diff --git a/apps/web/src/components/radar/CompactionEventsDialog.tsx b/apps/web/src/components/radar/CompactionEventsDialog.tsx
new file mode 100644
index 0000000..e188376
--- /dev/null
+++ b/apps/web/src/components/radar/CompactionEventsDialog.tsx
@@ -0,0 +1,111 @@
+import { trpc } from '@/lib/trpc'
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog'
+import { Skeleton } from '@/components/ui/skeleton'
+import type { DrilldownDialogProps } from './types'
+
+function formatTimestamp(ts: string): string {
+  const date = new Date(ts)
+  const now = new Date()
+  const diffMs = now.getTime() - date.getTime()
+  const diffSecs = Math.floor(diffMs / 1000)
+  const diffMins = Math.floor(diffSecs / 60)
+  const diffHours = Math.floor(diffMins / 60)
+  const diffDays = Math.floor(diffHours / 24)
+
+  let relative: string
+  if (diffSecs < 60) {
+    relative = `${diffSecs}s ago`
+  } else if (diffMins < 60) {
+    relative = `${diffMins}m ago`
+  } else if (diffHours < 24) {
+    relative = `${diffHours}h ago`
+  } else {
+    relative = `${diffDays}d ago`
+  }
+
+  const absolute = date.toLocaleString('en-US', {
+    month: 'short',
+    day: 'numeric',
+    year: 'numeric',
+    hour: '2-digit',
+    minute: '2-digit',
+    second: '2-digit',
+    hour12: false,
+  })
+
+  return `${relative} · ${absolute}`
+}
+
+export function CompactionEventsDialog({
+  open,
+  onOpenChange,
+  agentId,
+  agentName,
+}: DrilldownDialogProps) {
+  const { data, isLoading } = trpc.agent.getCompactionEvents.useQuery(
+    { agentId },
+    { enabled: open }
+  )
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent className="max-w-2xl">
+        <DialogHeader>
+          <DialogTitle>{`Compaction Events — ${agentName}`}</DialogTitle>
+          <DialogDescription>
+            Each row is a context-window compaction — the model&apos;s history was summarized to
+            free up space. Frequent compactions indicate a long-running agent with large context.
+          </DialogDescription>
+        </DialogHeader>
+
+        <div className="max-h-[70vh] overflow-y-auto">
+          {isLoading ? (
+            <div className="space-y-2">
+              {[0, 1, 2].map((i) => (
+                <div key={i}>
+                  <div className="flex items-center gap-4 py-2">
+                    <Skeleton className="w-40 h-4" />
+                    <Skeleton className="w-12 h-4" />
+                  </div>
+                  {i < 2 && <div className="border-b" />}
+                </div>
+              ))}
+            </div>
+          ) : !data || data.length === 0 ? (
+            <p className="text-center text-muted-foreground py-8">No data found</p>
+          ) : (
+            <>
+              {data.length >= 200 && (
+                <p className="text-sm text-muted-foreground mb-2">Showing first 200 instances.</p>
+              )}
+              <table className="w-full text-sm">
+                <thead>
+                  <tr className="border-b">
+                    <th className="text-left py-2 pr-4 font-medium">Timestamp</th>
+                    <th className="text-center py-2 font-medium">Session #</th>
+                  </tr>
+                </thead>
+                <tbody>
+                  {data.map((row, i) => (
+                    <tr key={i} className="border-b last:border-0">
+                      <td className="py-2 pr-4 text-muted-foreground">
+                        {formatTimestamp(row.timestamp)}
+                      </td>
+                      <td className="py-2 text-center">{row.sessionNumber}</td>
+                    </tr>
+                  ))}
+                </tbody>
+              </table>
+            </>
+          )}
+        </div>
+      </DialogContent>
+    </Dialog>
+  )
+}
diff --git a/apps/web/src/components/radar/SubagentSpawnsDialog.tsx b/apps/web/src/components/radar/SubagentSpawnsDialog.tsx
new file mode 100644
index 0000000..2fe27e9
--- /dev/null
+++ b/apps/web/src/components/radar/SubagentSpawnsDialog.tsx
@@ -0,0 +1,143 @@
+import { useState, useEffect, Fragment } from 'react'
+import { trpc } from '@/lib/trpc'
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog'
