Quickstart

Install one rule file and your coding agent answers the same question in fewer output tokens. It is text, it needs no account and no binaries, and it takes about a minute.

Want the local tools that shrink what the agent reads? That is Add the local tools. Building an agent from scratch? Start at the Agent SDK.

Install#

In Claude Code, install the plugin. It also wires the two hooks that track the mode and write it to disk:

claude plugin marketplace add JuliusBrussee/caveman && claude plugin install caveman@caveman

Everywhere else, the skills CLI:

npx skills add JuliusBrussee/caveman -g

-g installs into the agent's user skill directory. Drop it to install into the current project instead. Supported agents lists the profile slug for each host, and JetBrains Junie takes npx skills add JuliusBrussee/caveman -a junie -g. The full matrix is in INSTALL.md.

JetBrains ran 86 real coding tasks as a paired A/B with this skill alone and found 8.5 percent fewer output tokens with no detectable quality change, sign test p = 0.82.

Ask a question#

Start a new session and ask the agent something. The answer arrives without the preamble, and the symbol is still named. The skill has the same question answered both ways, at 69 tokens against 19. Code, commands, file paths and exact error strings are copied through byte for byte; only the prose around them shortens. What it leaves alone is the full list.

Pick a level#

Type /caveman in the agent if it has not woken up on its own, then /caveman lite or /caveman ultra to change how far it goes. full is the default, and three wenyan variants exist as well. Levels shows the same answer at each one.

Verify#

For the plugin, read the mode file the hooks write:

cat "${CLAUDE_CONFIG_DIR:-$HOME/.claude}/.caveman-active"

full

It mirrors whichever window wrote most recently. For a npx skills add install, check the directory instead:

ls ~/.claude/skills/caveman

Undo#

Say stop caveman or normal mode in the session to go back to full sentences there. To remove it:

claude plugin uninstall caveman@caveman   # the plugin
npx skills remove caveman                 # a skills CLI install

Limits#

The skill rides along as input tokens on every call. skills/caveman/SKILL.md is 1,650 tokens under o200k_base, and the compiled per-agent pack Claude Code loads is 2,131, so on a one-line question it can cost more than it saves. If you are billed per request rather than per token, a shorter answer is still one request. Numbers and limits has the rest.