# Grok 4.20 vs Mistral Medium 3.5 128B

> Side-by-side benchmark comparison for Grok 4.20 and Mistral Medium 3.5 128B across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/grok-4-20-beta-vs-mistral-medium-3-5-128b
- Last updated: September 10, 2026

- Shared sourced benchmarks: 6
- HTML indexing: indexable
- Ranking lane: BenchAlign v5

## Quick Verdict

Pick Grok 4.20 if you want the stronger benchmark profile. Mistral Medium 3.5 128B only makes more sense when its price, context window, or workload-specific category wins matter more than the overall score.

## Summary

- Grok 4.20 leads overall 67.13 to 30.13.
- The clearest category separation is in reasoning, where the averages are 34.2 for Grok 4.20 and 68.6 for Mistral Medium 3.5 128B.
- The biggest single benchmark swing is GPQA Diamond (Vals) in Knowledge, with scores of 88.6% and 34.8%.
- Grok 4.20 is the cheaper option on output tokens, which matters if you expect large responses or heavy interactive use.
- Grok 4.20 also has the larger context window at 2M.

## Model Snapshot

| Property | Grok 4.20 | Mistral Medium 3.5 128B |
|----------|----------|----------|
| Creator | xAI | Mistral |
| Type | Proprietary | Open Weight |
| Reasoning | Reasoning | Reasoning |
| Context | 2M | 256K |
| Overall Score | 67.13 | 30.13 |
| Benchmarks Covered | 23 | 7 |
| Pricing (input/output) | $2.00 / $6.00 | $1.50 / $7.50 |

## Category Breakdown

### Agentic

- Winner: Grok 4.20
- Grok 4.20 public-lane score: 26.7 (Supported · #145/152)
- Mistral Medium 3.5 128B public-lane score: 21.9 (Supported · #150/152)

| Benchmark | Grok 4.20 | Mistral Medium 3.5 128B | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 2.0 | 47.1% | Coming soon | Coming soon |
| DeepSearchQA | 62.8% | Coming soon | Coming soon |
| Gert Labs | 38.36% | 39.10% | Mistral Medium 3.5 128B |
| Terminal-Bench 2.1 (Vals) | 44.2% | 39.0% | Grok 4.20 |
| τ³-bench results | Coming soon | 91.4% | Coming soon |

### Coding

- Winner: Coming soon
- Grok 4.20 public-lane score: 28.2 (Supported · #141/151)
- Mistral Medium 3.5 128B public-lane score: 36.9 (Estimated · #127/151)

| Benchmark | Grok 4.20 | Mistral Medium 3.5 128B | Winner |
|-----------|-----------|-----------|--------|
| LiveCodeBench Pro | 74.2% | Coming soon | Coming soon |
| SWE-bench Verified | 76.7% | 77.6% | Mistral Medium 3.5 128B |
| SWE-bench Pro | 51.8% | Coming soon | Coming soon |
| Vibe Code Bench | 4.06% | Coming soon | Coming soon |
| LiveCodeBench (Vals) | 84.3% | Coming soon | Coming soon |
| SWE-bench (Vals) | 72.2% | 66.4% | Grok 4.20 |

### Multimodal & Grounded

- Winner: Coming soon
- Grok 4.20 public-lane score: 34.6 (#43/48)
- Mistral Medium 3.5 128B public-lane score: 55.6 (Unranked · 1 rankable row)

| Benchmark | Grok 4.20 | Mistral Medium 3.5 128B | Winner |
|-----------|-----------|-----------|--------|
| MMMU-Pro | 75.2% | Coming soon | Coming soon |
| CharXiv | 60.9% | Coming soon | Coming soon |
| ERQA | 54.1% | Coming soon | Coming soon |
| SimpleVQA | 57.4% | Coming soon | Coming soon |
| MedXpertQA (MM) | 65.8% | Coming soon | Coming soon |

### Reasoning

- Winner: Coming soon
- Grok 4.20 public-lane score: 34.2 (Unranked · 2 rankable rows)
- Mistral Medium 3.5 128B public-lane score: 68.6 (Unranked · 2 rankable rows)

| Benchmark | Grok 4.20 | Mistral Medium 3.5 128B | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-2 | 53.3% | Coming soon | Coming soon |
| ARC-AGI-3 | 0.1% | Coming soon | Coming soon |

### Knowledge

- Winner: Grok 4.20
- Grok 4.20 public-lane score: 49.4 (Supported · #85/183)
- Mistral Medium 3.5 128B public-lane score: 39 (Supported · #140/183)

| Benchmark | Grok 4.20 | Mistral Medium 3.5 128B | Winner |
|-----------|-----------|-----------|--------|
| GPQA-D | 88.5% | Coming soon | Coming soon |
| HLE w/o tools | 31.6% | Coming soon | Coming soon |
| HealthBench Hard | 20.3% | Coming soon | Coming soon |
| MedXpertQA (Text) | 50.2% | Coming soon | Coming soon |
| GPQA Diamond (Vals) | 88.6% | 34.8% | Grok 4.20 |
| MMLU-Pro (Vals) | 86.3% | 75.3% | Grok 4.20 |

### Instruction Following

- Winner: Coming soon
- Grok 4.20 public-lane score: Coming soon
- Mistral Medium 3.5 128B public-lane score: 84 (#48/123)

## FAQ

### Which is better overall, Grok 4.20 or Mistral Medium 3.5 128B?

Grok 4.20 is ahead overall on BenchLM right now.

### Where is the biggest gap between Grok 4.20 and Mistral Medium 3.5 128B?

The widest category gap is in reasoning, where the averages are 34.2 for Grok 4.20 and 68.6 for Mistral Medium 3.5 128B.

### How many benchmarks does Grok 4.20 cover on BenchLM?

Grok 4.20 currently has 23 sourced benchmark scores on BenchLM.

### How many benchmarks does Mistral Medium 3.5 128B cover on BenchLM?

Mistral Medium 3.5 128B currently has 7 sourced benchmark scores on BenchLM.

## Related Comparisons

- [Grok 4.20 vs Grok 4.20 Multi-agent](/compare/grok-4-20-beta-vs-grok-4-20-multi-agent-beta)
- [Mistral Medium 3.5 128B vs Grok 4.20 Multi-agent](/compare/grok-4-20-multi-agent-beta-vs-mistral-medium-3-5-128b)
- [Grok 4.20 vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-grok-4-20-beta)
- [Mistral Medium 3.5 128B vs Claude Fable 5.1](/compare/claude-fable-5-1-vs-mistral-medium-3-5-128b)

## Explore More

- [Grok 4.20 profile](/models/grok-4-20-beta)
- [Mistral Medium 3.5 128B profile](/models/mistral-medium-3-5-128b)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)