Bug Report: Recurrent Chat Panel Freezes with Tool Timeouts and Memory Leaks in Cursor 1.6.5, and all versions

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1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Bug Report: Recurrent Chat Panel Freezes with Tool Timeouts and Memory Leaks in Cursor 1.6.5

Date: September 12, 2025
Author: Guizmo
Environment: Windows (10/11, specify if possible), Cursor 1.6.5, C#,Python/Unity project with Poetry
Priority: Critical (makes workflow unusable, terminal essential)

Summary

Cursor 1.6.5’s chat panel consistently freezes when using multiple active panels, especially with workflows involving terminal commands (e.g., poetry run <project> validate compilation).
The freezes are caused by:

  • Tool timeouts (notably runTerminalCommandV2Params)
  • Memory leaks (175+ listeners detected)
  • Aborted AI streams (ConnectError: [canceled])

Temporary resets (clear chats, restart Cursor) only help for 5–30 minutes before the issue returns, making terminal-based development workflows impractical.
This bug affects all AI models (Gemini, Claude, GPT) and persists across updates.

Technical Context

  • Cursor Version: 1.6.5 (latest stable as of September 10, 2025)
  • OS: Windows (logs show paths like C:\Users\<user>\...)
  • Project: Anonymous Python CLI (Typer 0.17.4, Poetry) integrated with Unity, using pytest and async services
  • Workflow: Heavy use of terminal commands (poetry run <project> validate compilation) via chat panel Agent mode for code validation/editing
  • Setup: Multiple chat panels (1–2, sometimes detached across monitors), complex prompts mixing Python code + terminal execution
  • AI Models: All affected (Gemini 2.5 Pro, Claude 3.5 Sonnet, GPT-4o)
  • Dependencies: Poetry, pytest, Typer, no VPN/Zscaler detected

Problem Description

Symptoms

  • Panels freeze after 5–20 prompts, especially with terminal commands.
  • With 2+ panels (split or detached), freezes happen almost immediately.
  • Symptoms include:
    • Sudden AI stop (e.g., “Stopped Thinking” or truncated response).
    • No code/diff generation or terminal execution.
    • Developer Tools show repeated errors.

Temporary resets (clear chats, restart Cursor) restore function for 5–30 min, but freezes return faster with multiple panels.

Impact: Since the terminal is central to workflows (e.g., build validation via CLI), Cursor becomes unusable.

Reproduction Steps

  1. Open Cursor 1.6.5 on Windows.
  2. Load a Python project with Poetry (e.g., files like src/cli/commands/validate/cli.py).
  3. Open 2 chat panels (main + detached).
  4. In one panel, run:

Execute `poetry run <project> validate compilation` and validate code in src/cli/commands/validate/cli.py
  1. Repeat similar prompts (edit code + run terminal) 5–10 times.

Result: Panel freezes, AI stops, errors appear in logs.

Errors from Developer Tools

Example logs (Sept 12, 2025):


\[composer] No code block with diff found for URI: file:///c%3A/.../tests/conftest.py
\[composer] No code block with diff found for URI: file:///c%3A/.../src/cli/commands/validate/cli.py
\[ToolV2Service] Error executing tool 15 (runTerminalCommandV2Params): Object
\[ToolV2Service] ToolCallError details: Object
ERR Tool call errored or timed out: Error: Tool call errored or timed out
at AbortSignal.<anonymous> (...)
\[SUMMARIZATION-DEBUG] Stream processing ERROR: ConnectError: \[canceled]
\[017] potential listener LEAK detected, having 175 listeners already.
Error
at p8l.create (...)
at trn.\_event \[as onDidChangeGates] (...)

Error Analysis

  • Composer Errors: "No code block with diff found" → Composer fails to parse AI output or target files (cli.py, conftest.py), triggering retries and overload.
  • ToolV2Service Timeout: runTerminalCommandV2Params (e.g., Poetry commands) times out after ~5–30s, followed by an AbortSignal → AI stream blocked.
  • ConnectError: AI stream canceled due to tool timeout, cutting AI responses.
  • Listener Leak: 175+ listeners accumulate (linked to onDidChangeGates), causing memory leaks and unstable panels. Multi-panels worsen the issue.

