Model comparison
GPT-5.3 Codex vs Muse Glimmer
GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 41.7 on the Noometry Index.
Last verified . 1 shared benchmarks.
MetaSummary
- 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 48.6 to 40.4.
- Muse Glimmer has downloadable open weights; the other is API-only.
Side by side
| GPT-5.3 Codex | Muse Glimmer | |
|---|---|---|
| Provider | OpenAI | Meta |
| Noometry Index | 45.8 | 41.7 |
| Released | 2026-02-05 | 2026-08-10 |
| Weights | Proprietary | Open |
| Context window | 400K | — |
| Max output | 128K | — |
| Input $ / M tokens | $1.75 | — |
| Output $ / M tokens | $14 | — |
| Results tracked | 8 | 15 |
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Category by category
Coding GPT-5.3 Codex leads
GPT-5.3 Codex: 48.6 (#56), Muse Glimmer: 40.4 (#142)
| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena WebDev | 1409 | 1355 |
| SWE-bench Verified | 74.8% | — |
| SciCode | — | 44.9% |
| WeirdML | 79.3% | — |
| LMArena Coding | — | 1416 |
| ALE-Bench | 1,655 | — |
Agentic & Tool Use Not comparable
GPT-5.3 Codex: 48.0 (#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 Not comparable
GPT-5.3 Codex: —, Muse Glimmer: 25.7 (#144)
| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| CritPt | — | 2.6% |
| LMArena Hard Prompts | — | 1396 |
| Epoch Capabilities Index | 156.77 | — |
Math Not comparable
GPT-5.3 Codex: —, Muse Glimmer: 38.8 (#125)
| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Math | — | 1417 |
Knowledge Not comparable
GPT-5.3 Codex: —, Muse Glimmer: 38.5 (#143)
| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Expert | — | 1386 |
Multilingual Not comparable
GPT-5.3 Codex: —, Muse Glimmer: 50.5 (#122)
| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Non-English | — | 1384 |
| LMArena Chinese | — | 1412 |
| LMArena Russian | — | 1390 |
Instruction Following Not comparable
GPT-5.3 Codex: —, Muse Glimmer: 72.6 (#135)
| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Instruction Following | — | 1375 |
Long Context Not comparable
GPT-5.3 Codex: —, Muse Glimmer: 42.1 (#129)
| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Longer Query | — | 1382 |
Writing & Preference Not comparable
GPT-5.3 Codex: —, Muse Glimmer: 57.5 (#126)
| Benchmark | GPT-5.3 Codex | Muse Glimmer |
|---|---|---|
| LMArena Text | — | 1389 |
| LMArena Creative Writing | — | 1339 |
| LMArena Multi-Turn | — | 1399 |
Frequently asked questions
Is GPT-5.3 Codex better than Muse Glimmer?
GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 41.7 on the Noometry Index.
Is GPT-5.3 Codex or Muse Glimmer better for coding?
GPT-5.3 Codex scores higher on coding benchmarks: 48.6 versus 40.4 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 15.