fix(subagent): capture latest non-empty findings from child runs

src/agent/subagent/announce-findings.test.ts

@@ -0,0 +1,67 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+const readEntriesMock = vi.fn();
+
+vi.mock("../session/storage.js", () => ({
+  readEntries: (sessionId: string) => readEntriesMock(sessionId),
+}));
+
+import { readLatestAssistantReply } from "./announce.js";
+
+describe("readLatestAssistantReply", () => {
+  beforeEach(() => {
+    readEntriesMock.mockReset();
+  });
+
+  it("returns the latest non-empty assistant text when the last assistant message is tool-only", () => {
+    readEntriesMock.mockReturnValue([
+      {
+        type: "message",
+        timestamp: 1,
+        message: {
+          role: "assistant",
+          content: [{ type: "text", text: "南京天气：晴，12°C。" }],
+        },
+      },
+      {
+        type: "message",
+        timestamp: 2,
+        message: {
+          role: "assistant",
+          content: [{ type: "toolCall", id: "tool-1", name: "weather", arguments: { city: "Nanjing" } }],
+        },
+      },
+    ]);
+
+    const result = readLatestAssistantReply("child-session");
+    expect(result).toBe("南京天气：晴，12°C。");
+  });
+
+  it("falls back to latest toolResult text when no assistant text exists", () => {
+    readEntriesMock.mockReturnValue([
+      {
+        type: "message",
+        timestamp: 1,
+        message: {
+          role: "assistant",
+          content: [{ type: "toolCall", id: "tool-2", name: "weather", arguments: { city: "Nanjing" } }],
+        },
+      },
+      {
+        type: "message",
+        timestamp: 2,
+        message: {
+          role: "toolResult",
+          toolCallId: "tool-2",
+          toolName: "weather",
+          content: [{ type: "text", text: "{\"city\":\"Nanjing\",\"tempC\":12,\"condition\":\"Sunny\"}" }],
+          isError: false,
+        },
+      },
+    ]);
+
+    const result = readLatestAssistantReply("child-session");
+    expect(result).toContain("\"city\":\"Nanjing\"");
+    expect(result).toContain("\"condition\":\"Sunny\"");
+  });
+});

src/agent/subagent/announce.ts

@@ -39,19 +39,29 @@ export function buildSubagentSystemPrompt(params: SubagentSystemPromptParams): s
  */
 export function readLatestAssistantReply(sessionId: string): string | undefined {
   const entries = readEntries(sessionId);
+  let latestToolResultText: string | undefined;
 
-  // Walk backwards to find last assistant message
+  // Walk backwards to find the last non-empty assistant reply.
+  // If no assistant text exists (e.g. run ended after tool execution),
+  // fall back to the latest non-empty toolResult content.
   for (let i = entries.length - 1; i >= 0; i--) {
     const entry = entries[i]!;
     if (entry.type !== "message") continue;
 
     const message = entry.message;
-    if (message.role !== "assistant") continue;
+    if (message.role === "assistant") {
+      const text = extractAssistantText(message);
+      if (text) return text;
+      continue;
+    }
 
-    return extractAssistantText(message);
+    if (message.role === "toolResult" && !latestToolResultText) {
+      const text = extractToolResultText(message);
+      if (text) latestToolResultText = text;
+    }
   }
 
-  return undefined;
+  return latestToolResultText;
 }
 
 /**
@@ -59,7 +69,17 @@ export function readLatestAssistantReply(sessionId: string): string | undefined
  * AgentMessage.content for assistant is (TextContent | ThinkingContent | ToolCall)[].
  */
 function extractAssistantText(message: { role: string; content: unknown }): string {
-  const content = message.content;
+  return extractTextLikeContent(message.content);
+}
+
+/**
+ * Extract text content from a toolResult message.
+ */
+function extractToolResultText(message: { role: string; content: unknown }): string {
+  return extractTextLikeContent(message.content);
+}
+
+function extractTextLikeContent(content: unknown): string {
   if (typeof content === "string") {
     return sanitizeText(content);
   }
@@ -68,8 +88,9 @@ function extractAssistantText(message: { role: string; content: unknown }): stri
 
   const textParts: string[] = [];
   for (const block of content) {
-    if (block && typeof block === "object" && "type" in block && block.type === "text" && "text" in block) {
-      textParts.push(String(block.text));
+    if (!block || typeof block !== "object") continue;
+    if ("text" in block) {
+      textParts.push(String((block as { text: unknown }).text));
     }
   }