# Upgrade and Rollback Runbook

The compatibility gate is mandatory before every deployment or rollback:

```bash
bash packages/casan-harness/scripts/bash/upgrade-compatibility.sh check \
  --from 1.0.0 --to 1.0.1
```

Only an explicit rule in `compatibility-matrix.json` can permit a version pair.
Before rollout, verify provenance, create and verify a state backup, smoke the
extracted artifact, deploy immutable image digests, and verify an Evidence Pack
after deployment. A rollback requires the same gate with `--rollback`, plus an
approved change record and a verified backup.

Do not infer compatibility from matching image tags, passing unit tests, or
successful container startup. Add and review a new matrix entry before any
cross-minor or cross-major migration.