Fast Sub is a local-first subtitle tool for video and audio files.

It currently provides:

• A Python v0 CLI for local subtitle generation and translation workflows.
• A Go product core and local daemon for desktop orchestration.
• An Electron desktop app with Windows x64 installer / portable zip release-candidate artifacts and a macOS arm64 preview dmg.

The project defaults to local processing. Remote API or web providers must be selected explicitly before media or subtitle text is uploaded.

Fast Sub is at the desktop public-preview / release-candidate stage.

• Windows x64 installer and portable zip have passed Round 13 smoke records.
• macOS arm64 dmg has passed packaged runtime smoke on a macOS arm64 release machine.
• Windows builds are currently unsigned preview builds.
• macOS builds are currently ad-hoc signed and not notarized; Gatekeeper may require manual user approval.
• Models are not bundled with the installer; first-start model installation is managed by the app/model store.
• FFmpeg / FFprobe are not bundled. The desktop app can use a user-selected directory, an app-private explicit download, or a same-directory system PATH pair. Missing FFmpeg does not block opening the app, but transcription and burn-in require it before a job starts.
• The default local translation model is not bundled and is license-sensitive; the current default NLLB manifest is marked CC-BY-NC-4.0.

See dev-docs/current-status.md for the current project snapshot.

Preview artifacts are prepared through GitHub Releases. If the latest release is still marked as a draft, maintainers must publish it before external users can download the files.

See help-docs/help/download.md for download status and release limitations. Checksums and release notes are tracked in dev-docs/release/v0.13.2.md.

Package size note: the desktop packages are large because they include Electron/Chromium plus an app-private Python AI runtime. Model files are still downloaded after installation and are not bundled. Windows includes bundled aria2 for FFmpeg downloads; macOS uses the built-in HTTPS downloader by default.

For source checkout validation:

$env:GOCACHE=(Join-Path (Get-Location) '.gocache')
go test ./...

uv run pytest

cd desktop
npm run typecheck
npm test
npm run build

cmd/                 Go CLI entrypoints
internal/            Go product core, daemon, providers, jobs, models, runtime adapters
src/                 Python CLI, workers, providers, translation, model store, benchmark code
desktop/             Electron desktop app
tests/               Python tests
desktop-tests/       Desktop QA, release smoke records, screenshots, license reports
help-docs/           User help site and GitHub Pages source
dev-docs/            Project plans, architecture, specs, and implementation docs
dev-docs/go-docs/    Go standards and daemon/API specs
dev-docs/ui-docs/    Electron product, architecture, specs, and tracker
local_tests/         Local-only real media/model smoke inputs; do not commit large assets

Python checks:

uv run ruff format --check src\fast_sub tests
uv run ruff check src\fast_sub tests
uv run mypy src
uv run pytest

Go checks:

$env:GOCACHE=(Join-Path (Get-Location) '.gocache')
go test ./...

Desktop checks:

cd desktop
npm run typecheck
npm test
npm run build
npm run smoke

Windows package smoke:

cd desktop
npm run package:dir
npm run smoke:packaged

• Live user help: GitHub Pages help site for normal product usage.
• help-docs/help/README.md: user help and task guides.
• help-docs/help/download.md: download and platform status.
• help-docs/help/release-notes.md: user-facing release status and known limitations.
• dev-docs/README.md: documentation map.
• dev-docs/current-status.md: current status and next work.
• dev-docs/product/mvp.md: v0 MVP summary.
• dev-docs/go-docs/specs/daemon-api.md: daemon API contract.
• dev-docs/api/README.md: generated API/reference documentation policy and index.
• dev-docs/release/validation.md: release validation evidence index.
• dev-docs/ui-docs/project-tracker.md: detailed desktop implementation tracker.
• desktop-tests/round13-release-checklist.md: release checklist.
• ROADMAP.md: public roadmap.
• CONTRIBUTING.md: contribution rules.
• CODE_OF_CONDUCT.md: community expectations.
• LICENSE: Fast Sub source license.

Default local providers do not upload media or subtitles. Remote/web/API providers require explicit user selection and confirmation. Renderer code must not receive raw daemon tokens, raw provider secrets, Authorization headers, or raw secret references.

See help-docs/privacy.md.

Fast Sub source code is licensed under the MIT License.

Third-party dependencies, native runtime downloads, and model artifacts keep their own licenses and distribution policies. See THIRD_PARTY_NOTICES.md for details, especially before redistributing packaged binaries or using the default NLLB translation model commercially.