diff --git a/app/src/features/conversations/Conversations.tsx b/app/src/features/conversations/Conversations.tsx
index 271ddbb65..aa3e6ef24 100644
--- a/app/src/features/conversations/Conversations.tsx
+++ b/app/src/features/conversations/Conversations.tsx
@@ -2691,6 +2691,7 @@ const Conversations = ({
                             id: 'active-tool',
                             name: selectedInferenceStatus.activeTool ?? 'tool',
                             round: selectedInferenceStatus.iteration,
+                            seq: 0,
                             status: 'running',
                           }
                         ).title
@@ -2702,6 +2703,7 @@ const Conversations = ({
                             id: 'active-subagent',
                             name: `subagent:${selectedInferenceStatus.activeSubagent ?? ''}`,
                             round: selectedInferenceStatus.iteration,
+                            seq: 0,
                             status: 'running',
                           }
                         ).title
diff --git a/app/src/features/conversations/components/ProcessingTranscriptView.test.tsx b/app/src/features/conversations/components/ProcessingTranscriptView.test.tsx
index 94a6926b7..7ff928381 100644
--- a/app/src/features/conversations/components/ProcessingTranscriptView.test.tsx
+++ b/app/src/features/conversations/components/ProcessingTranscriptView.test.tsx
@@ -16,6 +16,7 @@ function failedEntry(overrides: Partial<ToolTimelineEntry> = {}): ToolTimelineEn
     id: 'call-1',
     name: 'read_file',
     round: 1,
+    seq: 0,
     status: 'error',
     failure: {
       class: 'MissingPermission',
diff --git a/app/src/features/conversations/components/ToolTimelineBlock.tsx b/app/src/features/conversations/components/ToolTimelineBlock.tsx
index d66d926f8..b78330de5 100644
--- a/app/src/features/conversations/components/ToolTimelineBlock.tsx
+++ b/app/src/features/conversations/components/ToolTimelineBlock.tsx
@@ -481,7 +481,6 @@ export function ToolTimelineBlock({
   liveResponse?: string;
 }) {
   const { t } = useT();
-  const latestRunningEntryId = [...entries].reverse().find(entry => entry.status === 'running')?.id;
 
   // Sticky override for the outer "Agentic task insights" group: `null` means
   // the user hasn't explicitly toggled it on THIS mount yet, so the group
@@ -502,6 +501,18 @@ export function ToolTimelineBlock({
 
   if (entries.length === 0) return null;
 
+  // The rows + the parent's streaming response — shared by both the collapsible
+  // (in-flight) and static (settled) header layouts below.
+  // Sort by issue order (`seq`), not arrival order: a `tool_args_delta` for a
+  // later parallel call can reach the store before an earlier call's own
+  // event, which would otherwise create rows in the wrong order.
+  // Sort a copy — `entries` may be a state slice other callers still rely on.
+  const ordered = [...entries].sort((a, b) => a.seq - b.seq);
+  // "Latest running" must be derived from the same seq-ordered list the rows
+  // render from — not raw arrival order — or a running row that arrived late
+  // but sorts earlier (e.g. seq [2, 0, 1]) gets treated as "latest" and the
+  // wrong step stays expanded/linked in compact chat mode.
+  const latestRunningEntryId = [...ordered].reverse().find(entry => entry.status === 'running')?.id;
   const isRunning = latestRunningEntryId != null;
 
   const titleLabel = (
@@ -527,11 +538,9 @@ export function ToolTimelineBlock({
     </button>
   ) : null;
 
-  // The rows + the parent's streaming response — shared by both the collapsible
-  // (in-flight) and static (settled) header layouts below.
   // Coalesce runs of identical, body-less rows (e.g. a retry loop that spawns
   // the same integrations step 25×) into single `×N` rows before rendering.
-  const rows = coalesceTimelineEntries(entries);
+  const rows = coalesceTimelineEntries(ordered);
 
   const body = (
     <>
diff --git a/app/src/features/conversations/components/__tests__/AgentProcessSourcePanel.test.tsx b/app/src/features/conversations/components/__tests__/AgentProcessSourcePanel.test.tsx
index cfdcf1890..39a726369 100644
--- a/app/src/features/conversations/components/__tests__/AgentProcessSourcePanel.test.tsx
+++ b/app/src/features/conversations/components/__tests__/AgentProcessSourcePanel.test.tsx
@@ -15,6 +15,7 @@ const fetchEntry = (id: string, url: string): ToolTimelineEntry => ({
   id,
   name: 'web_fetch',
   round: 1,
+  seq: 0,
   status: 'success',
   argsBuffer: JSON.stringify({ url }),
 });
@@ -82,6 +83,7 @@ describe('AgentProcessSourcePanel', () => {
             id: 'sa',
             name: 'subagent:researcher',
             round: 1,
+            seq: 0,
             status: 'success',
             subagent: {
               taskId: 'sub-1',
@@ -103,8 +105,8 @@ describe('AgentProcessSourcePanel', () => {
       <AgentProcessSourcePanel
         open
         entries={[
-          { id: 'c1', name: 'file_read', round: 1, status: 'success' },
-          { id: 'c2', name: 'file_read', round: 1, status: 'success' },
+          { id: 'c1', name: 'file_read', round: 1, seq: 0, status: 'success' },
+          { id: 'c2', name: 'file_read', round: 1, seq: 0, status: 'success' },
         ]}
         transcript={[
           { kind: 'narration', round: 1, seq: 0, text: 'Let me check both docs first.' },
@@ -132,6 +134,7 @@ describe('AgentProcessSourcePanel', () => {
             id: 'sa-1',
             name: 'subagent:researcher',
             round: 1,
+            seq: 0,
             status: 'success',
             subagent: {
               taskId: 'task-1',
@@ -160,6 +163,7 @@ describe('AgentProcessSourcePanel', () => {
       id: 'sa-scope',
       name: 'subagent:researcher',
       round: 1,
+      seq: 0,
       status: 'success',
       subagent: {
         taskId: 'task-9',
@@ -174,7 +178,7 @@ describe('AgentProcessSourcePanel', () => {
         entries={[
           scoped,
           // A second, unrelated step that must NOT show in the scoped view.
-          { id: 'other', name: 'web_fetch', round: 1, status: 'success' },
+          { id: 'other', name: 'web_fetch', round: 1, seq: 0, status: 'success' },
         ]}
         transcript={[{ kind: 'narration', round: 1, seq: 0, text: 'whole-run narration' }]}
         scopedEntry={scoped}
@@ -195,6 +199,7 @@ describe('AgentProcessSourcePanel', () => {
       id: 'tool-result-only',
       name: 'run_code',
       round: 1,
+      seq: 0,
       status: 'success',
       argsBuffer: '{"command":"pnpm test"}',
       result: 'exit 0\nAll checks passed.',
@@ -211,7 +216,7 @@ describe('AgentProcessSourcePanel', () => {
     renderPanel(
       <AgentProcessSourcePanel
         open
-        entries={[{ id: 'x', name: 'file_read', round: 1, status: 'success' }]}
+        entries={[{ id: 'x', name: 'file_read', round: 1, seq: 0, status: 'success' }]}
         onClose={() => {}}
       />
     );
diff --git a/app/src/features/conversations/components/__tests__/BackgroundProcessesPanel.test.tsx b/app/src/features/conversations/components/__tests__/BackgroundProcessesPanel.test.tsx
index 3feb487ab..661287518 100644
--- a/app/src/features/conversations/components/__tests__/BackgroundProcessesPanel.test.tsx
+++ b/app/src/features/conversations/components/__tests__/BackgroundProcessesPanel.test.tsx
@@ -22,7 +22,7 @@ function entry(
   subagent?: SubagentActivity,
   name = 'subagent:researcher'
 ): ToolTimelineEntry {
-  return { id: `e-${subagent?.taskId ?? name}`, name, round: 0, status, subagent };
+  return { id: `e-${subagent?.taskId ?? name}`, name, round: 0, seq: 0, status, subagent };
 }
 
