mcp-vsdiff

An MCP server that exposes VS Code's advanced diff algorithm as a tool.

What it does

Provides a single MCP tool, compute_diff, that computes a highly accurate unified diff between two strings using the same algorithm VS Code uses internally. Features include:

• Move detection — identifies blocks of code that were moved, not just deleted/inserted
• Unified diff output — standard @@-style hunks with 3 lines of context
• Move annotations — deleted lines show {moved to block #N} and inserted lines show {moved from block #N}
• Summary footer — total insertions, deletions, and moved blocks at the end

Usage

Install

npm install

Run

npm start

The server communicates over stdio and is compatible with any MCP client.

Tool: compute_diff

Parameter	Type	Required	Description
originalText	string	✅	The original text
modifiedText	string	✅	The modified text
ignoreTrimWhitespace	boolean		Ignore leading/trailing whitespace differences per line (default: true)
includeMetrics	boolean		Append a JSON metrics block to the response (default: true)
verboseMetrics	boolean		Add per-hunk breakdown to the metrics block (default: false)
metricsOnly	boolean		Return only the metrics block, no diff text — useful for large files (default: false)
maxDiffLines	number		Truncate the diff text if it exceeds this number of lines (default: 500). Set to 0 to disable.
skipDiffLines	number		Number of diff text lines to skip from the beginning. Combine with maxDiffLines to paginate through very large diffs (default: 0).

Metrics fields

Field	Description
hunkCount	Number of separate change regions (lower = easier to review)
changedLines	Real insertions + real deletions, excluding moved lines
realInsertions	Lines added, excluding moved lines
realDeletions	Lines removed, excluding moved lines
movedBlocks	Number of detected move operations
movedLines	Total lines involved in moves
hitTimeout	Whether the diff computation hit the 5 s time limit

ignoreTrimWhitespace gotcha: with the default true, a line whose only change is indentation (e.g. code moved into a deeper if block) will appear as unchanged context, making the diff look cleaner than a plain git diff would. Set to false if indentation changes need to be visible.

MCP config example

{
  "mcpServers": {
    "vsdiff": {
      "command": "node",
      "args": ["/path/to/mcp-diff/index.js"]
    }
  }
}

Dependencies

• @modelcontextprotocol/sdk — MCP server framework
• vscode-diff — VS Code's diff algorithm, extracted as a standalone package