Simon Willison’s Weblog

Rodney v0.4.0. My Rodney CLI tool for browser automation attracted quite the flurry of PRs since I announced it last week. Here are the release notes for the just-released v0.4.0:

• Errors now use exit code 2, which means exit code 1 is just for for check failures. #15
• New rodney assert command for running JavaScript tests, exit code 1 if they fail. #19
• New directory-scoped sessions with --local/--global flags. #14
• New reload --hard and clear-cache commands. #17
• New rodney start --show option to make the browser window visible. Thanks, Antonio Cuni. #13
• New rodney connect PORT command to debug an already-running Chrome instance. Thanks, Peter Fraenkel. #12
• New RODNEY_HOME environment variable to support custom state directories. Thanks, Senko Rašić. #11
• New --insecure flag to ignore certificate errors. Thanks, Jakub Zgoliński. #10
• Windows support: avoid Setsid on Windows via build-tag helpers. Thanks, adm1neca. #18
• Tests now run on windows-latest and macos-latest in addition to Linux.

I've been using Showboat to create demos of new features - here those are for rodney assert, rodney reload --hard, rodney exit codes, and rodney start --local.

The rodney assert command is pretty neat: you can now Rodney to test a web app through multiple steps in a shell script that looks something like this (adapted from the README):

#!/bin/bash
set -euo pipefail

FAIL=0

check() {
    if ! "$@"; then
        echo "FAIL: $*"
        FAIL=1
    fi
}

rodney start
rodney open "https://example.com"
rodney waitstable

# Assert elements exist
check rodney exists "h1"

# Assert key elements are visible
check rodney visible "h1"
check rodney visible "#main-content"

# Assert JS expressions
check rodney assert 'document.title' 'Example Domain'
check rodney assert 'document.querySelectorAll("p").length' '2'

# Assert accessibility requirements
check rodney ax-find --role navigation

rodney stop

if [ "$FAIL" -ne 0 ]; then
    echo "Some checks failed"
    exit 1
fi
echo "All checks passed"

# 17th February 2026, 11:02 pm / projects, annotated-release-notes, testing, browsers, rodney

Datasette 1.0a24. New Datasette alpha this morning. Key new features:

• Datasette's Request object can now handle multipart/form-data file uploads via the new await request.form(files=True) method. I plan to use this for a datasette-files plugin to support attaching files to rows of data.
• The recommended development environment for hacking on Datasette itself now uses uv. Crucially, you can clone Datasette and run uv run pytest to run the tests without needing to manually create a virtual environment or install dependencies first, thanks to the dev dependency group pattern.
• A new ?_extra=render_cell parameter for both table and row JSON pages to return the results of executing the render_cell() plugin hook. This should unlock new JavaScript UI features in the future.

More details in the release notes. I also invested a bunch of work in eliminating flaky tests that were intermittently failing in CI - I think those are all handled now.

# 29th January 2026, 5:21 pm / projects, datasette, python, uv, annotated-release-notes

shot-scraper 1.9. New release of my shot-scraper CLI tool for taking screenshots and scraping websites with JavaScript from the terminal.

• The shot-scraper har command has a new -x/--extract option which extracts all of the resources loaded by the page out to a set of files. This location can be controlled by the -o dir/ option. #184
• Fixed the shot-scraper accessibility command for compatibility with the latest Playwright. #185

The new shot-scraper har -x https://simonwillison.net/ command is really neat. The inspiration was the digital forensics expedition I went on to figure out why Rob Pike got spammed. You can now perform a version of that investigation like this:

cd /tmp
shot-scraper har --wait 10000 'https://theaidigest.org/village?day=265' -x

Then dig around in the resulting JSON files in the /tmp/theaidigest-org-village folder.

# 29th December 2025, 10:33 pm / projects, shot-scraper, annotated-release-notes

uv-init-demos. uv has a useful uv init command for setting up new Python projects, but it comes with a bunch of different options like --app and --package and --lib and I wasn't sure how they differed.

So I created this GitHub repository which demonstrates all of those options, generated using this update-projects.sh script (thanks, Claude) which will run on a schedule via GitHub Actions to capture any changes made by future releases of uv.

# 24th December 2025, 10:05 pm / uv, git-scraping, python, projects, github-actions

s3-credentials 0.17. New release of my s3-credentials CLI tool for managing credentials needed to access just one S3 bucket. Here are the release notes in full:

• New commands get-bucket-policy and set-bucket-policy. #91
• New commands get-public-access-block and set-public-access-block. #92
• New localserver command for starting a web server that makes time limited credentials accessible via a JSON API. #93

That s3-credentials localserver command (documented here) is a little obscure, but I found myself wanting something like that to help me test out a new feature I'm building to help create temporary Litestream credentials using Amazon STS.

