diff --git a/config/scripts/native-chat-live-session-benchmark.ts b/config/scripts/native-chat-live-session-benchmark.ts
index c21ae759a7f..5983dc2f4e7 100644
--- a/config/scripts/native-chat-live-session-benchmark.ts
+++ b/config/scripts/native-chat-live-session-benchmark.ts
@@ -117,7 +117,7 @@ function blockContent(message: NativeChatMessage): string {
   if (block.type === 'tool-result') {
     return block.output
   }
-  return block.path ?? block.url ?? block.alt ?? ''
+  return block.type === 'image-ref' ? (block.path ?? block.url ?? block.alt ?? '') : block.groupId
 }
 
 function messageWeight(message: NativeChatMessage, content: string): number {
diff --git a/src/main/claude/claude-background-task-tracker.ts b/src/main/claude/claude-background-task-tracker.ts
index a1504a65dec..de24b9a4fba 100644
--- a/src/main/claude/claude-background-task-tracker.ts
+++ b/src/main/claude/claude-background-task-tracker.ts
@@ -20,14 +20,22 @@ function record(value: unknown): Record<string, unknown> | null {
   return typeof value === 'object' && value !== null ? (value as Record<string, unknown>) : null
 }
 
-function taskId(message: Record<string, unknown>): string | null {
-  const value = message.task_id
-  return typeof value === 'string' && value.length > 0 && value.length <= MAX_TASK_ID_LENGTH
-    ? value
-    : null
+/** The bound every task id shares, wherever it enters. An id the roster stores
+ *  becomes a durable entry key, so a provisional one takes the same bound the
+ *  announced path applies — an over-long id is rejected, never truncated. */
+export function isBoundedClaudeTaskId(value: string): boolean {
+  return value.length > 0 && value.length <= MAX_TASK_ID_LENGTH
 }
 
-function taskDescription(value: unknown): string | undefined {
+/** The task's canonical, resume-stable id. Shared with the subagent roster so
+ *  both readers of this channel agree on what identifies a task. */
+export function claudeTaskId(message: Record<string, unknown>): string | null {
+  const value = message.task_id
+  return typeof value === 'string' && isBoundedClaudeTaskId(value) ? value : null
+}
+
+/** A task's human label, collapsed and bounded. */
+export function claudeTaskDescription(value: unknown): string | undefined {
   if (typeof value !== 'string') {
     return undefined
   }
@@ -107,7 +115,7 @@ export class ClaudeBackgroundTaskTracker {
       this.replaceAggregateRoster(message.tasks)
       return true
     }
-    const id = taskId(message)
+    const id = claudeTaskId(message)
     if (!id) {
       return false
     }
@@ -126,13 +134,13 @@ export class ClaudeBackgroundTaskTracker {
       }
       const existing = this.tasks.get(id)
       if (
-        (patch.is_backgrounded === true || taskDescription(patch.description)) &&
+        (patch.is_backgrounded === true || claudeTaskDescription(patch.description)) &&
         (!this.aggregateRosterObserved || existing)
       ) {
         this.upsert(id, {
           backgrounded: patch.is_backgrounded === true || existing?.backgrounded === true,
           kind: existing?.kind ?? 'unknown',
-          description: taskDescription(patch.description) ?? existing?.description
+          description: claudeTaskDescription(patch.description) ?? existing?.description
         })
         return true
       }
@@ -152,7 +160,7 @@ export class ClaudeBackgroundTaskTracker {
     this.upsert(id, {
       backgrounded: message.is_backgrounded === true || kind === 'workflow' || kind === 'monitor',
       kind,
-      description: taskDescription(message.description)
+      description: claudeTaskDescription(message.description)
     })
     return true
   }
@@ -172,14 +180,14 @@ export class ClaudeBackgroundTaskTracker {
       if (!task || task.ambient === true) {
         continue
       }
-      const id = taskId(task)
+      const id = claudeTaskId(task)
       if (!id) {
         continue
       }
       this.tasks.set(id, {
         backgrounded: true,
         kind: classifyClaudeBackgroundTaskKind(task.task_type),
-        description: taskDescription(task.description)
+        description: claudeTaskDescription(task.description)
       })
     }
   }
diff --git a/src/main/claude/claude-structured-item-translation.ts b/src/main/claude/claude-structured-item-translation.ts
index c0ce20908d8..1c1673b59cd 100644
--- a/src/main/claude/claude-structured-item-translation.ts
+++ b/src/main/claude/claude-structured-item-translation.ts
@@ -74,6 +74,18 @@ export function claudeMessageIdentity(
   return { provider: 'claude', sessionId: envelope.sessionId, uuid: envelope.uuid }
 }
 
