v1.12.2: live tok/s + ctx display next to status indicator

ChatThroughput renders inline beside StatusDot while streaming or
tool_running. Subscribes to existing usage frames via sessionEvents.
Hides when status drops to idle/error or data is older than 10s.

Addresses the 2026-05-21 spike's UX gap where slow streams looked
identical to dead streams — now there's a live token velocity readout
that immediately distinguishes the two.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/server/src/services/inference.ts

@@ -117,6 +117,7 @@ export interface InferenceFrame {
     | 'tool_call'
     | 'tool_result'
     | 'message_complete'
+    | 'usage'
     | 'messages_deleted'
     | 'session_renamed'
     | 'chat_renamed'
@@ -145,6 +146,7 @@ export interface InferenceFrame {
   tokens_used?: number | null;
   ctx_used?: number | null;
   ctx_max?: number | null;
+  completion_tokens?: number | null;
   started_at?: string | null;
   finished_at?: string | null;
   model?: string;
@@ -444,6 +446,7 @@ async function streamCompletion(
   messages: OpenAiMessage[],
   opts: StreamOptions,
   onDelta: (content: string) => void,
+  onUsage: ((prompt: number | null, completion: number | null) => void) | undefined,
   signal?: AbortSignal
 ): Promise<StreamResult> {
   const body: Record<string, unknown> = {
@@ -499,6 +502,7 @@ async function streamCompletion(
       if (typeof parsed.usage.completion_tokens === 'number') {
         completionTokens = parsed.usage.completion_tokens;
       }
+      onUsage?.(promptTokens, completionTokens);
     }
     // v1.11.3: removed dead `parsed.timings.n_ctx` read. llama-server's
     // streaming completion does NOT emit n_ctx in timings (verified
@@ -728,6 +732,34 @@ async function executeStreamPhase(
   ).filter((t) => webToolsEnabled || !WEB_TOOL_NAMES.has(t.function.name));
   const effectiveTemperature = agent?.temperature;
 
+  // v1.12.2: ctx_max lookup is cached after the first hit per model, so this
+  // is a Map probe in steady state. We capture nCtx once at the top of the
+  // stream so the throttled usage publish doesn't refetch each tick.
+  const mctxForStream = await modelContext.getModelContext(session.model);
+  const nCtxForStream = mctxForStream?.n_ctx ?? null;
+
+  // v1.12.2: throttle live usage publishes to ~500ms. The model can land
+  // dozens of usage frames per second; without a throttle the WS turns into
+  // a firehose for a few KB savings on each render.
+  const USAGE_THROTTLE_MS = 500;
+  let lastUsageAt = 0;
+  let pendingUsage: { p: number | null; c: number | null } | null = null;
+  let usageTimer: NodeJS.Timeout | null = null;
+  const flushUsage = () => {
+    if (!pendingUsage) return;
+    const { p, c } = pendingUsage;
+    pendingUsage = null;
+    lastUsageAt = Date.now();
+    ctx.publish(sessionId, {
+      type: 'usage',
+      message_id: assistantMessageId,
+      chat_id: chatId,
+      completion_tokens: c,
+      ctx_used: p,
+      ctx_max: nCtxForStream,
+    });
+  };
+
   try {
     return await streamCompletion(
       ctx,
@@ -745,6 +777,18 @@ async function executeStreamPhase(
         ctx.log.debug({ sessionId, delta }, 'inference delta');
         scheduleFlush();
       },
+      (prompt, completion) => {
+        pendingUsage = { p: prompt, c: completion };
+        const elapsed = Date.now() - lastUsageAt;
+        if (elapsed >= USAGE_THROTTLE_MS) {
+          flushUsage();
+        } else if (!usageTimer) {
+          usageTimer = setTimeout(() => {
+            usageTimer = null;
+            flushUsage();
+          }, USAGE_THROTTLE_MS - elapsed);
+        }
+      },
       signal
     );
   } finally {
@@ -752,6 +796,10 @@ async function executeStreamPhase(
       clearTimeout(pendingFlushTimer);
       pendingFlushTimer = null;
     }
+    if (usageTimer) {
+      clearTimeout(usageTimer);
+      usageTimer = null;
+    }
     await flushPromise;
   }
 }
@@ -1238,6 +1286,7 @@ async function runCapHitSummary(
         });
         scheduleFlush();
       },
+      undefined,
       signal,
     );
     summaryOk = true;
@@ -1499,6 +1548,7 @@ async function runDoomLoopSummary(
         });
         scheduleFlush();
       },
+      undefined,
       signal,
     );
     summaryOk = true;

