# Gemini 3.8 Flash vs GPT-5.6 Luna

> Side-by-side benchmark comparison for Gemini 3.8 Flash and GPT-5.6 Luna across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gemini-3-8-flash-vs-gpt-5-6-luna
- Last updated: October 17, 2026

- Shared sourced benchmarks: 17
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Pick Gemini 3.8 Flash if you want the stronger benchmark profile. GPT-5.6 Luna only makes more sense when its price, context window, or workload-specific category wins matter more than the overall score.

## Summary

- Gemini 3.8 Flash leads overall 69.25 to 64.35.
- The clearest category separation is in reasoning, where the averages are 74.3 for Gemini 3.8 Flash and 58.2 for GPT-5.6 Luna.
- The biggest single benchmark swing is FrontierMath v2 (Tier 4) in Mathematics, with scores of 21.951% and 58.500%.
- GPT-5.6 Luna 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 | Gemini 3.8 Flash | GPT-5.6 Luna |
|----------|----------|----------|
| Creator | Google | OpenAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 1.05M |
| Overall Score | 69.25 | 64.35 |
| Benchmarks Covered | 31 | 32 |
| Pricing (input/output) | $0.75 / $3.75 | $0.20 / $1.20 |

## Category Breakdown

### Agentic

- Winner: Gemini 3.8 Flash
- Gemini 3.8 Flash public-lane score: 65.9 (Supported · #16/128)
- GPT-5.6 Luna public-lane score: 56 (Supported · #39/128)

| Benchmark | Gemini 3.8 Flash | GPT-5.6 Luna | Winner |
|-----------|-----------|-----------|--------|
| Finance Agent v2 | 61.4% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | 89.4% | 84.7% | Gemini 3.8 Flash |
| Terminal-Bench 4.0 | 19.10% | Coming soon | Coming soon |
| OSWorld 2.0 | 59.0% | 45.6% | Gemini 3.8 Flash |
| Terminal-Bench 2.1 (Vals) | 81.3% | 79.0% | Gemini 3.8 Flash |
| ApprenticeBench | 24% | 7% | Gemini 3.8 Flash |
| Hermes Index | 38.1% | Coming soon | Coming soon |
| Hermes Bench | 62.2% | Coming soon | Coming soon |
| MazeBench | 4% | 0% | Gemini 3.8 Flash |
| Terminal-Bench 3.0 | Coming soon | 14.3% | Coming soon |
| BrowseComp | Coming soon | 83.3% | Coming soon |
| CyberGym | Coming soon | 77.9% | Coming soon |
| ExploitGym | Coming soon | 12.4% | Coming soon |
| Toolathlon | Coming soon | 53.4% | Coming soon |

### Coding

- Winner: GPT-5.6 Luna
- Gemini 3.8 Flash public-lane score: 61 (Supported · #17/150)
- GPT-5.6 Luna public-lane score: 61.6 (Supported · #16/150)

| Benchmark | Gemini 3.8 Flash | GPT-5.6 Luna | Winner |
|-----------|-----------|-----------|--------|
| DeepSWE | 73.8% | 67.2% | Gemini 3.8 Flash |
| Terminal-Bench 2.1 | 89.4% | 84.7% | Gemini 3.8 Flash |
| CursorBench 3.2 | 69.2% | 61.1% | Gemini 3.8 Flash |
| LiveCodeBench (Vals) | 89.5% | Coming soon | Coming soon |
| SWE-bench (Vals) | 80.0% | 93.0% | GPT-5.6 Luna |
| FrontierSWE v2 | 19.6% | Coming soon | Coming soon |
| CursorBench 4.0 | 39.6% | 35.9% | Gemini 3.8 Flash |
| Bug Hunt Bench | 18.0 fixes | Coming soon | Coming soon |
| SWE-bench Pro | Coming soon | 62.7% | Coming soon |
| FrontierCode 1.1 Extended | Coming soon | 55.1% | Coming soon |
| VulcanBench v3 | Coming soon | 85.5% | Coming soon |

### Reasoning

- Winner: Gemini 3.8 Flash
- Gemini 3.8 Flash public-lane score: 74.3 (#17/28)
- GPT-5.6 Luna public-lane score: 58.2 (#27/28)

| Benchmark | Gemini 3.8 Flash | GPT-5.6 Luna | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-1 | 98.50% | 88.00% | Gemini 3.8 Flash |
| ARC-AGI-2 | 89.2% | 59.5% | Gemini 3.8 Flash |
| ARC-AGI-3 | 10.4% | 0.2% | Gemini 3.8 Flash |

