# In Cursor: Settings > Features > AI # Disable: Cursor Tab, AI Autocomplete, Auto-apply # Then restart Claude Code claude Disable Cursor’s AI editing features while using Claude Code CLI. Use Cursor purely as a text editor (it is a VS Code fork and works fine without AI). Alternat...

Cursor Conflict With Claude Code CLI (2026)

Q: Prevention

# CLAUDE.md rule When using Claude Code CLI, disable all competing AI editors (Cursor AI, GitHub Copilot inline edits). Only one AI agent should modify files at a time. Use Claude Code in an external terminal if running alongside Cursor.

Last updated: April 20, 2026

The Error

Error: File 'src/app.tsx' was modified externally during Claude Code edit
  Cursor AI applied an edit to the same file simultaneously
  Edit tool string match failed — file contents changed between read and write
  Conflict between Cursor Tab completion and Claude Code Write tool

This appears when both Cursor’s built-in AI and Claude Code CLI try to edit the same file at the same time, causing Claude Code’s exact-match edit to fail.

The Fix

# In Cursor: Settings > Features > AI
# Disable: Cursor Tab, AI Autocomplete, Auto-apply
# Then restart Claude Code
claude

Disable Cursor’s AI editing features while using Claude Code CLI.
Use Cursor purely as a text editor (it is a VS Code fork and works fine without AI).
Alternatively, run Claude Code in a separate terminal window outside Cursor.

Why This Happens

Cursor and Claude Code both modify files on disk. Claude Code’s Edit tool reads a file, matches a specific string, and writes the replacement. If Cursor’s AI autocomplete or tab completion modifies the file between Claude Code’s read and write, the exact string match fails because the file content changed. Both tools are race-conditioning on the same file system resource without coordination.

If That Doesn’t Work

Run Claude Code in an external terminal instead of Cursor’s integrated terminal:

# Open iTerm2 or Terminal.app separately
cd /path/to/project
claude

Use VS Code instead of Cursor for Claude Code integration:

code .
# VS Code does not have competing AI edit features by default

Lock files before editing to prevent concurrent modifications:

claude "Before editing any file, verify it has not been modified in the last 5 seconds"

Prevention

# CLAUDE.md rule
When using Claude Code CLI, disable all competing AI editors (Cursor AI, GitHub Copilot inline edits). Only one AI agent should modify files at a time. Use Claude Code in an external terminal if running alongside Cursor.

This fix also applies if you see variations of this error:

Connection or process errors with similar root causes in the same subsystem
Timeout variants where the operation starts but does not complete
Permission variants where access is denied to the same resource
Configuration variants where the same setting is missing or malformed

If your specific error message differs slightly from the one shown above, the fix is likely the same. The key indicator is the operation that failed (shown in the stack trace) rather than the exact wording of the message.

Frequently Asked Questions

Does this error affect all operating systems?

This error can occur on macOS, Linux, and Windows (WSL). The exact error message may differ slightly between platforms, but the root cause and fix are the same. macOS users may see additional Gatekeeper or notarization prompts. Linux users should check that the relevant system packages are installed. Windows users should ensure they are running inside WSL2, not native Windows.

Will this error come back after updating Claude Code?

Updates can occasionally reintroduce this error if the update changes default configurations or dependency requirements. After updating Claude Code, verify your project still builds and runs correctly. If the error returns, reapply the fix and check the changelog for breaking changes.

Can this error cause data loss?

No, this error occurs before or during an operation and does not corrupt existing files. Claude Code’s edit operations are atomic — they either complete fully or not at all. However, if the error occurs during a multi-step operation, you may have partial changes that need to be reviewed with git diff before continuing.

How do I report this error to Anthropic if the fix does not work?

Open an issue at github.com/anthropics/claude-code with: (1) the full error message including stack trace, (2) your Node.js version (node --version), (3) your Claude Code version (claude --version), (4) your operating system and version, and (5) the command or operation that triggered the error.

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