Context

When using a personal lsv2_pt API key with the LangSmith Python client, you may encounter 403 Forbidden errors when calling endpoints such as /runs or /sessions. For example:

from langsmith import Client
client = Client(api_key="lsv2_pt_...")

list(client.list_projects())
# -> 403 Forbidden for url: https://api.smith.langchain.com/sessions?limit=100&offset=0

This can happen even when using the default workspace and without setting any custom endpoint or workspace ID environment variables.

Answer

There are a few things to check and try when encountering this issue:

1. Verify your API key type. Make sure your key starts with lsv2_pt (personal token) and not lsv2_sk (service key), as these have different permission scopes.

2. Specify the Workspace ID explicitly. Try passing the workspace_id parameter when instantiating the client:

   client = Client(api_key="lsv2_pt_...", workspace_id="your-workspace-id")

   You can find your Workspace ID in the LangSmith UI, as shown below:

   

3. Check your environment variables (especially in Jupyter/Colab environments, where variable caching is common). Run the following to verify they are set correctly:

   import os
   print(os.getenv("LANGSMITH_PROJECT"))
   print(os.getenv("LANGSMITH_TRACING"))
   print(os.getenv("LANGSMITH_ENDPOINT"))
   print(os.getenv("LANGSMITH_API_KEY"))

4. Clear cached environment variables if the output does not match your .env file:

   utils.get_env_var.cache_clear()

   Then reload your environment variables:

   from dotenv import load_dotenv
   import os
   load_dotenv(<path to .env file>, override=True)

5. Regenerate your API key. If the above steps do not resolve the issue, try revoking your existing API key and generating a new one from the LangSmith UI, then update your code or environment variables with the new key.