XcodeBazelMCP: Skill for Claude Code

Simulator Workflow

Build + Run + Launch Chain

The bazel_ios_build_and_run tool chains these steps (each failure short-circuits):

1. Build — bazel build <target>
2. Find app — search bazel-bin/ using target label's package path
3. Resolve simulator — priority: explicit UDID > name match > first booted > first available iPhone > first available device
4. Boot — lazy, only simctl boot if state != Booted
5. Install — simctl install <udid> <app_path>
6. Read bundle ID — plutil -convert json -o - on Info.plist (sync execSync)
7. Launch — simctl launch <udid> <bundleId>

App Bundle Discovery

• After bazel build, search bazel-bin/ using the target label's package path.
• Target //:Foo → bazel-bin/Foo.app, //Apps/Bar:Bar → bazel-bin/Apps/Bar/Bar.app.
• rules_apple places bundles inside <target>_archive-root/Payload/ — findAppBundle searches recursively.

Simulator Resolution

resolveSimulator returns { device: SimulatorDevice; warning?: string }:

• warning is set when the resolved simulator is not the explicitly requested one (fallback).
• resolveSimulatorFromArgs in helpers.ts is the convenience wrapper — returns { sim, warning }.
• prependWarning(message, warning) prepends the warning to tool output.

Launch Environment Variables

Env vars are passed via SIMCTL_CHILD_* prefix convention — simctl forwards them to the launched process.

For Cursor DEBUG MODE (NDJSON hypothesis logs), use the swift-agent-debug-log skill and bazel_ios_agent_debug_* tools:

• AGENT_DEBUG_LOG_PATH / AGENT_DEBUG_SESSION_ID via launchEnv on build_and_run or agent_debug_repro
• Simulator fallback: Documents/agent-debug.ndjson + bazel_ios_agent_debug_log_pull
• Do not rely on the sim app writing directly to .cursor/debug-*.log on the host

Platform CPU Flags

Platform	Flag
iOS simulator	--ios_multi_cpus=sim_arm64
iOS device	--ios_multi_cpus=arm64
macOS	(none — host arch)
tvOS	--tvos_cpus=sim_arm64
watchOS	--watchos_cpus=arm64
visionOS	--visionos_cpus=sim_arm64