# GPT-OSS 120B vs Mistral Medium 3.5 128B

> Side-by-side benchmark comparison for GPT-OSS 120B and Mistral Medium 3.5 128B across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-oss-120b-vs-mistral-medium-3-5-128b
- Last updated: September 29, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.7

## Quick Verdict

Evidence is too thin for a benchmark verdict: GPT-OSS 120B and Mistral Medium 3.5 128B 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-OSS 120B has the lower published output-token price.
- Mistral Medium 3.5 128B has the larger published context window at 256K.

## Model Snapshot

| Property | GPT-OSS 120B | Mistral Medium 3.5 128B |
|----------|----------|----------|
| Creator | OpenAI | Mistral |
| Type | Open Weight | Open Weight |
| Reasoning | Non-Reasoning | Reasoning |
| Context | 128K | 256K |
| Independent public score (not head-to-head) | 37.66 | 36.09 |
| Benchmarks Covered | 2 | 7 |
| Pricing (input/output) | $0.00 / $0.00 | $1.50 / $7.50 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-OSS 120B public-lane score: 20.5 (Estimated · #97/117)
- Mistral Medium 3.5 128B public-lane score: 19.7 (Supported · #100/117)

| Benchmark | GPT-OSS 120B | Mistral Medium 3.5 128B | Winner |
|-----------|-----------|-----------|--------|
| Gert Labs | 29.61% | 39.10% | Mistral Medium 3.5 128B |
| τ³-bench results | Coming soon | 91.4% | Coming soon |
| Terminal-Bench 2.1 (Vals) | Coming soon | 39.0% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-OSS 120B public-lane score: 26.4 (Estimated · #104/143)
- Mistral Medium 3.5 128B public-lane score: 26.6 (Estimated · #102/143)

| Benchmark | GPT-OSS 120B | Mistral Medium 3.5 128B | Winner |
|-----------|-----------|-----------|--------|
| React Native Evals | 71.6% | Coming soon | Coming soon |
| SWE-bench Verified | Coming soon | 77.6% | Coming soon |
| SWE-bench (Vals) | Coming soon | 66.4% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- GPT-OSS 120B public-lane score: 58 (Unranked · 2 rankable rows)
- Mistral Medium 3.5 128B public-lane score: 69.9 (Unranked · 2 rankable rows)

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- GPT-OSS 120B public-lane score: Coming soon
- Mistral Medium 3.5 128B public-lane score: 56.7 (Unranked · 1 rankable row)

### Knowledge

- Winner: Insufficient shared evidence
- GPT-OSS 120B public-lane score: 37.1 (Estimated · #107/169)
- Mistral Medium 3.5 128B public-lane score: 33.6 (Supported · #121/169)

| Benchmark | GPT-OSS 120B | Mistral Medium 3.5 128B | Winner |
|-----------|-----------|-----------|--------|
| GPQA Diamond (Vals) | Coming soon | 34.8% | Coming soon |
| MMLU-Pro (Vals) | Coming soon | 75.3% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-OSS 120B public-lane score: 82.8 (#46/124)
- Mistral Medium 3.5 128B public-lane score: 82.6 (#48/124)

## FAQ

### Is there enough evidence to pick between GPT-OSS 120B and Mistral Medium 3.5 128B?

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-OSS 120B vs GPT-OSS 20B](/compare/gpt-oss-120b-vs-gpt-oss-20b)
- [Mistral Medium 3.5 128B vs GPT-OSS 20B](/compare/gpt-oss-20b-vs-mistral-medium-3-5-128b)
- [GPT-OSS 120B vs GPT-6 Astra](/compare/gpt-6-astra-vs-gpt-oss-120b)
- [Mistral Medium 3.5 128B vs GPT-6 Astra](/compare/gpt-6-astra-vs-mistral-medium-3-5-128b)

## Explore More

- [GPT-OSS 120B profile](/models/gpt-oss-120b)
- [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)