# Devstral Small 2505 vs GPT-5.1-Codex

> GPT-5.1-Codex is the stronger model overall, scoring 38.6 to 34.3 on the Noometry Index. Devstral Small 2505 costs 23× less per token, which makes it the better buy when GPT-5.1-Codex's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/devstral-small-vs-gpt-5-1-codex
- Last updated: 2026-10-11
- Shared benchmarks: 1

## Summary

- They share 1 benchmark with published results for both. Devstral Small 2505 scores higher in 0 categories and GPT-5.1-Codex in 1 category; one gap is clear of the uncertainty.
- The biggest single-benchmark swing is SWE-bench Verified (bash only): 56.4% for Devstral Small 2505 and 66% for GPT-5.1-Codex.
- Devstral Small 2505 is cheaper at $0.10 / $0.30 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- GPT-5.1-Codex accepts more context: 400K tokens versus 128K.
- Devstral Small 2505 has downloadable open weights; the other is API-only.

## Snapshot

| | Devstral Small 2505 | GPT-5.1-Codex |
|---|---|---|
| Provider | Mistral AI | OpenAI |
| Noometry Index | 34.3 | 38.6 |
| Rank | 233 | 186 |
| Context | 128K | 400K |
| Input $/M | $0.10 | $1.25 |
| Output $/M | $0.30 | $10 |
| Weights | Open | Proprietary |

## Coding

- Devstral Small 2505: 38.9 (#166)
- GPT-5.1-Codex: 41.9 (#116)

| Benchmark | Devstral Small 2505 | GPT-5.1-Codex |
|---|---|---|
| SWE-bench Verified (bash only) | 56.4% | 66% |
| LMArena WebDev | — | 1337 |
| SciCode | 28.8% | — |
| ALE-Bench | — | 1,245 |

## Agentic & Tool Use

- Devstral Small 2505: —
- GPT-5.1-Codex: 38.0 (#33)

| Benchmark | Devstral Small 2505 | GPT-5.1-Codex |
|---|---|---|
| Terminal-Bench | — | 60.4% |
| METR Time Horizons | — | 70.8% |

## Reasoning

- Devstral Small 2505: 19.7 (#252)
- GPT-5.1-Codex: —

| Benchmark | Devstral Small 2505 | GPT-5.1-Codex |
|---|---|---|
| Kagi LLM Benchmark | 37.7% | — |
| CritPt | 0% | — |

## Math

- Devstral Small 2505: —
- GPT-5.1-Codex: 30.3 (#235)

| Benchmark | Devstral Small 2505 | GPT-5.1-Codex |
|---|---|---|
| ProofBench | — | 9% |

## FAQ

### Is Devstral Small 2505 better than GPT-5.1-Codex?

GPT-5.1-Codex is the stronger model overall, scoring 38.6 to 34.3 on the Noometry Index. Devstral Small 2505 costs 23× less per token, which makes it the better buy when GPT-5.1-Codex's lead doesn't matter for your workload.

### Which is cheaper, Devstral Small 2505 or GPT-5.1-Codex?

Devstral Small 2505 is cheaper. It lists at $0.10 per million input tokens and $0.30 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.

### Is Devstral Small 2505 or GPT-5.1-Codex better for coding?

GPT-5.1-Codex scores higher on coding benchmarks: 41.9 versus 38.9 in the Noometry coding category.

### Which has the bigger context window?

GPT-5.1-Codex does, with 400K tokens against 128K.

### How many benchmarks do Devstral Small 2505 and GPT-5.1-Codex share?

1 benchmark has published results for both models. Devstral Small 2505 has 4 scored results on Noometry and GPT-5.1-Codex has 6.