+import { Skeleton } from '@/components/ui/skeleton'
+import type { DrilldownDialogProps } from './types'
+
+function formatTimestamp(ts: string): string {
+  const date = new Date(ts)
+  const now = new Date()
+  const diffMs = now.getTime() - date.getTime()
+  const diffSecs = Math.floor(diffMs / 1000)
+  const diffMins = Math.floor(diffSecs / 60)
+  const diffHours = Math.floor(diffMins / 60)
+  const diffDays = Math.floor(diffHours / 24)
+
+  let relative: string
+  if (diffSecs < 60) {
+    relative = `${diffSecs}s ago`
+  } else if (diffMins < 60) {
+    relative = `${diffMins}m ago`
+  } else if (diffHours < 24) {
+    relative = `${diffHours}h ago`
+  } else {
+    relative = `${diffDays}d ago`
+  }
+
+  const absolute = date.toLocaleString('en-US', {
+    month: 'short',
+    day: 'numeric',
+    year: 'numeric',
+    hour: '2-digit',
+    minute: '2-digit',
+    second: '2-digit',
+    hour12: false,
+  })
+
+  return `${relative} · ${absolute}`
+}
+
+export function SubagentSpawnsDialog({
+  open,
+  onOpenChange,
+  agentId,
+  agentName,
+}: DrilldownDialogProps) {
+  const [expandedIndex, setExpandedIndex] = useState<number | null>(null)
+
+  const { data, isLoading } = trpc.agent.getSubagentSpawns.useQuery(
+    { agentId },
+    { enabled: open }
+  )
+
+  useEffect(() => {
+    if (!open) setExpandedIndex(null)
+  }, [open])
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent className="max-w-3xl">
+        <DialogHeader>
+          <DialogTitle>{`Subagent Spawns — ${agentName}`}</DialogTitle>
+          <DialogDescription>
+            Each row is an Agent tool call — a subagent spawned by this agent. The description and
+            first 200 characters of the prompt are shown.
+          </DialogDescription>
+        </DialogHeader>
+
+        <div className="max-h-[70vh] overflow-y-auto">
+          {isLoading ? (
+            <div className="space-y-2">
+              {[0, 1, 2].map((i) => (
+                <div key={i}>
+                  <div className="flex items-center gap-4 py-2">
+                    <Skeleton className="w-32 h-4" />
+                    <Skeleton className="w-48 h-4" />
+                    <Skeleton className="w-64 h-4" />
+                  </div>
+                  {i < 2 && <div className="border-b" />}
+                </div>
+              ))}
+            </div>
+          ) : !data || data.length === 0 ? (
+            <p className="text-center text-muted-foreground py-8">No data found</p>
+          ) : (
+            <>
+              {data.length >= 200 && (
+                <p className="text-sm text-muted-foreground mb-2">Showing first 200 instances.</p>
+              )}
+              <table className="w-full text-sm">
+                <thead>
+                  <tr className="border-b">
+                    <th className="text-left py-2 pr-4 font-medium">Timestamp</th>
+                    <th className="text-left py-2 pr-4 font-medium">Description</th>
+                    <th className="text-left py-2 font-medium">Prompt Preview</th>
+                  </tr>
+                </thead>
+                <tbody>
+                  {data.map((row, i) => (
+                    <Fragment key={i}>
+                      <tr
+                        className="border-b last:border-0 cursor-pointer hover:bg-muted/50"
+                        onClick={() => setExpandedIndex(i === expandedIndex ? null : i)}
+                      >
+                        <td className="py-2 pr-4 text-muted-foreground whitespace-nowrap">
+                          {formatTimestamp(row.timestamp)}
+                        </td>
+                        <td className="py-2 pr-4">{row.description}</td>
+                        <td className="py-2">
+                          {row.promptPreview}
+                          {row.fullPrompt.length > row.promptPreview.length && (
+                            <span>…</span>
+                          )}
+                        </td>
+                      </tr>
+                      {expandedIndex === i && (
+                        <tr>
+                          <td colSpan={3} className="pb-2">
+                            <div
