Cursor MCP Tool Boundary
The xclog, xcsym, and xcprof examples below are reference syntax, not executable commands for Cursor. Map each subcommand to the same-named MCP tool—for example, xclog launch to axiom_xclog_launch, xcsym crash to axiom_xcsym_crash, and xcprof record to axiom_xcprof_record—and preserve its arguments as structured fields. Do not run a bare helper binary. If a required MCP tool is unavailable, stop and report that the Axiom MCP integration is missing; do not fall back to a same-named executable.
Build & Environment
You MUST use this skill for ANY build, environment, or Xcode-related issue before debugging application code.
Cursor Subagent Routing
Delegate to the appropriate Cursor subagent when this router calls for a specialized auditor.
Capture Build and Test Diagnostics
Before the next necessary build or test, resolve bin/axbuild under the actual loaded package in Claude Code or Codex, or discover an executable on PATH in Pi. Check executable permission and run its absolute path with --help; assign that observed path to AXBUILD. Never infer an installation path from an example.
Cursor and MCP distributions do not bundle axbuild and expose no axbuild MCP wrapper. Use the saved-log fallback below when a verified shell helper is unavailable.
Before every Xcode invocation, run pgrep -lx xcodebuild; echo "pgrep exit=$?": exit 1 means none are running, 0 lists them, and any other exit means the inventory failed. Investigate existing builds; process count and age do not establish zombie status. Never terminate unrelated processes. When interrupted or timed out, axbuild also stops build scripts and other processes descended from its build that Xcode moved into separate process groups, found by parentage when cleanup begins and on each cleanup pass. It reports cleanup-incomplete for any such descendant it could not stop or verify (another user's, unreadable, or being debugged). Jobs that had already left the build's process tree, such as daemons or launchd-started tools, are neither stopped nor reported. Inspect ownership before stopping anything it lists. Discover the actual scheme and destination before executing:
Preserve caller flags, working directory, environment, test selection, coverage and explicit artifact paths. The wrapper adds absent diagnostic defaults; it never cleans caches or automatically rebuilds. Do not pipe a build through another command.
Inspect command (native outcome) and collection (evidence completeness) separately. Native success can accompany partial collection. The default JSON is bounded to 8,000 UTF-8 bytes; inspect omissions and read artifacts.report relative to the absolute artifacts.run directory for complete records and evaluated values. The startup stderr JSON identifies the run directory before completion. Use diagnostic locations and values rather than rebuilding to redisplay output.
The retained log is the primary compiler source; test results and validated Swift Testing events supplement it. A null failed-test count means uncertainty, not zero. Preserve result bundles for attachment export, coverage, console logs and deeper inspection. Native informational commands pass their output through.
Saved-log fallback: redirect the necessary native command's stdout/stderr to a unique file, let it finish, record its exit status and inspect that saved file. An xcresult build summary is not equivalent to the compiler log. Read an existing log before considering another build. If a build's output ends in a truncation marker, or before xcodebuild's closing ** BUILD … ** or ** TEST … ** line, read the saved log or report instead of rebuilding.
When to Use
Use this router when you encounter:
- Build failures (
BUILD FAILED, compilation errors, linker errors) - Test crashes or hangs
- Simulator issues (won't boot, device errors)
- Xcode misbehavior (stale builds, zombie processes)
- Dependency conflicts (CocoaPods, SPM)
- Build performance issues (slow compilation)
- Environment issues before debugging code
Routing Logic
This router invokes specialized skills based on the specific issue:
1. Environment-First Issues → xcode-debugging
Triggers:
BUILD FAILEDwithout obvious code cause- Tests crash in clean project
- Simulator hangs or won't boot
- "No such module" after SPM changes
- Zombie
xcodebuildprocesses - Stale builds (old code still running)
- Clean build differs from incremental build
- Device Hub / predicted-vs-built issues in Xcode 27 (
OS27) - Reproducing a device-only bug on a simulator (Device Hub) (
OS27)
Why xcode-debugging first: 90% of mysterious issues are environment, not code. Check this BEFORE debugging code.
