Build Live Driver Tracking with SSE and an AI Coding Workflow

Starting from an existing Node backend skeleton, build a frontend feature that uses Server-Sent Events to show live delivery-driver tracking. Work incrementally with an actual coding assistant and explain your prompts, model-selection reasoning, verification, and pull-request organization. ### Constraints and Clarifying Questions The backend event schema and milestone details are not supplied. Define a small contract for driver or delivery identity, location, event sequence, and observation time before generating code. State authentication, reconnect, and stale-location behavior as explicit implementation choices. The exercise concerns an existing backend integration, not designing an unrelated chat UI. ### What a Strong Answer Covers An end-to-end subscription, location updates, reconnect and cleanup behavior, stale or out-of-order events, a staged AI-assisted workflow, and evidence from focused unit and browser checks. Explain how you review generated changes rather than treating tool output as validated. ### Follow-up Questions - How do you ensure a late event for a previous delivery cannot move the current delivery's marker? - What would you include in a PR so another engineer can verify the feature?