 describe('selectBackgroundProcesses', () => {
diff --git a/app/src/features/conversations/components/__tests__/ToolTimelineBlock.test.tsx b/app/src/features/conversations/components/__tests__/ToolTimelineBlock.test.tsx
index d0c692f34..6743380e6 100644
--- a/app/src/features/conversations/components/__tests__/ToolTimelineBlock.test.tsx
+++ b/app/src/features/conversations/components/__tests__/ToolTimelineBlock.test.tsx
@@ -299,11 +299,19 @@ describe('SubagentActivityBlock', () => {
 describe('ToolTimelineBlock — agentic task insights surface', () => {
   it('wraps rows in the "Agentic task insights" group and conveys run state on the name', () => {
     const entries: ToolTimelineEntry[] = [
-      { id: 'r', name: 'web_search', round: 1, status: 'running', argsBuffer: '{"query":"f1"}' },
+      {
+        id: 'r',
+        name: 'web_search',
+        round: 1,
+        seq: 0,
+        status: 'running',
+        argsBuffer: '{"query":"f1"}',
+      },
       {
         id: 'd',
         name: 'file_read',
         round: 1,
+        seq: 0,
         status: 'success',
         argsBuffer: '{"path":"/a/b.txt"}',
       },
@@ -324,6 +332,25 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
     expect(done.className).not.toContain('animate-pulse');
   });
 
+  it('renders rows in seq (issue) order, not array (arrival) order', () => {
+    // Simulates the out-of-order-arrival bug: a `tool_args_delta` for
+    // a later parallel call can land — and create its row — before an
+    // earlier call's own event, so the entries array ends up scrambled
+    // relative to the order the agent actually issued the calls. `seq` is
+    // the source of truth for display order; the array position is not.
+    const entries: ToolTimelineEntry[] = [
+      { id: 'third', name: 'run_code', round: 1, seq: 2, status: 'success' },
+      { id: 'first', name: 'web_search', round: 1, seq: 0, status: 'success' },
+      { id: 'second', name: 'file_read', round: 1, seq: 1, status: 'success' },
+    ];
+    renderInStore(<ToolTimelineBlock entries={entries} />);
+    const rows = screen.getAllByTestId('agent-timeline-row');
+    expect(rows).toHaveLength(3);
+    expect(rows[0].textContent).toContain('Searching the web');
+    expect(rows[1].textContent).toContain('Reading file');
+    expect(rows[2].textContent).toContain('Run Code');
+  });
+
   it('renders nothing for an empty timeline', () => {
     const { container } = renderInStore(<ToolTimelineBlock entries={[]} />);
     expect(container.querySelector('[data-testid="agent-task-insights"]')).toBeNull();
@@ -331,7 +358,7 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
 
   it('stays open while running and collapses once settled so a finished run does not dominate', () => {
     const running: ToolTimelineEntry[] = [
-      { id: 'r', name: 'web_search', round: 1, status: 'running' },
+      { id: 'r', name: 'web_search', round: 1, seq: 0, status: 'running' },
     ];
     const { rerender } = renderInStore(<ToolTimelineBlock entries={running} />);
     // In flight → the group is open so the live activity is visible.
@@ -340,7 +367,7 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
     // Settled (no running row) → collapsed by default; the rows stay in the DOM
     // one click away, but no longer flood the conversation.
     const settled: ToolTimelineEntry[] = [
-      { id: 'r', name: 'web_search', round: 1, status: 'success' },
+      { id: 'r', name: 'web_search', round: 1, seq: 0, status: 'success' },
     ];
     rerender(
       <Provider store={store}>
@@ -371,7 +398,7 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
   describe('agentic task insights — sticky user expand/collapse across turns', () => {
     it('keeps an explicit user expand across a new turn that starts and settles', () => {
       const turn1Settled: ToolTimelineEntry[] = [
-        { id: 't1', name: 'web_search', round: 1, status: 'success' },
+        { id: 't1', name: 'web_search', round: 1, seq: 0, status: 'success' },
       ];
       const { rerender } = renderInStore(<ToolTimelineBlock entries={turn1Settled} />);
       // Default: settled and collapsed (unchanged behaviour).
@@ -384,7 +411,7 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
       // A new turn/feedback starts streaming onto the SAME mounted block.
       const turn2Running: ToolTimelineEntry[] = [
         ...turn1Settled,
-        { id: 't2', name: 'file_read', round: 2, status: 'running' },
+        { id: 't2', name: 'file_read', round: 2, seq: 1, status: 'running' },
       ];
       rerender(
         <Provider store={store}>
@@ -397,7 +424,7 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
       // involuntarily re-collapse, wiping out the user's choice.
       const turn2Settled: ToolTimelineEntry[] = [
         ...turn1Settled,
-        { id: 't2', name: 'file_read', round: 2, status: 'success' },
+        { id: 't2', name: 'file_read', round: 2, seq: 1, status: 'success' },
       ];
       rerender(
         <Provider store={store}>
@@ -409,13 +436,13 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
 
     it('leaves the default open-while-running/collapsed-when-settled behaviour unchanged absent any user interaction', () => {
       const running: ToolTimelineEntry[] = [
-        { id: 'r', name: 'web_search', round: 1, status: 'running' },
+        { id: 'r', name: 'web_search', round: 1, seq: 0, status: 'running' },
       ];
       const { rerender } = renderInStore(<ToolTimelineBlock entries={running} />);
       expect(screen.getByTestId('agent-task-insights')).toHaveAttribute('open');
 
       const settled: ToolTimelineEntry[] = [
-        { id: 'r', name: 'web_search', round: 1, status: 'success' },
+        { id: 'r', name: 'web_search', round: 1, seq: 0, status: 'success' },
       ];
       rerender(
         <Provider store={store}>
@@ -427,7 +454,7 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
 
