feat: show sub-workflow agents and lifecycle in the Activity panel

Deep agent resolution in the sidecar now walks sub-workflow nodes so
nested agents carry subworkflowNodeId and subworkflowName on activity
events. New subworkflow-started / subworkflow-completed activity types
let the frontend track sub-workflow lifecycle.

The Activity panel groups nested agents under collapsible sub-workflow
cards with status badges, accent-colored left borders, and smooth
expand/collapse transitions. Cards auto-expand when a sub-workflow
starts running. Workflows without sub-workflow nodes render identically
to before.

Extracted AgentRow, SubWorkflowGroup, and shared accent constants to
a new components/activity/ feature directory. Added
resolveWorkflowAgentHierarchy and buildGroupedActivityRows for
hierarchical activity grouping with dynamic fallback for unresolved
sub-workflow agents.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/AryxAppService.ts

@@ -2004,7 +2004,7 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     const session = this.requireSession(workspace, sessionId);
     const activityType = event.activityType;
     let nextRun: SessionRunRecord | undefined;
-    if (activityType !== 'completed') {
+    if (activityType === 'thinking' || activityType === 'tool-calling' || activityType === 'handoff') {
       nextRun = this.updateSessionRun(session, requestId, (run) =>
         appendRunActivityEvent(run, {
           activityType,
@@ -2032,6 +2032,8 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
       activityType: event.activityType,
       agentId: event.agentId,
       agentName: event.agentName,
+      subworkflowNodeId: event.subworkflowNodeId,
+      subworkflowName: event.subworkflowName,
       sourceAgentId: event.sourceAgentId,
       sourceAgentName: event.sourceAgentName,
       toolName: event.toolName,

src/main/services/sessionTurnExecutor.ts

@@ -675,7 +675,7 @@ export class SessionTurnExecutor {
     const session = this.requireSession(workspace, sessionId);
     const activityType = event.activityType;
     let nextRun: SessionRunRecord | undefined;
-    if (activityType !== 'completed') {
+    if (activityType === 'thinking' || activityType === 'tool-calling' || activityType === 'handoff') {
       nextRun = this.updateSessionRun(session, requestId, (run) =>
         appendRunActivityEvent(run, {
           activityType,
@@ -703,6 +703,8 @@ export class SessionTurnExecutor {
       activityType: event.activityType,
       agentId: event.agentId,
       agentName: event.agentName,
+      subworkflowNodeId: event.subworkflowNodeId,
+      subworkflowName: event.subworkflowName,
       sourceAgentId: event.sourceAgentId,
       sourceAgentName: event.sourceAgentName,
       toolName: event.toolName,

src/renderer/App.tsx

@@ -745,6 +745,7 @@ export default function App() {
       <ActivityPanel
         activity={activityForSession}
         workflow={workflowForSession}
+        workflows={workspace?.workflows}
         session={selectedSession}
         sessionRequestUsage={requestUsageForSession}
         turnEvents={turnEventsForSession}

src/renderer/components/ActivityPanel.tsx

@@ -1,59 +1,21 @@
 import { useMemo, type ReactNode } from 'react';
-import { Activity, AlertTriangle, ArrowRight, BarChart3, CheckCircle2, Cog, ShieldAlert, Sparkles, Users, Zap } from 'lucide-react';
+import { Activity, AlertTriangle, ArrowRight, BarChart3, CheckCircle2, Cog, GitBranch, ShieldAlert, Sparkles, Users, Zap } from 'lucide-react';
 
 import {
   buildAgentActivityRows,
-  formatAgentActivityLabel,
+  buildGroupedActivityRows,
   formatDuration,
   formatNanoAiu,
   formatTokenCount,
-  isAgentActivityActive,
-  isAgentActivityCompleted,
-  type AgentActivityRow,
-  type AgentUsageAccumulator,
   type SessionActivityState,
   type SessionRequestUsageState,
   type TurnEventLog,
 } from '@renderer/lib/sessionActivity';
-import { inferProvider } from '@shared/domain/models';
-import { resolveWorkflowAgentNodes, type AgentNodeConfig, type WorkflowDefinition, type WorkflowOrchestrationMode } from '@shared/domain/workflow';
+import { resolveWorkflowAgentHierarchy, type AgentNodeConfig, type WorkflowDefinition } from '@shared/domain/workflow';
 import type { SessionRecord } from '@shared/domain/session';
-import { ProviderIcon } from './ProviderIcons';
-
-/* ── Mode accent colours ───────────────────────────────────── */
-
-const modeAccent: Record<WorkflowOrchestrationMode, { dot: string; bar: string; label: string }> = {
-  single:       { dot: 'bg-[#245CF9]',                       bar: 'bg-[#245CF9] opacity-60',                       label: 'text-[#245CF9]' },
-  sequential:   { dot: 'bg-[var(--color-status-warning)]',   bar: 'bg-[var(--color-status-warning)] opacity-60',   label: 'text-[var(--color-status-warning)]' },
-  concurrent:   { dot: 'bg-[var(--color-status-success)]',   bar: 'bg-[var(--color-status-success)] opacity-60',   label: 'text-[var(--color-status-success)]' },
-  handoff:      { dot: 'bg-[var(--color-accent-sky)]',       bar: 'bg-[var(--color-accent-sky)] opacity-60',       label: 'text-[var(--color-accent-sky)]' },
-  'group-chat': { dot: 'bg-[var(--color-accent-purple)]',   bar: 'bg-[var(--color-accent-purple)] opacity-60',   label: 'text-[var(--color-accent-purple)]' },
-};
-
-/* ── Helpers ───────────────────────────────────────────────── */
-
-function formatModel(model: string): string {
-  return model.replace(/-/g, '\u2011');
-}
-
-function formatEffort(effort: string | undefined): string | undefined {
-  if (!effort) return undefined;
-  const labels: Record<string, string> = {
-    low: 'Low',
-    medium: 'Medium',
-    high: 'High',
-    xhigh: 'Max',
-  };
-  return labels[effort] ?? effort;
-}
-
-const modeLabels: Record<WorkflowOrchestrationMode, string> = {
-  single: 'Single agent',
-  sequential: 'Sequential',
-  concurrent: 'Concurrent',
-  handoff: 'Handoff',
-  'group-chat': 'Group chat',
-};
+import { AgentRow } from './activity/AgentRow';
+import { SubWorkflowGroup } from './activity/SubWorkflowGroup';
+import { modeAccent, modeLabels } from './activity/constants';
 
