Log Reducer MCP Server Cuts Token Usage When Claude Code Reads Logs

Log Reducer is an MCP server built specifically for Claude Code that reads log files server-side and sends only reduced output into conversations, preventing raw logs from entering the context window. According to the developer, a 2000-line log represents 20,000+ tokens permanently removed from sessions.

Compression Transforms

The tool runs 19 deterministic transforms to compress logs by 50-90% without making API calls:

• Folds stack traces — keeps code frames while collapsing framework noise
• Deduplicates repeated and near-identical lines
• Filters noise including health checks, heartbeats, progress bars, and Docker boilerplate
• Shortens UUIDs, timestamps, and long URLs
• Detects cycles and collapses repeating multi-line blocks
• Compacts access logs by stripping boilerplate down to method + path + status

Development with Claude Code

The entire project was built using Claude Code. The developer would paste log samples into conversations, Claude would analyze what could be compressed, implement transforms, and verify them against test fixtures. The evaluation workflow in the repository — which involves pasting a log, auto-generating ideal output, diffing against the pipeline, and implementing fixes — was designed to be driven entirely by Claude Code.

Setup and Usage

Install with npm install -g logreducer and add to your .claude/settings.json:

{
  "mcpServers": {
    "logreducer": {
      "command": "npx",
      "args": ["-y", "logreducer", "--mcp"]
    }
  }
}

To use: copy a log to your clipboard and type /logdump in Claude Code. The raw log is saved to a temporary file and reduced server-side automatically. You can also point it at files directly, filter by log level, grep with regex, or get structural summaries of large logs.

The tool is free and open source under the MIT license, available on GitHub at launch-it-labs/log-reducer and npm as logreducer.