Paratran

Overview

Paratran is a transcription tool for macOS on Apple Silicon. It wraps NVIDIA’s Parakeet TDT model (running through parakeet-mlx) in three interfaces: a CLI for one-off jobs, a REST API for long-running services, and an MCP server so Claude Code or Claude Desktop can transcribe audio as a tool call.

I built it because Whisper is slow on a laptop and most of the fast alternatives are cloud services. The default Parakeet model hits 6.34% average WER across eight English benchmarks, supports 25 languages, and runs roughly 30x faster than Whisper on the same hardware via MLX. It’s fast enough that a one-hour recording transcribes in well under a minute on an M-series chip.

Features

CLI

• Transcribe one file or a batch in a single command
• Output as plain text, JSON, SRT, or WebVTT (or all four at once)
• Greedy or beam search decoding with full control over beam size, length penalty, patience, and duration reward
• Chunking for long audio with configurable overlap so sentence boundaries survive joins
• Optional sentence splitting by max words, max duration, or silence gap
• BF16 by default with an --fp32 flag for environments that need it

Client mode (no per-file model reload)

The model takes a few seconds to load. Reloading it for every file is wasteful, so the same paratran binary doubles as a client: start paratran serve once, then point subsequent invocations at it with -s http://localhost:8000 (or PARATRAN_SERVER in the environment) and they hand the file off over HTTP and print the result. The CLI surface is identical either way.

REST API

A FastAPI server exposes /health and /transcribe. Upload a wav, mp3, flac, m4a, ogg, or webm file and get back the text plus per-sentence timing and per-token timestamps as JSON. All decoding and sentence-splitting options are query parameters, and interactive docs ship at /docs.

curl -X POST http://localhost:8000/transcribe -F "file=@recording.m4a"

MCP server

The same package installs paratran-mcp, an MCP server that exposes a transcribe tool to any MCP client. Stdio is the default (drop a few lines into .claude/settings.json and Claude Code can transcribe audio files in-place), and a streamable HTTP transport is available for remote or multi-client setups.

{
  "mcpServers": {
    "paratran": {
      "command": "uvx",
      "args": ["--from", "paratran", "paratran-mcp"]
    }
  }
}

Quick start

# Run without installing
uvx paratran recording.wav

# Or install as a tool
uv tool install paratran
paratran recording.wav

# Start the server once, transcribe many files instantly
paratran serve &
paratran -s http://localhost:8000 --output-format all recording.wav

The default model (parakeet-tdt-0.6b-v3) downloads on first use into the HuggingFace cache. --cache-dir or PARATRAN_MODEL_DIR redirects it to an external drive when the local SSD is tight.

Technology stack

• Python 3.11+, distributed on PyPI as paratran
• parakeet-mlx for inference, running on Apple’s MLX framework
• FastAPI and Uvicorn for the REST server
• The official mcp Python SDK for the MCP server, with stdio and streamable-HTTP transports
• macOS on M1/M2/M3/M4 (the MLX backend is Apple Silicon only)