opencode-fastedit

A high-performance line-based editing plugin for OpenCode that replaces ranges of lines by line number instead of requiring exact string matching.

Features

• Line-number based editing - Specify start and end line numbers instead of matching exact text
• Efficient multi-line edits - Replace, delete, or insert multiple lines at once
• Native diff display - Shows diff output with change statistics
• TypeScript support - Full type definitions included

Installation

Add to your opencode.json:

{
  "plugins": ["opencode-fastedit"]
}

Usage

The fastedit tool replaces a range of lines in a file with new code.

Parameters

| Parameter | Type | Required | Description | |-----------|------|----------|-------------| | file_path | string | Yes | Absolute path to the file to modify | | start_line | number | Yes | Starting line number (1-indexed) | | end_line | number | Yes | Ending line number (inclusive) | | new_code | string | Yes | Code to insert (empty string to delete only) |

Examples

// Replace lines 10-20 with new code
fastedit({
  file_path: "/path/to/file.ts",
  start_line: 10,
  end_line: 20,
  new_code: "const newFunction = () => {\n  return 'hello';\n};"
})

// Delete lines 5-10 (empty new_code)
fastedit({
  file_path: "/path/to/file.ts",
  start_line: 5,
  end_line: 10,
  new_code: ""
})

// Insert at line 5 (replace zero-length range)
fastedit({
  file_path: "/path/to/file.ts",
  start_line: 5,
  end_line: 4,
  new_code: "// This comment was inserted before original line 5"
})

Behavior

• Replaces all lines from start_line to end_line (inclusive) with new_code
• If new_code is empty, the lines are simply deleted
• Uses 1-indexed line numbers (matching the view tool output)
• Generates a unified diff showing changes

Diff Display

The pretty diff UI (colored green/red with split/unified views) requires OpenCode to include a fix for preserving plugin metadata.

Tracking Issue: anomalyco/opencode#12527

Once resolved, plugin tools will be able to display diffs in the same rich format as built-in tools.

License

MIT

Related

• OpenCode - The AI coding agent