AutoCAD Plant 3D 2026.2 Update: Python 3.13 Upgrade and Isometric Improvements

AutoCAD Plant 3D 2026.2 includes few changes that developers and integrators should be aware of. The most significant is an upgrade of the embedded Python runtime from Python 3.11 to Python 3.13.11. This update also improves the custom Python script development experience and corrects isometric continuation annotation behavior in certain flange configurations.

Python 3.11 to 3.13.11

Plant 3D 2026 and 2026.1 shipped with Python 3.11. Plant 3D 2026.2 upgrades the embedded runtime to Python 3.13.11 as part of security remediation for the Python package.

During development, the runtime moved through earlier Python 3.13-point releases before settling on 3.13.11 for the 2026.2 release. If you’re validating your installation or building against the embedded runtime, Python 3.13.11 is the version to target.

What developers need to do

If your Plant 3D integration depends on the embedded Python runtime :

• Recompile compiled Python extension modules against the Python 3.13 ABI.
• Review C API usage for functions removed or deprecated between Python 3.11 and 3.13. For example, PyUnicode_AS_UNICODE() and PyUnicode_GET_SIZE() were removed in Python 3.12, while Py_IgnoreEnvironmentFlag is deprecated in Python 3.13.
• Review your Python initialization sequence for changes introduced in Python 3.12 and 3.13.
• Check for dependencies on distutils, which was removed from the Python standard library in Python 3.12.
• Check for hardcoded assumptions about the location of Python configuration headers such as pyconfig.h.
• Regression-test your Python integrations specifically against Plant 3D 2026.2.

For the complete set of Python language and C API changes, review Python’s What’s New in Python 3.12 and What’s New in Python 3.13 documentation.

Improved custom Python script development

Plant 3D 2026.2 also improves the development and debugging experience for custom Python scripts.

When you modify a custom Python script, Plant 3D can now pick up the changes the next time the script runs. You no longer need to restart Plant 3D and reload the ARX module for each script change.

Error reporting has also been improved. When a custom Python script fails, the actual Python traceback is now surfaced instead of a generic error, making it easier to identify and troubleshoot script issues.

Isometric continuation annotation behavior

Plant 3D 2026.2 also corrects continuation annotation behavior in certain flange configurations.

In Plant 3D 2026.1 and earlier, COORD/CONT’D annotations, also referred to as Connected To annotations, could be missing at a flange connection when the flange had effectively zero length between its connection points.

This could occur, for example, with a slip-on flange used as a stub-end or loose flange with no gasket. Although these were commonly reported scenarios, the behavior was related to the underlying open-port detection rather than to a specific flange type or catalog.

In Plant 3D 2026.2, the isometric open-port detection logic has been updated to handle these configurations more consistently across flange types.

What developers need to do

There are no API or interface changes associated with this correction.

If you maintain isometric post-processing, validation, comparison, or QA automation, regression-test it against Plant 3D 2026.2. In particular, re-baseline workflows that may have been designed around the previous missing-annotation behavior.