diff --git a/CHANGELOG.md b/CHANGELOG.md
index 15548ea3b..a4d45c921 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -61,6 +61,7 @@ opt-out.
 - Insights runs/day averages over the days an agent was active in the window, so an agent first seen today with 12 runs reports 12/day instead of 12/7.
 - An open run's root start is kept when the reporter's buffer trims or a crash flush cuts to its newest 16 MB, so a run whose child spans overflow the buffer is still listed.
 - The run inspector shows `error`, not `running`, for a failed step that has no end time.
+- Studio trace viewer: an observation the crash sweep marked `interrupted` (or an open `error` one) now shows as terminal instead of "running" forever; its duration and the waterfall stop at the latest known end and the header clock stops ticking.
 - The observe daemon refuses cross-site browser writes and DNS rebinding on `/api/*`: a loopback-bound daemon answers only loopback `Host` names (403), writes carrying a non-loopback `Origin` (including `null`) or `Sec-Fetch-Site: cross-site` get 403, and a write with a body must be `Content-Type: application/json` (415) — `curl -d` needs `-H "Content-Type: application/json"`. The SDK reporter, CLI and Studio already comply. See [Observability](docs/observability.md).
 - Observe retention (`lousho observe start --retention-days`, `lousho observe prune`) also deletes old traces the sweep marked `interrupted` (a crashed run whose end never arrived); their age counts from when they were interrupted.
 
diff --git a/apps/agent-forge/src/observe/__tests__/tree.test.ts b/apps/agent-forge/src/observe/__tests__/tree.test.ts
index 97d1090f5..4b8524b9c 100644
--- a/apps/agent-forge/src/observe/__tests__/tree.test.ts
+++ b/apps/agent-forge/src/observe/__tests__/tree.test.ts
@@ -92,6 +92,12 @@ describe('traceBounds', () => {
     expect(bounds).toEqual({ minStart: 100, maxEnd: 1000 });
   });
 
+  it('does not count an open interrupted or error row to now', () => {
+    expect(
+      traceBounds([row({ start: 100, end: 400 }), row({ start: 200, end: null, status: 'interrupted' }), row({ start: 300, end: null, status: 'error' })], 1000),
+    ).toEqual({ minStart: 100, maxEnd: 400 });
+  });
+
   it('is degenerate-safe on empty input', () => {
     expect(traceBounds([])).toEqual({ minStart: 0, maxEnd: 1 });
   });
diff --git a/apps/agent-forge/src/observe/tree.ts b/apps/agent-forge/src/observe/tree.ts
index ff73d2995..40eb84c65 100644
--- a/apps/agent-forge/src/observe/tree.ts
+++ b/apps/agent-forge/src/observe/tree.ts
@@ -75,14 +75,27 @@ export function flattenObservationTree(roots: ObservationNode[]): ObservationNod
   return flat;
 }
 
-/** `[start, end]` bounds over every observation (an unfinished row counts to `now`). */
+/** The latest `end` among a node and its descendants, or `undefined` when none has ended. */
+export function latestKnownEnd(node: ObservationNode, seen = new Set<string>()): number | undefined {
+  if (seen.has(node.row.obs_id)) return undefined;
+  seen.add(node.row.obs_id);
+  let latest = node.row.end ?? undefined;
+  for (const child of node.children) {
+    const end = latestKnownEnd(child, seen);
+    if (end !== undefined && (latest === undefined || end > latest)) latest = end;
+  }
+  return latest;
+}
+
+/** `[start, end]` bounds over every observation (a running row counts to `now`; an open interrupted/error row stops at its start). */
 export function traceBounds(rows: ObserveObservationRow[], now = Date.now()): { minStart: number; maxEnd: number } {
   if (rows.length === 0) return { minStart: 0, maxEnd: 1 };
   let minStart = Infinity;
   let maxEnd = -Infinity;
   for (const row of rows) {
     minStart = Math.min(minStart, row.start);
-    maxEnd = Math.max(maxEnd, row.end ?? now);
+    const open = row.status === 'interrupted' || row.status === 'error' ? row.start : now;
+    maxEnd = Math.max(maxEnd, row.end ?? open);
   }
   return { minStart, maxEnd: Math.max(maxEnd, minStart + 1) };
 }
diff --git a/apps/agent-forge/src/screens/queues/QueueReview.tsx b/apps/agent-forge/src/screens/queues/QueueReview.tsx
index e3352d472..f2127e238 100644
--- a/apps/agent-forge/src/screens/queues/QueueReview.tsx
+++ b/apps/agent-forge/src/screens/queues/QueueReview.tsx
@@ -13,7 +13,7 @@ import type { ObserveQueue, ObserveQueueItem } from '../../observe/types';
 import { useDaemonDown, useNextQueueItem, useQueue, useTraceDetail } from '../../observe/useObserve';
 import { EmptyState } from '../../ui/EmptyState';
 import { TraceViewer, type TraceViewMode } from '../../ui/run/TraceViewer';
-import { displayName } from '../../ui/run/rows';
+import { displayName, isRunning } from '../../ui/run/rows';
 import { useNow } from '../../ui/run/useNow';
 import { fmtInt } from '../../observe/format';
 import { RubricForm } from './RubricForm';
@@ -38,7 +38,7 @@ function ReviewItem({ queue, item, onDone }: { queue: ObserveQueue; item: Observ
   const [mode, setMode] = useState<TraceViewMode>('tree');
   const observations = trace.data?.observations;
   const root = useMemo(() => (observations ? nestObservations(observations)[0]?.row : undefined), [observations]);
-  const now = useNow(root?.end === null);
+  const now = useNow(root !== undefined && isRunning(root));
 