 /* ── Section header ────────────────────────────────────────── */
 
@@ -65,112 +27,6 @@ function SectionHeader({ children }: { children: ReactNode }) {
   );
 }
 
-/* ── Agent row ─────────────────────────────────────────────── */
-
-function AgentRow({
-  row,
-  agent,
-  accent,
-  isLast,
-  agentUsage,
-}: {
-  row: AgentActivityRow;
-  agent?: AgentNodeConfig;
-  accent: (typeof modeAccent)[WorkflowOrchestrationMode];
-  isLast: boolean;
-  agentUsage?: AgentUsageAccumulator;
-}) {
-  const isActive = isAgentActivityActive(row.activity);
-  const isCompleted = isAgentActivityCompleted(row.activity);
-
-  return (
-    <div className={`relative flex gap-2.5 py-2.5 ${isLast ? '' : 'border-b border-[var(--color-border-subtle)]'}`}>
-      {/* Left accent bar — visible only when this agent is actively working */}
-      {isActive && (
-        <div className={`absolute -left-3 bottom-2 top-2 w-[3px] rounded-full ${accent.bar}`} />
-      )}
-
-      {/* Status dot */}
-      <div className="flex shrink-0 pt-0.5">
-        <span
-          className={`size-2 rounded-full transition-all duration-200 ${
-            isActive
-              ? `animate-pulse ${accent.dot} ring-2 ring-[var(--color-border-glow)]`
-              : isCompleted
-                ? 'bg-[var(--color-status-success)]'
-                : 'bg-[var(--color-surface-3)]'
-          }`}
-        />
-      </div>
-
-      {/* Content */}
-      <div className="min-w-0 flex-1">
-        <div className="flex items-center gap-1.5">
-          <span className="truncate text-[12px] font-medium text-[var(--color-text-primary)]">{row.agentName}</span>
-        </div>
-
-        {/* Model + effort inline */}
-        {agent && (
-          <div className="mt-1 flex flex-wrap items-center gap-1">
-            <span className="inline-flex items-center gap-1 text-[10px] text-[var(--color-text-muted)]">
-              {(() => {
-                const prov = inferProvider(agent.model);
-                return prov ? <ProviderIcon provider={prov} className="size-2.5" /> : null;
-              })()}
-              {formatModel(agent.model)}
-            </span>
-            {agent.reasoningEffort && (
-              <>
-                <span className="text-[10px] text-[var(--color-text-muted)]">·</span>
-                <span className="inline-flex items-center gap-0.5 text-[10px] text-[var(--color-text-muted)]">
-                  <Sparkles className="size-2" />
-                  {formatEffort(agent.reasoningEffort)}
-                </span>
-              </>
-            )}
-          </div>
-        )}
-
-        {/* Activity label */}
-        <div className="mt-1 flex items-center gap-1">
-          <span
-            className={`text-[10px] ${
-              isActive
-                ? accent.label
-                : isCompleted
-                  ? 'text-[var(--color-status-success)]'
-                  : 'text-[var(--color-text-muted)]'
-            }`}
-          >
-            {formatAgentActivityLabel(row.activity)}
-          </span>
-        </div>
-
-        {/* Per-agent usage summary */}
-        {agentUsage && agentUsage.requestCount > 0 && (
-          <div className="mt-0.5 flex items-center gap-1 text-[10px] text-[var(--color-text-muted)]">
-            <span className="font-mono tabular-nums">{formatTokenCount(agentUsage.inputTokens)} in</span>
-            <span className="text-[var(--color-text-muted)]">·</span>
-            <span className="font-mono tabular-nums">{formatTokenCount(agentUsage.outputTokens)} out</span>
-            {agentUsage.cost > 0 && (
-              <>
-                <span className="text-[var(--color-text-muted)]">·</span>
-                <span className="font-mono tabular-nums">{agentUsage.cost.toFixed(2)} cost</span>
-              </>
-            )}
-            {agentUsage.durationMs > 0 && (
-              <>
-                <span className="text-[var(--color-text-muted)]">·</span>
-                <span className="font-mono tabular-nums">{formatDuration(agentUsage.durationMs)}</span>
-              </>
-            )}
-          </div>
-        )}
-      </div>
-    </div>
-  );
-}
-
 /* ── Turn event helpers ─────────────────────────────────────── */
 
