Reported from a real run: after re-scoping a repo (5807->3710 nodes), the
228-community re-cluster kept run-1's 300 saved labels, so cids now covering a
different community wore the wrong (LLM) names — silently. cluster-only reused
.graphify_labels.json wholesale, and the overlap-based cid remap grabs a prior
cid on any overlap, inheriting a stale name.
Fix: write a per-community membership signature (sha256 of sorted member ids)
beside the labels. On reuse, keep a saved label only when the community's
signature is unchanged; a changed community is renamed by its deterministic
hub (correct-by-construction) with a warning to run `graphify label` for fresh
LLM names. For label files predating the signature, fall back to a community-
count check (a differing count means a different clustering -> don't trust cid
labels). Unchanged graphs reuse labels silently — no false warnings.
Verified: stale legacy labels (42) on a 12-community graph -> warned + hub-
renamed all + sig written; rerun on the unchanged graph -> silent reuse, labels
stable. Unit tests for the signature (deterministic, order-independent, changes
on membership change). Full suite 2771.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Community labels defaulted to "Community N" whenever no LLM backend was configured,
making the report + suggested questions unreadable ("why does log_action connect
Community 70 to Community 129?"). Add `label_communities_by_hub`: name each community
after its highest-degree member — the structural hub — so the report reads "log_action"
/ "auth" with zero LLM cost. Ties break by node id for run-to-run stability; a community
with no members in the graph keeps the "Community N" placeholder.
Wired as the default base at both label-building sites — the label/standalone path in
__main__ and the watch/detect rebuild in watch.py. A configured LLM naming pass still
runs and overrides these with richer names; its no-backend placeholder fallback is
guarded so it can't clobber the hub labels.
