diff --git a/web/hwlab-cloud-web/src/components/agent/TraceTimeline.test.ts b/web/hwlab-cloud-web/src/components/agent/TraceTimeline.test.ts
index 271341b0..41c80bc3 100644
--- a/web/hwlab-cloud-web/src/components/agent/TraceTimeline.test.ts
+++ b/web/hwlab-cloud-web/src/components/agent/TraceTimeline.test.ts
@@ -1,3 +1,4 @@
+// SPEC: PJ2026-0106050514 Workbench实时运行面 draft-2026-06-30-p0-1297-spec-first; PJ2026-010401080313 Workbench实时权威 draft-2026-07-14-p0-pure-kafka-authority.
 // @vitest-environment jsdom
 
 import { beforeEach, describe, expect, it } from "vitest";
@@ -270,6 +271,42 @@ describe("TraceTimeline sequence authority", () => {
     expect(completedSummary.text()).not.toMatch(/\b(?:ok|fail|run|running)\b|total=|duration=|exit=|工具调用成功/u);
     wrapper.unmount();
   });
+
+  it("bounds renderer input and DOM rows for a long Kafka Trace", async () => {
+    const events = Array.from({ length: 1_000 }, (_, index) => ({
+      sourceEventId: `evt_long_${index + 1}`,
+      runId: "run_long_trace",
+      sourceSeq: index + 1,
+      source: "agentrun.kafka",
+      type: "assistant",
+      label: "agentrun:assistant:message",
+      message: `long trace event ${index + 1}`
+    }));
+    const wrapper = mount(TraceTimeline, {
+      props: {
+        autoExpanded: true,
+        trace: {
+          traceId: "trc_long_timeline",
+          eventSource: "hwlab-kafka-sse",
+          status: "running",
+          eventCount: events.length,
+          events
+        }
+      }
+    });
+    await nextTick();
+
+    const disclosure = wrapper.get(".trace-disclosure");
+    expect(disclosure.attributes("data-event-count")).toBe("1000");
+    expect(disclosure.attributes("data-render-input-count")).toBe("240");
+    expect(disclosure.attributes("data-row-windowed")).toBe("true");
+    const rows = wrapper.findAll('[data-testid="trace-render-row"]');
+    expect(rows).toHaveLength(120);
+    expect(Number(rows[0]?.attributes("data-event-seq"))).toBeGreaterThanOrEqual(881);
+    expect(rows.at(-1)?.attributes("data-event-seq")).toBe("1000");
+    expect(wrapper.text()).toContain("共 1000 events");
+    wrapper.unmount();
+  });
 });
 
 function liveTrace(status: "running" | "completed") {
diff --git a/web/hwlab-cloud-web/src/components/agent/TraceTimeline.vue b/web/hwlab-cloud-web/src/components/agent/TraceTimeline.vue
index 69b09840..8873aafc 100644
--- a/web/hwlab-cloud-web/src/components/agent/TraceTimeline.vue
+++ b/web/hwlab-cloud-web/src/components/agent/TraceTimeline.vue
@@ -1,3 +1,4 @@
+<!-- SPEC: PJ2026-0106050514 Workbench实时运行面 draft-2026-06-30-p0-1297-spec-first; PJ2026-010401080313 Workbench实时权威 draft-2026-07-14-p0-pure-kafka-authority. Render a bounded, stable Trace tail from the Kafka SSE projection. -->
 <script setup lang="ts">
 import { computed, ref, watch } from "vue";
 import type { RunnerTrace } from "@/types";
@@ -18,13 +19,17 @@ const props = defineProps<{
 }>();
 
 const TRACE_RENDER_ROW_WINDOW = 120;
+const TRACE_RENDER_EVENT_WINDOW = TRACE_RENDER_ROW_WINDOW * 2;
 const listRef = ref<HTMLOListElement | null>(null);
 const expanded = ref(false);
 const { following, keepBottomAfterUpdate, onScroll, scrollToBottom } = useWorkbenchBottomFollowScroll(listRef, { threshold: 24 });
 
