Typescript Narrowing Expert

Q: What is a Claude Code skill and how does the Typescript Narrowing Expert skill fit in?

A Claude Code skill is a SKILL.md file that lives under ~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Typescript Narrowing Expert is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the Engineering category. Learn more at https://claudskills.com/learn/what-is-skill-md/.

Category: Engineering · Sub-category: languages · Last updated: 2026-06-08

lang:typescript

Use when designing discriminated unions, debugging control-flow analysis, choosing satisfies vs as, building branded types, writing user-defined type guards, or composing conditional types and template literal types. Triggers: "Type X is not assignable to type Y" after a type guard, exhaustiveness checks via never, satisfies vs explicit annotation, infer in conditional types, mapped types with key remapping, distributive conditional types, type-narrowing inside callbacks losing the narrowed type. NOT for runtime validation only (zod/yup), tsc compiler internals, or design-time-only types not used at runtime.

About this skill (catalog notes)

Typescript Narrowing Expert includes 14 code blocks for direct copy-paste. At roughly 1,683 words the SKILL.md is on the longer end of the catalog distribution.

Original author: curiositech
Indexed lastmod: 2026-06-08
Catalog position: Engineering · languages
Indexed related skills: 10

How Typescript Narrowing Expert fits the catalog

Typescript Narrowing Expert sits in the Engineering category under the languages sub-topic in the ClaudSkills catalog. There are 10 related skills indexed alongside it; comparing a few before installing usually reveals which fits your workflow best.

These notes are auto-generated from features detected in the SKILL.md file and from this catalog's structure — they aren't part of the source repository.

From the source SKILL.md

The interesting part of TypeScript isn't generics — it's narrowing. Control-flow analysis turns wide types into specific ones inside conditional branches. Most "TypeScript is fighting me" stories come from narrowing not propagating where the engineer expected.

What this skill does

Typescript Narrowing Expert is a community-contributed Claude Code skill in the languages sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/typescript-narrowing-expert/ and loads when your prompt matches the skill's trigger.

When to invoke it: Use when designing discriminated unions, debugging control-flow analysis, choosing satisfies vs as, building branded types, writing user-defined type guards, or composing conditional types and template literal types. Triggers: "Type X is not assignable to type Y" after a type guard, exhaustiveness checks via never, satisfies vs explicit annotation, infer in conditional types, mapped types with key remapping, distributive conditional types, type-narrowing inside callbacks losing the narrowed type.

Who uses this skill

The Typescript Narrowing Expert Claude Code skill is built for software engineers, backend developers, full-stack teams, and technical leads building and maintaining production systems. It's part of ClaudSkills (also referred to as Claude Skills or Claude Code Skills) — the open community-curated registry of 94,000+ SKILL.md files for Anthropic's Claude Code agent and the wider Claude ecosystem (Claude API, Claude Agent SDK).

How to install

Free

Manual install (2 steps)

mkdir -p ~/.claude/skills/typescript-narrowing-expert
curl -L https://claudskills.com/skills/typescript-narrowing-expert/SKILL.md \
  -o ~/.claude/skills/typescript-narrowing-expert/SKILL.md

Or just download SKILL.md directly and drop it into ~/.claude/skills/typescript-narrowing-expert/. Claude Code auto-discovers it on next session.

Skills live at ~/.claude/skills/typescript-narrowing-expert/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\typescript-narrowing-expert\SKILL.md on Windows. See the full install guide for step-by-step instructions.

📱 Install from your phone or desktop Telegram

Open @claudskills_bot on Telegram, tap Open Desktop App, and the desktop app installs this skill for you. Or share the bot link with a colleague — they get the same one-tap install. Learn more →

Pro

One-click install via the desktop app

The ClaudSkills desktop app installs any skill directly into ~/.claude/skills/ with one click — no terminal required. Pro starts at $9/mo or $149 lifetime.

Pro

For the full experience including quality scoring and one-click install features for each skill — upgrade to Pro.

See pricing → Download desktop app

Frequently asked questions

How do I install the Typescript Narrowing Expert Claude Code skill?

Install via the ClaudSkills desktop app (one click) or copy SKILL.md from the source repository to ~/.claude/skills/typescript-narrowing-expert/SKILL.md and restart Claude Code. Both flows are detailed at claudskills.com/install/.

What does the Typescript Narrowing Expert skill do?

Is this skill free to install?

Yes. ClaudSkills is an open registry — every skill keeps its source repository's license, and manual install via copy is free. ClaudSkills Pro ($9/mo, $79/yr, or $149 one-time) adds one-click install via the desktop app and a multi-signal Quality Score.

When should I use the Typescript Narrowing Expert skill?

Use Typescript Narrowing Expert when your Claude Code task falls under the Engineering category — specifically in the languages area. Claude Code auto-discovers installed skills and invokes the right one based on the task description, so you can also ask Claude directly (e.g. "use Typescript Narrowing Expert" or describe the task and let Claude pick). Browse related skills at /category/engineering/.

What is a Claude Code skill and how does the Typescript Narrowing Expert skill fit in?

A Claude Code skill is a SKILL.md file that lives under ~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Typescript Narrowing Expert is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the Engineering category. Learn more at /learn/what-is-a-claude-skill/.

Attribution & license

Source: https://github.com/curiositech/windags-skills/blob/HEAD/skills/typescript-narrowing-expert/SKILL.md
Author: curiositech

Cite this skill

If you reference this skill in a blog post, paper, or documentation, you can cite it as:

APA

curiositech. (2026). Typescript Narrowing Expert [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/typescript-narrowing-expert/

BibTeX

@misc{typescript-narrowing-expert-2026,
  author    = {curiositech},
  title     = {Typescript Narrowing Expert [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/typescript-narrowing-expert/}
}

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