GPT-5.2-Codex vs Muse Glimmer
| Spec | GPT-5.2-Codex | Muse Glimmer |
|---|---|---|
| Respan Index | 29.6 (#84) | 29.8 (#82) |
| Blended price per 1M | $4.81 | $0.35 |
| Context window | 400K | 131K |
| Input / output per 1M | $1.75 / $14 | $0.2 / $0.8 |
| Max output | 128K | - |
| Input | text, vision | text, vision |
| Released | 2025-12-18 | 2026-08-10 |
Respan Index by category
Each category is scored 0 to 100, and how far ahead the winner is. Leads under a point are close to even.
| Category | GPT-5.2-Codex | Muse Glimmer |
|---|---|---|
| Coding | 18.2 GPT-5.2-Codex | 10.7 Muse Glimmer |
| Agents | 21.5 GPT-5.2-Codex | 42.5 Muse Glimmer |
| Reasoning | 35.6 GPT-5.2-Codex | 27.1 Muse Glimmer |
| Knowledge & language | 34.4 GPT-5.2-Codex | 23.6* Muse Glimmer |
| Human preference | 49.0 GPT-5.2-Codex | 49.4 Muse Glimmer |
* Estimated: no published scores in that category. How the Respan Index works
Benchmarks both report
Muse Glimmer leads on 2 of the 3 benchmarks both report. Higher is better. Each score links to where it was published.
| Benchmark | GPT-5.2-Codex | Muse Glimmer |
|---|---|---|
| LMArena WebDev (LMArena) | 1339 | 1355 |
| OSWorld-Verified | 38.2% | 65.9% |
| SWE-Bench Pro | 56.4% | 51.2% |
FAQ
Is GPT-5.2-Codex better than Muse Glimmer?
Muse Glimmer scores 29.8 on the Respan Index (#82), ahead of GPT-5.2-Codex at 29.6 (#84). Muse Glimmer leads on 2 of the 3 benchmarks both report.
Which is cheaper, GPT-5.2-Codex or Muse Glimmer?
GPT-5.2-Codex lists at $1.75 input and $14 output per 1M tokens; Muse Glimmer at $0.2 and $0.8. Muse Glimmer is 14x cheaper per token at list price.
Which has the larger context window?
GPT-5.2-Codex accepts 400K tokens and Muse Glimmer 131K tokens.