Codex skill: drift detection + apply for a scaffolded harness.
What it does
Re-renders the template that produced the harness against the current generator version, using the same vars the original scaffold used. Computes a 3-bucket plan:
| Bucket | Meaning |
|---|---|
| added | upstream template now has files the harness doesn't |
| removed | upstream template no longer has files the harness does |
| changed | upstream and harness differ; sub-classified clean vs conflict |
A clean change means the harness's version equals the original generation — apply safely. A conflict means the user edited the file post-scaffold; the apply step writes either Git-style inline markers or a .rej sidecar for manual merge.
Usage from Codex
/upgrade-harness # dry-run on cwd
/upgrade-harness path=./my-harness
/upgrade-harness path=./my-harness apply=true
/upgrade-harness path=./my-harness apply=true conflict=rej
Equivalent CLI
harness upgrade ./my-harness # dry-run
harness upgrade ./my-harness --apply # apply, inline conflicts
harness upgrade ./my-harness --apply --conflict=rej # apply, .rej sidecars
Lifecycle position
scaffold (create-agent-harness)
↓
edit (you)
↓
upgrade (this skill) <- catches up to the latest template
↓
sign / verify / publish
Exit codes
| Code | Meaning |
|---|---|
| 0 | No drift OR clean apply (no conflicts) |
| 1 | Unresolved conflicts after apply, OR not a generated harness, OR template missing |
| 2 | Bad --conflict= value |
CI workflows can gate on exit 1 to flag unresolved conflicts.