fix(frontend): Improve error handling for invalid agent files (#11165)

### Changes 🏗️

<img width="672" height="761" alt="Screenshot 2025-10-14 at 16 12 50"
src="https://github.com/user-attachments/assets/9e664ade-10fe-4c09-af10-b26d10dca360"
/>


Fixes
[BUILDER-3YG](https://sentry.io/organizations/significant-gravitas/issues/6942679655/).
The issue was that: User uploaded an incompatible external agent persona
file lacking required flow graph keys (`nodes`, `links`).

- Improves error handling when an invalid agent file is uploaded.
- Provides a more user-friendly error message indicating the file must
be a valid agent.json file exported from the AutoGPT platform.
- Clears the invalid file from the form and resets the agent object to
null.

This fix was generated by Seer in Sentry, triggered by Toran Bruce
Richards. 👁️ Run ID: 1943626

Not quite right? [Click here to continue debugging with
Seer.](https://sentry.io/organizations/significant-gravitas/issues/6942679655/?seerDrawer=true)

### Checklist 📋

#### For code changes:
- [x] I have clearly listed my changes in the PR description
- [x] I have made a test plan
- [x] I have tested my changes according to the test plan:
  <!-- Put your test plan here: -->
- [x] Test that uploading an invalid agent file (e.g., missing `nodes`
or `links`) triggers the improved error handling and displays the
user-friendly error message.
- [x] Verify that the invalid file is cleared from the form after the
error, and the agent object is reset to null.

---------

Co-authored-by: seer-by-sentry[bot] <157164994+seer-by-sentry[bot]@users.noreply.github.com>
Co-authored-by: Swifty <craigswift13@gmail.com>
Co-authored-by: Lluis Agusti <hi@llu.lu>

autogpt_platform/frontend/src/app/(platform)/library/components/LibraryUploadAgentDialog/useLibraryUploadAgentDialog.ts

@@ -82,7 +82,7 @@ export const useLibraryUploadAgentDialog = () => {
           )
         ) {
           throw new Error(
-            "Invalid agent object in file: " + JSON.stringify(obj, null, 2),
+            "Invalid agent file. Please upload a valid agent.json file that has been previously exported from the AutoGPT platform. The file must contain the required fields: name, description, nodes, and links.",
           );
         }
         const agent = obj as Graph;
@@ -96,6 +96,17 @@ export const useLibraryUploadAgentDialog = () => {
         }
       } catch (error) {
         console.error("Error loading agent file:", error);
+
+        toast({
+          title: "Invalid Agent File",
+          description:
+            "Please upload a valid agent.json file that has been previously exported from the AutoGPT platform. The file must contain the required fields: name, description, nodes, and links.",
+          duration: 5000,
+          variant: "destructive",
+        });
+
+        form.resetField("agentFile");
+        setAgentObject(null);
       }
     };
     reader.readAsText(file);