diff --git a/.changeset/animate-tool-card-reveals.md b/.changeset/animate-tool-card-reveals.md
new file mode 100644
index 00000000000..a273d7ae45e
--- /dev/null
+++ b/.changeset/animate-tool-card-reveals.md
@@ -0,0 +1,5 @@
+---
+"kilo-code": patch
+---
+
+Animate tool-call and reasoning details when expanding and collapsing.
diff --git a/packages/kilo-ui/src/components/basic-tool.css b/packages/kilo-ui/src/components/basic-tool.css
index 0111b6381a9..49ed771af57 100644
--- a/packages/kilo-ui/src/components/basic-tool.css
+++ b/packages/kilo-ui/src/components/basic-tool.css
@@ -129,19 +129,62 @@ html[data-theme="kilo-vscode"] [data-component="tool-trigger"] {
   }
 }
 
+@keyframes tool-card-down {
+  from {
+    grid-template-rows: 0fr;
+    opacity: 0;
+  }
+
+  to {
+    grid-template-rows: 1fr;
+    opacity: 1;
+  }
+}
+
+@keyframes tool-card-up {
+  from {
+    grid-template-rows: 1fr;
+    opacity: 1;
+  }
+
+  to {
+    grid-template-rows: 0fr;
+    opacity: 0;
+  }
+}
+
 /* Card styling for tool calls in the VS Code sidebar theme */
 html[data-theme="kilo-vscode"] [data-component="tool-part-wrapper"][data-part-type="tool"] {
   border-radius: 0;
   border: 0;
   overflow: visible;
 
-  /* Header trigger — add bottom border when the collapsible is open */
   [data-component="collapsible"].tool-collapsible {
     gap: 0;
     border-radius: 0;
 
-    &:has([data-slot="collapsible-trigger"][aria-expanded="true"]) {
-      gap: 6px;
+    > [data-slot="collapsible-content"] {
+      display: grid;
+      overflow: visible;
+      clip-path: inset(0 -6px);
+
+      > * {
+        min-height: 0;
+      }
+    }
+
+    > [data-slot="collapsible-content"][data-expanded] {
+      animation: tool-card-down 220ms cubic-bezier(0.23, 1, 0.32, 1);
+    }
+
+    > [data-slot="collapsible-content"][data-closed] {
+      animation: tool-card-up 160ms cubic-bezier(0.77, 0, 0.175, 1);
+    }
+
+    [data-slot="basic-tool-details"]::before {
+      display: block;
+      height: 6px;
+      content: "";
     }
 
     [data-slot="collapsible-trigger"] {
@@ -409,3 +452,12 @@ html[data-theme="kilo-vscode"] [data-component="tool-part-wrapper"][data-part-ty
     }
   }
 }
+
+@media (prefers-reduced-motion: reduce) {
+  html[data-theme="kilo-vscode"] [data-component="tool-part-wrapper"][data-part-type="tool"] {
+    [data-component="collapsible"].tool-collapsible > [data-slot="collapsible-content"][data-expanded],
+    [data-component="collapsible"].tool-collapsible > [data-slot="collapsible-content"][data-closed] {
+      animation-duration: 0.01ms;
+    }
+  }
+}
diff --git a/packages/kilo-ui/src/components/basic-tool.tsx b/packages/kilo-ui/src/components/basic-tool.tsx
index 0f4234ad1a4..7ba072c7c44 100644
--- a/packages/kilo-ui/src/components/basic-tool.tsx
+++ b/packages/kilo-ui/src/components/basic-tool.tsx
@@ -20,14 +20,16 @@ export function initialOpen(props: OpenProps) {
 export function BasicTool(props: BasicToolProps) {
   const key = () => toolOpenKey(props)
   const initial = () => initialOpen(props)
+  const change = (open: boolean) => {
+    writeToolOpen(key(), open)
+    props.onOpenChange?.(open)
+  }
+  if (!("children" in props)) {
+    return <Base {...props} defaultOpen={initial()} retainDetails={props.defer} onOpenChange={change} />
+  }
   return (
-    <Base
-      {...props}
-      defaultOpen={initial()}
-      onOpenChange={(open) => {
-        writeToolOpen(key(), open)
-        props.onOpenChange?.(open)
-      }}
-    />
+    <Base {...props} defaultOpen={initial()} retainDetails={props.defer} onOpenChange={change}>
+      <div data-slot="basic-tool-details">{props.children}</div>
+    </Base>
   )
 }
diff --git a/packages/kilo-ui/src/components/message-part.css b/packages/kilo-ui/src/components/message-part.css
index ffb4ae84ec4..5a3fd732da0 100644
--- a/packages/kilo-ui/src/components/message-part.css
+++ b/packages/kilo-ui/src/components/message-part.css
@@ -477,6 +477,30 @@ html[data-theme="kilo-vscode"] [data-component="todos"] {
   padding: 8px;
 }
 
+@keyframes reasoning-card-down {
+  from {
+    grid-template-rows: 0fr;
+    opacity: 0;
+  }
+
+  to {
+    grid-template-rows: 1fr;
+    opacity: 1;
+  }
+}
+
+@keyframes reasoning-card-up {
+  from {
+    grid-template-rows: 1fr;
+    opacity: 1;
+  }
+
+  to {
+    grid-template-rows: 0fr;
+    opacity: 0;
+  }
+}
+
 /* Reasoning block: visually distinct from normal agent output.
    Reasoning stays open unless the user explicitly collapses it. */
 [data-component="reasoning-part"] {
@@ -550,22 +574,21 @@ html[data-theme="kilo-vscode"] [data-component="todos"] {
     }
   }
 
