GPT-5.1 Codex MaxvsMuse Spark 1.3
Muse Spark 1.3 is the newer model, released after GPT-5.1 Codex Max.
| Spec | GPT-5.1 Codex Max | Muse Spark 1.3 |
|---|---|---|
| Input price | — | $1.25/M tokens |
| Output price | — | $4.25/M tokens |
| Context window | — | 1.0M tokens |
| Weights | Closed | Closed |
| Free API (OpenRouter) | No | No |
| Released | Dec 2025 | Sep 2026 |
Our Verdict
GPT-5.1 Codex Max
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 Max
Input
—
Output
—
Muse Spark 1.3
Input
$1.25
Output
$4.25
Where to run it
2 hosts
GPT-5.1 Codex Max1 host
Muse Spark 1.31 host
Per million tokens. Prices and uptime via OpenRouter, checked 13 Sep 2026.
Writing DNA
Style Comparison
Similarity
71%
Muse Spark 1.3 uses 3.9x more headings
GPT-5.1 Codex Max
Muse Spark 1.3
60%Vocabulary59%
16wSentence Length14w
0.36Hedging0.28
2.3Bold2.6
4.2Lists2.3
0.00Emoji0.00
0.12Headings0.48
0.03Transitions0.02
Based on 13 + 27 text responses
Research
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FAQ
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