Model comparison
GPT-5.5 Pro vs GPT-OSS 120B
Head-to-head evidence from 1 shared benchmark result across 1 category. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.5 Pro #38 (Estimated); GPT-OSS 120B #116 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.5 Pro and GPT-OSS 120B share 1 comparable benchmark result. 0 of 8 categories are comparable. 6 results are unique to GPT-5.5 Pro; 25 to GPT-OSS 120B.
Updated July 22, 2026- Shared results
- 1
- GPT-5.5 Pro only
- 6
- GPT-OSS 120B only
- 25
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.5 Pro and GPT-OSS 120B is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 1 shared benchmark result across 1 evidence category; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
GPT-5.5 Pro is priced at $30.00 input / $180.00 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for GPT-OSS 120B. GPT-5.5 Pro has the larger context window at 1M, compared with 128K for GPT-OSS 120B.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | GPT-5.5 Pro | Δ | GPT-OSS 120B |
|---|---|---|---|
| Agentic | GPT-5.5 Pro90.1 | MarginNo overlap | GPT-OSS 120BNot measured |
| Knowledge | GPT-5.5 Pro57.2 | MarginNo overlap | GPT-OSS 120BNot measured |
| Math | GPT-5.5 Pro48.1 | MarginNo overlap | GPT-OSS 120BNot measured |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.5 Pro | GPT-OSS 120B | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.5 Pro$30 input / $180 output | GPT-OSS 120B$0 input / $0 output | GPT-OSS 120B has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.5 ProNot available | GPT-OSS 120B262 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.5 ProNot available | GPT-OSS 120B0.79 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.5 Pro1M | GPT-OSS 120B128K | GPT-5.5 Pro lists the larger context window. |
Benchmark Deep Dive
Agentic9 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-OSS 120B | Result |
|---|---|---|---|
| BrowseCompSource | 90.1% | — | Not comparable |
| AA Agentic IndexSource | — | 13.2% | Not comparable |
| APEX-Agents-AASource | — | 3.1% | Not comparable |
| τ²-bench resultsSource | — | 65.8% | Not comparable |
| GDPval-AASource | — | 15.0% | Not comparable |
| GDPval-AASource | — | 799 | Not comparable |
| Gert LabsSource | — | 29.61% | Not comparable |
| AA EnterpriseOps-GymSource | — | 25.5% | Not comparable |
| AA ITBenchSource | — | 5.6% | Not comparable |
Coding4 benchmarks
Reasoning2 benchmarks
Knowledge10 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-OSS 120B | Result |
|---|---|---|---|
| HLESource | 57.2% | — | Not comparable |
| HLE w/o toolsSource | 43.1% | — | Not comparable |
| Artificial Analysis Intelligence IndexSource | — | 23.8% | Not comparable |
| AA-GPQA DiamondSource | — | 78.2% | Not comparable |
| AA-HLESource | — | 18.5% | Not comparable |
| AA-Omniscience IndexSource | — | -50.0% | Not comparable |
| AA-Omniscience AccuracySource | — | 21.5% | Not comparable |
| AA-Omniscience Hallucination RateSource | — | 91.2% | Not comparable |
| AA Openness IndexSource | — | 38.9% | Not comparable |
| AA MMLU-ProSource | — | 80.8% | Not comparable |
Math4 benchmarks
Multilingual1 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-OSS 120B | Result |
|---|---|---|---|
| AA Global-MMLU-LiteSource | — | 82.8% | Not comparable |
Multimodal1 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-OSS 120B | Result |
|---|---|---|---|
| Design Arena WebsiteSource | — | 998 | Not comparable |
Inst. Following1 benchmarks
| Benchmark | GPT-5.5 Pro | GPT-OSS 120B | Result |
|---|---|---|---|
| AA-IFBenchSource | — | 69.0% | Not comparable |
Frequently Asked Questions (3)
Can I compare GPT-5.5 Pro and GPT-OSS 120B on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for GPT-5.5 Pro and GPT-OSS 120B today?
GPT-5.5 Pro: $30.00 input / $180.00 output per 1M tokens GPT-OSS 120B: $0.00 input / $0.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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