Hosted code and live replacement
Hosted code runs inside a substrate but remains actor-tier code. The host owns isolation and scheduling; the guest owns application state and mail behavior.
| Surface | Chapter | Use it for |
|---|---|---|
| Wasm actor modules | Components and lifecycle | first-class mailboxes, state, replies, replacement |
| Names/contracts/transforms | Inventory and transforms | engine-specific discovery plus the MCP build's bounded transform inventory |
Component bytes in the hub registry are artifacts. A loaded component is an engine-local instance. Keep these identities separate when building, uploading, selecting, loading, and replacing.
Read Guest and native boundaries before changing exports, schema, feature tiers, or state migration.