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Agent skill

Histogram Extension

by nwjs in nwjs/chromium.src

Extension pipeline to bump expiration dates of Chromium UMA histograms.

BSD-3-ClauseAuto-check passedDevelopment

Install Histogram Extension

skills CLI
$ npx skills add nwjs/chromium.src --skill histogram-extension -a claude-code

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

GitHub CLI
$ gh skill install nwjs/chromium.src histogram-extension --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/nwjs/chromium.src.git skills-src && mkdir -p .claude/skills && cp -r skills-src/agents/projects/code-health/histogram-extension .claude/skills/histogram-extension && 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/

Facts

Skill name
histogram-extension
GitHub stars
160
Token cost
~503 tokens
SKILL.md length
225 words
Files
3 (incl. scripts, references)
Skills in repo
64
Repo updated
First seen
Licence
BSD-3-Clause

At a glance

Extension pipeline to bump expiration dates of Chromium UMA histograms.

  • Works in 3 steps: Discovery & Locate (Delegated) → Update the Expiration Date → Commit and CL creation
  • Tasks that involve Code quality
  • SKILL.md covers Overview and Workflow
  • Runs Python scripts from its folder; calls python3

What it does

Histogram Extension is an agent skill from nwjs/chromium.src. Extension pipeline to bump expiration dates of Chromium UMA histograms.

Its SKILL.md is about 500 tokens, which your agent loads only when the skill is triggered. The skill folder holds 4 other files, including scripts and reference files (for example `references/bug_discovery.md` and `scripts/find_candidates.py`).

It sits in Development, covering Code quality. The repository describes itself as: Chromium codebase with NW.js modifications. Based on https://chromium.googlesource.com/chromium/src.git. The licence is BSD-3-Clause.

When your agent uses it

  • Tasks that involve Code quality

Example prompts

  • “/histogram-extension”

Requirements

  • Python 3

Workflow steps

3 steps, taken from the step headings in SKILL.md.

  1. Discovery & Locate (Delegated)
  2. Update the Expiration Date
  3. Commit and CL creation

What it can do on your machine

Read from SKILL.md and the folder at commit a9e8946. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships 1 file in scripts/ (Python), which the agent can run.

    Shell commands in SKILL.md call:

    • python3

    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

Histogram Extension loads about 503 tokens when it runs, and up to ~1.3k if it reads all its reference files. Until then it costs about 23 tokens; SKILL.md has 225 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~23
When it runs · the whole SKILL.md, loaded when a task matches
~503
With references · SKILL.md plus every file in references/, read only if the agent opens them
~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 passed

The automated check found no risky patterns in SKILL.md.

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); the scripts in this folder are not scanned.

SKILL.md

The full file from nwjs/chromium.src at commit a9e8946, republished under its BSD-3-Clause licence (© nwjs). 225 words, ~503 tokens.

Download SKILL.mdSave it as .claude/skills/histogram-extension/SKILL.md (or your agent's skills folder). This skill also uses 2 other files; get the full folder from GitHub.
name
histogram-extension
description
Extension pipeline to bump expiration dates of Chromium UMA histograms.

histogram-extension

Overview

This skill outlines how you (the agent) should automatically locate and extend the expiration dates of UMA histograms in Chromium that have expired or are nearing expiration.

Workflow

1. Discovery & Locate (Delegated)
  • AI-Led Discovery: Delegate to the generalist sub-agent to find histograms that are nearing expiration if none are provided. Run:
    bash
    python3 scripts/find_candidates.py --count 1
  • Bug Checking: Check references/bug_discovery.md and Buganizer to ensure the metric isn't already being extended in another ticket.
  • Locate: Look inside tools/metrics/histograms/metadata/*/histograms.xml to find the target metric.
  • Look for the <histogram name="TARGET_NAME" expires_after="YYYY-MM-DD"> definition (or enum=... expires_after="...").
2. Update the Expiration Date
  • Ask the user (or read from the brief) what the new expiration date should be. If none is specified, recommend extending by +6 months or +1 year (in YYYY-MM-DD format).
  • Carefully replace the expires_after="YYYY-MM-DD" string constraint inline, being sure not to modify other attributes.
3. Commit and CL creation

  • Create the Git commit with a descriptive, code-health aligned message using the metadata template below.