+                              className="bg-muted/30 p-3 rounded"
+                              style={{ maxHeight: '300px', overflowY: 'auto', fontFamily: 'monospace' }}
+                            >
+                              <pre>{row.fullPrompt}</pre>
+                            </div>
+                          </td>
+                        </tr>
+                      )}
+                    </Fragment>
+                  ))}
+                </tbody>
+              </table>
+            </>
+          )}
+        </div>
+      </DialogContent>
+    </Dialog>
+  )
+}
diff --git a/apps/web/src/components/radar/__tests__/CompactionEventsDialog.test.tsx b/apps/web/src/components/radar/__tests__/CompactionEventsDialog.test.tsx
new file mode 100644
index 0000000..94a2e8a
--- /dev/null
+++ b/apps/web/src/components/radar/__tests__/CompactionEventsDialog.test.tsx
@@ -0,0 +1,82 @@
+// @vitest-environment happy-dom
+import '@testing-library/jest-dom/vitest'
+import { render, screen } from '@testing-library/react'
+import { vi, describe, it, expect, beforeEach } from 'vitest'
+
+let mockUseQueryReturn: { data: unknown; isLoading: boolean } = {
+  data: undefined,
+  isLoading: false,
+}
+
+vi.mock('@/lib/trpc', () => ({
+  trpc: {
+    agent: {
+      getCompactionEvents: {
+        useQuery: vi.fn((_args: unknown, _opts: unknown) => mockUseQueryReturn),
+      },
+    },
+  },
+}))
+
+import { CompactionEventsDialog } from '../CompactionEventsDialog'
+
+const defaultProps = {
+  open: true,
+  onOpenChange: vi.fn(),
+  agentId: 'agent-123',
+  agentName: 'test-agent',
+}
+
+describe('CompactionEventsDialog', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    mockUseQueryReturn = { data: undefined, isLoading: false }
+  })
+
+  it('does not render dialog content when open=false', () => {
+    render(<CompactionEventsDialog {...defaultProps} open={false} />)
+    expect(screen.queryByText(/Compaction Events/)).toBeNull()
+  })
+
+  it('shows skeleton rows when loading', () => {
+    mockUseQueryReturn = { data: undefined, isLoading: true }
+    render(<CompactionEventsDialog {...defaultProps} />)
+    const skeletons = document.querySelectorAll('.animate-pulse')
+    expect(skeletons.length).toBeGreaterThanOrEqual(3)
+    expect(screen.queryByRole('table')).toBeNull()
+  })
+
+  it('shows "No data found" when data is empty', () => {
+    mockUseQueryReturn = { data: [], isLoading: false }
+    render(<CompactionEventsDialog {...defaultProps} />)
+    expect(screen.getByText('No data found')).toBeInTheDocument()
+  })
+
+  it('renders data rows correctly', () => {
+    mockUseQueryReturn = {
+      data: [{ timestamp: '2026-03-06T10:00:00.000Z', sessionNumber: 3 }],
+      isLoading: false,
+    }
+    render(<CompactionEventsDialog {...defaultProps} />)
+    expect(screen.getByText('3')).toBeInTheDocument()
+    // Timestamp includes year 2026
+    expect(screen.getByText(/2026/)).toBeInTheDocument()
+    expect(screen.queryByText('Showing first 200 instances.')).toBeNull()
+  })
+
+  it('shows 200-instance note when data length is 200', () => {
+    mockUseQueryReturn = {
+      data: Array(200).fill({ timestamp: '2026-03-06T10:00:00.000Z', sessionNumber: 1 }),
+      isLoading: false,
+    }
+    render(<CompactionEventsDialog {...defaultProps} />)
+    expect(screen.getByText('Showing first 200 instances.')).toBeInTheDocument()
+  })
+
+  it('renders dialog title and subtitle', () => {
+    mockUseQueryReturn = { data: [], isLoading: false }
+    render(<CompactionEventsDialog {...defaultProps} />)
+    expect(screen.getByText(/Compaction Events — test-agent/)).toBeInTheDocument()
+    expect(screen.getByText(/context-window compaction/)).toBeInTheDocument()
+  })
+})
diff --git a/apps/web/src/components/radar/__tests__/SubagentSpawnsDialog.test.tsx b/apps/web/src/components/radar/__tests__/SubagentSpawnsDialog.test.tsx
new file mode 100644
index 0000000..de2cb7e
--- /dev/null
+++ b/apps/web/src/components/radar/__tests__/SubagentSpawnsDialog.test.tsx
@@ -0,0 +1,127 @@
+// @vitest-environment happy-dom
+import '@testing-library/jest-dom/vitest'
+import { render, screen, fireEvent } from '@testing-library/react'
