From fde912e93b961cb4c708f273eb703af9d7efa0f2 Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Tue, 21 Jul 2026 19:42:32 -0700
Subject: [PATCH 01/12] fix(mothership): freeze the transcript on user stop
 instead of settle-scrolling

---
 .../mothership-chat/mothership-chat.tsx       | 19 +++++++++++++++++--
 apps/sim/hooks/use-auto-scroll.ts             | 14 ++++++++++++--
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
index db903e8398a..dcf171cb463 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
@@ -299,7 +299,22 @@ export function MothershipChat({
   const messages = useDeferredValue(messagesProp)
   const [lastRowAnimating, setLastRowAnimating] = useState(false)
   const scrollElementRef = useRef<HTMLDivElement | null>(null)
-  const { ref: autoScrollRef } = useAutoScroll(isStreamActive || lastRowAnimating)
+  /**
+   * True from the stop button until the next stream: a stopped turn must not
+   * settle-scroll — the user asked everything to freeze, and following the
+   * stopped-row/actions mount nudges the transcript up right after they did.
+   */
+  const stopRequestedRef = useRef(false)
+  const handleStopGeneration = useCallback(() => {
+    stopRequestedRef.current = true
+    onStopGeneration()
+  }, [onStopGeneration])
+  useEffect(() => {
+    if (isStreamActive) stopRequestedRef.current = false
+  }, [isStreamActive])
+  const { ref: autoScrollRef } = useAutoScroll(isStreamActive || lastRowAnimating, {
+    shouldFollowSettle: () => !stopRequestedRef.current,
+  })
   const sizerRef = useRef<HTMLDivElement | null>(null)
   const scrollerPaddingRef = useRef<{ top: number; bottom: number } | null>(null)
 
@@ -618,7 +633,7 @@ export function MothershipChat({
               ref={userInputRef}
               onSubmit={onSubmit}
               isSending={isStreamActive}
-              onStopGeneration={onStopGeneration}
+              onStopGeneration={handleStopGeneration}
               isInitialView={false}
               onSendQueuedHead={handleSendQueuedHead}
               onEditQueuedTail={handleEditQueuedTail}
diff --git a/apps/sim/hooks/use-auto-scroll.ts b/apps/sim/hooks/use-auto-scroll.ts
index d5edf8977ba..a7f4fce4c47 100644
--- a/apps/sim/hooks/use-auto-scroll.ts
+++ b/apps/sim/hooks/use-auto-scroll.ts
@@ -39,6 +39,12 @@ const POST_STREAM_SETTLE_WINDOW = 300
 
 interface UseAutoScrollOptions {
   scrollOnMount?: boolean
+  /**
+   * Consulted at stream teardown; return false to skip the post-stream settle
+   * follow. A user-initiated stop means "freeze" — chasing the stopped-row and
+   * actions mount would visibly nudge the transcript the user just halted.
+   */
+  shouldFollowSettle?: () => boolean
 }
 
 /**
@@ -55,10 +61,12 @@ interface UseAutoScrollOptions {
  */
 export function useAutoScroll(
   isStreaming: boolean,
-  { scrollOnMount = false }: UseAutoScrollOptions = {}
+  { scrollOnMount = false, shouldFollowSettle }: UseAutoScrollOptions = {}
 ) {
   const containerRef = useRef<HTMLDivElement>(null)
   const stickyRef = useRef(true)
+  const shouldFollowSettleRef = useRef(shouldFollowSettle)
+  shouldFollowSettleRef.current = shouldFollowSettle
   const userDetachedRef = useRef(false)
   const prevScrollTopRef = useRef(0)
   const prevScrollHeightRef = useRef(0)
@@ -237,7 +245,9 @@ export function useAutoScroll(
       // End-of-turn content mounts just after teardown; follow it briefly. The
       // chase's own upward-move interrupt still protects a real user scroll
       // even with the gesture listeners gone.
-      chase.kickUntil(POST_STREAM_SETTLE_WINDOW)
+      if (shouldFollowSettleRef.current?.() !== false) {
+        chase.kickUntil(POST_STREAM_SETTLE_WINDOW)
+      }
     }
   }, [isStreaming, scrollToBottom])
 

From fff6119766f26c5a5943ee4d7a0cfad1b8e88783 Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Tue, 21 Jul 2026 21:05:58 -0700
Subject: [PATCH 02/12] fix(mothership): swap stopped row into the shimmer slot
 and floor the sizer min-height

---
 .../message-content/message-content.tsx       | 27 ++++++++++++-------
 .../mothership-chat/mothership-chat.tsx       |  9 ++++++-
 2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
index 2abcec9fad5..13ec42f4557 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
@@ -943,13 +943,12 @@ function MessageContentInner({
                   <Options items={segment.items} onSelect={onOptionSelect} />
                 </div>
               )
+            // The stopped row renders in the tail region below, in the
+            // shimmer's place — a stop while the shimmer is visible must read
+            // as an in-place replacement, not the shimmer vanishing from the
+            // tail while a row mounts up here.
             case 'stopped':
-              return (
-                <div key={`stopped-${i}`} className='flex items-center gap-[8px]'>
-                  <CircleStop className='size-[16px] flex-shrink-0 text-[var(--text-icon)]' />
-                  <span className='text-[14px] text-[var(--text-body)]'>Stopped by user</span>
-                </div>
-              )
+              return null
           }
         })}
       </div>
@@ -969,10 +968,18 @@ function MessageContentInner({
           </div>
         </div>
       ) : (
-        // The actions row takes the slot's place in the SAME render — a single
-        // ~10px reflow instead of a collapse the buttons would ride upward or a
-        // late mount the chase would visibly scroll to.
-        actions && <div className='mt-2.5'>{actions}</div>
+        // Stopped row and actions take the slot's place in the SAME render — a
+        // single small reflow instead of a collapse the buttons would ride
+        // upward or a late mount the chase would visibly scroll to.
+        <>
+          {lastSegment?.type === 'stopped' && (
+            <div className='flex items-center gap-[8px] pt-[10px]'>
+              <CircleStop className='size-[16px] flex-shrink-0 text-[var(--text-icon)]' />
+              <span className='text-[14px] text-[var(--text-body)]'>Stopped by user</span>
+            </div>
+          )}
+          {actions && <div className='mt-[10px]'>{actions}</div>}
+        </>
       )}
     </div>
   )
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
index dcf171cb463..a92563dc4fd 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
@@ -351,7 +351,14 @@ export function MothershipChat({
       }
     }
     const padding = scrollerPaddingRef.current
-    const floor = Math.max(0, el.scrollTop + el.clientHeight - padding.top - padding.bottom)
+    // Math.floor, not the raw float: a fractional min-height can round
+    // scrollHeight 1px ABOVE the scrolled-to extent, and that phantom 1px gap
+    // re-derives 1px higher after every chase step — a visible 1px/frame
+    // upward creep whenever the floor is what's holding scrollHeight.
+    const floor = Math.max(
+      0,
+      Math.floor(el.scrollTop + el.clientHeight - padding.top - padding.bottom)
+    )
     sizer.style.minHeight = `${floor}px`
   })
   const setScrollElement = useCallback(

From e7ea9db9f75c9b192e917abd05f035a4038b27ce Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 10:28:42 -0700
Subject: [PATCH 03/12] fix(mothership): detach auto-scroll on stop and
 dead-band the sizer floor

