diff --git a/TODO.md b/TODO.md
index 2bd65e6..87a1c3d 100644
--- a/TODO.md
+++ b/TODO.md
@@ -16,8 +16,6 @@
 
 # M8 — macOS client
 
-- macOS client strict memory safety
-  Turn on `.strictMemorySafety()` for the `Byre` target in `mac/Package.swift` and resolve what it flags (`@unchecked Sendable` on `Re`, `MainActor.assumeIsolated` in the key and click monitors, and anything else), so `swift build` is warning-free with it on.
 - macOS client signing and SwiftData with iCloud sync
   Sign `byre.app` with the paid developer team (provisioning profile, iCloud and CloudKit entitlements) in `mac/bundle.sh`, and move the app's persisted state (the `byre.server` origin, drafts, last visits) from `UserDefaults` to SwiftData with CloudKit sync, so the server address follows the user to every Mac.
 - macOS client parity review
diff --git a/mac/Package.swift b/mac/Package.swift
index 86a30d7..6867bf9 100644
--- a/mac/Package.swift
+++ b/mac/Package.swift
@@ -25,7 +25,8 @@ let package = Package(
                 .product(name: "SwiftTerm", package: "SwiftTerm"),
                 .product(name: "OpenAPIRuntime", package: "swift-openapi-runtime"),
                 .product(name: "OpenAPIURLSession", package: "swift-openapi-urlsession"),
-            ]
+            ],
+            swiftSettings: [.strictMemorySafety()]
         ),
     ]
 )
diff --git a/mac/Sources/Byre/Diagram.swift b/mac/Sources/Byre/Diagram.swift
index 92d1a03..a045900 100644
--- a/mac/Sources/Byre/Diagram.swift
+++ b/mac/Sources/Byre/Diagram.swift
@@ -277,8 +277,13 @@ struct DiagramLayout {
     let size: CGSize
 }
 
-nonisolated(unsafe) private let labelFont = Fonts.ct(13)
-nonisolated(unsafe) private let edgeFont = Fonts.ct(12)
+private var labelFont: CTFont {
+    Fonts.ns(13) as CTFont
+}
+
+private var edgeFont: CTFont {
+    Fonts.ns(12) as CTFont
+}
 
 func textSize(_ text: String, _ font: CTFont) -> CGSize {
     let lines = text.components(separatedBy: "\n")
diff --git a/mac/Sources/Byre/Files.swift b/mac/Sources/Byre/Files.swift
index bcca51e..6adb69c 100644
--- a/mac/Sources/Byre/Files.swift
+++ b/mac/Sources/Byre/Files.swift
@@ -26,9 +26,9 @@ private func bytes(_ n: Int64) -> String {
         return "\(n) B"
     }
     if n < 1024 * 1024 {
-        return String(format: "%.1f KiB", Double(n) / 1024)
+        return "\((Double(n) / 1024).formatted(.number.precision(.fractionLength(1)).grouping(.never))) KiB"
     }
-    return String(format: "%.1f MiB", Double(n) / 1024 / 1024)
+    return "\((Double(n) / 1024 / 1024).formatted(.number.precision(.fractionLength(1)).grouping(.never))) MiB"
 }
 
 private func shown(_ c: FileContent) -> Int64 {
diff --git a/mac/Sources/Byre/Fonts.swift b/mac/Sources/Byre/Fonts.swift
index 44be0b2..0eb263d 100644
--- a/mac/Sources/Byre/Fonts.swift
+++ b/mac/Sources/Byre/Fonts.swift
@@ -1,4 +1,5 @@
 import CoreText
+import Synchronization
 import SwiftUI
 
 enum Fonts {
@@ -14,7 +15,7 @@ enum Fonts {
     }()
 
     private static func file(_ subset: String, _ italic: Bool, _ weight: CGFloat) -> CTFontDescriptor {
-        let d = descriptors["atkinson-hyperlegible-mono-\(subset)-wght-\(italic ? "italic" : "normal").woff2"]!
+        let d = unsafe descriptors["atkinson-hyperlegible-mono-\(subset)-wght-\(italic ? "italic" : "normal").woff2"]!
         return CTFontDescriptorCreateCopyWithVariation(d, 0x7767_6874 as CFNumber, weight)
     }
 
@@ -24,29 +25,25 @@ enum Fonts {
         return CTFontCreateWithFontDescriptor(d, size, nil)
     }
 
-    nonisolated(unsafe) private static var fonts: [String: (font: Font, ns: NSFont)] = [:]
-    private static let lock = NSLock()
+    private static let fonts = Mutex<[String: CTFont]>([:])
 
