A transient ConfigDb error while loading a deployment's artifact emptied the
served address space. LoadArtifact caught the exception, logged "rebuild
becomes no-op" and returned zero bytes; those parsed to an EMPTY composition,
which the planner diffed against the live one as a PureRemove and the applier
faithfully executed — 16 nodes gone, while the log claimed nothing happened.
An artifact we could not obtain is not an empty configuration. Nothing
legitimate produces a zero-length blob (an operator who really deletes
everything still deploys a JSON document with empty arrays), so "no bytes" can
only mean "no answer". HandleRebuild now abandons the rebuild on one, leaving
both the materialised nodes and _lastApplied intact so the retry diffs against
what is actually being served. The loader's own log line is now true.
The two cases are logged differently: warn when there is a live address space
being protected, debug when nothing has been deployed to this node yet.
Covered by a RED-first actor test (verified failing: the load error tore down
eq-2's subtree), plus a positive control proving a READABLE artifact that
genuinely drops an equipment still removes it — the guard suppresses teardown
only when the read failed.
Found on the LocalDb Phase 1 follow-up live gate, which induced it by flapping
SQL; that gate's log is the production evidence for the seam.
Closes#485
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Joseph Doherty
4b0be1335e