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EquipmentRuntime::read_sync establishes THE pattern for reading mutable engine state from gRPC/binding threads (Phase 0 item 6): post the read onto the io thread (the model's single owner), wait on a future with a deadline, nullopt => UNAVAILABLE at the RPC edge. Always truthful, no cache to invalidate; milliseconds are irrelevant at SECS rates. GetVariables: name resolution against the service snapshot (empty query = all; unknown name => INVALID_ARGUMENT naming the offender), values read via read_sync, converted by the new from_item reverse conversion (single-element numeric arrays => scalars, multi-element => List; Boolean/Binary/text per format; C2-as-integer and U8>2^63 wrap documented as TODOs). Tests run the engine in run_async — the daemon's PRODUCTION threading mode, previously untested — and round-trip through both conversions: SetVariables (declared-format write) then GetVariables (read) over a real in-process channel. Daemon suite 41 -> 61 assertions. daemon_interop.py gains a live GetVariables round-trip check vs the running daemon (verified green). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>