### Multimodal & Grounded

- Winner: Directional only
- Gemini 3.8 Flash public-lane score: 87.3 (#9/54)
- GPT-5.6 Luna public-lane score: 79.6 (#19/54)

| Benchmark | Gemini 3.8 Flash | GPT-5.6 Luna | Winner |
|-----------|-----------|-----------|--------|
| CharXiv w/o tools | 86.2% | Coming soon | Coming soon |
| LVBench | 87.1% | Coming soon | Coming soon |
| MMMU-Pro | Coming soon | 78.4% | Coming soon |
| MMMU-Pro w/ Python | Coming soon | 79.5% | Coming soon |

### Knowledge

- Winner: Gemini 3.8 Flash
- Gemini 3.8 Flash public-lane score: 73.5 (Supported · #13/184)
- GPT-5.6 Luna public-lane score: 64.8 (Supported · #37/184)

| Benchmark | Gemini 3.8 Flash | GPT-5.6 Luna | Winner |
|-----------|-----------|-----------|--------|
| HLE-Verified | 54.9% | Coming soon | Coming soon |
| LABBench2 | 86.2% | Coming soon | Coming soon |
| BioMysteryBench (human-solvable) | 88.8% | Coming soon | Coming soon |
| BioMysteryBench (human-difficult) | 56.5% | Coming soon | Coming soon |
| GPQA Diamond (Vals) | 94.4% | 91.7% | Gemini 3.8 Flash |
| MMLU-Pro (Vals) | 90.2% | 86.0% | Gemini 3.8 Flash |
| GPQA | Coming soon | 92.3% | Coming soon |
| GPQA-D | Coming soon | 92.3% | Coming soon |
| HealthBench Professional | Coming soon | 55.7% | Coming soon |
| HealthBench Hard | Coming soon | 32.0% | Coming soon |

### Instruction Following

- Winner: Not comparable
- Gemini 3.8 Flash public-lane score: Coming soon
- GPT-5.6 Luna public-lane score: Coming soon

| Benchmark | Gemini 3.8 Flash | GPT-5.6 Luna | Winner |
|-----------|-----------|-----------|--------|
| Gray Swan IPI (15 attempts) | 5.5% | Coming soon | Coming soon |

### Mathematics

- Winner: Not comparable
- Gemini 3.8 Flash public-lane score: 69.7 (Unranked · 2 rankable rows)
- GPT-5.6 Luna public-lane score: 84 (Unranked · 3 rankable rows)

| Benchmark | Gemini 3.8 Flash | GPT-5.6 Luna | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | 68.421% | 78.600% | GPT-5.6 Luna |
| FrontierMath v2 (Tier 4) | 21.951% | 58.500% | GPT-5.6 Luna |
| FrontierMath (legacy) | Coming soon | 78.6% | Coming soon |

## FAQ

### Which is better overall, Gemini 3.8 Flash or GPT-5.6 Luna?

Gemini 3.8 Flash is ahead overall on BenchLM right now.

### Where is the biggest gap between Gemini 3.8 Flash and GPT-5.6 Luna?

The widest category gap is in reasoning, where the averages are 74.3 for Gemini 3.8 Flash and 58.2 for GPT-5.6 Luna.

### How many benchmarks does Gemini 3.8 Flash cover on BenchLM?

Gemini 3.8 Flash currently has 31 sourced benchmark scores on BenchLM.

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

GPT-5.6 Luna currently has 32 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Gemini 3.8 Flash vs Gemini 3.8 Flash Cyber](/compare/gemini-3-8-flash-vs-gemini-3-8-flash-cyber)
- [GPT-5.6 Luna vs Gemini 3.8 Flash Cyber](/compare/gemini-3-8-flash-cyber-vs-gpt-5-6-luna)
- [Gemini 3.8 Flash vs GPT-5.6 Sol](/compare/gemini-3-8-flash-vs-gpt-5-6-sol)
- [GPT-5.6 Luna vs GPT-5.6 Sol](/compare/gpt-5-6-luna-vs-gpt-5-6-sol)

## Explore More

- [Gemini 3.8 Flash profile](/models/gemini-3-8-flash)
- [GPT-5.6 Luna profile](/models/gpt-5-6-luna)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)