The abstract capability flag forces every backend to state whether it owns per-session raw artifacts, but TypeScript cannot express that a true flag requires replacing the concrete unsupported default. Without an implementer-facing obligation, a backend could advertise support and then fail with a contradictory unsupported diagnostic on first use.\n\nDocument the required pairing at the capability declaration. Keep readRaw concrete so backends that correctly report false inherit one fail-loud implementation instead of duplicating rejection code.
Tianyi Cui
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