AppBootstrapAI: Skill for Claude Code

.claude/skills/swift-error-handling-pro/SKILL.md

swift-error-handling-pro is a skill for Claude Code from kelvinkosbab/AppBootstrapAI. It costs 44 tokens per session (780 once invoked), scanned A, original, MIT.

A review aid for Swift errors and functions that can fail. It checks error types, typed throws, Result values, asynchronous error flow, and silently ignored failures.

In plain words
What is it for?
Use it when writing or reviewing Swift error types, throwing functions, asynchronous code, and choices between Result and throws.
Why use it?
It helps make failures understandable to both code and users while avoiding swallowed errors and outdated patterns.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

This is kelvinkosbab/AppBootstrapAI's own configuration. It tells Claude Code how to work on AppBootstrapAI itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything AppBootstrapAI configures →

Reuse

Borrowing it

Nothing to install: this file belongs to kelvinkosbab/AppBootstrapAI. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/kelvinkosbab/AppBootstrapAI/main/.claude/skills/swift-error-handling-pro/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/kelvinkosbab/AppBootstrapAI

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 swift-error-handling-pro

README.md
[![agentmods](https://agentmods.dev/badge/skills/kelvinkosbab/appbootstrapai/swift-error-handling-pro/github.svg)](https://agentmods.dev/skills/kelvinkosbab/appbootstrapai/swift-error-handling-pro)
Your own site
<a href="https://agentmods.dev/skills/kelvinkosbab/appbootstrapai/swift-error-handling-pro"><img src="https://agentmods.dev/badge/skills/kelvinkosbab/appbootstrapai/swift-error-handling-pro/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 swift-error-handling-pro

Your own site · 80×15
<a href="https://agentmods.dev/skills/kelvinkosbab/appbootstrapai/swift-error-handling-pro"><img src="https://agentmods.dev/badge/skills/kelvinkosbab/appbootstrapai/swift-error-handling-pro.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 780 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 $0.00044 $0.00780
Opus 5 $0.00022 $0.00390
Sonnet 5 $0.00009 $0.00156
Haiku 4.5 $0.00004 $0.00078

Measured 10d ago against content hash 3bef2111db81, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

swift-error-handling-pro 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 10d 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.

.claude/skills/swift-error-handling-pro/SKILL.md · 95 lines

How it starts

The opening of the file, as written. The whole thing — 95 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Review Swift error handling for correctness, modern API usage, and clear error semantics. Report only genuine problems - do not nitpick or invent issues.

Review process:

  1. Check error type definitions for LocalizedError, Equatable, and Sendable conformance using references/error-types.md.
  2. Evaluate whether typed throws (Swift 6.0+) would clarify the API using references/typed-throws.md.
  3. Validate Result vs throws choice for the API style using references/result-vs-throws.md.
  4. Check async error propagation patterns using references/async-errors.md.
  5. Flag swallowed errors (catch blocks that ignore errors silently).

If doing a partial review, load only the relevant reference files.

Core Instructions

  • Target Swift 6.0 or later — typed throws is available and should be considered for library code.
  • Prefer throws over Result in modern async code — async throws reads more naturally than returning a Result.
  • Error types should conform to Sendable so they can cross isolation boundaries safely.
  • Public error types should conform to LocalizedError and provide errorDescription for user-facing strings.
  • Never use try! or try? to silence errors that could meaningfully be handled or surfaced.
  • Avoid catch { } blocks that swallow the error — at minimum, log it.
  • Don't wrap errors in nested types unnecessarily — flatten error hierarchies where possible.

Output Format

Organize findings by file. For each issue:

  1. State the file and relevant line(s).
  2. Name the rule being violated.
  3. Show a brief before/after code fix.

Skip files with no issues. End with a prioritized summary of the most impactful changes to make first.

Example output:

Sources/Storage/FileStoreError.swift

Line 12: Public error type should conform to LocalizedError for user-facing strings.

// Before
public enum FileStoreError: Error {
    case readFailed
    case writeFailed
}

// After
public enum FileStoreError: LocalizedError {
    case readFailed
    case writeFailed

    public var errorDescription: String? {
        switch self {
        case .readFailed: "Failed to read from disk."
        case .writeFailed: "Failed to write to disk."
        }
    }
}

Read the full file on GitHub · 95 lines

Files

What ships with it

4 files 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. 10d ago First seen · 95 lines · 44 tokens per session scan A 3bef2111db81

Subscribe to this mod's changes

swift-error-handling-pro is a skill published in the GitHub repository kelvinkosbab/AppBootstrapAI (5 stars, last pushed 19d ago), licensed MIT. It adds 44 tokens to every session and 780 once invoked, about $0.0002 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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