---
description: Require source-level fixes for malformed or polluted domain data
alwaysApply: true
---

# Root-Cause-First Bug Fixing

When malformed, stale, duplicated, or unexpected data appears in the UI:

1. Do not start with a UI filter, hidden row, fallback label, or string-pattern special case.
2. Determine whether the value is persisted/remote domain data or only a presentation defect.
3. Inspect the authoritative source and trace all transformations and writers to the earliest boundary that created the invalid state.
4. Fix the invariant at that boundary: input parsing, API/RPC ingestion, persistence, sync reconciliation, or canonical state projection.
5. Add a regression test at the producing boundary. A render/selector test alone is insufficient.
6. Handle historical pollution separately: inventory dependencies, confirm destructive cleanup, clean narrowly, and read back the authoritative source.
7. UI filtering is allowed only for an explicit product requirement or as defense-in-depth after the source fix. Never use it as the sole fix for invalid upstream data.
8. Do not change adjacent valid behavior without an explicit request.

Before declaring success, report: authoritative source, root cause, producing write path, source-level invariant, historical remediation, and verification evidence.

Any UI predicate that hides malformed data must cite an explicit product requirement. If the value violates the domain model, reject the UI-only patch until the producing path is fixed and regression-tested.