 import type { SessionEventKind } from '@shared/domain/event';
@@ -178,6 +34,8 @@ import type { SessionEventKind } from '@shared/domain/event';
 function TurnEventIcon({ kind, phase, success }: { kind: SessionEventKind; phase?: string; success?: boolean }) {
   const base = 'size-3';
   switch (kind) {
+    case 'agent-activity':
+      return <GitBranch className={`${base} ${phase === 'start' ? 'text-[var(--color-accent-sky)]' : 'text-[var(--color-status-success)]'}`} />;
     case 'subagent':
       return <ArrowRight className={`${base} ${success === false ? 'text-[var(--color-status-error)]' : 'text-[var(--color-accent-sky)]'}`} />;
     case 'hook-lifecycle':
@@ -207,6 +65,7 @@ function formatTurnEventTimestamp(iso: string): string {
 interface ActivityPanelProps {
   activity?: SessionActivityState;
   workflow: WorkflowDefinition;
+  workflows?: ReadonlyArray<WorkflowDefinition>;
   session: SessionRecord;
   sessionRequestUsage?: SessionRequestUsageState;
   turnEvents?: TurnEventLog;
@@ -215,32 +74,40 @@ interface ActivityPanelProps {
 export function ActivityPanel({
   activity,
   workflow,
+  workflows,
   session,
   sessionRequestUsage,
   turnEvents,
 }: ActivityPanelProps) {
-  const workflowAgents = useMemo(
-    () => resolveWorkflowAgentNodes(workflow)
-      .map((n) => n.config)
-      .filter((c): c is AgentNodeConfig => c.kind === 'agent'),
-    [workflow],
-  );
-  const workflowMode = workflow.settings.orchestrationMode ?? 'single';
+  const resolveOptions = useMemo(() => ({
+    resolveWorkflow: (id: string) => workflows?.find((w) => w.id === id),
+  }), [workflows]);
 
-  const activityRows = useMemo(
-    () => buildAgentActivityRows(activity, workflowAgents),
-    [activity, workflowAgents],
+  const hierarchy = useMemo(
+    () => resolveWorkflowAgentHierarchy(workflow, resolveOptions),
+    [workflow, resolveOptions],
   );
 
+  const groupedRows = useMemo(
+    () => buildGroupedActivityRows(activity, hierarchy),
+    [activity, hierarchy],
+  );
+
+  const workflowMode = workflow.settings.orchestrationMode ?? 'single';
+  const totalAgentCount = hierarchy.topLevelAgents.length
+    + hierarchy.subWorkflows.reduce((sum, sw) => sum + sw.agents.length, 0);
+
   const isBusy = session.status === 'running';
   const hasPendingApproval = session.pendingApproval?.status === 'pending';
   const queuedCount = (session.pendingApprovalQueue ?? []).filter((a) => a.status === 'pending').length;
   const totalApprovalCount = (hasPendingApproval ? 1 : 0) + queuedCount;
   const accent = modeAccent[workflowMode] ?? modeAccent.single;
 
+  const hasSubWorkflows = groupedRows.subWorkflows.length > 0;
+
   return (
     <div className="flex h-full flex-col">
-      {/* Header — top padding clears the title bar overlay zone */}
+      {/* Header */}
       <div className="drag-region border-b border-[var(--color-border)] px-4 pb-3 pt-3">
         <div className="flex min-h-8 items-center gap-2">
           <Activity className="size-4 text-[var(--color-text-muted)]" />
@@ -267,32 +134,53 @@ export function ActivityPanel({
             <Users className="size-3" />
             <span>Agents</span>
             <span className="font-mono rounded-full bg-[var(--color-surface-2)] px-1.5 py-0.5 text-[9px] tabular-nums text-[var(--color-text-muted)]">
-              {activityRows.length}
+              {totalAgentCount}
             </span>
             <span className={`ml-auto text-[9px] font-medium normal-case tracking-normal ${accent.label}`}>
               {modeLabels[workflowMode]}
             </span>
           </SectionHeader>
 