Invoke: skills/xcode-debugging.md
2. Slow Builds → build-performance
Triggers:
- Compilation takes too long
- Type checking bottlenecks
- Want to optimize build time
- Build Timeline shows slow phases
Invoke: skills/build-performance.md
3. SPM Dependency Conflicts → spm-conflict-resolver (Agent)
Triggers:
- SPM resolution failures
- "No such module" after adding package
- Duplicate symbol linker errors
- Version conflicts between packages
- Swift 6 package compatibility issues
- Package.swift / Package.resolved conflicts
Why spm-conflict-resolver: Specialized agent that analyzes Package.swift and Package.resolved to diagnose and resolve Swift Package Manager conflicts.
Invoke: Delegate to the spm-conflict-resolver subagent
4. Security & Privacy Audit → security-privacy-scanner (Agent)
Triggers:
- App Store submission prep
- Privacy Manifest requirements (iOS 17+)
- Hardcoded credentials in code
- Sensitive data storage concerns
- ATS violations
- Required Reason API declarations
Why security-privacy-scanner: Specialized agent that scans for security vulnerabilities and privacy compliance issues.
Invoke: Delegate to the security-privacy-scanner subagent or /axiom-audit security
5. iOS 17→18 Modernization → modernization-helper (Agent)
Triggers:
- Migrate ObservableObject to @Observable
- Update @StateObject to @State
- Adopt modern SwiftUI patterns
- Deprecated API cleanup
- iOS 17+ migration
Why modernization-helper: Specialized agent that scans for legacy patterns and provides migration paths with code examples.
Invoke: Delegate to the modernization-helper subagent or /axiom-audit modernization
6. Build Failure Auto-Fix → build-fixer (Agent)
Triggers:
- BUILD FAILED with no clear error details
- Build sometimes succeeds, sometimes fails
- App builds but runs old code
- "Unable to boot simulator" error
- Want automated environment-first diagnostics
Why build-fixer: Autonomous agent that checks zombie processes, Derived Data, SPM cache, and simulator state before investigating code. Saves 30+ minutes on environment issues.
Invoke: Delegate to the build-fixer subagent or /axiom-fix-build
7. Slow Build Optimization → build-optimizer (Agent)
Triggers:
- Builds take too long
- Want to identify slow type checking
- Expensive build phase scripts
- Suboptimal build settings
- Want parallelization opportunities
Why build-optimizer: Scans Xcode projects for build performance optimizations — slow type checking, expensive scripts, suboptimal settings — to reduce build times by 30-50%.
Invoke: Delegate to the build-optimizer subagent or /axiom-optimize-build
8. General Dependency Issues → build-debugging
Triggers:
- CocoaPods resolution failures
- "Multiple commands produce" errors
- Framework version mismatches
- Non-SPM dependency graph conflicts
Invoke: skills/build-debugging.md
9. TestFlight Crash Triage → testflight-triage
Triggers:
- Beta tester reported a crash
- Crash reports in Xcode Organizer
- Crash logs aren't symbolicated
- TestFlight feedback with screenshots
- App was killed but no crash report
Why testflight-triage: Systematic workflow for investigating TestFlight crashes and reviewing beta feedback. Covers symbolication, crash interpretation, common patterns, and Claude-assisted analysis.
Invoke: See axiom-shipping (skills/testflight-triage.md)
10. App Store Connect Navigation → app-store-connect-ref
Triggers:
- How to find crashes in App Store Connect
- ASC metrics dashboard navigation
- Understanding crash-free users percentage
- Comparing crash rates between versions
- Exporting crash data from ASC
- App Store Connect API for crash data
Why app-store-connect-ref: Reference for navigating ASC crash analysis, metrics dashboards, and data export workflows.
Invoke: See axiom-shipping (skills/app-store-connect-ref.md)
11. Crash Log Analysis → crash-analyzer (Agent)
Triggers:
- User has .ips or .crash file to analyze
- User pasted crash report text
- Need to parse crash log programmatically
- Identify crash pattern from exception type
- Check symbolication status
Why crash-analyzer: Autonomous agent that parses crash reports, identifies patterns (null pointer, Swift runtime, watchdog, jetsam), and generates actionable analysis.
