Contributor workflow rules for cmux setup, Xcode project normalization, tagged sidebar ExtensionKit development, and dev builds. Use when setting up the cmux repo, changing Xcode project files, adding sidebar extensions, or working with tagged debug builds.

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: 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: Do not use /tmp/cmux cli for tagged dogfood; that symlink points at the most recently reloaded build. See [references/tagged builds.md](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](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: See [references/sidebar extension tagging.md](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.

cmux-dev-workflow