Why Claude Code Won't Work in Cursor & How to Fix It | Connection Error Solutions

Table of Contents

• 3 Things to Check First When Claude Won't Work in Cursor
• Steps to Resolve the "IDE is not connected" Error
• What to Do When the Spark Icon or Extension Is Not Displayed
• When Claude Code Won't Work Due to Login or Authentication Errors
• Fixes for Cursor Running Slow, Freezing, or Crashing
• Repairing a Broken PATH After /migrate-installer
• Last Resort When Nothing Else Works
• Summary

3 Things to Check First When Claude Won't Work in Cursor

When you feel like "Claude Code isn't working in Cursor," there are 3 things to confirm before rushing to reinstall. These initial checks will identify the cause in 80% of cases.

1. Whether your version of Cursor is compatible with the Claude Code extension. Cursor updates frequently, and there are occasional periods when the extension hasn't caught up. Check via Help > About and cross-reference the Cursor official Changelog for the supported version for Claude Code integration.
2. The status of the Claude Code extension. Open the Extensions panel with Cmd+Shift+X and confirm that the official Anthropic Claude Code extension shows Enabled. If it says Disabled or Reload Required, enabling it and reloading should fix it.
3. Whether you have a file open in the editor. Cursor has a spec where it does not render the Spark icon when no file is open, so no matter what you do on the Welcome screen, it won't launch. Open any .txt or README file, then check the top-right corner.

If these 3 checks resolve the symptom, you don't need the rest of this article. If the issue persists, proceed to the relevant section by symptom.

Steps to Resolve the "IDE is not connected" Error

The error cursor + claude code: IDE is not connected appears when a bidirectional connection between the Claude Code CLI and Cursor has not been established. Before restarting Cursor, try re-establishing the connection from the CLI side first — this often resolves it in seconds.

Step 1: Run the /ide Command in Claude Code CLI

Launch claude in your terminal and type /ide in the input field after it starts. If Cursor is running, it will be auto-detected and the message Connected to Cursor will appear. This alone often restores the connection without any reinstallation.

Step 2: Relaunch Cursor from the Terminal Using cursor .

When launched via GUI, environment variables and PATH may not be inherited, causing the CLI and Cursor to reference different Claude Code binaries. Running cursor . in your terminal launches Cursor with your shell environment variables inherited, aligning the connection path with the claude command.

Step 3: Manually Install claude-code.vsix

If it still won't connect, the extension itself may be corrupted. Locate claude-code.vsix under ~/.claude/, then use Cursor's Command Palette (Cmd+Shift+P) and select Extensions: Install from VSIX... to load it. The same procedure is introduced as a confirmed solution for IDE integration in a DevelopersIO article by Classmethod (DevelopersIO).

What to Do When the Spark Icon or Extension Is Not Displayed

When the Spark icon (Claude's logo) that should appear in the top-right isn't showing, the most common causes in practice are, in order:

Cause A: No File Is Open

Cursor only displays the Spark icon when there is an active editor tab. It is normal behavior for it to be hidden on the Welcome screen, in an empty workspace, or when the sidebar is fully closed (Carpe Diem). Open any file.

Cause B: The Extension Is Disabled

During Cursor version updates, the Claude Code extension can automatically become Disabled. Click Enable in the Extensions panel and then Reload to refresh it.

Cause C: Extension Cannot Be Found in the Extensions Panel

If Claude Code doesn't appear in Cursor's extension search, you may need to directly obtain the version distributed via the VS Code Marketplace rather than Cursor's marketplace. Downloading the .vsix from the official Anthropic link and installing it manually is the most reliable approach.

Cause D: WSL or Remote SSH Environment

In remote environments, whether you install the extension on the "host side" or the "remote side" changes its behavior. Claude Code must be installed on the remote side, and if it's only on the host side, the Spark icon will not render.

When Claude Code Won't Work Due to Login or Authentication Errors

Authentication issues — such as "Sign in" appearing repeatedly, stopping at ANTHROPIC_API_KEY is not set, or browser authentication not completing — come down to 3 causes.

Cause 1: Environment Variables Are Not Being Inherited

If you've exported ANTHROPIC_API_KEY in your shell but Cursor isn't recognizing it, .zshrc or .bashrc may not be loaded when launching via GUI. Either relaunch Cursor from the terminal with cursor . (see Step 2 under IDE is not connected), or on macOS, use launchctl setenv to pass the value to the GUI session as well.

