diff --git a/src/main/agent-hooks/server-pi-normalization.test.ts b/src/main/agent-hooks/server-pi-normalization.test.ts
index 2aad513cb78..b351913de6f 100644
--- a/src/main/agent-hooks/server-pi-normalization.test.ts
+++ b/src/main/agent-hooks/server-pi-normalization.test.ts
@@ -450,3 +450,44 @@ describe('a Pi cancel beside a live child row', () => {
     expect(row?.mainAgent).toBeUndefined()
   })
 })
+
+describe('a Pi compaction that tails a finished reply', () => {
+  const turn_completed_at = 1_700_000_005_000
+  let server: AgentHookServer
+
+  beforeEach(async () => {
+    server = new AgentHookServer()
+    await server.start({ env: 'production' })
+  })
+
+  afterEach(() => {
+    server.stop()
+  })
+
+  async function post(payload: Record<string, unknown>): Promise<void> {
+    const response = await postHookEvent(server, buildBody(payload), '/hook/pi')
+    expect(response.status).toBe(204)
+  }
+
+  it('keeps the reply finish time from the compaction rows through settle', async () => {
+    await post({ hook_event_name: 'before_agent_start', prompt: 'summarize' })
+    await post({ hook_event_name: 'message_end', role: 'assistant', text: 'Summary ready.' })
+    await post({ hook_event_name: 'compaction_start', turn_completed_at })
+    expect(server.getStatusSnapshot()[0]).toMatchObject({
+      state: 'working',
+      prompt: 'summarize',
+      lastAssistantMessage: 'Summary ready.',
+      turnCompletedAt: turn_completed_at
+    })
+    await post({ hook_event_name: 'agent_end', turn_completed_at })
+    expect(server.getStatusSnapshot()[0]).toMatchObject({
+      state: 'done',
+      turnCompletedAt: turn_completed_at
+    })
+
+    // The same prompt again is a new turn, not the finished one.
+    await post({ hook_event_name: 'before_agent_start', prompt: 'summarize' })
+    expect(server.getStatusSnapshot()[0]?.state).toBe('working')
+    expect(server.getStatusSnapshot()[0]?.turnCompletedAt).toBeUndefined()
+  })
+})
diff --git a/src/main/pi/agent-status-compaction-source.ts b/src/main/pi/agent-status-compaction-source.ts
new file mode 100644
index 00000000000..8d3d102c6eb
--- /dev/null
+++ b/src/main/pi/agent-status-compaction-source.ts
@@ -0,0 +1,39 @@
+import type { PiAgentKind } from '../../shared/pi-agent-kind'
+
+/** Pi compacts between a finished reply's agent_end and its settle; stamping that compaction
+ *  with the reply's finish lets the host announce it before the compaction ends. */
+export function getPiAgentStatusCompactionHandlerSourceLines(kind: PiAgentKind): string[] {
+  if (kind !== 'pi') {
+    return []
+  }
+
+  return [
+    '  // Why: set only from a finished reply until its settle post, so a later /compact names no old turn.',
+    '  let replyFinishedAt: number | undefined',
+    '',
+    '  function takeCompletedReplyFields(): Record<string, unknown> {',
+    '    const fields = replyFinishedAt === undefined ? {} : { turn_completed_at: replyFinishedAt }',
+    '    replyFinishedAt = undefined',
+    '    return fields',
+    '  }',
+    '',
+    '  // Why: a run cut off mid-tool, failed or aborted has no finished reply to announce.',
+    '  function recordReplyFinish(event): void {',
+    '    let reply: { stopReason?: unknown } | undefined',
+    '    for (const message of Array.isArray(event?.messages) ? event.messages : []) {',
+    "      if (message?.role === 'assistant') reply = message",
+    '    }',
+    "    const finished = reply?.stopReason === 'stop' || reply?.stopReason === 'length'",
+    '    replyFinishedAt = finished && !isOmpRuntime() ? Date.now() : undefined',
+    '  }',
+    '',
+    "  onStatus('session_before_compact', (event, ctx) => {",
+    '    if (replyFinishedAt === undefined || isHeldByChildren()) return',
+    // Why: overflow recovery retries the turn and queued messages continue it after the compaction.
+    "    if (event?.willRetry === true || event?.reason === 'overflow') return",
+    "    if (typeof ctx?.hasPendingMessages === 'function' && ctx.hasPendingMessages()) return",
+    "    post('compaction_start', { turn_completed_at: replyFinishedAt })",
+    '  })',
+    ''
+  ]
+}
diff --git a/src/main/pi/agent-status-compaction.test.ts b/src/main/pi/agent-status-compaction.test.ts
new file mode 100644
index 00000000000..52db618e8b6
--- /dev/null
+++ b/src/main/pi/agent-status-compaction.test.ts
@@ -0,0 +1,112 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import {
+  createAgentStatusExtensionHarness,
+  type AgentStatusExtensionHarness
+} from './agent-status-extension-test-harness'
+import { idle, startAsync } from './agent-status-subagent-event-fixtures'
+
+const busy = { isIdle: () => false }
+
+function reply(stopReason: string): { messages: unknown[] } {
+  return { messages: [{ role: 'user' }, { role: 'assistant', stopReason }] }
+}
+
+// The posts after the run starts, reduced to the fields the host reads for a compaction tail.
