diff --git a/apps/web/src/components/BranchToolbar.browser.tsx b/apps/web/src/components/BranchToolbar.browser.tsx
new file mode 100644
index 0000000000..65d2f0b955
--- /dev/null
+++ b/apps/web/src/components/BranchToolbar.browser.tsx
@@ -0,0 +1,133 @@
+import "../index.css";
+
+import { MessageId, ProjectId, ThreadId } from "@t3tools/contracts";
+import { page } from "vitest/browser";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { render } from "vitest-browser-react";
+
+import { useComposerDraftStore } from "../composerDraftStore";
+import { useStore } from "../store";
+import BranchToolbar from "./BranchToolbar";
+
+vi.mock("./BranchToolbarBranchSelector", () => ({
+  BranchToolbarBranchSelector: () => <div data-testid="branch-selector" />,
+}));
+
+const THREAD_ID = ThreadId.makeUnsafe("thread-branch-toolbar");
+const PROJECT_ID = ProjectId.makeUnsafe("project-branch-toolbar");
+
+describe("BranchToolbar", () => {
+  beforeEach(() => {
+    localStorage.clear();
+    document.body.innerHTML = "";
+    useComposerDraftStore.setState({
+      draftsByThreadId: {},
+      draftThreadsByThreadId: {},
+      projectDraftThreadIdByProjectId: {},
+    });
+    useStore.setState({
+      projects: [
+        {
+          id: PROJECT_ID,
+          name: "Project",
+          cwd: "/repo/project",
+          model: "gpt-5",
+          expanded: true,
+          scripts: [],
+        },
+      ],
+      threads: [],
+      threadsHydrated: false,
+    });
+  });
+
+  afterEach(() => {
+    document.body.innerHTML = "";
+  });
+
+  it("renders a segmented local/worktree toggle for editable draft threads", async () => {
+    useComposerDraftStore.setState({
+      draftThreadsByThreadId: {
+        [THREAD_ID]: {
+          projectId: PROJECT_ID,
+          createdAt: "2026-03-11T10:00:00.000Z",
+          runtimeMode: "full-access",
+          interactionMode: "default",
+          branch: "main",
+          worktreePath: null,
+          envMode: "local",
+        },
+      },
+      projectDraftThreadIdByProjectId: {
+        [PROJECT_ID]: THREAD_ID,
+      },
+    });
+
+    const onEnvModeChange = vi.fn<(mode: "local" | "worktree") => void>();
+    await render(
+      <BranchToolbar threadId={THREAD_ID} envLocked={false} onEnvModeChange={onEnvModeChange} />,
+    );
+
+    const localToggle = page.getByRole("button", { name: "Local" });
+    const worktreeToggle = page.getByRole("button", { name: "New worktree" });
+
+    await expect.element(localToggle).toHaveAttribute("aria-pressed", "true");
+    await expect.element(worktreeToggle).toHaveAttribute("aria-pressed", "false");
+
+    await worktreeToggle.click();
+
+    expect(onEnvModeChange).toHaveBeenCalledTimes(1);
+    expect(onEnvModeChange).toHaveBeenCalledWith("worktree");
+  });
+
+  it("keeps the selected mode visible when the environment is locked", async () => {
+    useStore.setState({
+      projects: useStore.getState().projects,
+      threads: [
+        {
+          id: THREAD_ID,
+          codexThreadId: null,
+          projectId: PROJECT_ID,
+          title: "Locked thread",
+          model: "gpt-5",
+          runtimeMode: "full-access",
+          interactionMode: "default",
+          session: null,
+          createdAt: "2026-03-11T10:00:00.000Z",
+          latestTurn: null,
+          lastVisitedAt: undefined,
+          branch: "main",
+          worktreePath: null,
+          turnDiffSummaries: [],
+          activities: [],
+          proposedPlans: [],
+          error: null,
+          messages: [
+            {
+              id: MessageId.makeUnsafe("message-1"),
+              role: "user",
+              text: "hello",
+              streaming: false,
+              createdAt: "2026-03-11T10:00:00.000Z",
+            },
+          ],
+        },
+      ],
+      threadsHydrated: false,
+    });
+
+    const onEnvModeChange = vi.fn<(mode: "local" | "worktree") => void>();
+    await render(
+      <BranchToolbar threadId={THREAD_ID} envLocked onEnvModeChange={onEnvModeChange} />,
+    );
+
+    const localToggle = page.getByRole("button", { name: "Local" });
+    const worktreeToggle = page.getByRole("button", { name: "New worktree" });
+
+    await expect.element(localToggle).toBeDisabled();
+    await expect.element(worktreeToggle).toBeDisabled();
+    await expect.element(localToggle).toHaveAttribute("aria-pressed", "true");
+
+    expect(onEnvModeChange).not.toHaveBeenCalled();
+  });
+});
diff --git a/apps/web/src/components/BranchToolbar.tsx b/apps/web/src/components/BranchToolbar.tsx
index b2c60b2429..2ba8112f45 100644
--- a/apps/web/src/components/BranchToolbar.tsx
+++ b/apps/web/src/components/BranchToolbar.tsx
@@ -11,7 +11,7 @@ import {
   resolveEffectiveEnvMode,
 } from "./BranchToolbar.logic";
 import { BranchToolbarBranchSelector } from "./BranchToolbarBranchSelector";
-import { Button } from "./ui/button";
+import { Toggle, ToggleGroup } from "./ui/toggle-group";
 
