[EW] Agent: empty chat message

This session is empty, we need to understand why: https://mystique-langfuse-prod.corp.ethos117-prod-va6.ethos.adobe.net/project/cmn60m68c00088702ko6novs5/traces/5c9dc41a686d0ab833640a74d6af90a7?timestamp=2026-08-04T20:54:25.608Z

Open the linked Langfuse trace and inspect the session and agent execution details around the empty chat message. Trace the relevant request through the project to identify where the empty message is produced, then reproduce the failure and verify that the resulting session contains the expected chat content.

Written by the indexing model from the issue text.