For those working with Rich Text without embedded images, my free editor DelightEd offers a suite of unique features. I wrote it when macOS Mojave introduced Dark appearance mode, with the primary purpose of composing Rich Text documents that work independent of appearance. For that it can set styled text on a background that ensures perfect readability in both Light and Dark modes.
Since then it has gained other unique features, including support for creating interlinear text, in which different translations or versions of the same document are interleaved line by line. It will also open PDF documents and automatically extract all their text content.
General features supported include Writing Tools (Apple silicon Macs), case transformations, and a full suite of substitutions. However, until this new version of DelightEd, substitution settings haven’t been saved in DelightEd’s app settings. Version 2.5 now puts that right: to set the app’s default substitutions, set them up using the Substitution command in its Edit menu, for instance enabling Smart Links.
Then save those to its settings using the Save Defaults command in the app’s menu. Each time you open DelightEd after that, its substitutions will start from those saved defaults.
DelightEd version 2.5 for macOS 11.5 Big Sur and later, including Tahoe, is now available from here: delighted25
from Downloads above, from its Product Page, and through its auto-update mechanism.
I’m very grateful to Manuel for asking for this to be fixed.
Many discovered how long 5 minutes could last when they updated from macOS 26.3.1 to 26.4. Right at the end of its Preparation phase, Software Update showed there were only 5 minutes remaining for far longer. This article reveals what went wrong with that update.
My observations come from a Mac mini M4 Pro running a vanilla installation of macOS Tahoe, being updated from 26.3.1 (a) with the BSI installed, to 26.4. Times and details are taken from log extracts covering the final 14 minutes of the update, immediately prior to the reboot for its installation.
Preparation
At almost exactly 18:43:00, softwareupdated reported that the PREPARING_UPDATE phase was in progress, with 70% complete on the progress bar, and 20 minutes remaining. Periodic preparation activities were then reported in the log, mainly verifying components to be installed as part of the update. One of the longest of those, /usr/standalone/i386/Firmware.scap, took nearly 6.5 minutes alone, although you might wonder why that’s required on an Apple silicon Mac!
Eleven seconds later, softwareupdated changed the progress bar to display 10 minutes remaining, with 71% completed. Just 1.5 seconds later that changed again to display 5 minutes remaining with 94% complete. Six seconds after that, with 5 minutes still displayed, the log records 98.6% was complete.
The log and progress bar then remained stuck at 5 minutes remaining and 98.6% complete for the next 11 minutes and 47 seconds, before changing to 99.9% complete and no time remaining.
These are plotted in the chart below.
The final 5 minute period started at 18:43:12, and lasted until 18:55:04, as reflected in the long period of 98.6% completion (upper line) and 5 minutes remaining (lower line).
The “5 minutes” remaining actually took 12 minutes and 7 seconds, although log entries make it clear that preparation continued throughout that time, with further verifications and “Preparing system volume…”. Those details were reported as ActionText for progress monitoring, but curiously aren’t accessible to the user at the time.
Log entries record softwareupdated keeping detailed records of progress over this period, though. For example: 18:51:32.924688 softwareupdated PrepareUpdate PROGRESS (Continue) | state:{
ActionText = "Preparing system volume...";
ElapsedTime = 490;
ExpectedTime = 1335505;
PercentBytesComplete = "48.05373989419242";
PercentComplete = "4.701870471432042";
}
But those aren’t reflected in the progress bar.
Once the update had completed that preparation phase, extensive checks were performed to ensure it was correctly configured, and components were moved into place in the ‘stash’ to be used during installation. One second after successful completion, softwareupdated locked the controller state and waited for the reboot to start installation. Rebooting followed less than two minutes later.
What went wrong?
The macOS 26.4 update for Apple silicon Macs was large, and the work required to verify its contents and complete its preparation was incorrectly reported in both percent completion and time remaining. Even in smaller updates, some form of progress needs to be shown in the progress bar during these later stages of preparation, or users may be mislead into thinking the update has frozen or failed, and could for example restart their Mac to try updating again.
What should the user do?
When an update claims there’s only 5 minutes left, that could readily extend to longer, possibly on slower Macs as long as 30 minutes or more. Unless there’s evidence that the update has gone wrong at this stage, you should leave your Mac to complete it, as it almost certainly will. If you’re still in doubt and want to confirm that the update hasn’t frozen, open Activity Monitor and look for around 100% CPU from softwareupdated or related processes, and disk activity.
Unfortunately, there’s nothing the user can do to accelerate macOS updates.
One of the longstanding jokes in computing is how misleading progress indicators can be, and last week most of us had a timely reminder when we updated macOS. However much we might like a perfectly accurate linear indicator for macOS updates, this is one of those situations where the best we can expect is a compromise, as I tried to explain here.
