[Frontend] Reject built-in name collisions in voice upload and add VLLM_OMNI_SPEAKER_REGISTRATION_POLICY (#6848)

Signed-off-by: Hoseung Kim <hoseung.kim@navercorp.com>
Co-authored-by: Hoseung Kim <hoseung.kim@navercorp.com>

docs/configuration/environment_variables.md

@@ -88,6 +88,7 @@ depends on the installed kernels and model path.
 | `VLLM_OMNI_EVENT_DRIVEN_ORCH` | `1`, `true`, `yes` or `on` enables; defaults to on for Qwen3-TTS and off for other pipelines | Pipeline default computed from `pipeline_config.model_type` at engine initialization; env override resolved at `Orchestrator` construction and separately when the serving-side final-output drain starts | An explicit env value wins; otherwise both consumers use the engine's pipeline default. Values are stripped and case-normalized; any unrecognized value selects the legacy poll loop. Set before server startup. | Experimental |
 | `VLLM_OMNI_INPUT_WAIT_TIMEOUT_S` | Float seconds; default `600`; `<=0` disables | Full-payload input coordinator, not async-chunk transfer; read when the scheduler module imports in each worker | Environment-only setting. A non-float logs a warning and uses `600`. | Stable operational control |
 | `VLLM_OMNI_ORCH_MONITOR_PATH` | Filesystem path; default `<current-working-directory>/vllm_omni_orch_monitor_<timestamp>.json` | Orchestrator monitor enabled by `--enable-orch-monitor`; read when the monitor is created | Environment-only path override. Parent directories are created; write errors are logged. | Diagnostic |
+| `VLLM_OMNI_SPEAKER_REGISTRATION_POLICY` | `overwrite` or `immutable`; default `overwrite` | Speech server; read when speaker storage initializes | Environment-only setting. `immutable` rejects re-registering an existing uploaded voice name until it is deleted; any other value raises `ValueError` at startup. | Experimental |
 | `VLLM_OMNI_VIDEO_SYNC_TIMEOUT` | Float seconds; default `600` | Synchronous Videos API; read when the API server module imports | Environment-only setting. A non-float raises `ValueError` during import. | Experimental |
 | `VLLM_VIDEO_ASYNC_CHUNK` | `on` or `off`; default `on` | Streaming video output; read on attribute access | Environment-only setting. Values are trimmed and case-normalized; an invalid value warns once and uses `on`. | Experimental |
 | `VLLM_VIDEO_AUDIO_DELTA_MODE` | `fast` or `slow`; default `fast` | Streaming video audio deltas; read on attribute access | Environment-only setting. Values are trimmed and case-normalized; an invalid value warns once and uses `fast`. | Experimental |

docs/serving/speech_api.md

@@ -289,6 +289,19 @@ Upload a new voice sample for voice cloning in Base task TTS requests.
 
 Fields `ref_text` and `speaker_description` are omitted when not provided at upload time.
 
+**Naming rules:**
+
+- Names that collide with one of the model's built-in or precomputed voices are rejected (400). Voice
+  files already on disk under such a name are ignored at startup with a warning, so an upload can never
+  shadow a built-in voice.
+- Re-uploading an existing uploaded name overwrites it in place (the previous audio file is
+  deleted). Set `VLLM_OMNI_SPEAKER_REGISTRATION_POLICY=immutable` on the server to reject duplicates instead,
+  requiring an explicit `DELETE /v1/audio/voices/{name}` before re-registering — useful when the
+  endpoint is reachable by multiple writers and silent overwrites are a risk.
+- The voice registry has no per-user ownership: any client that can reach the endpoint can
+  overwrite (default policy) or delete any uploaded voice. For multi-tenant deployments, add
+  authentication at a proxy and namespace voice names per user (e.g. `{user}.{name}`).
+
 **Usage Example:**
 
 ```bash
@@ -577,6 +590,7 @@ by `GET /v1/audio/voices`. Valid precomputed voices can be used in
 | ---------- | --------- | ------------- |
 | `SPEAKER_SAMPLES_DIR` | `~/.cache/vllm-omni/speakers` | Directory for persisted uploaded speakers (`.safetensors` files). |
 | `SPEAKER_MAX_UPLOADED` | `1000` | Maximum number of uploaded speakers kept on disk. Upload requests past the cap return 400. |
+| `VLLM_OMNI_SPEAKER_REGISTRATION_POLICY` | `overwrite` | `immutable` rejects re-uploading an existing uploaded name (400) until it is deleted; any other value fails startup. |
 
 The in-memory LRU has a fixed 512 MiB byte budget.