# pi: caveman mode

> Source: <https://perrotta.dev/2026/07/pi-caveman-mode/>
> Published: 2026-07-22 10:14:47+00:00

♠ [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`

.— § —

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