Cursor freeze, crash while rendering response from tool calls

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Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

The 2.6.x and 2.5.x versions keep crashing and freezing while rendering longer markdown-like responses from tool calls.

Steps to Reproduce

  1. Do query like this: XXX tool: ‘YYY’ - use this tool to get information how to … . Do several queries in parallel with Composer
  2. In 70% after received tool responses (for 4-5 tool calls), the Cursor freeze. You need to wait 1-5min to become responsible and start working again.
  3. Next close Cursor with the chat visible and open it again. It will start with the last project with chat open and here it become unresponsive/freeze for couple of minutes. Then unfreeze
    Starting new Chat, again freeze Cursor.

Also:

  1. I ran my prompt on version 2.4.37 — conversation ID: b383d9a8-22ca-4787-95da-41316c86c0b12.
  2. Upgraded to the newest version 2.6.14.

When the cursor restarted with the conversation, it froze.
I have 100% scenario to reproduce the freeze.

Expected Behavior

No freezing, the 2.4.37 version does not have such problems

Operating System

Linux

Version Information

2.5.x, 2.6.x, 2.7 (Nightly)

For AI issues: add Request ID with privacy disabled

b383d9a8-22ca-4787-95da-41316c86c0b12

Additional Information

2.4.37 version works

Does this stop you from using Cursor

Yes - Cursor is unusable

2 Likes
4

Hey, this is a known issue. The chat markdown renderer can hang on a regex when it processes large responses from MCP tool calls. The team knows about it, but there’s no fix yet.

Your report matches this exactly: Window becomes unresponsive and reloads when MCP tool returns large response. That thread has a full root cause analysis.

As a temporary workaround, try limiting the size of responses from MCP tools. For example, if your MCP server supports pagination or truncation, use those. You can also add a rule so the agent requests data in smaller chunks instead of one big request.

I’ll let the team know it reproduces on Linux too and that it’s blocking work. That should help with prioritization.

5

A post was merged into an existing topic: Window becomes unresponsive and reloads when MCP tool returns large response (markdown lexer regex hang)