+function tail(harness: AgentStatusExtensionHarness): Record<string, unknown>[] {
+  return harness.fetchMock.mock.calls
+    .map((call) => JSON.parse(String(call[1]?.body)).payload)
+    .filter((payload) => payload.hook_event_name !== 'agent_start')
+    .map(({ hook_event_name, turn_completed_at, is_idle }) => ({
+      hook_event_name,
+      turn_completed_at,
+      is_idle
+    }))
+}
+
+// Why: the post queue keeps only the latest pending snapshot, and Pi's compaction posts are minutes apart.
+async function step(
+  harness: AgentStatusExtensionHarness,
+  name: string,
+  event?: unknown,
+  context?: { isIdle: () => boolean; hasPendingMessages?: () => boolean }
+): Promise<void> {
+  await harness.callHook(name, event, context)
+  await vi.advanceTimersByTimeAsync(0)
+}
+
+describe('Pi compaction after a finished reply', () => {
+  beforeEach(() => vi.useFakeTimers())
+  afterEach(() => vi.useRealTimers())
+
+  it('stamps a compaction before settle and the settled completion with the reply finish', async () => {
+    const harness = createAgentStatusExtensionHarness({ kind: 'pi' })
+    await step(harness, 'agent_start')
+    await step(harness, 'agent_end', reply('stop'), busy)
+    await step(harness, 'session_before_compact', { reason: 'threshold', willRetry: false })
+    await step(harness, 'session_compact', {})
+    await step(harness, 'agent_settled', undefined, idle)
+
+    const [start, settled] = tail(harness)
+    expect(start).toEqual({
+      hook_event_name: 'compaction_start',
+      turn_completed_at: expect.any(Number)
+    })
+    expect(settled).toEqual({
+      hook_event_name: 'agent_end',
+      turn_completed_at: start?.turn_completed_at
+    })
+  })
+
+  it.each([
+    {
+      name: 'an overflow retry',
+      run: async (harness: AgentStatusExtensionHarness) => {
+        await step(harness, 'agent_end', reply('stop'), busy)
+        await step(harness, 'session_before_compact', { reason: 'overflow', willRetry: true })
+      }
+    },
+    {
+      name: 'an aborted reply',
+      run: async (harness: AgentStatusExtensionHarness) => {
+        await step(harness, 'agent_end', reply('aborted'), busy)
+        await step(harness, 'session_before_compact', { reason: 'threshold', willRetry: false })
+      }
+    },
+    {
+      name: 'a reply with queued messages that continue the run',
+      run: async (harness: AgentStatusExtensionHarness) => {
+        await step(harness, 'agent_end', reply('stop'), busy)
+        await step(
+          harness,
+          'session_before_compact',
+          { reason: 'threshold', willRetry: false },
+          { isIdle: () => false, hasPendingMessages: () => true }
+        )
+      }
+    },
+    {
+      name: 'a /compact after the reply settled',
+      run: async (harness: AgentStatusExtensionHarness) => {
+        await step(harness, 'agent_end', reply('stop'), busy)
+        await step(harness, 'agent_settled', undefined, idle)
+        await step(harness, 'session_before_compact', { reason: 'manual', willRetry: false })
+      }
+    },
+    {
+      name: 'a reply whose children still run',
+      run: async (harness: AgentStatusExtensionHarness) => {
+        startAsync(harness, 'run-scout', 'scout')
+        await step(harness, 'agent_end', reply('stop'), busy)
+        await step(harness, 'session_before_compact', { reason: 'threshold', willRetry: false })
+      }
+    }
+  ])('posts no compaction tail for $name', async ({ run }) => {
+    const harness = createAgentStatusExtensionHarness({ kind: 'pi' })
+    await step(harness, 'agent_start')
+    await run(harness)
+    await step(harness, 'session_compact', {})
+
+    expect(tail(harness).map((post) => post.hook_event_name)).not.toContain('compaction_start')
+  })
+})
diff --git a/src/main/pi/agent-status-handler-source.ts b/src/main/pi/agent-status-handler-source.ts
index 2b5bf3f8f4b..7ab2e27aa81 100644
--- a/src/main/pi/agent-status-handler-source.ts
+++ b/src/main/pi/agent-status-handler-source.ts
@@ -5,6 +5,7 @@ import type { PiAgentKind } from '../../shared/pi-agent-kind'
 import { getOmpSessionOwnerHandlerSourceLines } from './omp-session-status-owner-source'
 import { getOmpPlanReviewHandlerSourceLines } from './omp-plan-review-source'
 import { getPiAgentStatusUiPromptHandlerSourceLines } from './agent-status-ui-prompt-source'
+import { getPiAgentStatusCompactionHandlerSourceLines } from './agent-status-compaction-source'
 import {
   getPiSubagentRosterEventSourceLines,
   getPiSubagentRosterSetupSourceLines
@@ -29,6 +30,7 @@ export function getPiAgentStatusHandlerSourceLines(kind: PiAgentKind): string[]
           "    post('session_start')",
           ...(kind === 'pi'
             ? [
+                '    replyFinishedAt = undefined',
                 '    restoreParkedSubagents()',
                 // Why: the host reads session_start as an idle session; children still hold this one.