-          {activityRows.length > 0 ? (
+          {/* Top-level agents */}
+          {groupedRows.topLevelAgents.length > 0 && (
             <div className="glass-surface rounded-lg px-3">
-              {activityRows.map((row, index) => {
+              {groupedRows.topLevelAgents.map((row, index) => {
+                const agent = hierarchy.topLevelAgents.find((a) => a.id === row.key || a.name === row.agentName);
                 const agentKey = row.activity?.agentId ?? row.key;
                 const agentUsage = sessionRequestUsage?.perAgent[agentKey]
                   ?? sessionRequestUsage?.perAgent[row.agentName];
                 return (
                   <AgentRow
-                    accent={accent}
-                    agent={workflowAgents[index]}
-                    agentUsage={agentUsage}
-                    isLast={index === activityRows.length - 1}
                     key={row.key}
                     row={row}
+                    agent={agent}
+                    accent={accent}
+                    isLast={!hasSubWorkflows && index === groupedRows.topLevelAgents.length - 1}
+                    agentUsage={agentUsage}
                   />
                 );
               })}
             </div>
-          ) : (
+          )}
+
+          {/* Sub-workflow groups */}
+          {hasSubWorkflows && (
+            <div className={`space-y-2 ${groupedRows.topLevelAgents.length > 0 ? 'mt-2' : ''}`}>
+              {groupedRows.subWorkflows.map((group) => {
+                const subDef = hierarchy.subWorkflows.find((sw) => sw.nodeId === group.nodeId);
+                return (
+                  <SubWorkflowGroup
+                    key={group.nodeId}
+                    group={group}
+                    agentConfigs={subDef?.agents ?? []}
+                    agentUsage={sessionRequestUsage?.perAgent}
+                  />
+                );
+              })}
+            </div>
+          )}
+
+          {totalAgentCount === 0 && !hasSubWorkflows && (
             <p className="py-4 text-center text-[11px] text-[var(--color-text-muted)]">No agents configured</p>
           )}
         </div>
@@ -376,5 +264,3 @@ export function ActivityPanel({
     </div>
   );
 }
-
-

src/renderer/components/activity/AgentRow.tsx

@@ -0,0 +1,111 @@
+import { Sparkles } from 'lucide-react';
+
+import type { AgentNodeConfig } from '@shared/domain/workflow';
+import { inferProvider } from '@shared/domain/models';
+import {
+  formatAgentActivityLabel,
+  formatDuration,
+  formatTokenCount,
+  isAgentActivityActive,
+  isAgentActivityCompleted,
+  type AgentActivityRow,
+  type AgentUsageAccumulator,
+} from '@renderer/lib/sessionActivity';
+import { ProviderIcon } from '@renderer/components/ProviderIcons';
+import { type ModeAccent, formatEffort, formatModel } from './constants';
+
+interface AgentRowProps {
+  row: AgentActivityRow;
+  agent?: AgentNodeConfig;
+  accent: ModeAccent;
+  isLast: boolean;
+  agentUsage?: AgentUsageAccumulator;
+}
+
+export function AgentRow({ row, agent, accent, isLast, agentUsage }: AgentRowProps) {
+  const isActive = isAgentActivityActive(row.activity);
+  const isCompleted = isAgentActivityCompleted(row.activity);
+
+  return (
+    <div className={`relative flex gap-2.5 py-2.5 ${isLast ? '' : 'border-b border-[var(--color-border-subtle)]'}`}>
+      {isActive && (
+        <div className={`absolute -left-3 bottom-2 top-2 w-[3px] rounded-full ${accent.bar}`} />
+      )}
+
+      {/* Status dot */}
+      <div className="flex shrink-0 pt-0.5">
+        <span
+          className={`size-2 rounded-full transition-all duration-200 ${
+            isActive
+              ? `animate-pulse ${accent.dot} ring-2 ring-[var(--color-border-glow)]`
+              : isCompleted
+                ? 'bg-[var(--color-status-success)]'
+                : 'bg-[var(--color-surface-3)]'
+          }`}
+        />
+      </div>
+
+      {/* Content */}
+      <div className="min-w-0 flex-1">
+        <div className="flex items-center gap-1.5">
+          <span className="truncate text-[12px] font-medium text-[var(--color-text-primary)]">{row.agentName}</span>
+        </div>
+
+        {agent && (
+          <div className="mt-1 flex flex-wrap items-center gap-1">
+            <span className="inline-flex items-center gap-1 text-[10px] text-[var(--color-text-muted)]">
+              {(() => {
+                const prov = inferProvider(agent.model);
+                return prov ? <ProviderIcon provider={prov} className="size-2.5" /> : null;
+              })()}
+              {formatModel(agent.model)}
+            </span>
+            {agent.reasoningEffort && (
+              <>
+                <span className="text-[10px] text-[var(--color-text-muted)]">·</span>
+                <span className="inline-flex items-center gap-0.5 text-[10px] text-[var(--color-text-muted)]">
+                  <Sparkles className="size-2" />
+                  {formatEffort(agent.reasoningEffort)}
+                </span>
+              </>
+            )}
+          </div>
+        )}
+
+        <div className="mt-1 flex items-center gap-1">
+          <span
+            className={`text-[10px] ${
+              isActive
+                ? accent.label
+                : isCompleted
+                  ? 'text-[var(--color-status-success)]'
+                  : 'text-[var(--color-text-muted)]'
+            }`}
+          >
+            {formatAgentActivityLabel(row.activity)}
+          </span>
+        </div>
+
+        {agentUsage && agentUsage.requestCount > 0 && (
+          <div className="mt-0.5 flex items-center gap-1 text-[10px] text-[var(--color-text-muted)]">
+            <span className="font-mono tabular-nums">{formatTokenCount(agentUsage.inputTokens)} in</span>
+            <span className="text-[var(--color-text-muted)]">·</span>
+            <span className="font-mono tabular-nums">{formatTokenCount(agentUsage.outputTokens)} out</span>
+            {agentUsage.cost > 0 && (
+              <>
+                <span className="text-[var(--color-text-muted)]">·</span>
+                <span className="font-mono tabular-nums">{agentUsage.cost.toFixed(2)} cost</span>
+              </>
+            )}
+            {agentUsage.durationMs > 0 && (
+              <>
+                <span className="text-[var(--color-text-muted)]">·</span>
+                <span className="font-mono tabular-nums">{formatDuration(agentUsage.durationMs)}</span>
+              </>
+            )}
+          </div>
+        )}
+      </div>
+    </div>
+  );
+}

