[BUG] Apktool 3.0.1 fails to rebuild Instagram 417 base (aapt2 layout reference error)

[Noctharion]

Information

1. Apktool Version (apktool -version) - 3.0.1
2. Operating System (Mac, Linux, Windows) - Windows 11 (PowerShell)
3. APK From? (Playstore, ROM, Other) - Other (Instagram 417.0.0.54.77 extracted from XAPK split bundle, using base com.instagram.android.apk)
4. Java Version (java --version) - java 25.0.2 2026-01-20 LTS

---

### Stacktrace/Logcat

C:\apktools>apktool b com.instagram.android
I: Using Apktool 3.0.1 on com.instagram.android.apk with 8 threads
I: Smaling smali folder into classes.dex...
I: Smaling smali_classes10 folder into classes10.dex...
I: Smaling smali_classes11 folder into classes11.dex...
I: Smaling smali_classes12 folder into classes12.dex...
I: Smaling smali_classes13 folder into classes13.dex...
I: Smaling smali_classes15 folder into classes15.dex...
I: Smaling smali_classes14 folder into classes14.dex...
I: Building resources with aapt2...
W: com.instagram.android\res\values-h640dp\layouts.xml:3: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values-h640dp\layouts.xml: error: file failed to compile.
W: com.instagram.android\res\values-land\layouts.xml:3: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values-land\layouts.xml:4: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values-land\layouts.xml: error: file failed to compile.
W: com.instagram.android\res\values-sw600dp\layouts.xml:3: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values-sw600dp\layouts.xml:4: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values-sw600dp\layouts.xml: error: file failed to compile.
W: com.instagram.android\res\values\layouts.xml:3: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:4: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:5: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:6: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:7: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:8: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:9: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:10: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:11: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:12: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:13: error: invalid value for type 'layout'. Expected a reference.
W: com.instagram.android\res\values\layouts.xml:14: error: invalid value for type 'layout'. Expected a reference.
Exception in thread "main" brut.androlib.exceptions.AndrolibException: brut.common.BrutException: Execution failed (exit code = 1): [C:\Users\danie\AppData\Local\Temp\aapt2_52179403741890999433921575529712792617.tmp, compile, --dir, com.instagram.android\res, --legacy, -o, com.instagram.android\build\resources.zip]
at brut.androlib.res.AaptInvoker.invoke(SourceFile:90)
at brut.androlib.ApkBuilder.buildResources(SourceFile:357)
at brut.apktool.Main.main(SourceFile:92)
Caused by: brut.common.BrutException: Execution failed (exit code = 1): [C:\Users\danie\AppData\Local\Temp\aapt2_52179403741890999433921575529712792617.tmp, compile, --dir, com.instagram.android\res, --legacy, -o, com.instagram.android\build\resources.zip]
at brut.util.OS.exec(SourceFile:147)
at brut.androlib.res.AaptInvoker.invoke(SourceFile:87)
... 2 more
shouldn't happen: null
shouldn't happen: null
shouldn't happen: null
shouldn't happen: null
shouldn't happen: null
shouldn't happen: null
shouldn't happen: null
com.instagram.android\smali_classes15\X\WFE.smali[1,0] required (...)+ loop did not match anything at input ''
com.instagram.android\smali_classes12\X\PSv.smali[1,0] required (...)+ loop did not match anything at input ''
com.instagram.android\smali_classes11\X\PlB.smali[1,0] required (...)+ loop did not match anything at input ''
com.instagram.android\smali\X\4um.smali[1,0] required (...)+ loop did not match anything at input ''
com.instagram.android\smali_classes10\X\MTd.smali[1,0] required (...)+ loop did not match anything at input ''
com.instagram.android\smali_classes13\X\RSJ.smali[1,0] required (...)+ loop did not match anything at input ''
com.instagram.android\smali_classes14\X\TEs.smali[1,0] required (...)+ loop did not match anything at input ''

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Steps to Reproduce

1. apktool d com.instagram.android.apk
2. apktool b com.instagram.android

(Build fails without making any modifications)

---

Frameworks

Not from an OEM ROM. Standard Play Store Instagram split bundle.

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APK

Instagram version 417.0.0.54.77 (base split extracted from XAPK).
Can be shared if needed, uptodown source.

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Questions to ask before submission

1. Have you tried apktool d, apktool b without changing anything? Yes
2. If you are trying to install a modified apk, did you resign it? Not applicable (build fails before signing)
3. Are you using the latest apktool version? Yes (3.0.1)

[Noctharion]

When decoding the same APK using --no-res (apktool d com.instagram.android.apk --no-res) and rebuilding without modifying anything, the build completes successfully.

This suggests the issue is specifically related to resource decoding/recompilation (aapt2 stage), not smali processing or general APK rebuilding.

[IgorEisberg]

I'll improve the output of weird values formats for file resource types, but it's not going to help in your case.
The layouts of this app are encoded in assets/layouts.bin.xz while resources.arsc keeps special references as strings.

<item type="layout" name="ab_test_media_thumbnail_preview_item_layout" format="string">L|BF64C|3F0|6543</item>
<item type="layout" name="ac_transition_second_level_top_banner" format="string">L|BC764|5C4|1056</item>
...