     it('also persists an explicit user collapse across a new turn (does not force it back open)', () => {
       const turn1Running: ToolTimelineEntry[] = [
-        { id: 't1', name: 'web_search', round: 1, status: 'running' },
+        { id: 't1', name: 'web_search', round: 1, seq: 0, status: 'running' },
       ];
       const { rerender } = renderInStore(<ToolTimelineBlock entries={turn1Running} />);
       expect(screen.getByTestId('agent-task-insights')).toHaveAttribute('open');
@@ -439,8 +466,8 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
       // A new turn starts running — the auto rule alone would force it back
       // open, but the user's explicit collapse must win.
       const turn2Running: ToolTimelineEntry[] = [
-        { id: 't1', name: 'web_search', round: 1, status: 'success' },
-        { id: 't2', name: 'file_read', round: 2, status: 'running' },
+        { id: 't1', name: 'web_search', round: 1, seq: 0, status: 'success' },
+        { id: 't2', name: 'file_read', round: 2, seq: 1, status: 'running' },
       ];
       rerender(
         <Provider store={store}>
@@ -457,6 +484,7 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
         id: 'd',
         name: 'web_search',
         round: 1,
+        seq: 0,
         status: 'success',
         argsBuffer: '{"query":"f1"}',
         result: 'Top result: https://openhuman.dev',
@@ -470,8 +498,8 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
   it('makes a row expandable on a result alone and omits the block without one', () => {
     const entries: ToolTimelineEntry[] = [
       // No argsBuffer / detail / subagent — the result is the only body.
-      { id: 'a', name: 'run_code', round: 1, status: 'success', result: 'exit 0' },
-      { id: 'b', name: 'run_code', round: 2, status: 'success' },
+      { id: 'a', name: 'run_code', round: 1, seq: 0, status: 'success', result: 'exit 0' },
+      { id: 'b', name: 'run_code', round: 2, seq: 0, status: 'success' },
     ];
     renderInStore(<ToolTimelineBlock entries={entries} expandAllRows />);
     const outputs = screen.getAllByTestId('tool-result-output');
@@ -481,7 +509,14 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
 
   it('renders the parent live response inside the panel under a Response heading', () => {
     const entries: ToolTimelineEntry[] = [
-      { id: 'r', name: 'web_search', round: 1, status: 'running', argsBuffer: '{"query":"f1"}' },
+      {
+        id: 'r',
+        name: 'web_search',
+        round: 1,
+        seq: 0,
+        status: 'running',
+        argsBuffer: '{"query":"f1"}',
+      },
     ];
     renderInStore(
       <ToolTimelineBlock
@@ -496,7 +531,7 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
 
   it('omits the Response block when there is no live response', () => {
     const entries: ToolTimelineEntry[] = [
-      { id: 'r', name: 'web_search', round: 1, status: 'running' },
+      { id: 'r', name: 'web_search', round: 1, seq: 0, status: 'running' },
     ];
     renderInStore(<ToolTimelineBlock entries={entries} />);
     expect(screen.queryByTestId('agent-live-response')).toBeNull();
@@ -504,7 +539,7 @@ describe('ToolTimelineBlock — agentic task insights surface', () => {
 
   it('strips a leaked <tool_call> envelope from the live response', () => {
     const entries: ToolTimelineEntry[] = [
-      { id: 'r', name: 'web_search', round: 1, status: 'running' },
+      { id: 'r', name: 'web_search', round: 1, seq: 0, status: 'running' },
     ];
     renderInStore(
       <ToolTimelineBlock
@@ -527,6 +562,7 @@ describe('ToolTimelineBlock — coalescing repeated rows', () => {
       id: `dup-${i}`,
       name: 'integrations_agent',
       round: 1,
+      seq: 0,
       status: 'success' as const,
     }));
     renderInStore(<ToolTimelineBlock entries={entries} />);
@@ -537,12 +573,12 @@ describe('ToolTimelineBlock — coalescing repeated rows', () => {
 
   it('does not merge across differing status or the live running row', () => {
     const entries: ToolTimelineEntry[] = [
-      { id: 'a', name: 'integrations_agent', round: 1, status: 'success' },
-      { id: 'b', name: 'integrations_agent', round: 1, status: 'success' },
+      { id: 'a', name: 'integrations_agent', round: 1, seq: 0, status: 'success' },
+      { id: 'b', name: 'integrations_agent', round: 1, seq: 0, status: 'success' },
       // Different status breaks the run.
-      { id: 'c', name: 'integrations_agent', round: 1, status: 'error' },
+      { id: 'c', name: 'integrations_agent', round: 1, seq: 0, status: 'error' },
       // The live running row is never folded away.
-      { id: 'd', name: 'integrations_agent', round: 1, status: 'running' },
+      { id: 'd', name: 'integrations_agent', round: 1, seq: 0, status: 'running' },
     ];
     renderInStore(<ToolTimelineBlock entries={entries} />);
     // success×2 (merged) + error (single) + running (single) = 3 rows.
@@ -554,8 +590,8 @@ describe('ToolTimelineBlock — coalescing repeated rows', () => {
 
