feat: show human playback markers on timeline

Resolves #105

js/src/components/ui/avatar.tsx

@@ -8,14 +8,14 @@ function Avatar({
   size = "default",
   ...props
 }: React.ComponentProps<typeof AvatarPrimitive.Root> & {
-  size?: "default" | "sm" | "lg"
+  size?: "default" | "xs" | "sm" | "lg"
 }) {
   return (
     <AvatarPrimitive.Root
       data-slot="avatar"
       data-size={size}
       className={cn(
-        "size-8 rounded-full after:rounded-full data-[size=lg]:size-10 data-[size=sm]:size-6 after:border-border group/avatar relative flex shrink-0 select-none after:absolute after:inset-0 after:border after:mix-blend-darken dark:after:mix-blend-lighten",
+        "size-8 rounded-full after:rounded-full data-[size=lg]:size-10 data-[size=sm]:size-6 data-[size=xs]:size-4 after:border-border group/avatar relative flex shrink-0 select-none after:absolute after:inset-0 after:border after:mix-blend-darken dark:after:mix-blend-lighten",
         className
       )}
       {...props}
@@ -47,7 +47,7 @@ function AvatarFallback({
     <AvatarPrimitive.Fallback
       data-slot="avatar-fallback"
       className={cn(
-        "bg-muted text-muted-foreground rounded-full flex size-full items-center justify-center text-sm group-data-[size=sm]/avatar:text-xs",
+        "bg-muted text-muted-foreground rounded-full flex size-full items-center justify-center text-sm group-data-[size=sm]/avatar:text-xs group-data-[size=xs]/avatar:text-[8px]",
         className
       )}
       {...props}
@@ -61,6 +61,7 @@ function AvatarBadge({ className, ...props }: React.ComponentProps<"span">) {
       data-slot="avatar-badge"
       className={cn(
         "bg-primary text-primary-foreground ring-background absolute right-0 bottom-0 z-10 inline-flex items-center justify-center rounded-full bg-blend-color ring-2 select-none",
+        "group-data-[size=xs]/avatar:size-1.5 group-data-[size=xs]/avatar:[&>svg]:hidden",
         "group-data-[size=sm]/avatar:size-2 group-data-[size=sm]/avatar:[&>svg]:hidden",
         "group-data-[size=default]/avatar:size-2.5 group-data-[size=default]/avatar:[&>svg]:size-2",
         "group-data-[size=lg]/avatar:size-3 group-data-[size=lg]/avatar:[&>svg]:size-2",
@@ -91,7 +92,7 @@ function AvatarGroupCount({
   return (
     <div
       data-slot="avatar-group-count"
-      className={cn("bg-muted text-muted-foreground size-8 rounded-full text-sm group-has-data-[size=lg]/avatar-group:size-10 group-has-data-[size=sm]/avatar-group:size-6 [&>svg]:size-4 group-has-data-[size=lg]/avatar-group:[&>svg]:size-5 group-has-data-[size=sm]/avatar-group:[&>svg]:size-3 ring-background relative flex shrink-0 items-center justify-center ring-2", className)}
+      className={cn("bg-muted text-muted-foreground size-8 rounded-full text-sm group-has-data-[size=lg]/avatar-group:size-10 group-has-data-[size=sm]/avatar-group:size-6 group-has-data-[size=xs]/avatar-group:size-4 group-has-data-[size=xs]/avatar-group:text-[8px] [&>svg]:size-4 group-has-data-[size=lg]/avatar-group:[&>svg]:size-5 group-has-data-[size=sm]/avatar-group:[&>svg]:size-3 ring-background relative flex shrink-0 items-center justify-center ring-2", className)}
       {...props}
     />
   )

js/src/features/particles/media-particle-view.tsx

@@ -98,7 +98,7 @@ export function MediaParticleView({
         />
 
         {audioSource && (
-          <div className="z-10 absolute bottom-10">
+          <div className="z-10 absolute bottom-20">
             <AudioLevelBars sourceNode={audioSource.sourceNode} />
           </div>
         )}

