# Mellum2-12B-A2.5B-Instruct vs Spark-X2.6-4B

> Side-by-side benchmark comparison for Mellum2-12B-A2.5B-Instruct and Spark-X2.6-4B across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/mellum2-12b-a2-5b-instruct-vs-spark-x2-6-4b
- Last updated: October 20, 2026

- Shared sourced benchmarks: 4
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Mellum2-12B-A2.5B-Instruct leads by point estimate. Conditional score ranges do not establish rank confidence. Choose using the category evidence and your own workload tests.

## Summary

- Mellum2-12B-A2.5B-Instruct has the higher overall point estimate 51 to 40.14. Conditional score ranges do not establish rank confidence.
- The biggest single benchmark swing is GPQA-D in Knowledge, with scores of 40.9% and 77.1%.
- Spark-X2.6-4B also has the larger context window at 1M.

## Model Snapshot

| Property | Mellum2-12B-A2.5B-Instruct | Spark-X2.6-4B |
|----------|----------|----------|
| Creator | JetBrains | SparkLLM |
| Type | Open Weight | Open Weight |
| Reasoning | Non-Reasoning | Reasoning |
| Context | 128K | 1M |
| Overall Score | null | 40.14 |
| Benchmarks Covered | 6 | 20 |
| Pricing (input/output) | N/A | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Not comparable
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon
- Spark-X2.6-4B public-lane score: 33 (Estimated · #89/131)

| Benchmark | Mellum2-12B-A2.5B-Instruct | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| BFCL v4 | 44.2% | 71.8% | Spark-X2.6-4B |
| τ²-bench results | Coming soon | 86.9% | Coming soon |
| MCP Atlas | Coming soon | 62.4% | Coming soon |
| BrowseComp | Coming soon | 53.1% | Coming soon |
| HLE w/ tools | Coming soon | 36.9% | Coming soon |
| τ³-bench results | Coming soon | 34.7% | Coming soon |
| Claw-Eval | Coming soon | 69.9% | Coming soon |

### Coding

- Winner: Not comparable
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon
- Spark-X2.6-4B public-lane score: 30.6 (Estimated · #95/152)

| Benchmark | Mellum2-12B-A2.5B-Instruct | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| LiveCodeBench v6 | 37.2% | Coming soon | Coming soon |
| SWE-bench Pro | Coming soon | 54.3% | Coming soon |
| SWE-bench Verified | Coming soon | 62.8% | Coming soon |
| SWE Multilingual | Coming soon | 64.7% | Coming soon |
| SciCode | Coming soon | 36.8% | Coming soon |

### Reasoning

- Winner: Not comparable
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon
- Spark-X2.6-4B public-lane score: 48.8 (Unranked · 2 rankable rows)

| Benchmark | Mellum2-12B-A2.5B-Instruct | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| LongBench v2 | Coming soon | 53.3% | Coming soon |

### Knowledge

- Winner: Not comparable
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon
- Spark-X2.6-4B public-lane score: 43 (Estimated · #109/187)

| Benchmark | Mellum2-12B-A2.5B-Instruct | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| MMLU-Redux | 78.1% | Coming soon | Coming soon |
| GPQA | 40.9% | 69.9% | Spark-X2.6-4B |
| GPQA-D | 40.9% | 77.1% | Spark-X2.6-4B |
| HLE w/o tools | Coming soon | 17.9% | Coming soon |

### Instruction Following

- Winner: Not comparable
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon
- Spark-X2.6-4B public-lane score: 78.2 (#62/149)

| Benchmark | Mellum2-12B-A2.5B-Instruct | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| IFEval | 75.8% | 93.6% | Spark-X2.6-4B |
| IFBench | Coming soon | 75.8% | Coming soon |

### Mathematics

- Winner: Not comparable
- Mellum2-12B-A2.5B-Instruct public-lane score: Coming soon
- Spark-X2.6-4B public-lane score: 76.4 (Unranked · 3 rankable rows)

| Benchmark | Mellum2-12B-A2.5B-Instruct | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| AIME26 | Coming soon | 91.2% | Coming soon |
| HMMT Feb 2026 | Coming soon | 81.3% | Coming soon |
| IMOAnswerBench | Coming soon | 75.2% | Coming soon |

## FAQ

### Which is better overall, Mellum2-12B-A2.5B-Instruct or Spark-X2.6-4B?

Mellum2-12B-A2.5B-Instruct has the higher overall point estimate. Conditional score ranges do not establish rank confidence.

### How many benchmarks does Mellum2-12B-A2.5B-Instruct cover on BenchLM?

Mellum2-12B-A2.5B-Instruct currently has 6 sourced benchmark scores on BenchLM.

### How many benchmarks does Spark-X2.6-4B cover on BenchLM?

Spark-X2.6-4B currently has 20 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Mellum2-12B-A2.5B-Instruct vs Mellum2-12B-A2.5B-Thinking](/compare/mellum2-12b-a2-5b-instruct-vs-mellum2-12b-a2-5b-thinking)
- [Spark-X2.6-4B vs Mellum2-12B-A2.5B-Thinking](/compare/mellum2-12b-a2-5b-thinking-vs-spark-x2-6-4b)
- [Mellum2-12B-A2.5B-Instruct vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-mellum2-12b-a2-5b-instruct)
- [Spark-X2.6-4B vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-spark-x2-6-4b)

## Explore More

- [Mellum2-12B-A2.5B-Instruct profile](/models/mellum2-12b-a2-5b-instruct)
- [Spark-X2.6-4B profile](/models/spark-x2-6-4b)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)