pi: caveman mode

Alessandro Perrotta, developer of the pi coding agent, reimplemented the terse-speak 'caveman mode' natively in pi using a 40-line extension and skill, after finding the upstream caveman project too bloated. The extension, auto-discovered at ~/.pi/agent/extensions/caveman.ts, rewrites the system prompt on every turn via the before_agent_start event and adds a /caveman command to toggle the mode, with code blocks, commit messages, and PR descriptions always remaining at full verbosity.

♠ Previously https://perrotta.dev/2025/12/pi/ , previously https://perrotta.dev/2026/06/caveman-talk-like-caveman-save-tokens/ . Problem statement : adopt caveman https://github.com/JuliusBrussee/caveman in pi https://github.com/earendil-works/pi . Pi isn’t one of the 30+ agents caveman auto-detects. The install matrix INSTALL.md lists agent detection rules one by one — claude , cursor , windsurf , opencode , openclaw , etc — and pi isn’t in it. Running the one-liner installer here would just skip everything silently. Booo Rather than run someone else’s curl | bash against an agent it wasn’t built for, “““I””” reimplemented the terse-speak part natively, since pi already ships the two primitives needed: skills https://agentskills.io/specification and extensions https://github.com/earendil-works/pi/blob/main/packages/coding-agent/docs/extensions.md . A skill https://github.com/thiagowfx/.dotfiles/blob/7c495489141fd6036e4be70de9a065c53f7a8394/pi/.pi/agent/extensions/caveman.ts for /skill:caveman documentation, and an extension that rewrites the system prompt on every turn via pi.on "before agent start", event = ... : js const INSTRUCTIONS = Caveman mode: on. Respond terse. Drop articles a/an/the , filler just/really/basically , pleasantries, hedging. Fragments OK. Short synonyms. Technical terms exact. Pattern: thing action reason . next step . Example — not: "Sure I'd be happy to help you with that." yes: "Bug in auth middleware. Fix:" Boundaries, always: code blocks, commit messages, and PR descriptions stay normal full verbosity, never compressed. Drop caveman style for security warnings, irreversible/destructive actions, or when the user seems confused — resume caveman after. ; export default function pi: ExtensionAPI { let on = true; // auto-on by default, every session const applyStatus = ctx: { ui: { setStatus: k: string, v?: string = void } } = { ctx.ui.setStatus "caveman", on ? " caveman " : undefined ; }; pi.on "session start", async event, ctx = applyStatus ctx ; pi.on "before agent start", event = { if on return; return { systemPrompt: ${event.systemPrompt}\n\n${INSTRUCTIONS} }; } ; pi.registerCommand "caveman", { description: "Toggle caveman terse-response mode: on|off default: on ", handler: async args, ctx = { const arg = args.trim .toLowerCase ; if arg === "off" || arg === "stop" || arg === "normal" on = false; else if arg === "on" || arg === "" on = true; else return ctx.ui.notify Unknown arg "${arg}". Use: on | off , "error" ; applyStatus ctx ; ctx.ui.notify on ? "Caveman mode on." : "Caveman mode off.", "info" ; }, } ; } before agent start https://github.com/earendil-works/pi/blob/main/packages/coding-agent/docs/extensions.md before agent start fires on ~/.pi/agent/extensions/caveman.ts , auto-discovered, no /reload needed after the first load.Unlike the Claude Code plugin, I skipped lite / full / ultra / wenyan — I called that bloat back in June, and I’m not adding it to my own version either. On or off is enough. The result, unprompted : user: caveman on or off now? assistant: Caveman: on. user: how to turn it off? assistant: /caveman off I also skipped the parts that don’t have a pi equivalent: the statusline savings counter, /caveman-stats , the caveman-shrink MCP proxy that rewrites tool descriptions a proxy that rewrites what an agent sees is exactly the kind of thing worth reading before installing . The 40-line extension above covers what I actually wanted. One rule baked into both the skill and the extension: code, commits, and PRs stay full verbosity, never compressed. This experience was an eye-opener for me to realize how bloated the upstream caveman project became. 🤖 Drafted with /bloggify .— § — Reply via email mailto:serendipity@perrotta.dev?subject=Reply to: pi: caveman mode