# GPT-6 Luna vs Grok 4.20

> Side-by-side benchmark comparison for GPT-6 Luna and Grok 4.20 across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-6-luna-vs-grok-4-20-beta
- 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: GPT-6 Luna and Grok 4.20 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.
- Grok 4.20 has the larger published context window at 2M.

## Model Snapshot

| Property | GPT-6 Luna | Grok 4.20 |
|----------|----------|----------|
| Creator | OpenAI | xAI |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 1.05M | 2M |
| Independent public score (not head-to-head) | 62.33 | 67.97 |
| Benchmarks Covered | 7 | 23 |
| Pricing (input/output) | $0.10 / $0.50 | $2.00 / $6.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-6 Luna public-lane score: 56.7 (Estimated · #35/157)
- Grok 4.20 public-lane score: 29.5 (Supported · #147/157)

| Benchmark | GPT-6 Luna | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| ExploitGym | 11.6% | Coming soon | Coming soon |
| Terminal-Bench 2.0 | Coming soon | 47.1% | Coming soon |
| DeepSearchQA | Coming soon | 62.8% | Coming soon |
| Gert Labs | Coming soon | 38.36% | Coming soon |
| Terminal-Bench 2.1 (Vals) | Coming soon | 44.2% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-6 Luna public-lane score: 66.6 (Estimated · #11/159)
- Grok 4.20 public-lane score: 29.8 (Supported · #149/159)

| Benchmark | GPT-6 Luna | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| DeepSWE | 66.6% | Coming soon | Coming soon |
| LiveCodeBench Pro | Coming soon | 74.2% | Coming soon |
| SWE-bench Verified | Coming soon | 76.7% | Coming soon |
| SWE-bench Pro | Coming soon | 51.8% | Coming soon |
| Vibe Code Bench | Coming soon | 4.06% | Coming soon |
| LiveCodeBench (Vals) | Coming soon | 84.3% | Coming soon |
| SWE-bench (Vals) | Coming soon | 72.2% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- GPT-6 Luna public-lane score: 78.3 (Unranked · 2 rankable rows)
- Grok 4.20 public-lane score: 34.3 (Unranked · 2 rankable rows)

| Benchmark | GPT-6 Luna | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-2 | Coming soon | 53.3% | Coming soon |
| ARC-AGI-3 | Coming soon | 0.1% | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-6 Luna public-lane score: 71.3 (Unranked · 1 rankable row)
- Grok 4.20 public-lane score: 34.6 (#45/50)

| Benchmark | GPT-6 Luna | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| MMMU-Pro | Coming soon | 75.2% | Coming soon |
| CharXiv | Coming soon | 60.9% | Coming soon |
| ERQA | Coming soon | 54.1% | Coming soon |
| SimpleVQA | Coming soon | 57.4% | Coming soon |
| MedXpertQA (MM) | Coming soon | 65.8% | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- GPT-6 Luna public-lane score: 63.6 (Estimated · #29/189)
- Grok 4.20 public-lane score: 50.5 (Supported · #87/189)

| Benchmark | GPT-6 Luna | Grok 4.20 | Winner |
|-----------|-----------|-----------|--------|
| HealthBench (raw) | 50.0% | Coming soon | Coming soon |
| HealthBench (length-adjusted) | 54.5% | Coming soon | Coming soon |
| HealthBench Professional | 60.8% | Coming soon | Coming soon |
| HealthBench Professional (raw) | 61.2% | Coming soon | Coming soon |
| HealthBench Hard | 31.4% | 20.3% | GPT-6 Luna |
| GPQA-D | Coming soon | 88.5% | Coming soon |
| HLE w/o tools | Coming soon | 31.6% | Coming soon |
| MedXpertQA (Text) | Coming soon | 50.2% | Coming soon |
| GPQA Diamond (Vals) | Coming soon | 88.6% | Coming soon |
| MMLU-Pro (Vals) | Coming soon | 86.3% | Coming soon |

## FAQ

### Is there enough evidence to pick between GPT-6 Luna and Grok 4.20?

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

- [GPT-6 Luna vs GPT-6 Astra](/compare/gpt-6-astra-vs-gpt-6-luna)
- [Grok 4.20 vs GPT-6 Astra](/compare/gpt-6-astra-vs-grok-4-20-beta)
- [GPT-6 Luna vs GPT-6 Sol](/compare/gpt-6-luna-vs-gpt-6-sol)
- [Grok 4.20 vs GPT-6 Sol](/compare/gpt-6-sol-vs-grok-4-20-beta)

## Explore More

- [GPT-6 Luna profile](/models/gpt-6-luna)
- [Grok 4.20 profile](/models/grok-4-20-beta)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)