---
title: "Swift 6.4: What’s New in Concurrency"
url: https://daily.dev/posts/swift-6-4-what-s-new-in-concurrency-5j79mqpon
source_url: https://www.avanderlee.com/concurrency/swift-6-4-whats-new-in-concurrency
type: article
source: "SwiftLee"
published: 2026-06-21T07:07:35.202Z
updated: 2026-06-21T14:37:28.902Z
tags: ["swift"]
reading_time: 10
upvotes: 0
comments: 0
language: en
---

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# Swift 6.4: What’s New in Concurrency

**[SwiftLee](https://daily.dev/sources/avanderlee)** · 10 min read · 0 upvotes · 0 comments

## Summary

Swift 6.4, released at WWDC 2026, brings several concurrency improvements. Key changes include: async defer bodies (SE-0493) allowing await inside defer for cleaner cleanup; task cancellation shields (SE-0504) via withTaskCancellationShield to protect cleanup code from observing cancellation; compiler warnings for ignored throwing tasks (SE-0520) to prevent silently swallowed errors; typed throwing task initializers for more specific failure types; an async Result initializer (SE-0530) to reduce boilerplate; weak let references from Swift 6.3 (SE-0481) for Sendable-safe delegate patterns; and ~Sendable (SE-0518) to explicitly mark types as intentionally non-Sendable.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://www.avanderlee.com/concurrency/swift-6-4-whats-new-in-concurrency>

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