During March 2026, this developer focused on improving training stability for the volcengine/verl repository by addressing a recurring tensor shape mismatch in VLM SFT training under FSDP with DatasetPadMode.NO_PADDING. They replaced the use of NestedTensor .values() with a combination of unbind and cat operations, ensuring correct handling of 3D position_ids across varying micro-batch scenarios. Working primarily in Python and leveraging advanced PyTorch tensor manipulation, the developer validated the fix through comprehensive testing. Their disciplined approach resulted in a robust internal solution that enhanced model training reliability without altering the public API, demonstrating depth in data processing and machine learning.