src/renderer/components/activity/SubWorkflowGroup.tsx

@@ -0,0 +1,145 @@
+import { useCallback, useEffect, useRef, useState } from 'react';
+import { ChevronDown, GitBranch } from 'lucide-react';
+
+import type { AgentNodeConfig } from '@shared/domain/workflow';
+import {
+  isAgentActivityActive,
+  type AgentUsageAccumulator,
+  type SubWorkflowActivityGroup,
+} from '@renderer/lib/sessionActivity';
+import { AgentRow } from './AgentRow';
+import { modeAccent, modeLabels } from './constants';
+
+interface SubWorkflowGroupProps {
+  group: SubWorkflowActivityGroup;
+  agentConfigs: ReadonlyArray<AgentNodeConfig>;
+  agentUsage?: Record<string, AgentUsageAccumulator>;
+}
+
+const statusPresentation = {
+  idle: {
+    dot: 'bg-[var(--color-surface-3)]',
+    text: 'text-[var(--color-text-muted)]',
+    label: 'Idle',
+  },
+  running: {
+    dot: 'animate-pulse',
+    text: '',
+    label: 'Running',
+  },
+  completed: {
+    dot: 'bg-[var(--color-status-success)]',
+    text: 'text-[var(--color-status-success)]',
+    label: 'Done',
+  },
+} as const;
+
+export function SubWorkflowGroup({ group, agentConfigs, agentUsage }: SubWorkflowGroupProps) {
+  const [isExpanded, setIsExpanded] = useState(false);
+  const prevStatusRef = useRef(group.status);
+
+  useEffect(() => {
+    if (prevStatusRef.current !== 'running' && group.status === 'running') {
+      setIsExpanded(true);
+    }
+    prevStatusRef.current = group.status;
+  }, [group.status]);
+
+  const toggle = useCallback(() => setIsExpanded((prev) => !prev), []);
+
+  const accent = modeAccent[group.orchestrationMode] ?? modeAccent.single;
+  const status = statusPresentation[group.status];
+  const hasActiveAgent = group.agents.some((a) => isAgentActivityActive(a.activity));
+
+  return (
+    <div
+      className="overflow-hidden rounded-lg border border-[var(--color-border-subtle)] border-l-[3px] bg-[var(--color-surface-1)]"
+      style={{ borderLeftColor: accent.color }}
+      role="group"
+      aria-label={`Sub-workflow: ${group.name}`}
+    >
+      {/* Collapsible header */}
+      <button
+        className="flex w-full items-center gap-2 px-3 py-2.5 text-left transition-colors hover:bg-[var(--color-surface-2)]"
+        onClick={toggle}
+        onKeyDown={(e) => {
+          if (e.key === 'Enter' || e.key === ' ') {
+            e.preventDefault();
+            toggle();
+          }
+        }}
+        aria-expanded={isExpanded}
+        type="button"
+      >
+        <GitBranch className="size-3.5 shrink-0 text-[var(--color-text-muted)]" />
+
+        <span className="min-w-0 flex-1 truncate text-[12px] font-medium text-[var(--color-text-primary)]">
+          {group.name}
+        </span>
+
+        {/* Status badge */}
+        <span className="flex items-center gap-1" aria-live="polite">
+          <span
+            className={`size-1.5 rounded-full ${
+              group.status === 'running'
+                ? `${accent.dot} ${status.dot} ring-1 ring-[var(--color-border-glow)]`
+                : status.dot
+            }`}
+          />
+          <span className={`text-[9px] font-medium ${group.status === 'running' ? accent.label : status.text}`}>
+            {status.label}
+          </span>
+        </span>
+
+        {/* Agent count pill */}
+        <span className="font-mono rounded-full bg-[var(--color-surface-2)] px-1.5 py-0.5 text-[9px] tabular-nums text-[var(--color-text-muted)]">
+          {group.agents.length}
+        </span>
+
+        <ChevronDown
+          className={`size-3 shrink-0 text-[var(--color-text-muted)] transition-transform duration-150 ${
+            isExpanded ? 'rotate-180' : ''
+          }`}
+        />
+      </button>
+
+      {/* Expandable agent list */}
+      <div
+        className="grid transition-[grid-template-rows] duration-150 ease-out"
+        style={{ gridTemplateRows: isExpanded ? '1fr' : '0fr' }}
+      >
+        <div className="overflow-hidden">
+          <div className="relative border-t border-[var(--color-border-subtle)] py-1 pl-5 pr-3">
+            {/* Connecting vertical accent line */}
+            {hasActiveAgent && (
+              <div className={`absolute bottom-3 left-[11px] top-3 w-px ${accent.bar}`} />
+            )}
+
+            {group.agents.map((row, index) => {
+              const agent = agentConfigs.find((c) => c.id === row.key || c.name === row.agentName);
+              const usage = agentUsage?.[row.activity?.agentId ?? row.key] ?? agentUsage?.[row.agentName];
+
+              return (
+                <AgentRow
+                  key={row.key}
+                  row={row}
+                  agent={agent}
+                  accent={accent}
+                  isLast={index === group.agents.length - 1}
+                  agentUsage={usage}
+                />
+              );
+            })}
+
+            {/* Mode label */}
+            <div className="flex items-center gap-1 pb-1 pt-0.5">
+              <span className={`text-[9px] font-medium ${accent.label}`}>
+                {modeLabels[group.orchestrationMode]}
+              </span>
+            </div>
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+}

