Unconditional list.extend() on repeated plugin install caused every
hook handler to be appended on each reinstall, leading to 3-4x duplicate
firings per event (PreToolUse, PostToolUse, Stop, etc.).
Fix: before appending each incoming handler, compute a fingerprint of
(matcher, frozenset-of-commands). Skip append if the fingerprint is
already present in the merged list. First-time installs are unaffected —
new handlers still land correctly.
Adds 7 unit tests covering: first install, double install, triple install,
different-matcher co-existence, different-command co-existence, existing
user hook preservation, and top-level key merge semantics.
Closes#566
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Molecule AI Triage Operator
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