Agent skill

Cost Diff

Snapshot delta between two cost-summary JSON outputs. An agent skill from ruvnet/ruflo.

MITAuto-check: notes

Install Cost Diff

skills CLI

$ npx skills add ruvnet/ruflo --skill cost-diff -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install ruvnet/ruflo cost-diff --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/ruvnet/ruflo.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/ruflo-cost-tracker/skills/cost-diff .claude/skills/cost-diff && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "cost-diff" agent skill from https://github.com/ruvnet/ruflo/tree/main/plugins/ruflo-cost-tracker/skills/cost-diff into .claude/skills/cost-diff/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cost-diff", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/ruvnet/ruflo/tree/main/plugins/ruflo-cost-tracker/skills/cost-diff

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add ruvnet/ruflo --skill cost-diff -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install ruvnet/ruflo cost-diff --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/ruvnet/ruflo.git skills-src && mkdir -p .agents/skills && cp -r skills-src/plugins/ruflo-cost-tracker/skills/cost-diff .agents/skills/cost-diff && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "cost-diff" agent skill from https://github.com/ruvnet/ruflo/tree/main/plugins/ruflo-cost-tracker/skills/cost-diff into .agents/skills/cost-diff/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cost-diff", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add ruvnet/ruflo --skill cost-diff -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install ruvnet/ruflo cost-diff --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/ruvnet/ruflo.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/plugins/ruflo-cost-tracker/skills/cost-diff .cursor/skills/cost-diff && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "cost-diff" agent skill from https://github.com/ruvnet/ruflo/tree/main/plugins/ruflo-cost-tracker/skills/cost-diff into .cursor/skills/cost-diff/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cost-diff", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/ruvnet/ruflo.git --path plugins/ruflo-cost-tracker/skills/cost-diff

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add ruvnet/ruflo --skill cost-diff -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install ruvnet/ruflo cost-diff --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/ruvnet/ruflo.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/plugins/ruflo-cost-tracker/skills/cost-diff .gemini/skills/cost-diff && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "cost-diff" agent skill from https://github.com/ruvnet/ruflo/tree/main/plugins/ruflo-cost-tracker/skills/cost-diff into .gemini/skills/cost-diff/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cost-diff", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install ruvnet/ruflo cost-diff

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add ruvnet/ruflo --skill cost-diff -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/ruvnet/ruflo.git skills-src && mkdir -p .github/skills && cp -r skills-src/plugins/ruflo-cost-tracker/skills/cost-diff .github/skills/cost-diff && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "cost-diff" agent skill from https://github.com/ruvnet/ruflo/tree/main/plugins/ruflo-cost-tracker/skills/cost-diff into .github/skills/cost-diff/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cost-diff", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add ruvnet/ruflo --skill cost-diff -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install ruvnet/ruflo cost-diff --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/ruvnet/ruflo.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/plugins/ruflo-cost-tracker/skills/cost-diff .opencode/skills/cost-diff && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "cost-diff" agent skill from https://github.com/ruvnet/ruflo/tree/main/plugins/ruflo-cost-tracker/skills/cost-diff into .opencode/skills/cost-diff/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cost-diff", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: cost-diff
GitHub stars: 74k
Token cost: ~1.3k tokens
SKILL.md length: 474 words
Files: 1
Skills in repo: 264
Repo updated: Oct 7, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Snapshot delta between two cost-summary JSON outputs. An agent skill from ruvnet/ruflo.

Works in 7 steps: Load --baseline and --current JSON… → Sanity check: both must have… → Per-key delta: byTier… → …
SKILL.md covers Algorithm, PR-gate workflow, --alert-on-class-pct (iter 86) and Smoke transcript (synthetic…, plus 3 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Cost Diff is an agent skill from ruvnet/ruflo. Snapshot delta between two cost-summary JSON outputs. PR-level cost regression detection — answers "what changed between these two specific snapshots?". Pairs with cost-summary's stable JSON contract.

Its SKILL.md is about 1.3k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

The repository describes itself as: 🌊 The original agent harness. Deploy intelligent multi-player swarms, coordinate autonomous workflows, and build conversational AI systems. Features adaptive memory…. The licence is MIT.

Example prompts

“what changed between these two specific snapshots?”
“/cost-diff”

Requirements

Pre-approved tools (allowed-tools): Bash

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

Load --baseline and --current JSON snapshots.
Sanity check: both must have total_cost_usd + sessionCount (cost-summary shape).
Per-key delta: byTier (haiku/sonnet/opus) and byModel (each model).
Each entry tagged added / removed / changed based on
Sort table by |delta| descending so the biggest movers are at the top.
alert-on-pct N: exit 1 when total_pct > N.
alert-on-usd N: exit 1 when total_delta_usd > N.

