ISSUE Race condition in update/download queue when user input conflicts with the "download complete" state transition, resulting in an invalid App ID lookup for the next-most game in the "Up Next" queue. The downloads complete successfully in the background, however the client's UI state becomes desynchronized. OS Windows 11 [24H2 Build 21600] Steam Client 1759461205 STEPS - Have at least three games in the "Unscheduled" queue. - Start downloading the first game by moving it to "Up Next." - Move a second game to the "Up Next" queue. - Wait until the first game is in its final stage (eg. "Finishing installation" or "Completing Download" at 100%). - At that exact moment, drag a third game from "Unscheduled" and place it over-top the second game in the "Up Next" queue. RESULT - A black error screen appears with an error message: "Game App ID not found." - The download queue UI becomes unresponsive. - However, after refreshing the client download view (by changing pages and returning), all three games show as "Completed," indicating the downloads and installations succeeded in the background. EXPECTED RESULT The "Up Next" queue should accept the reorder. The third game should be inserted into the "Up Next" queue, and the second game should start the download/installation process or be bumped down the "Up Next" queue without any errors. NOTES - Reproduced twice with games that have a 10-150MB download size. - The core issue seems to be a UI state desynchronization. The client throws a UI error when trying to update the "Up Next" queue state during the hand-off, but it appears that the backend download manager continues its operations successfully. I assume that this is a client-side rendering/logic bug rather than a core download system bug.