Schema Author

Use this skill when a task changes the active Brain schema pack in Brain/_brain.yaml or reviews content against that schema.

Workflow

1. Inspect the active schema pack with schema_inspect (view="active_pack") or o2b brain schema --json.
2. Check current usage and findings with schema_inspect views stats, lint, and orphans.
3. Explain candidate tokens with schema_inspect (view="explain_type") before renaming or deleting them.
4. Preview the batch first with schema_apply_mutations (dry_run=true) or o2b brain schema apply --dry-run --mutation ...: it returns the pack that would result and its diff and writes nothing at all - no config write, no audit record, no lock file. It runs the same pack validator the apply runs, so a batch that validator rejects raises identically in both. It does not run the two checks that exist only because the apply writes: the vault-identity write guard, and the atomic writer's re-parse of the rendered YAML. A batch that renders to unparseable YAML previews clean and fails on apply, so treat a clean preview as "the mutations are valid", not as "the apply will succeed".
5. Apply schema changes only through schema_apply_mutations or o2b brain schema apply --mutation ... so writes are locked, atomic, and audited.
6. Re-run lint/stats after mutation and report changed tokens plus any remaining findings.

Mutation Notes

Supported operations are add_type, remove_type, update_type, add_alias, remove_alias, add_prefix, remove_prefix, add_link_type, remove_link_type, set_extractable, and set_expert_routing.

Schema tokens must be lowercase normalized tokens accepted by Open Second Brain schema validation. Prefer small, durable tokens over project-specific phrasing unless the schema pack is explicitly project-scoped.