truncated-hash-threshold-is-16-chars

IN premise

A stored `source_hash` of exactly 16 characters that is a prefix of the current full SHA-256 hash is classified as `truncated_hash` (legacy format), not `content_changed`.

Summary

When the system finds a 16-character hash in storage that matches the beginning of the current full-length hash, it recognizes this as an old-format shortened hash rather than treating it as a content change. This prevents false "content changed" signals when migrating from the legacy 16-character hash format to full SHA-256 hashes.

Details

Source

entries/2026/05/05/reasons_lib-check_stale.md