   let body;
   if (down) body = <ObserveDaemonDown />;
diff --git a/apps/agent-forge/src/screens/traces/TraceHeader.tsx b/apps/agent-forge/src/screens/traces/TraceHeader.tsx
index b9f90257b..16e7a69ea 100644
--- a/apps/agent-forge/src/screens/traces/TraceHeader.tsx
+++ b/apps/agent-forge/src/screens/traces/TraceHeader.tsx
@@ -6,6 +6,13 @@ import { displayName, displayStatus, elapsedMs } from '../../ui/run/rows';
 import { AddToDataset } from './AddToDataset';
 import { AddToQueue } from './AddToQueue';
 
+/** The latest `end` over every observation, or `undefined` when none has ended. */
+function latestEnd(rows: ObserveObservationRow[]): number | undefined {
+  let latest: number | undefined;
+  for (const row of rows) if (row.end !== null && (latest === undefined || row.end > latest)) latest = row.end;
+  return latest;
+}
+
 /** Trace-wide totals, summed over every observation the way the daemon's trace list does. */
 function traceTotals(rows: ObserveObservationRow[]): { tokens: number | null; cost: number | null } {
   let tokens: number | null = null;
@@ -88,7 +95,7 @@ export function TraceHeader({
         )}
         <Fact label="Model">{model ? <code>{model}</code> : '-'}</Fact>
         <Fact label="Start">{fmtDateTime(root.start)}</Fact>
-        <Fact label="Duration">{fmtDuration(elapsedMs(root, now))}</Fact>
+        <Fact label="Duration">{fmtDuration(elapsedMs(root, now, latestEnd(observations)))}</Fact>
         <Fact label="Tokens">{fmtInt(tokens)}</Fact>
         <Fact label="Cost">{fmtCost(cost)}</Fact>
         {root.session_id && (
diff --git a/apps/agent-forge/src/screens/traces/TraceScreen.tsx b/apps/agent-forge/src/screens/traces/TraceScreen.tsx
index 1b1be08e7..f657e6a3e 100644
--- a/apps/agent-forge/src/screens/traces/TraceScreen.tsx
+++ b/apps/agent-forge/src/screens/traces/TraceScreen.tsx
@@ -9,6 +9,7 @@ import { useQueryState } from '../../router/useRoute';
 import { EmptyState } from '../../ui/EmptyState';
 import { tracesListPath } from './tracesUrl';
 import { TraceViewer, type TraceViewMode } from '../../ui/run/TraceViewer';
+import { isRunning } from '../../ui/run/rows';
 import { useNow } from '../../ui/run/useNow';
 import { TraceFeedback } from './TraceFeedback';
 import { TraceHeader } from './TraceHeader';
@@ -49,7 +50,7 @@ function useTrace(traceId: string, pollMs: number) {
 
   const observations = detail.data?.observations;
   const root = useMemo(() => (observations ? rootOf(observations) : undefined), [observations]);
-  const now = useNow(root?.end === null);
+  const now = useNow(root !== undefined && isRunning(root));
   const agentName = agents.data?.find((a) => a.agent_id === root?.agent_id)?.name ?? undefined;
   return { detail, down, root, now, agentName };
 }
diff --git a/apps/agent-forge/src/screens/traces/__tests__/TraceScreen.test.tsx b/apps/agent-forge/src/screens/traces/__tests__/TraceScreen.test.tsx
index 170987eec..1d210c820 100644
--- a/apps/agent-forge/src/screens/traces/__tests__/TraceScreen.test.tsx
+++ b/apps/agent-forge/src/screens/traces/__tests__/TraceScreen.test.tsx
@@ -144,6 +144,24 @@ describe('TraceScreen', () => {
     expect(header.querySelector('button[aria-label="Copy link"]')).not.toBeNull();
   });
 
