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png-cmp is a program I built that checks if two PNGs are visually equivalent. It’s inspired by the cmp command. Here’s how you use it:

png-cmp a.png b.png

Like cmp, it silently exits if the images are identical, and gives an error if they’re different.

Unlike cmp, it checks pixel data, not binary data. PNGs can look the same but be stored differently. For example, png-cmp ignores text metadata.

I was recently doing an experiment where I wanted to check if two PNGs were visually identical, so I built a tool for it!

Grab the source code here.

Out of the box, Zig provides minimal and sufficient facilities for error handling --- strongly-typed error codes. Error reporting is left to the user. Idiomatic solution is to pass a Diagnostics out parameter (sink) to materialize human-readable strings as needed.

Writing custom Rust lints for fun and profit

/elsewhere/sightings/

I built this feature on my phone using Claude Code for web, as an extension of my beats system for syndicating external content. Here's the PR and prompt.

As with my other forms of incoming syndicated content sightings show up on the homepage, the date archive pages, and in site search results.

I back-populated over a decade of iNaturalist sightings, which means you can search for lemur you'll see my lemur photos from Madagascar in 2019!

Tags: blogging, photography, wildlife, ai, inaturalist, generative-ai, llms, ai-assisted-programming, claude-code

Chilling effects in the build-to-rent sector, how fast could robot manufacturing scale up, PJM’s new interconnection queue, the backlash against battery storage, and more.

Giving dependencies the same treatment the fork got

This series of articles chronicles the history, both real and pseudo, behind Gabriel Knight 3: Blood of the Sacred, Blood of the Damned. It is possible to trace the Plantard family tree a fair ways back without relying on the Lobineau dossier, but not as far back as the time when the Merovingian kings ruled […]

Pictured above is the new DeskPi Super4C installed in an 8U mini rack. The Super4C is a 4-node Raspberry Pi CM5 cluster board that solves two pain points I had with the older Super6C.

I was testing this board around the same time I helped kick off the SBCC 2026, the Single Board Cluster Competition for students. A dozen or so university teams squared off to run the best mini HPC cluster with a budget of $6,000, and a couple days to benchmark six HPC workloads.

What to do when upstream ghosts you

Codex CLI 0.128.0 adds /goal

It looks like the feature is mainly implemented though the goals/continuation.md and goals/budget_limit.md prompts, which are automatically injected at the end of a turn.

Via @fcoury

Tags: ai, openai, prompt-engineering, generative-ai, llms, coding-agents, system-prompts, codex-cli, agentic-engineering

Our evaluation of OpenAI's GPT-5.5 cyber capabilities

Tags: ai, openai, generative-ai, llms, anthropic, claude, ai-security-research, gpt

It's a common misconception that we can't tell who is using LLM and who is not. I'm sure we didn't catch 100% of LLM-assisted PRs over the past few months, but the kind of mistakes humans make are fundamentally different than LLM hallucinations, making them easy to spot. Furthermore, people who come from the world of agentic coding have a certain digital smell that is not obvious to them but is obvious to those who abstain. It's like when a smoker walks into the room, everybody who doesn't smoke instantly knows it.

I'm not telling you not to smoke, but I am telling you not to smoke in my house.

— Andrew Kelley, Creator of Zig

Tags: zig, llms, ai, generative-ai

We need RSS for sharing abundant vibe-coded apps

I would love an RSS web feed for all those various tools and apps pages, each item with an “Install” button. (But install to where?)

The lesson here is that when vibe-coding accelerates app development, apps become more personal, more situated, and more frequent. Shipping a tool or a micro-app is less like launching a website and more like posting on a blog.

This inspired me to have Claude add an Atom feed (and icon) to my /elsewhere/tools/ page, which itself is populated by content from my tools.simonwillison.net site.

Tags: atom, matt-webb, rss, ai, vibe-coding

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