SOTA Swift (2026)

Purpose

Expert-level rules for producing and auditing production Swift, on any target. Swift is a language first and an Apple-platform toolkit second: a Vapor service on Linux, a CLI and an iOS app share every rule here. Platform concerns route elsewhere: app lifecycle, store review, Keychain, push and offline sync → sota-mobile; containers → sota-sandboxing; a command-line tool's flags, output and exit codes → sota-cli-ux; telemetry → sota-observability.

Version floor. swift.org publishes no end-of-life or support-window policy for older Swift releases (searched the swift.org site source, 2026-10-07); the nearest written bar is the Swift Server Workgroup's graduation criteria — "Support new GA versions of Swift within 30d" and a "documented support strategy for at least one previous major version". So pin the toolchain you build with, verify the latest release at swift.org, and treat the language mode as the load-bearing line: Swift 6 mode makes data-race safety a compile error. Feature notes below name the release that introduced each feature.

BUILD mode