Oskar Wickström

wickstrom.techOskar Wickström

18 Oct 2024

Introduction time! I'm Oskar, a software engineer living in Sweden with my wife and two kids. Over the years I've been into software testing and specification, functional programming (Haskell, various Lisps, and more), web development, and design. I write on wickstrom.tech. Also: music nerd.

Bombadil 0.7.10 is out, supporting a new parallel `fuzz` runner and `shrink` for minimizing traces with violations. github.com/antithesishq...

More browser performance work in Bombadil resulting in throughput increase of 2-4x! Any interest in more details? Blog post? Screencast?

Why obsess over throughput? Because faster fuzzing means finding more bugs faster! It's a very important lever for us. It's also fun and addictive. Bombadil ran at ~1 state per second only 6 months ago, and it's now around 100x faster.

15 Sept

8 parallel workers (and Chromium processes) with a simple interactive CLI dashboard, exploring TodoMVC. It's getting really interesting...

github.comRelease v0.7.3 · antithesishq/bombadilMajor updates: Browser testing is now up to 6x faster, capturing and testing up to 60 states per second, made possible by forking and heavily rewriting our CDP client, along with various improveme...

9 Sept

Bombadil 0.7.3 is released! It features a massive speed-up in browser tests, now capable of capturing and checking up to 60 states per second. github.com/antithesishq...

Here's Bombadil finding a 1/6^10 probability bug (rolling a die 10 times and finding a particular sequence of numbers) inside Antithesis within minutes.

It should be noted that it's a small synthetic benchmark, I'll be back with more results from real-world apps. But combined with last week's bug found by Antithesis+Bombadil, I'm very optimistic about how this plays out.

This leap is very satisfying, as I've been in this fight for many years, not having a good answer for one of the fundamental questions.

Here's Bombadil finding a 1/6^10 probability bug (rolling a die 10 times and finding a particular sequence of numbers) inside Antithesis within minutes.

I had various designs where if you at least had isolation, then over time you could *maybe* get somewhere. Building up some graph or tree model of the space, balance exploration vs exploitation, etc. The catch is that the code also changes over time, which greatly complicates building useful models.

Here, instead, we have full-system branching time, and the fuzzer uses client-side JS coverage as part of the objective function. It's all done with default properties in Bombadil, no extra config needed. It takes a few minutes to find the bug, it's all online learning, no over-time complications.

Here's Bombadil finding a 1/6^10 probability bug (rolling a die 10 times and finding a particular sequence of numbers) inside Antithesis within minutes.

This was always that one very uncomfortable concession when talking about browser fuzzing: the slowness and the practical impossibility of rewinding time, made it very impractical to do any sort of search through a state space.

Blind random walks are useful and you can definitely find bugs that you hadn't otherwise, but there's so much you're missing out on.

10 Aug

We have Bombadil 0.7.0! Lots of bug fixes and improvements, along with a new action template system. github.com/antithesishq...

logicforprogrammers.comLogic for ProgrammersPractical math for the working programmer.

7 Aug

How Antithesis Found and Explained a Bombadil Race Condition wickstrom.tech/2026-08-07-b...

Oskar Wickström reposted

Hillel

@hillelwayne.com

29 July

I am delighted to announce that after 5 years of work, 15 early releases, 50,000 words written, and 100,000 more deleted, *Logic for Programmers* is now complete and available in print! Blog post announcement: www.hillelwayne.com/post/lfp/ Website: logicforprogrammers.com

10 July

The Proportional Web Inspired by the "The Elements of Typographic Style" by Robert Bringhurst, this is an exploration of beautiful typography on the web, and a reusable stylesheet. owickstrom.github.io/the-proporti...

9 July

So, now GitHub Pages deploy is broken and I can't release my thing as planned. It really is time to move...

9 July

On bad days I'm at "damn it I'll just run my own server in the basement" and on better days I'm somewhere around a single NixOS machine on some VPS.

9 July

That's how I run my wife's site: NixOS, SQLite, bespoke Rust webapp for ecommerce. It's fast and cheap, and ironically it probably has better uptime than the enshittified platforms.

2 July

The levels of (and idolization of) learned helplessness and self-deception in agentic coding are staggering. How does one stay sane?

