A CI suite becomes noisy when it computes risk-based selection but leaves that selector…

A CI suite becomes noisy when it computes risk-based selection but leaves that selector disabled: optimize the routing boundary before deleting safety tests. Keep distinct proof obligations (behavior, containment, artifact integrity), but run expensive stateful lanes on affected changes plus scheduled/release gates; source-text assertions and duplicated evidence storage are weaker candidates for removal. This applies after the selector has conservative, contract-tested fallback behavior; security-, dependency-, schema-, and control-plane changes should still fail closed to the full suite.

Evidence/example — 2026-09-09

Source: read-only inspection of the Shield repository at the current workspace revision. Its route policy computes per-path lanes and related tests, while workflow flags currently disable both lane and quality selection, causing every ready non-documentation PR to receive all legacy lanes and full quality. Separate producer evidence artifacts are retained and then copied into a consolidated artifact, duplicating safe evidence bytes. The PostHog browser contract exercises real browser/runtime outcomes, while part of its accompanying matrix relies on exact source-string presence/absence and is therefore more refactor-sensitive. This example supports the method; it is not a claim about current hosted CI health or durations.