What it can do on your machine

Read from SKILL.md and the folder at commit de590e1. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves these tools, so the agent can use them without asking each time:
- Bash
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are bash).
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Cost Diff loads about 1.3k tokens when it runs. Until then it costs about 53 tokens; SKILL.md has 474 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~53
When it runs · the whole SKILL.md, loaded when a task matches: ~1.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check: notes

The automated check noted patterns worth knowing about, such as sudo or a known installer.

NotePre-approves every shell command (allowed-tools: Bash)SKILL.md
```
allowed-tools: Bash
```

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from ruvnet/ruflo at commit de590e1, republished under its MIT licence (© ruvnet). 474 words, ~1,254 tokens.

Download SKILL.mdSave it as .claude/skills/cost-diff/SKILL.md (or your agent's skills folder).

name: cost-diff
description: Snapshot delta between two cost-summary JSON outputs. PR-level cost regression detection — answers "what changed between these two specific snapshots?". Pairs with cost-summary's stable JSON contract.
allowed-tools: Bash
argument-hint: --baseline <baseline.json> --current <current.json> [--alert-on-pct N] [--alert-on-usd N] [--alert-on-class-pct <class>:N[,<class>:N]] [--format table|json]

PR-level cost regression detection. Where cost-counterfactual compares to HYPOTHETICAL baselines (always-haiku/sonnet/opus) and cost-burn compares latest bucket to PRIOR MEAN, cost-diff compares two SPECIFIC known-good snapshots.

Question	Skill
"What would we have spent at always-X?"	`cost-counterfactual`
"Is daily burn accelerating vs prior mean?"	`cost-burn`
"Did THIS PR add spend vs main?"	`cost-diff` ← this

Algorithm

Implementation: scripts/diff.mjs. Consumes the stable JSON contract from cost summary --format json.

Load --baseline and --current JSON snapshots.
Sanity check: both must have total_cost_usd + sessionCount (cost-summary shape).
Per-key delta: byTier (haiku/sonnet/opus) and byModel (each model).
Each entry tagged added / removed / changed based on baseline / current zero-ness.
Sort table by |delta| descending so the biggest movers are at the top.
--alert-on-pct N: exit 1 when total_pct > N.
--alert-on-usd N: exit 1 when total_delta_usd > N. Both can be set; first to trigger wins.

PR-gate workflow

bash

# Capture baseline (e.g. on main, via the cost-tracker-smoke CI workflow)
cost summary --format json > baseline.json

# On the PR branch, capture current state
cost summary --format json > current.json

# Compare; fail the PR if total spend grew >10% OR >$5
cost diff --baseline baseline.json --current current.json \
          --alert-on-pct 10 --alert-on-usd 5.00

The combination of both flags catches:

Percent-only fires: a small absolute change but a meaningful shift (e.g. doubling from $0.10 to $0.20 hits +100% but only +$0.10).
USD-only fires: a large absolute change with a small percent (e.g. growing from $100 to $110 is only +10% but +$10).

Either signal can fail the PR independently — they're OR'd.

--alert-on-class-pct (iter 86)

The two USD-level thresholds above miss a regression class: when ONE token type grows disproportionately even though total spend grows modestly. Example: a PR introduces a verbose context-cache pattern, total spend grows only 10% (under --alert-on-pct 50), but cache_write tokens grow 900%. The iter-82 driver hides inside the USD signal.

--alert-on-class-pct cache_write:50 exits 1 when cache_write tokens grow more than 50% baseline → current. Multiple classes can be checked in one flag (comma-separated):

bash

cost diff --baseline baseline.json --current current.json \
          --alert-on-class-pct cache_write:50,output:25

First class to breach wins. Valid classes: input | output | cache_write | cache_read.

Recommended PR-gate triad:

bash

cost diff --baseline ... --current ... \
          --alert-on-pct 25 \
          --alert-on-usd 5.00 \
          --alert-on-class-pct cache_write:100

Three orthogonal signals — pct (total grew), usd (large absolute jump), class-pct (composition shifted). Each catches what the others miss; AND-of-OR semantics means any one firing fails the PR.

Show full SKILL.md (157 more words)Show less

Smoke transcript (synthetic baseline + current)

| Total spend       | $1.000000 | $1.500000 | +$0.500000 | 50.00% |
| Sessions          | 10        | 13        | +3         | 30.00% |

## By tier
| opus   | $0      | $0.60   | +$0.600000 | new      | added   |
| sonnet | $0.70   | $0.50   | -$0.200000 | -28.57%  | changed |
| haiku  | $0.30   | $0.40   | +$0.100000 | 33.33%   | changed |

Notice the table is sorted by absolute delta, not alphabetically — the biggest mover (opus newly added) bubbles to the top. Operators reading top-down see "what mattered" first.

