delta

delta is a skill for Claude Code, Codex from melodic-software/claude-code-plugins. It costs 152 tokens per session (1,787 once invoked), scanned A, original, MIT.

A change-focused rerun of an instruction-placement audit that reports only new or changed findings, broken rule patterns, and index drift.

In plain words
What is it for?
Use it when checking instruction rules after repository changes or on a regular schedule.
Why use it?
It prevents repeat audits from making you review the same findings again, keeping attention on what changed since the previous run.

Skill for Claude CodeCodex

Installs and runs on its own, but its text points at files inside its plugin — anything it tells you to read at a ${CLAUDE_PLUGIN_ROOT} path is only there once the plugin is installed. Installing the plugin gets both.

Part of the instruction-placement plugin — 3 skills shipped together

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.

agentmods
npx agentmods add skills/melodic-software/claude-code-plugins/delta
Any agent
npx skills add melodic-software/claude-code-plugins --skill delta
Clone the repo
git clone --depth 1 https://github.com/melodic-software/claude-code-plugins

Made for: Claude Code, Codex.

Or install instruction-placement, the plugin that ships this one along with the rest of its 3 skills.

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 delta

README.md
[![agentmods](https://agentmods.dev/badge/skills/melodic-software/claude-code-plugins/delta.svg)](https://agentmods.dev/skills/melodic-software/claude-code-plugins/delta)
Your own site
<a href="https://agentmods.dev/skills/melodic-software/claude-code-plugins/delta"><img src="https://agentmods.dev/badge/skills/melodic-software/claude-code-plugins/delta.svg" alt="Measured on agentmods" height="20"></a>
Per session 152 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,787 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00152 $0.01787
Opus 5 $0.00076 $0.00894
Sonnet 5 $0.00030 $0.00357
Haiku 4.5 $0.00015 $0.00179

Measured yesterday against content hash f7562037b376, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

delta 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 yesterday.

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.

plugins/instruction-placement/skills/delta/SKILL.md · 130 lines

How it starts

The opening of the file, as written. The whole thing — 130 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Pre-computed context

!"${CLAUDE_PLUGIN_ROOT}/scripts/precompute.sh" audit 2>/dev/null || echo "- Orientation unavailable"

Purpose

A full audit is worth running rarely and reading carefully. This is the lane for the other times: it answers what moved, so a repeat run costs attention proportional to actual change.

The failure it exists to prevent is a specific one. An audit re-run that re-presents the same forty findings the operator already worked through trains them to skim, and a skimmed report is how a bad migration gets approved. Reporting only movement keeps the signal-to-noise ratio survivable on a cadence.

Read these first

Read For
../../context/findings-artifact.md Status vocabulary, re-run merge semantics, where the artifact lives
../../context/routing-rubric.md Only when a genuinely new candidate needs classifying

This skill does not restate the merge semantics. The artifact contract owns them, and a second statement is a second thing to drift.

What counts as movement

Five shapes, in report order. Everything else is suppressed.

Shape Trigger Why it matters
new A candidate with no prior finding The only shape that needs fresh classification
changed A finding whose source content changed since the last run Its line range is stale; realign would excise the wrong text
broken-glob A rule glob that resolved before and does not now The rule stopped firing, silently, and nobody was told
index-drift The index no longer matches the rules on disk Deferred surfaces became unreachable from subagents
stale A finding whose source no longer exists The content was moved or deleted outside this plugin

broken-glob is the shape that most justifies running this on a cadence. A glob breaks when the code it described gets renamed or moved, an ordinary refactor, nowhere near the rules tree, with no signal at the time. Nothing else in the plugin notices between check runs.

Read the full file on GitHub · 130 lines

Files

What ships with it

1 file 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. yesterday First seen · 130 lines · 152 tokens per session scan A f7562037b376

Subscribe to this mod's changes

delta is a skill published in the GitHub repository melodic-software/claude-code-plugins (14 stars, last pushed yesterday), licensed MIT. It adds 152 tokens to every session and 1,787 once invoked, about $0.0008 per session on Opus 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 2026-09-03.

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