Swift Concurrency Agent Skill is a portable set of guidance for AI coding tools working with Swift's concurrency features. Developers use it to migrate to Swift 6, diagnose data races and isolation errors, write safer asynchronous code, and improve concurrency performance. The catalogue entries package the project's plugin, skill, and instructions for supported agents.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add AvdLee/Swift-Concurrency-Agent-Skill --skill swift-concurrencygit clone --depth 1 https://github.com/AvdLee/Swift-Concurrency-Agent-SkillWrote 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.
[](https://agentmods.dev/skills/avdlee/swift-concurrency-agent-skill/swift-concurrency)<a href="https://agentmods.dev/skills/avdlee/swift-concurrency-agent-skill/swift-concurrency"><img src="https://agentmods.dev/badge/skills/avdlee/swift-concurrency-agent-skill/swift-concurrency/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.
<a href="https://agentmods.dev/skills/avdlee/swift-concurrency-agent-skill/swift-concurrency"><img src="https://agentmods.dev/badge/skills/avdlee/swift-concurrency-agent-skill/swift-concurrency.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00056 | $0.02916 |
| Opus 5 | $0.00028 | $0.01458 |
| Sonnet 5 | $0.00011 | $0.00583 |
| Haiku 4.5 | $0.00006 | $0.00292 |
Grade A, and why
swift-concurrency 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 11d 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.
Copies of this mod
2 near-identical copies found in the catalogue:
- swift-concurrency — 86% identical, 49 lines differ
- swift-concurrency — 80% identical, 54 lines differ
How it starts
The opening of the file, as written. The whole thing — 212 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Swift Concurrency
Fast Path
Before proposing a fix:
- Analyze
Package.swiftor.pbxprojto determine Swift language mode, strict concurrency level, default isolation, and upcoming features. Do this always, not only for migration work. - Capture the exact diagnostic and offending symbol.
- Determine the isolation boundary:
@MainActor, custom actor, actor instance isolation, ornonisolated. - Confirm whether the code is UI-bound or intended to run off the main actor. When spawning unstructured tasks, inspect the synchronous prefix (everything before the first
await): start on@MainActoronly when that prefix truly needs main-actor access; otherwise useTask { @concurrent in ... }and hop back withMainActor.runonly after the suspension. A trivial non-main line (for example,print) followed by main-actor work in the same prefix is not a reason to use@concurrent. For delayed retries, timers, and backoff tasks, separate the waiting from the UI mutation. The sleep often belongs off the main actor even when the final state update belongs on it.
Project settings that change concurrency behavior:
| Setting | SwiftPM (Package.swift) |
Xcode (.pbxproj) |
|---|---|---|
| Language mode | swiftLanguageVersions or -swift-version (// swift-tools-version: is not a reliable proxy) |
Swift Language Version |
| Strict concurrency | .enableExperimentalFeature("StrictConcurrency=targeted") |
SWIFT_STRICT_CONCURRENCY |
| Default isolation | .defaultIsolation(MainActor.self) |
SWIFT_DEFAULT_ACTOR_ISOLATION |
| Upcoming features | .enableUpcomingFeature("NonisolatedNonsendingByDefault") |
SWIFT_UPCOMING_FEATURE_* |
| Approachable Concurrency | N/A (use individual upcoming features) | SWIFT_APPROACHABLE_CONCURRENCY |
Xcode 26 note: New projects created in Xcode 26 will often start with
SWIFT_DEFAULT_ACTOR_ISOLATION = MainActorandSWIFT_APPROACHABLE_CONCURRENCY = YESenabled by default. Treat these as likely defaults for newly created projects, not as confirmed settings.
What ships with it
19 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.
- agents/openai.yaml 249 B
- assets/logo-small.png 4.2 KB
- assets/logo.png 25 KB
- references/_index.md 2.1 KB
- references/actors.md 17 KB
- references/async-algorithms.md 20 KB
- references/async-await-basics.md 7.5 KB
- references/async-sequences.md 17 KB
- references/core-data.md 15 KB
- references/glossary.md 6.9 KB
- references/linting.md 5.2 KB
- references/memory-management.md 12 KB
- references/migration.md 33 KB
- references/observation.md 14 KB
- references/performance.md 15 KB
- references/sendable.md 13 KB
- references/tasks.md 17 KB
- references/testing.md 13 KB
- references/threading.md 16 KB
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.
- 11d ago First seen · 212 lines · 56 tokens per session scan A 8c667b2ff988
swift-concurrency is a skill published in the GitHub repository AvdLee/Swift-Concurrency-Agent-Skill (1,646 stars, last pushed 29d ago), licensed MIT. It adds 56 tokens to every session and 2,916 once invoked, about $0.0003 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 2026-08-30.
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