harness-optimizer

harness-optimizer is an agent for Claude Code from KratosAR/claude-code-arsenal. It costs 21 tokens per session (202 once invoked), scanned A, a copy of harness-optimizer, MIT.

A tool for reviewing and improving the setup that controls how coding agents work, called an agent harness. It examines configuration such as hooks, evaluations, model routing, context, and safety settings.

In plain words
What is it for?
Use it to audit an agent setup, choose the most useful configuration changes, apply them, and compare results before and after. It is intended to work across Claude Code, Cursor, OpenCode, and Codex.
Why use it?
It helps identify configuration problems that reduce reliability, increase cost, or slow down agent work. Changes are kept small, reversible, and measurable.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: model in frontmatter; mentions Claude Code; mentions Codex.

Part of the arsenal-core plugin — 43 skills, 15 agents shipped together

Good fit Use it to audit an agent setup, choose the most useful configuration changes, apply them, and compare results before and after. It is intended to work across Claude Code, Cursor, OpenCode, and Codex.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/kratosar/claude-code-arsenal/harness-optimizer
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.

Clone the repo
git clone --depth 1 https://github.com/KratosAR/claude-code-arsenal

Made for: Claude Code.

Or install arsenal-core, the plugin that ships this one along with the rest of its 43 skills, 15 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 harness-optimizer

README.md
[![agentmods](https://agentmods.dev/badge/agents/kratosar/claude-code-arsenal/harness-optimizer/github.svg)](https://agentmods.dev/agents/kratosar/claude-code-arsenal/harness-optimizer)
Your own site
<a href="https://agentmods.dev/agents/kratosar/claude-code-arsenal/harness-optimizer"><img src="https://agentmods.dev/badge/agents/kratosar/claude-code-arsenal/harness-optimizer/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 harness-optimizer

Your own site · 80×15
<a href="https://agentmods.dev/agents/kratosar/claude-code-arsenal/harness-optimizer"><img src="https://agentmods.dev/badge/agents/kratosar/claude-code-arsenal/harness-optimizer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 21 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 202 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.
Origin 94% copy Near-identical to another mod 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 $0.00021 $0.00202
Opus 5.5 $0.00008 $0.00081
Sonnet 5.5 $0.00004 $0.00040
Haiku 4.5 $0.00002 $0.00020

Measured 1mo ago against content hash a0f42e525781, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

harness-optimizer 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 1mo ago.

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

This is a copy

94% identical to harness-optimizer — 5 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

arsenal-core/agents/harness-optimizer.md · 36 lines

What it actually says

You are the harness optimizer.

Mission

Raise agent completion quality by improving harness configuration, not by rewriting product code.

Workflow

  1. Run /harness-audit and collect baseline score.
  2. Identify top 3 leverage areas (hooks, evals, routing, context, safety).
  3. Propose minimal, reversible configuration changes.
  4. Apply changes and run validation.
  5. Report before/after deltas.

Constraints

  • Prefer small changes with measurable effect.
  • Preserve cross-platform behavior.
  • Avoid introducing fragile shell quoting.
  • Keep compatibility across Claude Code, Cursor, OpenCode, and Codex.

Output

  • baseline scorecard
  • applied changes
  • measured improvements
  • remaining risks
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. 1mo ago First seen · 36 lines · 21 tokens per session scan A a0f42e525781

Subscribe to this mod's changes

harness-optimizer is an agent published in the GitHub repository KratosAR/claude-code-arsenal (2 stars, last pushed 2mo ago), licensed MIT. It adds 21 tokens to every session and 202 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 94% identical to harness-optimizer, differing in 5 lines, and is treated as a copy.

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