   it('never merges rows that carry a unique result body', () => {
     const entries: ToolTimelineEntry[] = [
-      { id: 'a', name: 'run_code', round: 1, status: 'success', result: 'exit 0' },
-      { id: 'b', name: 'run_code', round: 1, status: 'success', result: 'exit 1' },
+      { id: 'a', name: 'run_code', round: 1, seq: 0, status: 'success', result: 'exit 0' },
+      { id: 'b', name: 'run_code', round: 1, seq: 0, status: 'success', result: 'exit 1' },
     ];
     renderInStore(<ToolTimelineBlock entries={entries} expandAllRows />);
     // Both keep their own row — distinct results are never coalesced.
@@ -570,6 +606,7 @@ describe('ToolTimelineBlock — subagent rendering', () => {
       id: 'tid:subagent:sub-1:researcher',
       name: 'subagent:researcher',
       round: 1,
+      seq: 0,
       status: 'running',
       subagent: {
         taskId: 'sub-1',
@@ -593,6 +630,7 @@ describe('ToolTimelineBlock — subagent rendering', () => {
       id: 'plain',
       name: 'list_threads',
       round: 0,
+      seq: 0,
       status: 'success',
     };
     renderInStore(<ToolTimelineBlock entries={[entry]} />);
@@ -620,6 +658,7 @@ describe('ToolTimelineBlock — worker thread ref status propagation', () => {
       id: `tid:subagent:task-42:researcher:${status}`,
       name: 'subagent:researcher',
       round: 1,
+      seq: 0,
       status,
       detail: WORKER_REF_DETAIL,
     };
@@ -664,6 +703,7 @@ describe('ToolTimelineBlock — compact chat mode (onViewDetails)', () => {
       id: 'tl-1',
       name: 'agent_prepare_context',
       round: 1,
+      seq: 0,
       status: 'success',
       detail: 'fetch X',
       result: 'Prepared context from 3 sources.',
@@ -673,6 +713,7 @@ describe('ToolTimelineBlock — compact chat mode (onViewDetails)', () => {
       id: 'sa-1',
       name: 'subagent:researcher',
       round: 1,
+      seq: 0,
       status: 'running',
       subagent: {
         taskId: 'task-1',
@@ -713,6 +754,7 @@ describe('ToolTimelineBlock — compact chat mode (onViewDetails)', () => {
             id: 'sa-done',
             name: 'subagent:researcher',
             round: 1,
+            seq: 0,
             status: 'success',
             subagent: {
               taskId: 'task-2',
diff --git a/app/src/features/conversations/timeline/ConversationTimeline.test.tsx b/app/src/features/conversations/timeline/ConversationTimeline.test.tsx
index 96fb5a504..6a5df2877 100644
--- a/app/src/features/conversations/timeline/ConversationTimeline.test.tsx
+++ b/app/src/features/conversations/timeline/ConversationTimeline.test.tsx
@@ -33,13 +33,14 @@ function agentMsg(id: string, content: string): ThreadMessage {
   };
 }
 function tool(id: string, name: string, round = 0): ToolTimelineEntry {
-  return { id, name, round, status: 'success' };
+  return { id, name, round, seq: 0, status: 'success' };
 }
 function subagentRow(id: string, taskId: string): ToolTimelineEntry {
   return {
     id,
     name: 'subagent:researcher',
     round: 0,
+    seq: 0,
     status: 'running',
     subagent: { taskId, agentId: 'researcher', toolCalls: [] },
   };
diff --git a/app/src/features/conversations/timeline/selectors.test.ts b/app/src/features/conversations/timeline/selectors.test.ts
index 108cb2af0..64b63b5e8 100644
--- a/app/src/features/conversations/timeline/selectors.test.ts
+++ b/app/src/features/conversations/timeline/selectors.test.ts
@@ -42,13 +42,14 @@ function tool(
   round = 0,
   status: ToolTimelineEntry['status'] = 'success'
 ): ToolTimelineEntry {
-  return { id, name, round, status };
+  return { id, name, round, seq: 0, status };
 }
 function subagentRow(id: string, taskId: string, round = 0): ToolTimelineEntry {
   return {
     id,
     name: 'subagent:researcher',
     round,
+    seq: 0,
     status: 'running',
     subagent: { taskId, agentId: 'researcher', toolCalls: [] },
   };
diff --git a/app/src/features/human/SubMascotLayer.test.tsx b/app/src/features/human/SubMascotLayer.test.tsx
index 928992983..c2a0285cd 100644
--- a/app/src/features/human/SubMascotLayer.test.tsx
+++ b/app/src/features/human/SubMascotLayer.test.tsx
@@ -17,6 +17,7 @@ function subagentEntry(overrides: Partial<ToolTimelineEntry> = {}): ToolTimeline
     id: 'thread-1:subagent:sub-1:researcher',
     name: 'subagent:researcher',
     round: 1,
+    seq: 0,
     status: 'running',
     detail: 'Research the relevant docs.',
     subagent: {
@@ -33,7 +34,7 @@ function subagentEntry(overrides: Partial<ToolTimelineEntry> = {}): ToolTimeline
 describe('subMascotModelsFromTimeline', () => {
   it('builds visible models only from subagent timeline rows', () => {
     const models = subMascotModelsFromTimeline([
-      { id: 'thread-1:tool:search', name: 'web_search', round: 1, status: 'running' },
+      { id: 'thread-1:tool:search', name: 'web_search', round: 1, seq: 0, status: 'running' },
       subagentEntry(),
     ]);
 
@@ -190,7 +191,7 @@ describe('<SubMascotLayer />', () => {
   it('renders nothing when no subagent rows are present', () => {
     const { container } = render(
       <SubMascotLayer
-        entries={[{ id: 'tool-1', name: 'web_search', round: 1, status: 'running' }]}
+        entries={[{ id: 'tool-1', name: 'web_search', round: 1, seq: 0, status: 'running' }]}
       />
     );
 
