caveman

Thu, 15 Oct 2026 20:46:54 +0800

JuliusBrussee/caveman

why many token when few do trick

Caveman make your AI agent say less and read less. Code stay exact. Brain still big.

33.2% fewer

input tokens, whole sessions
_{54 Claude Code runs, 18 of 18 answers right}

54% cheaper

with Auto, same score
_{85 coding tasks vs Opus 5.5 at xhigh, interim}

397 → 76

tokens for one test run
_{Blocks vs | tail -20}

1.4 to 2.4× cheaper

with caveman-style output
_{Adobe Research, eight models}

Cited by Adobe Research · A/B tested by JetBrains · Remade for Elasticsearch on Elasticsearch Labs
#1 on Hacker News · #1 on GitHub Trending · “No way this actually works.” ThePrimeagen

Install · Six rocks · Proof · Say less · Read less · Auto · Blocks · Commands · Caveman Cloud

Normal agent · 63 tokens	Caveman agent · 20 tokens
The reason your React component is re-rendering is likely because you’re creating a new object reference on each render cycle. When you pass an inline object as a prop, React’s shallow comparison sees it as a different object every time, which triggers a re-render. I’d recommend using useMemo to memoize the object.	New object ref each render, so React re-renders. Wrap the prop in `useMemo`.

Same fix. 63 token become 20. Brain still big.

Pick your club:

Skill	Same answer	Tokens
`/caveman`	New object ref each render, so React re-renders. Wrap the prop in `useMemo`.	20
`/ultracave`	Inline object prop, new ref, re-render. `useMemo`.	14
`/megacave`	新參照致重繪。`useMemo`。	13

_{Token counts: tiktoken o200k.}

Install

`1`	`npx @caveman-ai/cli@latest`

One command. Mac, Linux, Windows. Caveman find your agents and your logins, show what it change. Press Enter. Done. Needs Node.js 22.13+.

After that, plain claude stays caveman’d. So do Codex, Gemini CLI, OpenCode, and 30+ more. It runs on your machine, with your keys and your Claude Pro/Max login. One rock. That it.

_{Had caveman before 4.0? Say @latest, or the old copy on your machine wins. Already set up? caveman setup opens the screen again. Only want shorter answers? Get just the skill.}

Six rocks, one install

New in 4.0: caveman is six parts. All on after install. Each has its own switch.

Rock	What it does	Measured
Say less	Agent answers short. Code stays exact	63 → 20 tokens, same fix
Read less	Logs, JSON, CSV, test output shrink before the model reads them	33.2% fewer input tokens per session
Auto · new	Picks the model and the effort for each ask	54% cheaper than Opus at xhigh, same score
Blocks · new	Code mode: agent keeps the scripts it writes and runs them again	397 → 76 tokens for one test run
Waste fixes	Finds where your tokens go and fixes it. New: keeps the prompt cache warm while you pause	Not measured yet
Browse	Web pages come back compressed	129.8× smaller page

caveman status shows what is on. caveman off browse turns one off. Only Auto needs an account, and it is free. 4.0.0 release notes

Proof

Outside labs first. Ours come with each rock below. Nothing rounded up. Red rows stay red.

Who	Setup	Result
Adobe Research, CAVEWOMAN paper (cites this repo)	Caveman-style output, eight models, five datasets	Cost cut 1.4 to 2.4× per model, up to 3×
Elastic, Elasticsearch Labs	Caveman mode remade for Elasticsearch, eight live MCP scenarios	63.6% fewer response tokens. “Zero information loss.”
JetBrains	86 real coding tasks, paired A/B	No measurable quality loss (p = 0.82). 8.5% fewer output tokens

Two findings shaped caveman. Adobe: cavemanning your prompt makes answers worse, so caveman never touches your prompt. JetBrains: agent sessions are mostly code and tool calls, which the voice leaves alone. So caveman grew rocks that shrink what the agent reads and what it runs on.

Say less: the caveman voice

A voice, not broken grammar. Every reply follows the same structure.

