Flutter Debug Mode Blocked on iOS 26 Devices — What Developers Need to Know

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If you've recently updated your iPhone or iPad to iOS 26, you might have been greeted by this frustrating error while running your Flutter…

If you've recently updated your iPhone or iPad to iOS 26, you might have been greeted by this frustrating error while running your Flutter app:

mprotect failed: 13 (Permission denied)

Suddenly, hot reload doesn't work, debug builds fail, and your once-smooth workflow feels broken.
Don't worry — you're not alone. This issue is affecting developers across the Flutter community worldwide.

Let's break down what's happening, why it's happening, and how you can keep building without losing productivity.

What's Actually Going On

Starting with iOS 26, Apple has introduced stricter memory protection rules as part of its ongoing effort to improve app security.

Unfortunately, these changes conflict with how Flutter's Dart VM works in debug mode.

Here's the technical bit in plain English:

• Flutter's debug builds rely on Just-In-Time (JIT) compilation.
• JIT needs to modify memory pages at runtime to execute new code (this is what enables hot reload).
• iOS 26 now blocks that behavior for security reasons.

When the Dart VM tries to toggle executable memory during debug, iOS simply says "no" — resulting in mprotect failed: 13 (Permission denied).

The restriction only affects real devices.
Simulators continue to work fine because they don't enforce the same memory security.

What You Can Do Right Now

Here's how to adapt your workflow without losing momentum:

1. Use Profile Mode for On-Device Testing

You can still run Flutter apps on real devices in AOT (Ahead-of-Time) mode:

flutter run --profile

Profile mode offers near-production performance and supports some diagnostics, just without hot reload.

2. Continue Debugging in the iOS Simulator

The iOS simulator still supports full debug mode, including hot reload, hot restart, and breakpoints.
This is the best environment for most of your daily development work.

3. Upgrade to Flutter 3.35 or Later

If your project is using an older version, update your SDK to improve compatibility with iOS 26:

flutter upgrade

Debug Mode Feels Slower After Upgrading? You're Not Imagining It.

Many developers who upgraded to the latest Flutter version have noticed that debug builds feel slower, especially when running on iOS 26 simulators.

Build times are longer, hot reloads lag, and even simple UI updates take a few extra seconds.

Here's why:

1. Stricter iOS 26 Sandbox and Security Checks
   Each build now runs with additional entitlements and memory checks, adding overhead.
2. Flutter's Updated Tooling (3.35+)
   The Flutter team introduced new safeguards to align with Apple's changes — these extra layers slightly slow down build processes.
3. Xcode 16 Debugger Changes
   Apple's updated debugger performs deeper runtime analysis for safety, increasing run-time preparation time.
4. Simulator Overhead
   The iOS 26 simulators, especially on Apple Silicon Macs, now use more aggressive memory isolation, increasing CPU usage.

Recommended Development Workflow

Until the Flutter team introduces new tooling, here's the best workflow for iOS 26:

1. Develop and debug in simulator (hot reload available).
2. Test performance and device-specific behavior in profile mode.
3. Use release mode for QA, distribution, and App Store builds.
4. Stay up to date with the Flutter release notes and GitHub discussions.

Why Apple Made This Change

This wasn't targeted at Flutter specifically — it's part of Apple's broader push to strengthen app security.

By preventing dynamic memory execution, Apple reduces the risk of runtime code injection and malicious behavior.
Unfortunately, that same restriction also breaks legitimate JIT-based workflows like Flutter's debug mode.

It's frustrating, yes — but it's a trade-off between developer flexibility and platform security.