The same name is exported from multiple files. Barrel re-exports collide silently and importers can't tell which one they got. The check runs in the engine's finalize pass — per-file run collects export names into the shared corpus, then finalize groups by name and emits one Issue per duplicate set with the canonical occurrence as the primary span and the rest as related: Vec<RelatedSpan>.

// src/users.ts
export function format(u: User) { /* ... */ }   // flagged

// src/posts.ts
export function format(p: Post) { /* ... */ }   // also flagged (related)

// fix: namespace, rename, or pick one canonical home
export function formatUser(u: User) { /* ... */ }
export function formatPost(p: Post) { /* ... */ }

# cofferdam.toml
[checks."Design.DuplicateExportName"]
severity = "low"   # demote to info-only if your project relies on barrel collisions