Context: v0.11.0 migration orchestrators need a safe way to re-apply the
schema against an existing brain without risking a config flip. Today
running bare `gbrain init` with no flags defaults to PGLite and calls
saveConfig, which would silently overwrite an existing Postgres
database_url — caught by Codex in the v0.11.1 plan review as a
show-stopper data-loss bug.
The new --migrate-only path:
- loadConfig() reads the existing config (does NOT call saveConfig)
- errors out with a clear "run gbrain init first" if no config exists
- connects via the already-configured engine, calls engine.initSchema(),
disconnects
- --json emits structured success/error payloads
Everything downstream in the v0.11.1 migration chain (apply-migrations,
the stopgap bash script, the package.json postinstall hook) will invoke
this flag rather than bare gbrain init.
test/init-migrate-only.test.ts: 4 tests covering the no-config error
path, --json error payload shape, happy-path with a PGLite fixture
(verifies config.json content is byte-identical after the call — the
real invariant), and idempotent rerun.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
