diff --git a/README.md b/README.md
index 887dee1..1ef7b73 100644
--- a/README.md
+++ b/README.md
@@ -131,11 +131,11 @@ as sync targets and mount points — a mismatch is a broken path.
 # the share on HOST2 must have the exact same name.
 #
 # Same name on both servers:
-    /mnt/user/Movies          # HOST1 source of truth, HOST2 mirror
-    /mnt/user/Tv_Shows        # HOST1 source of truth, HOST2 mirror
-    /mnt/user/Music           # HOST1 source of truth, HOST2 mirror
-    /mnt/user/Anime_Shows     # HOST2 source of truth, HOST1 mirror
-    /mnt/user/Anime_Movies    # HOST2 source of truth, HOST1 mirror
+    /mnt/user/Movies          # both servers — arr_sync.sh keeps Radarr in union
+    /mnt/user/Tv_Shows        # both servers — arr_sync.sh keeps Sonarr in union
+    /mnt/user/Music           # both servers — arr_sync.sh keeps Lidarr in union
+    /mnt/user/Anime_Shows     # both servers — arr_sync.sh keeps Sonarr in union
+    /mnt/user/Anime_Movies    # both servers — arr_sync.sh keeps Radarr in union
 #
 # rsync.sh syncs /mnt/user/Movies on HOST1 → /mnt/user/Movies on HOST2.
 # If HOST2 has it at /mnt/user/Movies-Mirror → rsync aborts: path not found.
@@ -168,46 +168,61 @@ across separate shares per-user or per-application.
 
 ---
 
-### ── Never Two Arrs Against the Same Share Simultaneously ───────────────────
+### ── Both Arrs Manage All Shares — arr_sync.sh Is the Source of Truth ───────
 
 ```bash
 # ─────────────────────────────────────────────────────────────────────────────
-# This rule is absolute. No exceptions.
+# Both servers run Sonarr, Radarr, and Lidarr — all pointing at the same
+# share names. Either server can download anything to any share at any time.
 #
-# Correct: HOST1 Sonarr manages /mnt/user/Tv_Shows
-#          HOST2 Sonarr manages /mnt/user/Anime_Shows
-#          Different shares — no conflict
+# How it stays coherent:
+#   arr_sync.sh runs first (before rsync) — bidirectional library union.
+#   Both Sonarr instances know about every TV episode on either server.
+#   Both Radarr instances know about every movie on either server.
+#   Both Lidarr instances know about every album on either server.
 #
-# Correct: HOST1 Tdarr transcodes from /mnt/user/Anime_Shows
-#          HOST2 Sonarr downloads into /mnt/user/Anime_Shows
-#          But: they run in non-overlapping time windows
+# Then rsync spreads the files additively (no --delete).
+# Any file downloaded on HOST1 propagates to HOST2 on the next cycle.
+# Any file downloaded on HOST2 propagates to HOST1 on the next cycle.
 #
-# WRONG:   HOST1 Sonarr AND HOST2 Sonarr both managing /mnt/user/Tv_Shows
-#          Two arrs managing the same library = rename conflicts, double imports,
-#          deletion battles, corrupted databases.
+# HOST1 downloads Tv_Shows episode:
+#   → HOST1 Sonarr tracks it immediately
+#   → arr_sync.sh runs → HOST2 Sonarr now tracks it
+#   → daily rsync → file lands on HOST2
 #
-# This is why source of truth is split:
-    HOST1 owns:  Movies (Radarr), Tv_Shows (Sonarr), Music (Lidarr)
-    HOST2 owns:  Anime_Movies (Radarr), Anime_Shows (Sonarr)
+# HOST2 downloads the same show's next episode that same night:
+#   → HOST2 Sonarr tracks it immediately
+#   → arr_sync.sh runs → HOST1 Sonarr now tracks it
+#   → daily rsync → file lands on HOST1
 #
-# When HOST2 enters failover and starts HOST1's arr containers — those arrs
-# point at /mnt/user/Movies etc. HOST2's own arrs point at /mnt/user/Anime_*.
-# Different shares, no conflict. This is by design.
+# Both servers converge. Neither owns the share. The union is the truth.
 # ─────────────────────────────────────────────────────────────────────────────
 ```
 
 ---
 
-### ── Source of Truth ──────────────────────────────────────────────────────────
+### ── How arr_sync.sh Keeps the Union Stable ────────────────────────────────
 
 ```bash
 # ─────────────────────────────────────────────────────────────────────────────
-# Every share has exactly one server that owns it.
-# That server's arr manages it. That server pushes it to the other via daily sync.
-# The receiving server treats it as read-only.
+# arr_sync.sh runs as the fixed first step of intermediate_sync_maintenance.sh
+# (every 4 hours). It syncs all arr libraries bidirectionally before any rsync.
 #
-# Rule: never add content to a mirrored share on the non-owning server.
-# It will be overwritten on the next sync.
+# What it does:
+#   Reads each arr's full library via the local API
+#   SSHes to the remote, reads the remote arr library via its API
+#   Adds anything missing on either side — union, not overwrite
+#   Blocked items (blocklist) are excluded from sync
+#
+# What this means in practice:
+#   No share has an owner. No server is read-only.
+#   Either server can download content to any share at any time.
+#   arr_sync.sh guarantees both arrs agree on what exists before files move.
+#   rsync then spreads the files to make storage match what arrs already know.
+#
+# arr_cleanup.sh (daily) removes true orphans — files no arr tracks.
+# arr_cleanup uses the union model too: a file is only an orphan if
+# neither arr on either server has it indexed.
 # ─────────────────────────────────────────────────────────────────────────────
 ```