Hi I am using ROS2 humble with moveit2. I created a configuration with setup_assistant of moveit2. However, when I try to launch the demo launch file created by it. It gaves me the error:

[ERROR] [launch]: Caught exception in launch (see debug for traceback): 'capabilities'

I could not find anything related to capabilities. What does it mean? May someone please help me?


2 Answers 2


From what it looks like, this is a known issue for Humble. You will find more discussion on this thread.


I don't know if this is going to solve your issue, but I'm taking a shot in the dark regardless. I checked the recent pull requests for MoveIt2, and someone has sent in a PR which might correspond to what you want. Here is the PR in question.

From what I suspect, there is some misdefinition of the default value of the "capabilities" launch argument, which the PR aims to fix by declaring proper default argument. You may try this out to see if that fixes your issue.

  • $\begingroup$ Then can I ask you what is the best consistent version of Ros2 for moveit2, gazebo and rviz? $\endgroup$ Mar 21 at 9:35
  • $\begingroup$ I have changed my ros2 dist to iron and I still got the same error? $\endgroup$ Mar 22 at 9:28
  • $\begingroup$ Hi, I have found a PR that might be helpful to you. This seems to have been an issue with backporting - I suspect that with Rolling, you would not get this error. I've updated my answer to include more info, I'll let you follow up with the PR in question to see if that can solve your problem. $\endgroup$
    – ssarkar
    Mar 22 at 10:16

I found the solution thanks to @ssarkar. What you should do to fix this error is first you need to open the file called launches.py and go to line 203. To simply do it run the ros2 launch command with --debug.

After opening it you need to reverse commit the changes mentioned here. What I mean is copy,

ld.add_action(DeclareLaunchArgument("capabilities", default_value=""))

and then paste it instead of


After that save the file with ctrl+s and then rebuild you colcon space. Done.


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