diff --git a/HANDOFF.md b/HANDOFF.md
index 1db4401..aa786d8 100644
--- a/HANDOFF.md
+++ b/HANDOFF.md
@@ -8,8 +8,16 @@
 > ContentObserver in `MainActivity.kt` receives the changed URI, queries
 > that one row, drops a one-line payload (`.ms_recent.N`: `A|id|path|size`
 > or `D|id`), wakes Rust via zero-arg JNI; Rust applies it directly.
-> FS walk = startup baseline + 5-min reconciliation + mtime-diff
-> incremental; a walk that ERRORS is never applied (see scan.rs docs).
+> FS walk = startup baseline + 5-min reconciliation. On Android the
+> mtime-diff (`dir_sig`) machinery is DISABLED — it cost a 10k-entry
+> readdir per second and the MediaStore payloads already carry the
+> exact change signal; a no-payload OS event falls back to a 30s-
+> throttled full rescan. A `RESCANNING` gate parks payloads while a
+> full walk is in flight (mid-walk deletes must apply AFTER the walk's
+> apply to win over its stale snapshot). Per-file stat errors in a
+> walk are skipped (a deleted-mid-walk file must not kill deletion
+> detection); only readdir/root errors fail the walk, and a walk that
+> ERRORS is never applied (see scan.rs docs).
 >
 > **Emulator `pad_aosp` gotcha:** the image ships with
 > `debug.hwui.drawing_enabled=0` — every window renders BLACK (HWUI