Invoke: Delegate to the crash-analyzer subagent or /axiom-analyze-crash
12. MetricKit API Reference → metrickit-ref
Triggers:
- MetricKit setup and subscription
- MXMetricPayload parsing (CPU, memory, launches, hitches)
- MXDiagnosticPayload parsing (crashes, hangs, disk writes)
- MXCallStackTree decoding and symbolication
- Field crash/hang collection
- Background exit metrics
Why metrickit-ref: Complete MetricKit API reference with setup patterns, payload parsing, and integration with crash reporting systems.
Invoke: See axiom-performance (skills/metrickit-ref.md)
13. Hang Diagnostics → hang-diagnostics
Triggers:
- App hangs or freezes
- Main thread blocked for >1 second
- UI unresponsive to touches
- Xcode Organizer shows hang diagnostics
- MXHangDiagnostic from MetricKit
- Watchdog terminations (app killed during launch/background transition)
Why hang-diagnostics: Systematic diagnosis of hangs with decision tree for busy vs blocked main thread, tool selection (Time Profiler, System Trace), and 8 common hang patterns with fixes.
Invoke: See axiom-performance (skills/hang-diagnostics.md)
14. Live Debugging → lldb
Triggers:
- Need to reproduce a crash interactively
- Want to set breakpoints and inspect state
- Crash report analyzed, now need live investigation
- Need to attach debugger to running app
Why lldb: Crash reports tell you WHAT crashed. LLDB tells you WHY.
Invoke: skills/lldb.md
16. Runtime Console Capture → xclog-ref
Triggers:
- Need to see what the app is logging at runtime
- App crashes but no crash report (need console output)
- Silent failures (network, data, auth) with no UI feedback
- Want to capture print()/os_log() output from simulator
- Need structured log output for analysis
- "What is the app printing?"
Why xclog-ref: Xcode's debug console isn't accessible externally. xclog combines simctl stdout/stderr with log stream JSON to capture everything print(), NSLog(), os_log(), and Logger emit — with structured fields (level, subsystem, category) for automated analysis.
Invoke: /axiom-console
15. Code Signing Issues → code-signing
Triggers:
- "No signing certificate found"
- "Provisioning profile doesn't include signing certificate"
- errSecInternalComponent in CI
- ITMS-90035 Invalid Signature on upload
- Ambiguous identity / multiple certificates
- Entitlement mismatch or missing capability
- Setting up CI/CD code signing (GitHub Actions, fastlane match)
- Certificate expired or revoked
Why code-signing: Code signing errors are NEVER code bugs — they are 100% configuration (certificates, profiles, entitlements, keychains). Diagnosing with CLI tools takes 5 minutes vs hours of guessing.
Invoke: See axiom-security (skills/code-signing.md) (workflows) or See axiom-security (skills/code-signing-diag.md) (troubleshooting)
Decision Tree
- Mysterious/intermittent/clean build fails? → xcode-debugging (environment-first)
- SPM dependency conflict? → spm-conflict-resolver (Agent)
- CocoaPods/other dependency conflict? → build-debugging
- Slow build time? → build-performance
- Security/privacy/App Store prep? → security-privacy-scanner (Agent)
- Want automated build fix (environment-first diagnostics)? → build-fixer (Agent)
- Want build time optimization scan? → build-optimizer (Agent)
- Modernization/deprecated APIs? → modernization-helper (Agent)
- TestFlight crash/feedback? → testflight-triage
- Navigating App Store Connect? → app-store-connect-ref
- Have a crash log (.ips/.crash)? → crash-analyzer (Agent)
- MetricKit setup/parsing? → metrickit-ref
- App hang/freeze/watchdog? → hang-diagnostics
- Need to reproduce crash interactively / inspect runtime state? → lldb
- Code signing error (certificate, profile, entitlement, Keychain)? → code-signing / code-signing-diag
- Need to see runtime console output (print/os_log)? → xclog-ref or
/axiom-console
Anti-Rationalization
When NOT to Use (Conflict Resolution)
Do NOT use axiom-build for these — use the correct router instead:
axiom-build is for environment mysteries, not code errors:
- ✅ "No such module" when code is correct
- ✅ Simulator won't boot
- ✅ Clean build fails, incremental works
- ✅ Zombie xcodebuild processes
- ❌ Swift concurrency warnings/errors
- ❌ Database migration failures
- ❌ Type checking errors in valid code
Example Invocations
User: "My build failed with a linker error"
→ Invoke: skills/xcode-debugging.md (environment-first diagnostic)
User: "Builds are taking 10 minutes"
→ Invoke: skills/build-performance.md
User: "SPM won't resolve dependencies"
→ Invoke: spm-conflict-resolver agent
User: "Two packages require different versions of the same dependency"
→ Invoke: spm-conflict-resolver agent
User: "Duplicate symbol linker error"
→ Invoke: spm-conflict-resolver agent
User: "I need to prepare for App Store security review"
→ Invoke: security-privacy-scanner agent
User: "Do I need a Privacy Manifest?"