js/src/features/particles/playback-page-indicator.tsx

@@ -1,10 +1,20 @@
 import { cn } from "@/lib/utils";
+import { Avatar, AvatarFallback } from "@/components/ui/avatar";
+import {
+  Tooltip,
+  TooltipContent,
+  TooltipTrigger,
+} from "@/components/ui/tooltip";
+import type { HumanPresence } from "@/hooks/use-presence-positions";
+
+const MAX_VISIBLE_AVATARS = 3;
 
 interface PlaybackPageIndicatorProps {
   total: number;
   current: number;
   progress: number;
   onGoTo: (index: number) => void;
+  presenceBySegment?: Map<number, HumanPresence[]>;
 }
 
 export function PlaybackPageIndicator({
@@ -12,45 +22,79 @@ export function PlaybackPageIndicator({
   current,
   progress,
   onGoTo,
+  presenceBySegment,
 }: PlaybackPageIndicatorProps) {
   if (total === 0) return null;
 
   return (
-    <div className="flex w-full items-center gap-0.5 px-1">
+    <div className="flex w-full items-end gap-px leading-none">
-      {Array.from({ length: total }, (_, i) => (
+      {Array.from({ length: total }, (_, i) => {
-        <button
+        const presence = presenceBySegment?.get(i);
-          key={i}
+        return (
-          onClick={(e) => {
+          <div key={i} className="flex flex-1 flex-col items-stretch">
-            e.stopPropagation();
+            {/* Presence avatars above the track */}
-            onGoTo(i);
+            {presence && presence.length > 0 && (
-          }}
+              <SegmentPresenceAvatars presence={presence} />
-          className="group relative h-3 flex-1"
-        >
-          {/* Dim track */}
-          <div
-            className={cn(
-              "absolute inset-x-0 top-0 h-1 bg-white/30 transition-all",
-              "group-hover:h-1.5 group-hover:top-0.5",
             )}
-          />
+            <button
-          {/* Fill */}
+              onClick={(e) => {
-          <div
+                e.stopPropagation();
-            className={cn(
+                onGoTo(i);
-              "absolute left-0 top-0 h-1 bg-white/90 transition-all",
+              }}
-              "group-hover:h-1.5 group-hover:top-0.5",
+              className="group relative block h-3 w-full"
-            )}
+            >
-            style={{
+              {/* Dim track */}
-              width:
+              <div className="absolute inset-x-0 bottom-0 h-[3px] bg-white/30 transition-all group-hover:h-1.5" />
-                i < current
+              {/* Fill */}
-                  ? "100%"
+              <div
-                  : i === current
+                className="absolute left-0 bottom-0 h-[3px] bg-white/90 transition-all group-hover:h-1.5"
-                    ? `${progress * 100}%`
+                style={{
-                    : "0%",
+                  width:
-              transition: i === current ? "width 300ms linear" : "none",
+                    i < current
-            }}
+                      ? "100%"
-          />
+                      : i === current
-        </button>
+                        ? `${progress * 100}%`
+                        : "0%",
+                  transition: i === current ? "width 300ms linear" : "none",
+                }}
+              />
+            </button>
+          </div>
+        );
+      })}
+    </div>
+  );
+}
+
+function SegmentPresenceAvatars({
+  presence,
+}: {
+  presence: HumanPresence[];
+}) {
+  const visible = presence.slice(0, MAX_VISIBLE_AVATARS);
+  const overflow = presence.length - MAX_VISIBLE_AVATARS;
+
+  return (
+    <div className="flex items-center justify-center -space-x-1.5 pb-0.5">
+      {visible.map((human) => (
+        <Tooltip key={human.humanId}>
+          <TooltipTrigger asChild>
+            <Avatar size="xs" className="ring-1 ring-black/50">
+              <AvatarFallback>
+                {human.emailPrefix.slice(0, 2).toUpperCase()}
+              </AvatarFallback>
+            </Avatar>
+          </TooltipTrigger>
+          <TooltipContent side="top" className="text-xs">
+            {human.email}
+          </TooltipContent>
+        </Tooltip>
       ))}
+      {overflow > 0 && (
+        <span className="text-[10px] text-white/70 pl-1">
+          +{overflow}
+        </span>
+      )}
     </div>
   );
 }

