Function integration_line 

pub fn integration_line(shell: Shell, bin: &str) -> String

The single line appended to the shell rc file.

Drift resistance

For bash/zsh/pwsh/nu the line either re-evaluates the export at every shell start (eval "$(runex export ...)", Invoke-Expression (& runex export pwsh ...)) or re-writes the shell-side script every start (nu’s save --force). That makes the integration drift-proof: upgrading runex automatically picks up the latest template the next time the shell starts.

clink is the exception. The lua file lives outside any rcfile reload pathway, so users have to re-run runex init clink after a runex upgrade. runex doctor flags this drift via the integration:clink check (see crate::integration_check::check_clink_lua_freshness).