# GPT-5.3 Codex vs Muse Glimmer

> GPT-5.3 Codex is the stronger model overall, scoring 45.5 to 41.3 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-3-codex-vs-muse-glimmer
- Last updated: 2026-10-10
- Shared benchmarks: 1

## Summary

- They share 1 benchmark with published results for both. GPT-5.3 Codex scores higher in 1 category and Muse Glimmer in 0 categories; one gap is clear of the uncertainty.
- The widest gap is in coding, where GPT-5.3 Codex leads 48.5 to 38.7.
- Muse Glimmer has downloadable open weights; the other is API-only.

## Snapshot

| | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| Provider | OpenAI | Meta |
| Noometry Index | 45.5 | 41.3 |
| Rank | 61 | 128 |
| Context | 400K | — |
| Input $/M | $1.75 | — |
| Output $/M | $14 | — |
| Weights | Proprietary | Open |

## Coding

- GPT-5.3 Codex: 48.5 (#51)
- Muse Glimmer: 38.7 (#157)

| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena WebDev | 1408 | 1355 |
| SWE-bench Verified | 74.8% | — |
| WeirdML | 79.3% | — |
| LMArena Coding | — | 1417 |
| ALE-Bench | 1,655 | — |

## Agentic & Tool Use

- GPT-5.3 Codex: 47.8 (#9)
- Muse Glimmer: —

| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| Terminal-Bench | 78.4% | — |
| METR Time Horizons | 74.5% | — |
| Vending-Bench 2 | 5,940 | — |

## Reasoning

- GPT-5.3 Codex: —
- Muse Glimmer: 27.2 (#111)

| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Hard Prompts | — | 1395 |
| Epoch Capabilities Index | 156.84 | — |

## Math

- GPT-5.3 Codex: —
- Muse Glimmer: 36.1 (#128)

| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Math | — | 1419 |

## Knowledge

- GPT-5.3 Codex: —
- Muse Glimmer: 37.9 (#140)

| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Expert | — | 1388 |

## Multilingual

- GPT-5.3 Codex: —
- Muse Glimmer: 50.6 (#117)

| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Non-English | — | 1384 |
| LMArena Chinese | — | 1412 |
| LMArena Russian | — | 1393 |

## Instruction Following

- GPT-5.3 Codex: —
- Muse Glimmer: 72.7 (#134)

| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Instruction Following | — | 1374 |

## Long Context

- GPT-5.3 Codex: —
- Muse Glimmer: 42.1 (#124)

| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Longer Query | — | 1381 |

## Writing & Preference

- GPT-5.3 Codex: —
- Muse Glimmer: 57.7 (#122)

| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Text | — | 1389 |
| LMArena Creative Writing | — | 1338 |
| LMArena Multi-Turn | — | 1398 |

## FAQ

### Is GPT-5.3 Codex better than Muse Glimmer?

GPT-5.3 Codex is the stronger model overall, scoring 45.5 to 41.3 on the Noometry Index.

### Is GPT-5.3 Codex or Muse Glimmer better for coding?

GPT-5.3 Codex scores higher on coding benchmarks: 48.5 versus 38.7 in the Noometry coding category.

### How many benchmarks do GPT-5.3 Codex and Muse Glimmer share?

1 benchmark has published results for both models. GPT-5.3 Codex has 8 scored results on Noometry and Muse Glimmer has 13.