Attaching a Skill into a message breaks any models ability to connect to the server. All subsequent messages in the chat are errors. Workaround = prompting ‘Run the skill called X to do Y, for Z…’. omitting ‘/’ followed by the Skill name.
Error also occurs if in mid conversation, and agent offers to load X Skill, then all subsequent requests are errors.
Possibility of error being caused by Skills with over x amount of lines.
Thanks for the report and the screenshot. What you’re seeing isn’t intended, and it isn’t caused by anything in your setup.
When a skill is attached to a message (with /, or when you accept an offer to load one), Cursor reads the YAML frontmatter at the top of that skill’s SKILL.md. If that frontmatter isn’t valid YAML, the request fails with a generic server error. Later messages in the same chat keep failing because the skill stays attached. Skill length is not the trigger.
To unblock the chat, open the SKILL.md for the skill you attached and check the block between the --- markers. It should match the format in the skills docs:
---
name: my-skill
description: "Short description of what this skill does and when to use it."
---
A few things that commonly break the parse:
An unquoted description that contains a colon
Markdown headings or list markers inside the frontmatter block
A --- line at the top of the file followed by markdown (the parser treats that markdown as frontmatter)
After you fix or temporarily remove that skill, sending again in the same chat should work. The workaround you found (asking the agent to run the skill by name, without attaching it with /) is also fine.
We’ve let the team know and this is an issue we’re tracking. I’ll post here when there’s an update.
