Reaper Daemon

A local file bridge for driving REAPER from an AI agent. No network, no socket, nothing listening on a port. The agent drops JSON command files in a folder, a Lua script inside REAPER runs them and writes JSON results back. That is the whole design. If your agent speaks MCP, an optional stdio server in the repo exposes the same bridge as typed tools.

git clone https://github.com/wretcher207/reaper-daemon.git && cd reaper-daemon && python3 setup/install.py

View the source on GitHub →

Free and open source, MIT licensed. macOS, Windows, or Linux, REAPER plus Python 3, about thirty seconds to install.

What it does

• Project control: transport, tempo, cursor, time selection, render
• Tracks: add, delete, rename, select, volume, pan, mute, solo, arm, color
• FX: add, remove, bypass, reorder, set parameters, write automation envelopes
• Markers, regions, and media items
• MIDI: insert and audition MIDI files
• Discovery: scan_fx dumps every FX and parameter in the project
• Stem profiling: read a guitar track bar by bar and plan drums per section (Daemon Beater)
• Recipes: save a command sequence and replay it on any project

Every mutating command runs inside a REAPER undo block, so Cmd+Z reverts it like anything else.

Daemon Beater

New in 3.13. Before the agent writes a drum part, it reads the guitar. reaperd.py profile walks a stem bar by bar and prints what a drummer listens for: how dense the picking is, how regular, whether notes ring out or die palm-muted, where the silence sits, where the sections change, which sections repeat.

Point it at bar 33 and it reads just that window, not the whole song. It only pays for the bars you ask about, and the numbers match what a full pass would say. The agent proposes section labels, you correct them, and the drums get built section by section against real measurements instead of vibes.

How it works

One runtime. The Lua bridge runs forever as a defer loop inside REAPER. It polls an inbox folder, executes one command per tick, writes results to an outbox, and drops a heartbeat file you can check. It is the only thing that touches the REAPER API. Every JSON write is atomic, so a reader never sees a half-written file.

The bridge is plugin-agnostic. It ships with no knowledge of any specific synth, amp sim, or instrument. The agent learns what a project contains with scan_fx, then acts on tracks, FX, and parameters by name.

Who this is for

• Producers who already run a coding agent on their Mac and want it to touch their session, not just talk about it
• Anyone building tools on top of REAPER who does not want to maintain a socket server or an extension
• People who want their drum, MIDI, or FX automation generated and inserted in one move

Install

The fastest path is the one-line installer at the top of the page. It clones the repo and runs setup/install.py, which detects your OS, macOS, Windows, or Linux, finds REAPER’s resource folder, and writes a managed block into its startup script so the bridge loads on every launch.

If you already have a coding agent on your machine, you can hand the whole job to it instead. Paste the repo’s INSTALL.md into Claude Code or Codex and it will clone, wire startup, pause for you to restart REAPER, and run a real smoke test to confirm the bridge is live.

Reaper Daemon on GitHub →