Can't change python version to specified in project.toml file

LangSmith Product Help Deployment
1

I’m finding it very difficult to find support for this framework so I’m aiming to be part of the solution.

after upgrading some libraries and everything working fine on uv run langgraph dev locally, I was having major issues deploying to Langgraph Platform.

An error occurred while creating a Docker image from your specified GitHub repository. Please see your build logs (by clicking on the revision) for more information

react-agent, we can conclude that your requirements are unsatisfiable. And because only react-agent==0.1 is available and you require conclude that react-agent==0.1 cannot be used. 
Python>=3.12 and react-agent==0.1 depends on Python>=3.12, we can 
╰─▶ Because the current Python version (3.11.13) does not satisfy 
× No solution found when resolving dependencies: Using Python 3.11.13 environment at: /usr/local 9/10/2025, 7:06:57 PM [INFO] Step #17:  > [ 3/10] R
UN PYTHONDONTWRITEBYTECODE=1 uv pip install --system --prerelease=allow --no-cache-dir -c /api/constraints.txt -e /deps/*:
2

so from this doc Application structure - Docs by LangChain
I had the incorrect impression that only a few params were customizable in langgraph.json

The documentation is improving every day, and it seems more clear now that there are several params available

https://docs.langchain.com/langgraph-platform/cli#configuration-file
so in order to upgrade your server python version you have to specify it in langgraph.json

{
  "dependencies": [
    "."
  ],
  "graphs": {
    "agent": "./src/react_agent/graph.py:make_graph"
  },
  "env": ".env",
  "auth": {
    "path": "./src/react_agent/auth.py:auth"
  },
  "http": {
    "app": "./src/react_agent/app.py:app"
  },
  "python_version": "3.12"
}
3

Yup thats correct! We are working hard on improving the docs, so thank you for this feedback it is very helpful!