This is a completely custom-made packing method. Having strings for layout resources is not allowed by aapt2, even if we output them as <item> tags with a format="string" attribute, so you won't be able to rebuild resources.arsc either way, unless some changes are made directly to aapt2. @iBotPeaches

[iBotPeaches]

Its very interesting to me how Instagram is able to do this. You can obviously learn from the previous Facebook implementations where they had a custom dex loader, but at the resource level that would suggest their own rendering engine which I guess they have plenty of experience with in React Native, folly, hermes, redex, yoga.

So Android must do its part, then Instagram takes over with the layout reference to load via their own loader.

[IgorEisberg]

Yeah, we'll have to accept the fact that developers are getting creative. Some apps are even developed with Rust so they have no dex files at all...
Anyway, since layout is not one of the resource types that has implied compatible formats:
https://cs.android.com/android/platform/superproject/main/+/main:frameworks/base/tools/aapt2/ResourceParser.cpp;l=510
It doesn't pass the check in the main case for can_be_item:
https://cs.android.com/android/platform/superproject/main/+/main:frameworks/base/tools/aapt2/ResourceParser.cpp;l=670-671
Then fails at the fallback case for can_be_item:
https://cs.android.com/android/platform/superproject/main/+/main:frameworks/base/tools/aapt2/ResourceParser.cpp;l=721
Because that fallback only expects a reference: ParseXml(parser, android::ResTable_map::TYPE_REFERENCE, kNoRawString)

[IgorEisberg]

@iBotPeaches I don't have push access to your platform_frameworks_base repo, so I'll write the potential patch here.
Didn't test it (it's useless for me) but this is a rather simple thing to patch.

Here: https://github.com/iBotPeaches/platform_frameworks_base/blob/main/tools/aapt2/ResourceParser.cpp#L716
Change:

      out_resource->value = ParseXml(parser, android::ResTable_map::TYPE_REFERENCE, kNoRawString);
      if (!out_resource->value) {
        diag_->Error(DiagMessage(out_resource->source)
                     << "invalid value for type '" << *parsed_type << "'. Expected a reference");
        return false;
      }

To:

      // Only enforce a reference when there is no explicit format.
      if (resource_format == 0u) {
        out_resource->value = ParseXml(parser, android::ResTable_map::TYPE_REFERENCE, kNoRawString);
        if (!out_resource->value) {
          diag_->Error(DiagMessage(out_resource->source)
                       << "invalid value for type '" << *parsed_type << "'. Expected a reference");
          return false;
        }
      } else if (!ParseItem(parser, out_resource, resource_format)) {
        return false;
      }

[iBotPeaches]

Invited you to that repo - branches are a mess, but I think apktool-3.0.x is the main one atm.

[Noctharion]

Thanks for the investigation and explanation.

I understand now that the failure happens because aapt2 enforces layout resources to be references, while Instagram stores them as string tokens pointing to their custom loader (layouts.bin.xz).

If any experimental changes or patches are made on the aapt2 / Apktool side regarding this behavior, I don't mind testing them on my side and providing feedback or results.

[IgorEisberg]

If any experimental changes or patches are made on the aapt2 / Apktool side regarding this behavior, I don't mind testing them on my side and providing feedback or results.

The commit is already up, but new aapt2 binaries aren't expected until the next Apktool release.
https://github.com/iBotPeaches/platform_frameworks_base/commits/apktool-3.0.x/

[Noctharion]

If any experimental changes or patches are made on the aapt2 / Apktool side regarding this behavior, I don't mind testing them on my side and providing feedback or results.

The commit is already up, but new aapt2 binaries aren't expected until the next Apktool release. https://github.com/iBotPeaches/platform_frameworks_base/commits/apktool-3.0.x/

i will wait for new version, thank you

[REAndroid]

Hi @iBotPeaches
I did a few research few years ago on facebook (meta) resource encodings. I don't know it worth to give attention but I would like to share my findings with you.

1. Layouts

Located under assets/layouts.bin.xz, after un-compressing from xz we get layouts.bin. This file is a group of multiple standard binary xml files placed one after another as an array. The offset and size information is encoded as string in values/layout entry.
<layout name="res_name">L|{OFFSET}|{SIZE}|{CRC32_LAST_4HEX_DIGITS}</layout>
e.g
<item type="layout" name="ab_test_media_thumbnail_preview_item_layout" format="string">L|BF64C|3F0|6543</item>

0xBF64C : Offset of bin xml file on layout.bin (783948)
0x3F0 : Size of bin xml file (1008 bytes)
0x6543 : Last four digits of crc32 for bin xml file

2. Strings
   Located under assets/strings/{LOCALE}.frsc. This files begins with magic bytes of FRSC similar to ARSC StringPool but without styled strings and resource id map.

3. Drawables
   Used to have remote drawables that points the download url of images, but I am not seeing on recent versions.

NB: After unpacking we have to modify also resource overriding from dex side. Here is sample resource unpacked instagram.

[Daniel-1647]

@iBotPeaches @IgorEisberg Will it be possible for you to provide the aapt2 binary here before the next release of APKTOOL?
Thank you

[iBotPeaches]

If you see the PR that adds it you can pluck it from that. I synced the AOSP tree, updated our frameworks/base fork to latest and compiled and it failed. So I have some more work to do