diff --git a/apps/mobile/src/features/threads/git/GitBranchesSheet.test.tsx b/apps/mobile/src/features/threads/git/GitBranchesSheet.test.tsx
new file mode 100644
index 0000000000000..bc999e3e1cb4c
--- /dev/null
+++ b/apps/mobile/src/features/threads/git/GitBranchesSheet.test.tsx
@@ -0,0 +1,142 @@
+import { act, type ReactNode } from "react";
+import { createRoot } from "react-dom/client";
+import { expect, it, vi } from "vite-plus/test";
+
+type InputProps = {
+  accessibilityLabel: string;
+  value: string;
+  onChangeText: (value: string) => void;
+};
+type ActionProps = { label: string; disabled: boolean; onPress: () => void };
+const state = vi.hoisted(() => ({
+  refName: null as string | null,
+  branch: null as string | null,
+  inputs: new Map<string, InputProps>(),
+  actions: new Map<string, ActionProps>(),
+  worktrees: [] as Array<{ baseBranch: string; newBranch: string }>,
+}));
+
+vi.mock("@react-navigation/native", () => ({ useNavigation: () => ({ goBack() {} }) }));
+vi.mock("react-native", () => ({
+  Platform: { OS: "android" },
+  useWindowDimensions: () => ({ height: 800 }),
+  View: ({ children }: { children: ReactNode }) => children,
+  ScrollView: ({ children }: { children: ReactNode }) => children,
+  Pressable: () => null,
+}));
+vi.mock("react-native-safe-area-context", () => ({
+  useSafeAreaInsets: () => ({ bottom: 0 }),
+}));
+vi.mock("../../../components/ui/AndroidScreenHeader", () => ({ AndroidSheetHeader: () => null }));
+vi.mock("../../../components/ui/SheetHeader", () => ({ SheetHeader: () => null }));
+vi.mock("../../../components/ui/ScreenContent", () => ({
+  ScreenContent: ({ children }: { children: ReactNode }) => children,
+}));
+vi.mock("../../../native/StackHeader", () => ({ NativeStackScreenOptions: () => null }));
+vi.mock("../../../components/ui/AppText", () => ({
+  AppText: ({ children }: { children: ReactNode }) => children,
+  AppTextInput: (props: InputProps) => {
+    state.inputs.set(props.accessibilityLabel, props);
+    return null;
+  },
+}));
+vi.mock("../../../state/query", () => ({
+  useEnvironmentQuery: () => ({
+    data: state.refName === null ? undefined : { refName: state.refName },
+  }),
+}));
+vi.mock("../../../state/use-thread-selection", () => ({
+  useThreadSelection: () => ({
+    selectedThread: { environmentId: "environment", branch: state.branch },
+  }),
+}));
+vi.mock("../../../state/use-selected-thread-worktree", () => ({
+  useSelectedThreadWorktree: () => ({
+    selectedThreadCwd: "/repo",
+    selectedThreadWorktreePath: null,
+  }),
+}));
+vi.mock("../../../state/use-selected-thread-git-state", () => ({
+  useSelectedThreadGitState: () => ({
+    selectedThreadBranches: [],
+    selectedThreadBranchesLoading: false,
+    gitOperationLabel: null,
+  }),
+}));
+vi.mock("../../../state/use-selected-thread-git-actions", () => ({
+  useSelectedThreadGitActions: () => ({
+    canChangeThreadBranch: true,
+    onCreateSelectedThreadWorktree: async (input: { baseBranch: string; newBranch: string }) => {
+      state.worktrees.push(input);
+      return null;
+    },
+  }),
+}));
+vi.mock("../../../state/vcs", () => ({ vcsEnvironment: { status: () => null } }));
+vi.mock("./gitSheetComponents", () => ({
+  SheetActionButton: (props: ActionProps) => {
+    state.actions.set(props.label, props);
+    return null;
+  },
+}));
+
+import { GitBranchesSheet } from "./GitBranchesSheet";
+
+function setup(branch: string | null = null) {
+  (globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true;
+  state.refName = null;
+  state.branch = branch;
+  state.inputs.clear();
+  state.actions.clear();
+  state.worktrees = [];
+  const root = createRoot(document.createElement("div"));
+  const render = () =>
+    act(() => {
+      root.render(
+        <GitBranchesSheet
+          route={{ params: { environmentId: "environment", threadId: "thread" } }}
+        />,
+      );
+    });
+  render();
+  return {
+    render,
+    edit(label: string, value: string) {
+      act(() => state.inputs.get(label)!.onChangeText(value));
+    },
+    create() {
+      act(() => state.actions.get("Create worktree")!.onPress());
+    },
+    [Symbol.dispose]() {
+      act(() => root.unmount());
+    },
+  };
+}
+
+it.each([null, "stale-branch"])(
+  "uses the loaded checkout branch when thread metadata is %s",
+  (branch) => {
+    using screen = setup(branch);
+    screen.edit("Worktree branch name", "feature/new-worktree");
+    state.refName = "release/stable";
+    screen.render();
+    screen.create();
+    expect(state.worktrees).toEqual([
+      { baseBranch: "release/stable", newBranch: "feature/new-worktree" },
+    ]);
+  },
+);
+
+it.each(["custom-base", ""])("preserves an edited base %j when status arrives", (base) => {
+  using screen = setup();
+  screen.edit("Worktree base branch", base);
+  screen.edit("Worktree branch name", "feature/new-worktree");
+  state.refName = "release/stable";
+  screen.render();
+  expect(state.inputs.get("Worktree base branch")!.value).toBe(base);
+  expect(state.actions.get("Create worktree")!.disabled).toBe(base === "");
+  screen.create();
+  expect(state.worktrees).toEqual(
+    base === "" ? [] : [{ baseBranch: base, newBranch: "feature/new-worktree" }],
+  );
+});
diff --git a/apps/mobile/src/features/threads/git/GitBranchesSheet.tsx b/apps/mobile/src/features/threads/git/GitBranchesSheet.tsx
index dcaf96818bfe0..61c7a7ad6e4ab 100644
--- a/apps/mobile/src/features/threads/git/GitBranchesSheet.tsx
+++ b/apps/mobile/src/features/threads/git/GitBranchesSheet.tsx
@@ -49,9 +49,10 @@ export function GitBranchesSheet(_props: GitBranchesSheetProps) {
   const busy = gitState.gitOperationLabel !== null;
 