+import { vi, describe, it, expect, beforeEach } from 'vitest'
+
+let mockUseQueryReturn: { data: unknown; isLoading: boolean } = {
+  data: undefined,
+  isLoading: false,
+}
+
+vi.mock('@/lib/trpc', () => ({
+  trpc: {
+    agent: {
+      getSubagentSpawns: {
+        useQuery: vi.fn((_args: unknown, _opts: unknown) => mockUseQueryReturn),
+      },
+    },
+  },
+}))
+
+import { SubagentSpawnsDialog } from '../SubagentSpawnsDialog'
+
+const defaultProps = {
+  open: true,
+  onOpenChange: vi.fn(),
+  agentId: 'agent-123',
+  agentName: 'test-agent',
+}
+
+describe('SubagentSpawnsDialog', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    mockUseQueryReturn = { data: undefined, isLoading: false }
+  })
+
+  it('does not render dialog content when open=false', () => {
+    render(<SubagentSpawnsDialog {...defaultProps} open={false} />)
+    expect(screen.queryByText(/Subagent Spawns/)).toBeNull()
+  })
+
+  it('shows skeleton rows when loading', () => {
+    mockUseQueryReturn = { data: undefined, isLoading: true }
+    render(<SubagentSpawnsDialog {...defaultProps} />)
+    const skeletons = document.querySelectorAll('.animate-pulse')
+    expect(skeletons.length).toBeGreaterThanOrEqual(3)
+    expect(screen.queryByRole('table')).toBeNull()
+  })
+
+  it('shows "No data found" when data is empty', () => {
+    mockUseQueryReturn = { data: [], isLoading: false }
+    render(<SubagentSpawnsDialog {...defaultProps} />)
+    expect(screen.getByText('No data found')).toBeInTheDocument()
+  })
+
+  it('renders data rows correctly', () => {
+    mockUseQueryReturn = {
+      data: [
+        {
+          timestamp: '2026-03-06T10:00:00.000Z',
+          description: 'my task',
+          promptPreview: 'hello',
+          fullPrompt: 'hello world full',
+        },
+      ],
+      isLoading: false,
+    }
+    render(<SubagentSpawnsDialog {...defaultProps} />)
+    expect(screen.getByText('my task')).toBeInTheDocument()
+    expect(screen.getByText('hello')).toBeInTheDocument()
+    expect(screen.queryByText('hello world full')).toBeNull()
+  })
+
+  it('expands and collapses row on click', () => {
+    mockUseQueryReturn = {
+      data: [
+        {
+          timestamp: '2026-03-06T10:00:00.000Z',
+          description: 'my task',
+          promptPreview: 'hello',
+          fullPrompt: 'hello world full',
+        },
+      ],
+      isLoading: false,
+    }
+    render(<SubagentSpawnsDialog {...defaultProps} />)
+
+    // Click the row — should expand
+    fireEvent.click(screen.getByText('my task').closest('tr')!)
+    expect(screen.getByText('hello world full')).toBeInTheDocument()
+
+    // Click again — should collapse
+    fireEvent.click(screen.getByText('my task').closest('tr')!)
+    expect(screen.queryByText('hello world full')).toBeNull()
+  })
+
+  it('shows ellipsis suffix when fullPrompt is longer than promptPreview', () => {
+    const fullPrompt = 'A'.repeat(201)
+    const promptPreview = fullPrompt.slice(0, 200)
+    mockUseQueryReturn = {
+      data: [
+        {
+          timestamp: '2026-03-06T10:00:00.000Z',
+          description: 'truncated task',
+          promptPreview,
+          fullPrompt,
+        },
+      ],
+      isLoading: false,
+    }
+    render(<SubagentSpawnsDialog {...defaultProps} />)
+    expect(screen.getByText('…')).toBeInTheDocument()
+  })
+
+  it('shows 200-instance note when data length is 200', () => {
+    mockUseQueryReturn = {
+      data: Array(200).fill({
+        timestamp: '2026-03-06T10:00:00.000Z',
+        description: 'task',
+        promptPreview: 'prompt',
+        fullPrompt: 'full prompt',
+      }),
+      isLoading: false,
+    }
+    render(<SubagentSpawnsDialog {...defaultProps} />)
+    expect(screen.getByText('Showing first 200 instances.')).toBeInTheDocument()
+  })
+})
diff --git a/apps/web/src/components/radar/types.ts b/apps/web/src/components/radar/types.ts
new file mode 100644
index 0000000..67ea1ac
--- /dev/null
+++ b/apps/web/src/components/radar/types.ts
@@ -0,0 +1,6 @@
+export interface DrilldownDialogProps {
+  open: boolean
+  onOpenChange: (open: boolean) => void
+  agentId: string
+  agentName: string
+}