fix(desktop): add missing PATCH /api/sessions/{id} so rename works (#36249)

The desktop rename dialog sent PATCH /api/sessions/{id}, but the backend
only defined GET and DELETE for that path — FastAPI returned 405 Method
Not Allowed, surfaced to the user as "Rename failed". Add the PATCH route
backed by SessionDB.set_session_title (handles sanitization, uniqueness,
and clearing the title when empty).

Also fix a misleading notification: any 405 was summarized as an unrelated
"does not support that audio endpoint" message. Make it a generic 405 hint.

apps/desktop/src/store/notifications.ts

@@ -68,7 +68,8 @@ const ERROR_SUMMARIES: { test: (msg: string) => boolean; summarize: (msg: string
   },
   {
     test: msg => /method not allowed/i.test(msg),
-    summarize: () => 'The desktop backend does not support that audio endpoint yet. Restart Hermes Desktop.'
+    summarize: () =>
+      'The desktop backend rejected that request (405 Method Not Allowed). Try restarting Hermes Desktop.'
   },
   {
     test: msg => /microphone permission/i.test(msg),

hermes_cli/web_server.py

@@ -3657,6 +3657,31 @@ async def delete_session_endpoint(session_id: str):
         db.close()
 
 
+class SessionRename(BaseModel):
+    title: Optional[str] = None
+
+
+@app.patch("/api/sessions/{session_id}")
+async def rename_session_endpoint(session_id: str, body: SessionRename):
+    """Rename a session (or clear its title when ``title`` is empty/null)."""
+    from hermes_state import SessionDB
+    db = SessionDB()
+    try:
+        sid = db.resolve_session_id(session_id)
+        if not sid:
+            raise HTTPException(status_code=404, detail="Session not found")
+        try:
+            updated = db.set_session_title(sid, body.title or "")
+        except ValueError as e:
+            # Title too long, invalid characters, or already in use.
+            raise HTTPException(status_code=400, detail=str(e))
+        if not updated:
+            raise HTTPException(status_code=404, detail="Session not found")
+        return {"ok": True, "title": db.get_session_title(sid) or ""}
+    finally:
+        db.close()
+
+
 # ---------------------------------------------------------------------------
 # Log viewer endpoint
 # ---------------------------------------------------------------------------

tests/hermes_cli/test_web_server.py

@@ -205,6 +205,51 @@ class TestWebServerEndpoints:
         assert captured["list"] == 3
         assert captured["count"] == 3
 
+    def test_rename_session_updates_title(self):
+        """PATCH /api/sessions/{id} renames a session (regression: the route
+        was missing entirely, so the desktop rename dialog got a 405)."""
+        from hermes_state import SessionDB
+
+        db = SessionDB()
+        try:
+            db.create_session(session_id="rename-me", source="cli")
+        finally:
+            db.close()
+
+        resp = self.client.patch("/api/sessions/rename-me", json={"title": "My Chat"})
+        assert resp.status_code == 200
+        assert resp.json() == {"ok": True, "title": "My Chat"}
+
+        db = SessionDB()
+        try:
+            assert db.get_session_title("rename-me") == "My Chat"
+        finally:
+            db.close()
+
+    def test_rename_session_clears_title_when_empty(self):
+        from hermes_state import SessionDB
+
+        db = SessionDB()
+        try:
+            db.create_session(session_id="clear-me", source="cli")
+            db.set_session_title("clear-me", "Has A Title")
+        finally:
+            db.close()
+
+        resp = self.client.patch("/api/sessions/clear-me", json={"title": ""})
+        assert resp.status_code == 200
+        assert resp.json() == {"ok": True, "title": ""}
+
+        db = SessionDB()
+        try:
+            assert db.get_session_title("clear-me") is None
+        finally:
+            db.close()
+
+    def test_rename_session_not_found(self):
+        resp = self.client.patch("/api/sessions/does-not-exist", json={"title": "x"})
+        assert resp.status_code == 404
+
     def test_audio_transcription_endpoint(self, monkeypatch):
         import tools.transcription_tools as transcription_tools