# Gemini 3.8 Flash vs GPT-6 Luna

> Side-by-side benchmark comparison for Gemini 3.8 Flash and GPT-6 Luna across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gemini-3-8-flash-vs-gpt-6-luna
- Last updated: September 22, 2026

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

## Quick Verdict

Evidence is too thin for a benchmark verdict: Gemini 3.8 Flash and GPT-6 Luna 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.
- GPT-6 Luna has the lower published output-token price.
- GPT-6 Luna has the larger published context window at 1.05M.

## Model Snapshot

| Property | Gemini 3.8 Flash | GPT-6 Luna |
|----------|----------|----------|
| Creator | Google | OpenAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 1.05M |
| Independent public score (not head-to-head) | 74.05 | 62.33 |
| Benchmarks Covered | 21 | 7 |
| Pricing (input/output) | $0.75 / $3.75 | $0.10 / $0.50 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Gemini 3.8 Flash public-lane score: 67 (Supported · #12/157)
- GPT-6 Luna public-lane score: 56.7 (Estimated · #35/157)

| Benchmark | Gemini 3.8 Flash | GPT-6 Luna | Winner |
|-----------|-----------|-----------|--------|
| Finance Agent v2 | 61.4% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | 89.4% | Coming soon | Coming soon |
| Terminal-Bench 4.0 | 19.10% | Coming soon | Coming soon |
| OSWorld 2.0 | 59.0% | Coming soon | Coming soon |
| Terminal-Bench 2.1 (Vals) | 81.3% | Coming soon | Coming soon |
| ApprenticeBench | 24% | Coming soon | Coming soon |
| ExploitGym | Coming soon | 11.6% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Gemini 3.8 Flash public-lane score: 67.4 (Supported · #9/159)
- GPT-6 Luna public-lane score: 66.6 (Estimated · #11/159)

| Benchmark | Gemini 3.8 Flash | GPT-6 Luna | Winner |
|-----------|-----------|-----------|--------|
| DeepSWE | 73.8% | 66.6% | Gemini 3.8 Flash |
| Terminal-Bench 2.1 | 89.4% | Coming soon | Coming soon |
| cursorBench32 | 69.2% | Coming soon | Coming soon |
| LiveCodeBench (Vals) | 89.5% | Coming soon | Coming soon |
| SWE-bench (Vals) | 80.0% | Coming soon | Coming soon |
| FrontierSWE v2 | 19.6% | Coming soon | Coming soon |
| cursorBench40 | 39.6% | Coming soon | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- Gemini 3.8 Flash public-lane score: 76.9 (#7/17)
- GPT-6 Luna public-lane score: 78.3 (Unranked · 2 rankable rows)

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Gemini 3.8 Flash public-lane score: 82.9 (#9/50)
- GPT-6 Luna public-lane score: 71.3 (Unranked · 1 rankable row)

| Benchmark | Gemini 3.8 Flash | GPT-6 Luna | Winner |
|-----------|-----------|-----------|--------|
| CharXiv w/o tools | 86.2% | Coming soon | Coming soon |
| LVBench | 87.1% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Gemini 3.8 Flash public-lane score: 74.5 (Supported · #8/189)
- GPT-6 Luna public-lane score: 63.6 (Estimated · #29/189)

| Benchmark | Gemini 3.8 Flash | GPT-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% | Coming soon | Coming soon |
| MMLU-Pro (Vals) | 90.2% | Coming soon | Coming soon |
| HealthBench (raw) | Coming soon | 50.0% | Coming soon |
| HealthBench (length-adjusted) | Coming soon | 54.5% | Coming soon |
| HealthBench Professional | Coming soon | 60.8% | Coming soon |
| HealthBench Professional (raw) | Coming soon | 61.2% | Coming soon |
| HealthBench Hard | Coming soon | 31.4% | Coming soon |

## FAQ

### Is there enough evidence to pick between Gemini 3.8 Flash and GPT-6 Luna?

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 3.8 Flash vs Gemini 3.8 Flash Cyber](/compare/gemini-3-8-flash-vs-gemini-3-8-flash-cyber)
- [GPT-6 Luna vs Gemini 3.8 Flash Cyber](/compare/gemini-3-8-flash-cyber-vs-gpt-6-luna)
- [Gemini 3.8 Flash vs GPT-6 Astra](/compare/gemini-3-8-flash-vs-gpt-6-astra)
- [GPT-6 Luna vs GPT-6 Astra](/compare/gpt-6-astra-vs-gpt-6-luna)

## Explore More

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