diff --git a/src/auto-reply/reply/session.test.ts b/src/auto-reply/reply/session.test.ts
index 12433057b..c17837bb4 100644
--- a/src/auto-reply/reply/session.test.ts
+++ b/src/auto-reply/reply/session.test.ts
@@ -326,12 +326,13 @@ describe("initSessionState thread forking", () => {
     expect(result.sessionEntry.forkedFromParent).toBe(true);
     expect(result.sessionEntry.sessionFile).toBeTruthy();
     const forkedContent = await fs.readFile(result.sessionEntry.sessionFile ?? "", "utf-8");
-    const [sessionHeaderLine] = forkedContent.split("\n");
-    const sessionHeader = JSON.parse(sessionHeaderLine ?? "{}") as { parentSession?: string };
-    expect(sessionHeader.parentSession).toBeTruthy();
-    const resolvedParentSession = await fs.realpath(parentSessionFile);
-    const resolvedForkParentSession = await fs.realpath(sessionHeader.parentSession ?? "");
-    expect(resolvedForkParentSession).toBe(resolvedParentSession);
+    const [headerLine] = forkedContent.split(/\r?\n/).filter((line) => line.trim().length > 0);
+    const parsedHeader = JSON.parse(headerLine) as { parentSession?: string };
+    const expectedParentSession = await fs.realpath(parentSessionFile);
+    const actualParentSession = parsedHeader.parentSession
+      ? await fs.realpath(parsedHeader.parentSession)
+      : undefined;
+    expect(actualParentSession).toBe(expectedParentSession);
   });
 
   it("records topic-specific session files when MessageThreadId is present", async () => {