                 "    if (lifecycleState.waiting) post('agent_start')"
@@ -163,7 +165,9 @@ export function getPiAgentStatusHandlerSourceLines(kind: PiAgentKind): string[]
     '    lifecycleState.runGeneration += 1',
     // Why: a turn cannot begin under a dialog holding input focus, so this is the one
     // boundary that can recover a modal whose close never arrived.
-    ...(kind === 'pi' ? ['    piUiPromptDepth = 0', '    piTurnInFlight = true'] : []),
+    ...(kind === 'pi'
+      ? ['    piUiPromptDepth = 0', '    piTurnInFlight = true', '    replyFinishedAt = undefined']
+      : []),
     "    post('agent_start')",
     '  })',
     '',
@@ -193,6 +197,7 @@ export function getPiAgentStatusHandlerSourceLines(kind: PiAgentKind): string[]
     ...approvalHandlers,
     ...(kind === 'prime-agent' ? [] : getOmpPlanReviewHandlerSourceLines()),
     ...getPiAgentStatusUiPromptHandlerSourceLines(kind),
+    ...getPiAgentStatusCompactionHandlerSourceLines(kind),
     ...modelSelectHandler,
     "  // Why: capture the assistant's final text on each completed message",
     '  // so the dashboard preview reflects the most recent reply even before',
@@ -245,7 +250,12 @@ export function getPiAgentStatusHandlerSourceLines(kind: PiAgentKind): string[]
     // and so starts clean on a pane that has not run a turn yet — that pane is idle, not busy.
     ...(kind === 'pi' ? ['    piTurnInFlight = false'] : []),
     // Why: a run that ends because its session did has not completed; the host records it quietly.
-    "    post('agent_end', final ? { session_boundary: true } : {}, final)",
+    ...(kind === 'pi'
+      ? [
+          '    const replyFields = takeCompletedReplyFields()',
+          "    post('agent_end', final ? { session_boundary: true } : replyFields, final)"
+        ]
+      : ["    post('agent_end', final ? { session_boundary: true } : {}, final)"]),
     '    return true',
     '  }',
     '',
@@ -286,6 +296,7 @@ export function getPiAgentStatusHandlerSourceLines(kind: PiAgentKind): string[]
     '      return',
     '    }',
     '    lifecycleState.endedRunGeneration = lifecycleState.runGeneration',
+    ...(kind === 'pi' ? ['    recordReplyFinish(event)'] : []),
     '    if (isOmpRuntime()) {',
     '      postAgentEndOnce()',
     '      return',
diff --git a/src/shared/agent-hook-listener/providers/pi-family-events.ts b/src/shared/agent-hook-listener/providers/pi-family-events.ts
index d7bf5a4b43d..1618fdea30f 100644
--- a/src/shared/agent-hook-listener/providers/pi-family-events.ts
+++ b/src/shared/agent-hook-listener/providers/pi-family-events.ts
@@ -73,11 +73,14 @@ export function normalizePiCompatibleEvent(
   const isPiUiPrompt =
     agentType === 'pi' && (eventName === 'ui_prompt_start' || hookPayload.ui_prompt_active === true)
   const isPiUiPromptEnd = agentType === 'pi' && eventName === 'ui_prompt_end'
+  // Why: Pi posts this only for a compaction between a finished reply and its settle.
+  const isPiCompactionStart = agentType === 'pi' && eventName === 'compaction_start'
 
   let stateName =
     isPiCompatibleAsk || isOmpApprovalRequest || isOmpPlanReview
       ? 'blocked'
       : isOmpApprovalResolution ||
+          isPiCompactionStart ||
           eventName === 'before_agent_start' ||
           eventName === 'agent_start' ||
           eventName === 'tool_call' ||
@@ -125,6 +128,8 @@ export function normalizePiCompatibleEvent(
     lastAssistantMessage: snapshot.lastAssistantMessage,
     lastAssistantMessageIsToolOutput: snapshot.lastAssistantMessageIsToolOutput,
     subagents,
+    // Why: a compaction row and its settle carry one finish time, so the reply is announced once.
+    turnCompletedAt: hookPayload.turn_completed_at,
     // Why: the extension ends a run whose session was replaced; that is not a completed turn.
     ...(eventName === 'agent_end' && hookPayload.session_boundary === true
       ? { sessionBoundary: true }