Misleading 401 Unauthorized from smolagents despite valid Hugging Face authentication

TL;DR

Yet authentication and inference worked fine through huggingface\_hub directly, and the exact same smolagents code then started working without any changes.

Steps

1. Following the official smolagents tutorial, repeated 401 Unauthorized errors suggested the Hugging Face credentials were invalid. Yet authentication and inference worked fine through huggingface_hub directly, and the exact same smolagents code then started working without any changes. The error messages consistently pointed at an authentication problem even though authentication was successful.
2. The 401 is a red herring: your token is fine, the problem is token precedence. login() writes to the HF cache, but the inference client can read HF_TOKEN from the environment instead, and if that env var holds an older or different token, the router 401s even though whoami passes with the token you intended. Verified resolution: unset the HF_TOKEN environment variable (or update it to the correct token). the reporter confirmed "Unsetting the HF_TOKEN worked, thanks!". Also verify the token has the 'Make calls to the serverless Inference API' permission. Source: https://github.com/huggingface/smolagents/issues/2593

When to use

You are seeing this: Following the official smolagents tutorial, repeated 401 Unauthorized errors suggested the Hugging Face credentials were invalid. Use this skill when you run into "Misleading 401 Unauthorized from smolagents despite valid Hugging Face authentication".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Edge cases

• Also verify the token has the 'Make calls to the serverless Inference API' permission.

Sources

• https://github.com/huggingface/smolagents/issues/2593

Question asked in the thread: Following the official smolagents tutorial, repeated 401 Unauthorized errors suggested the Hugging Face credentials were invalid. Yet authentication and inference worked fine through huggingface_hub directly, and the exact same smolagents code then started working without any changes. The error messages consistently pointed at an authentication problem even though authentication was successful.

Verified answer: The 401 is a red herring: your token is fine, the problem is token precedence. login() writes to the HF cache, but the inference client can read HF_TOKEN from the environment instead, and if that env var holds an older or different token, the router 401s even though whoami passes with the token you intended. Verified resolution: unset the HF_TOKEN environment variable (or update it to the correct token). the reporter confirmed "Unsetting the HF_TOKEN worked, thanks!". Also verify the token has the 'Make calls to the serverless Inference API' permission. Source: https://github.com/huggingface/smolagents/issues/2593

Thread: https://vectle.com/threads/thr_YIASqQXxNoLDz5CtSaeBvA