diff --git a/app/src/pages/__tests__/Conversations.render.test.tsx b/app/src/pages/__tests__/Conversations.render.test.tsx
index c4df668e6..060e8bb11 100644
--- a/app/src/pages/__tests__/Conversations.render.test.tsx
+++ b/app/src/pages/__tests__/Conversations.render.test.tsx
@@ -665,7 +665,9 @@ describe('Conversations — smoke render (#1123 welcome-lock removal)', () => {
       store!.dispatch(
         setTurnTimelinesForThread({
           threadId: thread.id,
-          timelines: { 'req-1': [{ id: 'tc-1', name: 'read_file', round: 0, status: 'success' }] },
+          timelines: {
+            'req-1': [{ id: 'tc-1', name: 'read_file', round: 0, seq: 0, status: 'success' }],
+          },
         })
       );
     });
@@ -1567,7 +1569,7 @@ describe('Conversations — smoke render (#1123 welcome-lock removal)', () => {
         store!.dispatch(
           setToolTimelineForThread({
             threadId: thread.id,
-            entries: [{ id: 'tl-1', name: 'web_fetch', round: 1, status: 'running' }],
+            entries: [{ id: 'tl-1', name: 'web_fetch', round: 1, seq: 0, status: 'running' }],
           })
         );
       });
@@ -1703,7 +1705,7 @@ describe('Conversations — smoke render (#1123 welcome-lock removal)', () => {
         store!.dispatch(
           setToolTimelineForThread({
             threadId: 'some-other-thread',
-            entries: [{ id: 'other-1', name: 'web_fetch', round: 1, status: 'running' }],
+            entries: [{ id: 'other-1', name: 'web_fetch', round: 1, seq: 0, status: 'running' }],
           })
         );
       });
@@ -2091,11 +2093,12 @@ describe('Conversations — agent task insights panel anchoring (#3717 Bug 2)',
         setToolTimelineForThread({
           threadId: thread.id,
           entries: [
-            { id: 'tl-1', name: 'web_fetch', round: 1, status: 'success' },
+            { id: 'tl-1', name: 'web_fetch', round: 1, seq: 0, status: 'success' },
             {
               id: 'sa-1',
               name: 'subagent:researcher',
               round: 1,
+              seq: 0,
               status: 'running',
               subagent: { taskId: 'task-1', agentId: 'researcher', toolCalls: [] },
             },
@@ -2187,7 +2190,7 @@ describe('Conversations — agent task insights panel anchoring (#3717 Bug 2)',
       store!.dispatch(
         setToolTimelineForThread({
           threadId: thread.id,
-          entries: [{ id: 'tl-1', name: 'web_fetch', round: 1, status: 'success' }],
+          entries: [{ id: 'tl-1', name: 'web_fetch', round: 1, seq: 0, status: 'success' }],
         })
       );
     });
@@ -2243,7 +2246,7 @@ describe('Conversations — agent task insights panel anchoring (#3717 Bug 2)',
       store!.dispatch(
         setToolTimelineForThread({
           threadId: thread.id,
-          entries: [{ id: 'tl-1', name: 'web_fetch', round: 1, status: 'running' }],
+          entries: [{ id: 'tl-1', name: 'web_fetch', round: 1, seq: 0, status: 'running' }],
         })
       );
     });
@@ -2364,7 +2367,7 @@ describe('Conversations — agent task insights panel anchoring (#3717 Bug 2)',
       store!.dispatch(
         setToolTimelineForThread({
           threadId: thread.id,
-          entries: [{ id: 'tl-1', name: 'web_fetch', round: 1, status: 'cancelled' }],
+          entries: [{ id: 'tl-1', name: 'web_fetch', round: 1, seq: 0, status: 'cancelled' }],
         })
       );
     });
diff --git a/app/src/pages/dev/AgentInsightsPreview.tsx b/app/src/pages/dev/AgentInsightsPreview.tsx
index 9ff2cd129..7aada9d23 100644
--- a/app/src/pages/dev/AgentInsightsPreview.tsx
+++ b/app/src/pages/dev/AgentInsightsPreview.tsx
@@ -24,6 +24,7 @@ const RUNNING_ENTRIES: ToolTimelineEntry[] = [
     id: 's-slack',
     name: 'subagent:integrations_agent',
     round: 1,
+    seq: 0,
     status: 'running',
     sourceToolName: 'slack',
     subagent: {
@@ -44,6 +45,7 @@ const RUNNING_ENTRIES: ToolTimelineEntry[] = [
     id: 'e-search',
     name: 'web_search',
     round: 1,
+    seq: 1,
     status: 'success',
     argsBuffer: JSON.stringify({ query: 'monaco gp 2026 results' }),
   },
@@ -51,6 +53,7 @@ const RUNNING_ENTRIES: ToolTimelineEntry[] = [
     id: 'e-fetch1',
     name: 'web_fetch',
     round: 1,
+    seq: 2,
     status: 'success',
     argsBuffer: JSON.stringify({ url: 'https://news-gazette.com/sport/f1-monaco' }),
   },
@@ -58,6 +61,7 @@ const RUNNING_ENTRIES: ToolTimelineEntry[] = [
     id: 'e-fetch2',
     name: 'web_fetch',
     round: 1,
+    seq: 3,
     status: 'success',
     argsBuffer: JSON.stringify({ url: 'https://example.org/standings' }),
   },
@@ -65,6 +69,7 @@ const RUNNING_ENTRIES: ToolTimelineEntry[] = [
     id: 'e-shell',
     name: 'shell',
     round: 2,
+    seq: 4,
     status: 'success',
     argsBuffer: JSON.stringify({ command: 'cat report.py | head -20' }),
   },
@@ -72,6 +77,7 @@ const RUNNING_ENTRIES: ToolTimelineEntry[] = [
     id: 'e-err',
     name: 'file_read',
     round: 2,
+    seq: 5,
     status: 'error',
     argsBuffer: JSON.stringify({ path: '/tmp/missing.txt' }),
   },
diff --git a/app/src/store/__tests__/chatRuntimeSlice.subagentStream.test.ts b/app/src/store/__tests__/chatRuntimeSlice.subagentStream.test.ts
index 0dd40bde4..01621bf92 100644
--- a/app/src/store/__tests__/chatRuntimeSlice.subagentStream.test.ts
+++ b/app/src/store/__tests__/chatRuntimeSlice.subagentStream.test.ts
@@ -18,6 +18,7 @@ function withSubagentRow(): ReturnType<typeof reducer> {
     id: ROW_ID,
     name: 'subagent:researcher',
     round: 1,
+    seq: 0,
     status: 'running',
     subagent: { taskId: 'sub-1', agentId: 'researcher', toolCalls: [], transcript: [] },
   };
diff --git a/app/src/store/__tests__/chatRuntimeSlice.test.ts b/app/src/store/__tests__/chatRuntimeSlice.test.ts
index 36cf57ee3..d64713865 100644
--- a/app/src/store/__tests__/chatRuntimeSlice.test.ts
+++ b/app/src/store/__tests__/chatRuntimeSlice.test.ts
@@ -118,6 +118,7 @@ describe('chatRuntimeSlice', () => {
             id: 'call-1',
             name: 'search',
             round: 1,
+            seq: 0,
             status: 'running',
             argsBuffer: '{"q":"hello"}',
           },
@@ -126,7 +127,14 @@ describe('chatRuntimeSlice', () => {
     );
 
     expect(withTimeline.toolTimelineByThread['thread-1']).toEqual([
-      { id: 'call-1', name: 'search', round: 1, status: 'running', argsBuffer: '{"q":"hello"}' },
+      {
+        id: 'call-1',
+        name: 'search',
+        round: 1,
+        seq: 0,
+        status: 'running',
+        argsBuffer: '{"q":"hello"}',
+      },
     ]);
 
     const cleared = reducer(withTimeline, clearToolTimelineForThread({ threadId: 'thread-1' }));
@@ -223,6 +231,7 @@ describe('chatRuntimeSlice', () => {
         id: 'tc-1',
         name: 'shell',
         round: 3,
+        seq: 0,
         status: 'running',
         argsBuffer: '{"cmd":"ls"}',
         displayName: undefined,
@@ -478,7 +487,7 @@ describe('chatRuntimeSlice', () => {
       ),
       setToolTimelineForThread({
         threadId: 'thread-1',
-        entries: [{ id: 'call-1', name: 'search', round: 1, status: 'running' }],
+        entries: [{ id: 'call-1', name: 'search', round: 1, seq: 0, status: 'running' }],
       })
     );
 
