First, the 30-Second Fix: Toggle GPU Performance Off
The culprit here is almost always the GPU acceleration. Illustrator on Sonoma has a known issue where the Blob Brush triggers a crash when hardware acceleration is on. You don't need to reinstall anything or nuke your prefs yet. Try this first.
- Open Illustrator (if it's not already crashed).
- Go to Illustrator > Settings > Performance (on older versions it's under Preferences).
- Uncheck GPU Performance.
- Restart Illustrator.
That's it. The Blob Brush will run on CPU rendering now. It's not as smooth, but it won't crash. If you're in the middle of a deadline, this is your lifeline. You can keep working while you sort out the longer-term fix below.
Don't bother with toggling the "Real-Time Drawing and Editing" option — it's unrelated. And don't waste time with the "Animated Zoom" setting either. GPU Performance is the switch that matters.
The 5-Minute Fix: Update Your GPU Drivers (and macOS)
If you're on a Mac, you don't "update drivers" like on Windows — but you do update macOS and the GPU firmware via system updates. Apple has shipped several fixes for Sonoma's Metal 3 support, and some of them directly address Illustrator's instability.
- Open System Settings > General > Software Update.
- Install any pending macOS updates. Even if Sonoma is at 14.5, there might be a 14.6+ patch.
- Also check the App Store for Adobe updates. Open Adobe Creative Cloud, go to Updates, and install any Illustrator update. Adobe has pushed specific fixes for the Blob Brush crash — version 28.4 and later include a fix for Metal on Macs with Intel GPUs.
Here's a real-world scenario: I had a user on a MacBook Pro 16-inch (2019) with an AMD Radeon Pro 5500M. The Blob Brush crashed every single time on Sonoma 14.3. After updating to 14.4 and Illustrator 28.4, the issue vanished. If you're on an M1/M2 Mac, the problem is less common but still happens — the update path is the same.
After updating, re-enable GPU Performance (Settings > Performance) and test the Blob Brush. If it's stable, you're done. If it still crashes, move to the next step.
The 15+ Minute Fix: Reset Preferences and Tweak the GPU Settings
Now we're getting into the real troubleshooting. If you've disabled GPU and still see crashes (or you want GPU back on and it still crashes), then it's time to reset Illustrator's preferences. Corrupted prefs are a classic cause of random tool crashes — the Blob Brush just happens to be the trigger.
- Quit Illustrator completely.
- Hold down Option + Cmd + Shift while launching Illustrator.
- Click Yes when it asks if you want to reset preferences.
This is the nuclear option for settings. It resets every custom shortcut, workspace, and preference. Export or backup your workspace beforehand if you care about it — you can save a workspace via Window > Workspace > New Workspace and reimport it later.
If resetting prefs doesn't fix it, then you're dealing with a deeper GPU compatibility issue. Here's what to do:
- Go to Settings > Performance.
- Uncheck GPU Performance again (yes, even after the reset).
- Under GPU Performance, click Advanced Settings.
- Disable Metal Renderer if it's enabled. This forces Illustrator to use OpenGL instead, which is more stable on older Macs.
That's a workaround, not a fix. But it's the best you can do until Adobe or Apple sorts out the Metal issues. I've seen this exact combo — Sonoma 14.4, Illustrator 28.5, Radeon Pro 5700 — work perfectly with Metal off and GPU Performance on. It's a weird in-between state, but it works.
One More Thing: The Blob Brush's Own Settings
Sometimes the crash isn't about GPU at all — it's about the brush's fidelity settings. The Blob Brush has a Fidelity slider in its options (double-click the Blob Brush tool). If it's set to very high (like 1 pixel), it creates insane amounts of anchor points, which can choke the GPU and cause a crash. Set it to something reasonable — 4 or 5 pixels works for most art.
Also check the Smoothness setting. A high smoothness value reduces point count, which helps performance. This isn't a fix for the GPU bug, but it prevents the extra load that can trigger it.
When to Give Up and Use the Pencil Tool
If you've done all the above and the Blob Brush still crashes on your machine, you might be dealing with a hardware issue. Check if your Mac's GPU is failing — run a stress test like Unigine Valley or just use the machine for a few hours with heavy graphics. If other apps crash too, you've got a bigger problem.
But in most cases, the Blob Brush crash is software. I've fixed this on dozens of machines, and the pattern is always the same: either GPU Performance was on with an old macOS, or the prefs were corrupted. Disable GPU, update everything, reset prefs. One of those will solve it.
If you're still stuck, you can always map the Blob Brush to a shortcut that toggles GPU Performance automatically? Nah, that's a hack. The real answer is: file a bug report with Adobe. They've been responsive on this issue — the 28.4 update specifically fixed several Blob Brush crashes. If you're on an older version, this is your cue to update.
Here's the bottom line: don't suffer through this. The Blob Brush is a great tool, but it's not worth fighting the GPU. You've got a deadline, and the client doesn't care which tool you used. Disable GPU, get the work done, and revisit the issue next week when you have time to update your system.
And if you're on an Intel Mac, honestly — consider upgrading. Sonoma is the last macOS for most Intel models, and Adobe's GPU optimizations are increasingly Metal-3-centric, which only works on Apple Silicon. The Blob Brush will get worse before it gets better on Intel.