Rule	What it means
Answer first	`[thing] [action] [reason]. [next step].` No greeting, no “let me”, no recap
One idea per sentence	Built on ASD-STE100, the controlled English of aircraft maintenance manuals: 20 words max, active voice, one term per thing
Meaning never dropped	Articles can go. not, never, no, only never go. Numbers and units stay exact
Payload verbatim	Code, commands, paths, and error messages untouched, character for character
No theater	No “me think”. No chatter between tool calls. If caveman phrasing isn’t shorter, plain wins
Knows when to stop	Security warnings, irreversible actions, and confused users get full sentences. Then grunt resumes
Your prompts stay yours	Never rewritten. Research say that backfire

Ten dev questions on claude-opus-5-5:

Instruction	Output tokens
None	6,983
`Answer concisely.`	4,334
`/caveman`	4,119
`/ultracave`	2,693

“Be concise” is the real baseline; new models already know it. On top of it, /caveman cuts 3% more at the median and /ultracave 35% more. Measured on the 3.1.0 rules, not yet re-run. The rules cost about 1,160 tokens of input, and if you pay per request (GitHub Copilot), shorter answers save nothing. Harness · Every case where caveman loses

Only want this rock? The skill alone, no proxy:

`1`	`npx skills add JuliusBrussee/caveman -g`

Type /caveman ($caveman in Codex) if it doesn’t start on its own. Say stop caveman to go back.

Other ways in: Claude app and phone, Claude Code plugin, Gemini, every agent at once, Windows, uninstall

Claude on the web, the phone app, or Cowork? No terminal. Add caveman to your Claude account once, in Customize > Plugins: steps. Not tested end to end yet.

# Claude Code plugin, auto-starts every interactive session, subagents too
claude plugin marketplace add JuliusBrussee/caveman && claude plugin install caveman@caveman

# Gemini CLI
gemini extensions install https://github.com/JuliusBrussee/caveman

# Every agent on your machine at once, plus the Claude Code statusline badge (Node.js 22.13+)
curl -fsSL https://raw.githubusercontent.com/JuliusBrussee/caveman/v4.0.1/install.sh | bash

Already inside Claude Code? Same rock, slash form. Type these where you talk to Claude:

1
2

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

Windows, PowerShell 5.1+:

`1`	`irm https://raw.githubusercontent.com/JuliusBrussee/caveman/v4.0.1/install.ps1 \| iex`

On npm 12 or newer, new npm block git install. One-liners above handle it themselves from v3.2.0 on. Old one-liner pinned to v3.1.0 or older still fail there: use one above, or this: npx --allow-git=root -y github:JuliusBrussee/caveman#v4.0.1

Changed your mind: npx -y github:JuliusBrussee/caveman -- --uninstall (on npm 12+, add --allow-git=root too)

Only grabbed the skill? npx skills remove JuliusBrussee/caveman -g take it back out.

Install broke? Open your agent in this repo and say “Read CLAUDE.md and INSTALL.md, install caveman for me.” Agent fix own brain.

Read less: 33.2% fewer input tokens

The voice shrinks what the agent says. This shrinks what it reads. Same answers: 18 of 18 right.

File type	The file, through caveman	File saved	Whole Claude Code session, 3 runs	Session saved
CSV	28,041 → 314	98.9%	165,823 → 74,484	55.1%
Logs	22,810 → 348	98.5%	148,807 → 74,068	50.2%
YAML	20,447 → 178	99.1%	132,124 → 71,027	46.2%
Test output	18,806 → 203	98.9%	150,377 → 108,514	27.8%
JSON	18,837 → 281	98.5%	147,975 → 108,939	26.4%
HTML	21,670 → 21,670	none yet	140,687 → 154,641	9.9% worse
All six	130,611 → 22,994	82.4%	885,793 → 591,673	33.2%

The file is each test file through today’s compressor alone. The session is the whole agent run, which also carries the system prompt and tools, so it moves less. Honest part: the session run is from August 2026 on an older engine, HTML has no compressor yet so it lost, and each test file hides one record in 61 to 72 KB of noise. Yours will vary. Headroom on the same suite: 15 of 18 right, 6.7% fewer tokens. Method

Every original stays on your disk. The agent can pull it back any time.