---
 .../mothership-chat/mothership-chat.tsx       | 30 +++++++++++-------
 apps/sim/hooks/use-auto-scroll.ts             | 31 +++++++++----------
 2 files changed, 33 insertions(+), 28 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
index a92563dc4fd..827867d72f8 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
@@ -299,24 +299,22 @@ export function MothershipChat({
   const messages = useDeferredValue(messagesProp)
   const [lastRowAnimating, setLastRowAnimating] = useState(false)
   const scrollElementRef = useRef<HTMLDivElement | null>(null)
+  const { ref: autoScrollRef, detach: detachAutoScroll } = useAutoScroll(
+    isStreamActive || lastRowAnimating
+  )
   /**
-   * True from the stop button until the next stream: a stopped turn must not
-   * settle-scroll — the user asked everything to freeze, and following the
-   * stopped-row/actions mount nudges the transcript up right after they did.
+   * Stop means freeze: detach auto-scroll exactly like a user scroll-away, so
+   * every chase path — mutation kicks while the reveal drains, animation
+   * follows, the settle window — parks instead of nudging the transcript the
+   * user just halted. The next stream re-seeds stickiness from position.
    */
-  const stopRequestedRef = useRef(false)
   const handleStopGeneration = useCallback(() => {
-    stopRequestedRef.current = true
+    detachAutoScroll()
     onStopGeneration()
-  }, [onStopGeneration])
-  useEffect(() => {
-    if (isStreamActive) stopRequestedRef.current = false
-  }, [isStreamActive])
-  const { ref: autoScrollRef } = useAutoScroll(isStreamActive || lastRowAnimating, {
-    shouldFollowSettle: () => !stopRequestedRef.current,
-  })
+  }, [detachAutoScroll, onStopGeneration])
   const sizerRef = useRef<HTMLDivElement | null>(null)
   const scrollerPaddingRef = useRef<{ top: number; bottom: number } | null>(null)
+  const sizerFloorAppliedRef = useRef(0)
 
   /**
    * Sizer floor while streaming: `scrollHeight` must never dip below the
@@ -340,6 +338,7 @@ export function MothershipChat({
     const el = scrollElementRef.current
     if (!sizer || !el) return
     if (!floorActive) {
+      sizerFloorAppliedRef.current = 0
       sizer.style.minHeight = ''
       return
     }
@@ -359,6 +358,13 @@ export function MothershipChat({
       0,
       Math.floor(el.scrollTop + el.clientHeight - padding.top - padding.bottom)
     )
+    // Dead-band: the floor feeds back into its own inputs (a floored value can
+    // land a fraction BELOW the extent, the browser clamps scrollTop, and the
+    // next commit re-derives from the clamped position — a visible ~1px×N
+    // downward cascade on fractional-scrollTop displays). Sub-pixel deltas are
+    // rounding noise from that loop, never real growth; only apply real moves.
+    if (Math.abs(floor - sizerFloorAppliedRef.current) <= 1) return
+    sizerFloorAppliedRef.current = floor
     sizer.style.minHeight = `${floor}px`
   })
   const setScrollElement = useCallback(
diff --git a/apps/sim/hooks/use-auto-scroll.ts b/apps/sim/hooks/use-auto-scroll.ts
index a7f4fce4c47..254f25ca0ce 100644
--- a/apps/sim/hooks/use-auto-scroll.ts
+++ b/apps/sim/hooks/use-auto-scroll.ts
@@ -39,12 +39,6 @@ const POST_STREAM_SETTLE_WINDOW = 300
 
 interface UseAutoScrollOptions {
   scrollOnMount?: boolean
-  /**
-   * Consulted at stream teardown; return false to skip the post-stream settle
-   * follow. A user-initiated stop means "freeze" — chasing the stopped-row and
-   * actions mount would visibly nudge the transcript the user just halted.
-   */
-  shouldFollowSettle?: () => boolean
 }
 
 /**
@@ -56,17 +50,18 @@ interface UseAutoScrollOptions {
  * of the bottom to re-engage. Each streaming start re-seeds stickiness from the
  * current scroll position, so a user who scrolled up beforehand stays put.
  *
- * Returns `ref` (callback ref for the scroll container) and `scrollToBottom`
- * for imperative use after layout-changing events like panel expansion.
+ * Returns `ref` (callback ref for the scroll container), `scrollToBottom` for
+ * imperative use after layout-changing events like panel expansion, and
+ * `detach` for programmatic freezes (a user stop) — it parks every chase path
+ * exactly like a user scroll-away, until the user scrolls back to the bottom
+ * or the next stream re-seeds stickiness.
  */
 export function useAutoScroll(
   isStreaming: boolean,
-  { scrollOnMount = false, shouldFollowSettle }: UseAutoScrollOptions = {}
+  { scrollOnMount = false }: UseAutoScrollOptions = {}
 ) {
   const containerRef = useRef<HTMLDivElement>(null)
   const stickyRef = useRef(true)
-  const shouldFollowSettleRef = useRef(shouldFollowSettle)
-  shouldFollowSettleRef.current = shouldFollowSettle
   const userDetachedRef = useRef(false)
   const prevScrollTopRef = useRef(0)
   const prevScrollHeightRef = useRef(0)
@@ -91,6 +86,11 @@ export function useAutoScroll(
     el.scrollTop = el.scrollHeight
   }, [])
 
+  const detach = useCallback(() => {
+    stickyRef.current = false
+    userDetachedRef.current = true
+  }, [])
+
   const callbackRef = useCallback((el: HTMLDivElement | null) => {
     containerRef.current = el
     if (el && scrollOnMountRef.current) el.scrollTop = el.scrollHeight
@@ -244,12 +244,11 @@ export function useAutoScroll(
       lastUserGestureAtRef.current = Number.NEGATIVE_INFINITY
       // End-of-turn content mounts just after teardown; follow it briefly. The
       // chase's own upward-move interrupt still protects a real user scroll
-      // even with the gesture listeners gone.
-      if (shouldFollowSettleRef.current?.() !== false) {
-        chase.kickUntil(POST_STREAM_SETTLE_WINDOW)
-      }
+      // even with the gesture listeners gone, and the per-frame sticky check
+      // makes this a no-op after a detach().
+      chase.kickUntil(POST_STREAM_SETTLE_WINDOW)
     }
   }, [isStreaming, scrollToBottom])
 
-  return { ref: callbackRef, scrollToBottom }
+  return { ref: callbackRef, scrollToBottom, detach }
 }

From c9d7e7c8a0bb5444a8d1a54a591fa4e1cc5a8e93 Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 10:57:04 -0700
Subject: [PATCH 04/12] =?UTF-8?q?improvement(mothership):=20net-zero=20set?=
 =?UTF-8?q?tle=20=E2=80=94=20equal=20tail=20regions,=20drained=20floor,=20?=
 =?UTF-8?q?one=20growth=20signal?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../message-content/message-content.tsx       | 21 +++--
 .../mothership-chat/mothership-chat.tsx       | 38 ++++++++-
 apps/sim/hooks/use-auto-scroll.ts             | 80 ++++++-------------
 .../sim/lib/core/utils/smooth-bottom-chase.ts | 28 +------
 4 files changed, 74 insertions(+), 93 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
index 13ec42f4557..173e6528e16 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
@@ -30,6 +30,13 @@ import { deriveMessagePhase, isToolDone, type MessagePhase } from './utils'
 const FILE_SUBAGENT_ID = 'file'
 /** Quiet period before the shimmer takes the slot back from streamed output. */
 const STREAM_IDLE_DELAY_MS = 1_500
+/**
+ * The one vertical extent (10px gap + 36px row) every tail-region occupant —
+ * shimmer slot, actions row, stopped row — must share. The settle swap is only
+ * jump-free because these are equal; changing one side without the others
+ * reintroduces a scroll clamp at end of turn.
+ */
+const TAIL_REGION_CLASSES = 'mt-[10px] flex h-[36px] items-center'
 
