By name: moss-lineage-break-trace description: Use when a MOSS API result, displayed value, golden sample, source row, report date, lineage field, or page contract does not tie out and the cause must be traced.
MOSS Lineage Break Trace
Use this skill to root-cause mismatches instead of patching symptoms. It adapts GL break tracing patterns to MOSS source lineage and page verification.
Break Buckets
Classify the mismatch before fixing it:
| Bucket | Typical Signal |
|---|---|
| Source-date break | requested date, resolved date, trade date, natural date, or fallback date differs |
| Unit break | yuan / ten-thousand yuan / hundred-million yuan / percent / bp mismatch |
| Grain break | row-level value compared to aggregated value, wrong grouping, duplicate rows |
| Rule break | wrong formula, rule version, cache version, or formal/scenario mix |
| Mapping break | product/category/security/account maps to a different canonical key |
| Null-state break | null, 0, undefined, NaN, or missing row semantics differ |
| Presentation break | backend value correct, adapter/formatter/component changes meaning |
Trace Path
- Capture the failing assertion or visible mismatch with exact value, date, metric ID, route, and endpoint.
- Pull authoritative contract and lineage evidence first when MCP servers are available.
- Inspect the concrete data source and report dates with read-only catalog queries or existing tests.
- Walk the implementation path from repository/service/core calculation through API schema to frontend adapter and component.
- Identify the first layer where expected and actual diverge.
- Fix that layer only; do not compensate downstream unless the downstream layer caused the break.
- Add a regression test at the layer where the divergence first appeared.
Root Cause Statement
Use this form:
<layer> produced/displayed <wrong value/state> because <specific evidence-backed cause>.
Include owner area, expected clearing/fix action, and residual risk if evidence was unavailable.