Simon Willison’s Weblog

17th February 2026

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"