Auto: 54% cheaper, same score

New model in your agent’s picker. Pick Auto and caveman chooses the model and the effort for each ask. Hard ask, big brain. Easy ask, save rocks.

Setup	Tasks solved	Cost per try	Median time
Opus 5.5, xhigh effort, every ask	44.3%	$7.83	35.2 min
Auto, Claude models only	43.7%	$3.59	15.9 min
Auto, plus OpenAI and open models	42.9%	$3.47	16.7 min

Auto costs 0.46× what Opus 5.5 at xhigh costs. That is 54% saved, in under half the time. 85 real coding tasks from SWE-Interact and SWE-Together, one try each. Honest part: the run is half done, the 0.5-point score gap is too small to tell apart at this size (±7), and most of the saving is Auto lowering effort on easy asks. Already on Opus at medium? Expect less; not measured yet. Full table and limits

1
2

caveman login                  # free account. Auto shows up in the model picker
caveman providers add openai   # optional: give Auto more models, on your own key

Works in Claude Code, OpenCode, and Codex on a ChatGPT login, with API keys, Claude Pro/Max, or ChatGPT. Any other model you pick runs as picked. Not signed in: no Auto, nothing sent. What Auto sends

Blocks: code mode, script written once

skills.sh for code mode. Code mode is the agent writing a script instead of making tool call after tool call (Cloudflare, Anthropic). Problem: agent write same script every session, throw it away, write it again. Blocks keep it in your repo, check it every pull request, hand it back.

Input	Raw	What agents type now	Block
`go test -v ./...`, 326 tests	10,561	397 · `\| tail -20`	76 · `test-summary`
1.4 MB JSON file	251,893	236 · their own heredoc	227 · `json-peek`
366-line Go file	3,111	250 · `grep -n`	489 · `grep-defs`

Tokens the agent reads back. In one week, agents on one machine wrote the same script 394 times. Purdue measured the habit at up to 9.57% of task cost. grep-defs loses to a bare grep; row stays. Method

Comes with caveman. Eight blocks ready: json-peek · jsonl-stats · test-summary · first-error · wait-for · grep-defs · http-json · replace-in-file. When the agent starts typing a script a block already covers, it gets one line: use the block. Never denies or rewrites a command.

1
2

caveman-blocks scan    # what your agents retyped this month. Script text never leaves your machine
caveman-blocks init    # rules and block index into this repo's AGENTS.md

Pre-release (v0.1.0-rc.5). Python only, no sandbox yet. Own repo, own stars: caveman-ai/blocks

Smaller rocks

Rock	What it does	Measured
`caveman learn`	Ranks where your tokens go, from agent history already on disk. `caveman learn implement` applies fixes one diff at a time, only on your yes	Not yet
Warm cache · new	Step away and the provider forgets your session, so the next ask pays full price. Caveman keeps Anthropic’s prompt cache warm while you pause, only when your own history says you come back in time. Every warm is listed in `caveman stats`	Not yet
`caveman browse <url>`	A compressed web page for the agent	121 tokens instead of 15,704 for a Playwright snapshot of a 200-row table. Tiny forms lose 2.3×. Bench
`/caveman-compress <file>`	Shrinks memory files like `CLAUDE.md`, keeps a backup	4,138 tokens instead of 6,198 across five files, 22.8% to 49.1% each, every heading, code block, and path intact. Bench
Middleware	Same shrinking inside the Vercel AI SDK, LangChain, OpenAI, or Anthropic call you already make. TypeScript · Python · Every framework · One container for the team	Not yet

Commands

In your terminal:

caveman claude                # start an agent on caveman: codex · gemini · opencode · aider · kilo · qwen · hermes · openclaw · pi
caveman status                # what is on, which agents it reaches, one next step
caveman on browse             # switch one rock on or off: output · input · waste-fixes · routing · scripts · browse
caveman login                 # free account, turns on Auto
caveman learn                 # where your tokens go
caveman trial -- claude       # A/B a real session on your own work
caveman shrink -- pnpm test   # compress noisy command output
caveman convert --dry-run     # pixel mode: skills the model reads as images
caveman stats                 # your token history
caveman doctor                # one problem per line, with its fix

