Model comparison
Claude Sonnet 5.5 vs GPT-5.1-Codex-mini
Claude Sonnet 5.5 has enough public results to be ranked (#10); GPT-5.1-Codex-mini does not yet, so treat this comparison as directional.
Last verified . 1 shared benchmarks.
Summary
- They share 1 benchmark with published results for both. Claude Sonnet 5.5 scores higher in 2 categories and GPT-5.1-Codex-mini in 0 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in coding, where Claude Sonnet 5.5 leads 67.3 to 31.6.
- GPT-5.1-Codex-mini is cheaper at $0.25 / $2 per million input/output tokens, against $2 / $10 for Claude Sonnet 5.5.
- Claude Sonnet 5.5 accepts more context: 1M tokens versus 400K.
Side by side
| Claude Sonnet 5.5 | GPT-5.1-Codex-mini | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 61.9 | 37.3 |
| Released | 2026-09-28 | 2025-11-12 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 400K |
| Max output | 128K | 128K |
| Input $ / M tokens | $2 | $0.25 |
| Output $ / M tokens | $10 | $2 |
| Results tracked | 32 | 2 |
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Category by category
Coding Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 67.3 (#6), GPT-5.1-Codex-mini: 31.6
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| LMArena WebDev | 1774 | 1244 |
| FrontierCode | 52.1% | — |
| CursorBench | 55.5% | — |
| FrontierSWE | 61.9% | — |
| SciCode | 61% | — |
| LMArena Coding | 1513 | — |
| ALE-Bench | 1,819 | — |
Agentic & Tool Use Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 45.0 (#16), GPT-5.1-Codex-mini: 38.5
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| Terminal-Bench | — | 61.6% |
| APEX-Agents | 75.5% | — |
Reasoning Not comparable
Claude Sonnet 5.5: 54.0 (#28), GPT-5.1-Codex-mini: —
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| NYT Connections (extended) | 80.5% | — |
| CritPt | 31.4% | — |
| LMArena Hard Prompts | 1495 | — |
| Mystery Game Puzzles | 65% | — |
| Epoch Capabilities Index | 165.03 | — |
Math Not comparable
Claude Sonnet 5.5: 87.9 (#6), GPT-5.1-Codex-mini: —
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| FrontierMath (Tiers 1-3) | 88.8% | — |
| FrontierMath Tier 4 | 80.5% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 100% | — |
| LMArena Math | 1510 | — |
| FrontierMath Erdős | 2.9% | — |
Knowledge Not comparable
Claude Sonnet 5.5: 66.0 (#12), GPT-5.1-Codex-mini: —
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| GPQA Diamond | 95.6% | — |
| SimpleQA Verified | 46.5% | — |
| LMArena Expert | 1540 | — |
Multimodal Not comparable
Claude Sonnet 5.5: 51.5 (#6), GPT-5.1-Codex-mini: —
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| LMArena Vision | 1289 | — |
| Furniture Assembly | 75% | — |
Multilingual Not comparable
Claude Sonnet 5.5: 55.3 (#30), GPT-5.1-Codex-mini: —
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| LMArena Non-English | 1452 | — |
| LMArena Chinese | 1522 | — |
| LMArena Russian | 1451 | — |
Instruction Following Not comparable
Claude Sonnet 5.5: 78.3 (#11), GPT-5.1-Codex-mini: —
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| LMArena Instruction Following | 1495 | — |
Long Context Not comparable
Claude Sonnet 5.5: 45.9 (#28), GPT-5.1-Codex-mini: —
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| LMArena Longer Query | 1498 | — |
Writing & Preference Not comparable
Claude Sonnet 5.5: 66.0 (#40), GPT-5.1-Codex-mini: —
| Benchmark | Claude Sonnet 5.5 | GPT-5.1-Codex-mini |
|---|---|---|
| LMArena Text | 1471 | — |
| LMArena Creative Writing | 1465 | — |
| LMArena Multi-Turn | 1474 | — |
Frequently asked questions
Is Claude Sonnet 5.5 better than GPT-5.1-Codex-mini?
Claude Sonnet 5.5 has enough public results to be ranked (#10); GPT-5.1-Codex-mini does not yet, so treat this comparison as directional.
Which is cheaper, Claude Sonnet 5.5 or GPT-5.1-Codex-mini?
GPT-5.1-Codex-mini is cheaper. It lists at $0.25 per million input tokens and $2 per million output tokens; Claude Sonnet 5.5 lists at $2 and $10.
Is Claude Sonnet 5.5 or GPT-5.1-Codex-mini better for coding?
Claude Sonnet 5.5 scores higher on coding benchmarks: 67.3 versus 31.6 in the Noometry coding category.
Which has the bigger context window?
Claude Sonnet 5.5 does, with 1M tokens against 400K.
How many benchmarks do Claude Sonnet 5.5 and GPT-5.1-Codex-mini share?
1 benchmark has published results for both models. Claude Sonnet 5.5 has 32 scored results on Noometry and GPT-5.1-Codex-mini has 2.