js/src/features/particles/stream-view.tsx

@@ -20,6 +20,7 @@ import { WindowControls } from "@/components/window-controls";
 import { RelativeTimestamp } from "@/components/relative-timestamp";
 import { useStreamPlayback } from "@/hooks/use-stream-playback";
 import { usePrefetchAdjacentMedia } from "@/hooks/use-prefetch-adjacent-media";
+import { usePresencePositions } from "@/hooks/use-presence-positions";
 import { getInitials } from "@/lib/utils";
 
 function getParticleDisplayName(particle: Particle): string {
@@ -119,6 +120,15 @@ export function StreamView({ path, streamParticle }: StreamViewProps) {
 
   usePrefetchAdjacentMedia(children, currentIndex);
 
+  const authedUser = useAuthStore((s) => s.user);
+  const network = useNetwork(networkId);
+  const presenceBySegment = usePresencePositions(
+    streamParticle.playback_markers,
+    children,
+    network?.humans,
+    authedUser?.id,
+  );
+
   const [composeActive, setComposeActive] = useState(false);
   const [progress, setProgress] = useState(0);
 
@@ -268,16 +278,6 @@ export function StreamView({ path, streamParticle }: StreamViewProps) {
       {/* Bottom gradient safe zone — keeps captions & controls readable */}
       <div className="pointer-events-none absolute inset-x-0 bottom-0 z-[5] h-48 bg-gradient-to-t from-black/60 to-transparent" />
 
-      {/* Progress indicator */}
-      <div className="z-10 absolute left-0 right-0">
-        <PlaybackPageIndicator
-          total={children.length}
-          current={currentIndex}
-          progress={progress}
-          onGoTo={goTo}
-        />
-      </div>
-
       <div className="z-10 absolute left-0 right-0 mt-3">
         <TopBar networkId={networkId} particle={currentParticle} streamParticle={streamParticle} />
       </div>
@@ -303,9 +303,6 @@ export function StreamView({ path, streamParticle }: StreamViewProps) {
 
       {/* Bottom-left: metadata */}
       <div className="absolute bottom-0 left-0 z-10 flex items-center gap-2 px-2 pb-2 text-xs text-white/70">
-        {currentParticle && (
-          <SeenIndicator stream={streamParticle} currentParticle={currentParticle} networkId={networkId} />
-        )}
         {exitRemainingMs !== null && (
           <span className="rounded-full bg-black/30 px-2 py-1 backdrop-blur-sm">
             Closing in {Math.ceil(exitRemainingMs / 1000)}s
@@ -324,6 +321,17 @@ export function StreamView({ path, streamParticle }: StreamViewProps) {
           </span>
         </ControlsIndicator>
       </div>
+
+      {/* Progress indicator — bottom */}
+      <div className="z-10 absolute inset-x-0 bottom-0 mb-12">
+        <PlaybackPageIndicator
+          total={children.length}
+          current={currentIndex}
+          progress={progress}
+          onGoTo={goTo}
+          presenceBySegment={presenceBySegment}
+        />
+      </div>
     </div>
   );
 }
@@ -388,7 +396,7 @@ function TopBar({ networkId, particle, streamParticle }: { networkId: string; pa
                       </AvatarFallback>
                     </Avatar>
                   </TooltipTrigger>
-                  <TooltipContent>{human?.email_prefix ?? humanId}</TooltipContent>
+                  <TooltipContent>{human?.email ?? humanId}</TooltipContent>
                 </Tooltip>
               );
             })}
@@ -446,41 +454,3 @@ function ParticleBreadcrumbContent({ particle, networkId }: { particle: Particle
   )
 }
 
