The other day I was updating my M1 Apple Mac Mini to macOS Monterey and received a strange error. “Failed to load update brain trust cache”. Being that I write a lot of try catch blocks when programming, and know they rules I live under to make meaningful actionable catch error box responses, and what goes into providing users information they can actually use to handle an error, I was intrigued to find out what Apple was thinking on this one.
Failed is just a verb they used to notify that they catch was reached.
Load is another verb letting the user a file was attempted to be opened
Trust Cache is something that Apple uses trust files for letting the system run stuff at a platform privilege level. Meaning these cache files content are trusted by the entire computer.
Update brain is the logic that is tied to an update. Meaning the programming (the brain) so the update knows what to do.
So in other words, during the update, the local trusted cache needs to be updated, the logic that runs the update regardless if the update is on a watch, phone, ipad, macOS or whatever needs to be trusted at a platform level so it can run. So that local immutable read only cache needs to get an update before the system can update.
My guess is that 1) the apple update downloads to a computer 2) the update once started does a hash compare to make sure the update file has not been hijacked during transit to the computer that is running the update. To do that the hash of the update is compared with apple over the internet. If the hash checks out then 3) the local trusted cache gets updated so the update can run a platform level with out the user having to enter their username over and over again during the update.
In my case, what the error was telling me is that when the hash was being compared, the compare either failed, or more likely when the Update Brain was attempted to be opened as a platform level trust cache, that open failed.
What I did is click the button to start the update again, and the file probably called update brain was able to load as platform privilege storage as trust cache.