story-splitting

Split oversized user stories using SPIDR (Spike / Path / Interface / Data / Rule) or Richard Lawrence's 9-pattern catalog. Vertical value-slicing with V-test gating (reject horizontal technical slices). Post-split INVEST check per sub-story. Recommended order (walking skeleton → risk-reducing → value → quick wins → edges). Flags when NOT to split. Mermaid diagrams with optional PNG export.