Managing HTTP 429 status codes elegantly without middleware queuing logic.
When making concurrent requests across Anthropic and OpenAI directly from the client, sudden explosions of burst tokens will frequently trigger a 429 Too Many Requests wall.
Duplex leverages an Exponential Backoff recursion tree bounded to the client. We parse the `retry-after` header passively, alerting the user via non-blocking UI indicators, entirely avoiding locking the entire chat buffer for isolated endpoint failures.