upgrade-harness

> 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

bash
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.