doxa-maps/plugin-designs/rudder-voice

rudder-voice — Rudder, private voice-to-text (desktop target)

Rudder is a plugin that isn't a map. It shows that the same dx-maps pattern — one folder in plugin-designs/, developed live in the Plugin Studio — can ship a desktop app with its own local backend, not only embeddable maps. It is also a genuinely useful tool for the people who build here: talk to your agents instead of typing, with nothing leaving your computer.

• Streaming. Words appear in the text box while you speak; talk for as long as you like.

• Type and talk at once. Type, paste links or code anywhere in the box; everything you say is added to the end. While you're typing, Rudder holds its words and adds them when you pause.

• CPU only. No graphics card. About 1 GB of memory; keeps up with normal speech on a laptop CPU.

• Offline, no telemetry. NVIDIA Nemotron 3.5 ASR Streaming (0.6B) run by NVIDIA's open-source NeMo-Speech.cpp (ggml). Traced with strace while transcribing: zero sockets, zero DNS lookups.

• Microphones like a video-call app. Pick the input, hot-plug updates, a 3-second mic test, and plain-language errors (muted, disconnected, dead Bluetooth mic link — which it tries to recover).

• Robot voice (optional). Settings → Robot voice: every sentence you say is spoken back in a synthetic voice, so you can record a video that uses dictation without your real voice in it. Offline neural voices (Piper, run by the engine on the CPU) or the browser's own on-device voices; nothing leaves the computer. While the robot talks through loudspeakers, the engine stops listening, so it never transcribes itself; with headphones it keeps listening.

Run it in the Plugin Studio

bash backend/rudder-engine/setup-runtime.sh   # once: runtime + model (verified by SHA-256) + engine build
bun run dev                                   # starts the engine too; open "rudder-voice" in the studio

Linux with PipeWire or PulseAudio (parec, pactl). The engine listens on 127.0.0.1 only.

How it fits together

<rudder-voice> (this folder)  ──HTTP + SSE /api/rudder──►  backend/rudder-engine (Go)
                                                            ├─ parec / pw-record  (mic, open only while recording)
                                                            └─ WebSocket ► nemo-speech serve (127.0.0.1, model stays loaded)

bun run dev starts backend/bin/rudder-engine through internal/backend-dev-plugin.mjs and forwards /api/rudder to it, so the plugin calls the same API in the browser as it will inside the desktop app, where Tauri runs the engine as a sidecar and passes its address in profile-config (apiBase).

rudder-voice.meta.json declares "targets": ["desktop"]: on a plain website there is no local engine, so this plugin is not meant for web embeds.

Settings (environment variables)

Variable	Default	What it does
RUDDER_PORT	5193	engine HTTP port (loopback)
RUDDER_NEMO_PORT	5194	speech server port (loopback)
RUDDER_MODEL / RUDDER_NEMO_BIN	~/.local/share/rudder/...	model and runtime paths; the engine refuses a model that isn't a local file
RUDDER_LANG	en-US	default language (the model supports ~30)
RUDDER_KEEP_MSBC	unset	keep Bluetooth headsets on mSBC instead of switching them to the more stable CVSD
RUDDER_BT_RESET	unset	optional command that fully resets a Bluetooth headset, used when its mic link dies

Not yet

• The desktop app on macOS and Windows. On Linux it builds and runs: bun run desktop:build rudder-voice, see HOWTO-build-the-desktop-app.
• A saved word-correction table (PocketBase) for technical terms the model mishears.