GPT-5.1 Codex Max
Model details
- Model
gpt-5.1-codex-max- Provider
openai- API
openai-responses- Base URL
https://api.openai.com/v1- Input
- text, image
- Reasoning
- Yes
- Context window
- 400,000
- Max tokens
- 128,000
Show configuration
{
"providers": {
"openai": {
"apiKey": "YOUR_API_KEY",
"models": [
{
"id": "gpt-5.1-codex-max",
"name": "GPT-5.1 Codex Max",
"reasoning": true,
"input": [
"text",
"image"
],
"thinkingLevelMap": {
"off": null
},
"contextWindow": 400000,
"maxTokens": 128000,
"cost": {
"input": 1.25,
"output": 10,
"cacheRead": 0.125,
"cacheWrite": 0
}
}
],
"api": "openai-responses",
"baseUrl": "https://api.openai.com/v1"
}
}
}Pricing
USD per million tokens. A tier is selected from the total input tokens in each request and applies to that entire request.
| Request input | Input | Output | Cache read | Cache write |
|---|---|---|---|---|
| All requests | $1.25 | $10 | $0.125 | $0 |
Session cost calculator
Estimate the requests made during an agent session. A user turn can make several model calls while using tools, so costs are calculated per model request.
Estimated session$0.00
- Uncached input
- —
- Cache reads
- —
- Uncached prefixes
- —
- Cache writes
- —
- Output
- —
- Without caching
- —
The first request starts cold unless marked otherwise. Output is billed separately from context growth because reasoning tokens are not always retained. This remains a directional estimate: providers differ in eligibility, rounding, and retention.
Compatibility flags
Effective values after applying Pi's API defaults and model overrides.
| Feature | Value |
|---|---|
supportsDeveloperRole | Yes |
sendSessionIdHeader | Yes |
supportsLongCacheRetention | Yes |