Let Compact continue on another model or vendor

mac/Sources/Byre/Chat.swift

@@ -470,17 +470,10 @@ struct CompactButton: View {
         let level = pct >= 90 ? Palette.danger : pct >= 70 ? Palette.warn : Palette.accent
         let detail = usage.map { u in u.window > 0 ? "\ncontext: \(u.used.formatted()) of \(u.window.formatted()) tokens\(u.model.isEmpty ? "" : " (\(u.model))")" : "" } ?? ""
         let disabled = sessionId == nil || state != .idle || sending
-        Button {
-            guard let sessionId else {
-                return
-            }
-            sending = true
-            Task {
-                do {
-                    _ = try await store.api.client.compactSession(path: .init(sessionId: sessionId)).accepted
-                } catch {
-                    overlays.showAlert(errorText(error))
-                    sending = false
+        Menu {
+            ForEach(models, id: \.self) { m in
+                Button("Continue on \(m)") {
+                    compact(m)
                 }
             }
         } label: {
@@ -504,14 +497,34 @@ struct CompactButton: View {
                 .overlay(RoundedRectangle(cornerRadius: 6).stroke(pct >= 70 ? level : Palette.border))
                 .opacity(disabled ? 0.45 : 1)
                 .contentShape(Rectangle())
+        } primaryAction: {
+            compact(nil)
         }
+        .menuStyle(.button)
+        .menuIndicator(.hidden)
         .buttonStyle(.plain)
+        .fixedSize()
         .disabled(disabled)
-        .help("Ask the agent for a handoff, then continue in a new session with a fresh context\(detail)")
+        .help("Ask the agent for a handoff, then continue in a new session with a fresh context; hold to continue on another model\(detail)")
         .onChange(of: state) {
             sending = false
         }
     }
+
+    private func compact(_ model: String?) {
+        guard let sessionId else {
+            return
+        }
+        sending = true
+        Task {
+            do {
+                _ = try await store.api.client.compactSession(path: .init(sessionId: sessionId), body: .json(.init(model: model))).accepted
+            } catch {
+                overlays.showAlert(errorText(error))
+                sending = false
+            }
+        }
+    }
 }
 
 private struct ScrollMetrics: Equatable {