OpenCode Desktop starts multiple windows when launched once from a script

[andrey-golovko]

Summary

OpenCode Desktop can start multiple Desktop windows and multiple backend instances when it is launched once from a script.

This happens without:

• double-clicking
• running the script multiple times
• hotkeys
• parallel execution

The script starts OpenCode.exe exactly once, yet multiple Desktop windows appear.

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Environment

• OS: Windows 10 / Windows 11
• OpenCode Desktop: latest Windows build
• Installation paths:

  %LOCALAPPDATA%\OpenCode\OpenCode.exe
  %LOCALAPPDATA%\OpenCode\opencode-cli.exe
  

• Launch method:
  • PowerShell script
• Script execution count:
  • once

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Steps to Reproduce (single run)

1. Create a PowerShell script with a single launch command:

   & "$env:LOCALAPPDATA\OpenCode\OpenCode.exe" "C:\project"
   

2. Run the script once from PowerShell.

3. Observe that multiple OpenCode Desktop windows may open.

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Observed Behavior

• More than one Desktop window is shown.

• Process list contains multiple instances:

  OpenCode.exe
  OpenCode.exe
  

• Multiple backend instances are spawned:

  opencode-cli.exe serve --port=64840
  opencode-cli.exe serve --port=64854
  opencode-cli.exe serve --port=64870
  

• The script itself launches OpenCode.exe only once.

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Expected Behavior

• A single script execution should result in:
  • exactly one Desktop window
  • exactly one backend instance

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Analysis / Findings

Investigation shows that OpenCode Desktop appears to re-launch or self-spawn during startup.

Indicators:

• Multiple OpenCode.exe processes exist even though the parent script started it once.
• At least one OpenCode.exe instance has another OpenCode.exe as its parent.
• Desktop seems to perform an internal restart / re-exec (possibly for setup, update, or backend initialization), but the original instance does not exit.

This results in multiple UI windows instead of a clean handoff.

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Why This Is a Bug

Even if Desktop needs to restart itself internally:

• the original instance should exit, or
• the new instance should take over,

but multiple visible Desktop windows must not remain active.

Single-instance behavior should be enforced inside the application, not in user scripts.

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Workaround

Users must implement a global OS-level mutex in their launcher scripts, for example:

$mutex = New-Object System.Threading.Mutex($false, "Global\OpenCodeDesktopSingleton")
if (-not $mutex.WaitOne(0)) { exit }

This workaround prevents the issue, confirming that the problem is related to missing single-instance protection in Desktop.

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Proposed Fix

Implement a single-instance guard inside OpenCode Desktop:

• Use a global named mutex on Windows (e.g. Global\OpenCodeDesktop)
• On detecting an existing instance:
  • bring the existing window to foreground
  • exit immediately

This is standard behavior for IDEs and desktop developer tools.

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Impact

• Confusing user experience (multiple windows from one launch)
• Difficult automation and scripting
• Backend and MCP duplication
• Unnecessary resource usage

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Additional Notes

• The issue reproduces without any bootstrap backend.
• The issue reproduces without proxy configuration.
• The issue is not caused by user double-clicking or concurrent launches.