Most of that new feature was built by Claude Code from the following starting prompt:

Add a feature s3-credentials localserver which starts a localhost weberver running (using the Python standard library stuff) on port 8094 by default but -p/--port can set a different port and otherwise takes an option that names a bucket and then takes the same options for read--write/read-only etc as other commands. It also takes a required --refresh-interval option which can be set as 5m or 10h or 30s. All this thing does is reply on / to a GET request with the IAM expiring credentials that allow access to that bucket with that policy for that specified amount of time. It caches internally the credentials it generates and will return the exact same data up until they expire (it also tracks expected expiry time) after which it will generate new credentials (avoiding dog pile effects if multiple requests ask at the same time) and return and cache those instead.

# 16th December 2025, 11:40 pm / annotated-release-notes, s3-credentials, ai, claude-code, llms, coding-agents, generative-ai, projects, s3, aws, prompt-engineering

LLM 0.28. I released a new version of my LLM Python library and CLI tool for interacting with Large Language Models. Highlights from the release notes:

• New OpenAI models: gpt-5.1, gpt-5.1-chat-latest, gpt-5.2 and gpt-5.2-chat-latest. #1300, #1317
• When fetching URLs as fragments using llm -f URL, the request now includes a custom user-agent header: llm/VERSION (https://llm.datasette.io/). #1309
• Fixed a bug where fragments were not correctly registered with their source when using llm chat. Thanks, Giuseppe Rota. #1316
• Fixed some file descriptor leak warnings. Thanks, Eric Bloch. #1313
• Type annotations for the OpenAI Chat, AsyncChat and Completion execute() methods. Thanks, Arjan Mossel. #1315
• The project now uses uv and dependency groups for development. See the updated contributing documentation. #1318

That last bullet point about uv relates to the dependency groups pattern I wrote about in a recent TIL. I'm currently working through applying it to my other projects - the net result is that running the test suite is as simple as doing:

git clone https://github.com/simonw/llm
cd llm
uv run pytest

The new dev dependency group defined in pyproject.toml is automatically installed by uv run in a new virtual environment which means everything needed to run pytest is available without needing to add any extra commands.

# 12th December 2025, 8:20 pm / llm, uv, annotated-release-notes, ai, llms, python, generative-ai, projects

Bluesky Thread Viewer thread by @simonwillison.net. I've been having a lot of fun hacking on my Bluesky Thread Viewer JavaScript tool with Claude Code recently. Here it renders a thread (complete with demo video) talking about the latest improvements to the tool itself.

I've been mostly vibe-coding this thing since April, now spanning 15 commits with contributions from ChatGPT, Claude, Claude Code for Web and Claude Code on my laptop. Each of those commits links to the transcript that created the changes in the commit.

Bluesky is a lot of fun to build tools like this against because the API supports CORS (so you can talk to it from an HTML+JavaScript page hosted anywhere) and doesn't require authentication.

# 28th November 2025, 11:57 pm / bluesky, ai, claude-code, llms, vibe-coding, coding-agents, tools, generative-ai, projects, cors

llm-anthropic 0.23. New plugin release adding support for Claude Opus 4.5, including the new thinking_effort option:

llm install -U llm-anthropic
llm -m claude-opus-4.5 -o thinking_effort low 'muse on pelicans'

This took longer to release than I had hoped because it was blocked on Anthropic shipping 0.75.0 of their Python library with support for thinking effort.

# 25th November 2025, 5:26 am / llm, anthropic, claude, generative-ai, projects, ai, llms

sqlite-utils 3.39. I got a report of a bug in sqlite-utils concerning plugin installation - if you installed the package using uv tool install further attempts to install plugins with sqlite-utils install X would fail, because uv doesn't bundle pip by default. I had the same bug with Datasette a while ago, turns out I forgot to apply the fix to sqlite-utils.

Since I was pushing a new dot-release I decided to integrate some of the non-breaking changes from the 4.0 alpha I released last night.

I tried to have Claude Code do the backporting for me:

create a new branch called 3.x starting with the 3.38 tag, then consult https://github.com/simonw/sqlite-utils/issues/688 and cherry-pick the commits it lists in the second comment, then review each of the links in the first comment and cherry-pick those as well. After each cherry-pick run the command "just test" to confirm the tests pass and fix them if they don't. Look through the commit history on main since the 3.38 tag to help you with this task.

This worked reasonably well - here's the terminal transcript. It successfully argued me out of two of the larger changes which would have added more complexity than I want in a small dot-release like this.

I still had to do a bunch of manual work to get everything up to scratch, which I carried out in this PR - including adding comments there and then telling Claude Code:

Apply changes from the review on this PR https://github.com/simonw/sqlite-utils/pull/689

Here's the transcript from that.

The release is now out with the following release notes:

• Fixed a bug with sqlite-utils install when the tool had been installed using uv. (#687)
• The --functions argument now optionally accepts a path to a Python file as an alternative to a string full of code, and can be specified multiple times - see Defining custom SQL functions. (#659)
• sqlite-utils now requires on Python 3.10 or higher.