-    private static func cached(_ size: CGFloat, _ weight: CGFloat, _ italic: Bool) -> (font: Font, ns: NSFont) {
+    private static func cached(_ size: CGFloat, _ weight: CGFloat, _ italic: Bool) -> CTFont {
         let key = "\(size) \(weight) \(italic)"
-        lock.lock()
-        defer {
-            lock.unlock()
-        }
-        if let f = fonts[key] {
+        return fonts.withLock { fonts in
+            if let f = fonts[key] {
+                return f
+            }
+            let f = ct(size, weight: weight, italic: italic)
+            fonts[key] = f
             return f
         }
-        let c = ct(size, weight: weight, italic: italic)
-        let f = (Font(c), c as NSFont)
-        fonts[key] = f
-        return f
     }
 
     static func font(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> Font {
-        cached(size, weight, italic).font
+        Font(cached(size, weight, italic))
     }
 
     static func ns(_ size: CGFloat, weight: CGFloat = 400, italic: Bool = false) -> NSFont {
-        cached(size, weight, italic).ns
+        cached(size, weight, italic) as NSFont
     }
 }
diff --git a/mac/Sources/Byre/MarkdownView.swift b/mac/Sources/Byre/MarkdownView.swift
index 9d8f7f2..abf7928 100644
--- a/mac/Sources/Byre/MarkdownView.swift
+++ b/mac/Sources/Byre/MarkdownView.swift
@@ -112,7 +112,7 @@ struct InlineRenderer {
     private func run(_ s: String, _ style: Style) -> AttributedString {
         var a = AttributedString(s)
         a.font = Fonts.font(style.small ? 11 : size, weight: style.bold ? 700 : 400, italic: style.italic)
-        a.appKit.font = Fonts.ns(style.small ? 11 : size, weight: style.bold ? 700 : 400, italic: style.italic)
+        a.mergeAttributes(try! AttributeContainer([.font: Fonts.ns(style.small ? 11 : size, weight: style.bold ? 700 : 400, italic: style.italic)], including: \.appKit))
         if let link = style.link {
             a.link = link
         }
@@ -364,7 +364,7 @@ private struct FlowBuilder {
         s.append(NSAttributedString(string: "\n", attributes: [.font: Fonts.ns(ctx.size)]))
         let all = NSRange(location: 0, length: s.length)
         let color = NSColor(ctx.color)
-        s.enumerateAttribute(.foregroundColor, in: all) { value, range, _ in
+        unsafe s.enumerateAttribute(.foregroundColor, in: all) { value, range, _ in
             if value == nil {
                 s.addAttribute(.foregroundColor, value: color, range: range)
             }
@@ -405,8 +405,8 @@ private struct FlowText: NSViewRepresentable {
         v.isVerticallyResizable = false
         v.isHorizontallyResizable = false
         v.textContainerInset = .zero
-        v.textContainer!.lineFragmentPadding = 0
-        v.textContainer!.widthTracksTextView = true
+        unsafe v.textContainer!.lineFragmentPadding = 0
+        unsafe v.textContainer!.widthTracksTextView = true
         v.linkTextAttributes = [.cursor: NSCursor.pointingHand]
         v.delegate = context.coordinator
         return v
@@ -414,11 +414,11 @@ private struct FlowText: NSViewRepresentable {
 
     func updateNSView(_ v: FlowTextView, context: Context) {
         context.coordinator.openURL = context.environment.openURL
-        if v.textStorage!.isEqual(to: text) {
+        if unsafe v.textStorage!.isEqual(to: text) {
             return
         }
         let selected = v.selectedRanges
-        v.textStorage!.setAttributedString(text)
+        unsafe v.textStorage!.setAttributedString(text)
         if selected.allSatisfy({ NSMaxRange($0.rangeValue) <= text.length }) {
             v.selectedRanges = selected
         }
diff --git a/mac/Sources/Byre/PaneFocus.swift b/mac/Sources/Byre/PaneFocus.swift
index e3639af..7bd5b36 100644
--- a/mac/Sources/Byre/PaneFocus.swift
+++ b/mac/Sources/Byre/PaneFocus.swift
@@ -166,7 +166,7 @@ struct WindowReader: NSViewRepresentable {
     func makeNSView(context: Context) -> NSView {
         let view = NSView()
         DispatchQueue.main.async {
-            if let w = view.window {
+            if let w = unsafe view.window {
                 found(w)
             }
         }
@@ -175,7 +175,7 @@ struct WindowReader: NSViewRepresentable {
 
     func updateNSView(_ nsView: NSView, context: Context) {
         DispatchQueue.main.async {
-            if let w = nsView.window {
+            if let w = unsafe nsView.window {
                 found(w)
             }
         }
diff --git a/mac/Sources/Byre/Status.swift b/mac/Sources/Byre/Status.swift
index 3ce9361..be04d90 100644
--- a/mac/Sources/Byre/Status.swift
+++ b/mac/Sources/Byre/Status.swift
@@ -30,7 +30,7 @@ private func bytes(_ n: Int64) -> String {
         v /= 1024
         i += 1
     }
-    return String(format: i == 0 ? "%.0f %@" : "%.1f %@", v, units[i])
+    return "\(v.formatted(.number.precision(.fractionLength(i == 0 ? 0 : 1)).grouping(.never))) \(units[i])"
 }
 
 private func resetText(_ unixSeconds: Double) -> String {
diff --git a/mac/Sources/Byre/Terminal.swift b/mac/Sources/Byre/Terminal.swift
index d020e71..541af29 100644
--- a/mac/Sources/Byre/Terminal.swift
+++ b/mac/Sources/Byre/Terminal.swift
@@ -82,7 +82,7 @@ struct TerminalHost: NSViewRepresentable {
         context.coordinator.view = t
         DispatchQueue.main.async {
             colour(t)
-            t.window?.makeFirstResponder(t)
+            unsafe t.window?.makeFirstResponder(t)
             context.coordinator.connect()
         }
         return t