fix upload file size contract (#3408)

backend/app/gateway/routers/uploads.py

@@ -39,15 +39,39 @@ DEFAULT_MAX_FILE_SIZE = 50 * 1024 * 1024
 DEFAULT_MAX_TOTAL_SIZE = 100 * 1024 * 1024
 
 
+class UploadedFileInfo(BaseModel):
+    """Uploaded file metadata exposed by upload and list APIs."""
+
+    filename: str
+    size: int
+    path: str
+    virtual_path: str
+    artifact_url: str
+    extension: str | None = None
+    modified: float | None = None
+    original_filename: str | None = None
+    markdown_file: str | None = None
+    markdown_path: str | None = None
+    markdown_virtual_path: str | None = None
+    markdown_artifact_url: str | None = None
+
+
 class UploadResponse(BaseModel):
     """Response model for file upload."""
 
     success: bool
-    files: list[dict[str, str]]
+    files: list[UploadedFileInfo]
     message: str
     skipped_files: list[str] = Field(default_factory=list)
 
 
+class UploadListResponse(BaseModel):
+    """Response model for uploaded file listing."""
+
+    files: list[UploadedFileInfo]
+    count: int
+
+
 class UploadLimits(BaseModel):
     """Application-level upload limits exposed to clients."""
 
@@ -256,7 +280,7 @@ async def upload_files(
 
             file_info = {
                 "filename": safe_filename,
-                "size": str(file_size),
+                "size": file_size,
                 "path": str(sandbox_uploads / safe_filename),
                 "virtual_path": virtual_path,
                 "artifact_url": upload_artifact_url(thread_id, safe_filename),
@@ -333,9 +357,9 @@ async def get_upload_limits(
     return _get_upload_limits(config)
 
 
-@router.get("/list", response_model=dict)
+@router.get("/list", response_model=UploadListResponse)
 @require_permission("threads", "read", owner_check=True)
-async def list_uploaded_files(thread_id: str, request: Request) -> dict:
+async def list_uploaded_files(thread_id: str, request: Request) -> UploadListResponse:
     """List all files in a thread's uploads directory."""
     try:
         uploads_dir = get_uploads_dir(thread_id)
@@ -349,7 +373,7 @@ async def list_uploaded_files(thread_id: str, request: Request) -> dict:
     for f in result["files"]:
         f["path"] = str(sandbox_uploads / f["filename"])
 
-    return result
+    return UploadListResponse(**result)
 
 
 @router.delete("/{filename}")