Canonical Chat runtime

Web Chat has one application runtime: Canonical Chat. ChatRuntimeProvider composes the Canonical store, IndexedDB repository, synchronization coordinator, outbound coordinator, and shared chat surface. There is no Legacy Message store, REST client, controller, or runtime selector in the application layer.

The authenticated online shell may read /v1/users/me/protocol-capabilities for optional Canonical limits. A missing or invalid response uses conservative Canonical defaults; it never selects another runtime. Browser and Electron Socket owners always request messageProtocolVersion='canonical-v1' in a fresh device.hello. Resume preserves the protocol confirmed by the current session.

Ownership

features/canonical-chat/              UI, controller, hooks, runtime, and React composition
lib/canonical-chat/                   Protocol, store, persistence, sync, projection, voice, and outbound modules
packages/realtime-contract/           Validated Socket schemas
packages/*-adapter/                    Browser and Electron Socket owners

Network responses and Socket events enter the same Canonical snapshot reducer. React renders projections from the store; it does not build a second message timeline.

Offline authenticated mode

The host-managed authenticated shell mounts OfflineCanonicalChatRuntimeProvider when the account is available but the host reports offline. This opens the same user-scoped Canonical IndexedDB repository and renders its cached active/latest segment. Local-only mode does not start WebSocket, bootstrap/catch-up, outbound delivery, read-position writes, remote search, or thinking polling. Composer submission remains blocked until the online runtime remounts.

Detailed DTO, cursor, segment, and synchronization rules live in apps/web/src/lib/canonical-chat/README.md.