Summary

lychee-action fails with lychee: command not found on self-hosted runners (and any environment) where $HOME resolves to a different path between composite-action steps. The action ends up adding one directory to $GITHUB_PATH and installing the binary into a different one.

Where it goes wrong

In action.yml, $HOME is evaluated independently in two separate bash shells:

- name: Set up environment
  run: |
    echo "$HOME/.local/bin" >> "$GITHUB_PATH"   # ← $HOME #1
    mkdir -p "$HOME/.local/bin"
  shell: bash

# ...later...

- name: Install lychee
  run: |
    install -t "$HOME/.local/bin" -D "${{ steps.lychee-setup.outputs.temp_dir }}/lychee"   # ← $HOME #2
  shell: bash

On ubuntu-latest both $HOMEs resolve to /home/runner, so it works. But on runners where each step gets a fresh ephemeral $HOME (we hit this on an internal self-hosted runner; actions/checkout itself logs Temporarily overriding HOME='/workspace/_temp/<uuid>' post-step), the two paths diverge. PATH points at the old $HOME, install lands in the new one, and entrypoint.sh errors with:

entrypoint.sh: line 49: lychee: command not found
##[error]Process completed with exit code 127.

Repro

Any runner that resets/overrides $HOME between composite-action steps. The clearest sign in logs is:

• Step "Install lychee" reports success
• Step "Run Lychee" immediately errors with lychee: command not found
• Earlier setup step also added a different $HOME/.local/bin to $GITHUB_PATH

Suggested fix

Install into a path that does not depend on $HOME. The natural choice is $RUNNER_TEMP — guaranteed-writable, stable across steps within a job, and exactly what it's for:

- name: Set up environment
  run: |
    echo "$RUNNER_TEMP/lychee/bin" >> "$GITHUB_PATH"
    mkdir -p "$RUNNER_TEMP/lychee/bin"
  shell: bash

…and use $RUNNER_TEMP/lychee/bin in the install step too. This also makes the action robust in containers where $HOME may be unset or read-only.

For comparison, jdx/mise-action is a JS action and uses the Actions toolkit's core.addPath() from inside Node — same intent, but it sidesteps the "$HOME evaluated twice in two shells" pitfall entirely.