[Bugfix] Reject instructions changes on locked native duplex sessions (#6318)

Signed-off-by: ANURAG KANADE <anuragkanade6@gmail.com>

tests/e2e/features/fullduplex/personaplex/test_unified_runtime.py

@@ -18,6 +18,10 @@ from vllm_omni.experimental.fullduplex.engine.duplex_runtime import (
     DuplexInputMode,
 )
 from vllm_omni.experimental.fullduplex.engine.messages import DuplexFence
+from vllm_omni.experimental.fullduplex.openai.runtime_adapter import (
+    ServingRuntimeConfigError,
+)
+from vllm_omni.experimental.fullduplex.personaplex.config import DEFAULT_PERSONA
 from vllm_omni.experimental.fullduplex.personaplex.data_plane import (
     PersonaPlexDataPlaneContext,
     PersonaPlexDataPlaneSession,
@@ -242,6 +246,53 @@ def test_personaplex_capabilities_are_honest() -> None:
     assert multi.supports_barge_in is False
 
 
+def test_personaplex_runtime_config_update_rejects_changed_persona() -> None:
+    adapter = PersonaPlexServingRuntimeAdapter(lambda *_: None)
+    short_persona = "You are a helpful assistant."
+    longer_persona = (
+        "You are now a swashbuckling pirate captain who speaks entirely in "
+        "nautical slang, references buried treasure constantly, and never "
+        "breaks character no matter what the user asks."
+    )
+    current = {"personaplex_persona": short_persona, "personaplex_voice_prompt": "NATF2.pt"}
+
+    with pytest.raises(ServingRuntimeConfigError, match="persona"):
+        adapter.runtime_config_for_update(
+            SimpleNamespace(instructions=longer_persona, extra_body={}),
+            current,
+        )
+
+    unchanged = adapter.runtime_config_for_update(
+        SimpleNamespace(instructions=short_persona, extra_body={}),
+        current,
+    )
+    assert unchanged["personaplex_persona"] == short_persona
+
+
+def test_personaplex_runtime_config_update_rejects_changed_voice() -> None:
+    adapter = PersonaPlexServingRuntimeAdapter(lambda *_: None)
+    current = {"personaplex_persona": DEFAULT_PERSONA, "personaplex_voice_prompt": "NATF2.pt"}
+
+    with pytest.raises(ServingRuntimeConfigError, match="voice"):
+        adapter.runtime_config_for_update(
+            SimpleNamespace(instructions=None, voice="OtherVoice.pt", extra_body={}),
+            current,
+        )
+
+    unchanged = adapter.runtime_config_for_update(
+        SimpleNamespace(instructions=None, voice="NATF2.pt", extra_body={}),
+        current,
+    )
+    assert unchanged["personaplex_voice_prompt"] == "NATF2.pt"
+
+
+def test_personaplex_rejects_minicpmo_only_opt_out_flag() -> None:
+    adapter = PersonaPlexServingRuntimeAdapter(lambda *_: None)
+
+    with pytest.raises(ServingRuntimeConfigError, match="minicpmo45_native_duplex"):
+        adapter.validate_client_extra_body({"minicpmo45_native_duplex": False})
+
+
 def test_pcm_buffer_emits_one_80ms_frame_transactionally() -> None:
     buffer = PersonaPlexPcmAppendBuffer()
     reservation = buffer.prepare_append(