ai-change-impact

ai-change-impact is a skill for Claude Code from starbringer/AI-Insights. It costs 169 tokens per session (1,665 once invoked), scanned A, original, MIT.

A measurement workflow for comparing the cost of AI coding work before and after a change. It uses recorded usage data to separate differences caused by API calls, context, or other measured factors.

In plain words
What is it for?
Use it to compare two sessions, compare two time periods, find when a harness change occurred, and explain whether the change improved or worsened cost.
Why use it?
It answers whether a configuration or workflow change actually saved money instead of relying on impressions. It also reports caveats when the comparison may not be reliable.

Skill for Claude Code

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

Good fit Use it to compare two sessions, compare two time periods, find when a harness change occurred, and explain whether the change improved or worsened cost.

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Install with agentmods
npx agentmods add skills/starbringer/ai-insights/ai-change-impact
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 starbringer/AI-Insights --skill ai-change-impact
Clone the repo
git clone --depth 1 https://github.com/starbringer/AI-Insights

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 ai-change-impact

README.md
[![agentmods](https://agentmods.dev/badge/skills/starbringer/ai-insights/ai-change-impact/github.svg)](https://agentmods.dev/skills/starbringer/ai-insights/ai-change-impact)
Your own site
<a href="https://agentmods.dev/skills/starbringer/ai-insights/ai-change-impact"><img src="https://agentmods.dev/badge/skills/starbringer/ai-insights/ai-change-impact/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 ai-change-impact

Your own site · 80×15
<a href="https://agentmods.dev/skills/starbringer/ai-insights/ai-change-impact"><img src="https://agentmods.dev/badge/skills/starbringer/ai-insights/ai-change-impact.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 169 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,665 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 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 $0.00169 $0.01665
Opus 5 $0.00084 $0.00833
Sonnet 5 $0.00034 $0.00333
Haiku 4.5 $0.00017 $0.00167

Measured 11d ago against content hash 890b2e849ecb, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

ai-change-impact 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 11d 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.

assets/skills/ai-change-impact/SKILL.md · 137 lines

How it starts

The opening of the file, as written. The whole thing — 137 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AI change impact

Answer one question: did that change save money, and how much?

Three rules govern the whole analysis:

  • The arithmetic is the app's job, the judgement is yours. compare_runs and compare_periods return an exact decomposition. Your value is deciding whether the comparison is fair and saying so plainly.
  • Report the caveats. Both tools return a caveats array generated from the actual data. Never drop it. A saving the user cannot rely on is worse than no number, because they will act on it.
  • You never edit config here. This skill measures. If the answer is "it got worse", say that and stop; fixing it is a separate request.

1. Pick the mode

The user has… Mode Tool
Two runs to compare (re-ran the same task) Run vs run compare_runs
Just kept working after the change Period vs period compare_periods
A change but no idea when Find the split first get_harness_changes

Run mode is exact but n = 1. Period mode is noisier but reflects real use. When both are possible, do both: they answer different questions, and agreement between them is the strongest evidence you can offer.

2. Establish scope and horizon

Run list_providers, then pick the provider: the one the user named, the only one with hasData: true, or ask. Pass it as provider on every call — a harness diff needs a concrete provider and is skipped for "all".

Then check get_data_retention before asking for any window. Records older than retentionDays are deleted, not hidden. If the "before" side predates oldestRetainedTimestamp, say so directly:

Your retention is set to 30 days, so nothing before 2026-06-29 exists any more — that period cannot be compared. Raise the retention setting now if you want this question answerable next month; the data cannot be recovered once deleted.

Do not fall back to a window you can answer and present it as the answer.

3. Find the split point

Read the full file on GitHub · 137 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. 11d ago First seen · 137 lines · 0 tokens per session scan A 890b2e849ecb

Subscribe to this mod's changes

ai-change-impact is a skill published in the GitHub repository starbringer/AI-Insights (2 stars, last pushed 22d ago), licensed MIT. It adds 169 tokens to every session and 1,665 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 2026-08-31.

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