  • Skill Name: histogram-extension

  • Branch Name: histogram-extension-[histogram-name]

  • Commit Hashtag: Code Health

  • Cleanup Title: Extend expiration for [Histogram Name]

  • Cleanup Description: This metric is still actively needed for telemetry monitoring. Extending expiration to prevent data loss.

  • Parent Bug: 499059543

  • Bug ID: The resolved <Bug ID> from the Bug Checking step.

  • Upload the CL to Gerrit and add the appropriate metadata reviewers depending on the OWNERS file located in tools/metrics/histograms/metadata/{category}/OWNERS.

© nwjs, BSD-3-Clause. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files (scripts, references) in agents/projects/code-health/histogram-extension of nwjs/chromium.src.

  • SKILL.md
  • references/bug_discovery.md
  • scripts/find_candidates.py

Open the folder on GitHubat commit a9e8946

Compare with similar skills

Histogram Extension 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.

Histogram Extension compared with similar skills
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Histogram Extension this skillnwjs/chromium.src160—~503Automated safety check: PassBSD-3-Clause
Install Anti-Slop Oxlint Rulesdmmulroy/anti-slop5.3k1 repos~2.2kAutomated safety check: PassMIT
WooCommerce Code Reviewwoocommerce/woocommerce11k3 repos~1.1kAutomated safety check: PassCustom licence
Systematic Code Refactoringluongnv89/claude-howto42k—~3kAutomated safety check: PassMIT
Constraint-Driven Developmentaddyosmani/agent-skills103k2 repos~5.2kAutomated safety check: PassMIT
Skill Doli Code ReviewDolibarr/dolibarr7.7k1 repos~1.1kAutomated safety check: PassMIT

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Categories

Questions about Histogram Extension

What does Histogram Extension do?

Extension pipeline to bump expiration dates of Chromium UMA histograms. src. Extension pipeline to bump expiration dates of Chromium UMA histograms.

When should I use Histogram Extension?

Histogram Extension fits situations like: tasks that involve Code quality.

How do I install Histogram Extension in Claude Code?

Run `npx skills add nwjs/chromium.src --skill histogram-extension -a claude-code`. Or copy the skill folder (agents/projects/code-health/histogram-extension in nwjs/chromium.src) into .claude/skills/histogram-extension in your project. Claude Code loads it when a task matches its description.

How do I install Histogram Extension in Codex?

Run `npx skills add nwjs/chromium.src --skill histogram-extension -a codex`. Or copy the skill folder (agents/projects/code-health/histogram-extension in nwjs/chromium.src) into .agents/skills/histogram-extension in your project. Codex loads it when a task matches its description.

Can I use Histogram Extension 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 nwjs/chromium.src --skill histogram-extension -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/histogram-extension, .gemini/skills/histogram-extension, .github/skills/histogram-extension and .opencode/skills/histogram-extension in your project.

What does Histogram Extension need to run?

Going by SKILL.md and its folder, Histogram Extension needs Python for the scripts in its folder and the command-line tools its instructions call (python3). Our summary lists: Python 3.

Does Histogram Extension 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 Histogram Extension safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Histogram Extension use?

Histogram Extension is published under the BSD-3-Clause licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Histogram Extension use?

About 503 tokens (SKILL.md is roughly 2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 796 tokens, read only when the agent opens those files.

What are the alternatives to Histogram Extension?

Skills that share tags, products or a category with Histogram Extension: Install Anti-Slop Oxlint Rules (dmmulroy/anti-slop, 5.3k stars), WooCommerce Code Review (woocommerce/woocommerce, 11k stars), Systematic Code Refactoring (luongnv89/claude-howto, 42k stars) and Constraint-Driven Development (addyosmani/agent-skills, 103k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Histogram Extension?

nwjs (a GitHub organization) maintains it in nwjs/chromium.src, which has 160 GitHub stars. The repository holds 64 skills in this directory. The repository was last updated on October 3, 2026.

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