feat(lens): show a now reading stage that types each trace's reasoning

ui/litellm-dashboard/src/app/globals.css

@@ -69,6 +69,16 @@
   --animate-slot-slide-in: slot-slide-in 150ms cubic-bezier(0, 0, 0.2, 1) both;
   --animate-trace-drawer-in: trace-drawer-in 200ms cubic-bezier(0.25, 1, 0.5, 1) both;
   --animate-trace-drawer-out: trace-drawer-out 200ms cubic-bezier(0.4, 0, 1, 1) both;
+  --animate-lens-shimmer: lens-shimmer 1.1s cubic-bezier(0.4, 0, 0.2, 1) infinite;
+
+  @keyframes lens-shimmer {
+    from {
+      transform: translateX(-100%);
+    }
+    to {
+      transform: translateX(250%);
+    }
+  }
 
   @keyframes trace-drawer-in {
     from {

ui/litellm-dashboard/src/components/lens/investigations/live/NowReading.tsx

@@ -0,0 +1,88 @@
+"use client";
+
+import { cn } from "@/lib/cva.config";
+
+import { durationLabel, outcome, shortVerdict } from "../../model/live";
+import { laneText, typedChars, type Lane } from "../../model/stage";
+import { ModelName } from "./LiveStrip";
+
+const RED = "text-[#e5484d]";
+
+function LaneRow({ lane, now, charMs }: { lane: Lane; now: number; charMs: number }) {
+  const { review } = lane;
+  const text = review ? laneText(review.reasoning) : "";
+  const typed = typedChars(lane, now, charMs);
+  const typing = !!review && typed < text.length;
+  const issue = review ? outcome(review) === "issue" : false;
+  return (
+    <li className="flex flex-col gap-1 rounded-lg bg-background/70 px-2.5 py-2 text-[12px] ring-1 ring-border/60 motion-safe:animate-in motion-safe:fade-in motion-safe:slide-in-from-top-1 motion-safe:duration-200">
+      <div className="flex items-center gap-2">
+        <span
+          aria-hidden="true"
+          className={cn(
+            "size-1.5 shrink-0 rounded-full",
+            !review ? "bg-foreground motion-safe:animate-pulse" : issue && !typing ? "bg-[#e5484d]" : "bg-foreground/50",
+          )}
+        />
+        <span className="truncate font-medium text-foreground">{lane.agent || "trace"}</span>
+        <span className="truncate font-mono text-[11px] text-muted-foreground">{lane.traceId.slice(0, 8)}</span>
+        <span className="ml-auto shrink-0 text-[11px] tabular-nums text-muted-foreground">
+          {review ? durationLabel(review.duration_ms) : `reading · ${durationLabel(Math.max(0, now - lane.startedAt))}`}
+        </span>
+      </div>
+      {!review ? (
+        <div aria-hidden="true" className="h-0.5 overflow-hidden rounded-full bg-muted">
+          <div className="h-full w-2/5 rounded-full bg-foreground/30 motion-safe:animate-lens-shimmer" />
+        </div>
+      ) : (
+        <>
+          <p className="min-h-[1.25rem] leading-relaxed text-muted-foreground">
+            {text.slice(0, typed)}
+            {typing && <span aria-hidden="true" className="ml-px inline-block h-3 w-px translate-y-0.5 bg-foreground" />}
+          </p>
+          {!typing && (
+            <p className={cn("truncate font-medium motion-safe:animate-in motion-safe:fade-in", issue ? RED : "text-foreground")}>
+              {shortVerdict(review)}
+            </p>
+          )}
+        </>
+      )}
+    </li>
+  );
+}
+
+export function NowReading({
+  model,
+  counter,
+  lanes,
+  now,
+  charMs,
+}: {
+  model: string;
+  counter: string;
+  lanes: readonly Lane[];
+  now: number;
+  charMs: number;
+}) {
+  return (
+    <section aria-label="Now reading" className="mb-3 flex flex-col gap-2 rounded-xl bg-muted p-2.5 ring-1 ring-border">
+      <header className="flex items-center justify-between gap-3 px-0.5">
+        <ModelName model={model} size="md" />
+        <span role="status" className="text-[11px] tabular-nums text-muted-foreground">
+          {counter}
+        </span>
+      </header>
+      {lanes.length ? (
+        <ol className="flex flex-col gap-1.5">
+          {lanes.map((lane) => (
+            <LaneRow key={lane.key} lane={lane} now={now} charMs={charMs} />
+          ))}
+        </ol>
+      ) : (
+        <div aria-hidden="true" className="h-0.5 overflow-hidden rounded-full bg-background/60">
+          <div className="h-full w-2/5 rounded-full bg-foreground/30 motion-safe:animate-lens-shimmer" />
+        </div>
+      )}
+    </section>
+  );
+}

ui/litellm-dashboard/src/components/lens/investigations/live/useStage.ts

@@ -0,0 +1,34 @@
+"use client";
+
+import { useEffect, useState } from "react";
+
+import type { InFlight } from "../../model/live";
+import { startStage, stepStage, type Stage } from "../../model/stage";
+import type { Review } from "../../model/types";
+
+const TICK_MS = 30;
+const CHAR_MS = 3;
+
+function prefersReducedMotion(): boolean {
+  return typeof window !== "undefined" && window.matchMedia?.("(prefers-reduced-motion: reduce)").matches === true;
+}
+
+export function useStage(
+  reviews: readonly Review[],
+  reading: readonly InFlight[],
+  running: boolean,
+  slots: number,
+): { stage: Stage; now: number; charMs: number } {
+  const [charMs] = useState(() => (prefersReducedMotion() ? 0 : CHAR_MS));
+  const [stage, setStage] = useState(() => startStage(reviews));
+  const [now, setNow] = useState(Date.now);
+  const next = stepStage(stage, { reading, reviews, now, slots, running, charMs });
+  if (next !== stage) setStage(next);
+  const busy = running || next.lanes.length > 0;
+  useEffect(() => {
+    if (!busy) return;
+    const timer = window.setInterval(() => setNow(Date.now()), TICK_MS);
+    return () => window.clearInterval(timer);
+  }, [busy]);
+  return { stage: next, now, charMs };
+}