Cause 2: OAuth Authentication Redirect Failure

If the Anthropic account authentication page doesn't appear in your browser, or it freezes on "waiting for callback" after authentication, a browser popup blocker or extension (such as uBlock Origin) may be interfering. The fastest fix is to retry in a private window.

Cause 3: No Claude Max Plan or Expired Subscription

While basic Claude Code functionality is possible with an API key, a Claude Max plan (monthly subscription) is recommended for greater usage and access to advanced models. If "subscription required" appears when launching claude, an incomplete authentication is also a common cause, so first confirm your authentication status with claude auth. If that doesn't resolve it, check your plan status in the Anthropic console.

Fixes for Cursor Running Slow, Freezing, or Crashing

Cursor getting heavy after extended use, the editor becoming unresponsive, or suddenly crashing — this symptom is primarily caused by memory leaks.

Fix 1: Periodically Clear Terminal History

Claude Code continuously holds terminal history in its context, consuming GB-level memory during long sessions. Clearing the terminal with Cmd+K or resetting the history with /clear in claude will improve things.

Fix 2: Keep Tabs to 10 or Fewer

Cursor includes the contents of open tabs in the AI context, so opening many tabs simultaneously increases both inference costs and memory usage. An aitools-zukan verification article also reports that reducing tab count and splitting long sessions are effective in suppressing crashes (aitools-zukan).

Fix 3: Minimize Extensions

When Cursor's built-in Composer or Tab completion runs simultaneously with the Claude Code extension, memory conflicts make crashes more likely. If you primarily use Claude Code, temporarily disabling Cursor's Tab completion will improve stability (note.com).

Repairing a Broken PATH After /migrate-installer

There are reports of IDE integration breaking immediately after running /migrate-installer in the Claude Code CLI. This happens because the binary location changes after migration, and Cursor continues referencing the old path.

The repair steps are as follows:

1. Run which claude in your terminal to check where it currently points
2. If there is a new path after migration, such as ~/.claude/local/claude, prepend it by running echo 'export PATH="$HOME/.claude/local:$PATH"' >> ~/.zshrc
3. Fully quit Cursor (Cmd+Q) and relaunch it from the terminal with cursor . (see Step 2 under IDE is not connected)
4. In the Claude Code extension settings, overwrite claude.executablePath with the new path

This ensures the CLI and Cursor point to the same binary, restoring IDE integration.

Last Resort When Nothing Else Works

If none of the steps so far have resolved the issue, there are 3 options:

1. Switch to the VS Code Version of Claude Code

Since Cursor and VS Code share the same extension API, you can run Claude Code in VS Code while carrying over your settings. A Zenn verification article reports that the VS Code version has better memory stability and is less prone to crashing during long sessions (Zenn).

2. Complete Uninstall of Cursor and Claude Code → Reinstall

Back up ~/.cursor and ~/.claude, then uninstall both and reinstall them in order: Cursor first, then the Claude Code extension. This is the definitive fix when settings are corrupted.

3. Switch to CLI-Only Operation of Claude Code

Instead of insisting on IDE integration, launching claude from the terminal alone is also a valid option. Using Cursor separately as just an editor, with AI interaction decoupled from the CLI, is a stable approach with fewer failure points, and makes subscription expiration checks and incident response much simpler (Uravation Inc.).

Summary

Symptoms of Claude Code not working in Cursor can always be classified into 5 categories: "connection, display, authentication, crash, and PATH." Before jumping to reinstallation, working through the 5 steps — the /ide command, launching with cursor ., manual VSIX installation, reducing tabs, and PATH repair — will resolve 90% of symptoms that occur in practice. If it still doesn't work, switching to the VS Code version or CLI-only operation is the right call, and not insisting on Cursor will ultimately result in less impact on development speed.

Sources

• How to Fix Claude Code IDE Integration Issues in Cursor | DevelopersIO
• How to Fix Claude Code Running Slow (Cursor) | aitools-zukan
• Workarounds for Claude Code Crashing in Cursor | note papapenpal
• 6 Settings to Make VS Code Claude Code More Usable for Those Switching from Cursor | Zenn
• Claude Code Icon Not Appearing in Cursor | Carpe Diem
• What to Do When Claude Is Unavailable or Unreachable? 3 Steps to Check for Outages | Uravation Inc.