 const events = computed(() => Array.isArray(props.trace?.events) ? props.trace.events : []);
 const eventCount = computed(() => props.trace?.eventCount ?? events.value.length);
-const rawReadableRows = computed(() => expanded.value ? traceDisplayRows(traceRecord(props.trace), events.value as Record<string, unknown>[], {
+const renderEvents = computed(() => events.value.length > TRACE_RENDER_EVENT_WINDOW
+  ? events.value.slice(-TRACE_RENDER_EVENT_WINDOW)
+  : events.value);
+const rawReadableRows = computed(() => expanded.value ? traceDisplayRows(traceRecord(props.trace), renderEvents.value as Record<string, unknown>[], {
   formatClock: formatDisplayClock,
   finalResponsePlacement: props.finalResponsePlacement,
   outerFinalResponseText: props.outerFinalResponseText
@@ -32,6 +37,7 @@ const rawReadableRows = computed(() => expanded.value ? traceDisplayRows(traceRe
 const readableRows = computed(() => rawReadableRows.value);
 const hiddenRowCount = computed(() => Math.max(0, readableRows.value.length - TRACE_RENDER_ROW_WINDOW));
 const renderedRows = computed(() => hiddenRowCount.value > 0 ? readableRows.value.slice(-TRACE_RENDER_ROW_WINDOW) : readableRows.value);
+const inputEventWindowed = computed(() => renderEvents.value.length < events.value.length);
 const traceSummaryLabel = computed(() => {
   const count = eventCount.value;
   if (count <= 0) return String(props.trace?.status ?? "").trim() || "pending";
@@ -159,14 +165,14 @@ function firstNonEmptyString(...values: unknown[]): string | null {
 
 <template>
   <section v-if="trace" class="trace-timeline" :data-trace-id="trace.traceId || undefined" :data-status="trace.status" :data-projection-health="trace.projection?.projectionHealth || trace.projectionHealth || undefined" :data-following="following ? 'true' : 'false'">
-    <details class="trace-disclosure" :open="expanded" :data-event-count="eventCount" :data-readable-row-count="readableRows.length" :data-rendered-row-count="renderedRows.length" :data-row-windowed="hiddenRowCount > 0 ? 'true' : 'false'" @toggle="onDisclosureToggle">
+    <details class="trace-disclosure" :open="expanded" :data-event-count="eventCount" :data-render-input-count="renderEvents.length" :data-readable-row-count="readableRows.length" :data-rendered-row-count="renderedRows.length" :data-row-windowed="hiddenRowCount > 0 || inputEventWindowed ? 'true' : 'false'" @toggle="onDisclosureToggle">
       <summary class="trace-disclosure-summary" aria-label="折叠运行记录">
         <span class="trace-disclosure-caret" aria-hidden="true" />
         <span class="trace-disclosure-label">运行记录</span>
         <span class="trace-disclosure-count">{{ traceSummaryLabel }}</span>
       </summary>
       <div v-if="expanded" class="trace-disclosure-body">
-        <p v-if="hiddenRowCount > 0" class="trace-window-notice">显示最近 {{ renderedRows.length }} / {{ readableRows.length }} 行</p>
+        <p v-if="hiddenRowCount > 0 || inputEventWindowed" class="trace-window-notice">显示最近 {{ renderedRows.length }} 行，共 {{ eventCount }} events</p>
         <ol v-if="renderedRows.length > 0" ref="listRef" @scroll="onScroll">
           <li v-for="(row, index) in renderedRows" :key="rowKey(row, index)" class="trace-render-row" data-testid="trace-render-row" :data-trace-id="trace.traceId || undefined" :data-event-seq="row.seq ?? undefined" :data-event-seq-authority="row.sequenceAuthority" :data-projected-seq="row.sequenceAuthority === 'projected' ? row.seq ?? undefined : undefined" :data-event-kind="row.rowId" :data-event-status="row.tone" :data-tool-state="row.toolState ?? undefined" :data-terminal="row.terminal ? 'true' : 'false'" :data-row-kind="rowIsTool(row) ? 'tool' : 'message'" :data-row-id="row.rowId" :aria-posinset="hiddenRowCount + index + 1">
             <details v-if="rowIsTool(row)" class="trace-tool-details" :aria-busy="row.toolState === 'running' ? 'true' : undefined">