Headlessly A/B-test how a harness change (system prompt, tool, tool-result text, model) affects the agent's behavior, by replaying a REAL ModMixer chat transcript and running the agent's next turn against a chosen model — no GUI, no RimWorld, no manual clicking. Use when you've changed something that should change what the model DOES (e.g. "the agent should now ask before relaunching") and want runtime evidence across variants, not just a typecheck.
How to install harness-verify?
lebek/modmixer/harness-verify
$npx -y skills add lebek/modmixer --skill harness-verifyInstalls into the current project.
›Prefer a prompt? Paste this to your agent
Run `npx skills use "https://github.com/lebek/modmixer" --skill "lebek/modmixer/harness-verify"` and follow the generated skill instructions now. Read its complete output, redirecting it to a temporary file first if necessary. Resolve relative paths from the supporting-files directory it provides.
Use the skills in "https://github.com/lebek/modmixer" that are relevant to the current task. Run `npx skills add "https://github.com/lebek/modmixer"` and select the relevant skills, then follow their instructions.
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