[Bug]: [iOS] "Could not create a sandbox extension" on Clean SPM Project with Xcode 16.4 (16F6)

[ArtifexRota]

Capacitor Version

💊 Capacitor Doctor 💊

Latest Dependencies:

@capacitor/cli: 7.4.3
@capacitor/core: 7.4.3
@capacitor/android: 7.4.3
@capacitor/ios: 7.4.3

Installed Dependencies:

@capacitor/android: not installed
@capacitor/cli: 7.4.3
@capacitor/core: 7.4.3
@capacitor/ios: 7.4.3

[success] iOS looking great! 👌

Other API Details

npm version: 11.5.1
node version: v24.7.0
pod version: 1.16.2

macOS Version: Sequoia 15.3.1
Xcode Version:16.4 (16F6)
iOS Version on physical device: 18.6.2

Platforms Affected

• iOS
• Android
• Web

Current Behavior

When running a clean, minimal Capacitor 7 SPM project (created with npx cap add ios --packagemanager SPM) on a physical iOS device, the Xcode console logs the error Could not create a sandbox extension for .... This seems to prevent native plugins like Push Notifications from working correctly in a full application.

Expected Behavior

The app should start without the sandbox extension error.

Project Reproduction

https://github.com/ArtifexRota/capacitor-sandbox-bug-repro

Additional Information

Project is created with legacy Xcode 8.0 format, updating it does not solve the issue

[ArtifexRota]

Update: I've also confirmed that I am using the latest LTS version of Node.js (v22.19.0). I completely cleaned my node_modules and reinstalled all dependencies. I then completely removed the ios directory and regenerated it using npx cap add ios --packagemanager SPM. All configurations in Xcode (Signing, Capabilities, Info.plist) were done manually on the clean project. The Could not create a sandbox extension error still persists even in the minimal reproduction project under these conditions.

[ArtifexRota]

Update:
Updated now to
iOS 26.0
macOS Tahoe 26.0
Xcode Version 26.0.1 (17A400)
The Issue is still there.

[scottywm]

I literally just upgraded my Mac to this new version you speak of.

I hope I don't run into these issues too.

TBH I'm feeling very uncomfortable with capacitor these days, the community and team don't seem to be fixing these new issues and there is almost zero engagement from the ionic team.

Have you tried creating a ticket with the ionic team to resolve the issue?

[ArtifexRota]

The Key Finding: The issue is NOT specific to Capacitor.

I created a brand new, 100% clean Apache Cordova project. After configuring signing, cordova run ios fails with the exact same Could not create a sandbox extension error in the device console.

This is the final piece of evidence in a long investigation. Here is the full summary of what has been proven:

Framework Agnostic: The error occurs with both Capacitor and Cordova, pointing to a systemic problem with how hybrid apps are handled.

Capacitor Version Agnostic: The error is not a recent regression. It persists across all tested versions: v6.2.0, v7.4.3, and v8.0.0-alpha.1.

Dependency Manager Agnostic: The error occurs regardless of the dependency manager used. I have tested and reproduced the failure with both SPM and CocoaPods.

Device Agnostic: This is not a faulty state on a single iPhone. The failure was reproduced on two separate, distinct physical iPhones.

System Agnostic: The issue spans multiple OS generations. It occurred on my previous macOS Sequoia / Xcode 16 setup and persists on my current brand new, 1-month-old Mac after a full OS reinstall of macOS Tahoe / Xcode 26 with a clean user profile.

The Control Case: A 100% pure native Xcode project (File > New Project) works perfectly on the same machine, with the same signing identity, and on the same devices.

Conclusion:
The problem is a deep, systemic bug in Apple's developer toolchain (xcodebuild, sandboxd) that incorrectly denies fundamental permissions to any hybrid app built via an external CLI.
I have escalated this to Apple with a Code-Level Support ticket. I am leaving this issue open for visibility for other developers who will inevitably hit this wall. I will report back here if Apple provides a solution or workaround.

[ArtifexRota]

The Final Test: Tauri Works Perfectly

After proving the issue persists across all Capacitor/Cordova versions, I created a brand new, 100% clean Tauri v2 project.
The Result: The Tauri app builds and runs perfectly on my physical device. The Could not create a sandbox extension error does NOT occur.

This is the final, definitive proof. The problem lies specifically with the core architecture of Capacitor/Cordova and how it interacts with modern iOS/Xcode security features.

Full Summary of Proven Facts:

Framework Specificity: The error occurs with both Capacitor (v6, v7, v8-alpha) and Cordova, but NOT with Tauri.

System Agnostic: The failure was reproduced on two different Macs (M4 local, M2 cloud) and two different macOS/Xcode generations (Sequoia/16 and Tahoe/26).

Device & iOS Agnostic: The failure was reproduced on two different iPhones across four different stable iOS versions (18.x and 26.x).

Account Agnostic: The failure persisted even when signing with a brand new, clean Apple ID.

Control Case: A pure native Xcode app and the iOS Simulator always work correctly.

Conclusion:
This is a fundamental incompatibility between the Capacitor/Cordova architecture and Apple's sandbox service on physical devices running modern iOS versions. Since Tauri works, it proves my development environment is healthy and capable of building hybrid apps.

I will be migrating my project to Tauri to meet my deadline. I am leaving this issue open for visibility, as it seems to be a critical, blocking issue for anyone in a similar system environment. I have also escalated this to Apple with a Code-Level Support ticket.

[ArtifexRota]

Final Update - Root Cause Identified:
The issue is a regression introduced in the iOS 18.6.2 WebKit security update. The stricter sandbox rules now prevent the Capacitor/Cordova architecture (which uses a local web server) from acquiring the necessary sandbox extensions at launch. This is proven by the fact that Tauri, which uses a different IPC architecture, works perfectly on the exact same system. This is a critical compatibility break for all standard hybrid apps.