Since the update this morning, I’ve been getting this error frequently. I changed everything to auto, not requesting any web searches or tool calls. I had some prompts work, and some fail. Turned off my MCP servers, same result. LMK how I can help debug
Request ID: eb5fe58e-392a-439d-ba0b-19adec364869
{“error”:“ERROR_HOOKS_BLOCKED”,“details”:{“title”:“Submission blocked by hook”,“detail”:“Hook blocked with message: Hook error: Error: Session initialization failed: 400”,“additionalInfo”:{},“buttons”:,“planChoices”:}}
Hook blocked with message: Hook error: Error: Session initialization failed: 400
Here’s what’s frustrating - I haven’t touched my Claude Code configuration in ages. Nothing changed on my end. The only thing that changed was updating Cursor, and suddenly Composer is completely broken. I can’t submit anything.
What’s even stranger is that I’m not even using Anthropic models right now, but Cursor is still trying to initialize Claude Code hooks and failing. This worked perfectly fine before the update.
I found that disabling the “Rules, Skills, Subagents” setting fixes it, but that feels like a workaround rather than a solution. Why is Cursor now forcing Claude Code initialization even when it’s not being actively used? This seems like something that broke in the recent update.
Can someone from the team look into this? It’s a critical issue for me since I literally cannot use Composer at all right now.
My setup: Cursor 2.4.27, macOS ARM64 (M1), VSCode 1.105.1
You’re only disabling the use of third-party skills (like those in a .claude directory)
You can still use skills and subagents built in/for Cursor (sitting in a .cursor subdirectory). Like that, you shouldn’t be blocked form using Composer, unless I’m missing something!
Yes, disabling that setting does fix the Composer issue, but it’s really just a workaround. The problem is that turning off “Rules, Skills, Subagents” breaks other tools I rely on that use the Claude Code integration. I shouldn’t have to choose between using Composer and having my other workflows function properly.
The real issue here is that something changed in how Cursor handles Claude Code hooks after the update. This configuration was working perfectly fine before, and I haven’t modified anything in my setup. Now suddenly Cursor is failing to initialize these hooks and blocking submissions entirely.
Is there a way to fix the actual hook initialization problem rather than just disabling the feature? Or maybe make the Claude Code integration more resilient so it doesn’t completely break Composer when there’s an issue with session initialization?
It feels like this should either fail gracefully or there should be better error handling so one broken hook doesn’t take down the entire Composer functionality.
I also have claude-mem@thedotmack installed and configured.
So when I disable “Rules, Skills, Subagents” in Cursor settings, these Claude Code hooks and plugins stop working entirely. That’s why I mentioned it breaks my other tools - I need both Composer to work and these Claude Code integrations to function.
I understand this is a new feature in Cursor, but the issue is that after the update, Cursor started trying to initialize these hooks and is failing with the 400 error, which then blocks Composer completely. Before the update, everything was working fine - I could use both Claude Code tools and Cursor without any conflicts.
Is there a way to make the hook initialization more fault-tolerant so that if one hook fails, it doesn’t block the entire Composer functionality?
Agreed that we should look into this! I’ll report it back to the team.
What I’m trying to parse out is what was working for you before this update? Skills and Subagents are both new to v2.4. Were you using Commands/Rules that are now not working when you disable this setting?