   const [newBranchName, setNewBranchName] = useState("");
-  const [worktreeBaseBranch, setWorktreeBaseBranch] = useState(
-    currentBranchLabel === "Detached HEAD" ? "main" : currentBranchLabel,
-  );
+  const [worktreeBaseBranchOverride, setWorktreeBaseBranchOverride] = useState<string | null>(null);
+  const worktreeBaseBranch =
+    worktreeBaseBranchOverride ??
+    (currentBranchLabel === "Detached HEAD" ? "main" : currentBranchLabel);
   const [worktreeBranchName, setWorktreeBranchName] = useState("");
 
   const disabledExistingBranchNames: Array<string> = [];
@@ -141,7 +142,7 @@ export function GitBranchesSheet(_props: GitBranchesSheetProps) {
             ) : null}
             <TextInput
               value={worktreeBaseBranch}
-              onChangeText={setWorktreeBaseBranch}
+              onChangeText={setWorktreeBaseBranchOverride}
               placeholder="main"
               accessibilityLabel="Worktree base branch"
               className="android:rounded-xl android:bg-sheet-solid ios:rounded-[18px]"
diff --git a/apps/mobile/vite.config.ts b/apps/mobile/vite.config.ts
index b64dc1c4e2a12..53f57f668a0ea 100644
--- a/apps/mobile/vite.config.ts
+++ b/apps/mobile/vite.config.ts
@@ -4,6 +4,7 @@ import { defineConfig, normalizePath } from "vite-plus";
 import "vite-plus/test/config";
 
 const reactTests = [
+  "src/features/threads/git/GitBranchesSheet.test.tsx",
   "src/features/threads/new-task-flow-provider.test.tsx",
   "src/features/workspace/workspace-tabs-state.test.ts",
   "src/state/use-thread-pr.demand.test.tsx",