src/renderer/components/activity/constants.ts

@@ -0,0 +1,34 @@
+import type { WorkflowOrchestrationMode } from '@shared/domain/workflow';
+
+export interface ModeAccent {
+  dot: string;
+  bar: string;
+  label: string;
+  color: string;
+}
+
+export const modeAccent: Record<WorkflowOrchestrationMode, ModeAccent> = {
+  single:       { dot: 'bg-[#245CF9]',                       bar: 'bg-[#245CF9] opacity-60',                       label: 'text-[#245CF9]',                       color: '#245CF9' },
+  sequential:   { dot: 'bg-[var(--color-status-warning)]',   bar: 'bg-[var(--color-status-warning)] opacity-60',   label: 'text-[var(--color-status-warning)]',   color: 'var(--color-status-warning)' },
+  concurrent:   { dot: 'bg-[var(--color-status-success)]',   bar: 'bg-[var(--color-status-success)] opacity-60',   label: 'text-[var(--color-status-success)]',   color: 'var(--color-status-success)' },
+  handoff:      { dot: 'bg-[var(--color-accent-sky)]',       bar: 'bg-[var(--color-accent-sky)] opacity-60',       label: 'text-[var(--color-accent-sky)]',       color: 'var(--color-accent-sky)' },
+  'group-chat': { dot: 'bg-[var(--color-accent-purple)]',   bar: 'bg-[var(--color-accent-purple)] opacity-60',   label: 'text-[var(--color-accent-purple)]',   color: 'var(--color-accent-purple)' },
+};
+
+export const modeLabels: Record<WorkflowOrchestrationMode, string> = {
+  single: 'Single agent',
+  sequential: 'Sequential',
+  concurrent: 'Concurrent',
+  handoff: 'Handoff',
+  'group-chat': 'Group chat',
+};
+
+export function formatModel(model: string): string {
+  return model.replace(/-/g, '\u2011');
+}
+
+export function formatEffort(effort: string | undefined): string | undefined {
+  if (!effort) return undefined;
+  const labels: Record<string, string> = { low: 'Low', medium: 'Medium', high: 'High', xhigh: 'Max' };
+  return labels[effort] ?? effort;
+}

src/renderer/lib/sessionActivity.ts

@@ -1,4 +1,4 @@
-import type { AgentNodeConfig } from '@shared/domain/workflow';
+import type { AgentNodeConfig, WorkflowAgentHierarchy, WorkflowOrchestrationMode } from '@shared/domain/workflow';
 import type { SessionEventRecord } from '@shared/domain/event';
 import type { QuotaSnapshot, WorkflowDiagnosticKind, WorkflowDiagnosticSeverity } from '@shared/contracts/sidecar';
 
@@ -8,6 +8,8 @@ export interface AgentActivityState {
   activityType?: SessionEventRecord['activityType'];
   toolName?: string;
   toolArguments?: Record<string, unknown>;
+  subworkflowNodeId?: string;
+  subworkflowName?: string;
 }
 
 export interface SessionUsageState {
@@ -31,9 +33,14 @@ export function applySessionEventActivity(
   event: SessionEventRecord,
 ): SessionActivityMap {
   if (event.kind === 'agent-activity') {
-    const agentKey = resolveAgentKey(event);
+    const isSubworkflowLifecycle =
+      event.activityType === 'subworkflow-started' || event.activityType === 'subworkflow-completed';
+    const agentKey = isSubworkflowLifecycle
+      ? event.subworkflowNodeId?.trim()
+      : resolveAgentKey(event);
+
     if (!agentKey) {
-      console.warn('[aryx activity] Dropping agent-activity event without agentId/agentName.', event);
+      console.warn('[aryx activity] Dropping agent-activity event without key.', event);
       return current;
     }
 
