fix(state): renaming a bot's canonical Bot Chat is refused — the title IS the identity (#92473)

Bot Mode resolves the forever-chat by exact-title lookup on
(profile, 'Bot Chat'); no session-id pointer exists. A user rename
therefore orphaned the whole conversation: resolution missed, the next
click minted an empty replacement, and UNIQUE(title) then blocked ever
renaming back. Refuse the rename at SessionDB._set_session_title — the
single write path every surface funnels through (gateway session.title,
/title, CLI rename, REST). Hidden discriminates the registry row, so a
normal visible session a user happens to call 'Bot Chat' stays freely
renameable; re-asserting the same canonical title stays a no-op.

hermes_state.py

@@ -9096,6 +9096,13 @@ class SessionDB(SessionSearchMixin, SessionSchemaMixin, SessionPortabilityMixin)
         TITLE_SOURCE_USER: 2,
     }
 
+    # Bot Mode's forever-chat registry: the session titled exactly this, on a
+    # bot's profile, IS the bot's canonical chat — resolved by exact-title
+    # lookup on every open (no session-id pointer exists). The title is the
+    # identity, which is why _set_session_title refuses user renames of a
+    # hidden row holding it (#92473).
+    CANONICAL_BOT_CHAT_TITLE = "Bot Chat"
+
     @classmethod
     def _title_rank(cls, source: Optional[str]) -> int:
         """Rank a stored title_source. NULL means a pre-provenance row.
@@ -9222,11 +9229,31 @@ class SessionDB(SessionSearchMixin, SessionSchemaMixin, SessionPortabilityMixin)
 
         def _do(conn):
             current = conn.execute(
-                "SELECT title, title_source FROM sessions WHERE id = ?",
+                "SELECT title, title_source, hidden FROM sessions WHERE id = ?",
                 (session_id,),
             ).fetchone()
             if current is None:
                 return 0
+            # The canonical Bot Chat's NAME is its identity: Bot Mode resolves
+            # the forever-chat by exact-title lookup on every open, so renaming
+            # the row orphans the entire conversation — the next click mints an
+            # empty replacement and UNIQUE(title) then blocks ever renaming
+            # back (#92473). Refuse the rename at the single write path every
+            # surface funnels through (gateway session.title, /title, CLI
+            # rename, REST). Hidden is the discriminator: canonical chats are
+            # born hidden; an ordinary visible session a user happens to call
+            # "Bot Chat" stays freely renameable.
+            if (
+                is_user
+                and (current["title"] or "") == self.CANONICAL_BOT_CHAT_TITLE
+                and bool(current["hidden"])
+                and title != self.CANONICAL_BOT_CHAT_TITLE
+            ):
+                raise ValueError(
+                    "This is the bot's canonical Bot Chat — its name is its "
+                    "identity, and renaming it would orphan the conversation. "
+                    "To start fresh, create a new bot instead."
+                )
             if not is_user and current["title"] is not None:
                 if self._title_rank(current["title_source"]) >= new_rank:
                     return 0

tests/hermes_state/test_canonical_title_guard.py

@@ -0,0 +1,71 @@
+"""The canonical Bot Chat's title is its identity — renames must be refused.
+
+Bot Mode resolves a bot's forever-chat by exact-title lookup on
+(profile, "Bot Chat") every time it opens; there is no session-id pointer.
+A user rename therefore orphans the whole conversation: resolution misses,
+the next click mints an empty replacement, and UNIQUE(title) then blocks
+renaming the original back (#92473).
+
+The guard lives in SessionDB._set_session_title — the single write path
+every rename surface funnels through (gateway session.title RPC, /title,
+CLI rename, REST) — and keys on hidden + exact canonical title so ordinary
+sessions a user happens to call "Bot Chat" stay freely renameable.
+"""
+import pytest
+
+from hermes_state import SessionDB
+
+
+@pytest.fixture
+def db(tmp_path):
+    return SessionDB(tmp_path / "state.db")
+
+
+def _make_canonical(db, session_id="forever"):
+    db.create_session(session_id, source="desktop")
+    assert db.set_session_title(session_id, SessionDB.CANONICAL_BOT_CHAT_TITLE)
+    assert db.set_session_hidden(session_id, True)
+    return session_id
+
+
+def test_user_rename_of_canonical_bot_chat_is_refused(db):
+    sid = _make_canonical(db)
+    with pytest.raises(ValueError, match="canonical Bot Chat"):
+        db.set_session_title(sid, "My cool chat")
+    # Identity intact: exact-title lookup still finds the forever chat.
+    row = db.get_session_by_title(SessionDB.CANONICAL_BOT_CHAT_TITLE)
+    assert row and row["id"] == sid
+
+
+def test_clearing_the_canonical_title_is_refused(db):
+    sid = _make_canonical(db)
+    with pytest.raises(ValueError, match="canonical Bot Chat"):
+        db.set_session_title(sid, "")
+    row = db.get_session_by_title(SessionDB.CANONICAL_BOT_CHAT_TITLE)
+    assert row and row["id"] == sid
+
+
+def test_rewriting_the_same_canonical_title_is_a_noop_not_an_error(db):
+    # The plugin's eager session.title write re-asserts the canonical title
+    # on creation paths; that must never start failing.
+    sid = _make_canonical(db)
+    assert db.set_session_title(sid, SessionDB.CANONICAL_BOT_CHAT_TITLE)
+
+
+def test_visible_session_titled_bot_chat_stays_renameable(db):
+    # hidden discriminates the registry row: a normal visible session the
+    # user happened to name "Bot Chat" is not canonical and renames freely.
+    db.create_session("ordinary", source="cli")
+    assert db.set_session_title("ordinary", SessionDB.CANONICAL_BOT_CHAT_TITLE)
+    assert db.set_session_title("ordinary", "renamed away")
+    assert db.get_session("ordinary")["title"] == "renamed away"
+
+
+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
+    # the registry name.
+    sid = _make_canonical(db)
+    assert not db.set_auto_title(sid, "Chat about groceries", source=SessionDB.TITLE_SOURCE_LLM)
+    row = db.get_session_by_title(SessionDB.CANONICAL_BOT_CHAT_TITLE)
+    assert row and row["id"] == sid