nvrsion: Add: Fix auto-scroll instability in iOS session chat so the transcript no longer jitters on scroll, and begin MACOS_VM_NATIVE_AGENT_Markdown in ./docs/MACOS_VM_NATIVE_AGENT.md.

Nucleic-Promote: 1
Co-authored-by: Nucleic <[email protected]>

NucleicRemote/NucleicRemote/Views/SessionDetailView.swift

@@ -18,13 +18,18 @@ struct SessionDetailView: View {
     // Bumped on send to jump the transcript to the bottom, even if the user had scrolled up to
     // read history — sending is a deliberate "show me what happens next" (mirrors the Mac).
     @State private var scrollToBottomRequest = 0
+    // Owned here (not inside `TranscriptList`) so the jump-to-bottom chevron can ride in the chat
+    // bar just above the composer. `TranscriptList` drives it from the scroll geometry.
+    @State private var isScrolledToBottom = true
 
     private var summary: WireSessionSummary? {
         store.sessions.first { $0.sessionID == sessionID }
     }
 
     var body: some View {
-        TranscriptList(events: store.openEvents, scrollToBottomRequest: scrollToBottomRequest)
+        TranscriptList(events: store.openEvents,
+                       scrollToBottomRequest: scrollToBottomRequest,
+                       isScrolledToBottom: $isScrolledToBottom)
             // The chat bar floats over the scrolling content on Liquid Glass instead of sitting
             // in a boxed strip below it, so the transcript runs the full height of the screen.
             .safeAreaInset(edge: .bottom) { actionArea }
@@ -236,6 +241,15 @@ struct SessionDetailView: View {
     /// pending. Content scrolls beneath it; nothing renders when there's nothing to act on.
     private var actionArea: some View {
         VStack(spacing: 8) {
+            // The jump-to-bottom chevron rides here, immediately above the chat bar — not as a
+            // transcript overlay, which aligned to the scroll view's full-height bounds and so sat
+            // behind this floating bar at the screen's bottom edge. Shown only while scrolled up; a
+            // tap bumps the same scroll request the send button uses, so following resumes once the
+            // transcript reaches the bottom. Mirrors the Mac's `JumpToBottomButton`.
+            if !isScrolledToBottom {
+                JumpToBottomButton { scrollToBottomRequest += 1 }
+                    .transition(.move(edge: .bottom).combined(with: .opacity))
+            }
             // Interacting with a chat while the owning Mac is unreachable surfaces this first, so a
             // disabled composer reads as "offline / read-only history" rather than broken.
             if !store.connectivity.isLive { disconnectedBanner }
@@ -243,6 +257,7 @@ struct SessionDetailView: View {
         }
         .padding(.horizontal, 12)
         .padding(.bottom, 8)
+        .animation(.easeInOut(duration: 0.15), value: isScrolledToBottom)
     }
 
     /// The offline notice over the transcript: the chat's history is cached and readable, but the
@@ -401,8 +416,9 @@ struct TranscriptList: View {
 
     /// True while the user is parked at (within a hair of) the bottom, so live output keeps
     /// following; once they scroll up it flips false, following stops, and the jump-to-bottom
-    /// chevron appears. Starts true — a freshly opened chat is anchored at the bottom.
-    @State private var isScrolledToBottom = true
+    /// chevron appears. Starts true — a freshly opened chat is anchored at the bottom. Owned by
+    /// the parent so the chevron can live in the chat bar above the composer.
+    @Binding var isScrolledToBottom: Bool
 
     /// True for a short window right after the transcript appears, while it runs its first
     /// layout passes and its events fill in. During it we accept only "at bottom" scroll
@@ -426,10 +442,22 @@ struct TranscriptList: View {
     var body: some View {
         ScrollViewReader { proxy in
             ScrollView {
-                LazyVStack(alignment: .leading, spacing: 14) {
+                // Eager VStack (not Lazy): the whole transcript is in memory, and eager layout
+                // hands the ScrollView its true, *fixed* total content height up front. A
+                // LazyVStack instead realizes rows as they scroll into view, so its reported
+                // content height shifts mid-scroll as rows resolve — and that shifting height fed
+                // straight back through the geometry reader below (flip at-bottom → toggle the
+                // `.defaultScrollAnchor` → re-pin → new height → …), which is what made the whole
+                // transcript jitter up and down under a drag. A stable height breaks the loop.
+                // Matches the Mac transcript, for the same reason.
+                VStack(alignment: .leading, spacing: 14) {
                     ForEach(items) { item in
                         TranscriptRow(item: item).id(item.id)
                     }
+                    // Fixed, zero-content scroll target for "jump to bottom". Scrolling to the last
+                    // row's id instead would chase a moving target — the final row's identity
+                    // changes as its streaming deltas coalesce — nudging the viewport mid-stream.
+                    Color.clear.frame(height: 1).id(Self.bottomAnchorID)
                 }
                 .padding()
                 // Cap the transcript to a readable measure on a wide iPad so lines don't run
@@ -483,35 +511,27 @@ struct TranscriptList: View {
             // so every streamed delta keeps the view pinned to the bottom — but only while the
             // user is already parked there. Scrolling up to read history is never yanked down.
             .onChange(of: events.count) {
-                if isScrolledToBottom { scrollToLast(proxy, animated: !transcriptSettling) }
-            }
-            // An explicit jump — the chevron or sending a message — always wins.
-            .onChange(of: scrollToBottomRequest) { scrollToLast(proxy) }
-            // Floating chevron above the chat bar, shown only while scrolled up; tap to jump back
-            // to the latest output. Mirrors the Mac's `JumpToBottomButton`.
-            .overlay(alignment: .bottom) {
-                ZStack {
-                    if !isScrolledToBottom {
-                        JumpToBottomButton { scrollToLast(proxy) }
-                            .padding(.bottom, 12)
-                            .transition(.move(edge: .bottom).combined(with: .opacity))
-                    }
-                }
-                .animation(.easeInOut(duration: 0.15), value: isScrolledToBottom)
+                if isScrolledToBottom { scrollToEnd(proxy, animated: !transcriptSettling) }
             }
+            // An explicit jump — the chevron or sending a message — always wins. The chevron
+            // itself lives in the parent's chat bar (above the composer), not as an overlay here,
+            // so it sits over the composer instead of behind the floating bar; a tap bumps this
+            // same request, and following resumes once the geometry reader sees the bottom.
+            .onChange(of: scrollToBottomRequest) { scrollToEnd(proxy) }
         }
     }
 
-    /// Scroll the last message to the bottom edge; `animated: false` during the open-settle
+    /// Scroll the fixed bottom anchor into view; `animated: false` during the open-settle
     /// window so a chat that's still laying out snaps to the tail instead of easing into place.
-    private func scrollToLast(_ proxy: ScrollViewProxy, animated: Bool = true) {
-        guard let last = items.last else { return }
+    private func scrollToEnd(_ proxy: ScrollViewProxy, animated: Bool = true) {
         if animated {
-            withAnimation { proxy.scrollTo(last.id, anchor: .bottom) }
+            withAnimation { proxy.scrollTo(Self.bottomAnchorID, anchor: .bottom) }
         } else {
-            proxy.scrollTo(last.id, anchor: .bottom)
+            proxy.scrollTo(Self.bottomAnchorID, anchor: .bottom)
         }
     }
+
+    private static let bottomAnchorID = "nucleic.transcript-bottom"
 }
 
 /// The floating "jump to the latest" chevron shown above the chat bar while the user has