diff --git a/apps/web/src/hooks/useThreadActions.permissions.test.ts b/apps/web/src/hooks/useThreadActions.permissions.test.ts
index 58bc33cd0d64..649ec0c6bac1 100644
--- a/apps/web/src/hooks/useThreadActions.permissions.test.ts
+++ b/apps/web/src/hooks/useThreadActions.permissions.test.ts
@@ -55,7 +55,11 @@ vi.mock("react", () => ({
   useRef: (current: unknown) => ({ current }),
 }));
 vi.mock("@tanstack/react-router", () => ({
-  useRouter: () => ({ state: { location: { href: "/" }, matches: [] }, navigate: async () => {} }),
+  useRouter: () => ({
+    state: { location: { href: "/" }, matches: [] },
+    history: { subscribe: () => () => {} },
+    navigate: async () => {},
+  }),
 }));
 vi.mock("../state/session", () => ({
   environmentSession: { sessionStateAtom: "session" },
diff --git a/apps/web/src/hooks/useThreadActions.ts b/apps/web/src/hooks/useThreadActions.ts
index a057f0852732..cc9c27770886 100644
--- a/apps/web/src/hooks/useThreadActions.ts
+++ b/apps/web/src/hooks/useThreadActions.ts
@@ -588,10 +588,16 @@ export function useThreadActions() {
       sortOrder: sidebarThreadSortOrder,
       now: new Date().toISOString(),
     });
+    let navigatedDuringDelete = false;
+    // The missing-thread redirect and the index draft replace this entry; any other history
+    // action while the delete is pending is the user's own choice, which must win.
+    const stopWatchingHistory = router.history.subscribe(({ action }) => {
+      if (action.type !== "REPLACE") navigatedDuringDelete = true;
+    });
     const deleteResult = await deleteThreadMutation({
       environmentId: threadRef.environmentId,
       input: { threadId: threadRef.threadId },
-    });
+    }).finally(stopWatchingHistory);
     if (deleteResult._tag === "Failure") {
       return deleteResult;
     }
@@ -615,7 +621,7 @@ export function useThreadActions() {
     clearTerminalUiState(threadRef);
     clearDeletedThreadPanelState(threadRef);
 
-    if (shouldNavigateToFallback) {
+    if (shouldNavigateToFallback && !navigatedDuringDelete) {
       const fallbackThread = fallbackThreadId
         ? readThreadShell(scopeThreadRef(threadRef.environmentId, fallbackThreadId))
         : null;
diff --git a/apps/web/src/hooks/useThreadActions.undo.test.ts b/apps/web/src/hooks/useThreadActions.undo.test.ts
index a2ce4229d9b0..98f69e9de5a0 100644
--- a/apps/web/src/hooks/useThreadActions.undo.test.ts
+++ b/apps/web/src/hooks/useThreadActions.undo.test.ts
@@ -19,10 +19,20 @@ const commands = vi.hoisted(() => ({
   snooze: vi.fn(),
   unsnooze: vi.fn(),
 }));
-const router = vi.hoisted(() => ({
-  navigate: vi.fn(async () => {}),
-  state: { location: { href: "/" }, matches: [{ params: {} as Record<string, string> }] },
-}));
+const router = vi.hoisted(() => {
+  const listeners = new Set<(event: { action: { type: string } }) => void>();
+  return {
+    navigate: vi.fn(async () => {}),
+    state: { location: { href: "/" }, matches: [{ params: {} as Record<string, string> }] },
+    history: {
+      listeners,
+      subscribe: (listener: (event: { action: { type: string } }) => void) => {
+        listeners.add(listener);
+        return () => listeners.delete(listener);
+      },
+    },
+  };
+});
 vi.mock("../state/use-atom-query-runner", () => ({ useAtomQueryRunner: () => vi.fn() }));
 vi.mock("../state/session", async (original) => ({
   ...(await original<typeof import("../state/session")>()),
@@ -251,6 +261,25 @@ describe("archive navigation", () => {
   });
 });
 
+describe("delete navigation", () => {
+  it.each([
+    { type: "REPLACE", by: "the app's missing-thread redirect", fallsBack: true },
+    { type: "PUSH", by: "the user opening another thread", fallsBack: false },
+  ])("falls back: $fallsBack after $by while deleting", async ({ type, fallsBack }) => {
+    router.state.matches[0]!.params = {
+      environmentId: target.environmentId,
+      threadId: target.threadId,
+    };
+    commands.delete.mockImplementation(async () => {
+      for (const listener of router.history.listeners) listener({ action: { type } });
+      return { _tag: "Success", value: undefined };
+    });
+    expect((await useThreadActions().deleteThread(target))._tag).toBe("Success");
+    expect(router.navigate).toHaveBeenCalledTimes(fallsBack ? 1 : 0);
+    expect(router.history.listeners.size).toBe(0);
+  });
+});
+
 describe("settle and snooze Undo", () => {
   it("un-settles from the notice and expires the Undo after a manual un-settle", async () => {
     const add = vi.spyOn(toastManager, "add").mockReturnValue("toast");