[Bugfix][Qwen3-Omni] Default the talker voice to Ethan (#8568)

Signed-off-by: Yueqian Lin <linyueqian@outlook.com>

tests/model_executor/models/qwen3_omni/test_qwen3_omni_default_speaker.py

@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
+"""Regression tests for the Qwen3-Omni default talker voice.
+
+The released checkpoint lists ``talker_config.speaker_id`` as
+``{"chelsie": 2301, "ethan": 2302, "aiden": 2303}``. The default voice used to
+be the first key, so a request that named no speaker was spoken by Chelsie,
+while the reference ``generate(speaker="Ethan")`` (and other servers) use Ethan.
+Benchmarks that omit ``speaker`` then compared two different voices.
+"""
+
+import pytest
+
+from vllm_omni.model_executor.models.qwen3_omni.qwen3_omni import (
+    DEFAULT_SPEAKER,
+    Qwen3OmniMoeForConditionalGeneration,
+    resolve_default_speaker,
+)
+
+pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
+
+# Order as shipped in Qwen/Qwen3-Omni-30B-A3B-Instruct config.json.
+CHECKPOINT_SPEAKER_IDS = {"chelsie": 2301, "ethan": 2302, "aiden": 2303}
+
+
+def test_default_speaker_is_ethan_even_when_listed_second() -> None:
+    assert DEFAULT_SPEAKER == "ethan"
+    assert resolve_default_speaker(CHECKPOINT_SPEAKER_IDS) == "ethan"
+
+
+def test_default_speaker_falls_back_to_first_key_without_ethan() -> None:
+    assert resolve_default_speaker({"chelsie": 1, "aiden": 2}) == "chelsie"
+
+
+def test_unknown_or_missing_speaker_uses_ethan_token() -> None:
+    model = object.__new__(Qwen3OmniMoeForConditionalGeneration)
+    model.tts_text_spk_token_ids = dict(CHECKPOINT_SPEAKER_IDS)
+    model.default_tts_text_spk_type = resolve_default_speaker(model.tts_text_spk_token_ids)
+
+    assert model._get_text_spk_token_id("not-a-speaker") == CHECKPOINT_SPEAKER_IDS["ethan"]
+    assert model._get_text_spk_token_id(model.default_tts_text_spk_type) == CHECKPOINT_SPEAKER_IDS["ethan"]
+    assert model._get_text_spk_token_id("chelsie") == CHECKPOINT_SPEAKER_IDS["chelsie"]