Build the macOS app from source

Requirements

The Zig version is what the pinned Ghostty submodule requires; scripts/build-ghostty.sh checks for it before building. Install it if you don't already have it.

brew install zig@0.15

Build libghostty

Fetch the submodules and build Ghostty.

git submodule update --init --recursive
scripts/build-ghostty.sh

This produces GhosttyKit.xcframework plus the Ghostty themes, shell integration, and terminfo the application bundle needs. You don't need to run it before every build, only after changing the Ghostty revision.

Build and test

swift build
swift test
Tests/ReleasePackagingTests.sh

Run swift run Mytty during development. The debug build is named Mytty Dev, shows a DEV Dock badge, and keeps its state in separate paths:

Use Path
Configuration ~/.config/mytty-dev/
Application data ~/Library/Application Support/mytty-dev/
Logs ~/Library/Logs/mytty-dev/

Sockets are also created separately inside a temporary directory, so they never interfere with an installed release build. Only agent hook installation is shared, since each provider's hooks are written to a config file shared by the whole user.

Package an application bundle

To bundle a debug build:

scripts/bundle.sh debug
open "dist/Mytty Dev.app"

To bundle a release build:

VERSION=0.1.0 BUILD_NUMBER=1 scripts/bundle.sh release
open dist/Mytty.app

It signs with a Developer ID identity if one can be found through SIGN_IDENTITY or scripts/resolve-signing-identity.sh, and falls back to an ad-hoc signature otherwise. An ad-hoc signature is fine for checking a build locally but can't be distributed to other Macs. Distributed builds go through the release workflow's signing and notarization instead; see Release a version.

SIMD build fails on Xcode 27 beta

The pinned Ghostty revision needs Zig 0.15.2, but its bundled libc++ can't compile Ghostty's SIMD C++ sources against the Xcode 27 beta SDK, because that SDK no longer exposes the INFINITY macro this compilation expects at compile time.

scripts/build-ghostty.sh works around this by disabling SIMD by default. This only affects the vendor library build, not Mytty itself. Once the pinned toolchain moves past this beta SDK generation, run the script with MYTTY_GHOSTTY_SIMD=true to confirm it still builds through the real SIMD path.