash)
- [Mellum2.1-12B-A2.5B-Thinking vs GLM-5.2](/compare/glm-5-2-vs-mellum2-1-12b-a2-5b-thinking)

## Explore More

- [GLM-5.3-Flash profile](/models/glm-5-3-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)