Installation

Download and install the latest release for your system:

https://github.com/kevinselwyn/nessemble-rs/releases

Release artifacts are provided for all five supported platforms:

Two more artifacts accompany every release:

• nessemble_<v>.vsix — the VS Code extension.
• nessemble_<v>_wasm.tar.gz — the in-browser assembler bundle (the WebAssembly build plus the <nessemble-assembler> web component).

A linux/amd64 container image is also published to GHCR for CI pipelines and coding agents that only need the executable.

VS Code extension

nessemble_<v>.vsix is the VS Code (and Cursor) extension: a client for the assembler's built-in language server, giving you diagnostics, lint hints, completion, hover, formatting, semantic highlighting, and go-to-definition on .asm/.s files.

It contains no copy of the assembler, so install nessemble itself first — the extension runs the nessemble on your PATH. One universal .vsix works on every platform:

code --install-extension nessemble_<v>.vsix

Or use the Extensions view's Install from VSIX… command. See Editor support for settings and format-on-save.

macOS: "Apple could not verify…"

The macOS .pkg is not signed with an Apple Developer ID or notarized, so after you download it, Gatekeeper blocks it with:

"nessemble_<v>.pkg" Not Opened — Apple could not verify "nessemble_<v>.pkg" is free of malware…

This is expected for an unsigned package; it does not mean the file is harmful. You have two options.

Install the .pkg anyway — clear the download-quarantine flag, then install:

xattr -d com.apple.quarantine nessemble_<v>.pkg
sudo installer -pkg nessemble_<v>.pkg -target /

Or use the plain binary tarball (nessemble_<v>_macos.tar.gz) and skip the installer:

tar -xzf nessemble_<v>_macos.tar.gz
xattr -d com.apple.quarantine nessemble     # clear quarantine
sudo mv nessemble /usr/local/bin/            # put it on your PATH

Both install the same binary to /usr/local/bin/nessemble. (The tarball binary is a 64-bit Intel build, matching the .pkg; it runs on Apple Silicon under Rosetta.)

Container image

A binary-only image is published to the GitHub Container Registry on every release:

ghcr.io/kevinselwyn/nessemble-rs:<version>   # e.g. :2.11.0
ghcr.io/kevinselwyn/nessemble-rs:latest

It exists for CI pipelines and coding agents that need the nessemble executable but not this source tree — pulling the image is faster and simpler than building the workspace. The image is a single statically-linked linux/amd64 binary on scratch: there is no shell, package manager, or libc inside it, only /nessemble. That means you consume it by lifting the binary out, not by opening a shell in it.

Copy it into your own image with a multi-stage COPY --from — the most common pattern for build tools:

COPY --from=ghcr.io/kevinselwyn/nessemble-rs:2.11.0 /nessemble /usr/local/bin/nessemble

Extract it to the host without writing a Dockerfile — create a container from the image (it need not run) and copy the file out:

docker create --name nessemble ghcr.io/kevinselwyn/nessemble-rs:2.11.0
docker cp nessemble:/nessemble ./nessemble
docker rm nessemble

Run it directly — the entrypoint is the binary, so pass nessemble arguments straight through and mount your project as the working directory:

docker run --rm ghcr.io/kevinselwyn/nessemble-rs:2.11.0 --version

docker run --rm -v "$PWD:/work" -w /work \
  ghcr.io/kevinselwyn/nessemble-rs:2.11.0 project.asm --output project.nes --format nes

Pin a version tag (:2.11.0) rather than :latest for reproducible builds. In a Claude Code on the web (or similar) environment, pulling the image in a setup script caches it into the environment snapshot, so the binary is on disk at the start of every later session.

From source

nessemble is a Cargo workspace and builds with a stock Rust toolchain.

git clone https://github.com/kevinselwyn/nessemble-rs
cd nessemble-rs
cargo build --release

The binary is written to target/release/nessemble. See Building for cross-compilation and packaging details.