Bundled `mosh-client`

This directory holds the network-protocol-only mosh-client binary bundled with the Netcatty installer. Netcatty drives the ssh + mosh-server bootstrap itself and then launches this bundled client directly (see electron/bridges/moshHandshake.cjs and electron/bridges/terminalBridge.cjs).

How binaries land here

.github/workflows/build-mosh-binaries.yml builds or fetches mosh-client on relevant pushes/PRs, or on a manual workflow_dispatch. It uses scripts/build-mosh/build-linux.sh and scripts/build-mosh/build-macos.sh for Linux/macOS, and scripts/build-mosh/fetch-windows.sh for the pinned Windows bundle:

target	provenance
`linux-x64`	upstream source, manylinux2014, static third-party deps + glibc
`linux-arm64`	upstream source, manylinux2014, static third-party deps + glibc
`darwin-universal`	upstream source, lipo arm64 + x86_64, macOS system dylibs only
`win32-x64`	Netcatty-pinned runtime bundle + FluentTerminal fallback
`win32-arm64`	(not built — Cygwin arm64 port not yet stable)

The upstream Cygwin Windows build is not rebuilt in this workflow by default. Windows releases use a SHA256-pinned bundle that was built by Netcatty and verified for packaging.

When manually dispatched with release_tag, that workflow publishes the binaries to the dedicated binaricat/Netcatty-mosh-bin repository. The release gets a tag like mosh-bin-1.4.0-1, with SHA256SUMS attached.
Release packaging runs scripts/resolve-mosh-bin-release.cjs before npm run fetch:mosh. It uses an explicit workflow input first, then the MOSH_BIN_RELEASE repository variable, then the latest non-draft mosh-bin-* GitHub Release from the dedicated binary repository. The fetch step pulls the binaries into resources/mosh/<platform-arch>/. For local packaging, set MOSH_BIN_RELEASE yourself before running the same fetch command. Override MOSH_BIN_OWNER / MOSH_BIN_REPO only when testing a different binary repository. electron-builder.config.cjs then copies the matching binary into Resources/mosh/mosh-client[.exe].

Local dev uses the same binary path: npm run dev runs npm run fetch:mosh:dev first, which downloads the host platform's bundled mosh-client into this gitignored directory. Netcatty does not fall back to a system-installed mosh or mosh-client; if the bundled binary is missing, Mosh startup fails loudly instead of using whatever happens to be installed on the developer machine.

Official Windows package builds currently ship x64 only for bundled Mosh coverage. Windows arm64 packaging should be added only after we have a tested arm64 client bundle.

The directory is otherwise empty (binaries are gitignored).

Licenses

Mosh itself is licensed under GPL-3.0 (https://github.com/mobile-shell/mosh).
Netcatty is GPL-3.0, so redistribution as part of the installer is permitted.
The default Windows x64 artifact is a SHA256-pinned Netcatty mosh-client-win32-x64.tar.gz bundle from binaricat/Netcatty-mosh-bin release mosh-bin-1.4.0-2. It includes mosh-client.exe, required Cygwin runtime DLLs, and the bundled xterm-256color terminfo entry. The FluentTerminal standalone mosh-client.exe from https://github.com/felixse/FluentTerminal @ commit bad0f85 remains published as a pinned fallback.
Bundled/static deps (OpenSSL Apache-2.0, protobuf BSD-3-Clause, ncurses MIT) are compatible with GPL-3.0.

Reproducible build

To reproduce the binaries locally:

docker run --rm -v $PWD:/workspace -w /workspace \
  -e MOSH_REF=mosh-1.4.0 -e ARCH=x64 -e OUT_DIR=/workspace/out \
  quay.io/pypa/manylinux2014_x86_64 \
  bash scripts/build-mosh/build-linux.sh

For macOS the build needs an Xcode toolchain; see scripts/build-mosh/build-macos.sh.

Phase 2/3 — done in this PR

electron/bridges/moshHandshake.cjs reimplements the upstream Mosh Perl wrapper in Node: parser + sniffer + command builders as pure functions.
terminalBridge.startMoshSession runs the SSH bootstrap in a node-pty so password / 2FA / known-hosts prompts render naturally in the user's terminal, then swaps session.proc from the ssh PTY to a freshly-spawned mosh-client PTY when MOSH CONNECT is detected. Keystrokes that arrive after the swap go to mosh-client because writeToSession reads session.proc lazily.
Mosh startup requires Netcatty's bundled mosh-client and a usable ssh client for the remote bootstrap. System-installed mosh / mosh-client binaries are intentionally ignored.
Windows x64 currently ships the pinned Netcatty runtime bundle. The old standalone client remains only as a release fallback.

Roadmap

Add Windows arm64 only after a tested arm64 client bundle is available.
Make MOSH_REF track upstream release tags automatically.

README.md