diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
index 3362622b7efd15aa91b80a67fc08b2867934f6ac..52085daa459321a900664bd6cb7c591a48355695 100644
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -3468,7 +3468,7 @@ export default function ChatView({ threadId }: ChatViewProps) {
         onDismiss={() => setThreadError(activeThread.id, null)}
       />
       {/* Main content area with optional plan sidebar */}
-      <div className="flex min-h-0 flex-1">
+      <div className="flex min-h-0 min-w-0 flex-1">
         {/* Chat column */}
         <div className="flex min-h-0 min-w-0 flex-1 flex-col">
 
@@ -3953,6 +3953,15 @@ export default function ChatView({ threadId }: ChatViewProps) {
         </form>
       </div>
 
+      {isGitRepo && (
+        <BranchToolbar
+          threadId={activeThread.id}
+          onEnvModeChange={onEnvModeChange}
+          envLocked={envLocked}
+          onComposerFocusRequest={scheduleComposerFocus}
+        />
+      )}
+
         </div>{/* end chat column */}
 
         {/* Plan sidebar */}
@@ -3974,15 +3983,6 @@ export default function ChatView({ threadId }: ChatViewProps) {
         ) : null}
       </div>{/* end horizontal flex container */}
 
-      {isGitRepo && (
-        <BranchToolbar
-          threadId={activeThread.id}
-          onEnvModeChange={onEnvModeChange}
-          envLocked={envLocked}
-          onComposerFocusRequest={scheduleComposerFocus}
-        />
-      )}
-
       {(() => {
         if (!terminalState.terminalOpen || !activeProject) {
           return null;
diff --git a/apps/web/src/components/ui/sidebar.logic.ts b/apps/web/src/components/ui/sidebar.logic.ts
new file mode 100644
index 0000000000000000000000000000000000000000..c9e4b4c1d8cfba537f101c00f3fe7886f8037197
--- /dev/null
+++ b/apps/web/src/components/ui/sidebar.logic.ts
@@ -0,0 +1,2 @@
+export const SIDEBAR_INSET_BASE_CLASSNAME =
+  "relative flex min-w-0 w-full flex-1 flex-col bg-background";
diff --git a/apps/web/src/components/ui/sidebar.test.tsx b/apps/web/src/components/ui/sidebar.test.tsx
new file mode 100644
index 0000000000000000000000000000000000000000..99bf2d0179f7b979e11043ee4624eac589a2c4b2
--- /dev/null
+++ b/apps/web/src/components/ui/sidebar.test.tsx
@@ -0,0 +1,9 @@
+import { describe, expect, it } from "vitest";
+
+import { SIDEBAR_INSET_BASE_CLASSNAME } from "./sidebar.logic";
+
+describe("SidebarInset", () => {
+  it("stays shrinkable inside flex layouts", () => {
+    expect(SIDEBAR_INSET_BASE_CLASSNAME).toContain("min-w-0");
+  });
+});
diff --git a/apps/web/src/components/ui/sidebar.tsx b/apps/web/src/components/ui/sidebar.tsx
index ba77bddc279895af5ba2515279c97a73356486c7..ef79926ef226790d18923b8dc481a246ea1878bf 100644
--- a/apps/web/src/components/ui/sidebar.tsx
+++ b/apps/web/src/components/ui/sidebar.tsx
@@ -18,6 +18,7 @@ import {
 import { Skeleton } from "~/components/ui/skeleton";
 import { Tooltip, TooltipPopup, TooltipTrigger } from "~/components/ui/tooltip";
 import { useMediaQuery } from "~/hooks/useMediaQuery";
+import { SIDEBAR_INSET_BASE_CLASSNAME } from "./sidebar.logic";
 
 const SIDEBAR_COOKIE_NAME = "sidebar_state";
 const SIDEBAR_COOKIE_MAX_AGE = 60 * 60 * 24 * 7;
@@ -595,7 +596,7 @@ function SidebarInset({ className, ...props }: React.ComponentProps<"main">) {
   return (
     <main
       className={cn(
-        "relative flex w-full flex-1 flex-col bg-background",
+        SIDEBAR_INSET_BASE_CLASSNAME,
         "md:peer-data-[variant=inset]:peer-data-[state=collapsed]:ms-2 md:peer-data-[variant=inset]:m-2 md:peer-data-[variant=inset]:ms-0 md:peer-data-[variant=inset]:rounded-xl md:peer-data-[variant=inset]:shadow-sm/5",
         className,
       )}