@@ -43,10 +50,12 @@ export function applySessionEventActivity(
         ...(current[event.sessionId] ?? {}),
         [agentKey]: {
           agentId: event.agentId ?? agentKey,
-          agentName: event.agentName?.trim() || event.agentId?.trim() || agentKey,
+          agentName: event.agentName?.trim() || event.subworkflowName?.trim() || event.agentId?.trim() || agentKey,
           activityType: event.activityType,
           toolName: event.toolName,
           toolArguments: event.toolArguments,
+          subworkflowNodeId: event.subworkflowNodeId,
+          subworkflowName: event.subworkflowName,
         },
       },
     };
@@ -146,6 +155,88 @@ export function isAgentActivityCompleted(activity: AgentActivityState | undefine
   return activity?.activityType === 'completed';
 }
 
+export type SubWorkflowGroupStatus = 'idle' | 'running' | 'completed';
+
+export interface SubWorkflowActivityGroup {
+  nodeId: string;
+  name: string;
+  workflowId?: string;
+  orchestrationMode: WorkflowOrchestrationMode;
+  status: SubWorkflowGroupStatus;
+  agents: AgentActivityRow[];
+}
+
+export interface GroupedActivityRows {
+  topLevelAgents: AgentActivityRow[];
+  subWorkflows: SubWorkflowActivityGroup[];
+}
+
+function resolveSubWorkflowGroupStatus(
+  agents: AgentActivityRow[],
+  lifecycleEntry: AgentActivityState | undefined,
+): SubWorkflowGroupStatus {
+  if (lifecycleEntry?.activityType === 'subworkflow-completed') return 'completed';
+  if (lifecycleEntry?.activityType === 'subworkflow-started') return 'running';
+  if (agents.some((a) => isAgentActivityActive(a.activity))) return 'running';
+  if (agents.some((a) => isAgentActivityCompleted(a.activity))) return 'completed';
+  return 'idle';
+}
+
+export function buildGroupedActivityRows(
+  current: SessionActivityState | undefined,
+  hierarchy: WorkflowAgentHierarchy,
+): GroupedActivityRows {
+  const topLevelAgents = buildAgentActivityRows(current, hierarchy.topLevelAgents);
+  const subWorkflows: SubWorkflowActivityGroup[] = hierarchy.subWorkflows.map((sub) => {
+    const agents = buildAgentActivityRows(current, sub.agents);
+    const lifecycleEntry = current?.[sub.nodeId];
+
+    return {
+      nodeId: sub.nodeId,
+      name: sub.workflowName || sub.nodeLabel,
+      workflowId: sub.workflowId,
+      orchestrationMode: sub.orchestrationMode,
+      status: resolveSubWorkflowGroupStatus(agents, lifecycleEntry),
+      agents,
+    };
+  });
+
+  // Pick up agents that arrived via activity events with a subworkflowNodeId
+  // but whose sub-workflow isn't in the statically-resolved hierarchy (e.g.
+  // a referenced workflow that couldn't be resolved at design time).
+  if (current) {
+    const knownKeys = new Set([
+      ...topLevelAgents.map((a) => a.key),
+      ...subWorkflows.flatMap((sw) => [sw.nodeId, ...sw.agents.map((a) => a.key)]),
+    ]);
+
+    const dynamicGroups = new Map<string, { name: string; agents: AgentActivityRow[] }>();
+    for (const [key, state] of Object.entries(current)) {
+      if (knownKeys.has(key)) continue;
+      if (!state.subworkflowNodeId) continue;
+      if (state.activityType === 'subworkflow-started' || state.activityType === 'subworkflow-completed') continue;
+
+      const group = dynamicGroups.get(state.subworkflowNodeId)
+        ?? { name: state.subworkflowName ?? state.subworkflowNodeId, agents: [] };
+      group.agents.push({ key, agentName: state.agentName, activity: state });
+      dynamicGroups.set(state.subworkflowNodeId, group);
+    }
+
+    for (const [nodeId, group] of dynamicGroups) {
+      const lifecycleEntry = current[nodeId];
+      subWorkflows.push({
+        nodeId,
+        name: group.name,
+        orchestrationMode: 'sequential',
+        status: resolveSubWorkflowGroupStatus(group.agents, lifecycleEntry),
+        agents: group.agents,
+      });
+    }
+  }
+
+  return { topLevelAgents, subWorkflows };
+}
+
 function removeSessionActivity(
   current: SessionActivityMap,
   sessionId: string,
@@ -280,6 +371,26 @@ function formatDiagnosticLabel(
 
 function formatTurnEventEntry(event: SessionEventRecord): TurnEventEntry | undefined {
   switch (event.kind) {
+    case 'agent-activity': {
+      if (event.activityType === 'subworkflow-started') {
+        return {
+          kind: event.kind,
+          occurredAt: event.occurredAt,
+          label: `Sub-workflow started: ${event.subworkflowName ?? event.subworkflowNodeId ?? 'unknown'}`,
+          phase: 'start',
+        };
+      }
+      if (event.activityType === 'subworkflow-completed') {
+        return {
+          kind: event.kind,
+          occurredAt: event.occurredAt,
+          label: `Sub-workflow completed: ${event.subworkflowName ?? event.subworkflowNodeId ?? 'unknown'}`,
+          phase: 'end',
+          success: true,
+        };
+      }
+      return undefined;
+    }
     case 'subagent':
       return {
         kind: event.kind,

src/shared/contracts/sidecar.ts

@@ -271,7 +271,13 @@ export interface MessageReclassifiedEvent {
   newKind: 'thinking';
 }
 
