# GPT-5.6 Luna vs Grok 4.1 Fast

> Side-by-side benchmark comparison for GPT-5.6 Luna and Grok 4.1 Fast across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-6-luna-vs-grok-4-1-fast
- Last updated: September 24, 2026

- Shared sourced benchmarks: 0
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.7

## Quick Verdict

No benchmark verdict yet: there is no shared sourced benchmark row for GPT-5.6 Luna and Grok 4.1 Fast.

## Summary

- GPT-5.6 Luna and Grok 4.1 Fast do not currently share a sourced benchmark row. The mirror therefore compares metadata, pricing, context windows, and each model's separately reported coverage without naming a benchmark winner.

## Model Snapshot

| Property | GPT-5.6 Luna | Grok 4.1 Fast |
|----------|----------|----------|
| Creator | OpenAI | xAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Non-Reasoning |
| Context | 1.05M | 1M |
| Independent public score (not head-to-head) | 65.6 | 36.33 |
| Benchmarks Covered | 29 | 1 |
| Pricing (input/output) | $0.20 / $1.20 | $0.20 / $0.50 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-5.6 Luna public-lane score: 55.3 (Supported · #28/105)
- Grok 4.1 Fast public-lane score: Coming soon

| Benchmark | GPT-5.6 Luna | Grok 4.1 Fast | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 3.0 | 14.3% | Coming soon | Coming soon |
| Terminal-Bench 2.1 | 84.7% | Coming soon | Coming soon |
| BrowseComp | 83.3% | Coming soon | Coming soon |
| 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 |
| Gert Labs | Coming soon | 47.32% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-5.6 Luna public-lane score: 64.5 (Supported · #9/135)
- Grok 4.1 Fast public-lane score: Coming soon

| Benchmark | GPT-5.6 Luna | Grok 4.1 Fast | Winner |
|-----------|-----------|-----------|--------|
| SWE-bench Pro | 62.7% | Coming soon | Coming soon |
| 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 |
| cursorBench32 | 61.1% | Coming soon | Coming soon |
| VulcanBench v3 | 85.5% | Coming soon | Coming soon |
| SWE-bench (Vals) | 93.0% | Coming soon | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- GPT-5.6 Luna public-lane score: 54.7 (#18/19)
- Grok 4.1 Fast public-lane score: 43.6 (Unranked · 2 rankable rows)

| Benchmark | GPT-5.6 Luna | Grok 4.1 Fast | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-2 | 59.5% | Coming soon | Coming soon |
| ARC-AGI-3 | 0.2% | Coming soon | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-5.6 Luna public-lane score: 67.1 (#22/50)
- Grok 4.1 Fast public-lane score: 31.4 (Unranked · 1 rankable row)

| Benchmark | GPT-5.6 Luna | Grok 4.1 Fast | Winner |
|-----------|-----------|-----------|--------|
| MMMU-Pro | 78.4% | Coming soon | Coming soon |
| MMMU-Pro w/ Python | 79.5% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- GPT-5.6 Luna public-lane score: 64.6 (Supported · #22/158)
- Grok 4.1 Fast public-lane score: 32.2 (Estimated · #119/158)

| Benchmark | GPT-5.6 Luna | Grok 4.1 Fast | Winner |
|-----------|-----------|-----------|--------|
| GPQA | 92.3% | Coming soon | Coming soon |
| GPQA-D | 92.3% | Coming soon | Coming soon |
| 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 |

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-5.6 Luna public-lane score: Coming soon
- Grok 4.1 Fast public-lane score: 40.4 (#100/124)

### Mathematics

- Winner: Insufficient shared evidence
- GPT-5.6 Luna public-lane score: 94.2 (Unranked · 3 rankable rows)
- Grok 4.1 Fast public-lane score: Coming soon

| Benchmark | GPT-5.6 Luna | Grok 4.1 Fast | 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 |

## FAQ

### Can I compare GPT-5.6 Luna and Grok 4.1 Fast on BenchLM yet?

Not fully yet. BenchLM is tracking both models, but sourced benchmark coverage is still incomplete for a fair score-level comparison.

### Why does this page show "coming soon" values?

BenchLM only calls winners when public benchmark coverage is available on both sides of the comparison.

## Related Comparisons

- [GPT-5.6 Luna vs GPT-5.6 Sol](/compare/gpt-5-6-luna-vs-gpt-5-6-sol)
- [Grok 4.1 Fast vs GPT-5.6 Sol](/compare/gpt-5-6-sol-vs-grok-4-1-fast)
- [GPT-5.6 Luna vs GPT-5.6 Terra](/compare/gpt-5-6-luna-vs-gpt-5-6-terra)
- [Grok 4.1 Fast vs GPT-5.6 Terra](/compare/gpt-5-6-terra-vs-grok-4-1-fast)

## Explore More

- [GPT-5.6 Luna profile](/models/gpt-5-6-luna)
- [Grok 4.1 Fast profile](/models/grok-4-1-fast)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)