GPT-5.1-CodexvsMuse Spark 1.3
Muse Spark 1.3 has a larger context window than GPT-5.1-Codex (1.0M tokens vs 400K tokens).
| Spec | GPT-5.1-Codex | Muse Spark 1.3 |
|---|---|---|
| Input price | $1.25/M tokens | $1.25/M tokens |
| Output price | $10/M tokens | $4.25/M tokens |
| Context window | 400K tokens | 1.0M tokens |
| Weights | Closed | Closed |
| Free API (OpenRouter) | No | No |
| Released | Nov 2025 | Sep 2026 |
Our Verdict
GPT-5.1-Codex
Muse Spark 1.3
Not enough votes to call it. On the specs, nothing separates them.
Too close to call
Reviewing agent-written code?See a Brief PR report
API pricing
Cost per 1M tokens
GPT-5.1-Codex
Input
$1.25
Output
$10.00
Muse Spark 1.3
Input
$1.25
Output
$4.25
2.4× cheaper
Where to run it
2 hosts
GPT-5.1-Codex1 host
Muse Spark 1.31 host
Per million tokens. Prices and uptime via OpenRouter, checked 11 Sep 2026.
Writing DNA
Style Comparison
Similarity
45%
GPT-5.1-Codex uses 21.3x more transitions
GPT-5.1-Codex
Muse Spark 1.3
70%Vocabulary59%
17wSentence Length14w
0.39Hedging0.28
3.4Bold2.6
3.5Lists2.3
0.00Emoji0.00
0.50Headings0.48
0.38Transitions0.02
Based on 14 + 27 text responses
Research
What we learned reading every model
FAQ
Common questions
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