-export type AgentActivityType = 'thinking' | 'tool-calling' | 'handoff' | 'completed';
+export type AgentActivityType =
+  | 'thinking'
+  | 'tool-calling'
+  | 'handoff'
+  | 'completed'
+  | 'subworkflow-started'
+  | 'subworkflow-completed';
 
 export interface ToolCallFileChangePreview {
   path: string;
@@ -286,6 +292,8 @@ export interface AgentActivityEvent {
   activityType: AgentActivityType;
   agentId?: string;
   agentName?: string;
+  subworkflowNodeId?: string;
+  subworkflowName?: string;
   sourceAgentId?: string;
   sourceAgentName?: string;
   toolName?: string;

src/shared/domain/event.ts

@@ -8,7 +8,13 @@ import type {
   WorkflowDiagnosticSeverity,
 } from '@shared/contracts/sidecar';
 
-export type SessionActivityType = 'thinking' | 'tool-calling' | 'handoff' | 'completed';
+export type SessionActivityType =
+  | 'thinking'
+  | 'tool-calling'
+  | 'handoff'
+  | 'completed'
+  | 'subworkflow-started'
+  | 'subworkflow-completed';
 
 export type SessionEventKind =
   | 'status'
@@ -42,6 +48,8 @@ export interface SessionEventRecord {
   activityType?: SessionActivityType;
   agentId?: string;
   agentName?: string;
+  subworkflowNodeId?: string;
+  subworkflowName?: string;
   sourceAgentId?: string;
   sourceAgentName?: string;
   toolName?: string;

src/shared/domain/workflow.ts

@@ -536,6 +536,68 @@ export function resolveWorkflowAgents(workflow: WorkflowDefinition): AgentNodeCo
   });
 }
 
+export interface SubWorkflowGroupDescriptor {
+  nodeId: string;
+  nodeLabel: string;
+  workflowId?: string;
+  workflowName: string;
+  orchestrationMode: WorkflowOrchestrationMode;
+  agents: AgentNodeConfig[];
+}
+
+export interface WorkflowAgentHierarchy {
+  topLevelAgents: AgentNodeConfig[];
+  subWorkflows: SubWorkflowGroupDescriptor[];
+}
+
+export function resolveWorkflowAgentHierarchy(
+  workflow: WorkflowDefinition,
+  options?: WorkflowResolutionOptions,
+): WorkflowAgentHierarchy {
+  const topLevelAgents = resolveWorkflowAgents(workflow);
+  const subWorkflows: SubWorkflowGroupDescriptor[] = [];
+
+  const subWorkflowNodes = workflow.graph.nodes
+    .filter((node): node is WorkflowNode & { config: SubWorkflowConfig } => node.kind === 'sub-workflow')
+    .slice()
+    .sort((a, b) => {
+      const orderA = a.order ?? Number.MAX_SAFE_INTEGER;
+      const orderB = b.order ?? Number.MAX_SAFE_INTEGER;
+      if (orderA !== orderB) return orderA - orderB;
+      return a.label.localeCompare(b.label);
+    });
+
+  for (const node of subWorkflowNodes) {
+    const subWorkflowDef = resolveSubWorkflowDefinition(node, options);
+    if (!subWorkflowDef) continue;
+
+    const agents = resolveWorkflowAgents(subWorkflowDef);
+    const mode = inferWorkflowOrchestrationMode(subWorkflowDef, options);
+
+    subWorkflows.push({
+      nodeId: node.id,
+      nodeLabel: node.label,
+      workflowId: node.config.workflowId,
+      workflowName: subWorkflowDef.name || node.label,
+      orchestrationMode: mode,
+      agents,
+    });
+  }
+
+  return { topLevelAgents, subWorkflows };
+}
+
+function resolveSubWorkflowDefinition(
+  node: WorkflowNode & { config: SubWorkflowConfig },
+  options?: WorkflowResolutionOptions,
+): WorkflowDefinition | undefined {
+  if (node.config.inlineWorkflow) return node.config.inlineWorkflow;
+  if (node.config.workflowId && options?.resolveWorkflow) {
+    return options.resolveWorkflow(node.config.workflowId);
+  }
+  return undefined;
+}
+
 function hasWorkflowExecutionFanEdges(
   workflow: WorkflowDefinition,
   options?: WorkflowResolutionOptions,