Improve dashboard LLM validation UX and report flow

backend/src/api/routes/storage.py

@@ -144,4 +144,46 @@ async def download_file(
             raise HTTPException(status_code=400, detail=str(e))
 # [/DEF:download_file:Function]
 
+# [DEF:get_file_by_path:Function]
+# @PURPOSE: Retrieve a file by validated absolute/relative path under storage root.
+#
+# @PRE: path must resolve under configured storage root.
+# @POST: Returns a FileResponse for existing files.
+#
+# @PARAM: path (str) - Absolute or storage-root-relative file path.
+# @RETURN: FileResponse - The file content.
+#
+# @RELATION:    CALLS -> StoragePlugin.get_storage_root
+# @RELATION:    CALLS -> StoragePlugin.validate_path
+@router.get("/file")
+async def get_file_by_path(
+    path: str,
+    plugin_loader=Depends(get_plugin_loader),
+    _ = Depends(has_permission("plugin:storage", "READ"))
+):
+    with belief_scope("get_file_by_path"):
+        storage_plugin: StoragePlugin = plugin_loader.get_plugin("storage-manager")
+        if not storage_plugin:
+            raise HTTPException(status_code=500, detail="Storage plugin not loaded")
+
+        requested_path = (path or "").strip()
+        if not requested_path:
+            raise HTTPException(status_code=400, detail="Path is required")
+
+        try:
+            candidate = Path(requested_path)
+            if candidate.is_absolute():
+                abs_path = storage_plugin.validate_path(candidate)
+            else:
+                storage_root = storage_plugin.get_storage_root()
+                abs_path = storage_plugin.validate_path(storage_root / candidate)
+        except ValueError as e:
+            raise HTTPException(status_code=400, detail=str(e))
+
+        if not abs_path.exists() or not abs_path.is_file():
+            raise HTTPException(status_code=404, detail="File not found")
+
+        return FileResponse(path=str(abs_path), filename=abs_path.name)
+# [/DEF:get_file_by_path:Function]
+
 # [/DEF:storage_routes:Module]