fix(plugins): preserve agent message provenance in timeline transforms

Co-authored-by: RoundRedDot <roundreddot@gmail.com>

packages/app/src/plugins/timeline/projection.test.ts

@@ -14,6 +14,45 @@ function thought(text: string, status: "loading" | "ready" = "loading"): StreamI
 }
 
 describe("plugin timeline projection", () => {
+  it.each(["message", "finished", "errored", "permission-required", "closed"] as const)(
+    "preserves immutable agent-message provenance for %s cards",
+    (event) => {
+      const agentMessage = {
+        event,
+        sender: { id: "remote::reviewer", title: "QA question-timing #7014/#7000/#6809" },
+        text: "The original message, including **Markdown**.",
+      };
+      const source: StreamItem = {
+        kind: "tool_call",
+        id: "message-1",
+        timestamp: new Date("2026-01-01T00:00:00.000Z"),
+        payload: {
+          source: "agent",
+          data: {
+            provider: "codex",
+            callId: "delivery-1",
+            name: "agent_message",
+            status: "completed",
+            error: null,
+            detail: { type: "plain_text", text: agentMessage.text, icon: "bot" },
+            agentMessage,
+          },
+        },
+      };
+      const inspect: TimelineItemTransform = ({ item }) => {
+        expect(item.type).toBe("tool_call");
+        if (item.type !== "tool_call") throw new Error("Expected a tool call");
+        expect(item.agentMessage).toEqual(agentMessage);
+        expect(item.agentMessage).not.toBe(agentMessage);
+        expect(Object.isFrozen(item.agentMessage)).toBe(true);
+        expect(Object.isFrozen(item.agentMessage?.sender)).toBe(true);
+        return undefined;
+      };
+      expect(projectPluginTimelineItems([source], inspect)).toEqual([source]);
+      expect(Object.isFrozen(agentMessage.sender)).toBe(false);
+    },
+  );
+
   it("does not expose mutable tool detail from stream state", () => {
     const detail = { type: "read" as const, filePath: "/repo/original.ts" };
     const source: StreamItem = {

packages/app/src/plugins/timeline/projection.ts

@@ -22,13 +22,14 @@ function cloneAndFreeze<T>(value: T): T {
 }
 
 function sourceToolCallTimelineItem(data: AgentToolCallData): ToolCallTimelineItem {
-  const { callId, name, status, error, detail, metadata } = data;
+  const { callId, name, status, error, detail, metadata, agentMessage } = data;
   const base = {
     type: "tool_call" as const,
     callId,
     name,
     detail,
     ...(metadata ? { metadata } : {}),
+    ...(agentMessage ? { agentMessage } : {}),
   };
   switch (status) {
     case "running":