Refactor a Chatbot Codebase

You are given a piece of chatbot-related code/module that suffers from poor readability, duplicated logic, and inconsistent edge-case handling. Refactor it while preserving external behavior. Requirements: Keep the public interface unchanged (function signatures / I/O protocol as provided). Improve structure: remove duplication, clarify responsibilities, use clear naming. Handle edge cases consistently (empty input, error paths, timeouts/cancellation, as constrained by the prompt). If requested, add unit tests or a minimal verification harness. Explain what you changed and why.