claude.ai: merging Chat and Cowork into one surface (7-8 Oct 2026) broke working Cowork sessions

Concerns the claude.ai web app, not the CLI. CLI-only template fields: not applicable. Max plan, model claude-opus-5-5, sessions inside a Project.

Until 7 Oct 2026 I used Cowork exclusively and it worked. Chat and Cowork were then merged into one surface with no option to keep the old Cowork behaviour. Since the merge, the same sessions, skills and connectors fail in ways they did not before. Evidence from one session on 9 Oct 2026 (conversation [id removed], ~00:30 to 05:20 ET):

1. Blank assistant turns. A user message got an empty assistant reply and had to be sent again. Another message appears twice in the transcript for the same reason.
2. Session rename silently fails. The session kept the default title "Session" despite a rename call at turn one. Before the merge the same call (PUT /v1/code/sessions/{id}) renamed the visible title; now the visible name lives on the chat_conversations record, project sessions are missing from GET /v1/code/sessions (#100379), and the PUT returns 200 while nothing visible changes.
3. Auto mode classifier now refuses owner-approved actions with Cowork-labelled reasons ("Cowork Run Routine Now", "Cowork Folder Access") inside the merged surface, including running the account owner's own scheduled task on demand and requesting folder access on the owner's own Mac. Filed in detail as #100730.
4. Tool result cards misrender. create_pull_request shows an editable PR card that later reports a false "failed to create pull request" (#100747).
5. Cross-chat reading is now walled by Project. A conversation the user links directly cannot be opened from a chat in another Project (#100749).

Expected: the merged surface behaves as Cowork did: one session id, one visible title, listed everywhere, no empty replies, and no new classifier categories applied to work the owner already approved.

Ask: treat these as regressions from the merge, and until fixed, give users a way to run the pre-merge Cowork behaviour.

Supersedes my comment on #98702, which predates the merge.