 interface TextSegment {
   type: 'text'
@@ -956,8 +963,8 @@ function MessageContentInner({
         // Fixed-height placeholder for the NEXT piece of output: the shimmer
         // and arriving output trade places via opacity only, so mid-turn swaps
         // can't move layout. A sibling of the space-y stack (not a child), so
-        // it carries no stray sibling margin — pt-[10px] is its own gap.
-        <div aria-hidden={!showShimmer} className='pt-[10px]'>
+        // it carries no stray sibling margin.
+        <div aria-hidden={!showShimmer} className={TAIL_REGION_CLASSES}>
           <div
             className={cn(
               'transition-opacity duration-200 ease-out',
@@ -968,17 +975,17 @@ function MessageContentInner({
           </div>
         </div>
       ) : (
-        // Stopped row and actions take the slot's place in the SAME render — a
-        // single small reflow instead of a collapse the buttons would ride
-        // upward or a late mount the chase would visibly scroll to.
+        // Stopped row and actions take the slot's place in the SAME render and
+        // at the SAME extent (TAIL_REGION_CLASSES), so the swap is height-
+        // neutral by construction — no reflow for the pinned scroller to absorb.
         <>
           {lastSegment?.type === 'stopped' && (
-            <div className='flex items-center gap-[8px] pt-[10px]'>
+            <div className={cn(TAIL_REGION_CLASSES, 'gap-[8px]')}>
               <CircleStop className='size-[16px] flex-shrink-0 text-[var(--text-icon)]' />
               <span className='text-[14px] text-[var(--text-body)]'>Stopped by user</span>
             </div>
           )}
-          {actions && <div className='mt-[10px]'>{actions}</div>}
+          {actions && <div className={TAIL_REGION_CLASSES}>{actions}</div>}
         </>
       )}
     </div>
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
index 827867d72f8..b65df433261 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
@@ -12,6 +12,7 @@ import {
 } from 'react'
 import { cn } from '@sim/emcn'
 import { defaultRangeExtractor, type Range, useVirtualizer } from '@tanstack/react-virtual'
+import { SMOOTH_CHASE_RATE } from '@/lib/core/utils/smooth-bottom-chase'
 import { MessageActions } from '@/app/workspace/[workspaceId]/components'
 import { ChatMessageAttachments } from '@/app/workspace/[workspaceId]/home/components/chat-message-attachments'
 import { ChatSurfaceProvider } from '@/app/workspace/[workspaceId]/home/components/chat-surface-context'
@@ -109,7 +110,7 @@ const UNSCROLLED = Symbol('unscrolled')
 const LAYOUT_STYLES = {
   'mothership-view': {
     scrollContainer:
-      'min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-6 pt-4 pb-2 [scrollbar-gutter:stable_both-edges]',
+      'min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-6 pt-4 pb-2 [overflow-anchor:none] [scrollbar-gutter:stable_both-edges]',
     sizer: 'relative mx-auto w-full max-w-[48rem]',
     rowGap: 'pb-6',
     userRow: 'flex flex-col items-end gap-[6px] pt-3',
@@ -120,7 +121,8 @@ const LAYOUT_STYLES = {
     footerInner: 'mx-auto max-w-[48rem]',
   },
   'copilot-view': {
-    scrollContainer: 'min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-3 pt-2 pb-4',
+    scrollContainer:
+      'min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-3 pt-2 pb-4 [overflow-anchor:none]',
     sizer: 'relative w-full',
     rowGap: 'pb-4',
     userRow: 'flex flex-col items-end gap-[6px] pt-2',
@@ -315,6 +317,7 @@ export function MothershipChat({
   const sizerRef = useRef<HTMLDivElement | null>(null)
   const scrollerPaddingRef = useRef<{ top: number; bottom: number } | null>(null)
   const sizerFloorAppliedRef = useRef(0)
+  const floorDrainRafRef = useRef(0)
 
   /**
    * Sizer floor while streaming: `scrollHeight` must never dip below the
@@ -331,6 +334,15 @@ export function MothershipChat({
    * Active on the same signal as auto-scroll: the reveal keeps re-parsing
    * markdown (and shrinking) after the network stream closes, so the floor
    * must hold through `lastRowAnimating` too.
+   *
+   * Release is DRAINED, not cliffed: while active the floor forbids
+   * scrollHeight from dropping, so permanent shrinks over the turn accrue as
+   * phantom space (debt). Clearing min-height in one commit released that
+   * whole debt as a single clamp — the end-of-turn downward jump. Instead the
+   * floor glides down to the natural size at the chase's rate; the browser's
+   * clamp follows a few px per frame, which reads as the same eased settle as
+   * the rest of the stream. Instant-clears when the debt is sub-pixel or the
+   * user isn't pinned (shrinking below-viewport space is invisible then).
    */
   const floorActive = isStreamActive || lastRowAnimating
   useLayoutEffect(() => {
@@ -338,10 +350,28 @@ export function MothershipChat({
     const el = scrollElementRef.current
     if (!sizer || !el) return
     if (!floorActive) {
-      sizerFloorAppliedRef.current = 0
-      sizer.style.minHeight = ''
+      if (sizerFloorAppliedRef.current === 0) return
+      scrollerPaddingRef.current = null
+      const pinned = el.scrollHeight - el.scrollTop - el.clientHeight <= 2
+      cancelAnimationFrame(floorDrainRafRef.current)
+      const drain = () => {
+        const target = virtualizer.getTotalSize()
+        const current = sizerFloorAppliedRef.current
+        if (current === 0) return
+        const next = Math.floor(current - Math.max(1, (current - target) * SMOOTH_CHASE_RATE))
+        if (!pinned || next - target <= 1) {
+          sizerFloorAppliedRef.current = 0
+          sizer.style.minHeight = ''
+          return
+        }
+        sizerFloorAppliedRef.current = next
+        sizer.style.minHeight = `${next}px`
+        floorDrainRafRef.current = requestAnimationFrame(drain)
+      }
+      drain()
       return
     }
+    cancelAnimationFrame(floorDrainRafRef.current)
     if (!scrollerPaddingRef.current) {
       const style = getComputedStyle(el)
       scrollerPaddingRef.current = {
diff --git a/apps/sim/hooks/use-auto-scroll.ts b/apps/sim/hooks/use-auto-scroll.ts
index 254f25ca0ce..2df1efda434 100644
--- a/apps/sim/hooks/use-auto-scroll.ts
+++ b/apps/sim/hooks/use-auto-scroll.ts
@@ -25,22 +25,6 @@ const USER_GESTURE_WINDOW = 250
  * in the listener) is the other upward shortcut; plain `Space` pages down.
  */
 const SCROLL_UP_KEYS = new Set(['ArrowUp', 'PageUp', 'Home'])
-/** How long to keep chasing the bottom while a CSS height animation plays. */
-const ANIMATION_FOLLOW_WINDOW = 500
-/**
- * How long to keep chasing the bottom after streaming stops. End-of-turn content
- * mounts just after `isStreaming` flips false — the suggested-follow-up options,
- * the actions row (swapped into the thinking slot's place), and the
- * virtualizer's re-measure of the grown row — so a single final scroll fires
- * before it lays out and leaves it clipped behind the input. Following for a
- * short window pulls it into view.
- */
-const POST_STREAM_SETTLE_WINDOW = 300
-
-interface UseAutoScrollOptions {
-  scrollOnMount?: boolean
-}
-
 /**
  * Manages sticky auto-scroll for a streaming chat container.
  *
@@ -50,23 +34,18 @@ interface UseAutoScrollOptions {
  * of the bottom to re-engage. Each streaming start re-seeds stickiness from the
  * current scroll position, so a user who scrolled up beforehand stays put.
  *
- * Returns `ref` (callback ref for the scroll container), `scrollToBottom` for
- * imperative use after layout-changing events like panel expansion, and
- * `detach` for programmatic freezes (a user stop) — it parks every chase path
- * exactly like a user scroll-away, until the user scrolls back to the bottom
- * or the next stream re-seeds stickiness.
+ * Returns `ref` (callback ref for the scroll container) and `detach` for
+ * programmatic freezes (a user stop) — it parks every chase path exactly like
+ * a user scroll-away, until the user scrolls back to the bottom or the next
+ * stream re-seeds stickiness.
  */
-export function useAutoScroll(
-  isStreaming: boolean,
-  { scrollOnMount = false }: UseAutoScrollOptions = {}
-) {
+export function useAutoScroll(isStreaming: boolean) {
   const containerRef = useRef<HTMLDivElement>(null)
   const stickyRef = useRef(true)
   const userDetachedRef = useRef(false)
   const prevScrollTopRef = useRef(0)
   const prevScrollHeightRef = useRef(0)
   const touchStartYRef = useRef(0)
-  const scrollOnMountRef = useRef(scrollOnMount)
   /**
    * Whether the user is actively dragging the scrollbar — a pointer press on the
    * container itself rather than its content. Reset on teardown so a pointer held
@@ -80,12 +59,6 @@ export function useAutoScroll(
    */
   const lastUserGestureAtRef = useRef(Number.NEGATIVE_INFINITY)
 
