ESP is an abbreviation for the EFI System Partition, where a PC uses its contents to boot a PC far enough along to start loading Windows. For almost as long as I can remember, that partition has been created and sized during Windows installation at 100 MB. But this is changing. Here’s a “known issue” for  KB5089549, Microsoft’s May 2026 Patch Tuesday cumulative update for Windows 11. It can fail mid-installation on systems with a critically full EFI System Partition (10 MB or less free space). What do we, and OEMs, do as Windows outgrows 100 MB ESP? Get bigger!

Other Evidence That Windows Outgrows 100 MB ESP

I polled the 7 PCs (2 desktops, 5 laptops) here in my office at Chez Tittel to check their ESPs and observed something interesting. Here’s what I found:

Notice that the ESP sticks at the 100 MB mark until 2024, at which point it jumps to 260 MB. Then, on this year’s May-delivered Lenovo Yoga Slim 7X Gen 11 (X2 Snapdragon) it jumps again to 450 MB. There’s no doubt about it: the EFI is getting bigger!

What is the ESP, Anywho?

The EFI System Partition — ESP, in the shorthand everyone actually uses — is a small, dedicated FAT32 partition that lives on GPT-formatted disks and serves as the staging ground for everything the system needs before the operating system proper gets involved. Boot loaders live there. Firmware drivers live there. UEFI utility executables live there. If the system can’t find and read the ESP at power-on, it goes nowhere. It is, in other words, foundational infrastructure — and like most foundational infrastructure, nobody pays attention to it until something breaks.

Microsoft’s own documentation has recommended a minimum ESP size of 200 MB for UEFI/GPT systems since at least the Windows 8 era, with 260 MB or larger as the preferred target for new installations. That guidance has been sitting in plain sight on Microsoft Learn for years. OEMs, however, have a long tradition of shipping machines with a 100 MB ESP because, at the time those machines were built, Windows fit comfortably within it. The margins were thin, but they existed. That era is over.

Why 100 MB Isn’t Enough Anymore

Every Windows feature update — and, increasingly, every cumulative security update — must write updated boot files, recovery sequences, and language-specific font sets into the ESP. As the Windows boot stack has grown over successive releases, the items demanding ESP real estate have multiplied: Secure Boot validation assets, BitLocker metadata, UEFI capsule drivers, and a collection of per-locale font files for the pre-OS boot interface that can alone consume several dozen megabytes. If 100 MB was ever “enough,” Windows has long since moved those goalposts.

The specific tripwire for KB5089549 is tight, but telling. Microsoft confirmed that the failure triggers when the ESP has 10 MB or less of free space remaining. On a 100 MB partition that has been hosting Windows through several years of cumulative updates, that threshold is entirely realistic. The update proceeds normally through its initial phases — progress bars, the usual theater — and then dies during the restart phase, right around the 35–36% completion mark. The CBS.log entries are unambiguous: SpaceCheck: Insufficient free space and ServicingBootFiles failed. Error = 0x70. The accompanying companion error code, 0xc1900104, surfaces during feature-update upgrade attempts and carries the same root cause. The partition is simply full.

Increasing ESP Lebensraum

The community has converged on two main workarounds, and it is worth being clear-eyed about both of them.

The first is the “fonts delete” trick. You mount the ESP using mountvol Y: /S from an elevated command prompt, navigate to EFI\Microsoft\Boot\Fonts, and delete everything inside — typically recovering somewhere between 30 and 60 MB in a single sweep. It is fast, it is effective, and it is entirely unsupported by Microsoft. The risk is real: those font files support non-English boot environments. If your machine ever needs to display Cyrillic, Japanese, or Arabic characters in the pre-OS recovery interface, you will have a bad time. For an English-only deployment sitting quietly in a US office, the practical risk is low. In any multilingual environment, it should be treated as a last resort only.

Microsoft has also offered its own short-term registry tweak for KB5089549 specifically: running reg add “HKLM\SYSTEM\CurrentControlSet\Control\Bfsvc” /v EspPaddingPercent /t REG_DWORD /d 0 /f from an elevated prompt, followed by a reboot. This reduces the padding buffer the update engine reserves in the ESP, giving just enough headroom to slip the update through. It buys time. It does not fix the underlying problem.

The second, more durable option is partition resizing — shrinking the C: volume and extending the ESP to somewhere between 260 MB and 512 MB. Tools like MiniTool Partition Wizard (MTPW) can accomplish this from within Windows on many configurations. That said, a WinPE offline environment is the proper path since you are modifying a sometimes live boot partition. This is the correct fix. It is also disruptive, carries a non-trivial risk of data loss if anything goes wrong mid-operation, and absolutely requires a verified backup before you touch anything. Done properly, you will not need to revisit this for years. Done carelessly, you will spend an afternoon with recovery media and a sinking feeling. I experienced this myself recently on an ASUS Zenbook A14 laptop.

MS Is Mum on Remediation

Microsoft has not, as of this writing in mid-2026, provided an official, automated remediation path. There is no inbox tool that detects an undersized ESP and expands it gracefully. Ditto no Setup-phase blocker with a clear, actionable error. There is a Known Issue Rollback for KB5089549, which automatically propagates to consumer and unmanaged devices and prevents the broken update state — useful, but it leaves the machine unpatched. Enterprise admins can deploy the associated Group Policy to apply the KIR on managed fleets. None of this changes the underlying geometry of the partition. Something’s got to grow — and soon!