-  /* Collapse/expand animation via Kobalte's CSS variable.
-     Uses grid trick: the outer wrapper transitions grid-template-rows
-     between 0fr (collapsed) and 1fr (expanded) so the content smoothly
-     collapses without needing to know the pixel height up front. */
   [data-slot="collapsible-content"] {
     display: grid;
-    grid-template-rows: 0fr;
-    transition: grid-template-rows 250ms ease-out;
     overflow: hidden;
 
     > * {
+      min-height: 0;
       overflow: hidden;
     }
 
     &[data-expanded] {
-      grid-template-rows: 1fr;
+      animation: reasoning-card-down 220ms cubic-bezier(0.23, 1, 0.32, 1);
+    }
+
+    &[data-closed] {
+      animation: reasoning-card-up 160ms cubic-bezier(0.77, 0, 0.175, 1);
     }
   }
 
@@ -598,10 +621,6 @@ html[data-theme="kilo-vscode"] [data-component="reasoning-part"] {
   [data-component="collapsible"].tool-collapsible {
     gap: 0;
     border-radius: 0;
-
-    &:has([data-slot="collapsible-trigger"][aria-expanded="true"]) {
-      gap: 6px;
-    }
   }
 
   [data-slot="collapsible-trigger"] {
@@ -667,6 +686,12 @@ html[data-theme="kilo-vscode"] [data-component="reasoning-part"] {
     width: calc(100% + 12px);
   }
 
+  [data-slot="reasoning-details"]::before {
+    display: block;
+    height: 6px;
+    content: "";
+  }
+
   [data-slot="reasoning-content"] {
     padding: 8px 12px 10px;
     border: 0;
@@ -712,3 +737,10 @@ html[data-theme="kilo-vscode"] [data-component="reasoning-part"] {
     line-height: var(--line-height-large);
   }
 }
+
+@media (prefers-reduced-motion: reduce) {
+  [data-component="reasoning-part"] [data-slot="collapsible-content"][data-expanded],
+  [data-component="reasoning-part"] [data-slot="collapsible-content"][data-closed] {
+    animation-duration: 0.01ms;
+  }
+}
diff --git a/packages/kilo-ui/src/components/message-part.tsx b/packages/kilo-ui/src/components/message-part.tsx
index d8a448ed0ed..4fb2aab53bc 100644
--- a/packages/kilo-ui/src/components/message-part.tsx
+++ b/packages/kilo-ui/src/components/message-part.tsx
@@ -1591,8 +1591,10 @@ PART_MAPPING["reasoning"] = function ReasoningPartDisplay(props: MessagePartProp
             <Collapsible.Arrow />
           </Collapsible.Trigger>
           <Collapsible.Content>
-            <div data-slot="reasoning-content" ref={ref} onScroll={onScroll} onWheel={onWheel}>
-              <Markdown text={view().body} cacheKey={id} streaming={!done()} />
+            <div data-slot="reasoning-details">
+              <div data-slot="reasoning-content" ref={ref} onScroll={onScroll} onWheel={onWheel}>
+                <Markdown text={view().body} cacheKey={id} streaming={!done()} />
+              </div>
             </div>
           </Collapsible.Content>
         </Collapsible>
diff --git a/packages/ui/src/components/basic-tool.tsx b/packages/ui/src/components/basic-tool.tsx
index 3dd1f37836f..9e713a12d64 100644
--- a/packages/ui/src/components/basic-tool.tsx
+++ b/packages/ui/src/components/basic-tool.tsx
@@ -31,6 +31,7 @@ export interface BasicToolProps {
   defaultOpen?: boolean
   forceOpen?: boolean
   defer?: boolean
+  retainDetails?: boolean // kilocode_change
   hasDetails?: boolean // kilocode_change
   locked?: boolean
   animated?: boolean
@@ -125,7 +126,7 @@ export function BasicTool(props: BasicToolProps) {
         if (!props.defer) return
         if (!value) {
           cancel()
-          setState("ready", false)
+          if (!props.retainDetails) setState("ready", false) // kilocode_change
           return
         }
 
@@ -175,6 +176,14 @@ export function BasicTool(props: BasicToolProps) {
     props.onOpenChange?.(value) // kilocode_change
   }
 
+  // kilocode_change start
+  const end = (event: AnimationEvent) => {
+    if (event.target !== event.currentTarget) return
+    if (!props.retainDetails || open()) return
+    setState("ready", false)
+  }
+  // kilocode_change end
+
   const trigger = () => (
     <div
       data-component="tool-trigger"
@@ -299,7 +308,7 @@ export function BasicTool(props: BasicToolProps) {
       </Show>
       {/* kilocode_change start */}
       <Show when={!props.animated && (hasChildren() || hasDetails()) && !props.hideDetails}>
-        <Collapsible.Content>
+        <Collapsible.Content onAnimationEnd={end}>
           <Show when={!props.defer || ready()}>{props.children}</Show>
         </Collapsible.Content>
       </Show>