This is a TIL (“Today I Learned”) post. I expect it to be useful to my future self and maybe to others, but it is meant to be a quick, informal way to capture something I learned rather than a polished presentation.
I encountered an error when running Python scripts that used llama_index to interact with LLM provider APIs:
httpcore.LocalProtocolError: Illegal header value b'Bearer <REDACTED KEY>\r'The \r at the end of the header value was the problem. That character originated from an example .env file that I was copying and modifying. It contained carriage return (\r) characters at the end of each line, likely due to being created or edited on a Windows system and then used in a Linux environment that expects line feeds (\n).
These characters were invisible in standard editors but could be revealed using cat -vET:
$ cat -vET .env.example
export OPENAI_API_KEY='YOUR_OPENAI_KEY_HERE'^M$
export GOOGLE_API_KEY='YOUR_GOOGLE_KEY_HERE'^M$
export ANTHROPIC_API_KEY='YOUR_ANTHROPIC_KEY_HERE'^M$The ^M represents the carriage return character. When the environment variables were loaded, these carriage returns were included as part of the API key strings. The httpx library (used by the openai library) correctly identified this character as illegal in an HTTP header value, leading to the LocalProtocolError.
Creating a new .env file from scratch resolved the issue. The carriage return character no longer appeared:
$ cat -vET .env.example
export OPENAI_API_KEY='YOUR_OPENAI_KEY_HERE'$
export GOOGLE_API_KEY='YOUR_GOOGLE_KEY_HERE'$
export ANTHROPIC_API_KEY='YOUR_ANTHROPIC_KEY_HERE'$And the script ran successfully.