Worked on the jdx/mise repository to address a critical bug in environment variable propagation for the MISE CLI. Focused on ensuring that the MISE_ENV variable is reliably injected into spawned shells when using the -E flag with 'mise exec' and 'mise en', the developer reinforced environment handling logic in Rust and Bash. Complemented the fix with comprehensive end-to-end tests to validate correct environment behavior, including configuration discovery and override precedence. This work improved script reliability and preserved environment context across shell invocations, demonstrating a methodical approach to CLI development, robust testing, and cross-environment scripting in Rust-based tooling.