Custom iOS AI keyboard extensions: SwiftUI, LLM APIs & low latency

Keyboard extensions run under tight memory and network limits. Users expect instant suggestions while typing in Messages, Mail, or Slack—so AI keyboard products fail when they treat the extension like a full app. Architecture must keep inference off the critical path where possible: debounce keystrokes, cache frequent completions, and stream only when it helps.

Never embed provider API keys in the extension bundle. A thin backend proxies requests, applies rate limits, and rotates credentials. Firebase or similar handles auth tokens tied to subscription status so free users cannot hit your LLM bill unchecked.

SwiftUI and UIKit both work in extensions; the UX win is staying invisible—minimal chrome, clear loading states, and graceful offline behavior. App Review scrutinizes keyboards that access too much text; document data use and offer opt-in flows.

Clients search for “AI keyboard developer iOS” and “LLM keyboard extension.” The deliverable is measurable latency and reliable suggestions in real apps, not a demo video. Load testing and token budgeting belong in v1.

I have integrated LLM services into native keyboard workflows with scalable backends. If you are productizing AI-assisted typing, nail one language and one use case first—rewrite, tone, or autocomplete—before expanding models.