Bug: Opening files with IntelliJ IDEA fails with DirectoryLock CannotActivateException

Description

I previously suggested adding support for opening files directly with local IDEs (such as IntelliJ IDEA and other applications). I noticed this capability has now been added, which is a very useful improvement.

However, when using Codex to open a file with IntelliJ IDEA on Windows, IntelliJ fails to start.

Error

IntelliJ IDEA shows:

Start Failed

Internal error

com.intellij.platform.ide.bootstrap.DirectoryLock$CannotActivateException:
Process "C:\Program Files\JetBrains\IntelliJ IDEA 2026.1.3\bin\idea64.exe" is still running and does not respond.

Screenshot attached in the original report.

Expected behavior

• Codex launches IntelliJ IDEA successfully.
• The selected file/project opens in the IDE.

Actual behavior

• IntelliJ IDEA startup fails.
• The file cannot be opened through the IDE integration.

Environment

• OS: Windows
• IDE: IntelliJ IDEA 2026.1.3
• Feature: Codex open file with external application / IDE integration

Possible cause

It looks like the launcher may start IDEA while an existing IDEA process or stale lock is detected, triggering IntelliJ's DirectoryLock protection.

Possible improvements:

• Detect an existing IntelliJ process before launching.
• Reuse an existing IDE instance when possible.
• Wait for IDE startup before sending the open-file command.
• Handle stale IDE locks/process states more gracefully.

Thank you for adding this feature. It will be very useful once this issue is resolved.