A live, auto-sync-maintained index does not converge to a clean full
rebuild of the identical tree. On codegraph's own repo, 4.3% of distinct
edges are wrong in both directions (751 missing, 476 stale), dominated by
`calls` — the edges flow queries traverse and that feed the RWR mass
explore ranks files by.
Raw edge rows differ by only +0.7%, because the divergence is
bidirectional and nets out; any drift check must compare edge SETS.
Rebuild-vs-rebuild is 0, so the indexer is deterministic and this is not
noise. Node sets are identical and every integrity check is 0 on both
indexes, so this is stale cross-file resolution, not accumulated residue.
`diff-index-drift.mjs` is read-only and takes two index paths — rebuilding
is the caller's job, so the tool can never clobber the artifact it is
measuring. It also refuses a missing path, since node:sqlite creates an
empty database rather than failing and an empty schema reads exactly like
a stale pre-migration index.
Diagnostic captures from the originating incident are deliberately NOT
committed: they contain verbatim source from a private repo.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
