cmux Dev Workflow

Initial setup

./scripts/setup.sh initializes submodules, builds GhosttyKit, and installs the pbxproj normalization pre-commit hook.

Tagged local dev

Build the Debug app after every code change:

./scripts/reload.sh --tag <short-tag>

It builds without launching; pass --launch only when you need the app open. Never run bare xcodebuild or open an untagged cmux DEV.app: untagged builds share the default debug socket and bundle ID with other agents, causing conflicts and stealing focus.

For CLI or socket dogfood against a tagged Debug app:

CMUX_TAG=<tag> scripts/cmux-debug-cli.sh list-workspaces

Do not use /tmp/cmux-cli for tagged dogfood; that symlink points at the most recently reloaded build. See references/tagged-builds.md.

Xcode toolchain

The team is pinned to Xcode 26.x. .xcode-version is the single source of truth for the major; cmux.xcodeproj/project.pbxproj carries objectVersion = 60, what Xcode 26 writes by default. (objectVersion = 77 is reserved for synchronized folder groups, which cmux does not use.)

Intel Macs on macOS 14 with Xcode 16.2 (Swift 6.0.3) can still build the macOS app and run tagged reload.sh dev builds as a best-effort pathway. Keep app-linked Swift within Swift 6.0 syntax: no trailing commas in parameter or argument lists (SE-0439), no nonisolated on type declarations (SE-0449), and the #if compiler(>=6.2) / #else @Sendable split for @concurrent (SE-0461 is Swift 6.2; Swift 6.0 only warns that the attribute was renamed and does not implement its semantics). See "Intel Macs, Xcode 16.2, Swift 6.0" in AGENTS.md.

scripts/setup.sh installs the tracked scripts/git-hooks/pre-commit, which runs scripts/normalize-pbxproj.py on any staged project.pbxproj so Xcode's nondeterministic reordering never reaches a commit. The hook is idempotent. CI runs scripts/check-pbxproj.sh to enforce both the objectVersion pin and normalization, so skipping the hook gives a clear PR failure. Bumping the pin is a deliberate team decision: see references/xcode-project-normalization.md.

Sidebar extension point (dev tagging)

Each tagged dev build gets its own ExtensionKit sidebar extension point so concurrent dev builds do not collide. Three build settings drive it:

• CMUX_SIDEBAR_EXTENSION_POINT_ID (default com.cmuxterm.app.cmux.sidebar): the extension point identifier baked into Info.plist at build time.
• CMUX_BUNDLE_ID_SUFFIX (default empty): inserted into the app and appex bundle ids so a tagged extension gets a distinct identity that pkd records separately.
• CMUX_DISPLAY_NAME_SUFFIX (default empty): appended to the appex CFBundleDisplayName. The OS groups sidebar extensions by display name for the enable/disable and availability counts the host reads, so two same-named appexes installed side by side are treated as one logical extension and toggling one perturbs the other.

The host resolves its point id at runtime from the Info.plist key CMUXSidebarExtensionPointIdentifier via CmuxSidebarExtensionPoint.identifier(in:). ./scripts/reload.sh --tag <tag> scopes the host point to com.cmuxterm.app.debug.<tag>.cmux.sidebar. Build a matching tag-scoped sample extension with:

./scripts/reload-extension.sh --tag <tag> [--host-bundle-id <id>] [--example sample|tabs|both]

See references/sidebar-extension-tagging.md for the settings it passes, the no-re-signing rule, and the checklist for authoring a new tag-ready sample extension.