docs: document SessionDB compat patch in README

README.md

@@ -112,3 +112,22 @@ it uses `fallback_peer`. If that's also unset → `user-default-*` (safe).
 - If the config file is missing, all resolution returns None → Honcho
   creates `user-default-*` as today.
 - No data loss risk. No changes to any file in the Hermes repo.
+
+## SessionDB compatibility patch
+
+The built-in `session_search` tool passes a `user_id` keyword argument to
+`SessionDB.search_messages()` and `SessionDB.list_sessions_rich()`, but
+the upstream backend methods do not accept it (they were removed in a
+later release — the tool code wasn't updated to match). This causes:
+
+```
+SessionDB.search_messages() got an unexpected keyword argument 'user_id'
+```
+
+The plugin applies a monkey-patch at load time that wraps both methods
+to accept (and silently drop) the `user_id` kwarg before calling the
+original backend. Same zero-fork pattern as the Honcho patch.
+
+The access-control filtering by user_id still happens in the tool code
+after results are returned — this patch only removes the redundant
+(and broke) passing of user_id to the DB layer.