Test: Multi-Chat in the Claude Code agent-host harness

[sandy081]

Refs: #323625

• anyOS @lszomoru
• anyOS @kycutler

Complexity: 4

Authors: @sandy081

Create Issue

---

Multi-Chat in Claude Code

A single Claude Code session can hold multiple independent chats (tabs): add new chats, fork
existing ones, run them concurrently, each with its own model, and have them all survive a
restart. Peer chats stay grouped under their parent session and never appear as separate
top-level sessions.

Set up

1. Agents window enabled.
2. Create and authenticate a Claude Code (Claude agent-host) session.

Scenario 1 — Add & switch chats

• Use Add Chat (Cmd/Ctrl+T, or the new-chat action in the tab bar) → a new chat tab
  appears under the same session, empty and ready for input; you can switch between tabs.

Scenario 2 — Independent, concurrent conversations

• Send a message in Chat 1, then a different one in Chat 2 → each streams/responds
  independently and responses land in the correct tab.
• A running turn in one chat does not block sending in the other (concurrent turns work).
• Change the model in Chat 2 to a different one than Chat 1 → it applies only to that
  chat; Chat 1 keeps its model; later responses in Chat 2 use the new model.

Scenario 3 — Fork a chat

• From a chat with some turns, use Fork (fork-into-new-chat at a turn) → a new chat opens
  pre-populated with the source chat's turns up to the fork point; continuing the fork does
  not affect the original.

Scenario 4 — Close / delete a chat

• Close a non-default (added/peer) chat tab (Delete on the tab, or the close action) →
  the peer chat is removed; other chats and the session remain intact.
• The default/main chat cannot be closed on its own (it lives with the session).

Scenario 5 — Restore after restart

• Create a session with 2-3 chats (mix of added + forked), send messages in each, set
  different models, then reload/restart → the session reopens with all chats restored as
  tabs; each chat's history, title, and model are preserved; no chat is lost, duplicated, or
  promoted to a top-level session.

Scenario 6 — Backward compatibility

• Open a pre-existing Claude session created before this feature → it restores normally and
  you can add new chats to it.

[kycutler]

Wasn't able to test scenario 6.

A few small bugs, but overall it works well!