Chat

Realm Chat is where direct messages between two people live. The thread, its messages, its membership, and its read state all exist exactly once — in Realm, not on your desktop and not inside one login session. That single thread is what every surface reads.

Substrate

Realm Chat admits exactly one substrate:

Substrate	Purpose
DIRECT	Two-party human direct messaging

Any other chat shape is rejected before canonical chat state is created, mutated, or returned. LocalAgent conversations remain Runtime-owned and do not become Realm human-chat threads.

Reader Scenario: A Direct Conversation

You direct-message another user.

1. Direct substrate. Realm admits a DIRECT thread between you and the other user.
2. Send. Your message is committed to the thread.
3. Realtime delivery. Other user sees the message via Socket.IO realtime delivery.
4. Read state. Read state is canonical — your client's "read" is recorded in the thread.

The thread is canonical Realm truth. Switching devices does not require re-syncing; the canonical thread is the source.

Reader Scenario: Read State Across Devices

You read a message on Desktop. You open the same conversation on Avatar.

1. Read on Desktop. Read state is committed to Realm.
2. Open on Avatar. Avatar reads the canonical thread, including read state.
3. Avatar sees you've read it. No silent re-display of read messages.

Read state is platform truth, not per-surface state. This is what makes multi-surface chat coherent.

How Chat Relates To Other Realm Surfaces

Surface	Relation
Social (R-SOC-*)	Friendship gates direct chat preconditions; social does not own the thread itself
Truth (R-TRUTH-*)	Chat that affects world meaning may participate in truth
World History (R-WHIST-*)	Chat events that contribute to canonical history append there
Runtime ConversationAnchor	Runtime owns LocalAgent conversation continuity separately from Realm human chat

What Chat Does Not Do

Concern	Why not
Own conversation continuity	Runtime ConversationAnchor owns that
Own agent execution	RuntimeAgentService owns that
Own UI rendering	Desktop chat surface owns that
Admit non-direct chat shapes	Realm Chat is limited to direct human threads

Source Basis

• .nimi/spec/sdks/realm-consumer.authority.yaml
• .nimi/spec/runtime/agent-participation.authority.yaml