# GPT-5.6 Luna vs Spark-X2.6-4B

> Side-by-side benchmark comparison for GPT-5.6 Luna and Spark-X2.6-4B across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-6-luna-vs-spark-x2-6-4b
- Last updated: October 20, 2026

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

## Quick Verdict

GPT-5.6 Luna leads by point estimate. Conditional score ranges do not establish rank confidence. Choose using the category evidence and your own workload tests.

## Summary

- GPT-5.6 Luna has the higher overall point estimate 64.38 to 40.14. Conditional score ranges do not establish rank confidence.
- The clearest category separation is in coding, where the averages are 61.6 for GPT-5.6 Luna and 30.6 for Spark-X2.6-4B.
- The biggest single benchmark swing is BrowseComp in Agentic, with scores of 83.3% and 53.1%.
- Spark-X2.6-4B is the cheaper option on output tokens, which matters if you expect large responses or heavy interactive use.
- GPT-5.6 Luna also has the larger context window at 1.05M.

## Model Snapshot

| Property | GPT-5.6 Luna | Spark-X2.6-4B |
|----------|----------|----------|
| Creator | OpenAI | SparkLLM |
| Type | Proprietary | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 1.05M | 1M |
| Overall Score | 64.38 | 40.14 |
| Benchmarks Covered | 34 | 20 |
| Pricing (input/output) | $0.20 / $1.20 | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Directional only
- GPT-5.6 Luna public-lane score: 55.9 (Supported · #41/131)
- Spark-X2.6-4B public-lane score: 33 (Estimated · #89/131)

| Benchmark | GPT-5.6 Luna | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 3.0 | 14.3% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | 84.7% | Coming soon | Coming soon |
| BrowseComp | 83.3% | 53.1% | GPT-5.6 Luna |
| OSWorld 2.0 | 45.6% | Coming soon | Coming soon |
| CyberGym | 77.9% | Coming soon | Coming soon |
| ExploitGym | 12.4% | Coming soon | Coming soon |
| Toolathlon | 53.4% | Coming soon | Coming soon |
| Terminal-Bench 2.1 (Vals) | 79.0% | Coming soon | Coming soon |
| ApprenticeBench | 7% | Coming soon | Coming soon |
| MazeBench | 0% | Coming soon | Coming soon |
| BFCL v4 | Coming soon | 71.8% | Coming soon |
| τ²-bench results | Coming soon | 86.9% | Coming soon |
| MCP Atlas | Coming soon | 62.4% | 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: Directional only
- GPT-5.6 Luna public-lane score: 61.6 (Supported · #16/152)
- Spark-X2.6-4B public-lane score: 30.6 (Estimated · #95/152)

| Benchmark | GPT-5.6 Luna | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Pro | 62.7% | 54.3% | GPT-5.6 Luna |
| Terminal-Bench 2.1 | 84.7% | Coming soon | Coming soon |
| DeepSWE | 67.2% | Coming soon | Coming soon |
| FrontierCode 1.1 Extended | 55.1% | Coming soon | Coming soon |
| CursorBench 3.2 | 61.1% | Coming soon | Coming soon |
| VulcanBench v3 | 85.5% | Coming soon | Coming soon |
| SWE-bench (Vals) | 93.0% | Coming soon | Coming soon |
| CursorBench 4.0 | 35.9% | Coming soon | 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
- GPT-5.6 Luna public-lane score: 58.2 (#26/27)
- Spark-X2.6-4B public-lane score: 48.8 (Unranked · 2 rankable rows)

| Benchmark | GPT-5.6 Luna | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-2 | 59.5% | Coming soon | Coming soon |
| ARC-AGI-3 | 0.2% | Coming soon | Coming soon |
| ARC-AGI-1 | 88.00% | Coming soon | Coming soon |
| LongBench v2 | Coming soon | 53.3% | Coming soon |

### Multimodal & Grounded

- Winner: Not comparable
- GPT-5.6 Luna public-lane score: 79.6 (#19/55)
- Spark-X2.6-4B public-lane score: Coming soon

| Benchmark | GPT-5.6 Luna | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| ExtractBench (LlamaIndex) | 91.16% | Coming soon | Coming soon |
| ParseBench | 68.34% | Coming soon | Coming soon |
| MMMU-Pro | 78.4% | Coming soon | Coming soon |
| MMMU-Pro w/ Python | 79.5% | Coming soon | Coming soon |

### Knowledge

- Winner: Directional only
- GPT-5.6 Luna public-lane score: 64.8 (Supported · #38/187)
- Spark-X2.6-4B public-lane score: 43 (Estimated · #109/187)

| Benchmark | GPT-5.6 Luna | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 92.3% | 69.9% | GPT-5.6 Luna |
| GPQA-D | 92.3% | 77.1% | GPT-5.6 Luna |
| HealthBench Professional | 55.7% | Coming soon | Coming soon |
| HealthBench Hard | 32.0% | Coming soon | Coming soon |
| GPQA Diamond (Vals) | 91.7% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 86.0% | Coming soon | Coming soon |
| HLE w/o tools | Coming soon | 17.9% | Coming soon |

### Instruction Following

- Winner: Not comparable
- GPT-5.6 Luna public-lane score: Coming soon
- Spark-X2.6-4B public-lane score: 78.2 (#62/149)

| Benchmark | GPT-5.6 Luna | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| IFEval | Coming soon | 93.6% | Coming soon |
| IFBench | Coming soon | 75.8% | Coming soon |

### Mathematics

- Winner: Not comparable
- GPT-5.6 Luna public-lane score: 84 (Unranked · 3 rankable rows)
- Spark-X2.6-4B public-lane score: 76.4 (Unranked · 3 rankable rows)

| Benchmark | GPT-5.6 Luna | Spark-X2.6-4B | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath (legacy) | 78.6% | Coming soon | Coming soon |
| FrontierMath v2 (Tiers 1-3) | 78.600% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 58.500% | Coming soon | Coming soon |
| 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, GPT-5.6 Luna or Spark-X2.6-4B?

GPT-5.6 Luna has the higher overall point estimate. Conditional score ranges do not establish rank confidence.

### Where is the biggest gap between GPT-5.6 Luna and Spark-X2.6-4B?

The widest category gap is in coding, where the averages are 61.6 for GPT-5.6 Luna and 30.6 for Spark-X2.6-4B.

### How many benchmarks does GPT-5.6 Luna cover on BenchLM?

GPT-5.6 Luna currently has 34 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

- [GPT-5.6 Luna vs GPT-5.6 Sol](/compare/gpt-5-6-luna-vs-gpt-5-6-sol)
- [Spark-X2.6-4B vs GPT-5.6 Sol](/compare/gpt-5-6-sol-vs-spark-x2-6-4b)
- [GPT-5.6 Luna vs GPT-5.6 Terra](/compare/gpt-5-6-luna-vs-gpt-5-6-terra)
- [Spark-X2.6-4B vs GPT-5.6 Terra](/compare/gpt-5-6-terra-vs-spark-x2-6-4b)

## Explore More

- [GPT-5.6 Luna profile](/models/gpt-5-6-luna)
- [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)