diff --git a/tests/helpers/runtime.py b/tests/helpers/runtime.py
index 83c45b57bc3..ae65fe159c1 100644
--- a/tests/helpers/runtime.py
+++ b/tests/helpers/runtime.py
@@ -1201,17 +1201,18 @@ def iter_omni_server(
         server_args = params.server_args or []
         if model != original_model:
             server_args = [*server_args, "--served-model-name", original_model]
-        if params.use_omni and params.stage_init_timeout is not None:
-            server_args = [*server_args, "--stage-init-timeout", str(params.stage_init_timeout)]
-        else:
-            server_args = [*server_args, "--stage-init-timeout", "600"]
-        if params.init_timeout is not None:
-            server_args = [*server_args, "--init-timeout", str(params.init_timeout)]
-        else:
-            server_args = [*server_args, "--init-timeout", "900"]
-        # ``omni_server`` / ``omni_server_function``: match ``serve`` (``--disable-log-stats`` wins).
-        if "--disable-log-stats" not in server_args and "--log-stats" not in server_args:
-            server_args = [*server_args, "--log-stats"]
+        if params.use_omni:
+            if params.stage_init_timeout is not None:
+                server_args = [*server_args, "--stage-init-timeout", str(params.stage_init_timeout)]
+            else:
+                server_args = [*server_args, "--stage-init-timeout", "600"]
+            if params.init_timeout is not None:
+                server_args = [*server_args, "--init-timeout", str(params.init_timeout)]
+            else:
+                server_args = [*server_args, "--init-timeout", "900"]
+            # ``omni_server`` / ``omni_server_function``: match ``serve`` (``--disable-log-stats`` wins).
+            if "--disable-log-stats" not in server_args and "--log-stats" not in server_args:
+                server_args = [*server_args, "--log-stats"]
         if params.use_stage_cli:
             if not params.use_omni:
                 raise ValueError("omni_server with use_stage_cli=True requires use_omni=True")
diff --git a/tests/helpers/tests/test_runtime_omni_args.py b/tests/helpers/tests/test_runtime_omni_args.py
new file mode 100644
index 00000000000..37944e18d8e
--- /dev/null
+++ b/tests/helpers/tests/test_runtime_omni_args.py
@@ -0,0 +1,81 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
+
+"""CPU regression tests for iter_omni_server argument assembly.
+
+Verifies that --stage-init-timeout, --init-timeout, and --log-stats are only
+added when use_omni=True.  The use_omni=False assertion fails on baseline
+da572cddb and passes on this head.
+"""
+
+from __future__ import annotations
+
+import threading
+from contextlib import nullcontext
+from types import SimpleNamespace
+
+import pytest
+
+from tests.helpers import runtime
+from tests.helpers.runtime import OmniServerParams
+
+pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
+
+OMNI_ONLY_FLAGS = {"--stage-init-timeout", "--init-timeout", "--log-stats"}
+
+
+def _capture_server_args(monkeypatch: pytest.MonkeyPatch) -> list[str]:
+    captured: list[str] = []
+
+    def fake_omni_server(model, serve_args, **kwargs):
+        del model, kwargs
+        captured.extend(serve_args)
+        return nullcontext(SimpleNamespace(model="fake-model"))
+
+    monkeypatch.setattr(runtime, "OmniServer", fake_omni_server)
+    monkeypatch.setattr(runtime, "_whisper_device_free_around", nullcontext)
+    monkeypatch.setattr(
+        "tests.helpers.stage_config.stage_config_path_for_run_level",
+        lambda _config_path, _run_level: None,
+    )
+    return captured
+
+
+def _run_fixture(params: OmniServerParams):
+    request = SimpleNamespace(
+        param=params,
+        node=SimpleNamespace(get_closest_marker=lambda _name: None),
+    )
+    gen = runtime.iter_omni_server(request, "core_model", threading.Lock())
+    next(gen)
+    with pytest.raises(StopIteration):
+        next(gen)
+
+
+def test_non_omni_skips_omni_flags(monkeypatch: pytest.MonkeyPatch) -> None:
+    captured = _capture_server_args(monkeypatch)
+    _run_fixture(OmniServerParams(model="fake-model", use_omni=False))
+    leaked = OMNI_ONLY_FLAGS & set(captured)
+    assert not leaked, f"Omni-only flags leaked into non-Omni args: {leaked}"
+
+
+def test_omni_defaults(monkeypatch: pytest.MonkeyPatch) -> None:
+    captured = _capture_server_args(monkeypatch)
+    _run_fixture(OmniServerParams(model="fake-model", use_omni=True))
+    assert captured[captured.index("--stage-init-timeout") + 1] == "600"
+    assert captured[captured.index("--init-timeout") + 1] == "900"
+    assert "--log-stats" in captured
+
+
+def test_omni_custom_timeouts(monkeypatch: pytest.MonkeyPatch) -> None:
+    captured = _capture_server_args(monkeypatch)
+    _run_fixture(OmniServerParams(model="fake-model", use_omni=True, stage_init_timeout=120, init_timeout=300))
+    assert captured[captured.index("--stage-init-timeout") + 1] == "120"
+    assert captured[captured.index("--init-timeout") + 1] == "300"
+
+
+def test_omni_disable_log_stats_wins(monkeypatch: pytest.MonkeyPatch) -> None:
+    captured = _capture_server_args(monkeypatch)
+    _run_fixture(OmniServerParams(model="fake-model", use_omni=True, server_args=["--disable-log-stats"]))
+    assert "--disable-log-stats" in captured
+    assert "--log-stats" not in captured