The pre-stream error boundary covers both the live-session flush barrier and the persistence read, but its response attributed every failure to reading storage. A flush failure therefore produced a misleading diagnostic even though the response correctly withheld private backend details.\n\nUse preparation as the shared operation name and cover the flush-failure path explicitly. Both preparation stages now retain one stable, path-safe HTTP 500 without pretending to identify the failing stage.
Tianyi Cui
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