We're testing the SimpleURLFilter sample project on macOS. The filter configuration saves successfully, but when enabling the filter, it transitions to .stopped with NEURLFilterManager.Error error 10 (extensionCancelled). System logs from neagent: neagent +[NEBloomFilter mmapToFile:data:dataLength:numberOfBits:numberOfHashes:murmurSeed:tag:]: NEBloomFilter - failed to open mmap file /private/var/db/urlPrefilter/com.apple.networkextension.url-prefilter-data.temp.<bundle-id> <errno 13 - Permission denied> neagent <NEAgentURLFilterExtension>: -[NEAgentURLFilterExtension startURLFilter]_block_invoke - Failed to save first fetch of pre-filter data The directory exists but is owned by root with 755: drwxr-xr-x 2 root wheel 64 Jun 18 14:42 /private/var/db/urlPrefilter/ Changing permissions to 777 doesn't help — the system resets them back to 755 when the filter starts. Works on: macOS 26.3 (25D125) — same code, same entitlements, same team, same directory permissions. Fails on: macOS 26.5.1 (25F80) — neagent can't write the bloom filter data. Entitlements and provisioning profiles are identical on both machines (both include url-filter-provider). This appears to be a regression in neagent between builds 25D125 and 25F80.