-  const scrollToBottom = useCallback(() => {
-    const el = containerRef.current
-    if (!el) return
-    el.scrollTop = el.scrollHeight
-  }, [])
-
   const detach = useCallback(() => {
     stickyRef.current = false
     userDetachedRef.current = true
@@ -93,7 +66,6 @@ export function useAutoScroll(
 
   const callbackRef = useCallback((el: HTMLDivElement | null) => {
     containerRef.current = el
-    if (el && scrollOnMountRef.current) el.scrollTop = el.scrollHeight
   }, [])
 
   useEffect(() => {
@@ -198,42 +170,38 @@ export function useAutoScroll(
       prevScrollHeightRef.current = scrollHeight
     }
 
-    const onMutation = () => {
+    /**
+     * The single growth signal: the transcript sizer's height. Every source of
+     * scrollHeight growth flows through it — virtualizer re-measures per
+     * streamed token, CSS height animations (each frame re-measures the row),
+     * the sizer min-height floor — so one ResizeObserver replaces a subtree
+     * MutationObserver plus an `animationstart` deadline machine, and there is
+     * exactly one reason the chase ever runs.
+     */
+    const sizer = el.firstElementChild
+    const onSizerResize = () => {
       prevScrollHeightRef.current = el.scrollHeight
       if (!stickyRef.current) return
       chase.kick()
     }
 
-    /**
-     * CSS-driven height animations (e.g. Radix Collapsible expanding mid-stream)
-     * grow scrollHeight without triggering MutationObserver, so auto-scroll stops
-     * following. Keep the one chase loop alive for a short window so the
-     * container stays pinned while the animation runs. `animationstart` fires
-     * for every child animation in the transcript (segment fade-ins, loader
-     * keyframes, label crossfades) — kickUntil coalesces them into a single
-     * extended deadline on the single loop; anything more snaps the glide.
-     */
-    const onAnimationStart = () => chase.kickUntil(ANIMATION_FOLLOW_WINDOW)
-
     el.addEventListener('wheel', onWheel, { passive: true })
     el.addEventListener('touchstart', onTouchStart, { passive: true })
     el.addEventListener('touchmove', onTouchMove, { passive: true })
     el.addEventListener('scroll', onScroll, { passive: true })
-    el.addEventListener('animationstart', onAnimationStart)
     el.addEventListener('pointerdown', onPointerDown, { passive: true })
     el.addEventListener('keydown', onKeyDown, { passive: true })
     window.addEventListener('pointerup', onPointerUp, { passive: true })
     window.addEventListener('pointercancel', onPointerUp, { passive: true })
 
-    const observer = new MutationObserver(onMutation)
-    observer.observe(el, { childList: true, subtree: true, characterData: true })
+    const observer = new ResizeObserver(onSizerResize)
+    if (sizer) observer.observe(sizer)
 
     return () => {
       el.removeEventListener('wheel', onWheel)
       el.removeEventListener('touchstart', onTouchStart)
       el.removeEventListener('touchmove', onTouchMove)
       el.removeEventListener('scroll', onScroll)
-      el.removeEventListener('animationstart', onAnimationStart)
       el.removeEventListener('pointerdown', onPointerDown)
       el.removeEventListener('keydown', onKeyDown)
       window.removeEventListener('pointerup', onPointerUp)
@@ -242,13 +210,13 @@ export function useAutoScroll(
       chase.cancel()
       pointerDownRef.current = false
       lastUserGestureAtRef.current = Number.NEGATIVE_INFINITY
-      // End-of-turn content mounts just after teardown; follow it briefly. The
-      // chase's own upward-move interrupt still protects a real user scroll
-      // even with the gesture listeners gone, and the per-frame sticky check
-      // makes this a no-op after a detach().
-      chase.kickUntil(POST_STREAM_SETTLE_WINDOW)
+      // Teardown can land mid-glide (options mounted late in the reveal, gap
+      // not yet closed) — canceling there strands the follow-ups behind the
+      // input. One plain kick runs the loop to rest and parks; a stopped turn
+      // stays frozen because the detached sticky check parks it on frame one.
+      chase.kick()
     }
-  }, [isStreaming, scrollToBottom])
+  }, [isStreaming])
 
-  return { ref: callbackRef, scrollToBottom, detach }
+  return { ref: callbackRef, detach }
 }
diff --git a/apps/sim/lib/core/utils/smooth-bottom-chase.ts b/apps/sim/lib/core/utils/smooth-bottom-chase.ts
index 90c3b9d8e84..ad31140bd96 100644
--- a/apps/sim/lib/core/utils/smooth-bottom-chase.ts
+++ b/apps/sim/lib/core/utils/smooth-bottom-chase.ts
@@ -26,14 +26,6 @@ export interface SmoothBottomChaseHandle {
   isActive: () => boolean
   /** Start the loop if parked. Call after content growth. */
   kick: () => void
-  /**
-   * Keep the loop alive for `durationMs` even while the gap is at rest,
-   * re-checking every frame. Covers growth that arrives over several frames
-   * with no observable trigger — a CSS height animation, or a virtualizer
-   * re-measure settling after streaming stops. Repeat calls extend the
-   * deadline; there is never more than one loop.
-   */
-  kickUntil: (durationMs: number) => void
   cancel: () => void
 }
 
