Model comparison
GPT-5.1-Codex-Max vs GPT-OSS 20B
Head-to-head evidence from 11 shared benchmark results across 5 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: GPT-5.1-Codex-Max #90 (Estimated); GPT-OSS 20B #159 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. GPT-5.1-Codex-Max and GPT-OSS 20B share 11 comparable benchmark results. 0 of 8 categories are comparable. 2 results are unique to GPT-5.1-Codex-Max; 7 to GPT-OSS 20B.
Updated July 20, 2026- Shared results
- 11
- GPT-5.1-Codex-Max only
- 2
- GPT-OSS 20B only
- 7
- Comparable categories
- 0 / 8
Benchmark data for GPT-5.1-Codex-Max and GPT-OSS 20B is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 11 shared benchmark results across 5 evidence categories; 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-5.1-Codex-Max is priced at $1.25 input / $10.00 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for GPT-OSS 20B. GPT-5.1-Codex-Max has the larger context window at 400K, compared with 128K for GPT-OSS 20B.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | GPT-5.1-Codex-Max | GPT-OSS 20B | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | GPT-5.1-Codex-Max$1.25 input / $10 output | GPT-OSS 20B$0 input / $0 output | GPT-OSS 20B has the lower combined listed price. |
| Generation speedtokens per second | GPT-5.1-Codex-MaxNot available | GPT-OSS 20B313 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | GPT-5.1-Codex-MaxNot available | GPT-OSS 20B0.65 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | GPT-5.1-Codex-Max400K | GPT-OSS 20B128K | GPT-5.1-Codex-Max lists the larger context window. |
Benchmark Deep Dive
Agentic5 benchmarks
Coding4 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | GPT-5.1-Codex-Max | GPT-OSS 20B | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 34.7% | 14.9% | GPT-5.1-Codex-Max leads |
| AA-GPQA DiamondSource | 86.0% | 68.8% | GPT-5.1-Codex-Max leads |
| AA-HLESource | 23.4% | 9.8% | GPT-5.1-Codex-Max leads |
| AA-Omniscience IndexSource | -6.0% | -63.9% | GPT-5.1-Codex-Max leads |
| AA-Omniscience AccuracySource | 39.2% | 15.5% | GPT-5.1-Codex-Max leads |
| AA-Omniscience Hallucination RateSource | 74.4% | 94.1% | GPT-5.1-Codex-Max leads |
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | GPT-5.1-Codex-Max | GPT-OSS 20B | Result |
|---|---|---|---|
| AA-IFBenchSource | 70.0% | 65.1% | GPT-5.1-Codex-Max leads |
Frequently Asked Questions (3)
Can I compare GPT-5.1-Codex-Max and GPT-OSS 20B 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-5.1-Codex-Max and GPT-OSS 20B today?
GPT-5.1-Codex-Max: $1.25 input / $10.00 output per 1M tokens GPT-OSS 20B: $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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