@@ -943,9 +952,73 @@ describe('toolCallReceived (Phase 3 reducer-side merge)', () => {
     const rows = state.toolTimelineByThread['t1'];
     expect(rows).toHaveLength(1);
     expect(rows[0].round).toBe(1);
+    // The row keeps its original `seq` across the upsert — issue order is set
+    // once, at first creation, and must not shift on a later update event.
+    expect(rows[0].seq).toBe(0);
     // Processing pointer is recorded once for the stable callId.
     expect(state.processingByThread['t1']).toHaveLength(1);
   });
+
+  it('assigns a monotonically increasing seq to each newly created row per thread', () => {
+    let state = reducer(
+      undefined,
+      toolCallReceived({ threadId: 't1', round: 0, toolName: 'search', toolCallId: 'c1' })
+    );
+    state = reducer(
+      state,
+      toolCallReceived({ threadId: 't1', round: 0, toolName: 'search', toolCallId: 'c2' })
+    );
+    state = reducer(
+      state,
+      toolCallReceived({ threadId: 't1', round: 0, toolName: 'search', toolCallId: 'c3' })
+    );
+    const rows = state.toolTimelineByThread['t1'];
+    expect(rows.map(r => r.seq)).toEqual([0, 1, 2]);
+    // A different thread gets its own independent counter.
+    state = reducer(
+      state,
+      toolCallReceived({ threadId: 't2', round: 0, toolName: 'search', toolCallId: 'd1' })
+    );
+    expect(state.toolTimelineByThread['t2'][0].seq).toBe(0);
+  });
+
+  it('keeps the seq from first creation when args arrive before the tool_call event', () => {
+    // A `tool_args_delta` for call B can race ahead of call A's `tool_call`
+    // event when the agent issues two parallel calls in one turn. The row
+    // created by whichever event lands first gets seq 0; the row's `seq`
+    // must not change when the (later) sibling event for the same call
+    // arrives and only updates the existing row in place.
+    let state = reducer(
+      undefined,
+      toolArgsDeltaReceived({
+        threadId: 't1',
+        round: 0,
+        delta: '{"q":"b"}',
+        toolName: 'search',
+        toolCallId: 'call-b',
+      })
+    );
+    state = reducer(
+      state,
+      toolCallReceived({ threadId: 't1', round: 0, toolName: 'search', toolCallId: 'call-a' })
+    );
+    // call-b's row was created first (seq 0) even though call-a's
+    // `tool_call` event is semantically "first" in the pair — the point is
+    // that whichever event creates the row locks in the seq, and a later
+    // `toolCallReceived` for that same id does not reassign it.
+    state = reducer(
+      state,
+      toolCallReceived({ threadId: 't1', round: 0, toolName: 'search', toolCallId: 'call-b' })
+    );
+    const rows = state.toolTimelineByThread['t1'];
+    const rowB = rows.find(r => r.id === 'call-b');
+    const rowA = rows.find(r => r.id === 'call-a');
+    expect(rowB?.seq).toBe(0);
+    expect(rowA?.seq).toBe(1);
+    // Re-receiving call-b's tool_call event (args arrived first) must not
+    // bump its seq to a later value.
+    expect(rowB?.seq).toBe(0);
+  });
 });
 
 describe('toolResultReceived (Phase 3 reducer-side merge)', () => {
@@ -954,7 +1027,7 @@ describe('toolResultReceived (Phase 3 reducer-side merge)', () => {
       undefined,
       setToolTimelineForThread({
         threadId: 't1',
-        entries: [{ id: 'call-1', name: 'shell', round: 0, status: 'running' }],
+        entries: [{ id: 'call-1', name: 'shell', round: 0, seq: 0, status: 'running' }],
       })
     );
 
@@ -976,7 +1049,7 @@ describe('toolResultReceived (Phase 3 reducer-side merge)', () => {
     });
   });
 
-  it('falls back to the newest running row of the same name+round when no id matches', () => {
+  it('falls back to the (only) running row of the same name+round when no id matches', () => {
     const state = reducer(
       withRunningRow(),
       toolResultReceived({ threadId: 't1', round: 0, toolName: 'shell', success: false })
@@ -984,6 +1057,42 @@ describe('toolResultReceived (Phase 3 reducer-side merge)', () => {
     expect(state.toolTimelineByThread['t1'][0].status).toBe('error');
   });
 
+  it('FIFO: settles the oldest (not newest) running row of the same name+round when no id matches', () => {
+    // Two parallel `get_tool_contract` calls with the same name+round and no
+    // toolCallId on the result (mirrors a legacy/incomplete socket payload).
+    // The fallback must settle the row that was issued FIRST (lowest seq),
+    // not the most recently created one — otherwise a result for the first
+    // call can incorrectly settle the second call's still-running row.
+    let state = reducer(
+      undefined,
+      setToolTimelineForThread({
+        threadId: 't1',
+        entries: [
+          { id: 'call-old', name: 'get_tool_contract', round: 0, seq: 0, status: 'running' },
+          { id: 'call-new', name: 'get_tool_contract', round: 0, seq: 1, status: 'running' },
+        ],
+      })
+    );
+    state = reducer(
+      state,
+      toolResultReceived({
+        threadId: 't1',
+        round: 0,
+        toolName: 'get_tool_contract',
+        success: true,
+        output: 'first result',
+      })
+    );
+    const rows = state.toolTimelineByThread['t1'];
+    const oldRow = rows.find(r => r.id === 'call-old');
+    const newRow = rows.find(r => r.id === 'call-new');
+    expect(oldRow?.status).toBe('success');
+    expect(oldRow?.result).toBe('first result');
+    // The newer call's row is untouched — still running, awaiting its own result.
+    expect(newRow?.status).toBe('running');
+    expect(newRow?.result).toBeUndefined();
+  });
+
   it('is a no-op when nothing matches (mirrors the provider changed-guard)', () => {
     const before = withRunningRow();
     const after = reducer(
@@ -1105,6 +1214,7 @@ describe('subagent event reducers (Phase 3)', () => {
             id: 'spawn-1',
             name: 'spawn_subagent',
             round: 0,
+            seq: 0,
             status: 'running',
             detail: 'go research',
           },
@@ -1259,7 +1369,9 @@ describe('toolArgsDeltaReceived (Phase 3 reducer-side merge)', () => {
       undefined,
       setToolTimelineForThread({
         threadId: 't1',
-        entries: [{ id: 'r1', name: 'search', round: 0, status: 'running', argsBuffer: '{' }],
+        entries: [
+          { id: 'r1', name: 'search', round: 0, seq: 0, status: 'running', argsBuffer: '{' },
+        ],
       })
     );
     state = reducer(
diff --git a/app/src/store/chatRuntimeSlice.test.ts b/app/src/store/chatRuntimeSlice.test.ts
index 769a8baaa..316c7da7f 100644
--- a/app/src/store/chatRuntimeSlice.test.ts
+++ b/app/src/store/chatRuntimeSlice.test.ts
@@ -417,6 +417,7 @@ describe('chatRuntimeSlice queue status', () => {
             id: 't-dup:subagent:run-1:spawn_subagent',
             name: 'subagent:tinyplace_agent',
             round: 1,
+            seq: 0,
             status: 'running',
             subagent: { taskId: 'run-1', agentId: 'tinyplace_agent', toolCalls: [] },
           },
@@ -499,6 +500,7 @@ describe('hydrateRuntimeFromSnapshot — sub-agent prose persistence', () => {
             id: 't9:subagent:task-x:spawn_subagent',
             name: 'subagent:researcher',
             round: 1,
+            seq: 0,
             status: 'running',
             subagent: {
               taskId: 'task-x',
@@ -655,8 +657,15 @@ describe('hydrateRuntimeFromSnapshot — live-driver guard', () => {
       setToolTimelineForThread({
         threadId: 't-live',
         entries: [
-          { id: 'c1', name: 'web_search', round: 1, status: 'success', result: 'found 3 hits' },
-          { id: 'c2', name: 'read_file', round: 2, status: 'running' },
+          {
+            id: 'c1',
+            name: 'web_search',
+            round: 1,
+            seq: 0,
+            status: 'success',
+            result: 'found 3 hits',
+          },
+          { id: 'c2', name: 'read_file', round: 2, seq: 0, status: 'running' },
         ],
       })
     );
@@ -803,7 +812,7 @@ describe('hydrateRuntimeFromSnapshot — streaming/timeline race guard', () => {
     store.dispatch(
       setToolTimelineForThread({
         threadId: 't-settled',
-        entries: [{ id: 'c-live', name: 'read_file', round: 1, status: 'success' }],
+        entries: [{ id: 'c-live', name: 'read_file', round: 1, seq: 0, status: 'success' }],
       })
     );
 
