Reference

Integration checklist

60-second design-review scan. Companion to lesson 4.

Lesson 4 Lesson 5 Copy spectrum Playbook Type matrix Transfer Glossary

Reject clone if…

You need a JSON document (HTTP, file, log) → JSON.stringify, and design for loss.
You need methods / class identity / a versioned wire → custom serializer + revival.
Nested refs should stay shared → shallow copy.
The value is a reactive Proxy (Vue reactive / Pinia / MobX) → unwrap first, or clone a plain DTO. Proxies throw.
You are about to structuredClone and then postMessage / IDB put / pushState with no other reason → the API already clones.

Both sides still need the bytes → clone (or copy, then transfer one copy).
The API has no transfer list (BroadcastChannel, IndexedDB, History).
You listed a buffer that is not in the value → it still detaches and the clone never sees it.

Risk	What to check
Orphan list	Every transfer-list entry is reachable from the cloned / posted value
Typed-array list	List is `.buffer`, not the view
Detach surprise	Sender is done with those bytes; no later clone of them
Proxy / class	Payload is plain data, not a live reactive object or class instance
Cost	Graph size / frequency; patches or transfer before blaming the API
Loud vs silent	Functions/DOM throw on clone; JSON drops them. Know which algorithm you are on