Troubleshooting Gemini CLI API Key Configuration Issues

A developer encountered an issue where the GEMINI_API_KEY environment variable was not being recognized when trying to use the Gemini CLI. After an in-depth investigation, it was discovered that the Gemini CLI’s key lookup mechanism has a significant flaw: it prioritizes checking for a .env file in the project directory, and if it can’t find one, it throws an error directly without falling back to the .env file in the user’s home directory. This design can easily lead to conflicts in a multi-project environment, reducing productivity. The user, in collaboration with Gemini 3 Pro, identified the root cause of the problem and pointed out that this configuration logic is not intelligent enough. The article details the problem’s symptoms, the troubleshooting process, and suggestions for optimization, providing a practical reference for developers who rely on the Gemini CLI and helping them avoid similar configuration pitfalls.