Unity Review — Unity-Specific Gotchas

This skill is detection only. Each item below is a known trap that compiles clean, passes unilyze, and still breaks at build time, on device, or across a domain reload. Run the detection command, decide ✓ (safe / not present) or ✗ (trap present), and list affected files. You do not fix; you surface.

Run review-triage first for the project profile — the XR items only apply if triage recorded an XR stack.

For each trap: Symptom (what the developer sees), Cause (the underlying mechanism), Detect (the command to run), Severity.

1. Prefab Variant m_AddedComponents with implicit fileIDs

• Symptom: components added on a Prefab Variant silently vanish in builds or when the base prefab is restructured.
• Cause: a variant records added components as overrides keyed by the base prefab's serialized fileID. If the base prefab is edited so those fileIDs shift, the override dangles and Unity drops the component with no error.
• Detect: grep -rln "m_AddedComponents\|m_RemovedComponents" <project>/Assets --include=*.prefab then open each and confirm no override references a stripped/missing fileID.
• Severity: high (silent build-time loss).

2. ARFoundation SubsystemLifecycleManager AddComponent ordering