 interface BranchToolbarProps {
   threadId: ThreadId;
@@ -47,6 +47,9 @@ export default function BranchToolbar({
     hasServerThread,
     draftThreadEnvMode: draftThread?.envMode,
   });
+  const envToggleValue = activeWorktreePath ? "worktree" : effectiveEnvMode;
+  const envToggleDisabled = envLocked || activeWorktreePath !== null;
+  const worktreeToggleLabel = activeWorktreePath ? "Worktree" : "New worktree";
 
   const setThreadBranch = useCallback(
     (branch: string | null, worktreePath: string | null) => {
@@ -103,23 +106,40 @@ export default function BranchToolbar({
   if (!activeThreadId || !activeProject) return null;
 
   return (
-    <div className="mx-auto flex w-full max-w-3xl items-center justify-between px-5 pb-3 pt-1">
-      <div className="flex items-center gap-2">
-        {envLocked || activeWorktreePath ? (
-          <span className="border border-transparent px-[calc(--spacing(2)-1px)] text-sm font-medium text-muted-foreground/70 sm:text-xs">
-            {activeWorktreePath ? "Worktree" : "Local"}
-          </span>
-        ) : (
-          <Button
-            type="button"
-            variant="ghost"
-            className="text-muted-foreground/70 hover:text-foreground/80"
-            size="xs"
-            onClick={() => onEnvModeChange(effectiveEnvMode === "local" ? "worktree" : "local")}
+    <div className="mx-auto flex w-full max-w-3xl items-center justify-between gap-3 px-5 pb-3 pt-1">
+      <div className="flex shrink-0 items-center gap-2">
+        <ToggleGroup
+          aria-label="Thread workspace mode"
+          className="shrink-0"
+          size="xs"
+          variant="outline"
+          multiple={false}
+          value={[envToggleValue]}
+          onValueChange={(value) => {
+            if (envToggleDisabled) return;
+            const nextMode = value[0];
+            if ((nextMode === "local" || nextMode === "worktree") && nextMode !== envToggleValue) {
+              onEnvModeChange(nextMode);
+            }
+          }}
+        >
+          <Toggle
+            className="px-3"
+            disabled={envToggleDisabled}
+            title="Use the local repository"
+            value="local"
           >
-            {effectiveEnvMode === "worktree" ? "New worktree" : "Local"}
-          </Button>
-        )}
+            Local
+          </Toggle>
+          <Toggle
+            className="px-3"
+            disabled={envToggleDisabled}
+            title="Use a separate worktree"
+            value="worktree"
+          >
+            {worktreeToggleLabel}
+          </Toggle>
+        </ToggleGroup>
       </div>
 
       <BranchToolbarBranchSelector
diff --git a/apps/web/src/components/ChatView.logic.ts b/apps/web/src/components/ChatView.logic.ts
index 59e2904310..f06ca39d9c 100644
--- a/apps/web/src/components/ChatView.logic.ts
+++ b/apps/web/src/components/ChatView.logic.ts
@@ -116,6 +116,17 @@ export function cloneComposerImageForRetry(
   }
 }
 
+export function extendReplacementRangeForTrailingSpace(
+  text: string,
+  rangeEnd: number,
+  replacement: string,
+): number {
+  if (!replacement.endsWith(" ")) {
+    return rangeEnd;
+  }
+  return text[rangeEnd] === " " ? rangeEnd + 1 : rangeEnd;
+}
+
 export function getCustomModelOptionsByProvider(settings: {
   customCodexModels: readonly string[];
 }): Record<ProviderKind, ReadonlyArray<{ slug: string; name: string }>> {
diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
index 64c15ba2fc..9c1ad09521 100644
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -149,6 +149,7 @@ import {
   buildTemporaryWorktreeBranchName,
   cloneComposerImageForRetry,
   collectUserMessageBlobPreviewUrls,
+  extendReplacementRangeForTrailingSpace,
   getCustomModelOptionsByProvider,
   LAST_INVOKED_SCRIPT_BY_PROJECT_KEY,
   LastInvokedScriptByProjectSchema,
@@ -2968,17 +2969,6 @@ export default function ChatView({ threadId }: ChatViewProps) {
     };
   }, [composerCursor]);
 
-  const extendReplacementRangeForTrailingSpace = (
-    text: string,
-    rangeEnd: number,
-    replacement: string,
-  ): number => {
-    if (!replacement.endsWith(" ")) {
-      return rangeEnd;
-    }
-    return text[rangeEnd] === " " ? rangeEnd + 1 : rangeEnd;
-  };
-
   const resolveActiveComposerTrigger = useCallback((): {
     snapshot: { value: string; cursor: number; expandedCursor: number };
     trigger: ComposerTrigger | null;
diff --git a/apps/web/vitest.browser.config.ts b/apps/web/vitest.browser.config.ts
index c67fdfbe99..160878e058 100644
--- a/apps/web/vitest.browser.config.ts
+++ b/apps/web/vitest.browser.config.ts
@@ -16,6 +16,7 @@ export default mergeConfig(
     },
     test: {
       include: [
+        "src/components/BranchToolbar.browser.tsx",
         "src/components/ChatView.browser.tsx",
         "src/components/KeybindingsToast.browser.tsx",
       ],