Steps Already Tried (No Lasting Fix)

  • Clear All Chats: Temporary improvement (5–30 min).
  • Restart Cursor: Same temporary effect, shorter with multi-panels.
  • Clear Cache: Deleted %APPDATA%\Cursor\Cache and UserData → brief improvement.
  • Simpler Prompts: Fewer tool calls reduce frequency but don’t fix (terminal essential).
  • Incognito/Safe Mode: (cursor --disable-extensions, --incognito) → no difference.
  • API Keys/Quotas: Not related (all models affected).
  • Update: 1.6.5 is latest stable; no improvement from earlier 1.6.x.

Root Cause Hypothesis

A cascading error cycle:

  1. Tool call (runTerminalCommandV2Params) times out (e.g., heavy Poetry commands).
  2. Composer fails to parse diffs → retries triggered.
  3. AI stream aborted (ConnectError: [canceled]).
  4. Each cycle adds listeners (onDidChangeGates) → memory leak (175+).
  5. Multiple panels multiply listeners/queues → guaranteed freezes.

Aggravating Factors:

  • Multiple active panels → focus loss, extra queues.
  • Heavy project (C# + Python + Unity) → large file scans.
  • Windows → Electron socket/thread handling less robust than macOS.
  • Terminal-intensive workflow → Poetry commands exceed timeouts.

Why resets help temporarily: They clear queues/listeners, but accumulation resumes immediately.

Workflow Impact

Terminal usage is central to the workflow (e.g., CLI tests for Unity builds). Freezes:

  • Interrupt code editing/validation.
  • Make chat panels unusable after 5–20 prompts.
  • Force frequent resets → break productivity.
  • Affect all AI models → no workaround by switching providers.

Fix Suggestions for Cursor Team

Tool Timeouts

  • Increase default timeout for runTerminalCommandV2Params (currently ~5–30s).
  • Allow user-configurable timeout (e.g., Settings > Tools > Timeout).
  • Detect slow commands (Poetry) → run async with UI feedback (“Running…”).

Listener Management

  • Add aggressive GC for onDidChangeGates and other listeners.
  • Cap listener count (e.g., max 50) with auto-reset/alert when exceeded.

Multi-Panel Stability

  • Prioritize one active panel for AI streams (disable concurrent queues).
  • Fix focus loss in detached panels (esp. multi-monitor).

Composer Robustness

  • Handle "No code block with diff found" gracefully (avoid infinite retries).
  • Optimize URI/file scanning for large projects (e.g., restrict to open files).

Logs & Diagnostics

  • Provide clearer logs for aborts (reason for ConnectError).
  • Add UI to monitor listener/queue counts in real time.

Additional Information

  • VPN/Zscaler: None used.
  • Logs: Included above (Sept 12, 2025 extract).
  • Screenshots/Videos: Available on request (can record via OBS).
  • Frequency: Near 100% with multi-panels; ~50% with single panel after 10–20 prompts and sommetime less.
  • Workarounds Tried:
    • Disabling tools/composer → reduces frequency but unacceptable (terminal essential).
    • Clearing cache → only temporary.
    • Incognito/Safe mode → no durable effect.

Request to Cursor Team

  • Priority: Critical — makes Cursor unusable for terminal-heavy workflows (CLI/Unity dev).
  • Temporary Fix: Provide a hotfix/beta (e.g., 1.6.6) for timeouts/listener leaks.
  • Configuration Option: Allow increasing tool timeouts or limiting listener counts.
  • Follow-Up: Please confirm receipt and provide ETA for a patch.

:folded_hands: Thanks for your work on Cursor. This bug is a major blocker, but with these details I’m confident you can resolve it quickly.

Steps to Reproduce

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.6.6 (user setup)
VSCode Version: 1.99.3
Commit: 9455eaa4c87f2bad91eda3f2bc9b42b16eae1080
Date: 2025-09-11T01:16:54.096Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26100

For AI issues: which model did you use?

api gemini-2.5-pro

Does this stop you from using Cursor

No - Cursor works, but with this issue

2

Thanks for the detailed bug report! Please update to latest Cursor version and check if you still face these issues. The team has shipped several terminal improvements since 1.6.6 that may resolve the issues you’re experiencing.

If problems persist after updating, please let us know. Thanks!

3

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