# 24th November 2025, 6:59 pm / coding-agents, projects, sqlite, claude-code, sqlite-utils, uv, annotated-release-notes

llm-gemini 0.27. New release of my LLM plugin for Google's Gemini models:

• Support for nested schemas in Pydantic, thanks Bill Pugh. #107
• Now tests against Python 3.14.
• Support for YouTube URLs as attachments and the media_resolution option. Thanks, Duane Milne. #112
• New model: gemini-3-pro-preview. #113

The YouTube URL feature is particularly neat, taking advantage of this API feature. I used it against the Google Antigravity launch video:

llm -m gemini-3-pro-preview \
 -a 'https://www.youtube.com/watch?v=nTOVIGsqCuY' \
 'Summary, with detailed notes about what this thing is and how it differs from regular VS Code, then a complete detailed transcript with timestamps'

Here's the result. A spot-check of the timestamps against points in the video shows them to be exactly right.

# 18th November 2025, 11 pm / gemini, llm, generative-ai, projects, ai, llms, youtube

llm-anthropic 0.22. New release of my llm-anthropic plugin:

• Support for Claude's new structured outputs feature for Sonnet 4.5 and Opus 4.1. #54
• Support for the web search tool using -o web_search 1 - thanks Nick Powell and Ian Langworth. #30

The plugin previously powered LLM schemas using this tool-call based workaround. That code is still used for Anthropic's older models.

I also figured out uv recipes for running the plugin's test suite in an isolated environment, which are now baked into the new Justfile.

# 15th November 2025, 8:48 pm / llm, anthropic, claude, generative-ai, projects, ai, llms, uv, python

Datasette 1.0a22. New Datasette 1.0 alpha, adding some small features we needed to properly integrate the new permissions system with Datasette Cloud:

• datasette serve --default-deny option for running Datasette configured to deny all permissions by default. (#2592)
• datasette.is_client() method for detecting if code is executing inside a datasette.client request. (#2594)

Plus a developer experience improvement for plugin authors:

• datasette.pm property can now be used to register and unregister plugins in tests. (#2595)

# 13th November 2025, 11:04 pm / projects, datasette-cloud, annotated-release-notes, datasette

SLOCCount in WebAssembly. This project/side-quest got a little bit out of hand.

I remembered an old tool called SLOCCount which could count lines of code and produce an estimate for how much they would cost to develop. I thought it would be fun to play around with it again, especially given how cheap it is to generate code using LLMs these days.

Here's the homepage for SLOCCount by David A. Wheeler. It dates back to 2001!

I figured it might be fun to try and get it running on the web. Surely someone had compiled Perl to WebAssembly...?

WebPerl by Hauke Dämpfling is exactly that, even adding a neat <script type="text/perl"> tag.

I told Claude Code for web on my iPhone to figure it out and build something, giving it some hints from my initial research:

Build sloccount.html - a mobile friendly UI for running the Perl sloccount tool against pasted code or against a GitHub repository that is provided in a form field

It works using the webperl webassembly build of Perl, plus it loads Perl code from this exact commit of this GitHub repository https://github.com/licquia/sloccount/tree/7220ff627334a8f646617fe0fa542d401fb5287e - I guess via the GitHub API, maybe using the https://github.com/licquia/sloccount/archive/7220ff627334a8f646617fe0fa542d401fb5287e.zip URL if that works via CORS

Test it with playwright Python - don’t edit any file other than sloccount.html and a tests/test_sloccount.py file

Since I was working on my phone I didn't review the results at all. It seemed to work so I deployed it to static hosting... and then when I went to look at it properly later on found that Claude had given up, cheated and reimplemented it in JavaScript instead!

So I switched to Claude Code on my laptop where I have more control and coached Claude through implementing the project for real. This took way longer than the project deserved - probably a solid hour of my active time, spread out across the morning.

I've shared some of the transcripts - one, two, and three - as terminal sessions rendered to HTML using my rtf-to-html tool.

At one point I realized that the original SLOCCount project wasn't even entirely Perl as I had assumed, it included several C utilities! So I had Claude Code figure out how to compile those to WebAssembly (it used Emscripten) and incorporate those into the project (with notes on what it did.)

The end result (source code here) is actually pretty cool. It's a web UI with three tabs - one for pasting in code, a second for loading code from a GitHub repository and a third that lets you open a Zip file full of code that you want to analyze. Here's an animated demo:

The cost estimates it produces are of very little value. By default it uses the original method from 2001. You can also twiddle the factors - bumping up the expected US software engineer's annual salary from its 2000 estimate of $56,286 is a good start!

I had ChatGPT take a guess at what those figures should be for today and included those in the tool, with a very prominent warning not to trust them in the slightest.

# 22nd October 2025, 6:12 am / perl, ai, claude-code, llms, vibe-coding, webassembly, ai-assisted-programming, tools, javascript, generative-ai, projects