In your agent:

Command	What it does
`/caveman` · `/ultracave` · `/megacave`	The voice, the grunt, the 文言文. `/caveman status` shows the mode, `/caveman off` stops it
`/caveman-commit`	One-line Conventional Commit
`/caveman-review`	One finding per line: `L42: 🔴 null deref. Guard it.`
`/caveman-compress <file>`	Shrinks memory files and backs up the original
`/caveman-stats`	Real token usage for this Claude Code session
`/caveman-help`	Every mode and command on one screen
`cavecrew`	Subagents that find, edit, and review code, then report back in caveman
`investigate-first` · `lean-build` · `surgical-patch` · `safe-refactor` · `migration` · `verify-and-stop`	Work patterns that write less code. Your agent picks them up when a task fits
`caveman-setup` · `caveman-discover` · `caveman-learn` · `caveman-manage` · `caveman-optimize` · `caveman-explore` · `caveman-evidence-review`	Drive the proxy from inside your agent

Caveman Cloud

Everything above is for the coding agent you use. Caveman Cloud is for the agents you build.

You ship an agent. Every run costs money. Is it good? Is it cheap? Which change made it worse? Cloud answers.

Cloud does	What you get
Observability	Every run traced to the work and what it cost. Sets itself up from your repo, your keys, and the logs or OpenTelemetry you already have
Evals	Grades how good the answers are, on your own tasks, from your real traffic
Autopilot	Proposes a cheaper change, tests it on your recorded work, ships only when the evals say answers are still as good. You approve the pull request
Proof	Every number says if it is measured, inferred, or verified. A saving counts only after real traffic shows it

Sign up free · Try the demo · Book a call · Docs

In the wild

ThePrimeagen: “No way this actually works.” Watch

Adobe Research: CAVEWOMAN, arXiv, June 2026

JetBrains: “It is fun, and it costs you nothing measurable in quality.” Read

Elastic: elastic-caveman on Elasticsearch Labs, April 2026

Hacker News: #1, 904 points

GitHub Trending #1 overall, July 2026 · Trendshift #1 repo of the day, April 2026 · Product Hunt #8 of the day

Started as a joke in April 2026. Now past 100,000 stars. Joke got serious. Voice did not.

Privacy

The skill runs on your machine and sends nothing. One exception: /caveman-compress sends the file you compress to your configured model provider.
The CLI sends usage stats by default: commands run, token counts, caveman-blocks commands and usage counts, a random install ID, OS, and IP. Never your prompts, code, file paths, or scripts you wrote. One person maintains this for free, and those stats show what to build next. Off for good, Blocks included: caveman telemetry off or DO_NOT_TRACK=1.
Auto, only once you sign in and pick it: each ask sends Caveman Cloud your latest ask (with whatever your agent attaches to it, such as CLAUDE.md, memory or @-mentioned files), the one before it, and the end of the agent’s last reply, plus each request’s tool names, effort, a few agent headers, and the previous request’s token counts. On the Free plan Caveman may keep it to improve routing. caveman off routing stops it.
Where requests go: from your machine to your provider, or to another provider you added with caveman providers add, on your own key. Only a request routed to a Caveman Cloud model passes through Caveman Cloud, whole (system prompt, tool results, code), on your Caveman project’s stored key, billed to that project. caveman providers cloud off stops that.

The full list, and how to delete sent telemetry: SECURITY.md.

License

Apache-2.0, whole repo. Read it, fork it, ship it, host it. Free like mammoth on open plain. Older releases and third-party notices: LICENSING.md. “Caveman” and the rock logo are trademarks of Julius Brussee.

Cite

@software{brussee2026caveman,
  author = {Brussee, Julius},
  title  = {Caveman: why many token when few do trick},
  year   = {2026},
  url    = {https://github.com/JuliusBrussee/caveman}
}

🪨 Caveman save you token. Star cost zero. Fair trade.

_{Docs ·
Install matrix ·
Honest numbers ·
Contributing ·
Caveman Cloud ·
Issues}

Cost Efficiency on Producthunt daily