# GPT-5.1-Codex vs Kimi K2.5 Instant

> Kimi K2.5 Instant is the stronger model overall, scoring 42.9 to 38.2 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-1-codex-vs-kimi-k2-5-instant
- Last updated: 2026-10-10
- Shared benchmarks: 1

## Summary

- They share 1 benchmark with published results for both. GPT-5.1-Codex scores higher in 0 categories and Kimi K2.5 Instant in 2 categories; one gap is clear of the uncertainty.
- The widest gap is in math, where Kimi K2.5 Instant leads 36.6 to 29.3.
- Kimi K2.5 Instant has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| Provider | OpenAI | Moonshot AI |
| Noometry Index | 38.2 | 42.9 |
| Rank | 178 | 92 |
| Context | 400K | — |
| Input $/M | $1.25 | — |
| Output $/M | $10 | — |
| Weights | Proprietary | Open |

## Coding

- GPT-5.1-Codex: 41.7 (#107)
- Kimi K2.5 Instant: 42.3 (#95)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena WebDev | 1337 | 1404 |
| SWE-bench Verified (bash only) | 66% | — |
| LMArena Coding | — | 1483 |
| ALE-Bench | 1,245 | — |

## Agentic & Tool Use

- GPT-5.1-Codex: 37.8 (#32)
- Kimi K2.5 Instant: —

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |

## Reasoning

- GPT-5.1-Codex: —
- Kimi K2.5 Instant: 28.5 (#88)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Hard Prompts | — | 1443 |

## Math

- GPT-5.1-Codex: 29.3 (#218)
- Kimi K2.5 Instant: 36.6 (#105)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| ProofBench | 9% | — |
| LMArena Math | — | 1443 |

## Knowledge

- GPT-5.1-Codex: —
- Kimi K2.5 Instant: 39.5 (#121)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Expert | — | 1438 |

## Multimodal

- GPT-5.1-Codex: —
- Kimi K2.5 Instant: 39.5 (#47)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Vision | — | 1254 |

## Multilingual

- GPT-5.1-Codex: —
- Kimi K2.5 Instant: 52.2 (#89)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Non-English | — | 1406 |
| LMArena Chinese | — | 1450 |
| LMArena French | — | 1403 |
| LMArena German | — | 1413 |
| LMArena Korean | — | 1378 |
| LMArena Russian | — | 1404 |
| LMArena Spanish | — | 1448 |

## Instruction Following

- GPT-5.1-Codex: —
- Kimi K2.5 Instant: 75.5 (#61)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Instruction Following | — | 1430 |

## Long Context

- GPT-5.1-Codex: —
- Kimi K2.5 Instant: 43.8 (#82)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Longer Query | — | 1435 |

## Writing & Preference

- GPT-5.1-Codex: —
- Kimi K2.5 Instant: 60.8 (#91)

| Benchmark | GPT-5.1-Codex | Kimi K2.5 Instant |
|---|---|---|
| LMArena Text | — | 1420 |
| LMArena Creative Writing | — | 1379 |
| LMArena Multi-Turn | — | 1427 |

## FAQ

### Is GPT-5.1-Codex better than Kimi K2.5 Instant?

Kimi K2.5 Instant is the stronger model overall, scoring 42.9 to 38.2 on the Noometry Index.

### Is GPT-5.1-Codex or Kimi K2.5 Instant better for coding?

They score almost the same on coding (41.7 vs 42.3); test both on your own repository before choosing.

### How many benchmarks do GPT-5.1-Codex and Kimi K2.5 Instant share?

1 benchmark has published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Kimi K2.5 Instant has 18.