@@ -55,15 +47,11 @@ export function createSmoothBottomChase(
 ): SmoothBottomChaseHandle {
   let raf: number | null = null
   let lastTop: number | null = null
-  let deadline = 0
 
   const park = () => {
     if (raf !== null) cancelAnimationFrame(raf)
     raf = null
     lastTop = null
-    // A stale deadline must not leak into a later plain kick() — kick alone
-    // parks at rest, only a live kickUntil window idles through it.
-    deadline = 0
   }
 
   const step = () => {
@@ -83,14 +71,7 @@ export function createSmoothBottomChase(
     }
     const gap = target.getBottomTop() - top
     if (gap <= CHASE_REST_GAP) {
-      // Within a kickUntil deadline the loop idles at rest instead of parking,
-      // so growth in the deadline window is chased without a fresh trigger.
-      if (performance.now() >= deadline) {
-        park()
-        return
-      }
-      lastTop = top
-      raf = requestAnimationFrame(step)
+      park()
       return
     }
     target.setTop(top + Math.max(1, gap * SMOOTH_CHASE_RATE))
@@ -105,8 +86,7 @@ export function createSmoothBottomChase(
    * Seed the upward-move interrupt baseline at (re)start so a user scroll-up
    * between the kick and the first frame parks the loop immediately — without
    * it the first step has no baseline and writes one downward frame against
-   * the user (relevant on the teardown kickUntil, where the gesture listeners
-   * are already gone).
+   * the user.
    */
   const start = () => {
     if (raf !== null) return
@@ -117,10 +97,6 @@ export function createSmoothBottomChase(
   return {
     isActive: () => raf !== null,
     kick: start,
-    kickUntil: (durationMs: number) => {
-      deadline = Math.max(deadline, performance.now() + durationMs)
-      start()
-    },
     cancel: park,
   }
 }

From cb63d01b2f1ef71a0f00a56eea30978deccafc49 Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 11:10:58 -0700
Subject: [PATCH 05/12] fix(mothership): follow the post-stop drain to the end
 instead of freezing

---
 .../message-content/message-content.tsx       | 18 ++++++++----
 .../mothership-chat/mothership-chat.tsx       | 16 ++--------
 apps/sim/hooks/use-auto-scroll.ts             | 29 +++++++++----------
 .../sim/lib/core/utils/smooth-bottom-chase.ts | 22 +++++++++++++-
 4 files changed, 50 insertions(+), 35 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
index 173e6528e16..846bfea31e5 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
@@ -860,8 +860,16 @@ function MessageContentInner({
   }, [visibleStreamActivityKey, isStreaming])
 
   const lastSegment = segments[segments.length - 1]
-  const hasTrailingTextSegment = lastSegment?.type === 'text'
-  const isRevealing = hasTrailingTextSegment && trailingRevealing
+  // The reveal tail is the last TEXT segment — a stopped block appends AFTER
+  // the text that is still visibly draining, and treating the turn as settled
+  // the moment it lands tears down the scroll machinery mid-reveal.
+  const revealTailIndex =
+    lastSegment?.type === 'stopped' && segments[segments.length - 2]?.type === 'text'
+      ? segments.length - 2
+      : lastSegment?.type === 'text'
+        ? segments.length - 1
+        : -1
+  const isRevealing = revealTailIndex >= 0 && trailingRevealing
   const phase = deriveMessagePhase({ isStreaming, isRevealing })
 
   const onPhaseChangeRef = useRef(onPhaseChange)
@@ -912,13 +920,13 @@ function MessageContentInner({
                   onQuestionDismiss={onQuestionDismiss}
                   onWorkspaceResourceSelect={onWorkspaceResourceSelect}
                   onRevealStateChange={
-                    i === segments.length - 1 ? handleTrailingRevealChange : undefined
+                    i === revealTailIndex ? handleTrailingRevealChange : undefined
                   }
                   onStreamActivityChange={
-                    i === segments.length - 1 ? handleTrailingStreamActivityChange : undefined
+                    i === revealTailIndex ? handleTrailingStreamActivityChange : undefined
                   }
                   onPendingTagChange={
-                    i === segments.length - 1 ? handleTrailingPendingTagChange : undefined
+                    i === revealTailIndex ? handleTrailingPendingTagChange : undefined
                   }
                 />
               )
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
index b65df433261..1273a58e701 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
@@ -301,19 +301,7 @@ export function MothershipChat({
   const messages = useDeferredValue(messagesProp)
   const [lastRowAnimating, setLastRowAnimating] = useState(false)
   const scrollElementRef = useRef<HTMLDivElement | null>(null)
-  const { ref: autoScrollRef, detach: detachAutoScroll } = useAutoScroll(
-    isStreamActive || lastRowAnimating
-  )
-  /**
-   * Stop means freeze: detach auto-scroll exactly like a user scroll-away, so
-   * every chase path — mutation kicks while the reveal drains, animation
-   * follows, the settle window — parks instead of nudging the transcript the
-   * user just halted. The next stream re-seeds stickiness from position.
-   */
-  const handleStopGeneration = useCallback(() => {
-    detachAutoScroll()
-    onStopGeneration()
-  }, [detachAutoScroll, onStopGeneration])
+  const { ref: autoScrollRef } = useAutoScroll(isStreamActive || lastRowAnimating)
   const sizerRef = useRef<HTMLDivElement | null>(null)
   const scrollerPaddingRef = useRef<{ top: number; bottom: number } | null>(null)
   const sizerFloorAppliedRef = useRef(0)
@@ -676,7 +664,7 @@ export function MothershipChat({
               ref={userInputRef}
               onSubmit={onSubmit}
               isSending={isStreamActive}
-              onStopGeneration={handleStopGeneration}
+              onStopGeneration={onStopGeneration}
               isInitialView={false}
               onSendQueuedHead={handleSendQueuedHead}
               onEditQueuedTail={handleEditQueuedTail}
diff --git a/apps/sim/hooks/use-auto-scroll.ts b/apps/sim/hooks/use-auto-scroll.ts
index 2df1efda434..c5ae57f9a28 100644
--- a/apps/sim/hooks/use-auto-scroll.ts
+++ b/apps/sim/hooks/use-auto-scroll.ts
@@ -25,6 +25,12 @@ const USER_GESTURE_WINDOW = 250
  * in the listener) is the other upward shortcut; plain `Space` pages down.
  */
 const SCROLL_UP_KEYS = new Set(['ArrowUp', 'PageUp', 'Home'])
+/**
+ * How long the chase idle-follows after stream teardown. Covers content that
+ * mounts with the observers already gone — a stop's stopped-row and actions
+ * append only after the abort round-trips.
+ */
+const POST_STOP_SETTLE_WINDOW = 800
 /**
  * Manages sticky auto-scroll for a streaming chat container.
  *
@@ -34,10 +40,7 @@ const SCROLL_UP_KEYS = new Set(['ArrowUp', 'PageUp', 'Home'])
  * of the bottom to re-engage. Each streaming start re-seeds stickiness from the
  * current scroll position, so a user who scrolled up beforehand stays put.
  *
- * Returns `ref` (callback ref for the scroll container) and `detach` for
- * programmatic freezes (a user stop) — it parks every chase path exactly like
- * a user scroll-away, until the user scrolls back to the bottom or the next
- * stream re-seeds stickiness.
+ * Returns `ref`, the callback ref for the scroll container.
  */
 export function useAutoScroll(isStreaming: boolean) {
   const containerRef = useRef<HTMLDivElement>(null)
@@ -59,11 +62,6 @@ export function useAutoScroll(isStreaming: boolean) {
    */
   const lastUserGestureAtRef = useRef(Number.NEGATIVE_INFINITY)
 