@@ -830,7 +839,7 @@ describe('hydrateRuntimeFromSnapshot — streaming/timeline race guard', () => {
     store.dispatch(
       setToolTimelineForThread({
         threadId: 't-crashed',
-        entries: [{ id: 'c-stale', name: 'read_file', round: 1, status: 'running' }],
+        entries: [{ id: 'c-stale', name: 'read_file', round: 1, seq: 0, status: 'running' }],
       })
     );
 
diff --git a/app/src/store/chatRuntimeSlice.ts b/app/src/store/chatRuntimeSlice.ts
index d0cad6d80..7e01b5fbf 100644
--- a/app/src/store/chatRuntimeSlice.ts
+++ b/app/src/store/chatRuntimeSlice.ts
@@ -287,6 +287,16 @@ export interface ToolTimelineEntry {
   id: string;
   name: string;
   round: number;
+  /**
+   * Monotonic per-thread issue-order index, assigned once when the row is
+   * FIRST created (by `toolCallReceived`, `toolArgsDeltaReceived`, or
+   * `subagentSpawned`) from {@link ChatRuntimeState.toolTimelineSeqByThread}.
+   * Unlike arrival order — which a `tool_args_delta` for a later parallel
+   * call can race ahead of — `seq` reflects the order the agent actually
+   * issued the calls, so the timeline can be sorted deterministically
+   * (see `ToolTimelineBlock`) regardless of socket delivery order.
+   */
+  seq: number;
   status: ToolTimelineEntryStatus;
   argsBuffer?: string;
   displayName?: string;
@@ -612,6 +622,15 @@ interface ChatRuntimeState {
    */
   parallelRequestThreads: Record<string, string>;
   toolTimelineByThread: Record<string, ToolTimelineEntry[]>;
+  /**
+   * Per-thread monotonic counter backing {@link ToolTimelineEntry.seq}. Bumped
+   * once per NEW row created in {@link toolTimelineByThread} (never on an
+   * update to an existing row), so `seq` always reflects issue order even
+   * when socket events for parallel tool calls arrive out of order. Reset
+   * alongside the timeline itself so a new turn/thread starts counting from
+   * zero.
+   */
+  toolTimelineSeqByThread: Record<string, number>;
   /**
    * Per-turn tool timelines for *past* (settled) turns of a thread, keyed
    * `threadId -> requestId -> entries`. Hydrated from `turn_state_history` on
@@ -705,6 +724,7 @@ const initialState: ChatRuntimeState = {
   parallelStreamsByThread: {},
   parallelRequestThreads: {},
   toolTimelineByThread: {},
+  toolTimelineSeqByThread: {},
   turnTimelinesByThread: {},
   processingByThread: {},
   taskBoardByThread: {},
@@ -841,11 +861,23 @@ function subagentActivityFromPersisted(activity: PersistedSubagentActivity): Sub
   };
 }
 
-function toolTimelineFromPersisted(entry: PersistedToolTimelineEntry): ToolTimelineEntry {
+/**
+ * `seq` defaults to the array index the caller maps over — persisted
+ * `toolTimeline` order IS issue order (the core appends rows as it issues
+ * calls), so the index is a faithful stand-in for the live monotonic
+ * counter. Callers that hydrate the *live* timeline (as opposed to a past,
+ * settled turn) additionally seed {@link ChatRuntimeState.toolTimelineSeqByThread}
+ * with the row count so subsequent live events keep counting up from there.
+ */
+function toolTimelineFromPersisted(
+  entry: PersistedToolTimelineEntry,
+  seq: number
+): ToolTimelineEntry {
   return {
     id: entry.id,
     name: entry.name,
     round: entry.round,
+    seq,
     status: entry.status,
     argsBuffer: entry.argsBuffer,
     displayName: entry.displayName,
@@ -917,7 +949,7 @@ function timelineStatusFromRun(status: AgentRun['status']): ToolTimelineEntrySta
   }
 }
 