apps/web/src/api/types.ts

@@ -332,6 +332,17 @@ export type WsFrame =
       // to the client without a refetch.
       metadata?: MessageMetadata | null;
     }
+  // v1.12.2: live throughput frame, published mid-stream every ~500ms with
+  // the latest token + ctx counts so ChatThroughput can render tok/s and
+  // ctx_used while the model is still generating.
+  | {
+      type: 'usage';
+      message_id: string;
+      chat_id?: string;
+      completion_tokens: number | null;
+      ctx_used: number | null;
+      ctx_max: number | null;
+    }
   | { type: 'messages_deleted'; message_ids: string[]; chat_id?: string }
   | { type: 'chat_renamed'; chat_id: string; name: string }
   // v1.11: published by services/compaction.ts after the new anchored

apps/web/src/components/ChatTabBar.tsx

@@ -2,6 +2,7 @@ import { useState } from 'react';
 import { Bot, History, MessageSquare, Plus, Terminal, X } from 'lucide-react';
 import type { Chat, WorkspacePane } from '@/api/types';
 import { StatusDot } from '@/components/StatusDot';
+import { ChatThroughput } from '@/components/ChatThroughput';
 import {
   ContextMenu,
   ContextMenuContent,
@@ -99,6 +100,7 @@ export function ChatTabBar({
               >
                 <MessageSquare size={12} className="shrink-0" />
                 <StatusDot chatId={chat.id} />
+                <ChatThroughput chatId={chat.id} />
                 {renamingId === chat.id ? (
                   <input
                     autoFocus

apps/web/src/components/ChatThroughput.tsx

@@ -0,0 +1,28 @@
+import { useChatStatus } from '@/hooks/useChatStatus';
+import { useChatThroughput } from '@/hooks/useChatThroughput';
+import { cn } from '@/lib/utils';
+
+interface Props {
+  chatId: string | null | undefined;
+  className?: string;
+}
+
+// v1.12.2: inline throughput readout. Renders next to StatusDot while the
+// chat is streaming or running a tool. Hidden in idle/error/waiting states
+// — the dot already communicates those.
+export function ChatThroughput({ chatId, className }: Props) {
+  const status = useChatStatus(chatId);
+  const t = useChatThroughput(chatId);
+  if (!chatId || !t) return null;
+  if (status !== 'streaming' && status !== 'tool_running') return null;
+  const tps = t.tps != null && t.tps > 0 ? Math.round(t.tps) : null;
+  const showCtx = t.ctx_used != null && t.ctx_max != null;
+  if (tps === null && !showCtx) return null;
+  return (
+    <span className={cn('text-xs text-muted-foreground tabular-nums', className)}>
+      {tps !== null && `${tps} tok/s`}
+      {tps !== null && showCtx && ' · '}
+      {showCtx && `${t.ctx_used!.toLocaleString()}/${t.ctx_max!.toLocaleString()}`}
+    </span>
+  );
+}

apps/web/src/components/MobileTabSwitcher.tsx

@@ -13,6 +13,7 @@ import { toast } from 'sonner';
 import type { Chat, WorkspacePane } from '@/api/types';
 import { BottomSheet } from '@/components/BottomSheet';
 import { StatusDot } from '@/components/StatusDot';
+import { ChatThroughput } from '@/components/ChatThroughput';
 import {
   DropdownMenu,
   DropdownMenuContent,
@@ -206,6 +207,7 @@ export function MobileTabSwitcher({
         >
           <span className="shrink-0 text-muted-foreground">{paneIcon(active?.kind ?? 'chat')}</span>
           <StatusDot chatId={activeChatId} />
+          <ChatThroughput chatId={activeChatId} />
           <span className="truncate flex-1 text-left">{activeLabel}</span>
           <ChevronDown size={14} className="opacity-60 shrink-0" />
         </button>
@@ -237,6 +239,7 @@ export function MobileTabSwitcher({
               >
                 <span className="shrink-0 text-muted-foreground">{paneIcon(pane.kind)}</span>
                 <StatusDot chatId={cid ?? null} />
+                <ChatThroughput chatId={cid ?? null} />
                 {renamingChatId === cid && cid ? (
                   <input
                     autoFocus

