feat: add per-model unload endpoint and UI button

- POST /models/{model_name}/unload — unloads a specific model from
  memory without deleting from disk, supports all engine types
- Frontend: Unload button in model detail dialog when model is loaded
- Delete button remains disabled while loaded (unload first)

app/src/components/ServerSettings/ModelManagement.tsx

@@ -13,6 +13,7 @@ import {
   RotateCcw,
   Scale,
   Trash2,
+  Unplug,
   X,
 } from 'lucide-react';
 import { useCallback, useMemo, useState } from 'react';
@@ -300,6 +301,27 @@ export function ModelManagement() {
     },
   });
 
+  const unloadMutation = useMutation({
+    mutationFn: async (modelName: string) => {
+      return await apiClient.unloadModel(modelName);
+    },
+    onSuccess: async (_data, modelName) => {
+      toast({
+        title: 'Model unloaded',
+        description: `${modelName} has been unloaded from memory.`,
+      });
+      await queryClient.invalidateQueries({ queryKey: ['modelStatus'], refetchType: 'all' });
+      await queryClient.refetchQueries({ queryKey: ['modelStatus'] });
+    },
+    onError: (error: Error) => {
+      toast({
+        title: 'Unload failed',
+        description: error.message,
+        variant: 'destructive',
+      });
+    },
+  });
+
   const formatSize = (sizeMb?: number): string => {
     if (!sizeMb) return 'Unknown size';
     if (sizeMb < 1024) return `${sizeMb.toFixed(1)} MB`;
@@ -697,26 +719,46 @@ export function ModelManagement() {
                       </Button>
                     </>
                   ) : freshSelectedModel.downloaded ? (
-                    <Button
-                      size="sm"
-                      onClick={() => {
-                        setModelToDelete({
-                          name: freshSelectedModel.model_name,
-                          displayName: freshSelectedModel.display_name,
-                          sizeMb: freshSelectedModel.size_mb,
-                        });
-                        setDeleteDialogOpen(true);
-                      }}
-                      variant="outline"
-                      disabled={freshSelectedModel.loaded}
-                      title={
-                        freshSelectedModel.loaded ? 'Unload model before deleting' : 'Delete model'
-                      }
-                      className="flex-1"
-                    >
-                      <Trash2 className="h-4 w-4 mr-2" />
-                      {freshSelectedModel.loaded ? 'Unload to Delete' : 'Delete Model'}
-                    </Button>
+                    <div className="flex gap-2 flex-1">
+                      {freshSelectedModel.loaded && (
+                        <Button
+                          size="sm"
+                          onClick={() => unloadMutation.mutate(freshSelectedModel.model_name)}
+                          variant="outline"
+                          disabled={unloadMutation.isPending}
+                          className="flex-1"
+                        >
+                          {unloadMutation.isPending ? (
+                            <Loader2 className="h-4 w-4 mr-2 animate-spin" />
+                          ) : (
+                            <Unplug className="h-4 w-4 mr-2" />
+                          )}
+                          {unloadMutation.isPending ? 'Unloading...' : 'Unload'}
+                        </Button>
+                      )}
+                      <Button
+                        size="sm"
+                        onClick={() => {
+                          setModelToDelete({
+                            name: freshSelectedModel.model_name,
+                            displayName: freshSelectedModel.display_name,
+                            sizeMb: freshSelectedModel.size_mb,
+                          });
+                          setDeleteDialogOpen(true);
+                        }}
+                        variant="outline"
+                        disabled={freshSelectedModel.loaded}
+                        title={
+                          freshSelectedModel.loaded
+                            ? 'Unload model before deleting'
+                            : 'Delete model'
+                        }
+                        className="flex-1"
+                      >
+                        <Trash2 className="h-4 w-4 mr-2" />
+                        Delete Model
+                      </Button>
+                    </div>
                   ) : (
                     <Button
                       size="sm"

app/src/lib/api/client.ts

@@ -337,6 +337,12 @@ class ApiClient {
     });
   }
 
+  async unloadModel(modelName: string): Promise<{ message: string }> {
+    return this.request<{ message: string }>(`/models/${modelName}/unload`, {
+      method: 'POST',
+    });
+  }
+
   async cancelDownload(modelName: string): Promise<{ message: string }> {
     return this.request<{ message: string }>('/models/download/cancel', {
       method: 'POST',

backend/main.py

@@ -1479,7 +1479,7 @@ async def load_model(model_size: str = "1.7B"):
 
 @app.post("/models/unload")
 async def unload_model():
-    """Unload TTS model to free memory."""
+    """Unload the default Qwen TTS model to free memory."""
     try:
         tts.unload_tts_model()
         return {"message": "Model unloaded successfully"}
@@ -1487,6 +1487,68 @@ async def unload_model():
         raise HTTPException(status_code=500, detail=str(e))
 
 
+@app.post("/models/{model_name}/unload")
+async def unload_model_by_name(model_name: str):
+    """Unload a specific model from memory without deleting it from disk."""
+    # Map of model_name -> (model_type, model_size)
+    model_types = {
+        "qwen-tts-1.7B": ("tts", "1.7B"),
+        "qwen-tts-0.6B": ("tts", "0.6B"),
+        "luxtts": ("luxtts", "default"),
+        "chatterbox-tts": ("chatterbox", "default"),
+        "chatterbox-turbo": ("chatterbox_turbo", "default"),
+        "whisper-base": ("whisper", "base"),
+        "whisper-small": ("whisper", "small"),
+        "whisper-medium": ("whisper", "medium"),
+        "whisper-large": ("whisper", "large"),
+        "whisper-turbo": ("whisper", "turbo"),
+    }
+
+    if model_name not in model_types:
+        raise HTTPException(status_code=400, detail=f"Unknown model: {model_name}")
+
+    model_type, model_size = model_types[model_name]
+
+    try:
+        if model_type == "tts":
+            tts_model = tts.get_tts_model()
+            if tts_model.is_loaded() and tts_model.model_size == model_size:
+                tts.unload_tts_model()
+            else:
+                return {"message": f"Model {model_name} is not loaded"}
+        elif model_type == "luxtts":
+            from .backends import get_tts_backend_for_engine
+            backend = get_tts_backend_for_engine("luxtts")
+            if backend.is_loaded():
+                backend.unload_model()
+            else:
+                return {"message": f"Model {model_name} is not loaded"}
+        elif model_type == "chatterbox":
+            from .backends import get_tts_backend_for_engine
+            backend = get_tts_backend_for_engine("chatterbox")
+            if backend.is_loaded():
+                backend.unload_model()
+            else:
+                return {"message": f"Model {model_name} is not loaded"}
+        elif model_type == "chatterbox_turbo":
+            from .backends import get_tts_backend_for_engine
+            backend = get_tts_backend_for_engine("chatterbox_turbo")
+            if backend.is_loaded():
+                backend.unload_model()
+            else:
+                return {"message": f"Model {model_name} is not loaded"}
+        elif model_type == "whisper":
+            whisper_model = transcribe.get_whisper_model()
+            if whisper_model.is_loaded() and whisper_model.model_size == model_size:
+                transcribe.unload_whisper_model()
+            else:
+                return {"message": f"Model {model_name} is not loaded"}
+
+        return {"message": f"Model {model_name} unloaded successfully"}
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
+
 @app.get("/models/progress/{model_name}")
 async def get_model_progress(model_name: str):
     """Get model download progress via Server-Sent Events."""