diff --git a/packages/dashboard/app/components/TaskChatTab.css b/packages/dashboard/app/components/TaskChatTab.css
index ba41617002..f84c0ac5af 100644
--- a/packages/dashboard/app/components/TaskChatTab.css
+++ b/packages/dashboard/app/components/TaskChatTab.css
@@ -539,11 +539,16 @@ FN-7241 adds timestamps inside individual task-detail transcript blocks. Keep bl
   gap: var(--space-sm);
 }
 
+/*
+FNXC:TaskDetailChat 2026-07-21-23:42:
+FN-8473 requires the Activity Live steering input to share the transcript panel's --radius-lg so the composer does not look sharper than the panel above it.
+*/
 .task-chat-input {
   min-height: calc(var(--space-2xl) + var(--space-sm));
   max-height: var(--task-chat-composer-max-height, 40vh);
   resize: none;
   flex: 1 1 auto;
+  border-radius: var(--radius-lg);
 }
 
 /*
diff --git a/packages/dashboard/app/components/__tests__/TaskChatTab.test.tsx b/packages/dashboard/app/components/__tests__/TaskChatTab.test.tsx
index 88158901d9..9bbb94bc24 100644
--- a/packages/dashboard/app/components/__tests__/TaskChatTab.test.tsx
+++ b/packages/dashboard/app/components/__tests__/TaskChatTab.test.tsx
@@ -2776,6 +2776,21 @@ describe("TaskChatTab", () => {
     expect(css).not.toContain("62vh");
   });
 
+  it("matches the Activity Live composer radius to its transcript on desktop and mobile", () => {
+    const css = readFileSync(resolve(__dirname, "../TaskChatTab.css"), "utf8");
+    const sharedStyles = readFileSync(resolve(__dirname, "../../styles.css"), "utf8");
+    const transcriptRule = getCssRuleBlock(css, ".task-chat-transcript");
+    const inputRule = getCssRuleBlock(css, ".task-chat-input");
+    const mobileCss = getCssAfter(css, "@media (max-width: 768px)");
+    const mobileInputRule = getCssRuleBlock(mobileCss, ".task-chat-input");
+    const globalInputRule = getCssRuleBlock(sharedStyles, ".input,");
+
+    expect(getCssDeclaration(transcriptRule, "border-radius")).toBe("var(--radius-lg)");
+    expect(getCssDeclaration(inputRule, "border-radius")).toBe("var(--radius-lg)");
+    expect(mobileInputRule).not.toMatch(/border-radius\s*:/);
+    expect(getCssDeclaration(globalInputRule, "border-radius")).toBe("var(--radius-sm)");
+  });
+
   it("positions the icon-only expand toggle as a tokenized chat-view overlay with no toolbar shell", () => {
     const css = readFileSync(resolve(__dirname, "../TaskChatTab.css"), "utf8");
     const tabRule = getCssRuleBlock(css, ".task-chat-tab");