apps/web/src/hooks/useChatThroughput.ts

@@ -0,0 +1,106 @@
+import { useEffect, useState } from 'react';
+
+// v1.12.2: live throughput stream consumer. Fed by useSessionStream when a
+// 'usage' WS frame lands. Renders next to StatusDot via ChatThroughput.
+//
+// Singleton + Set<setState> pattern mirrors useChatStatus so any component
+// can subscribe to any chatId without prop drilling.
+
+export interface ThroughputSample {
+  tps: number | null;
+  ctx_used: number | null;
+  ctx_max: number | null;
+}
+
+interface Entry {
+  ctx_used: number | null;
+  ctx_max: number | null;
+  completion_tokens: number | null;
+  recorded_at: number;
+  prev_completion_tokens: number | null;
+  prev_recorded_at: number | null;
+  tps: number | null;
+}
+
+// Stale window. After this, useChatThroughput returns null — clears the
+// indicator after the stream ends without the next inference turn.
+const STALE_MS = 10_000;
+
+const entries = new Map<string, Entry>();
+const subscribers = new Set<() => void>();
+
+function notify(): void {
+  for (const s of subscribers) {
+    try { s(); } catch { /* swallow */ }
+  }
+}
+
+// v1.12.2: imported by useSessionStream's WS handler. Computes tps from the
+// gap between successive completion_tokens samples; first sample yields null
+// (we need two points). Skips zero-progress samples so a duplicate usage
+// frame doesn't push tps to 0.
+export function recordUsage(
+  chatId: string,
+  data: { completion_tokens: number | null; ctx_used: number | null; ctx_max: number | null },
+): void {
+  const now = Date.now();
+  const prev = entries.get(chatId);
+  let tps: number | null = prev?.tps ?? null;
+  if (
+    prev &&
+    data.completion_tokens != null &&
+    prev.completion_tokens != null &&
+    data.completion_tokens > prev.completion_tokens &&
+    now > prev.recorded_at
+  ) {
+    const dTokens = data.completion_tokens - prev.completion_tokens;
+    const dSeconds = (now - prev.recorded_at) / 1000;
+    tps = dTokens / dSeconds;
+  }
+  entries.set(chatId, {
+    ctx_used: data.ctx_used,
+    ctx_max: data.ctx_max,
+    completion_tokens: data.completion_tokens,
+    recorded_at: now,
+    prev_completion_tokens: prev?.completion_tokens ?? null,
+    prev_recorded_at: prev?.recorded_at ?? null,
+    tps,
+  });
+  notify();
+}
+
+export function clearThroughput(chatId: string): void {
+  if (entries.delete(chatId)) notify();
+}
+
+// Periodic sweep: re-notify so stale entries fall off the UI when the
+// stream ends without a follow-up frame. Light — one timer for the whole app.
+const G = globalThis as Record<string, unknown>;
+if (!G.__boocode_throughput_ticker) {
+  G.__boocode_throughput_ticker = true;
+  setInterval(() => {
+    const now = Date.now();
+    let touched = false;
+    for (const [k, v] of entries) {
+      if (now - v.recorded_at > STALE_MS) {
+        entries.delete(k);
+        touched = true;
+      }
+    }
+    if (touched) notify();
+  }, 2_000);
+}
+
+export function useChatThroughput(chatId: string | null | undefined): ThroughputSample | null {
+  const [, force] = useState({});
+  useEffect(() => {
+    const sub = () => force({});
+    subscribers.add(sub);
+    return () => { subscribers.delete(sub); };
+  }, []);
+  if (!chatId) return null;
+  const entry = entries.get(chatId);
+  if (!entry) return null;
+  if (Date.now() - entry.recorded_at > STALE_MS) return null;
+  return { tps: entry.tps, ctx_used: entry.ctx_used, ctx_max: entry.ctx_max };
+}

apps/web/src/hooks/useSessionStream.ts

@@ -3,6 +3,7 @@ import { toast } from 'sonner';
 import type { Message, WsFrame } from '@/api/types';
 import { api } from '@/api/client';
 import { sessionEvents } from './sessionEvents';
+import { recordUsage } from './useChatThroughput';
 
 // session_renamed frame removed from WsFrame — it was declared but never
 // published on the per-session WS channel (server publishes via broker.publishUser
@@ -125,6 +126,19 @@ function applyFrame(state: State, frame: WsFrame): State {
       );
       return { ...state, messages: next };
     }
+    case 'usage': {
+      // v1.12.2: live throughput. Side-effects into the module-level
+      // singleton consumed by ChatThroughput; no message-state mutation.
+      // chat_id is the optional ws-frame field; usage frames always include it.
+      if (frame.chat_id) {
+        recordUsage(frame.chat_id, {
+          completion_tokens: frame.completion_tokens,
+          ctx_used: frame.ctx_used,
+          ctx_max: frame.ctx_max,
+        });
+      }
+      return state;
+    }
     case 'messages_deleted': {
       const removeSet = new Set(frame.message_ids);
       return {