Debug - iOS App Debugging Loop

Use XcodeBuildMCP and ios-simulator MCPs to diagnose issues, capture app state, and collaborate with users on fixes. Always confirm before making changes.

Workflow

Capture current state — Use ios-simulator to capture screenshots and understand the current visual state of the app. Use XcodeBuildMCP to read build logs and runtime errors.

Gather diagnostic information — Collect relevant information:

• Screenshot of the issue using ios-simulator

• Console logs and error messages from XcodeBuildMCP

• App state and behavior observations

• Ask: "Looking at this screenshot and these logs, can you describe exactly what's wrong or what you expected to happen?"

Analyze the problem — Review the captured information:

• Identify error patterns in logs

• Compare visual output to expected behavior

• Locate relevant code sections that might be causing the issue

Propose changes clearly — Describe intended fixes with specifics:

• Bad: "I'll fix the layout"

• Good: "I'll update the VStack spacing from 8 to 16 points and add .padding(.horizontal, 20) to fix the alignment issue shown in the screenshot"

Confirm before implementing — Use AskUserQuestion to get explicit approval. Never modify code without confirmation.

Verify with comparison — After changes:

• Rebuild the app using XcodeBuildMCP

• Capture a new screenshot to confirm the fix

• Check logs to ensure errors are resolved

• Ask: "Does this match what you were looking for?"

XcodeBuildMCP Tools

Use these XcodeBuildMCP tools for building and analyzing:

• build — Build the Xcode project/workspace

• get-build-logs — Retrieve build logs to diagnose compilation errors

• get-runtime-logs — Get runtime logs from the running app

• clean — Clean build artifacts before rebuilding

• test — Run unit tests to verify fixes

ios-simulator Tools

Use these ios-simulator tools for app interaction and state capture:

• launch-app — Launch the app in the simulator

• take-screenshot — Capture the current simulator screen

• tap — Tap at specific coordinates on the screen

• swipe — Perform swipe gestures

• enter-text — Type text into focused text fields

• get-device-info — Get simulator device information

• install-app — Install the app on the simulator

• uninstall-app — Uninstall the app from the simulator

Related Skills

When implementing fixes, load these skills for guidance:

• app:swiftui-architecture — SwiftUI patterns, state management, and architectural guidance

• app:swift-testing — Testing patterns and best practices

Debugging Workflow Example

• User reports: "The login button doesn't work"

• Capture screenshot showing the button

• Check runtime logs for tap events or errors

• Identify the issue in code (e.g., missing action binding)

• Propose fix: "I'll connect the button's action to the LoginIntent as defined in app-intent-driven-development"

• Get confirmation

• Implement fix

• Rebuild app

• Take new screenshot showing working button

• Verify logs show successful tap handling

Before/After Verification

After implementing changes:

• Rebuild the app with XcodeBuildMCP

• Launch the updated app in the simulator

• Take a new screenshot of the same view

• Compare build/runtime logs (before and after)

• Present screenshots side by side

• Ask: "Does this resolve the issue?"

• If not, repeat the feedback loop