2 July

I'm a "centrist" I guess but this is just so draining. I don't know what to make of it anymore.

youtu.beOld Tom Bombadil is a merry fuzzer! | Oskar Wickström | Bug Bash 2026YouTube video by Antithesis

25 June

The Bombadil lightning talk recording from Bug Bash 2026 is published! youtu.be/bs2xT1aq5Yo?...

github.comRelease v0.6.0 · antithesishq/bombadilMajor updates: Terminal testing with the full specification language (#190, #210, #206) Add default properties and actions for terminal (#205) Add timeout for terminal programs that output forever...

15 June

Bombadil 0.6.0 is out, with full specification language support for terminal UI testing! github.com/antithesishq...

github.comGitHub - MercuryTechnologies/zizek: Property-based testing for Haskell, built on Hypothesis.Property-based testing for Haskell, built on Hypothesis. - MercuryTechnologies/zizek

15 June

Printscreen is so 2010s. Photos of e-ink monitor is where it's at.

Oskar Wickström reposted

skyking

@jkachmar.com

11 June

work let me open source my meme library. big thank you to Antithesis for building a property testing engine called Hegel, without which i would not have put in nearly this much effort to produce something halfway decent.

13 June

Reading "The Elements of Typographic Style", I got way too inspired and went down a CSS rabbit hole trying to reproduce some of it. Everything doesn't transfer to web. (First image is my version, second is from the book.) Now I want to write something real with this stylesheet!

Alegreya is neat.

Bombadil playing terminal Tetris at 900+ actions per second. Can't really see what's going on (replays, menus, etc just flashing by). This is running the full spec language verifier on every frame.

Oskar Wickström reposted

Wenting

@wenting.bsky.social

27 May

Sorry for not posting for so long... I have been extremely busy working on my new project: The Enchanter (also called Modos Flow): a 300-ppi Eink portable monitor with 60Hz refresh rate and touch screen. It's fully open-source: gitlab.com/zephray/ench....

22 May

Maybe I'm dating and deprecating myself in a single stroke, but I genuinely struggle seeing a productivity increase from agentic coding. I try, I retry, like every 2-3 weeks. I always end up tired and slow, either from hand-holding in real time or spending hours undoing the slop.

22 May

And this is like a broken record, but yes, some things it does help with (the silly scripts, the CI YAML hell, etc). I just can't seem to get it to hit my quality bar without a lot of effort, which obviously isn't the purpose.

22 May

This is not a moral stance. It's not me saying these things aren't sometimes useful, or that they aren't very impressive anyway. It's an observation of the current practical applicability in my overall work. YMMV.

Oskar Wickström reposted

Joe Sondow

@joesondow.bsky.social

20 May

The AI bubble as an interpretive dance

This post is unavailable.

16 May

"About three months ago, I bought [...] an e-ink monitor for desktop use. I’ve used it as my primary monitor since, and I’ve had a lot of questions about it. This is my experience report, from the perspective of a working, still mostly typing, programmer." wickstrom.tech/2026-05-16-c...

15 May

Now easier than ever to run Bombadil in GitHub Actions! github.com/antithesishq...

15 May

Good morning, eink lovers!

Blue sky indeed.

Bombadil 0.5.0 is out! This one I'm really excited about, including: - 5-8x test speed-ups! - Experimental terminal UI fuzzing - Test reproduction ... and much more. Get it while it's hot at: github.com/antithesishq...

antithesishq.github.ioThe Bombadil Manual

14 May

Docs: antithesishq.github.io/bombadil/

wickstrom.techCatching Typos on My Website with Browser Testing

13 May

How I turned Bombadil into a spell checker for my website and fixed 13 old typos: wickstrom.tech/2026-05-13-c...

13 May

Rewrote my zsh prompt to support jj, so I guess it's final now.

antithesis.comWhen did the bug start?Causality analysis for Antithesis.

12 May

"When did the bug start?" Really cool feature for causality analysis from my colleagues. antithesis.com/blog/2026/ca...

12 May

There are many Rust crates in this world, Bilbo Baggins, and none of them should be used lightly.

11 May

This has now increased 7.8x and 4.6x speedups!

Oskar Wickström@wickstrom.tech

Good stuff landing soon! Bombadil fixed timeouts are going away, in favor of a dynamic strategy that monitors DOM and network activity, in order to react as quickly as possible and not waste time just sitting around. Quick measurements show 2-4x speedups in terms of actions per second.

Falling in love with jj today.

8 May

I declare myself beaten. Fuzzing btop again and was perplexed why the fuzzer sometimes terminated in the middle of a run. Turns out it used btop to kill itself...

8 May

OK, not beaten quite yet. Unshare to the rescue. Linux namespaces and unshare are very worth learning about!