Showing progress
There are two types of progress indicator, determinate and indeterminate, depending on whether the task is quantifiable and progress is measurable. Determinate indicators are always preferred, as they inform the user whether they need only wait only a few moments, or they have time to enjoy a leisurely meal, but that requires quantifiability and measurability.
The simple example is copying a file from one disk to another: although macOS doesn’t know in advance how long that might take, it can quantify the task as the size of the file to be copied, then keep track of how much of that has already been completed. When half the size of the file has been copied, the progress bar can be set to half-way along its total length, so providing an accurate indication of progress.
However, with some copy operations that breaks down: when copying a sparse file between APFS volumes, for example, only the sparse data is copied, not the whole file size. As a result, copying sparse files often results in progress bars that jump from a low point to completion in the twinkling of an eye. This also relies on the quantities involved being linearly proportional to the time required, an assumption that often breaks down when downloading from a remote server.
macOS updates
Updating macOS consists of a series of many tasks (see references at the end), of which only one, downloading, is both quantifiable and has measurable progress, and even that may be far from linear. Apple therefore has a choice of:
Display multiple progress indicators, appropriate to each phase. While that might work well for the download phase, it can’t work for others, including preparation, which is likely to take a period of several minutes at least.
Combine those into a single progress bar, as at present.
Use an indeterminate progress indicator, such as a spinning wheel, which would be reliable but unhelpful.
As downloading is the one task that is quantifiable and its progress is measurable, I’ll start there.
For this, the progress bar starts an an arbitrary 15%, and softwareupdated assumes the total size of that download is the magnitude of that task.
When the download has been completed, the progress bar reaches an arbitrary 55%, and its caption then changes to reporting progress with preparation.
There is a weakness in the assumption that becomes obvious when downloading from a local Content Caching server, as the final 1 GB or so normally isn’t provided from the cache, but has to be freshly downloaded from Apple’s servers. However, that isn’t normally apparent when caching isn’t available and the whole of the download comes from the same remote source.
For the remainder of the progress bar, between 0%-15% and 55%-100%, the task is neither quantifiable nor measurable. Instead, softwareupdated divides it into a series of subtasks, each of which has a fixed progress level. One list of subtasks and levels obtained from the log is given in the Appendix at the end.
The disadvantage of that strategy is that time required by each subtask varies with the update and the Mac being updated. Inevitably, computationally intensive subtasks will proceed more rapidly on newer and faster Macs, while those mainly constrained by disk speed should be more uniform. Large updates should take significantly longer, and that will vary by subtask as well.
The last 5 minutes
A particular problem with some more recent macOS updates, including that from 26.3.1 to 26.4 last week, has been unmarked progress over the final “5 minutes” of preparation. While indeterminate progress indicators continue to move over that period, and reassure the user that the task hasn’t ground to a halt or frozen, the progress bar shown had no intermediate points, making it easy to misinterpret as failure to progress. If this is going to be a feature of future macOS updates, Apple needs to insert some intermediate points to let the user know that the update is still proceeding.
Conclusion
A progress bar that combines different measures of progress, such as download size and substages, can work well, but only if the user is aware of how to read it. As we only update macOS a few times each year, that isn’t sufficient exposure, and how it works needs to be made explicit.
In my account of how Tahoe updates macOS, I had reached the stage when Rosetta and the main update had started downloading from Pallas, Apple’s software update server (see the Appendix at the end for further explanation of terms used).
Download
Currently, the main update download (at least) is compressed using Zip, and is decompressed as a stream during download, so there’s no delay decompressing during the preparation phase later.
In this case, downloading the main update was completed within 8 minutes. The source of the Zip archive was originally given as a path on [https://]updates.cdn-apple.com/2026WinterFCS/patches, and that was written to a local path on /System/Library/AssetsV2/com_apple_MobileAsset_MacSoftwareUpdate/ In my case, though, I have a local Content Caching Server running, and immediately before the download started com.apple.AssetCacheServices substituted a download URL on that server to ensure the update was obtained through the local caching server. At the same time, an Event Report was sent back to Apple, recording the start of download.
Progress was updated every second during the download, and brought the progress bar from 16% to 53.9% over the following 8 minutes, with little other activity taking place.
Preflight
Activity then changed to what is repeatedly referred to as Preflight FDR Recovery, and is the first entry point for the UpdateBrainService, downloaded for MobileSoftwareUpdate rather than softwareupdated.
This runs an Event Recorder and begins to perform preflight checks to “recover FDR SFR”, and to perform a “firmware-only update”. To prepare for that, it retrieves various nonces and their digests for LocalPolicy, RecoveryOS boot policy, and others. Following those is the first of many attempts to determine purgeable space, in preparation for installation of the update. Those are performed by com.apple.cache_delete.
