Agent builder shows nothing when Create Agent returns 422 — validation errors are never rendered

[TonsOfFun]

Submitting the agent builder form returns 422 and the UI shows nothing — no error banner, no field-level messages. The form simply does not advance, so there is no way to tell what was rejected.

The controller does return the validation errors; they are just never rendered.

Reproduce

1. Open the agent builder ("New Agent") in the dashboard.
2. Fill in the form and submit.
3. Observe POST /api/agents → 422 in the network tab, with an errors payload in the response body.
4. The UI stays on the form with no indication of a problem.

Evidence

Posting the equivalent payload directly to the API succeeds:

POST /api/agents  → 201 Created

So the endpoint works; the failure is specific to what the builder submits, and the 422 body explains it — but only to someone reading the network tab.

Expected

Render the 422 errors from the response: a summary at the form level, and field-level messages where the errors map to fields.

Note

Observed on the claude/mcp-tool-execution branch during evaluation work. I did not trace which field was rejected or why the builder's payload differs from the working direct POST — this issue is about the silent failure, which stands regardless of the underlying validation.