TypeScript Frontends for AI Products That Stream

Chat UIs look simple until tokens arrive out of order, the user navigates away, or the server retries mid-stream.

Model the client state machine: idle, streaming, error, cancelled. If everything is a boolean soup, race conditions win.

Prefer typed event payloads over appending raw strings from SSE without schema. Parsing once saves debugging for weeks.

AbortController is not optional. Users hit stop; your fetch should stop spending money too.

Show progress and citations as first-class data, not afterthoughts stitched into markdown hacks.