We maintain a macOS product whose installer uses custom InstallerSection plugin bundles to show configuration panes during install. Starting with macOS 27 beta 6, all of our plugins stopped loading in Installer.app — the panes never appear and the install fails because our preinstall step depends on data the panes collect. The exact same .pkg works on macOS 26.6, and per thread 842811 the same bundles were fine on 27 betas 1–4(I have tested it from beta 6 onwards).
While investigating we found what looks like the underlying cause, and it's reproducible by hand.
THE FINDING
During a failing install, look inside the extracted plugin bundle while the Installer window is still open:
ls -la /private/tmp/com.apple.installer*/<Plugin>.bundle/Contents/
That layout fails code-signature validation. You can reproduce the failure manually, no Installer involved:
codesign -vvv "/private/tmp/com.apple.installer"*/<Plugin>.bundle → <Plugin>.bundle: Too many levels of symbolic links
WHAT THE SYSTEM LOGS SHOW
amfid rejects the plugin executable:
/private/tmp/com.apple.installerXXXXXX/<Plugin>.bundle/Contents/MacOS/<Plugin> not valid: Error Domain=AppleMobileFileIntegrityError Code=-420 "The signature on the file is invalid"
with repeated "UNIX error exception: 62" (errno 62 = ELOOP, too many levels of symbolic links) in backtraces through BundleDiskRep::component → SecStaticCode::component → validateNonResourceComponents → staticValidateCore, and "Code failed basic validity check (error: 100062)".
For a Developer ID–signed plugin the kernel then treats it as fatal:
AMFI: When validating /private/tmp/com.apple.installerXXXXXX/<Plugin>.bundle/Contents/MacOS/<Plugin>: The code contains a Team ID, but validating its signature failed. mac_vnode_check_signature: ... code signature validation failed fatally check_signature[pid: N]: error = 1
The plugin is never dlopen'd and the pane never appears.
QUESTIONS
- Is there a way to get Installer to deploy the bundle with real files — or any other workaround?
Note : I have Filed via Feedback Assistant as FB24601496; this overlaps FB24415432 / thread https://developer.apple.com/forums/thread/842811, which we've cross-referenced
I have experienced this issue on latest Beta 8 build also -27.0 Beta (26A5425a)