Pallas was then checked to see if there was any more recent version of RecoveryOS UpdateBrain, but there wasn’t. A further check for any newer recoveryOS was also made, before the main macOS update was prepared, at a progress level of 60% as set previously.
Preparation
The first step of the main preparation phase is to purge staged assets with com.apple.cache_delete. With that complete, UpdateBrainService recalculates cryptex size requirement for the update, and the install target prepare size:
cryptex size is 1.2 times the app cryptex size = 60 MB, plus 1.2 times the system cryptex size = 7749 MB, a total of 7809 MB, as previously calculated;
prepare size is the sum of the snapshot installation size of 3785 MB, the cryptex size of 7809 MB, three ‘slack sizes’ for VW, Recovery and Preboot of 2048 + 1024 + 1024 = 4096 MB, the new template size of 991 MB, twice the update partition size totalling 600 MB, less the old template size of 363 MB. The grand total comes to 16,918 MB.
UpdateBrainService then checks volume free sizes, and confirms that they’re sufficient to complete the update. It next creates a ‘stash’, which is protected by keys in the stash keybag, handled by the Secure Enclave Processor. There is then another round of purging with com.apple.cache_delete.
Much of the preparation phase is spent verifying the protection of installation packages, cryptexes, then the contents of /System/Applications and /System/Library. As progress is about 64% complete, System volume preparations are started, and there’s another round of purging by com.apple.cache_delete. There’s surprisingly little log activity as progress passes 70% complete.
With progress reaching 84% complete, UpdateBrainService starts unarchiving files in parallel, taking just under 5 seconds to complete those. Following that, there’s another brief period unarchiving data files in parallel, then working with the contents of /System/Volumes/Update/mnt1/private/var/MobileAsset/PreinstalledAssetsV2 as progress reaches 87% complete.
When there’s 87.5% completed, UpdateBrainService reports it’s creating hard links in parallel, then is searching for new paths and verifying files, such as those in the Ruby framework. The Recovery volume is unmounted, and there’s yet another purge with com.apple.cache_delete. After those, key volume locations are checked.
The high water mark of disk usage during update is prepared. This reveals some of the steps to be undertaken during installation, including:
prepare source package,
patch cryptexes,
patch system volume,
extract to system volume,
install personalised.
There’s a further round of purging with cache_delete before declaring PrepareUpdate as successful, then suspending the update briefly. When update resumes, the Update volume is mounted and prepared, and there’s another round of purging. The System volume is then mounted, checked, and prepared. Progress is now at 98.5% complete, and once 100% is reached, the countdown to restarting the Mac is begun.
Installation
During the download and preparation phases, apart from repeated purging, the log is generally quiet. This changes dramatically once the Mac starts preparing for shutdown and installation. WebKit is cleaned up and shut down, as are many other processes. The ‘stash’ of update components is then committed, and final scans and checks are completed.
The update is then applied, followed by Rosetta, RecoveryOS, UpdateBrain and finally minor documentation. After that period of nearly 20 seconds, this phase is declared complete, and a restart is notified before waiting for the essential reboot.
Reboot
Once rebooting by root has been initiated, the boot chime is muted to ensure the update continues in silence. The last log message is written a few seconds later, and UpdateBrain then runs the update.
Less than 3 minutes later, the system boot is recorded in the log, and kprintf is initialised 5 seconds later. About 3 minutes afterwards softwareupdated is started up, and runs various clean-up routines to complete the update sequence in conjunction with ControllerSetup and a Finite State Machine.
Key points
The main update download is decompressed while streaming, to save preparation time later.
If a local Content Caching Server is connected, AssetCacheServices will substitute its IP address for that of the Pallas server to ensure the download is obtained through the cache.
Following download, extensive preflight checks are performed.
During preparation components are verified, paths checked, and some unarchiving is performed.
Prior to reboot and installation, processes including WebKit are shut down in readiness for reboot and install.
FDR is unknown, but appears associated almost exclusively with a preflight phase.
Pallas is the internal name for Apple’s software update server. This appears throughout log entries, where for example Pallas audience is jargon for the type of user, normally macOS Customer.
RecoveryOS appears to refer to the version of Recovery in the hidden container of the internal SSD, more widely known as Fallback Recovery.
SFR appears to refer to the version of Recovery in the Recovery volume of the active boot volume group, also known as Paired Recovery.
Splat, semi-splat and rollback objects all refer to cryptexes. Splat is the general term, while semi-splat refers to a cryptex-based update that might include rapid security responses (RSR) and background security improvements (BSI) implemented by replacing one or both cryptexes. Rollback objects are older versions of a cryptex that have been saved to allow a newer cryptex to be reverted to that older one, in the event that the newer cryptex causes problems.
UpdateBrain is the executable code supplied as part of an update that prepares and installs that specific update. There’s a separate UpdateBrainService for RecoveryOS.
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