-  const detach = useCallback(() => {
-    stickyRef.current = false
-    userDetachedRef.current = true
-  }, [])
-
   const callbackRef = useCallback((el: HTMLDivElement | null) => {
     containerRef.current = el
   }, [])
@@ -210,13 +208,14 @@ export function useAutoScroll(isStreaming: boolean) {
       chase.cancel()
       pointerDownRef.current = false
       lastUserGestureAtRef.current = Number.NEGATIVE_INFINITY
-      // Teardown can land mid-glide (options mounted late in the reveal, gap
-      // not yet closed) — canceling there strands the follow-ups behind the
-      // input. One plain kick runs the loop to rest and parks; a stopped turn
-      // stays frozen because the detached sticky check parks it on frame one.
-      chase.kick()
+      // Growth can land after teardown with no observer alive: options mounted
+      // late in the reveal, and a stop's stopped-row/actions appending once the
+      // abort completes. Idle-follow briefly so that content isn't stranded
+      // behind the input; a user who scrolled away stays put via the sticky
+      // check.
+      chase.kickUntil(POST_STOP_SETTLE_WINDOW)
     }
   }, [isStreaming])
 
-  return { ref: callbackRef, detach }
+  return { ref: callbackRef }
 }
diff --git a/apps/sim/lib/core/utils/smooth-bottom-chase.ts b/apps/sim/lib/core/utils/smooth-bottom-chase.ts
index ad31140bd96..0b71687fc32 100644
--- a/apps/sim/lib/core/utils/smooth-bottom-chase.ts
+++ b/apps/sim/lib/core/utils/smooth-bottom-chase.ts
@@ -26,6 +26,13 @@ export interface SmoothBottomChaseHandle {
   isActive: () => boolean
   /** Start the loop if parked. Call after content growth. */
   kick: () => void
+  /**
+   * Keep the loop alive for `durationMs` even while the gap is at rest,
+   * re-checking every frame. For growth that lands with no observable trigger
+   * — content mounting just after a stream's observers tear down (a stop's
+   * stopped-row/actions). Repeat calls extend the deadline; one loop only.
+   */
+  kickUntil: (durationMs: number) => void
   cancel: () => void
 }
 
@@ -47,11 +54,13 @@ export function createSmoothBottomChase(
 ): SmoothBottomChaseHandle {
   let raf: number | null = null
   let lastTop: number | null = null
+  let deadline = 0
 
   const park = () => {
     if (raf !== null) cancelAnimationFrame(raf)
     raf = null
     lastTop = null
+    deadline = 0
   }
 
   const step = () => {
@@ -71,7 +80,14 @@ export function createSmoothBottomChase(
     }
     const gap = target.getBottomTop() - top
     if (gap <= CHASE_REST_GAP) {
-      park()
+      // Within a kickUntil deadline, idle at rest instead of parking so
+      // trigger-less growth inside the window is still chased.
+      if (performance.now() >= deadline) {
+        park()
+        return
+      }
+      lastTop = top
+      raf = requestAnimationFrame(step)
       return
     }
     target.setTop(top + Math.max(1, gap * SMOOTH_CHASE_RATE))
@@ -97,6 +113,10 @@ export function createSmoothBottomChase(
   return {
     isActive: () => raf !== null,
     kick: start,
+    kickUntil: (durationMs: number) => {
+      deadline = Math.max(deadline, performance.now() + durationMs)
+      start()
+    },
     cancel: park,
   }
 }

From 4bb8fbd56c58b896e69185f33dd223e756b2745e Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 11:18:17 -0700
Subject: [PATCH 06/12] fix(mothership): single stopped tail region and drain
 cleanup

---
 .../components/message-content/message-content.tsx | 14 +++++++++-----
 .../components/mothership-chat/mothership-chat.tsx |  5 ++++-
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
index 846bfea31e5..4be3768d760 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
@@ -983,17 +983,21 @@ function MessageContentInner({
           </div>
         </div>
       ) : (
-        // Stopped row and actions take the slot's place in the SAME render and
-        // at the SAME extent (TAIL_REGION_CLASSES), so the swap is height-
-        // neutral by construction — no reflow for the pinned scroller to absorb.
+        // The settled tail takes the slot's place in the SAME render and at the
+        // SAME extent (TAIL_REGION_CLASSES), so the swap is height-neutral by
+        // construction — no reflow for the pinned scroller to absorb. A stopped
+        // turn shares the ONE region (status left, actions right); stacking two
+        // regions would double the tail and break neutrality.
         <>
-          {lastSegment?.type === 'stopped' && (
+          {lastSegment?.type === 'stopped' ? (
             <div className={cn(TAIL_REGION_CLASSES, 'gap-[8px]')}>
               <CircleStop className='size-[16px] flex-shrink-0 text-[var(--text-icon)]' />
               <span className='text-[14px] text-[var(--text-body)]'>Stopped by user</span>
+              {actions && <div className='ml-auto'>{actions}</div>}
             </div>
+          ) : (
+            actions && <div className={TAIL_REGION_CLASSES}>{actions}</div>
           )}
-          {actions && <div className={TAIL_REGION_CLASSES}>{actions}</div>}
         </>
       )}
     </div>
diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
index 1273a58e701..6c8bae6e805 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
@@ -306,6 +306,7 @@ export function MothershipChat({
   const scrollerPaddingRef = useRef<{ top: number; bottom: number } | null>(null)
   const sizerFloorAppliedRef = useRef(0)
   const floorDrainRafRef = useRef(0)
+  useEffect(() => () => cancelAnimationFrame(floorDrainRafRef.current), [])
 
   /**
    * Sizer floor while streaming: `scrollHeight` must never dip below the
@@ -340,12 +341,14 @@ export function MothershipChat({
     if (!floorActive) {
       if (sizerFloorAppliedRef.current === 0) return
       scrollerPaddingRef.current = null
-      const pinned = el.scrollHeight - el.scrollTop - el.clientHeight <= 2
       cancelAnimationFrame(floorDrainRafRef.current)
       const drain = () => {
         const target = virtualizer.getTotalSize()
         const current = sizerFloorAppliedRef.current
         if (current === 0) return
+        // Re-checked per frame: a user scrolling away mid-drain makes the
+        // remaining shrink invisible, so finish instantly instead of clamping.
+        const pinned = el.scrollHeight - el.scrollTop - el.clientHeight <= 2
         const next = Math.floor(current - Math.max(1, (current - target) * SMOOTH_CHASE_RATE))
         if (!pinned || next - target <= 1) {
           sizerFloorAppliedRef.current = 0

From f7a94daac3153dcb5b8741bb4b01ee3b53436b2d Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 11:25:10 -0700
Subject: [PATCH 07/12] fix(mothership): clamp-aware chase interrupt so the
 floor drain can't park the settle follow

---
 .../sim/lib/core/utils/smooth-bottom-chase.ts | 22 ++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/apps/sim/lib/core/utils/smooth-bottom-chase.ts b/apps/sim/lib/core/utils/smooth-bottom-chase.ts
index 0b71687fc32..ffe8011c298 100644
--- a/apps/sim/lib/core/utils/smooth-bottom-chase.ts
+++ b/apps/sim/lib/core/utils/smooth-bottom-chase.ts
@@ -44,9 +44,12 @@ export interface SmoothBottomChaseHandle {
  *
  * Self-interrupting: chase writes only ever move the offset down, and content
  * growth leaves it where the last write put it — so an offset that moved UP
- * since the last write can only be a user scrolling away, and the loop parks
- * instead of fighting them. `shouldContinue` layers any caller-owned stickiness
- * on top (checked every frame).
+ * since the last write, MORE than the bottom itself moved up, can only be a
+ * user scrolling away, and the loop parks instead of fighting them. (A
+ * content-shrink clamp moves the offset and the bottom together — e.g. the
+ * transcript's floor drain — and must not read as a user scroll.)
+ * `shouldContinue` layers any caller-owned stickiness on top (checked every
+ * frame).
  */
 export function createSmoothBottomChase(
   target: SmoothBottomChaseTarget,
@@ -54,12 +57,14 @@ export function createSmoothBottomChase(
 ): SmoothBottomChaseHandle {
   let raf: number | null = null
   let lastTop: number | null = null
+  let lastBottomTop: number | null = null
   let deadline = 0
 
   const park = () => {
     if (raf !== null) cancelAnimationFrame(raf)
     raf = null
     lastTop = null
+    lastBottomTop = null
     deadline = 0
   }
 