-// Shows a list of avatars of users who have seen the current particle, based on playback markers in the stream particle.
-const SeenIndicator = ({ stream, currentParticle, networkId }: { stream: Particle & { type: "stream" }, currentParticle: Particle, networkId: string }) => {
-  const authedUser = useAuthStore((s) => s.user);
-  const network = useNetwork(networkId);
-  const playbackMarkers = stream.playback_markers ?? {};
-
-  const seenUserIds = Object.entries(playbackMarkers)
-    .filter(([userId, timestamp]) => timestamp.getTime() >= currentParticle.created_at.getTime() && userId !== authedUser?.id)
-    .map(([userId, _]) => userId);
-
-  const seenHumans = seenUserIds
-    .map((userId) => network?.humans?.find((h) => h.id === userId))
-    .filter((h): h is NonNullable<typeof h> => !!h && h.id !== currentParticle.created_by_human_id);
-
-  if (seenHumans.length === 0) return null;
-
-  return (
-    <>
-      {"Seen by"}
-      <AvatarGroup>
-        {seenHumans.map((human) => (
-          <Tooltip key={human.id}>
-            <TooltipTrigger asChild>
-              <Avatar size="sm">
-                <AvatarFallback>
-                  {human.email_prefix.slice(0, 2)}
-                </AvatarFallback>
-              </Avatar>
-            </TooltipTrigger>
-            <TooltipContent>
-              <p>Seen by {human.email_prefix}</p>
-            </TooltipContent>
-          </Tooltip>
-        ))}
-      </AvatarGroup>
-    </>
-  );
-}

js/src/features/particles/transcript-overlay.tsx

@@ -75,7 +75,7 @@ export function TranscriptOverlay({
   return (
     <div className={centered
       ? "absolute inset-0 flex items-center justify-center px-6"
-      : "absolute bottom-6 left-0 right-0 flex justify-center px-6"
+      : "absolute bottom-17 left-0 right-0 flex justify-center px-6"
     }>
       <p className="rounded-lg px-5 py-3 text-2xl text-center max-w-lg">
         {activeChunk.map((word, i) => {

js/src/hooks/use-presence-positions.ts

@@ -0,0 +1,50 @@
+import { useMemo } from "react";
+import type { Human, Particle } from "@/api/types";
+
+export interface HumanPresence {
+  humanId: string;
+  email: string;
+  emailPrefix: string;
+}
+
+/**
+ * Maps playback markers to segment indices, returning which users are present at each particle.
+ */
+export function usePresencePositions(
+  playbackMarkers: Record<string, Date> | undefined,
+  children: Particle[],
+  networkHumans: Human[] | undefined,
+  currentUserId: string | undefined,
+): Map<number, HumanPresence[]> {
+  return useMemo(() => {
+    const result = new Map<number, HumanPresence[]>();
+    if (!playbackMarkers || !networkHumans || children.length === 0) return result;
+
+    for (const [userId, markerTimestamp] of Object.entries(playbackMarkers)) {
+      if (userId === currentUserId) continue;
+
+      const human = networkHumans.find((h) => h.id === userId);
+      if (!human) continue;
+
+      // Find the last particle whose created_at <= marker timestamp
+      let segmentIndex = -1;
+      for (let i = children.length - 1; i >= 0; i--) {
+        if (children[i].created_at.getTime() <= markerTimestamp.getTime()) {
+          segmentIndex = i;
+          break;
+        }
+      }
+      if (segmentIndex === -1) continue;
+
+      const existing = result.get(segmentIndex);
+      const presence: HumanPresence = { humanId: human.id, email: human.email, emailPrefix: human.email_prefix };
+      if (existing) {
+        existing.push(presence);
+      } else {
+        result.set(segmentIndex, [presence]);
+      }
+    }
+
+    return result;
+  }, [playbackMarkers, children, networkHumans, currentUserId]);
+}