FSKit passthrough sample fails to mount

You’re code signing your app and app extension, right?

There was a very similar report last week that was caused by a failure to sign.

The logs show the following

That’s quite hard to read. See tip 5 in Quinn’s Top Ten DevForums Tips for advice on how to post preformatted text.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Yes, both are signed

Executable=/Users/alexf/Library/Developer/Xcode/DerivedData/Passthrough-fmtxodvbsknmqegwvscnzsczlopk/Build/Products/Debug/PassthroughAppEx.appex/Contents/MacOS/PassthroughAppEx
Identifier=com.example.apple-samplecode.PassthroughXXXXXXXX.AppEx
Format=bundle with Mach-O thin (arm64)
CodeDirectory v=20400 size=476 flags=0x0(none) hashes=3+7 location=embedded
Hash type=sha256 size=32
CandidateCDHash sha256=9abcde7d8b79d23164600c46c55cdace7136690a
CandidateCDHashFull sha256=9abcde7d8b79d23164600c46c55cdace7136690aecb06f89082b53853a045b76
Hash choices=sha256
CMSDigest=9abcde7d8b79d23164600c46c55cdace7136690aecb06f89082b53853a045b76
CMSDigestType=2
CDHash=9abcde7d8b79d23164600c46c55cdace7136690a
Signature size=4781
Authority=XXXXXXXXXXXXX
Authority=Apple Worldwide Developer Relations Certification Authority
Authority=Apple Root CA
Signed Time=17 Mar 2026 at 15:00:17
Info.plist entries=21
TeamIdentifier=XXXXXXXX
Sealed Resources version=2 rules=13 files=3
Internal requirements count=1 size=216```

Attaching the logs again:

Filtering the log data using "subsystem == "com.apple.FSKit" OR process CONTAINS[c] "samplecode""
Timestamp               Ty Process[PID:TID]
2026-03-17 15:15:51.832 I  mount[16111:d88caa] [com.apple.FSKit:default] FSClient setting up connection to fskitd
2026-03-17 15:15:51.833 Db fskitd[589:d88a5f] [com.apple.FSKit:default] -[liveFilesMountServiceDelegate listener:shouldAcceptNewConnection:]: start
2026-03-17 15:15:51.833 Df fskitd[589:d88a5f] [com.apple.FSKit:default] Incomming connection, entitled 0
2026-03-17 15:15:51.833 Db fskitd[589:d88a5f] [com.apple.FSKit:default] -[liveFilesMountServiceDelegate listener:shouldAcceptNewConnection:]: accepting connection
2026-03-17 15:15:51.833 Df fskitd[589:d88a5f] [com.apple.FSKit:default] Hello FSClient! entitlement no
2026-03-17 15:15:51.834 Df mount[16111:d88caa] [com.apple.FSKit:default] Setting remote protocol to all XPC
2026-03-17 15:15:51.834 Df fskitd[589:d88a5f] [com.apple.FSKit:default] About to get current agent for 501
2026-03-17 15:15:51.834 I  fskitd[589:d88a5f] [com.apple.FSKit:default] About to call to fskit_agent
2026-03-17 15:15:51.835 I  fskit_agent[10123:d877d9] [com.apple.FSKit:default] Getting extensions
2026-03-17 15:15:51.836 Db fskitd[589:d88a5f] [com.apple.FSKit:default] -[fskitdAgentManager currentExtensionForShortName:auditToken:replyHandler:]_block_invoke: Found extension for fsShortName (<private>)
2026-03-17 15:15:51.837 I  fskitd[589:d88a5f] [com.apple.FSKit:default] Probe starting on <private>
2026-03-17 15:15:51.837 Db fskitd[589:d87c31] [com.apple.FSKit:default] -[FSResourceManager getResourceState:]:found:<private>
2026-03-17 15:15:51.837 Db fskitd[589:d87c31] [com.apple.FSKit:default] -[FSResourceManager addTaskUUID:resource:]:<private>: Adding task (<private>)
2026-03-17 15:15:51.837 Df fskitd[589:d87c31] [com.apple.FSKit:default] About to get current agent for 501
2026-03-17 15:15:51.837 I  fskitd[589:d87c31] [com.apple.FSKit:default] About to call to fskit_agent
2026-03-17 15:15:51.837 I  fskit_agent[10123:d877d9] [com.apple.FSKit:default] Getting extensions
2026-03-17 15:15:51.838 Db fskitd[589:d87c31] [com.apple.FSKit:default] -[fskitdXPCServer getExtensionModuleFromID:forToken:]_block_invoke: Found extension <private>, attrs <private>
2026-03-17 15:15:51.838 Db fskitd[589:d87c31] [com.apple.FSKit:default] applyResource starting with resource <private> kind 4```