AltStore crashes on launch on iOS/ipadOS 26.4

After updating to iOS / iPadOS 26.4, AltStore crashes on launch.

It seems that they fixed the Windows version of AltServer to overcome this issue:
https://faq.altstore.io/release-notes/altserver#altserver-1.7.4-windows-only

Has anyone else experienced this or found a fix?

Confirmed and fixed on iOS 26.5 (iPhone 15 Pro). Posting the full diagnosis + a working fork in case it helps.

Root cause. App installs but crashes instantly on launch, no crash report. idevicesyslog during launch shows the kernel rejecting the signature:

kernel  TXM [Error]: CodeSignature: selector: 24 | 0x53 | 0x23 | 9
SpringBoard(FrontBoard)  [app<…>:-1] Now flagged as pending exit for reason: Bootstrap failed

AMFI accepts the profile (AMFI: profile validated the code signature), but the kernel's TXM rejects the signature ldid produces. iOS 26 enforces several things ldid (vendored ~2022) gets wrong, and I verified each by diffing against a known-good rcodesign signature:

DER entitlements emitted as a bare ASN.1 SET instead of [APPLICATION 16] { INTEGER version, [CONTEXT 16] {…} } (and DER booleans as 0x01 instead of 0xFF).
A legacy SHA-1-primary CodeDirectory instead of SHA-256-only.
Empty designated requirements (app + every framework).
An older CodeResources resource-sealing format.

You can patch ldid for the first three (I did — the Mach-O signatures become byte-identical to rcodesign), but CodeResources still diverges, so with stricter signing the install fails (0xe8008016 → 0xe8008001) instead of crashing at launch. (An RFC3161 timestamp is not required — rcodesign --timestamp-url none installs fine.)

Fix that works. Rather than reimplement modern codesign inside ldid, sign with rcodesign (apple-codesign) instead. AltServer already prepares the bundle (embeds the profile, computes entitlements) and builds a cert chain p12 — so in AltSign's Signer::SignApp I just replaced the ldid::Sign(...) call with a shell-out to rcodesign sign. Everything else (auth, certificate, provisioning, install) is unchanged.

👉 Fork + details: https://github.com/ondrej-simon/AltServer-Linux — see IOS26.md

With that, AltServer installs and launches directly on iOS 26 (Installation Succeeded), no extra steps. Requirements: rcodesign + openssl on the host (path via ALTSERVER_RCODESIGN).

I switched to sidestore and NEVER looked back, everything works and on-device-refresh

Second data point plus a fix that keeps ldid in-process, no external signer needed.

Symptom on iOS 27 / 26.4+: install succeeds, app flashes and exits. idevicesyslog:

kernel  AMFI: cmsBlobVerifyWithAgilityHash failed ... Unrecoverable CT signature issue
launchd Bad executable (85)

Root cause. I built the vendored ldid.cpp (AltServer-Windows pinned at 071b1dd, 2022) as a CLI, signed a test binary and dumped the CMS with openssl cms -cmsout -print. The hash-agility attribute 1.2.840.113635.100.9.2 is present but carries the SHA-256 CodeDirectory hash truncated to 20 bytes; CoreTrust expects the full 32, so the agility hash never matches and the signature is rejected. The designated requirement is also empty. DER entitlements, the SHA-256 alternate CodeDirectory and CD version 0x20400 are already emitted, so those were not the blocker here.

Fix. Riley already fixed this for AltServer for Windows 1.7.4 in rileytestut/AltServer-Windows commit 62a7a2b "[ldid] Updates ldid to match AltStore + AltServer macOS' version" (branches 26.4_fix / 1.7.4 / develop); this repo's upstream_repo submodule never picked it up. Only ldid/ldid.cpp and ldid/ldid.hpp change, plus two lines in AltSign/Signer.cpp: ldid::Sign now takes a single ldid::Progress object, and DiskFolder needs a trailing "/" (not "\\", the Linux source rewriter doesn't translate backslashes). It compiles unchanged against the existing Alpine/LibreSSL builder image. With it, AltStore installed from Linux over Wi-Fi launches on iOS 27 with zero CoreTrust errors in the log.

Fork with this plus the September 2026 Apple ID sign-in fix (com.apple.dt.Xcode → com.apple.akd in client-info, AuthKit User-Agent, no keep-alive, cf. #135) and netmuxd ≥ 0.3 address support: https://github.com/jaakkopalvaila/AltServer-Linux (branch ng, see README-NG.md). Submodules point at patched forks, so git clone --recursive builds as-is.