studio/frontend: clear stale thread/compare search after sidebar nav

[danielhanchen]

Summary

• Three sidebar navigations (delete active chat, New Chat, Unsloth home logo) call navigate({to: "/chat", search: {new: nonce}}). TanStack Router merges search params by default, so the prior ?thread=<id> (or ?compare=<id>) survives.
• The recovery useEffect in features/chat/chat-page.tsx:557-585 only fires when search.thread changes, so the in-tab URL stays stale until a hard reload.
• Pass thread: undefined, compare: undefined alongside new to actually remove the prior keys.

Repro

python scripts/r6_repro_active_delete_url.py
# URL before: http://127.0.0.1:8890/chat?thread=AAA
#   +0.5s URL: http://127.0.0.1:8890/chat?thread=AAA
#   +5.0s URL: http://127.0.0.1:8890/chat?thread=AAA
# final URL:  http://127.0.0.1:8890/chat?thread=AAA   <- stale
# active_in_sidebar: False                            <- row gone
# (hard reload then redirects to /chat?new=<nonce>)

Test plan

• tsc clean
• Probe scripts/r6_sidebar_delete_chat_probe.py expect delete_active_thread_navigates_away: True after patched build
• Manual: delete active chat then URL clears to ?new
• Manual: from /chat?thread=X click New Chat then URL becomes ?new without leftover thread
• Manual: from /chat?thread=X click Unsloth logo then URL becomes ?new

[gemini-code-assist]

Code Review

This pull request updates the navigation logic in the AppSidebar component to explicitly clear thread and compare search parameters, preventing TanStack Router from merging stale values into the URL. The reviewer suggests using the functional form of the search property in TanStack Router as a more idiomatic and robust way to reset parameters. Furthermore, for the thread deletion handler, it is recommended to explicitly clear the active thread ID and close the mobile sidebar to maintain state consistency.

[gemini-code-assist]

To ensure consistency with other navigation actions in the sidebar and to avoid stale state in the store, you should clear the active thread ID and close the mobile sidebar (if open) when navigating after a deletion.

Additionally, using the functional form of search in TanStack Router is a more robust way to reset the URL parameters. It prevents the router from merging old thread or compare IDs into the new URL, ensuring the address bar is updated immediately without relying on the recovery logic in ChatPage (which only handles stale IDs on mount).

      setActiveThreadId(null);
      void navigate({
        to: "/chat",
        search: () => ({ new: view.newThreadNonce }),
      });
      closeMobileIfOpen();

References

1. Prefer explicit cleanup of resource bindings or references within deletion handlers over background 'sweeper' effects that rely on list state to detect and clean up stale data.

[gemini-code-assist]

Using the functional form of search is a more idiomatic and robust way to reset the URL parameters in TanStack Router, as it explicitly defines the new search state rather than merging with the existing one.

Suggested change

	void navigate({
	to: "/chat",
	search: { new: createNavigationNonce() },
	search: { new: createNavigationNonce(), thread: undefined, compare: undefined },
	});
	void navigate({
	to: "/chat",
	search: () => ({ new: createNavigationNonce() }),
	});

[gemini-code-assist]

Using the functional form of search is a more idiomatic and robust way to reset the URL parameters in TanStack Router, as it explicitly defines the new search state rather than merging with the existing one.

Suggested change

	navigate({
	to: "/chat",
	search: { new: createNavigationNonce(), thread: undefined, compare: undefined },
	});
	void navigate({
	to: "/chat",
	search: () => ({ new: createNavigationNonce() }),
	});