diff --git a/tests/e2e/conftest.py b/tests/e2e/conftest.py
new file mode 100644
index 0000000000..846557802f
--- /dev/null
+++ b/tests/e2e/conftest.py
@@ -0,0 +1,9 @@
+"""Configuration for e2e tests that rely on Unix PTY infrastructure."""
+
+from __future__ import annotations
+
+import sys
+
+# PTY-based e2e tests depend on Unix-only modules (fcntl, termios, pty).
+# Skip the entire directory on Windows to prevent ImportError during collection.
+collect_ignore_glob = ["test_*.py"] if sys.platform == "win32" else []
diff --git a/tests/tools/test_background_tools.py b/tests/tools/test_background_tools.py
index 75cc79b55e..30292df2ed 100644
--- a/tests/tools/test_background_tools.py
+++ b/tests/tools/test_background_tools.py
@@ -23,7 +23,7 @@ def _write_task(runtime, task_id: str, *, status: TaskStatus, output: str = ""):
         timeout_s=60,
     )
     store.create_task(spec)
-    store.output_path(task_id).write_text(output, encoding="utf-8")
+    store.output_path(task_id).write_text(output, encoding="utf-8", newline="")
     runtime_state = TaskRuntime(status=status, updated_at=time.time())
     if status in {"completed", "failed", "killed", "lost"}:
         runtime_state.finished_at = time.time()
@@ -57,7 +57,7 @@ def _write_agent_task(
     )
     store.create_task(spec)
     if task_output:
-        store.output_path(task_id).write_text(task_output, encoding="utf-8")
+        store.output_path(task_id).write_text(task_output, encoding="utf-8", newline="")
     runtime_state = TaskRuntime(status=status, updated_at=time.time())
     if status in {"completed", "failed", "killed", "lost"}:
         runtime_state.finished_at = time.time()
@@ -66,7 +66,7 @@ def _write_agent_task(
     # Write subagent output (the live file)
     subagent_dir = runtime.subagent_store.instance_dir(agent_id, create=True)
     subagent_output_path = subagent_dir / "output"
-    subagent_output_path.write_text(subagent_output, encoding="utf-8")
+    subagent_output_path.write_text(subagent_output, encoding="utf-8", newline="")
     return spec