diff --git a/tests/ipcMain/helpers.ts b/tests/ipcMain/helpers.ts
index 4eaea823dd..de27d7fae8 100644
--- a/tests/ipcMain/helpers.ts
+++ b/tests/ipcMain/helpers.ts
@@ -232,7 +232,16 @@ export async function sendMessageAndWait(
 
   // Wait for stream completion
   const collector = createEventCollector(env.sentEvents, workspaceId);
-  await collector.waitForEvent("stream-end", timeoutMs);
+  const streamEnd = await collector.waitForEvent("stream-end", timeoutMs);
+
+  if (!streamEnd) {
+    collector.logEventDiagnostics(`sendMessageAndWait timeout after ${timeoutMs}ms`);
+    throw new Error(
+      `sendMessageAndWait: Timeout waiting for stream-end after ${timeoutMs}ms.\n` +
+        `See detailed event diagnostics above.`
+    );
+  }
+
   return collector.getEvents();
 }
 
diff --git a/tests/ipcMain/resumeStream.test.ts b/tests/ipcMain/resumeStream.test.ts
index b0edd8b442..e43cc6e0da 100644
--- a/tests/ipcMain/resumeStream.test.ts
+++ b/tests/ipcMain/resumeStream.test.ts
@@ -192,26 +192,25 @@ describeIntegration("IpcMain resumeStream integration tests", () => {
           .filter((e) => "role" in e && e.role === "assistant");
         expect(assistantMessages.length).toBeGreaterThan(0);
 
-        // Verify we received content deltas
-        const deltas = collector.getDeltas();
-        expect(deltas.length).toBeGreaterThan(0);
-
         // Verify no stream errors
         const streamErrors = collector
           .getEvents()
           .filter((e) => "type" in e && e.type === "stream-error");
         expect(streamErrors.length).toBe(0);
 
-        // Verify the assistant responded with actual content and said the verification word
-        const allText = deltas
-          .filter((d) => "delta" in d)
-          .map((d) => ("delta" in d ? d.delta : ""))
-          .join("");
-        expect(allText.length).toBeGreaterThan(0);
+        // Get the final message content from stream-end parts
+        // StreamEndEvent has parts: Array<MuxTextPart | MuxReasoningPart | MuxToolPart>
+        const finalMessage = collector.getFinalMessage() as any;
+        expect(finalMessage).toBeDefined();
+        const textParts = (finalMessage?.parts ?? []).filter(
+          (p: any) => p.type === "text" && p.text
+        );
+        const finalContent = textParts.map((p: any) => p.text).join("");
+        expect(finalContent.length).toBeGreaterThan(0);
 
         // Verify the assistant followed the instruction and said the verification word
         // This proves resumeStream properly loaded history and continued from it
-        expect(allText).toContain(verificationWord);
+        expect(finalContent).toContain(verificationWord);
       } finally {
         await cleanup();
       }