diff --git a/ui-tui/src/app/useMainApp.ts b/ui-tui/src/app/useMainApp.ts
index 28b2a26f9a..8a5b0b1fde 100644
--- a/ui-tui/src/app/useMainApp.ts
+++ b/ui-tui/src/app/useMainApp.ts
@@ -161,7 +161,7 @@ export function useMainApp(gw: GatewayClient) {
     [historyItems, messageId]
   )
 
-  const virtualHistory = useVirtualHistory(scrollRef, virtualRows)
+  const virtualHistory = useVirtualHistory(scrollRef, virtualRows, cols)
 
   const scrollWithSelection = useCallback(
     (delta: number) => {
@@ -306,12 +306,26 @@ export function useMainApp(gw: GatewayClient) {
       return
     }
 
-    const onResize = () =>
-      rpc<TerminalResizeResponse>('terminal.resize', { cols: stdout.columns ?? 80, session_id: ui.sid })
+    let timer: null | ReturnType<typeof setTimeout> = null
+
+    const onResize = () => {
+      if (timer) {
+        clearTimeout(timer)
+      }
+
+      timer = setTimeout(() => {
+        timer = null
+        void rpc<TerminalResizeResponse>('terminal.resize', { cols: stdout.columns ?? 80, session_id: ui.sid })
+      }, 100)
+    }
 
     stdout.on('resize', onResize)
 
     return () => {
+      if (timer) {
+        clearTimeout(timer)
+      }
+
       stdout.off('resize', onResize)
     }
   }, [rpc, stdout, ui.sid])
diff --git a/ui-tui/src/hooks/useVirtualHistory.ts b/ui-tui/src/hooks/useVirtualHistory.ts
index efa2642df3..3d1d27c056 100644
--- a/ui-tui/src/hooks/useVirtualHistory.ts
+++ b/ui-tui/src/hooks/useVirtualHistory.ts
@@ -15,6 +15,7 @@ const OVERSCAN = 40
 const MAX_MOUNTED = 260
 const COLD_START = 40
 const QUANTUM = OVERSCAN >> 1
+const FREEZE_RENDERS = 2
 
 const upperBound = (arr: number[], target: number) => {
   let lo = 0,
@@ -31,6 +32,7 @@ const upperBound = (arr: number[], target: number) => {
 export function useVirtualHistory(
   scrollRef: RefObject<ScrollBoxHandle | null>,
   items: readonly { key: string }[],
+  columns: number,
   { estimate = ESTIMATE, overscan = OVERSCAN, maxMounted = MAX_MOUNTED, coldStartCount = COLD_START } = {}
 ) {
   const nodes = useRef(new Map<string, unknown>())
@@ -40,6 +42,34 @@ export function useVirtualHistory(
   const [hasScrollRef, setHasScrollRef] = useState(false)
   const metrics = useRef({ sticky: true, top: 0, vp: 0 })
 
+  // Resize handling — scale cached heights by oldCols/newCols so post-resize
+  // offsets stay roughly aligned with (still-unknown) real Yoga heights.
+  // Clearing the cache instead would force a pessimistic back-walk that mounts
+  // ~190 rows at once (viewport+overscan at 1-row estimate), each a fresh
+  // marked.lexer + syntax highlight = ~3ms; ~600ms React commit block. Freeze
+  // the mount range for FREEZE_RENDERS so warm useMemo results survive while
+  // the layout effect writes post-resize real heights back into cache.
+  // skipMeasurement prevents that first post-resize useLayoutEffect from
+  // poisoning the cache with pre-resize Yoga values (Yoga's stored heights
+  // are from the frame BEFORE this render's calculateLayout with new width).
+  const prevColumns = useRef(columns)
+  const skipMeasurement = useRef(false)
+  const prevRange = useRef<null | readonly [number, number]>(null)
+  const freezeRenders = useRef(0)
+
+  if (prevColumns.current !== columns && prevColumns.current > 0 && columns > 0) {
+    const ratio = prevColumns.current / columns
+
+    prevColumns.current = columns
+
+    for (const [k, h] of heights.current) {
+      heights.current.set(k, Math.max(1, Math.round(h * ratio)))
+    }
+
+    skipMeasurement.current = true
+    freezeRenders.current = FREEZE_RENDERS
+  }
+
   useLayoutEffect(() => {
     setHasScrollRef(Boolean(scrollRef.current))
   }, [scrollRef])
@@ -97,10 +127,19 @@ export function useVirtualHistory(
   const vp = Math.max(0, scrollRef.current?.getViewportHeight() ?? 0)
   const sticky = scrollRef.current?.isSticky() ?? true
 
+  const frozenRange = freezeRenders.current > 0 ? prevRange.current : null
+
   let start = 0,
     end = items.length
 
-  if (items.length > 0) {
+  if (frozenRange) {
+    // Columns just changed. Reuse the pre-resize mount range so already-mounted
+    // MessageRows keep their warm memos (marked.lexer, syntax highlight). Clamp
+    // to n in case messages were removed (/clear, compaction) mid-freeze.
+    ;[start, end] = frozenRange
+    start = Math.min(start, items.length)
+    end = Math.min(end, items.length)
+  } else if (items.length > 0) {
     if (vp <= 0) {
       start = Math.max(0, items.length - coldStartCount)
     } else {
@@ -113,6 +152,12 @@ export function useVirtualHistory(
     sticky ? (start = Math.max(0, end - maxMounted)) : (end = Math.min(items.length, start + maxMounted))
   }
 
+  if (freezeRenders.current > 0) {
+    freezeRenders.current--
+  } else {
+    prevRange.current = [start, end]
+  }
+
   const measureRef = useCallback((key: string) => {
     let fn = refs.current.get(key)
 
@@ -127,18 +172,25 @@ export function useVirtualHistory(
   useLayoutEffect(() => {
     let dirty = false
 
-    for (let i = start; i < end; i++) {
-      const k = items[i]?.key
+    if (skipMeasurement.current) {
+      // First render after a column change — Yoga heights still reflect the
+      // pre-resize layout. Writing them into cache would overwrite the scaled
+      // estimates with stale pre-resize values. Next render's Yoga is correct.
+      skipMeasurement.current = false
+    } else {
+      for (let i = start; i < end; i++) {
+        const k = items[i]?.key
 
-      if (!k) {
-        continue
-      }
+        if (!k) {
+          continue
+        }
 
-      const h = Math.ceil((nodes.current.get(k) as MeasuredNode | undefined)?.yogaNode?.getComputedHeight?.() ?? 0)
+        const h = Math.ceil((nodes.current.get(k) as MeasuredNode | undefined)?.yogaNode?.getComputedHeight?.() ?? 0)
 
-      if (h > 0 && heights.current.get(k) !== h) {
-        heights.current.set(k, h)
-        dirty = true
+        if (h > 0 && heights.current.get(k) !== h) {
+          heights.current.set(k, h)
+          dirty = true
+        }
       }
     }