kit初版，模型引入,agent优化

art-agent/backend/app/api/chat.py

@@ -7,6 +7,7 @@ from fastapi import APIRouter, File, Form, UploadFile
 from sse_starlette.sse import EventSourceResponse
 
 from app.agent.loop import run_agent_loop
+from app.config import get_image_models_list, get_default_image_model_id
 
 router = APIRouter()
 
@@ -23,26 +24,56 @@ async def _save_upload(file: UploadFile) -> str:
     return f"/uploads/{filename}"
 
 
+@router.post("/upload-ref-image")
+async def upload_ref_image(
+    file: UploadFile = File(...),
+):
+    """
+    独立的参考图上传端点。
+    前端选图后立即调用，返回服务端路径，供后续发消息时引用。
+    """
+    UPLOADS_DIR.mkdir(parents=True, exist_ok=True)
+    url = await _save_upload(file)
+    return {"url": url, "filename": file.filename}
+
+
+@router.get("/models")
+async def list_models():
+    """返回可用的图像生成模型列表。"""
+    return {
+        "models": get_image_models_list(),
+        "default": get_default_image_model_id(),
+    }
+
+
 @router.post("/chat")
 async def chat(
     messages: str = Form(...),
     ref_image: Optional[UploadFile] = File(None),
+    ref_image_url: Optional[str] = Form(None),
+    image_model: Optional[str] = Form(None),
 ):
     """
     主对话端点。
 
     参数：
     - messages: JSON 字符串，对话历史 [{role, content}]
-    - ref_image: 可选的参考图文件
+    - ref_image: 可选的参考图文件（兼容旧方式）
+    - ref_image_url: 可选，已通过 /upload-ref-image 上传后的服务端路径
+    - image_model: 可选，指定本次使用的生图模型短 ID
     """
     parsed_messages = json.loads(messages)
 
-    ref_image_url: Optional[str] = None
-    if ref_image and ref_image.filename:
-        ref_image_url = await _save_upload(ref_image)
+    resolved_ref_url: Optional[str] = None
+    if ref_image_url:
+        resolved_ref_url = ref_image_url
+    elif ref_image and ref_image.filename:
+        resolved_ref_url = await _save_upload(ref_image)
 
     async def event_generator():
-        async for event in run_agent_loop(parsed_messages, ref_image_url):
+        async for event in run_agent_loop(
+            parsed_messages, resolved_ref_url, image_model=image_model
+        ):
             yield {
                 "event": event["type"],
                 "data": json.dumps(event["data"], ensure_ascii=False),