Exit codes

Exit	Meaning
0	No alert, OR no thresholds set
1	--alert-on-pct or --alert-on-usd threshold exceeded
2	Config error (missing files, invalid JSON, malformed snapshot)

Status column

Status	Meaning
`added`	This tier/model was $0 in baseline, >$0 in current
`removed`	This tier/model was >$0 in baseline, $0 in current
`changed`	Both baseline and current >$0; delta is the difference

Entries with baseline === 0 && current === 0 are dropped (nothing to report).

Composition with cost-summary

cost-diff is the SECOND HALF of a contract that cost-summary started: the stable JSON shape from cost summary --format json. Both pieces have been frozen — adding fields to summary is fine; renaming or removing isn't.

If you're consuming snapshots elsewhere (dashboards, alerting), the same shape works — cost-diff is just one consumer.

Files

Just SKILL.md in plugins/ruflo-cost-tracker/skills/cost-diff of ruvnet/ruflo.

Open the folder on GitHubat commit de590e1

Compare with similar skills

Cost Diff next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Cost Diff compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Cost Diff this skillruvnet/ruflo	74k	—	~1.3k	Automated safety check: Notes	MIT	today
Cost Trackingaffaan-m/ECC	274k	1 repos	~1.3k	Automated safety check: Pass	MIT	2 days ago
Cost Trackingaffaan-m/ECC	274k	—	~829	Automated safety check: Pass	MIT	2 days ago
Analyze Cloud Costslangfuse/langfuse	35k	—	~672	Automated safety check: Pass	Custom licence	today
Output Dev Workflow Costgrowthxai/output	440	—	~1.4k	Automated safety check: Notes	Apache-2.0	today
Cloud Cost Optimizationwshobson/agents	40k	13 repos	~1.7k	Automated safety check: Pass	MIT	2 days ago

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Questions about Cost Diff

What does Cost Diff do?

Snapshot delta between two cost-summary JSON outputs. An agent skill from ruvnet/ruflo. Cost Diff is an agent skill from ruvnet/ruflo. Snapshot delta between two cost-summary JSON outputs.

How do I install Cost Diff in Claude Code?

Run `npx skills add ruvnet/ruflo --skill cost-diff -a claude-code`. Or copy the skill folder (plugins/ruflo-cost-tracker/skills/cost-diff in ruvnet/ruflo) into .claude/skills/cost-diff in your project. Claude Code loads it when a task matches its description.

How do I install Cost Diff in Codex?

Run `npx skills add ruvnet/ruflo --skill cost-diff -a codex`. Or copy the skill folder (plugins/ruflo-cost-tracker/skills/cost-diff in ruvnet/ruflo) into .agents/skills/cost-diff in your project. Codex loads it when a task matches its description.

Can I use Cost Diff in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add ruvnet/ruflo --skill cost-diff -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/cost-diff, .gemini/skills/cost-diff, .github/skills/cost-diff and .opencode/skills/cost-diff in your project.

What does Cost Diff need to run?

SKILL.md names no scripts, command-line tools or credentials: Cost Diff is instructions for the agent only. Its frontmatter pre-approves these tools: Bash.

Does Cost Diff access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Cost Diff safe to install?

Our automated static check of SKILL.md found notes only (pre-approves every shell command (allowed-tools: bash)), nothing it rates as a warning. It is not a guarantee. Review the folder before installing.

What licence does Cost Diff use?

Cost Diff is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Cost Diff use?

About 1.3k tokens (SKILL.md is roughly 5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Cost Diff?

Skills that share tags, products or a category with Cost Diff: Cost Tracking (affaan-m/ECC, 274k stars), Cost Tracking (affaan-m/ECC, 274k stars), Analyze Cloud Costs (langfuse/langfuse, 35k stars) and Output Dev Workflow Cost (growthxai/output, 440 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Cost Diff?

ruvnet (a GitHub user) maintains it in ruvnet/ruflo, which has 74,012 GitHub stars. The repository holds 264 skills in this directory. The repository was last updated on October 7, 2026.

Source: ruvnet/ruflo on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Cost Diff

Install Cost Diff

Facts

At a glance

What it does

Example prompts

Requirements

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Algorithm

PR-gate workflow

--alert-on-class-pct (iter 86)

Smoke transcript (synthetic baseline + current)

Exit codes

Status column

Composition with cost-summary

Files

Compare with similar skills

Similar skills

Cost Tracking

Cost Tracking

Analyze Cloud Costs

Output Dev Workflow Cost

Cloud Cost Optimization

Accesslint Diff

More from ruvnet/ruflo

AgentDB Pattern Memory

Security Audit Scanner

SPARC Development Methodology

Swarm Orchestration

Ruflo Multi-Agent Orchestration

Agent Coordination

Questions about Cost Diff