[Bugfix] Forward Qwen3-Omni streaming video sampling parameters (#7325)

Signed-off-by: psv666 <2693925048@qq.com>

docs/serving/video_stream_api.md

@@ -60,10 +60,24 @@ WebSocket /v1/video/chat/stream
 | `max_frames` | integer, 1-256 | `50` | Maximum retained frame buffer size. Oldest frames are evicted first. |
 | `system_prompt` | string or null | null | Optional custom system prompt. |
 | `use_audio_in_video` | bool | `true` | Include streamed audio chunks in multimodal video understanding when audio is present. |
-| `sampling_params_list` | list or null | null | Optional per-stage sampling parameter overrides. |
+| `sampling_params_list` | list or null | null | Optional per-stage parameter dictionaries. Each provided entry replaces that stage's deployment sampling settings. |
 | `enable_frame_filter` | bool | `true` | Enable EVS near-duplicate frame filtering. |
 | `frame_filter_threshold` | float, 0.0-1.0 | `0.95` | EVS similarity threshold. Higher keeps more frames; lower drops more near-duplicates. |
 
+Sampling parameter bugfix: `sampling_params_list` is now forwarded to the engine;
+earlier versions accepted this field but silently used deployment defaults instead.
+Each provided entry constructs a fresh `SamplingParams` for that stage in pipeline
+order; it is not merged with that stage's deployment defaults. Fields absent from a
+provided entry use `SamplingParams` constructor defaults. Only omitted trailing
+stages keep their deployment defaults. An omitted, `null`, or empty list keeps the
+engine defaults. Invalid sampling parameters return an `error` when the query is
+submitted.
+
+For example, `[{"temperature": 0.2, "max_tokens": 64}]` configures the thinker while
+the talker and code2wav retain their deployment defaults. With only
+`[{"temperature": 0.2}]`, the thinker's `max_tokens` and `top_p` use constructor
+defaults, not its YAML values.
+
 ### Legacy Aliases
 
 The server accepts these legacy field names and rewrites them before validation. New clients should send the canonical names above.