opencode-diff-preview

OpenCode plugin for Windows permission-time diff preview.

When OpenCode asks for permission to run an edit, this plugin can open a VS Code diff so you can inspect the change before replying.

What it does

• Opens a diff preview for permission.asked on edit
• In the default file preview mode, writes the expected result into the real file first
• Rolls the file back on reject or timeout
• Keeps the file as-is on once or always
• Supports a simpler patch preview mode that shows raw diff content instead of touching the target file
• Removes preview temp files after the permission reply is received

Requirements

• Windows
• OpenCode with plugin support
• VS Code installed
• code CLI available, or Code.exe installed in a standard location

Use in OpenCode

Once the package is published to npm, OpenCode can install and load it automatically through the plugin field in your config.

Edit either:

• ~/.config/opencode/opencode.json
• opencode.json

Then add:

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["opencode-diff-preview"]
}

Restart OpenCode after updating the config.

Recommended config

This plugin reads runtime settings from:

• ~/.config/opencode/diff.jsonc

If the file does not exist, built-in defaults are used.

Recommended minimal config:

{
  "editor": "code",
  "mode": "permission",
  "openOnPermissionAsked": true,
  "permissionPreviewMode": "file",
  "permissionOpenAfterTool": false
}

Preview modes

file

This is the default mode.

When OpenCode asks permission for an edit, the plugin:

1. Applies the expected content to the real file
2. Opens a diff with Original on the left and the real file on the right
3. Rolls the file back on reject or timeout
4. Leaves the file in place on once or always
5. Removes preview temp files after the permission reply is received

OpenCode permission prompts currently reply with once, always, or reject. This plugin treats reject as the deny path.

The diff is for preview only. Manual edits made in the diff view are not part of the supported workflow and may be overwritten or rolled back.

patch

In patch mode, the plugin does not apply the patch to the real file. It opens a diff against generated preview files that contain the patch text, and removes those temp files after the permission reply is received.

Common config fields

• editor: diff editor command, default code
• mode: current default is permission
• openOnPermissionAsked: whether to open preview on permission request
• permissionPreviewMode: file or patch
• tempDir: where preview temp files are stored, config or workspace
• transactionTimeoutMs: rollback timeout in milliseconds, default 120000

Limitations

The current version does not:

• preserve manual edits made in the diff right pane
• support editing inside the preview diff as part of the workflow
• close diff tabs after reply
• provide deep IDE integration beyond launching a diff command

Also note:

• only Windows is supported
• preview handling only applies to edit permissions

Local development

Build:

pnpm install
pnpm build

Pack locally:

pnpm pack