The other day I said it was coming. Yesterday, it arrived at my door about noonish. Today, I want to share my first impressions. TLDR version: I expected a lot from the Snapdragon X2, and I wasn’t disappointed. In today’s post, I’ll describe Lenovo Yoga Slim 7x Gen 11 unboxing & setup. In subsequent posts I’ll go into more detail. Here goes…

Digging Into Yoga Slim 7x Gen 11 Unboxing & Setup

Lenovo’s getting pretty good at the notion of low-footprint, low-carbon packaging and delivery. The box includes 2 eggshell carton style cradled for the laptop, a bamboo fiber sleeve for same, a cardboard holder for the one-piece 65W brick, which comes wrapped in a disposable paper sleeve. That last is black, and easy to miss: I didn’t even notice it until I checked it for the power rating info. Good job, packaging team!

I jostled the power switch (right edge of keyboard deck) as I picked up the unit, and it came right up with a full charge. I’m happy to report that “instant-on” remains as fast and reliable on X2 models as it was on their X1 predecessors. I logged right into the Lenovo review account and got going, and jumped into the setup process. That has its own story (complete with interesting bumps in the road). First, let me offer a table to compare Snapdragon X1 and X2 laptops:

Snapdragon X1 vs. X2: Good Gets Better

The key points to absorb from the following info are: more and faster cores, more cache, DX12 Ultimate, 80 TOPS NPU, PCIe 5.0. This laptop is noticeably faster than my 8 core Ryzen 7 5800X desktop with 64GB RAM, especially on CPU-intensive tasks. Impressive!

One Small Little Gotcha…

My only real disappointment with the review unit was that it shipped to me running Windows 11 Home. That’s because I rely on RDP (through Remote Desktop Connection, aka mstsc.exe). Thus, I had to upgrade to Windows 11 Pro to make that work. However, this is a minor beef, and one easily remedied at purchase time for an extra US$50.

Here’s the configuration Lenovo sent (aside from the already-mentioned OS): X2E Elite 88-100 CPU, 32GB RAM, 1TB PCIe Gen4 SSD, 1920×1200 OLED display. As configured, the Lenovo store currently lists the price at US$1,795.49. Comparatively speaking, I believe this is a good deal, given current prices for RAM and SSD.

Setting Up the Yoga Slim 7X Gen 11

Things got interesting right away. I made a misstep and associated my MSA with the Lenovo review account — not smart. As a result, I ran a factory reset to see what would happen. Indeed, it took about 22 minutes all told (pretty darn fast, AFAIK). That put me back into the base OOBE for Windows 11. Then, I burned an MVP key to upgrade from Home to Pro, which went amazingly fast — less than 2 minutes from hand-off to the Pro desktop. Overall, given intense non-gaming workloads, this unit screams!

Along the way, I learned that you can target ARM CPUs in WinGet using the --architecture ARM parameter and argument during installs. That helped me get the right versions of CrystalDiskMark, PowerShell 7, and a couple of other odds and ends up and running on the X2 laptop. In addition, I used a combination of PatchMyPC Home Updater and WinGet to get all the usual tools and applications up and running. On the whole, that process took about 2 hours and was pretty enjoyable.

I did hit a typical snag in getting RDP to work. Specifically, I was unable to get into the laptop (machine name: Yog7X2) using a Microsoft Account (MSA), despite various well-known fixes — namely, requiring Hello compliance for all logins, and making sure to sign in with the password at least once to get the MSA registered with the LSA. Consequently, I resorted to the equally well-known workaround of setting up a local account and using that instead.

First Impressions: Bedazzled and Enthused

I’ve actually purchased two Snapdragon X1 laptops for our household already (in 2025). For instance, I own an ASUS Zenbook A14. Meanwhile, my son has a ThinkPad T14s Gen 6 that we bought to replace a ThinkPad X390 after its display cracked. Obviously, I’m already enamored of the value proposition: decent performance, great battery life, and a slim, portable form factor. Indeed, both of us emphatically like those older models.

Surprisingly, the Slim 7X Gen 11 runs noticeably faster than most of the fleet here at Chez Tittel. To be clear, that fleet includes high-end Lenovo models like the ThinkPad P16 Gen3 Mobile Workstation and the ThinkStation P3 Ultra — so that’s a significant statement.

In addition, the unit is incredibly light at 1.17 kg (2.58 lbs). At the same time, even the low-end OLED display is brilliant and easy on the eyes. Astonishingly, reviews published so far (it’s early in the life cycle) put battery life in a range from 25 hours (mixed real-world usage) to 31 hours (local video playback), with Lenovo claiming “up to 29 hours” in its CES 2026 announcement. Naturally, I’ll see how that pans out in my own testing and usage.

All in all, this is a machine I wanted to see and use. Now that I’ve gotten started, I’m favorably disposed. Furthermore, I’m expecting my ardor and appreciation to grow as I get more time with this snazzy little laptop. Stay tuned: I plan to post three more items about this device in the next two weeks.

One More Things (Added 1 Day Later)

The Yoga Slim 7X Gen 11 also offers another feature I definitely appreciate. I concur with Michael Crider’s recent PC World story that OEMs should provide USB-C ports on both sides of their laptops for ease of access to chargers and docks in cramped conditions and on on office desktops. And guess what? Lenovo provides 3 (!) USB-C ports on this model: 2 on the left side, and one on the right. Good stuff!