D035 - The worker protocol is serialisable data

Status: decided Date: 2026-08-19

Shim and worker messages are serde types defined apart from their transport, and service operations take and return serialisable values.

Why: the transport can change without the protocol moving. An operation handing back rich types that reference a loaded module cannot cross a process boundary.

Rejected:

• Protocol defined by the transport: a transport change becomes a protocol change.
• Service operations returning references: unusable from the worker.