The Challenge of APDL Automation

APDL (ANSYS Parametric Design Language) is a powerful but rigid scripting environment used in computational engineering. Automating it with general-purpose LLMs often fails because these models struggle with the specific syntax, state-dependent commands, and error-handling requirements of engineering simulation software. CAX-Agent addresses this by providing a dedicated harness that bridges the gap between high-level intent and low-level APDL execution.

The CAX-Agent Architecture

CAX-Agent functions as a lightweight middleware layer that constrains the agent's action space to valid APDL operations. Instead of allowing an LLM to generate raw, unverified scripts, the framework:

• Constrains Execution: It forces the agent to interact with the simulation environment through a predefined set of verified functions rather than open-ended code generation.
• Error Feedback Loops: When a simulation fails, the harness captures the specific APDL error logs and feeds them back into the agent's context, allowing for iterative self-correction.
• State Management: It maintains the simulation state, ensuring that the agent understands the current geometry and mesh status before issuing subsequent commands.

Improving Reliability in Engineering Workflows

By shifting from a 'generate-and-pray' approach to a 'harness-and-verify' model, CAX-Agent significantly reduces the hallucination rate common in engineering automation. The framework is designed to be lightweight, meaning it does not require massive fine-tuning of base models. Instead, it relies on prompt engineering combined with a robust execution environment that treats APDL as a structured API. This approach allows engineers to automate complex simulation setups—such as parametric sweeps or iterative design optimization—with higher success rates and less manual debugging.