fix(chat): handle empty uploaded files case and improve artifact selection logic (#979)

* fix(chat): handle empty uploaded files case and improve artifact selection logic

* Update frontend/src/components/workspace/chats/chat-box.tsx

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix: address code review suggestions from PR #979 (#3)

* Initial plan

* fix: address PR #979 review suggestions

- utils.ts: scope (empty) check inside <uploaded_files> tag content
- chat-box.tsx: remove stale `artifacts` from useEffect deps
- context.tsx: wrap select/deselect with useCallback for stable refs
- test: add test_empty_new_files_produces_empty_marker

Co-authored-by: foreleven <4785594+foreleven@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: foreleven <4785594+foreleven@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com>
Co-authored-by: foreleven <4785594+foreleven@users.noreply.github.com>

backend/src/agents/middlewares/uploads_middleware.py

@@ -53,12 +53,15 @@ class UploadsMiddleware(AgentMiddleware[UploadsMiddlewareState]):
 
         lines.append("The following files were uploaded in this message:")
         lines.append("")
-        for file in new_files:
+        if new_files:
-            size_kb = file["size"] / 1024
+            for file in new_files:
-            size_str = f"{size_kb:.1f} KB" if size_kb < 1024 else f"{size_kb / 1024:.1f} MB"
+                size_kb = file["size"] / 1024
-            lines.append(f"- {file['filename']} ({size_str})")
+                size_str = f"{size_kb:.1f} KB" if size_kb < 1024 else f"{size_kb / 1024:.1f} MB"
-            lines.append(f"  Path: {file['path']}")
+                lines.append(f"- {file['filename']} ({size_str})")
-            lines.append("")
+                lines.append(f"  Path: {file['path']}")
+                lines.append("")
+        else:
+            lines.append("(empty)")
 
         if historical_files:
             lines.append("The following files were uploaded in previous messages and are still available:")

backend/tests/test_uploads_middleware_core_logic.py

@@ -188,6 +188,13 @@ class TestCreateFilesMessage:
         msg = mw._create_files_message([self._new_file()], [])
         assert "read_file" in msg
 
+    def test_empty_new_files_produces_empty_marker(self, tmp_path):
+        mw = _middleware(tmp_path)
+        msg = mw._create_files_message([], [])
+        assert "(empty)" in msg
+        assert "<uploaded_files>" in msg
+        assert "</uploaded_files>" in msg
+
 
 # ---------------------------------------------------------------------------
 # before_agent

frontend/src/components/workspace/artifacts/context.tsx

@@ -1,4 +1,10 @@
-import { createContext, useContext, useState, type ReactNode } from "react";
+import {
+  createContext,
+  useCallback,
+  useContext,
+  useState,
+  type ReactNode,
+} from "react";
 
 import { useSidebar } from "@/components/ui/sidebar";
 import { env } from "@/env";
@@ -35,20 +41,23 @@ export function ArtifactsProvider({ children }: ArtifactsProviderProps) {
   const [autoOpen, setAutoOpen] = useState(true);
   const { setOpen: setSidebarOpen } = useSidebar();
 
-  const select = (artifact: string, autoSelect = false) => {
+  const select = useCallback(
-    setSelectedArtifact(artifact);
+    (artifact: string, autoSelect = false) => {
-    if (env.NEXT_PUBLIC_STATIC_WEBSITE_ONLY !== "true") {
+      setSelectedArtifact(artifact);
-      setSidebarOpen(false);
+      if (env.NEXT_PUBLIC_STATIC_WEBSITE_ONLY !== "true") {
-    }
+        setSidebarOpen(false);
-    if (!autoSelect) {
+      }
-      setAutoSelect(false);
+      if (!autoSelect) {
-    }
+        setAutoSelect(false);
-  };
+      }
+    },
+    [setSidebarOpen, setSelectedArtifact, setAutoSelect],
+  );
 
-  const deselect = () => {
+  const deselect = useCallback(() => {
     setSelectedArtifact(null);
     setAutoSelect(true);
-  };
+  }, []);
 
   const value: ArtifactsContextType = {
     artifacts,

frontend/src/components/workspace/chats/chat-box.tsx

@@ -34,12 +34,19 @@ const ChatBox: React.FC<{ children: React.ReactNode; threadId: string }> = ({
     setOpen: setArtifactsOpen,
     setArtifacts,
     select: selectArtifact,
+    deselect,
     selectedArtifact,
   } = useArtifacts();
 
   const [autoSelectFirstArtifact, setAutoSelectFirstArtifact] = useState(true);
   useEffect(() => {
     setArtifacts(thread.values.artifacts);
+    if (
+      thread.values.artifacts?.length === 0 ||
+      (selectedArtifact && !thread.values.artifacts?.includes(selectedArtifact))
+    ) {
+      deselect();
+    }
     if (
       env.NEXT_PUBLIC_STATIC_WEBSITE_ONLY === "true" &&
       autoSelectFirstArtifact
@@ -51,7 +58,9 @@ const ChatBox: React.FC<{ children: React.ReactNode; threadId: string }> = ({
     }
   }, [
     autoSelectFirstArtifact,
+    deselect,
     selectArtifact,
+    selectedArtifact,
     setArtifacts,
     thread.values.artifacts,
   ]);

frontend/src/core/messages/utils.ts

@@ -300,6 +300,11 @@ export function parseUploadedFiles(content: string): FileInMessage[] {
     return [];
   }
 
+  // Check if the backend reported no new files were uploaded in this message
+  if (uploadedFilesContent?.includes("(empty)")) {
+    return [];
+  }
+
   // Parse file list
   // Format: - filename (size)\n  Path: /path/to/file
   const fileRegex = /- ([^\n(]+)\s*\(([^)]+)\)\s*\n\s*Path:\s*([^\n]+)/g;