# GPT-5.5 Pro vs GPT-OSS 120B

> Side-by-side benchmark comparison for GPT-5.5 Pro and GPT-OSS 120B across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-5-5-pro-vs-gpt-oss-120b
- Last updated: September 4, 2026

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

## Quick Verdict

No benchmark verdict yet: there is no shared sourced benchmark row for GPT-5.5 Pro and GPT-OSS 120B.

## Summary

- GPT-5.5 Pro and GPT-OSS 120B 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-5.5 Pro | GPT-OSS 120B |
|----------|----------|----------|
| Creator | OpenAI | OpenAI |
| Type | Proprietary | Open Weight |
| Reasoning | Reasoning | Non-Reasoning |
| Context | 1M | 128K |
| Independent public score (not head-to-head) | 63.07 | 49.26 |
| Benchmarks Covered | 6 | 2 |
| Pricing (input/output) | $30.00 / $180.00 | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-5.5 Pro public-lane score: 60.6 (Estimated · #24/151)
- GPT-OSS 120B public-lane score: 44.9 (Estimated · #97/151)

| Benchmark | GPT-5.5 Pro | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| BrowseComp | 90.1% | Coming soon | Coming soon |
| Gert Labs | Coming soon | 29.61% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- GPT-5.5 Pro public-lane score: Coming soon
- GPT-OSS 120B public-lane score: 46.2 (Estimated · #100/183)

| Benchmark | GPT-5.5 Pro | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| React Native Evals | Coming soon | 71.6% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- GPT-5.5 Pro public-lane score: Coming soon
- GPT-OSS 120B public-lane score: 57.7 (Unranked · 2 rankable rows)

### Knowledge

- Winner: Insufficient shared evidence
- GPT-5.5 Pro public-lane score: 61.1 (Estimated · #36/181)
- GPT-OSS 120B public-lane score: 44.4 (Estimated · #118/181)

| Benchmark | GPT-5.5 Pro | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| HLE | 57.2% | Coming soon | Coming soon |
| HLE w/o tools | 43.1% | Coming soon | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-5.5 Pro public-lane score: Coming soon
- GPT-OSS 120B public-lane score: 84 (#46/120)

### Mathematics

- Winner: Insufficient shared evidence
- GPT-5.5 Pro public-lane score: 70.2 (Unranked · 3 rankable rows)
- GPT-OSS 120B public-lane score: Coming soon

| Benchmark | GPT-5.5 Pro | GPT-OSS 120B | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath (legacy) | 52.4% | Coming soon | Coming soon |
| FrontierMath v2 (Tiers 1-3) | 51.000% | Coming soon | Coming soon |
| FrontierMath v2 (Tier 4) | 39.600% | Coming soon | Coming soon |

## FAQ

### Can I compare GPT-5.5 Pro and GPT-OSS 120B 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-5.5 Pro vs GPT-5.5](/compare/gpt-5-5-vs-gpt-5-5-pro)
- [GPT-OSS 120B vs GPT-5.5](/compare/gpt-5-5-vs-gpt-oss-120b)
- [GPT-5.5 Pro vs GPT-OSS 20B](/compare/gpt-5-5-pro-vs-gpt-oss-20b)
- [GPT-OSS 120B vs GPT-OSS 20B](/compare/gpt-oss-120b-vs-gpt-oss-20b)

## Explore More

- [GPT-5.5 Pro profile](/models/gpt-5-5-pro)
- [GPT-OSS 120B profile](/models/gpt-oss-120b)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)