@@ -74,11 +79,17 @@ export function createSmoothBottomChase(
       return
     }
     const top = target.getTop()
-    if (lastTop !== null && top < lastTop - 1) {
+    const bottomTop = target.getBottomTop()
+    if (
+      lastTop !== null &&
+      lastBottomTop !== null &&
+      lastTop - top > lastBottomTop - bottomTop + 1
+    ) {
       park()
       return
     }
-    const gap = target.getBottomTop() - top
+    lastBottomTop = bottomTop
+    const gap = bottomTop - top
     if (gap <= CHASE_REST_GAP) {
       // Within a kickUntil deadline, idle at rest instead of parking so
       // trigger-less growth inside the window is still chased.
@@ -107,6 +118,7 @@ export function createSmoothBottomChase(
   const start = () => {
     if (raf !== null) return
     lastTop = target.getTop()
+    lastBottomTop = target.getBottomTop()
     raf = requestAnimationFrame(step)
   }
 

From fb10473b4f9f3c28812edd8bf28f620b63778a53 Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 11:31:46 -0700
Subject: [PATCH 08/12] fix(mothership): park the chase only on real upward top
 moves, not growth

---
 apps/sim/lib/core/utils/smooth-bottom-chase.ts | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/apps/sim/lib/core/utils/smooth-bottom-chase.ts b/apps/sim/lib/core/utils/smooth-bottom-chase.ts
index ffe8011c298..e2b928e8f24 100644
--- a/apps/sim/lib/core/utils/smooth-bottom-chase.ts
+++ b/apps/sim/lib/core/utils/smooth-bottom-chase.ts
@@ -80,11 +80,12 @@ export function createSmoothBottomChase(
     }
     const top = target.getTop()
     const bottomTop = target.getBottomTop()
-    if (
-      lastTop !== null &&
-      lastBottomTop !== null &&
-      lastTop - top > lastBottomTop - bottomTop + 1
-    ) {
+    // A user scroll is an ACTUAL upward top move (first clause — growth alone
+    // must not trip this) that exceeds any upward move of the bottom itself
+    // (second clause — a shrink clamp moves both together).
+    const topDrop = lastTop === null ? 0 : lastTop - top
+    const bottomDrop = lastBottomTop === null ? 0 : lastBottomTop - bottomTop
+    if (topDrop > 1 && topDrop > bottomDrop + 1) {
       park()
       return
     }

From 7b6c86f2ff8f5efce73b5a69d062afe6a959531d Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 11:48:09 -0700
Subject: [PATCH 09/12] improvement(mothership): stack the stopped status above
 the actions row

---
 .../components/message-content/message-content.tsx    | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
index 4be3768d760..75d45c79db1 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
@@ -986,18 +986,17 @@ function MessageContentInner({
         // The settled tail takes the slot's place in the SAME render and at the
         // SAME extent (TAIL_REGION_CLASSES), so the swap is height-neutral by
         // construction — no reflow for the pinned scroller to absorb. A stopped
-        // turn shares the ONE region (status left, actions right); stacking two
-        // regions would double the tail and break neutrality.
+        // turn stacks a second region (status row above the actions); that +46px
+        // is deliberate — the teardown's eased follow glides it into view, and
+        // the stacked layout beats a combined status/actions row visually.
         <>
-          {lastSegment?.type === 'stopped' ? (
+          {lastSegment?.type === 'stopped' && (
             <div className={cn(TAIL_REGION_CLASSES, 'gap-[8px]')}>
               <CircleStop className='size-[16px] flex-shrink-0 text-[var(--text-icon)]' />
               <span className='text-[14px] text-[var(--text-body)]'>Stopped by user</span>
-              {actions && <div className='ml-auto'>{actions}</div>}
             </div>
-          ) : (
-            actions && <div className={TAIL_REGION_CLASSES}>{actions}</div>
           )}
+          {actions && <div className={TAIL_REGION_CLASSES}>{actions}</div>}
         </>
       )}
     </div>

From ecacda731f50e4b07f23da0e3b812e2bb12c4ee0 Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 11:51:08 -0700
Subject: [PATCH 10/12] improvement(mothership): compact stopped-turn tail with
 the original 10px rhythm

---
 .../message-content/message-content.tsx       | 37 ++++++++++---------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
index 75d45c79db1..21fb1a5a20d 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx
@@ -31,10 +31,11 @@ const FILE_SUBAGENT_ID = 'file'
 /** Quiet period before the shimmer takes the slot back from streamed output. */
 const STREAM_IDLE_DELAY_MS = 1_500
 /**
- * The one vertical extent (10px gap + 36px row) every tail-region occupant —
- * shimmer slot, actions row, stopped row — must share. The settle swap is only
- * jump-free because these are equal; changing one side without the others
- * reintroduces a scroll clamp at end of turn.
+ * The vertical extent (10px gap + 36px row) shared by the shimmer slot and the
+ * actions row that replaces it at settle. The swap is only jump-free because
+ * these are equal; changing one side without the other reintroduces a scroll
+ * clamp at end of turn. (A stopped turn's stacked rows are exempt — their
+ * extra height is glided-in growth, not a swap.)
  */
 const TAIL_REGION_CLASSES = 'mt-[10px] flex h-[36px] items-center'
 
@@ -982,22 +983,22 @@ function MessageContentInner({
             <PendingTagIndicator label={thinkingLabel ?? 'Thinking…'} />
           </div>
         </div>
-      ) : (
-        // The settled tail takes the slot's place in the SAME render and at the
-        // SAME extent (TAIL_REGION_CLASSES), so the swap is height-neutral by
-        // construction — no reflow for the pinned scroller to absorb. A stopped
-        // turn stacks a second region (status row above the actions); that +46px
-        // is deliberate — the teardown's eased follow glides it into view, and
-        // the stacked layout beats a combined status/actions row visually.
+      ) : // The settled tail takes the slot's place in the SAME render and at the
+      // SAME extent (TAIL_REGION_CLASSES), so the swap is height-neutral by
+      // construction — no reflow for the pinned scroller to absorb. A stopped
+      // turn instead stacks compact natural rows (10px gaps, no 36px boxes):
+      // its extra height is glided-in growth either way, so only the
+      // shimmer-swap occupant needs the fixed extent.
+      lastSegment?.type === 'stopped' ? (
         <>
-          {lastSegment?.type === 'stopped' && (
-            <div className={cn(TAIL_REGION_CLASSES, 'gap-[8px]')}>
-              <CircleStop className='size-[16px] flex-shrink-0 text-[var(--text-icon)]' />
-              <span className='text-[14px] text-[var(--text-body)]'>Stopped by user</span>
-            </div>
-          )}
-          {actions && <div className={TAIL_REGION_CLASSES}>{actions}</div>}
+          <div className='mt-[10px] flex items-center gap-[8px]'>
+            <CircleStop className='size-[16px] flex-shrink-0 text-[var(--text-icon)]' />
+            <span className='text-[14px] text-[var(--text-body)]'>Stopped by user</span>
+          </div>
+          {actions && <div className='mt-[10px]'>{actions}</div>}
         </>
+      ) : (
+        actions && <div className={TAIL_REGION_CLASSES}>{actions}</div>
       )}
     </div>
   )

