fix(state): release archived Bot Chat title

hermes_state_titles.py

@@ -97,7 +97,7 @@ class SessionTitlesMixin:
                 return 0
             if title:
                 conflict = conn.execute(
-                    "SELECT id FROM sessions WHERE title = ? AND id != ?", (title, session_id),
+                    "SELECT id, archived, hidden FROM sessions WHERE title = ? AND id != ?", (title, session_id),
                 ).fetchone()
                 if conflict:
                     conflict_id = conflict["id"]
@@ -105,6 +105,16 @@ class SessionTitlesMixin:
                     # user, so transfer it onto the tip (uniqueness + lineage kept).
                     if self._is_compression_ancestor(conn, ancestor_id=conflict_id, descendant_id=session_id):
                         conn.execute("UPDATE sessions SET title = NULL WHERE id = ?", (conflict_id,))
+                    # A deliberately archived hidden Bot Chat is a retired registry
+                    # entry, not a live identity. Retire its name in the same title
+                    # transaction so a replacement can become the sole canonical row;
+                    # the old session remains archived and otherwise untouched.
+                    elif (title == self.CANONICAL_BOT_CHAT_TITLE and bool(conflict["archived"])
+                          and bool(conflict["hidden"])):
+                        conn.execute(
+                            "UPDATE sessions SET title = NULL, title_source = NULL WHERE id = ?",
+                            (conflict_id,),
+                        )
                     else:
                         raise ValueError(f"Title '{title}' is already in use by session {conflict_id}")
             # CAS on the values just read (``IS`` is NULL-safe): a concurrent write between

tests/hermes_state/test_canonical_title_guard.py

@@ -61,6 +61,23 @@ def test_visible_session_titled_bot_chat_stays_renameable(db):
     assert db.get_session("ordinary")["title"] == "renamed away"
 
 
+def test_deliberately_archived_canonical_chat_releases_name_for_replacement(db):
+    """Retiring a Bot Chat must not leave its registry name permanently locked."""
+    retired = _make_canonical(db, "retired")
+    assert db.set_session_archived(retired, True)
+
+    db.create_session("replacement", source="desktop")
+    assert db.set_session_title("replacement", SessionDB.CANONICAL_BOT_CHAT_TITLE)
+    assert db.set_session_hidden("replacement", True)
+
+    # The retired row stays archived, while exact-title resolution reaches the
+    # replacement that Bot Mode will subsequently open.
+    assert db.get_session(retired)["archived"]
+    assert db.get_session(retired)["title"] is None
+    row = db.get_session_by_title(SessionDB.CANONICAL_BOT_CHAT_TITLE)
+    assert row and row["id"] == "replacement"
+
+
 def test_auto_titler_still_cannot_touch_the_canonical_row(db):
     # Pre-existing provenance contract, re-pinned here: user-authority title
     # outranks derived/llm, so the turn-start auto-titler can never displace