The block-level body merge keyed each block by its full attribute set,
including the per-block UniqueID the editor stamps on every heading/paragraph.
A body arriving from git is parsed from clean markdown and carries no block
ids, so a live block (id present) never matched the same block coming from git
(no id). The three-way merge's LCS could not anchor on it, and an incoming
block with no matching anchor — content inserted at the TOP of the page — was
re-added on every push/pull cycle: a non-convergent, unbounded duplication loop.
Exclude the volatile 'id' attribute from the block comparison key
(serializeXmlNode) so blocks compare by content across the git round-trip.
The merge keeps the live block INSTANCE (and its id, and any in-flight edit)
for an anchor — picks are by index, not key — so identity is preserved while
reconciliation becomes idempotent. Mirrors canonicalize.ts, which already
strips the regenerated block id from the round-trip idempotency comparison.
Adds a RED-before-fix repro modelling the live-id vs git-no-id asymmetry and
asserting no block growth across cycles.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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