cmux-dev-workflow

---

name: cmux-dev-workflow description: "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

Tagged local dev

After making code changes, always run the reload script with a tag to build the Debug app:

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

By default, reload.sh builds but does not launch the app. Pass --launch only when you need to open it automatically.

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, use the tag-bound helper and set CMUX_TAG:

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.

When rebuilding cmuxd for release/bundling, always use ReleaseFast:

cd cmuxd && zig build -Doptimize=ReleaseFast

Initial setup

Run the setup script to initialize submodules, build GhosttyKit, and install the pbxproj normalization pre-commit hook:

./scripts/setup.sh

Xcode toolchain

The team is pinned to Xcode 26.x. .xcode-version records the major; cmux.xcodeproj/project.pbxproj carries objectVersion = 60, which is what Xcode 26 writes by default. (objectVersion 77 is reserved for projects that adopt synchronized folder groups, which cmux does not use yet. Bumping to a different value requires a deliberate team decision.)

scripts/setup.sh installs a tracked pre-commit hook (scripts/git-hooks/pre-commit) that runs scripts/normalize-pbxproj.py on any staged cmux.xcodeproj/project.pbxproj, sorting the high-churn sections 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 anyone who skips the hook (or never ran setup) gets a clear failure on their PR.

.xcode-version is the single source of truth. To bump the pin: edit .xcode-version, open cmux.xcodeproj in the new Xcode (which rewrites objectVersion automatically when it touches the file), and add a case for the new Xcode major in scripts/check-pbxproj.sh mapping it to the objectVersion that major writes.

Sidebar extension point (dev tagging)

Each tagged dev build gets its own ExtensionKit sidebar extension point so concurrent dev builds don't collide. Three build settings drive this:

• 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 + availability counts the host reads (AppExtensionIdentity exposes only bundleIdentifier, localizedName, extensionPointIdentifier, id — cmux already keys its own identity off the stable bundleIdentifier, but the OS-level grouping is by name). Two same-named appexes installed side by side (a base build and a tagged build) are treated as one logical extension, so toggling one perturbs the other; a per-tag display name keeps them distinct.

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. ./scripts/reload-extension.sh --tag <tag> [--host-bundle-id <id>] [--example sample|tabs|both] builds a matching tag-scoped sample extension, passing CMUX_SIDEBAR_EXTENSION_POINT_ID=<host-bundle-id>.cmux.sidebar, CMUX_BUNDLE_ID_SUFFIX=.<tag>, and CMUX_DISPLAY_NAME_SUFFIX=" <tag>". It installs exactly what xcodebuild produced (xcodebuild ad-hoc signs with entitlements intact) — it does NOT re-sign, because a bare codesign --force --sign - strips the appex entitlements and the extension then drops its host XPC connection. pkd ingests the tagged copy because its bundle id is distinct. Verify with pluginkit -m -p <host-bundle-id>.cmux.sidebar.

To author a NEW sample extension that is tag-ready:

• appex Info.plist: EXAppExtensionAttributes:EXExtensionPointIdentifier = $(CMUX_SIDEBAR_EXTENSION_POINT_ID).
• add CMUX_SIDEBAR_EXTENSION_POINT_ID (default com.cmuxterm.app.cmux.sidebar), CMUX_BUNDLE_ID_SUFFIX (default empty), and CMUX_DISPLAY_NAME_SUFFIX (default empty) build settings to the app and appex targets in all build configs.
• PRODUCT_BUNDLE_IDENTIFIER = <appBase>$(CMUX_BUNDLE_ID_SUFFIX) for the app target and <appBase>$(CMUX_BUNDLE_ID_SUFFIX).<leaf> for the appex (suffix before the appex leaf so the appex id stays prefixed by the app id).
• appex INFOPLIST_KEY_CFBundleDisplayName (or the CFBundleDisplayName Info.plist value) = <Name>$(CMUX_DISPLAY_NAME_SUFFIX).
• it must be ad-hoc signed by xcodebuild (Info.plist bound, entitlements intact) for pkd to ingest the tagged copy; do not re-sign post-build.

Detailed references

• Read references/tagged-builds.md for detailed tagged reload, app link, socket, and cleanup behavior.
• Read references/xcode-project-normalization.md before touching .xcode-version or cmux.xcodeproj/project.pbxproj.
• Read references/sidebar-extension-tagging.md when changing ExtensionKit sidebar extension identifiers, tagged sample extensions, or pluginkit verification.