+  it('header duration for an interrupted root with no end stops at the latest child end', async () => {
+    daemon({
+      trace: {
+        trace_id: 't1',
+        observations: [
+          obs({ obs_id: 'root', name: 'crashed run', start: T0, end: null, status: 'interrupted' }),
+          obs({ obs_id: 'c1', parent_obs_id: 'root', start: T0 + 100, end: T0 + 4000 }),
+        ],
+        scores: [],
+      },
+    });
+    const c = mount();
+    await waitFor(() => c.querySelector('.trace-header') !== null);
+    const header = c.querySelector('.trace-header') as HTMLElement;
+    expect(header.textContent).toContain('4.0s');
+    expect(header.textContent).toContain('interrupted');
+  });
+
   it('selects the ?obs= node on load and writes ?obs= with replace on selection', async () => {
     window.history.replaceState(null, '', '/#/traces/t1?obs=tool1');
     daemon({ trace: TRACE });
diff --git a/apps/agent-forge/src/ui/run/RunTree.tsx b/apps/agent-forge/src/ui/run/RunTree.tsx
index d00a3dea4..ca1121028 100644
--- a/apps/agent-forge/src/ui/run/RunTree.tsx
+++ b/apps/agent-forge/src/ui/run/RunTree.tsx
@@ -2,7 +2,7 @@ import type { ReactNode } from 'react';
 
 import { VirtualList } from '../../components/debug/VirtualList';
 import { fmtDuration, fmtInt } from '../../observe/format';
-import type { ObservationNode } from '../../observe/tree';
+import { latestKnownEnd, type ObservationNode } from '../../observe/tree';
 import type { ObserveObservationRow } from '../../observe/types';
 import { StatusPill } from '../StatusPill';
 import {
@@ -56,8 +56,9 @@ function KindIcon({ kind }: { kind: string }) {
   );
 }
 
-function Duration({ row, now }: { row: ObserveObservationRow; now: number }) {
-  const ms = elapsedMs(row, now);
+function Duration({ node, now }: { node: ObservationNode; now: number }) {
+  const { row } = node;
+  const ms = elapsedMs(row, now, !isRunning(row) && row.end === null ? latestKnownEnd(node) : undefined);
   if (isRunning(row)) return <span className="run-dur run-dur-live">{fmtDuration(ms)} running</span>;
   return <span className="run-dur">{fmtDuration(ms)}</span>;
 }
@@ -96,7 +97,7 @@ function TreeRow({ node, selected, virtual, now, playgroundLinks, onSelect }: Tr
         {status !== 'ok' && status !== null && <StatusPill status={status} />}
         {row.model && <span className="run-model-chip">{row.model}</span>}
         {tokens !== null && <span className="run-tokens">{fmtInt(tokens)} tok</span>}
-        <Duration row={row} now={now} />
+        <Duration node={node} now={now} />
       </button>
       {playgroundLinks && row.kind === 'generation' && (
         <a className="run-playground-link" href={playgroundHref(row.trace_id, row.obs_id)} title={`Open ${name} in Playground`}>
diff --git a/apps/agent-forge/src/ui/run/Waterfall.tsx b/apps/agent-forge/src/ui/run/Waterfall.tsx
index 67ee98a6c..468de1c19 100644
--- a/apps/agent-forge/src/ui/run/Waterfall.tsx
+++ b/apps/agent-forge/src/ui/run/Waterfall.tsx
@@ -1,6 +1,6 @@
 import { VirtualList } from '../../components/debug/VirtualList';
 import { fmtDuration } from '../../observe/format';
-import { traceBounds, type ObservationNode } from '../../observe/tree';
+import { latestKnownEnd, traceBounds, type ObservationNode } from '../../observe/tree';
 import type { ObserveObservationRow } from '../../observe/types';
 import { VIRTUALISE_ABOVE, VIRTUAL_ROW_HEIGHT, cx, displayName, elapsedMs, isRunning, useFlatNodes } from './rows';
 import './run.css';
@@ -62,7 +62,7 @@ interface BarRowProps {
 
