diff --git a/ui/src/components/task-chat/TaskChatDescriptionBubble.test.tsx b/ui/src/components/task-chat/TaskChatDescriptionBubble.test.tsx
index 172f8118aff..a89465abf63 100644
--- a/ui/src/components/task-chat/TaskChatDescriptionBubble.test.tsx
+++ b/ui/src/components/task-chat/TaskChatDescriptionBubble.test.tsx
@@ -95,8 +95,16 @@ describe("TaskChatDescriptionBubble (PAP-375)", () => {
     expect(bubble?.className).toContain("items-start");
     expect(bubble?.querySelector('[data-testid="task-chat-agent-avatar"]')).not.toBeNull();
     expect(bubble?.textContent).toContain("CEO");
-    expect(bubble?.querySelector(".bg-\\(--bubble-agent\\)")).not.toBeNull();
+    // PAP-501: agent prose sits on the page surface. The description is agent
+    // prose when an agent opened the task, so it carries no card fill, no
+    // rounding and no width cap — matching TaskChatBubble's agent branch.
+    expect(bubble?.querySelector(".bg-\\(--bubble-agent\\)")).toBeNull();
     expect(bubble?.querySelector(".bg-\\(--liveness-blue\\)")).toBeNull();
+    const agentBody = bubble?.querySelector(".bg-transparent");
+    expect(agentBody).not.toBeNull();
+    expect(agentBody?.className).toContain("w-full");
+    expect(agentBody?.className).not.toContain("rounded-2xl");
+    expect(agentBody?.className).not.toContain("max-w-(--pct-85)");
   });
 
   it("renders the live description — a new value shows without remount", () => {
diff --git a/ui/src/components/task-chat/TaskChatDescriptionBubble.tsx b/ui/src/components/task-chat/TaskChatDescriptionBubble.tsx
index 28c874ac061..5c504cc9ed5 100644
--- a/ui/src/components/task-chat/TaskChatDescriptionBubble.tsx
+++ b/ui/src/components/task-chat/TaskChatDescriptionBubble.tsx
@@ -135,11 +135,17 @@ export function TaskChatDescriptionBubble({ brief }: TaskChatDescriptionBubblePr
         )}
       >
         <div
+          // PAP-501 put agent prose on the page surface: no card fill, no
+          // rounding, full width. TaskChatBubble already does this for agent
+          // messages. The description is agent prose too when an agent opened
+          // the task, so it follows the same rule rather than keeping a
+          // --bubble-agent card that no other agent text still uses. The human
+          // side keeps its accent bubble.
           className={cn(
-            "max-w-(--pct-85) break-words px-3.5 py-2 text-sm",
+            "break-words py-2 text-sm",
             isHuman
-              ? "rounded-2xl rounded-br-sm bg-(--liveness-blue) text-white"
-              : "rounded-2xl rounded-bl-sm bg-(--bubble-agent) text-foreground",
+              ? "max-w-(--pct-85) rounded-2xl rounded-br-sm bg-(--liveness-blue) px-3.5 text-white"
+              : "w-full bg-transparent px-1 text-foreground",
           )}
         >
           <FoldCurtain