stack_host_copy is the copy: analogue of stack_host_template: it folds the IS_STACK_HOST gate into the module so callers do not silently fail on hosts whose destination tree is owned only by the stack host. In swarm an app's compose / build-context directory (/opt/compose/<app>) exists only on the manager, so a bare copy: into directories.instance also ran on workers and aborted the play with 'Destination directory does not exist'.
Migrate the six compose-dir copy tasks (baserow, jenkins, bookwyrm, postmarks, yourls, openldap) to stack_host_copy and drop the now-redundant when: IS_STACK_HOST. A new drift-guard lint test (test_stack_host_copy_migration) flags any future bare copy: into the compose dir, and a unit test covers the wrapper.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
kevinveenbirkenbachandClaude Opus 4.8