Project AURIONAI Use-Cases Research & Innovation
code

GPT-5.1-Codex-Max

A version of GPT-5.1-Codex optimized for long-running, long-horizon agentic coding tasks. OpenAI shut it down in the API on 23 July 2026.

OpenAIOpenAIUSAGPT-5Family
OpenAI
Levelmodel
Classcode
Parametersnot in the notes
Context400,000
Released4 Dec 2025
Opennessproprietary
Runs onnot in the notes
Statusshut down

Lineage

finetune
GPT-5.1-Codex to GPT-5.1-Codex-Max: finetune, medium confidenceGPT-5.1 to GPT-5.1-Codex: finetune, medium confidenceGPT-5.1GPT-5.1OpenAI, Nov 2025GPT-5.1-CodexGPT-5.1-CodexOpenAI, Nov 2025GPT-5.1-Codex-MaxGPT-5.1-Codex-MaxOpenAI, Dec 2025
OpenAIGPT-5.1-Codex is the parent (finetune)medium confidencemodel card
Where this comes from
Parent and child relations from model cards, Hugging Face base_model fields and the genealogy tables of the research notes. The tree shows two generations each way, 3 models. Confidence and evidence are the notes' own.

R&D Topics

Agentic software engineeringproduced byCode language modelsproduced by

Identity

Developer
OpenAI
Family
GPT-5
Released
4 Dec 2025 sourcesinferred from page
Weights published
–
Record checked
11 Oct 2026
Where this comes from
Developer and dates from the research notes. Release date is the vendor's public announcement; weights date is when open weights were published.

Architecture and Size

Architecture
not in the notes
Total parameters
– sources
Active parameters
–
Checkpoint parameters
–
Context length
400,000 tokens
Input
text, image
Output
text
Where this comes from
Parameter counts as the developer states them. Where the checkpoint holds a different total, both are shown (register A16).

Openness and Access

Openness
proprietary
Licence
Proprietary sources
Access routes
API
Where this comes from
The licence file governs over registry tags and aggregator labels.

Deployment

Runs on
not in the notes
Footprint
128,000 max output tokens; Responses API only. Release date is the API changelog date; the openai.com announcement page refused automated access
Runtimes
not in the notes
Where this comes from
Deployment tiers and runtimes as named in the notes. Footprint is the notes' figure, not a measurement by AURION.

Indonesia

Indonesian support
not stated
Regional languages
not in the notes
Jakarta hosting
unknown
Languages
not in the notes
Where this comes from
Indonesia fields are carried on every model; unknown is an allowed value.

Benchmark Results

The notes record no benchmark result for this model.

Industry Use Cases

No industry use case links this model.

Sources

  1. developers.openai.com/api/docs/models/gpt-5.1-codex-max.md https://developers.openai.com/api/docs/models/gpt-5.1-codex-max.md
  2. developers.openai.com/api/docs/changelog.md https://developers.openai.com/api/docs/changelog.md
  3. developers.openai.com/api/docs/deprecations.md https://developers.openai.com/api/docs/deprecations.md

To cite this page: Project AURION, AI Use-Cases Research & Innovation, "GPT-5.1-Codex-Max", https://aurion.semai.id/models/openai-gpt-5-1-codex-max/, records of October 2026.