caveman-learn

caveman-learn is a skill for Claude Code from JuliusBrussee/caveman. It costs 76 tokens per session (2,739 once invoked), scanned A, original, Apache-2.0.

A guide for applying findings from a Caveman learning report, which ranks where an agent uses the most tokens.

In plain words
What is it for?
Use it to inspect costly context, approve targeted reductions, shorten an oversized CLAUDE.md file, or move repeated information into cavemem.
Why use it?
It helps identify and reduce unnecessary context or repeated instructions that increase language-model usage.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions CLAUDE.md; mentions subagents; mentions Claude Code.

Part of the caveman plugin — 22 skills, 9 commands, 3 agents shipped together

Good fit Use it to inspect costly context, approve targeted reductions, shorten an oversized CLAUDE.md file, or move repeated information into cavemem.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/juliusbrussee/caveman/caveman-learn
About the project

caveman is a skill and proxy for coding agents that shortens unnecessary explanatory prose so agents use fewer tokens while leaving code, commands, paths, and error messages unchanged. It is for people using coding agents who want terse responses and lower token use, including with Claude-based workflows. The catalogue entries contain its skills, commands, agents, instructions, and plugins.

JuliusBrussee/caveman · 114,861 stars · on GitHub · docs.caveman.so

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add JuliusBrussee/caveman --skill caveman-learn
Clone the repo
git clone --depth 1 https://github.com/JuliusBrussee/caveman

Made for: Claude Code.

Or install caveman, the plugin that ships this one along with the rest of its 22 skills, 9 commands, 3 agents.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for caveman-learn

README.md
[![agentmods](https://agentmods.dev/badge/skills/juliusbrussee/caveman/caveman-learn/github.svg)](https://agentmods.dev/skills/juliusbrussee/caveman/caveman-learn)
Your own site
<a href="https://agentmods.dev/skills/juliusbrussee/caveman/caveman-learn"><img src="https://agentmods.dev/badge/skills/juliusbrussee/caveman/caveman-learn/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for caveman-learn

Your own site · 80×15
<a href="https://agentmods.dev/skills/juliusbrussee/caveman/caveman-learn"><img src="https://agentmods.dev/badge/skills/juliusbrussee/caveman/caveman-learn.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 76 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,739 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • Socket pass 17 Oct 2026
  • Snyk pass 17 Oct 2026
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00076 $0.02739
Opus 5.5 $0.00030 $0.01096
Sonnet 5.5 $0.00015 $0.00548
Haiku 4.5 $0.00008 $0.00274

Measured 7d ago against content hash 05e803e80247, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

caveman-learn scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (tests/index.js, tests/skill-file.test.mjs), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

2 near-identical copies found in the catalogue:

skills/caveman-learn/SKILL.md · 177 lines

How it starts

The opening of the file, as written. The whole thing — 177 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are the Caveman Learn editing skill. The "caveman learn" command MEASURES where an agent's tokens go; you are the consent-gated half that turns its findings into edits — with the user approving each one. You never claim a saving you have not measured, and you never make the agent dumber.

New sinks you may see, and what they are for:

  • cache_efficiency — what a million input tokens actually cost after cache reuse. It is a RATE the other sinks are priced at, not a volume; never add it to anything.
  • tool_output_portfolio — the call shapes that dominate context, ranked.
  • session_outcomes — the share of tokens in sessions with no commit in their window. Correlational. Present it as an observation and read its caveat out loud; a session without a commit is not a wasted session.
  • subagent_spend — the share of context that ran in subagents. Visibility only. Do not turn it into advice to spawn fewer subagents.
  • procedure_repeat:* — a distillation candidate. See SKILL_DISTILLATION below.

Read the plan first:

  1. Run: caveman learn report --json Parse the caveman.learn.v1 JSON. Show the Cave Score, its four components, and the ranked token sinks. For each sink state its class and basis. Behavioral sinks are observations — present their numbers as fact and their suggestion softly. Do not turn a behavioral finding into an imperative.

    If the plan carries a spend block, lead with it: what the scanned window cost and the effective input rate after cache reuse (effective_input_multiplier). Rules you must not break when you show money:

    • Spend is what the window COST. It is never what a fix would return.
    • Say the window it covers. Never multiply it into a month, a year, or a run rate.
    • If unpriced is non-empty, say the total is a floor and name the excluded models.
    • Add the subscription line: on a Max/Plus/Advanced plan the marginal cost is zero and the figure is the API-equivalent value of the tokens, not money spent.
    • Never call any of it verified.

Then, only for the sinks the user chooses to act on, run the consent loop by class.

Before proposing a fix, you may run: caveman learn simulate <sink_id>. Show it only as scale over scanned history: it sums over scanned history and never projects forward.

REDUCIBLE (a heavy CLAUDE.md, a never-invoked skill):

  • Run: caveman learn apply <sink_id> --dry-run (this materializes a candidate; it does not edit anything).
  • Propose a concrete diff and show before -> after tokens/turn.
  • Ask the user yes or no. On yes, apply the edit with your own file tools.
  • Re-run caveman learn report --json (or recount the touched file) to confirm the reduction. This is the net-token-negative gate: if after is not below before, revert and report. Never keep an edit that does not reduce tokens/turn.

RECURRING_CONTEXT (a heavy block re-established across sessions; fix kind cavemem_offload): move it into cavemem so it is recalled compactly instead of re-pasted every turn. The candidate carries only a LOCATOR — never the block body.

  • Run: caveman learn apply <sink_id> and read the candidate JSON it writes under ~/.caveman/candidates/. Take only the locator, the numbers, and the proposed pointer text. Do not trust any body from the candidate; there is none.
  • Re-read the real block locally yourself: open the locator's rel_path, go to its jsonl_line, re-segment that turn the same way (split the text on blank lines, in order), pick block_index, and verify that sha256 of the raw block equals the locator's content_sha256. If it does not match, the file changed since the scan — abort this item.
  • Store it: write the real block byte for byte to a temp file with your file tool, then run: caveman mem remember --stdin < and capture the returned id. Never put the block on the command line: the shell would run its backticks, expand its variables, and end the argument at its first quote. Delete the temp file once the id is back.
  • Measure the gate honestly. before = the block's tokens/turn (it loaded every turn). after = the pointer's tokens/turn plus the recall cost. Get the recall cost by running caveman mem recall "" and reading tokens_added on the hit. If after is not below before, run caveman mem forget , leave the source untouched, and stop.
  • Trim the source and write the pointer. Remove the block from its CLAUDE.md or AGENTS.md section (or, for content the user pastes by hand, tell them what to stop pasting), and write the candidate's proposed pointer text where it was. The pointer names the recall path: caveman mem recall "" for the compact form, and caveman mem recover for the byte-exact original.
  • Never make the agent dumber: before you finish, confirm that caveman mem recall "" returns a hit AND a pointer is in place. If recall returns nothing, or you did not write a pointer, REVERT (caveman mem forget and restore the source). Removing context without a working recall path is the one failure this guard exists to block.
  • Re-measure and report the confirmed reduction and the recall path.

Read the full file on GitHub · 177 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 7d ago Changed · +2 lines 05e803e80247
  2. 24d ago Changed · +31 lines 466ce607aebf
  3. 1mo ago First seen · 144 lines · 76 tokens per session scan A 8b210c266f5c

Subscribe to this mod's changes

caveman-learn is a skill published in the GitHub repository JuliusBrussee/caveman (114,861 stars, last pushed today), licensed Apache-2.0. It adds 76 tokens to every session and 2,739 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.