Module queue 

Event queue — EventQueue trait + two impls.

Adapters that buffer events for later transmission depend on the EventQueue trait so the choice of in-memory vs. persistent backing is a deployment detail. Both impls have the same FIFO semantics (oldest event drained first); only PersistentEventQueue survives process restart.

• InMemoryEventQueue — Mutex<VecDeque<OwnedEvent>>. Default for tests and for adapters that consider events ephemeral.
• PersistentEventQueue — backed by redb at a path under AppPaths::data_dir(). Pure-Rust, no C deps, ~250–400 KB binary footprint vs. SQLite’s ~1 MB. Atomic writes, MVCC reads, single-writer.

Structs

InMemoryEventQueue

Bounded FIFO event buffer with Send + Sync access.

PersistentEventQueue

redb-backed event queue. Send + Sync — internal Mutex wraps the Database handle so adapter UI-thread pushes and worker- thread drains don’t conflict.

Enums

PersistentQueueError

Traits

EventQueue

FIFO event buffer with capped size and oldest-eviction.