Hi @circleci team and community,
I am consistently running into Simulator device failed to launch errors when running my iOS unit and UI tests as part of my Fastlane lane on CircleCI. The message is:
Simulator device failed to launch com.apps.app. The request was denied by service delegate (SBMainWorkspace)… Launchd job spawn failed
Exit status: 65
What’s puzzling is:
The tests run perfectly on my local Mac, with the same Xcode version (16.4), same Fastlane config, and the same simulator (iPhone 16 Pro with iOS 17.5 or 18.5).
My Fastlane Lane
desc 'Perform Unit and UI Tests'
lane :test
do
scan(
scheme: 'test-development',
clean: true,
skip_detect_devices: false,
sdk: 'iphonesimulator',
device: 'iPhone 16 Pro',
should_zip_build_products: true,
code_coverage: true,
reset_simulator: true,
only_testing: 'AppTests,AppUITests',
max_concurrent_simulators: 5,
concurrent_workers: 5
)
end
My CircleCI Job
jobs:
test:
resource_class: m4pro.large
macos:
xcode: 16.4.0
working_directory: /Users/distiller/project
environment:
FL_OUTPUT_DIR: output
TERM: xterm
steps:
- checkout
- run: bundle update --bundler
- run: bundle install
- run: gem install specific_install
- run: gem specific_install -l https://github.com/Soomgo-Mobile/fastlane.git -b patch-1
- run: ./carthage.sh update --use-ssh --platform iOS --use-xcframeworks
- run:
name: Build and run test
command: bundle exec fastlane test
no_output_timeout: 45m
- store_artifacts:
path: /var/folders/6y/gy9gggt14379c_k39vwb50lc0000gn/T/
destination: Logs
- store_test_results:
path: output/scan
The Error Details
Every run ends with lines like:
Simulator device failed to launch com.apps.app. The request was denied by service delegate (SBMainWorkspace). The operation couldn’t be completed.
Launch failed. Launchd job spawn failed.
Exit status: 65
What I Have Tried
-
Booting and erasing all simulators before tests (
simctl shutdown all,simctl erase all) -
Pre-creating simulators with
simctl create(using both names and service IDs) -
Explicitly booting the intended simulator and waiting after boot with
sleep 10 -
Passing both simulator display name and UDID to Fastlane scan
-
Ensured all code signing is disabled for simulator builds
-
Using both latest (
iPhone 16 Pro, iOS 18.5) and previous (iPhone 15 Pro, iOS 17.5) device/runtime combinations -
Running the same steps on my local machine (it always works locally!)
My Problem
-
Tests fail only on CircleCI, never locally.
-
The root cause always seems to be SBMainWorkspace denying the launch, causing the simulator/test runner to never start.
-
All workarounds (full simulator erase, custom boot, different devices/runtimes, explicit Fastlane flags) haven’t made any difference.
Request for Help
Is anyone else experiencing this with recent CircleCI macOS images/Xcode releases?
Are there any CircleCI known issues/workarounds/fixes for this persistent simulator launch failure with SBMainWorkspace?
Could this be tied to the CircleCI executor’s resource limits, image corruption, or Apple Silicon/Rosetta issues?
Any help or suggestions would be massively appreciated—I’ve spent significant time troubleshooting, and it’s hurting my team’s velocity.
Thank you!