Sparse routing is an architectural pattern designed to allow a single, shared runbook to govern diverse, heterogeneous tasks without inducing control drift. Rather than encoding exhaustive, per-task procedures into the global workflow, sparse routing organizes control into:

1. A Thin Shared Runbook: Maintains a lightweight, general state backbone common across all tasks.
2. Semantic Triggering: Activates specialized pathways and policies derived from observable task semantics rather than static task identifiers.
3. Late State-Local Checks: Enforces specialized transition checks and constraints only when current task context and workspace artifacts explicitly demonstrate elevated downstream failure risk.

This structure preserves broad agent autonomy on routine tasks while selectively enforcing stringent controls only where specific failure modes are likely to occur.