Xcode: Fix “dyld: Symbol not found: MetricKit.mxSignpost” with 26.4.1

An app that uses MetricKit and was built with Xcode 26.4 can crash immediately on iOS, macOS, or visionOS versions earlier than 26.4 with dyld: Symbol not found: MetricKit.mxSignpost. Apple fixed this toolchain issue in Xcode 26.4.1. Installing the update is only the first step: you must rebuild and redistribute the app with the updated Xcode.

Actual error
Cause
Affected versions and conditions
Recommended resolution
Workarounds
Verification checklist
Cautions
Summary
Official references

Actual error

dyld: Symbol not found: MetricKit.mxSignpost
Referenced from: <your app binary>
Expected in: /System/Library/Frameworks/MetricKit.framework/MetricKit
Abort trap: 6

The key crash-log terms are dyld, Symbol not found, mxSignpost, and MetricKit. The known issue is a strong match when the same Xcode 26.4 build launches on OS 26.4 but crashes at startup on a 26.3.x or other pre-26.4 system.

Cause

When Xcode 26.4 builds an app that links or uses MetricKit, the generated binary can contain a reference to a MetricKit symbol that is unavailable on operating-system versions earlier than 26.4. The dynamic loader cannot resolve that symbol, so the process terminates before normal application code and Swift error handling can run.

Apple Developer Technical Support tracked the report as FB22384135. Apple states in the Xcode 26.4.1 release notes that it fixed crashes caused by missing symbols in MetricKit apps built with Xcode 26.4 and run on iOS, macOS, and visionOS releases below 26.4. The Apple issue number is 173827073.

Affected versions and conditions

The app was compiled and linked with Xcode 26.4.
The app links or uses MetricKit.
The destination runs iOS, macOS, or visionOS earlier than 26.4.
Launch fails while resolving MetricKit.mxSignpost.

Fixed version: Xcode 26.4.1. Apple’s prescribed resolution is to rebuild the app with the updated Xcode. Requiring every user to update their operating system to 26.4 is not the appropriate developer-side fix.

Recommended resolution

1. Check the active Xcode

xcodebuild -version
xcode-select -p

If the command reports Xcode 26.4, install Xcode 26.4.1 or later. On machines and CI systems with multiple installations, also confirm that the updated developer directory is actually active.

2. Select Xcode 26.4.1 or later

sudo xcode-select -s /Applications/Xcode.app
xcodebuild -version

Adjust the path for your installation. In CI, update the selected image, DEVELOPER_DIR, or Xcode-version setting as well.

3. Create a new archive

xcodebuild clean
xcodebuild archive \
  -scheme MyApp \
  -configuration Release \
  -archivePath build/MyApp.xcarchive

Do not merely re-sign or re-upload an archive that Xcode 26.4 already produced. Compile and link again with Xcode 26.4.1 or later, then distribute the newly generated binary.

4. Test on a pre-26.4 device

Launch the rebuilt app on your minimum supported OS and on a 26.3.x environment if available. Verify that the app starts and that no crash report references MetricKit.mxSignpost.

Workarounds

If you cannot adopt Xcode 26.4.1 immediately, temporarily producing the release build with Xcode 26.3.x avoids using the affected 26.4 toolchain. This is a bridge, not the final resolution. Continuing to distribute an archive made with Xcode 26.4, or asking users to update only their OS, leaves supported older systems exposed.

Removing MetricKit usage may seem like another workaround, but Apple’s confirmed fix is to rebuild with Xcode 26.4.1. A simple #available check may not prevent a loader failure that occurs before application code executes.

Verification checklist

Confirm Xcode 26.4.1 or later with xcodebuild -version.
Discard the affected archive and create a new one.
Launch the new build on supported iOS, macOS, and visionOS versions below 26.4.
Confirm that crash logs no longer contain dyld and MetricKit.mxSignpost.
Check that TestFlight or internal distribution contains the new build number and binary.

Cautions

Updating a developer workstation is not enough if CI still builds with Xcode 26.4.
Deleting DerivedData alone does not fix the binary; a rebuild with the corrected toolchain is required.
Testing only on OS 26.4 can hide the problem. Include the minimum supported OS in launch testing.
MetricKit is Apple’s framework for performance metrics and diagnostics. This known issue concerns Xcode 26.4 build output, not the general design of your MetricKit instrumentation.

Summary

dyld: Symbol not found: MetricKit.mxSignpost is a confirmed Xcode 26.4 compatibility failure affecting MetricKit apps on operating systems earlier than 26.4. Upgrade the build environment to Xcode 26.4.1 or later, create a fresh archive, redistribute it, and verify launch on older supported systems.