arbor

arbor is a skill for Claude Code from K-Dense-AI/scientific-agent-skills. It costs 73 tokens per session (3,707 once invoked), scanned A, original, MIT.

A system for repeatedly improving a codebase, data pipeline, prompt, or other working artifact against a measurable goal. It tests competing ideas, records what was learned, and keeps changes that also perform well on separate checks.

In plain words
What is it for?
Use it to run and organize repeated experiments on software, training methods, agent setups, data pipelines, or prompts.
Why use it?
It prevents lessons from being lost across many experiments and reduces the risk of tuning an artifact only to the feedback used during development.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: mentions subagents.

Good fit Use it to run and organize repeated experiments on software, training methods, agent setups, data pipelines, or prompts.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/k-dense-ai/scientific-agent-skills/arbor
About the project

Scientific Agent Skills is a collection of reusable procedures that give AI agents capabilities for scientific research across areas such as biology, chemistry, medicine, and drug discovery. It is used by researchers and by people building AI scientist workflows with compatible coding agents. The catalogue contains many of the project's skills and supporting instructions.

K-Dense-AI/scientific-agent-skills · 50,453 stars · on GitHub · arxiv.org

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 K-Dense-AI/scientific-agent-skills --skill arbor
Clone the repo
git clone --depth 1 https://github.com/K-Dense-AI/scientific-agent-skills

Made for: Claude Code.

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 arbor

README.md
[![agentmods](https://agentmods.dev/badge/skills/k-dense-ai/scientific-agent-skills/arbor/github.svg)](https://agentmods.dev/skills/k-dense-ai/scientific-agent-skills/arbor)
Your own site
<a href="https://agentmods.dev/skills/k-dense-ai/scientific-agent-skills/arbor"><img src="https://agentmods.dev/badge/skills/k-dense-ai/scientific-agent-skills/arbor/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 arbor

Your own site · 80×15
<a href="https://agentmods.dev/skills/k-dense-ai/scientific-agent-skills/arbor"><img src="https://agentmods.dev/badge/skills/k-dense-ai/scientific-agent-skills/arbor.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 73 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,707 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 1 Oct 2026
  • Snyk pass 1 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 $0.00073 $0.03707
Opus 5.5 $0.00029 $0.01483
Sonnet 5.5 $0.00015 $0.00741
Haiku 4.5 $0.00007 $0.00371

Measured 14d ago against content hash aae219831d92, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

arbor 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 14d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/tree.py), 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

6 near-identical copies found in the catalogue:

  • arbor — 100% identical, 95 lines differ
  • arbor — 100% identical, 97 lines differ
  • arbor — 100% identical, 97 lines differ
  • arbor — 100% identical, 97 lines differ
  • arbor — 100% identical, 95 lines differ
  • arbor — 89% identical, 78 lines differ
skills/arbor/SKILL.md · 194 lines

How it starts

The opening of the file, as written. The whole thing — 194 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Arbor — Autonomous Optimization via Hypothesis Tree Refinement

Overview

This skill runs an Autonomous Optimization (AO) loop: starting from an existing artifact and a measurable objective, improve it through many rounds of experiment and evaluation — without step-by-step human supervision, while checking for overfitting to the development signal. It's the right tool when the bottleneck isn't writing one good change, but organizing dozens of trials so that lessons accumulate instead of evaporating.

It implements Hypothesis Tree Refinement (HTR) from Arbor (Jin et al., 2026). The key idea: keep the research state in a persistent hypothesis tree rather than in conversation history. Each node binds a hypothesis, the distilled insight it produced, and a pointer to the artifact version that realizes it. You play the long-lived coordinator that owns this tree and decides where to search; short-lived executor subagents test one hypothesis each in isolated git worktrees and report back. A held-out merge gate admits a change only when it improves on a test evaluator executors do not optimize against. This is what turns trial-and-error into cumulative, auditable research.

Use the scripts/tree.py state manager for all the bookkeeping (creating nodes, writing evidence, propagating insights, pruning, the merge gate, the Observe projection). It records scores and decisions; it does not run evaluators, create worktrees, verify Git refs, or merge Git branches. Only the coordinator writes shared state, serially; executors return evidence. The helper has no multi-writer locking. Its JSON schema is separate from upstream Arbor checkpoints.

When to use this skill

Reach for Arbor when the task is iterative improvement of a concrete artifact under an evaluator:

  • Model training: optimizer/architecture/recipe changes to lower loss or hit a target in fewer steps.
  • Harness/agent engineering: raising pass rate or accuracy of an agent loop, search harness, or tool-use scaffold.
  • Data synthesis: improving a generation/filtering pipeline judged by downstream model behavior.
  • Benchmark optimization: MLE-bench / Kaggle-style "improve the submission" tasks.
  • Prompt/system optimization where you can score outputs automatically.

Read the full file on GitHub · 194 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. 14d ago Changed · +18 lines · -144 tokens per session aae219831d92
  2. 15d ago Changed · +6 lines 8c028bea4afe
  3. 1mo ago Changed · +17 lines 156bc720de44
  4. 1mo ago First seen · 153 lines · 217 tokens per session scan A 1825f2a08f47

Subscribe to this mod's changes

arbor is a skill published in the GitHub repository K-Dense-AI/scientific-agent-skills (50,453 stars, last pushed today), licensed MIT. It adds 73 tokens to every session and 3,707 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.

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