diff --git a/Packages/CmuxMobileShell/Sources/CmuxMobileShell/MobileShellComposite.swift b/Packages/CmuxMobileShell/Sources/CmuxMobileShell/MobileShellComposite.swift
index 1333cfafe42..c7440d2dde1 100644
--- a/Packages/CmuxMobileShell/Sources/CmuxMobileShell/MobileShellComposite.swift
+++ b/Packages/CmuxMobileShell/Sources/CmuxMobileShell/MobileShellComposite.swift
@@ -344,7 +344,9 @@ public final class MobileShellComposite: MobileTerminalOutputSinking {
     /// Per-image encoded-bytes cap. An add whose single image exceeds this is
     /// rejected outright (the view bounds the encode below this, but the store
     /// re-enforces it as the single source of truth).
-    public static let maxPendingAttachmentImageBytes = 8 * 1024 * 1024
+    // nonisolated so the composer's off-main (nonisolated) image-encode path can
+    // read the authoritative per-image cap; it is an immutable Sendable literal.
+    public nonisolated static let maxPendingAttachmentImageBytes = 8 * 1024 * 1024
     /// GLOBAL encoded-bytes budget summed across EVERY terminal's staged set, not
     /// just the target's. The per-terminal cap bounds one draft, but each live
     /// terminal carries its own per-terminal budget, so staging photos across many
diff --git a/Packages/CmuxMobileShellUI/Sources/CmuxMobileShellUI/TerminalComposerView.swift b/Packages/CmuxMobileShellUI/Sources/CmuxMobileShellUI/TerminalComposerView.swift
index 2ee76e0e77a..299fbdad58c 100644
--- a/Packages/CmuxMobileShellUI/Sources/CmuxMobileShellUI/TerminalComposerView.swift
+++ b/Packages/CmuxMobileShellUI/Sources/CmuxMobileShellUI/TerminalComposerView.swift
@@ -114,7 +114,7 @@ struct TerminalComposerView: View {
     /// clipboard paste path and keep the bounded encode under ~8 MB. The store
     /// re-enforces this as the authoritative per-image cap; this constant only
     /// bounds the encode loop below it.
-    private static let maxImageBytes = CMUXMobileShellStore.maxPendingAttachmentImageBytes
+    private nonisolated static let maxImageBytes = CMUXMobileShellStore.maxPendingAttachmentImageBytes
 
     /// Cap how many images one message may carry, mirrored from the store so the
     /// picker's `maxSelectionCount` matches the store's authoritative count cap.
@@ -137,14 +137,14 @@ struct TerminalComposerView: View {
 
     /// Max pixel dimension of the cached chip thumbnail. The chip renders at 56pt;
     /// 3x covers Retina without holding the full-resolution image.
-    private static let thumbnailMaxPixelSize = 168
+    private nonisolated static let thumbnailMaxPixelSize = 168
 
     /// Max pixel dimension of the SEND payload. ImageIO downsamples the picked
     /// item to fit this longest edge before re-encoding, so a panorama or a
     /// 48-megapixel HEIC never materializes as a full-resolution raster. 2048 px
     /// keeps screenshot text legible for an agent while bounding the bytes well
     /// under the per-image cap.
-    private static let sendMaxPixelSize = 2048
+    private nonisolated static let sendMaxPixelSize = 2048
 
     var body: some View {
         composerSurface
@@ -542,7 +542,7 @@ struct TerminalComposerView: View {
     /// 3. Progressively smaller dimensions as a last resort.
     /// Returns the encoded bytes + a lowercase format hint, or `nil` if the source
     /// is undecodable. The cap is also re-enforced authoritatively in the store.
-    private static func boundedSendPayload(from source: CGImageSource) -> (data: Data, format: String)? {
+    private nonisolated static func boundedSendPayload(from source: CGImageSource) -> (data: Data, format: String)? {
         // PNG at the bounded send size: lossless, and for a typical screenshot it
         // lands well under the cap.
         if let png = downsampledImageData(
@@ -599,7 +599,7 @@ struct TerminalComposerView: View {
     ///   - maxPixelSize: The longest-edge cap, in pixels, for the downsample.
     ///   - type: The destination UTType identifier (`"public.png"`/`"public.jpeg"`).
     ///   - jpegQuality: The JPEG compression quality (0...1); `nil` for PNG.
-    private static func downsampledImageData(
+    private nonisolated static func downsampledImageData(
         from source: CGImageSource,
         maxPixelSize: Int,
         type: String,