Troubleshooting

Troubleshooting

"When a tool call does not do what you expected, work through these in order. Most problems are one of three things: REAPER is not listening, the ports do not match, or another process holds the feedback port."

A tool runs but nothing happens in REAPER

OSC is fire-and-forget UDP: when the ports do not match, nothing errors and nothing happens. In REAPER, open Options, then Preferences, then Control/OSC/web, and confirm the OSC control surface from the install page is present with the local listen port set to 8000. The server sends to port 8000 by default; if you changed that with --port or DEADCAT_REAPER_PORT, the two must agree. REAPER applies the change as soon as you close the dialog; no restart is needed.

A write tool reports that REAPER did not confirm the change

The server checks each write against REAPER's own reported state, and that report arrives through the feedback device: in the same Control/OSC/web dialog, set the device IP to 127.0.0.1 and the device port to 9001. Without that device, writes still reach REAPER but nothing comes back to confirm them.

Some unconfirmed reports are expected even with feedback configured. REAPER sends no position feedback while the transport is stopped, so moving the edit cursor on a stopped transport reports that it could not confirm. Markers have no feedback surface at all, so the marker tools report what they sent without claiming confirmation.

A read tool returns null fields or unnamed tracks

A null field means REAPER has not reported that value yet. A track listed without a name is usually an empty slot in REAPER's eight-track surface bank. The picture fills in as the session changes and REAPER reports more state.

The feedback port is in use

Only one process can own UDP port 9001 at a time. A second server instance, or a deadcat read command running while a server holds the port, says so instead of guessing. Quit the extra instance, or move one of them with --feedback-port and match the device port in REAPER.

reaper_insert_media reports that the bridge is not installed

reaper_insert_media needs the bridge script registered once; the steps are on the install page. The common failure is editing reaper-kb.ini while REAPER is running: REAPER rewrites that file on exit, so an edit made while it runs is silently lost. Quit REAPER fully, edit, then relaunch.

The extension does not appear in Claude Desktop

Claude Desktop loads extensions at launch. After installing the bundle, quit and reopen the app, then check Settings, then Extensions.

Still stuck?

REAPER's own OSC documentation explains the control surface DeadCat talks to, and is worth a read when the failure seems to be on REAPER's side of the wire. Otherwise, open an issue with the tool call you made, what you expected, and what happened.