 function BarRow({ node, minStart, totalMs, now, selected, virtual, onSelect }: BarRowProps) {
   const { row } = node;
-  const ms = elapsedMs(row, now);
+  const ms = elapsedMs(row, now, !isRunning(row) && row.end === null ? latestKnownEnd(node) : undefined);
   const left = ((row.start - minStart) / totalMs) * 100;
   const width = Math.max(0.5, (ms / totalMs) * 100);
   const failed = row.status === 'error';
diff --git a/apps/agent-forge/src/ui/run/__tests__/run.test.tsx b/apps/agent-forge/src/ui/run/__tests__/run.test.tsx
index 85630013d..18263a25a 100644
--- a/apps/agent-forge/src/ui/run/__tests__/run.test.tsx
+++ b/apps/agent-forge/src/ui/run/__tests__/run.test.tsx
@@ -65,6 +65,19 @@ const TRACE: ObserveObservationRow[] = [
 const row = (c: HTMLElement, id: string) => c.querySelector(`[data-obs-id="${id}"]`) as HTMLElement;
 
 describe('RunTree', () => {
+  it('treats an interrupted row with no end as terminal: no "running", elapsed stops at the latest known end', () => {
+    const rows = [
+      obs({ obs_id: 'iroot', end: null, status: 'interrupted' }),
+      obs({ obs_id: 'ichild', parent_obs_id: 'iroot', start: T0 + 10, end: T0 + 250 }),
+    ];
+    const c = render(<RunTree observations={rows} onSelect={() => {}} now={T0 + 60_000} />);
+    const r = row(c, 'iroot');
+    expect(r.querySelector('.run-dur')?.textContent).toBe('250ms');
+    expect(r.querySelector('.run-dur-live')).toBeNull();
+    expect(r.textContent).not.toContain('running');
+    expect(r.textContent).toContain('interrupted');
+  });
+
   it('indents rows by depth in depth-first order', () => {
     const c = render(<RunTree observations={TRACE} onSelect={() => {}} now={T0 + 5000} />);
     const rows = [...c.querySelectorAll<HTMLElement>('.run-tree-row')];
diff --git a/apps/agent-forge/src/ui/run/rows.ts b/apps/agent-forge/src/ui/run/rows.ts
index eaa77206e..592f44437 100644
--- a/apps/agent-forge/src/ui/run/rows.ts
+++ b/apps/agent-forge/src/ui/run/rows.ts
@@ -30,20 +30,25 @@ export function totalTokens(row: ObserveObservationRow): number | null {
   return (row.usage_input_tokens ?? 0) + (row.usage_output_tokens ?? 0);
 }
 
-/** An open observation (`end === null`) is running, whatever its stored status says. */
+/** An open observation (`end === null`) is running unless its stored status is terminal (`interrupted` by the crash sweep, or `error`). */
 export function isRunning(row: ObserveObservationRow): boolean {
-  return row.end === null;
+  return row.end === null && row.status !== 'interrupted' && row.status !== 'error';
 }
 
-/** The status to display: a stored `error` always wins; else `running` for an open observation, else the stored status. */
+/** The status to display: a stored terminal status (`error`, `interrupted`) always wins; else `running` for an open observation, else the stored status. */
 export function displayStatus(row: ObserveObservationRow): string | null {
-  if (row.status === 'error') return 'error';
+  if (row.status === 'error' || row.status === 'interrupted') return row.status;
   return isRunning(row) ? 'running' : row.status;
 }
 
-/** Elapsed ms: `end - start`, or `now - start` while still running. */
-export function elapsedMs(row: ObserveObservationRow, now: number): number {
-  return Math.max(0, (row.end ?? now) - row.start);
+/**
+ * Elapsed ms: `end - start`, or `now - start` while still running. An open
+ * row with a terminal status stops at `fallbackEnd` (the latest known end
+ * among it and its descendants), else at its start; it never counts to `now`.
+ */
+export function elapsedMs(row: ObserveObservationRow, now: number, fallbackEnd?: number): number {
+  const end = row.end ?? (isRunning(row) ? now : (fallbackEnd ?? row.start));
+  return Math.max(0, end - row.start);
 }
 
 /** The href that opens a generation in the Playground (it loads the trace, then pre-fills from the observation). */