Sotto

Local translation, right where you read.

Sotto is a native macOS menu bar app. Select text in any app and press Command+C twice to open a translation beside the selection.

Status

This repository currently contains the first interaction prototype:

• menu bar lifecycle
• double-copy detection through the system pasteboard
• selection bounds lookup through the macOS Accessibility API
• a lightweight floating panel near the selected text, with scroll support for longer text
• menu controls for pausing/resuming the double-copy trigger
• a replaceable translation engine boundary
• native in-process MLX Swift translation engine

Translation runs in-process through MLX Swift LM with the default model id mlx-community/translategemma-4b-it-4bit_immersive-translate. The model is prepared in the background on app launch. On first launch, Sotto downloads it from Hugging Face and caches it through the Hugging Face Swift client. Gemma-family models may require accepting the model terms on Hugging Face before download.

See Development Context for the product and technical assumptions behind the prototype. See Native MLX Plan for the intended single-app runtime architecture.

Requirements

• Apple Silicon Mac
• macOS 14 or later
• Swift 6.1.3 or later
• Xcode 15.2 or later for the macOS SDK

Run

scripts/patch-mlx-swift-lm.sh
swift build
scripts/build-metallib.sh
swift run Sotto

scripts/build-metallib.sh compiles the MLX Metal shader library. SwiftPM on the command line cannot build Metal shaders, so without this step the app aborts at launch with Failed to load the default metallib and the menu bar item never appears. See Development Context for details. The .app build below runs this step automatically.

On first use, grant Sotto access in System Settings → Privacy & Security → Accessibility. Without that permission, the panel falls back to the mouse pointer position. The menu bar item shows the current Accessibility status and includes actions to request permission or open the relevant System Settings pane.

For a more realistic local app run, build a .app bundle:

scripts/build-app.sh
open .build/Sotto.app

This is still a Mac app running on your machine directly. No iOS Simulator or emulator is required. Sotto runs as a menu bar app, so it does not open a normal Dock window. Development builds show a small startup popup so launch success is visible. The menu bar item shows model setup status and includes a retry action if preparation fails.

Local Translation Server

The normal app path no longer requires a user-managed local translation server. LocalServerTranslationEngine remains in the codebase as a debug fallback for comparing native MLX output against mlx_lm.server.

One debug path is MLX LM with the MLX-converted TranslateGemma model:

uv tool install mlx-lm
scripts/run-translation-server.sh

The server stays in the foreground and keeps the terminal occupied. After Starting httpd at 127.0.0.1 on port 8000..., no shell prompt is expected until you stop the server with Control+C.

Test

scripts/patch-mlx-swift-lm.sh
swift test

mlx-swift-lm 3.31.4 and swift-huggingface 0.9.0 currently need small Swift 6.1 concurrency patches when built with this toolchain. The patch script edits only SwiftPM checkouts under .build/checkouts; remove it once upstream releases compatible versions.