Manage React conversation state

Keep three kinds of state distinct: backend observations, application policy, and local presentation. This makes a partial answer, a disabled Send button, and an open sidebar understandable without treating them as one mutable store.

The React APIs are experimental, private source-build packages. The streaming example provides a concrete application owner.

Publish one coherent observation

The streaming application publishes creation, rows, busy, canSubmit, outcome, and error in a single frozen snapshot. These are example application fields, not required fields of useAgent.

On a session notification, the owner projects messages and publishes the next aggregate. Its getSnapshot returns that same object until a change. The view observes it and renders rows and controls from the same publication.

Keep content projection in this owner. createMessageContent manages Markdown documents and row reuse; content.project advances that owned content. Publishing prepared rows avoids changing a shared projection during React rendering.

Preserve backend-specific meaning

The private LangGraph session exposes a readonly values map. undefined means no current application-values map is observed; an empty object means an empty map was observed. The hook preserves this distinction and the concrete session type.

Observing values does not validate their schema, write backend state, or issue additional reads. Narrow unknown application values at the application boundary before presenting them. See the state-related runtime examples for an authored backend contract.

Keep local choices local

Draft text, disclosure expansion, and popup visibility can belong to React. They should not implicitly submit, recreate sessions, or change conversation identity. A new owner or conversation may intentionally reset those choices; merely receiving another token should not.

When replacing an owner, invalidate old asynchronous work before it can publish into the new selection. Dispose the old session and content at that owner boundary. Lifecycle describes this cleanup, while Render state covers editable presentation data.