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:
-            size_kb = file["size"] / 1024
-            size_str = f"{size_kb:.1f} KB" if size_kb < 1024 else f"{size_kb / 1024:.1f} MB"
-            lines.append(f"- {file['filename']} ({size_str})")
-            lines.append(f"  Path: {file['path']}")
-            lines.append("")
+        if new_files:
+            for file in new_files:
+                size_kb = file["size"] / 1024
+                size_str = f"{size_kb:.1f} KB" if size_kb < 1024 else f"{size_kb / 1024:.1f} MB"
+                lines.append(f"- {file['filename']} ({size_str})")
+                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