From 4757422ea80f054b038c7d764c825901d2f43481 Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 12:12:32 -0700
Subject: [PATCH 11/12] fix(mothership): single drain cadence and a
 settle-window gesture kill switch

---
 .../components/mothership-chat/mothership-chat.tsx | 14 +++++++++++---
 apps/sim/hooks/use-auto-scroll.ts                  | 14 ++++++++++++++
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
index 6c8bae6e805..c0041ccacf2 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
@@ -340,18 +340,25 @@ export function MothershipChat({
     if (!sizer || !el) return
     if (!floorActive) {
       if (sizerFloorAppliedRef.current === 0) return
+      // A drain already in flight keeps its own rAF cadence — settle-burst
+      // commits re-enter this branch and must not add extra steps in layout,
+      // which would accelerate the release past the eased rate.
+      if (floorDrainRafRef.current !== 0) return
       scrollerPaddingRef.current = null
-      cancelAnimationFrame(floorDrainRafRef.current)
       const drain = () => {
         const target = virtualizer.getTotalSize()
         const current = sizerFloorAppliedRef.current
-        if (current === 0) return
+        if (current === 0) {
+          floorDrainRafRef.current = 0
+          return
+        }
         // Re-checked per frame: a user scrolling away mid-drain makes the
         // remaining shrink invisible, so finish instantly instead of clamping.
         const pinned = el.scrollHeight - el.scrollTop - el.clientHeight <= 2
         const next = Math.floor(current - Math.max(1, (current - target) * SMOOTH_CHASE_RATE))
         if (!pinned || next - target <= 1) {
           sizerFloorAppliedRef.current = 0
+          floorDrainRafRef.current = 0
           sizer.style.minHeight = ''
           return
         }
@@ -359,10 +366,11 @@ export function MothershipChat({
         sizer.style.minHeight = `${next}px`
         floorDrainRafRef.current = requestAnimationFrame(drain)
       }
-      drain()
+      floorDrainRafRef.current = requestAnimationFrame(drain)
       return
     }
     cancelAnimationFrame(floorDrainRafRef.current)
+    floorDrainRafRef.current = 0
     if (!scrollerPaddingRef.current) {
       const style = getComputedStyle(el)
       scrollerPaddingRef.current = {
diff --git a/apps/sim/hooks/use-auto-scroll.ts b/apps/sim/hooks/use-auto-scroll.ts
index c5ae57f9a28..a14aa532eda 100644
--- a/apps/sim/hooks/use-auto-scroll.ts
+++ b/apps/sim/hooks/use-auto-scroll.ts
@@ -214,6 +214,20 @@ export function useAutoScroll(isStreaming: boolean) {
       // behind the input; a user who scrolled away stays put via the sticky
       // check.
       chase.kickUntil(POST_STOP_SETTLE_WINDOW)
+      // The main gesture listeners are gone, so give the settle window its own
+      // kill switch: the chase's clamp-aware interrupt catches wheel-scale
+      // moves, but a slow trackpad glide during a concurrent shrink could slip
+      // under it for up to the window's duration.
+      const cancelOnGesture = (event: Event) => {
+        if (event.type === 'wheel' && (event as WheelEvent).deltaY >= 0) return
+        chase.cancel()
+      }
+      el.addEventListener('wheel', cancelOnGesture, { passive: true })
+      el.addEventListener('touchmove', cancelOnGesture, { passive: true })
+      setTimeout(() => {
+        el.removeEventListener('wheel', cancelOnGesture)
+        el.removeEventListener('touchmove', cancelOnGesture)
+      }, POST_STOP_SETTLE_WINDOW + 100)
     }
   }, [isStreaming])
 

From 243cd3708884dabe5b1aa362c87ddfe5154bab4c Mon Sep 17 00:00:00 2001
From: Theodore Li <theo@sim.ai>
Date: Wed, 22 Jul 2026 12:24:36 -0700
Subject: [PATCH 12/12] fix(mothership): debt-aware drain fast-path and
 settle-window handle retention

---
 .../mothership-chat/mothership-chat.tsx       | 13 ++++++-----
 apps/sim/hooks/use-auto-scroll.ts             | 22 ++++++++++++++++++-
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
index c0041ccacf2..dcac9da0b56 100644
--- a/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx
@@ -352,16 +352,19 @@ export function MothershipChat({
           floorDrainRafRef.current = 0
           return
         }
-        // Re-checked per frame: a user scrolling away mid-drain makes the
-        // remaining shrink invisible, so finish instantly instead of clamping.
-        const pinned = el.scrollHeight - el.scrollTop - el.clientHeight <= 2
-        const next = Math.floor(current - Math.max(1, (current - target) * SMOOTH_CHASE_RATE))
-        if (!pinned || next - target <= 1) {
+        // Instant-clear only when the whole remaining debt sits BELOW the
+        // viewport (debt ≤ distance-from-bottom) — then the shrink is
+        // invisible. A merely-unpinned viewport with debt larger than its
+        // slack would still clamp, so it keeps the eased drain instead.
+        const distance = el.scrollHeight - el.scrollTop - el.clientHeight
+        const debt = current - target
+        if (debt <= 1 || debt <= distance) {
           sizerFloorAppliedRef.current = 0
           floorDrainRafRef.current = 0
           sizer.style.minHeight = ''
           return
         }
+        const next = Math.floor(current - Math.max(1, debt * SMOOTH_CHASE_RATE))
         sizerFloorAppliedRef.current = next
         sizer.style.minHeight = `${next}px`
         floorDrainRafRef.current = requestAnimationFrame(drain)
diff --git a/apps/sim/hooks/use-auto-scroll.ts b/apps/sim/hooks/use-auto-scroll.ts
index a14aa532eda..d20a68c10f1 100644
--- a/apps/sim/hooks/use-auto-scroll.ts
+++ b/apps/sim/hooks/use-auto-scroll.ts
@@ -66,10 +66,21 @@ export function useAutoScroll(isStreaming: boolean) {
     containerRef.current = el
   }, [])
 
+  /**
+   * Cancels the previous teardown's settle window (chase, temp listeners,
+   * removal timer). Invoked when a new stream starts — a stop-then-resend must
+   * not leave the old settle chase writing beside the new stream's chase — and
+   * on unmount.
+   */
+  const settleCleanupRef = useRef<(() => void) | null>(null)
+  useEffect(() => () => settleCleanupRef.current?.(), [])
+
   useEffect(() => {
     if (!isStreaming) return
     const el = containerRef.current
     if (!el) return
+    settleCleanupRef.current?.()
+    settleCleanupRef.current = null
 
     /**
      * Eased bottom-chase shared by the mutation observer and the seed below —
@@ -224,10 +235,19 @@ export function useAutoScroll(isStreaming: boolean) {
       }
       el.addEventListener('wheel', cancelOnGesture, { passive: true })
       el.addEventListener('touchmove', cancelOnGesture, { passive: true })
-      setTimeout(() => {
+      const removeGestureGuard = () => {
         el.removeEventListener('wheel', cancelOnGesture)
         el.removeEventListener('touchmove', cancelOnGesture)
+      }
+      const guardTimeout = setTimeout(() => {
+        removeGestureGuard()
+        settleCleanupRef.current = null
       }, POST_STOP_SETTLE_WINDOW + 100)
+      settleCleanupRef.current = () => {
+        chase.cancel()
+        clearTimeout(guardTimeout)
+        removeGestureGuard()
+      }
     }
   }, [isStreaming])