fix(app): select current branch for new workspaces

Closes #541

nix/package.nix

@@ -42,7 +42,7 @@ buildNpmPackage rec {
 
   # To update: run `nix build` with lib.fakeHash, copy the `got:` hash.
   # CI auto-updates this when package-lock.json changes (see .github/workflows/).
-  npmDepsHash = "sha256-O5AxXbwGJO52gvmVTzJqgy7nb2dxoVAaikBni3Gtu/s=";
+  npmDepsHash = "sha256-0Izp63gVeBO9Efo4Uf8/EB3TkQ9FXJ4Td2Fe5UHm9eE=";
 
   # Prevent onnxruntime-node's install script from running during automatic
   # npm rebuild (it tries to download from api.nuget.org, which fails in the sandbox).

packages/app/src/components/git-diff-pane.tsx

@@ -584,7 +584,9 @@ const DiffFileHeader = memo(function DiffFileHeader({
         onPress={toggleExpanded}
       >
         <View style={styles.fileHeaderLeft}>
-          <Text style={styles.fileName}>{file.path.split("/").pop()}</Text>
+          <Text style={styles.fileName} numberOfLines={1}>
+            {file.path.split("/").pop()}
+          </Text>
           <Text style={styles.fileDir} numberOfLines={1}>
             {file.path.includes("/") ? ` ${file.path.slice(0, file.path.lastIndexOf("/"))}` : ""}
           </Text>
@@ -2504,11 +2506,11 @@ const styles = StyleSheet.create((theme) => ({
   fileHeader: {
     flexDirection: "row",
     alignItems: "center",
-    justifyContent: "space-between",
     paddingLeft: theme.spacing[3],
     paddingRight: theme.spacing[2],
     paddingVertical: theme.spacing[2],
     gap: theme.spacing[1],
+    minWidth: 0,
     zIndex: 2,
     elevation: 2,
   },
@@ -2532,13 +2534,15 @@ const styles = StyleSheet.create((theme) => ({
     fontSize: theme.fontSize.sm,
     fontWeight: theme.fontWeight.normal,
     color: theme.colors.foreground,
-    flexShrink: 0,
+    flexShrink: 1,
+    minWidth: 0,
   },
   fileDir: {
     fontSize: theme.fontSize.sm,
     fontWeight: theme.fontWeight.normal,
     color: theme.colors.foregroundMuted,
     flex: 1,
+    minWidth: 0,
   },
   newBadge: {
     backgroundColor: "rgba(46, 160, 67, 0.2)",

packages/app/src/screens/new-workspace-screen.test.tsx

@@ -97,7 +97,11 @@ const {
 
   const hoistedMockClient = {
     isConnected: true,
-    getCheckoutStatus: vi.fn(async () => ({ currentBranch: "main" })),
+    getCheckoutStatus: vi.fn(
+      async (): Promise<{ currentBranch: string | null }> => ({
+        currentBranch: "main",
+      }),
+    ),
     getBranchSuggestions: vi.fn(async () => ({ branches: ["main", "dev", "feat/x"] })),
     searchGitHub: vi.fn(async () => ({
       items: [hoistedPrItem, hoistedPrItemB],
@@ -672,7 +676,7 @@ describe("NewWorkspaceScreen picker payload", () => {
     });
   });
 
-  it("sends no new fields when nothing is selected (default)", async () => {
+  it("uses the loaded current branch as the selected branch", async () => {
     renderScreen();
     await flush();
 
@@ -684,12 +688,24 @@ describe("NewWorkspaceScreen picker payload", () => {
     expect(call).toMatchObject({
       cwd: "/repo",
       worktreeSlug: "gentle-slug",
+      action: "branch-off",
+      refName: "main",
     });
-    expect(call).not.toHaveProperty("refName");
-    expect(call).not.toHaveProperty("action");
     expect(call).not.toHaveProperty("githubPrNumber");
   });
 
+  it("requires a branch selection when the current branch is unavailable", async () => {
+    mockClient.getCheckoutStatus.mockResolvedValueOnce({ currentBranch: null });
+    renderScreen();
+    await flush();
+
+    click(await findByTestId("test-composer-submit"));
+    await flush();
+
+    expect(mockClient.createPaseoWorktree).not.toHaveBeenCalled();
+    expect(document.body.textContent).toContain("Choose a branch to start from");
+  });
+
   it("opens the new workspace draft tab as soon as the worktree is ready", async () => {
     initialDraftState.text = "please review this change";
     renderScreen();

packages/app/src/screens/new-workspace-screen.tsx

@@ -194,6 +194,15 @@ function pickerItemTriggerLabel(item: PickerItem): string {
   return item.kind === "branch" ? item.name : formatPrLabel(item.item);
 }
 
+function resolveSelectedPickerItem(input: {
+  pickerSelection: PickerSelection | null;
+  currentBranch: string | null | undefined;
+}): PickerItem | null {
+  if (input.pickerSelection) return input.pickerSelection.item;
+  const currentBranch = input.currentBranch?.trim();
+  return currentBranch ? { kind: "branch", name: currentBranch } : null;
+}
+
 function syncPickerPrAttachment(input: {
   attachments: ComposerAttachment[];
   previousPickerPrNumber: number | null;
@@ -436,7 +445,6 @@ export function NewWorkspaceScreen({
 
   const displayName = displayNameProp?.trim() ?? "";
   const workspace = createdWorkspace;
-  const selectedItem = pickerSelection?.item ?? null;
   const isPending = pendingAction !== null;
   const client = useHostRuntimeClient(serverId);
   const isConnected = useHostRuntimeIsConnected(serverId);
@@ -476,7 +484,10 @@ export function NewWorkspaceScreen({
     refetchOnWindowFocus: false,
   });
 
-  const currentBranch = checkoutStatusQuery.data?.currentBranch ?? null;
+  const selectedItem = resolveSelectedPickerItem({
+    pickerSelection,
+    currentBranch: checkoutStatusQuery.data?.currentBranch,
+  });
 
   const branchSuggestionsQuery = useQuery({
     queryKey: ["branch-suggestions", serverId, sourceDirectory, debouncedPickerSearchQuery],
@@ -527,8 +538,8 @@ export function NewWorkspaceScreen({
 
   const triggerLabel = useMemo(() => {
     if (selectedItem) return pickerItemTriggerLabel(selectedItem);
-    return currentBranch ?? "main";
-  }, [currentBranch, selectedItem]);
+    return "Select branch";
+  }, [selectedItem]);
 
   const selectedOptionId = useMemo(() => {
     if (!selectedItem) return "";
@@ -588,6 +599,9 @@ export function NewWorkspaceScreen({
   const buildCreateWorktreeInput = useCallback(
     (input: { cwd: string; attachments: AgentAttachment[] }) => {
       const checkoutRequest = pickerItemToCheckoutRequest(selectedItem);
+      if (!checkoutRequest) {
+        throw new Error("Choose a branch to start from");
+      }
 
       return {
         cwd: input.cwd,