Since BUG-989 a new chat is saved on its first send, and that create already carries the session's model. selectSessionModel still PATCHed the session right away; with no row yet the route answered 404 and the composer showed 「云端同步失败」 although the local choice had taken effect. The selection now returns before any PATCH for an unsaved empty consultation (same predicate as the send path). Saved chats sync as before. Full suite 4988 / fail 24, identical to 11333460; build keeps / Static. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_017eEAG8HD3mm8gsKXgk8uU8