iOS simulator native asset hook returns the same fat dylib for arm64 and x86_64 Flutter builds

[alealv]

Summary

When sqlite_vector is used from a Flutter app on iOS simulator, the native-asset build hook returns the same fat simulator dylib for both arm64 and x86_64 targets. Flutter then tries to package those outputs together and fails during the simulator build.

Package Version

• sqlite_vector 0.9.85

Environment

• Flutter 3.41.2
• Xcode 26.1.1
• iOS simulator build (just build ios --simulator --no-codesign in our case, but this is a normal Flutter iOS simulator build)

Failure

Flutter fails during iOS simulator packaging with an error like:

Target install_code_assets failed: Error: Failed to create universal binary:
fatal error: .../usr/bin/lipo: .../vector_ios-sim.dylib and .../vector_ios-sim.dylib have the same architectures (x86_64) and can't be in the same fat output file

Root Cause

The current hook returns native_libraries/ios-sim/vector_ios-sim.dylib for every iOS simulator build, regardless of target architecture:

• simulator arm64 build -> ios-sim/vector_ios-sim.dylib
• simulator x86_64 build -> ios-sim/vector_ios-sim.dylib

That file is already a fat dylib containing both architectures, so Flutter ends up trying to combine duplicate inputs.

We confirmed this by inspecting the hook outputs for both simulator targets: both originally pointed at the same vector_ios-sim.dylib.

What Fixed It Locally

We patched the build hook so that for iOS simulator builds it thins the fat dylib per target architecture and emits an arch-specific output file:

• arm64 -> vector_ios_sim_arm64.dylib
• x86_64 -> vector_ios_sim_x86_64.dylib

After that, the Flutter iOS simulator build succeeded.

Suggested Fix

In hook/build.dart, for OS.iOS + simulator targets, emit an architecture-specific dylib instead of returning the same fat simulator binary for every target.

If helpful, I can open a PR with the hook change we tested locally.

[marcobambini]

Hi @alealv yes please open a PR so we can better take a look at the fix, thanks!

[alealv]

Small follow-up: it looks like the reason pub.dev is still stuck at 0.9.85 is that the Flutter publish workflow is failing for the tag releases.

I checked the 0.9.92 run here:
https://github.com/sqliteai/sqlite-vector/actions/runs/22264167954

The failing step is assemble and publish flutter package, and the relevant pub validation errors are:

• pubspec.yaml is modified in git
• packages/flutter/CHANGELOG.md does not mention 0.9.92

So the GitHub release exists, but the pub.dev publish step never completes. Thought it was worth pointing out explicitly in case it helps unblock the release.

[marcobambini]

Thanks, @alealv. We are working on a fix; @Gioee should trigger the new package.

[Gioee]

Hi @alealv , thanks for the issue and the helpful PR! I've just fixed the workflow and now the latest released version on pub.dev is the 0.9.93 with your fix included!