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Troubleshooting

Add-In Failed To Load (crash logs)​

When the add-in fails during host startup, RevitDevTool writes a one-shot crash log before the panel appears:

%APPDATA%\RevitDevTool\{Year}\Logs\crash_{app}_{ver}_{pid}.log

Example (Revit 2025, PID 12345):

%APPDATA%\RevitDevTool\2025\Logs\crash_Revit_2025_12345.log

Check this file first when the ribbon tab is missing, MCP lists no hosts after a rebuild, or pytest cannot connect immediately after launch.

Rolling session logs use the log_* pattern in the same folder. AutoClean removes log_* only — crash_* files are kept.

Build Configuration Not Found​

Use .slnx and Autodesk configuration names:

dotnet build RevitDevTool.slnx -c "Debug.Autodesk.2025"

Do not use old names like Release R25. Available configurations: Debug.Autodesk.2022 through Debug.Autodesk.2027 and Release.Autodesk.2022 through Release.Autodesk.2027.

Python Dependencies Do Not Install​

Check:

  • Pixi can run on the machine (enterprise policy may block third-party executables)
  • %APPDATA%\RevitDevTool\pixi-env is writable
  • On Plant 3D only: uv can run, and %APPDATA%\RevitDevTool\uv-env\{major.minor} is writable
  • Package indexes are reachable (conda-forge + PyPI for Pixi; PyPI for the Plant 3D uv sidecar)
  • PEP 723 # /// script block is present and valid at the top of the script

If both managers are blocked, confirm pyRevit is installed for pip/pyRevit CPython fallback.

Python Debugger Does Not Attach​

Check:

  • VSCode is listening on the configured port
  • The RevitDevTool debugger port matches VSCode
  • debugpy is installed in the active Python environment (Pixi env, Plant 3D uv sidecar, or fallback)
  • Firewall/security policy allows local attach

pytest Cannot Connect​

Check:

  1. The host (Revit, AutoCAD, or Civil 3D) is running with RevitDevTool loaded
  2. host_name and host_version in pyproject.toml match the running instance
  3. Try uv run pytest --force-launch --host-version 2025 -v
  4. If the add-in failed to load, read the newest startup log (see above)

IronPython tests (test_*_ipy.py) use unittest semantics and do not use PEP 723 dependencies. On Revit they prefer the pyRevit engine when it is installed.

Geometry Does Not Display (Revit)​

Check:

  • The active view supports DirectContext3D rendering
  • Visualization is enabled in settings
  • The traced object is a supported Revit geometry type
  • The geometry is within visible view range
  • The script printed the actual geometry object, not just a string representation

AI Client Cannot Find Hosts​

Check:

  • At least one host instance is running with RevitDevTool loaded
  • .NET 10 runtime is installed
  • If hosts disappeared after a rebuild, read the newest crash_* log before assuming the MCP server failed

MCP client config should follow the installation instructions for your client and point to the RevitDevTool MCP server.

MCP Server Logs​

The stdio MCP server writes to:

%APPDATA%\RevitDevTool\logs\

Useful when the AI client times out or list_host_instances returns empty.