# GPT-5.1-Codex vs Yi-1.5-34B

> GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 30.2 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-1-codex-vs-yi-1-5-34b
- Last updated: 2026-10-10
- Shared benchmarks: 0

## Summary

- The widest gap is in coding, where GPT-5.1-Codex leads 41.7 to 31.9.
- Yi-1.5-34B has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| Provider | OpenAI | 01.AI |
| Noometry Index | 38.2 | 30.2 |
| Rank | 178 | 286 |
| Context | 400K | — |
| Input $/M | $1.25 | — |
| Output $/M | $10 | — |
| Weights | Proprietary | Open |

## Coding

- GPT-5.1-Codex: 41.7 (#107)
- Yi-1.5-34B: 31.9 (#267)

| Benchmark | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1337 | — |
| BigCodeBench Instruct | — | 33.9% |
| LMArena Coding | — | 1169 |
| BigCodeBench Complete | — | 43.8% |
| ALE-Bench | 1,245 | — |

## Agentic & Tool Use

- GPT-5.1-Codex: 37.8 (#32)
- Yi-1.5-34B: —

| Benchmark | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |

## Reasoning

- GPT-5.1-Codex: —
- Yi-1.5-34B: 21.5 (#195)

| Benchmark | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| LMArena Hard Prompts | — | 1160 |

## Math

- GPT-5.1-Codex: 29.3 (#218)
- Yi-1.5-34B: 25.3 (#248)

| Benchmark | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| ProofBench | 9% | — |
| LMArena Math | — | 1182 |
| MATH Level 5 | — | 25.5% |

## Knowledge

- GPT-5.1-Codex: —
- Yi-1.5-34B: 14.8 (#290)

| Benchmark | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| GPQA Diamond | — | 32% |
| LMArena Expert | — | 1144 |

## Multilingual

- GPT-5.1-Codex: —
- Yi-1.5-34B: 32.5 (#251)

| Benchmark | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| LMArena Non-English | — | 1121 |
| LMArena Chinese | — | 1213 |
| LMArena French | — | 1155 |
| LMArena German | — | 1111 |
| LMArena Japanese | — | 1021 |
| LMArena Korean | — | 1005 |
| LMArena Russian | — | 1091 |
| LMArena Spanish | — | 1120 |

## Instruction Following

- GPT-5.1-Codex: —
- Yi-1.5-34B: 59.4 (#252)

| Benchmark | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| LMArena Instruction Following | — | 1139 |

## Long Context

- GPT-5.1-Codex: —
- Yi-1.5-34B: 34.6 (#243)

| Benchmark | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| LMArena Longer Query | — | 1144 |

## Writing & Preference

- GPT-5.1-Codex: —
- Yi-1.5-34B: 37.6 (#252)

| Benchmark | GPT-5.1-Codex | Yi-1.5-34B |
|---|---|---|
| LMArena Text | — | 1173 |
| LMArena Creative Writing | — | 1135 |
| LMArena Multi-Turn | — | 1153 |

## FAQ

### Is GPT-5.1-Codex better than Yi-1.5-34B?

GPT-5.1-Codex is the stronger model overall, scoring 38.2 to 30.2 on the Noometry Index.

### Is GPT-5.1-Codex or Yi-1.5-34B better for coding?

GPT-5.1-Codex scores higher on coding benchmarks: 41.7 versus 31.9 in the Noometry coding category.

### How many benchmarks do GPT-5.1-Codex and Yi-1.5-34B share?

0 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Yi-1.5-34B has 21.