I’m working with LangChain and LangSmith to build a testing system for my language model prompts. Everything was running smoothly until I had to generate a new OpenAI API key after deleting the old one.
I updated the new API key in my environment variables file and confirmed it works by testing it directly with OpenAI’s chat completion endpoint. I also went into LangSmith and manually updated the key in two places: the playground’s secrets section for my specific prompt, and in my organization settings under the secrets tab.
But when I run the arun_on_dataset method in my Python script, I keep getting this authentication error:
AuthenticationError("Error code: 401 - {'error': {'message': 'Incorrect API key provided: sk-M4KLP***************************************RGxT. You can find your API key at https://platform.openai.com/account/api-keys."
The weird thing is that the error message shows the prefix of my old deleted API key, not the new one I set everywhere. My code hasn’t changed at all from when it was working before.
Where else might the old API key be cached or stored that I need to update?
Been there. API key caching is a nightmare with multiple services and environments.
Your old key’s probably stuck in your runtime or Python session. Even after updating the env file, your Python process might still have the old value in memory.
Restart your Python interpreter completely. Using Jupyter? Restart the kernel. Running scripts? Close everything and start fresh.
Check for .env files in parent directories too - they might override your changes. These sometimes load in weird order.
Honestly, this whole API key juggling between different services is why I moved everything to automation workflows. Instead of managing keys across LangChain, LangSmith, and your local environment, I set up the entire testing pipeline in Latenode.
One place for all API credentials. Need to update keys? Do it once. The workflow handles LangSmith dataset testing automatically without worrying about cached or overridden environment variables.
Way cleaner than debugging where keys are stuck in memory.
check ur global env vars too, not just .env. sometimes an old key is set and messes with things. also, langsmith might cache the key, so logging out and in could help refresh it.
This just happened to me! LangChain was the problem - it stores API keys in its own config that sticks around even after you change your environment variables. Delete the LangChain config directory (usually ~/.langchain/ or check for hidden LangChain folders in your user directory). Let LangChain rebuild the config files with your new environment variables. Also check if you’ve got any hardcoded API key assignments in your Python code like openai.api_key = "..." - easy to forget about those. Since the error shows your old key prefix, it’s definitely cached somewhere locally, not a server issue.
Docker containers could be the problem. If you’re running your script in a container, the old API key might be baked into the image or passed through docker-compose environment variables you haven’t updated. I had this exact issue last month - spent hours checking local configs only to find my container was still using the old key from the build process. Also check IDE-specific environment configs. VSCode, PyCharm, and other editors sometimes keep their own environment variable settings that override system ones. Since you’re seeing the old key prefix in the error, it’s definitely cached somewhere in your execution environment, not a LangSmith server issue.
Check your shell profile files too. The old key might be hardcoded in .bashrc, .zshrc, or .bash_profile. These override whatever you put in .env files.
I hit this exact issue six months ago. Had the old API key exported in my .zshrc from when I first set up the project. Even after updating everything else, my terminal kept loading that old key on startup.
Run env | grep OPENAI in your terminal to see what’s actually loaded. If the old key shows up, it’s coming from your shell config.
Also check pytest config files or test runners - they might have their own environment settings. Test frameworks sometimes cache environment variables between runs.
Since you’re seeing the old key prefix in the error, it’s definitely getting loaded from somewhere in your local setup. Not a LangSmith server issue.