→ Invoke: security-privacy-scanner agent
User: "Are there hardcoded credentials in my code?"
→ Invoke: security-privacy-scanner agent
User: "How do I migrate from ObservableObject to @Observable?"
→ Invoke: modernization-helper agent
User: "Update my code to use modern SwiftUI patterns"
→ Invoke: modernization-helper agent
User: "Should I still use @StateObject?"
→ Invoke: modernization-helper agent
User: "A beta tester said my app crashed" → Invoke: See axiom-shipping (skills/testflight-triage.md)
User: "I see crashes in App Store Connect but don't know how to investigate" → Invoke: See axiom-shipping (skills/testflight-triage.md)
User: "My crash logs aren't symbolicated" → Invoke: See axiom-shipping (skills/testflight-triage.md)
User: "I need to review TestFlight feedback" → Invoke: See axiom-shipping (skills/testflight-triage.md)
User: "How do I find crashes in App Store Connect?" → Invoke: See axiom-shipping (skills/app-store-connect-ref.md)
User: "Where's the crash-free users metric in ASC?" → Invoke: See axiom-shipping (skills/app-store-connect-ref.md)
User: "How do I export crash data from App Store Connect?" → Invoke: See axiom-shipping (skills/app-store-connect-ref.md)
User: "Analyze this crash log" [pastes .ips content]
→ Invoke: crash-analyzer agent or /axiom-analyze-crash
User: "Parse this .ips file: ~/Library/Logs/DiagnosticReports/MyApp.ips"
→ Invoke: crash-analyzer agent or /axiom-analyze-crash
User: "Why did my app crash? Here's the report..."
→ Invoke: crash-analyzer agent or /axiom-analyze-crash
User: "How do I set up MetricKit to collect crash data?"
→ Invoke: See axiom-performance (skills/metrickit-ref.md)
User: "How do I parse MXDiagnosticPayload?"
→ Invoke: See axiom-performance (skills/metrickit-ref.md)
User: "What's in MXCallStackTree and how do I decode it?"
→ Invoke: See axiom-performance (skills/metrickit-ref.md)
User: "My app hangs sometimes"
→ Invoke: See axiom-performance (skills/hang-diagnostics.md)
User: "The main thread is blocked and UI is unresponsive"
→ Invoke: See axiom-performance (skills/hang-diagnostics.md)
User: "Xcode Organizer shows hang diagnostics for my app"
→ Invoke: See axiom-performance (skills/hang-diagnostics.md)
User: "My app was killed by watchdog during launch"
→ Invoke: See axiom-performance (skills/hang-diagnostics.md)
User: "I have a crash report and need to reproduce it in the debugger"
→ Invoke: skills/lldb.md
User: "How do I set breakpoints to catch this crash?"
→ Invoke: skills/lldb.md
User: "My build is failing with BUILD FAILED but no error details"
→ Invoke: build-fixer agent or /axiom-fix-build
User: "Build sometimes succeeds, sometimes fails"
→ Invoke: build-fixer agent or /axiom-fix-build
User: "How can I speed up my Xcode build times?"
→ Invoke: build-optimizer agent or /axiom-optimize-build
User: "No signing certificate found when I try to build" → Invoke: See axiom-security (skills/code-signing-diag.md)
User: "errSecInternalComponent in my GitHub Actions CI" → Invoke: See axiom-security (skills/code-signing-diag.md)
User: "How do I set up code signing for GitHub Actions?" → Invoke: See axiom-security (skills/code-signing.md)
User: "What is my app printing to the console?"
→ Invoke: /axiom-console
User: "I need to see the simulator console output"
→ Invoke: /axiom-console
User: "The app fails silently, no error in the UI"
→ Invoke: /axiom-console
