diff --git a/packages/ui/src/components/chat/message/parts/ReasoningPart.tsx b/packages/ui/src/components/chat/message/parts/ReasoningPart.tsx
index baa40aae..0e74274b 100644
--- a/packages/ui/src/components/chat/message/parts/ReasoningPart.tsx
+++ b/packages/ui/src/components/chat/message/parts/ReasoningPart.tsx
@@ -83,6 +83,9 @@ const LiveDuration: React.FC<{ start: number; end?: number; active: boolean }> =
     return <>{formatDuration(start, end, now)}</>;
 };
 
+// TODO: Re-enable reasoning/justification header timestamps after hover UX is redesigned.
+const ENABLE_REASONING_HEADER_TIMESTAMPS = false;
+
 type ReasoningTimelineBlockProps = {
     text: string;
     variant: ReasoningVariant;
@@ -165,7 +168,7 @@ export const ReasoningTimelineBlock: React.FC<ReasoningTimelineBlockProps> = ({
                                 <span
                                     className={cn(
                                         'text-muted-foreground/80 transition-opacity duration-150',
-                                        !isMobile && endedTimestampText && 'group-hover/tool:opacity-0'
+                                        !isMobile && endedTimestampText && ENABLE_REASONING_HEADER_TIMESTAMPS && 'group-hover/tool:opacity-0'
                                     )}
                                 >
                                     <LiveDuration
@@ -174,7 +177,7 @@ export const ReasoningTimelineBlock: React.FC<ReasoningTimelineBlockProps> = ({
                                         active={typeof timeEnd !== 'number'}
                                     />
                                 </span>
-                                {!isMobile && endedTimestampText ? (
+                                {!isMobile && endedTimestampText && ENABLE_REASONING_HEADER_TIMESTAMPS ? (
                                     <span
                                         className={cn(
                                             'pointer-events-none absolute right-0 top-0 whitespace-nowrap text-muted-foreground/70 transition-opacity duration-150',
@@ -186,7 +189,7 @@ export const ReasoningTimelineBlock: React.FC<ReasoningTimelineBlockProps> = ({
                                 ) : null}
                             </span>
                         ) : null}
-                        {typeof timeStart !== 'number' && !isMobile && endedTimestampText ? (
+                        {typeof timeStart !== 'number' && !isMobile && endedTimestampText && ENABLE_REASONING_HEADER_TIMESTAMPS ? (
                             <span className="text-muted-foreground/70 flex-shrink-0 tabular-nums">
                                 {endedTimestampText}
                             </span>
diff --git a/packages/ui/src/components/chat/message/parts/ToolPart.tsx b/packages/ui/src/components/chat/message/parts/ToolPart.tsx
index 5d9b8356..3ca5d287 100644
--- a/packages/ui/src/components/chat/message/parts/ToolPart.tsx
+++ b/packages/ui/src/components/chat/message/parts/ToolPart.tsx
@@ -141,6 +141,9 @@ const LiveDuration: React.FC<{ start: number; end?: number; active: boolean }> =
     return <>{formatDuration(start, end, now)}</>;
 };
 
+// TODO: Re-enable tool header timestamp display after hover UX is redesigned.
+const ENABLE_TOOL_HEADER_TIMESTAMPS = false;
+
 const parseDiffStats = (metadata?: Record<string, unknown>): { added: number; removed: number } | null => {
     if (!metadata?.diff || typeof metadata.diff !== 'string') return null;
 
@@ -1823,7 +1826,7 @@ const ToolPart: React.FC<ToolPartProps> = ({
                             <span
                                 className={cn(
                                     'text-muted-foreground/80 transition-opacity duration-150',
-                                    !isMobile && endedTimestampText && 'group-hover/tool:opacity-0'
+                                    !isMobile && endedTimestampText && ENABLE_TOOL_HEADER_TIMESTAMPS && 'group-hover/tool:opacity-0'
                                 )}
                             >
                                 <LiveDuration
@@ -1832,7 +1835,7 @@ const ToolPart: React.FC<ToolPartProps> = ({
                                     active={Boolean(isActive && typeof effectiveTimeEnd !== 'number')}
                                 />
                             </span>
-                            {!isMobile && endedTimestampText ? (
+                            {!isMobile && endedTimestampText && ENABLE_TOOL_HEADER_TIMESTAMPS ? (
                                 <span
                                     className={cn(
                                         'pointer-events-none absolute right-0 top-0 whitespace-nowrap text-muted-foreground/70 transition-opacity duration-150',
@@ -1844,7 +1847,7 @@ const ToolPart: React.FC<ToolPartProps> = ({
                             ) : null}
                         </span>
                     ) : null}
-                    {typeof effectiveTimeStart !== 'number' && !isMobile && endedTimestampText ? (
+                    {typeof effectiveTimeStart !== 'number' && !isMobile && endedTimestampText && ENABLE_TOOL_HEADER_TIMESTAMPS ? (
                         <span className="ml-auto text-muted-foreground/70 flex-shrink-0 tabular-nums">
                             {endedTimestampText}
                         </span>