Async Programming

This walks you through writing concurrent Python and Rust code that won't bite you with race conditions or resource leaks. It's structured around TDD with pytest-asyncio, starting each feature with a test that catches the concurrent bug before you write the implementation. The patterns section covers the usual suspects: asyncio.gather for parallelism, semaphores for rate limiting, proper lock usage around shared state, and keeping blocking calls off the event loop. The decision framework is helpful for quickly choosing between locks, queues, or atomic operations. It's marked medium risk because async bugs like TOCTOU or double-spending are subtle and security-sensitive, even if they're not direct attack vectors. Good reference if you keep forgetting the right way to handle cancellation or deadlock prevention.

skills.sh installs: 258
GitHub stars: 48
last updated: Aug 21, 2026

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Install

$ npx -y skills add martinholovsky/claude-skills-generator --skill async-programming --agent claude-code

Installs into .claude/skills of the current project.

Files

Async Programming Skill

File Organization

SKILL.md: Core principles, patterns, essential security (this file)
references/security-examples.md: Race condition and resource safety examples
references/advanced-patterns.md: Advanced async patterns and optimization

Validation Gates

Gate 0.1: Domain Expertise Validation

Status: PASSED
Expertise Areas: asyncio, Tokio, race conditions, resource management, concurrent safety

Gate 0.2: Vulnerability Research

Status: PASSED (3+ issues for MEDIUM-RISK)
Research Date: 2025-11-20
Issues: CVE-2024-12254 (asyncio memory), Redis race condition (CVE-2023-28858/9)

Gate 0.11: File Organization Decision

Decision: Split structure (MEDIUM-RISK, ~400 lines main + references)

1. Overview

Risk Level: MEDIUM

Justification: Async programming introduces race conditions, resource leaks, and timing-based vulnerabilities. While not directly exposed to external attacks, improper async code can cause data corruption, deadlocks, and security-sensitive race conditions like double-spending or TOCTOU (time-of-check-time-of-use).

SKILL.md on GitHub