-function timelineEntryFromRun(run: AgentRun): ToolTimelineEntry | null {
+function timelineEntryFromRun(run: AgentRun, seq: number): ToolTimelineEntry | null {
   if (!['subagent', 'worker_thread', 'workflow_child', 'team_member'].includes(run.kind)) {
     return null;
   }
@@ -931,6 +963,7 @@ function timelineEntryFromRun(run: AgentRun): ToolTimelineEntry | null {
     id: `subagent:${run.id}`,
     name: `subagent:${agentId}`,
     round: 0,
+    seq,
     status: timelineStatusFromRun(run.status),
     displayName,
     detail: run.summary ?? run.error ?? undefined,
@@ -1035,6 +1068,7 @@ const chatRuntimeSlice = createSlice({
     },
     clearToolTimelineForThread: (state, action: PayloadAction<{ threadId: string }>) => {
       delete state.toolTimelineByThread[action.payload.threadId];
+      delete state.toolTimelineSeqByThread[action.payload.threadId];
       delete state.processingByThread[action.payload.threadId];
     },
     /**
@@ -1122,11 +1156,14 @@ const chatRuntimeSlice = createSlice({
           detail: displayDetail ?? prev.detail,
         });
       } else {
+        const seq = state.toolTimelineSeqByThread[threadId] ?? 0;
+        state.toolTimelineSeqByThread[threadId] = seq + 1;
         entries.push(
           decorateEntry({
             id: rowId,
             name: toolName,
             round,
+            seq,
             status: 'running',
             displayName: displayLabel,
             detail: displayDetail,
@@ -1176,7 +1213,14 @@ const chatRuntimeSlice = createSlice({
           return;
         }
       }
-      for (let i = entries.length - 1; i >= 0; i -= 1) {
+      // FIFO, not LIFO: entries are appended in `seq` (issue) order and never
+      // reordered in place, so scanning forward from index 0 finds the OLDEST
+      // still-running row of this name+round — settling the call that was
+      // actually issued first. A backward (newest-first) scan mis-pairs a
+      // result with the wrong row when 2+ calls with the same name are
+      // in-flight in parallel (e.g. `get_tool_contract` ×2) and results land
+      // out of order.
+      for (let i = 0; i < entries.length; i += 1) {
         const entry = entries[i];
         if (entry.status === 'running' && entry.name === toolName && entry.round === round) {
           entry.status = status;
@@ -1272,11 +1316,14 @@ const chatRuntimeSlice = createSlice({
           name: prev.name.length === 0 && toolName ? toolName : prev.name,
         });
       } else {
+        const seq = state.toolTimelineSeqByThread[threadId] ?? 0;
+        state.toolTimelineSeqByThread[threadId] = seq + 1;
         entries.push(
           decorateEntry({
             id: toolCallId ?? '',
             name: toolName ?? '',
             round,
+            seq,
             status: 'running',
             argsBuffer: delta,
           })
@@ -1326,11 +1373,14 @@ const chatRuntimeSlice = createSlice({
         const spawnIdx = entries.findIndex(e => e.id === pending.spawnEntryId);
         if (spawnIdx >= 0) entries.splice(spawnIdx, 1);
       }
+      const seq = state.toolTimelineSeqByThread[threadId] ?? 0;
+      state.toolTimelineSeqByThread[threadId] = seq + 1;
       entries.push(
         decorateEntry({
           id: rowId,
           name: `subagent:${agentId}`,
           round,
+          seq,
           status: 'running',
           detail: pending.prompt,
           sourceToolName: pending.sourceToolName,
@@ -1818,6 +1868,7 @@ const chatRuntimeSlice = createSlice({
         delete state.parallelStreamsByThread[action.payload.threadId];
       }
       delete state.toolTimelineByThread[action.payload.threadId];
+      delete state.toolTimelineSeqByThread[action.payload.threadId];
       delete state.processingByThread[action.payload.threadId];
       delete state.taskBoardByThread[action.payload.threadId];
       delete state.inferenceTurnLifecycleByThread[action.payload.threadId];
@@ -1840,6 +1891,7 @@ const chatRuntimeSlice = createSlice({
       state.parallelStreamsByThread = {};
       state.parallelRequestThreads = {};
       state.toolTimelineByThread = {};
+      state.toolTimelineSeqByThread = {};
       state.turnTimelinesByThread = {};
       state.processingByThread = {};
       state.taskBoardByThread = {};
@@ -2009,8 +2061,14 @@ const chatRuntimeSlice = createSlice({
           // (no-op for an already-completed snapshot whose rows are terminal).
           state.toolTimelineByThread[threadId] = preserveLiveSubagentProse(
             state.toolTimelineByThread[threadId],
-            snapshot.toolTimeline.map(toolTimelineFromPersisted).map(settleOrphanedTimelineEntry)
+            snapshot.toolTimeline
+              .map((e, seq) => toolTimelineFromPersisted(e, seq))
+              .map(settleOrphanedTimelineEntry)
           );
+          // Persisted order is issue order — seed the live counter with the
+          // row count so events arriving after this hydration keep counting
+          // up rather than restarting at 0 and colliding with existing seqs.
+          state.toolTimelineSeqByThread[threadId] = snapshot.toolTimeline.length;
         }
         state.processingByThread[threadId] = snapshot.transcript ?? [];
         return;
@@ -2040,8 +2098,11 @@ const chatRuntimeSlice = createSlice({
 
       state.toolTimelineByThread[threadId] = preserveLiveSubagentProse(
         state.toolTimelineByThread[threadId],
-        snapshot.toolTimeline.map(toolTimelineFromPersisted)
+        snapshot.toolTimeline.map((e, seq) => toolTimelineFromPersisted(e, seq))
       );
+      // Persisted order is issue order — seed the live counter with the row
+      // count so events arriving after this hydration keep counting up.
+      state.toolTimelineSeqByThread[threadId] = snapshot.toolTimeline.length;
       state.processingByThread[threadId] = snapshot.transcript ?? [];
     },
     /**
@@ -2065,8 +2126,13 @@ const chatRuntimeSlice = createSlice({
         existing.map(entry => entry.subagent?.taskId).filter(Boolean) as string[]
       );
       for (const run of runs) {
-        const entry = timelineEntryFromRun(run);
+        // Ledger rows are historical/durable, not live-issued — assign the
+        // next counter value like any other newly-created row so they still
+        // get a stable, monotonically increasing `seq` for sorting.
+        const seq = state.toolTimelineSeqByThread[threadId] ?? 0;
+        const entry = timelineEntryFromRun(run, seq);
         if (!entry || byId.has(entry.id) || liveTaskIds.has(run.id)) continue;
+        state.toolTimelineSeqByThread[threadId] = seq + 1;
         byId.set(entry.id, entry);
       }
       state.toolTimelineByThread[threadId] = Array.from(byId.values());
@@ -2200,7 +2266,9 @@ export const fetchAndHydrateTurnHistory = createAsyncThunk(
       for (const turn of history.slice(1)) {
         if (turn.lifecycle !== 'completed' && turn.lifecycle !== 'interrupted') continue;
         if (!turn.requestId || turn.toolTimeline.length === 0) continue;
-        timelines[turn.requestId] = turn.toolTimeline.map(toolTimelineFromPersisted);
+        timelines[turn.requestId] = turn.toolTimeline.map((e, seq) =>
+          toolTimelineFromPersisted(e, seq)
+        );
       }
       turnStateLog(
         'hydrated turn history thread=%s turns=%d',
diff --git a/app/src/utils/__tests__/toolTimelineFormatting.test.ts b/app/src/utils/__tests__/toolTimelineFormatting.test.ts
index a08f28bec..0ccb87609 100644
--- a/app/src/utils/__tests__/toolTimelineFormatting.test.ts
+++ b/app/src/utils/__tests__/toolTimelineFormatting.test.ts
@@ -14,7 +14,7 @@ import {
 } from '../toolTimelineFormatting';
 
 function entry(overrides: Partial<ToolTimelineEntry>): ToolTimelineEntry {
-  return { id: 'x', name: 'delegate_notion', round: 1, status: 'running', ...overrides };
+  return { id: 'x', name: 'delegate_notion', round: 1, seq: 0, status: 'running', ...overrides };
 }
 
 describe('formatTimelineEntry', () => {
diff --git a/app/src/utils/toolTimelineFormatting.agentPrepareContext.test.ts b/app/src/utils/toolTimelineFormatting.agentPrepareContext.test.ts
index 1c95178b5..a892b230e 100644
--- a/app/src/utils/toolTimelineFormatting.agentPrepareContext.test.ts
+++ b/app/src/utils/toolTimelineFormatting.agentPrepareContext.test.ts
@@ -4,7 +4,7 @@ import type { ToolTimelineEntry } from '../store/chatRuntimeSlice';
 import { formatTimelineEntry, formatToolName } from './toolTimelineFormatting';
 
 function entry(partial: Partial<ToolTimelineEntry> & { name: string }): ToolTimelineEntry {
-  return { id: 'e1', round: 0, status: 'running', ...partial };
+  return { id: 'e1', round: 0, seq: 0, status: 'running', ...partial };
 }
 
 describe('toolTimelineFormatting — agent_prepare_context / context_scout', () => {