## Diamond Recursion Scan (prefect) — CLEAN (deeper scan)

**Scan date:** 2026-03-29
**Pattern:** Recursive cycle/dependency check without visited set (CWE-407 diamond recursion, O(2^D))

### Files examined

- `src/prefect/cli/transfer/_dag.py:TransferDAG` — proper Kahn's algorithm, `visited: set[uuid.UUID]` — CLEAN
- `src/prefect/cli/transfer/_dag.py:has_cycles` — three-color DFS with `color` dict — CLEAN
- `src/prefect/utilities/collections.py:visit_collection` — tree-walker, not DAG — CLEAN

### Verdict: CLEAN — no diamond recursion CWE-407 found beyond existing pre-0001..0002