+/** User bubbles belong to the submitted message; SDK user frames carry echoes
+ *  and tool results, so a user envelope keeps only its tool results. */
+export function claudeOutputEnvelope(envelope: ClaudeMessageEnvelope): ClaudeMessageEnvelope {
+  if (envelope.role !== 'user') {
+    return envelope
+  }
+  return {
+    ...envelope,
+    content: envelope.content.filter((part) => claudeRecord(part)?.type === 'tool_result')
+  }
+}
+
 function messageBlocks(envelope: ClaudeMessageEnvelope): NativeChatBlock[] {
   const blocks: NativeChatBlock[] = []
   for (const value of envelope.content) {
diff --git a/src/main/claude/claude-structured-journal-translation-subagents.test.ts b/src/main/claude/claude-structured-journal-translation-subagents.test.ts
new file mode 100644
index 00000000000..3b280020c31
--- /dev/null
+++ b/src/main/claude/claude-structured-journal-translation-subagents.test.ts
@@ -0,0 +1,259 @@
+import { describe, expect, it, vi } from 'vitest'
+import type {
+  AgentJournalItemBody,
+  AgentJournalItemIdentity
+} from '../../shared/agent-session-journal-types'
+import type {
+  NativeChatSubagentEntry,
+  NativeChatSubagentGroupBlock
+} from '../../shared/native-chat-types'
+import type { StructuredAgentSessionEventSink } from '../native-chat/agent-session-wire/structured-agent-session-event-sink'
+import { createClaudeJournalTranslator } from './claude-structured-journal-translation'
+
+const GROUP_ITEM_ID = 'claude-subagents:claude-session:user-1'
+
+/** The union's other arms carry no client message id, so reading one narrows. */
+function orcaClientMessageId(identity: AgentJournalItemIdentity): string | null {
+  return identity.provider === 'orca' ? identity.clientMessageId : null
+}
+
+function harness() {
+  const items: { identity: AgentJournalItemIdentity; body: AgentJournalItemBody }[] = []
+  const sink: StructuredAgentSessionEventSink = {
+    appendItem: (identity, body) => items.push({ identity, body }),
+    appendTombstone: vi.fn(),
+    publish: vi.fn()
+  }
+  const translator = createClaudeJournalTranslator({ sink, fallbackIdPrefix: 'test' })
+  const groupRows = () =>
+    items.filter((item) => orcaClientMessageId(item.identity) === GROUP_ITEM_ID)
+  const agentsOf = (body: AgentJournalItemBody | undefined): NativeChatSubagentEntry[] => {
+    if (!body || body.kind !== 'message') {
+      return []
+    }
+    const block = body.blocks.find(
+      (candidate): candidate is NativeChatSubagentGroupBlock => candidate.type === 'subagent-group'
+    )
+    return block ? block.agents : []
+  }
+  /** The last roster row written for one group, so a test can read a group that
+   *  is no longer the live one. */
+  const rosterIn = (groupId: string): NativeChatSubagentEntry[] =>
+    agentsOf(
+      items.findLast((item) => orcaClientMessageId(item.identity) === `claude-subagents:${groupId}`)
+        ?.body
+    )
+  const rosterOf = (turnUuid: string): NativeChatSubagentEntry[] =>
+    rosterIn(`claude-session:${turnUuid}`)
+  const roster = (): NativeChatSubagentEntry[] => agentsOf(groupRows().at(-1)?.body)
+  const fallbackRows = (): AgentJournalItemBody[] =>
+    items
+      .filter((item) => (orcaClientMessageId(item.identity) ?? '').startsWith('provider-frame:'))
+      .map((item) => item.body)
+  return { translator, groupRows, roster, rosterIn, rosterOf, fallbackRows }
+}
+
+function userTurn(uuid: string) {
+  return {
+    type: 'message' as const,
+    sessionId: 'orca-session',
+    startsTurn: true as const,
+    message: {
+      type: 'user',
+      uuid,
+      session_id: 'claude-session',
+      parent_tool_use_id: null,
+      message: { role: 'user', content: [{ type: 'text', text: 'go' }] }
+    }
+  }
+}
+
+function systemFrame(subtype: string, fields: Record<string, unknown>) {
+  return {
+    type: 'message' as const,
+    sessionId: 'orca-session',
+    message: { type: 'system', subtype, session_id: 'claude-session', ...fields }
+  }
+}
+
+function spawnResult(uuid: string, toolUseId: string) {
+  return {
+    type: 'message' as const,
+    sessionId: 'orca-session',
+    message: {
+      type: 'user',
+      uuid,
+      session_id: 'claude-session',
+      parent_tool_use_id: null,
+      message: {
+        role: 'user',
+        content: [{ type: 'tool_result', tool_use_id: toolUseId, content: 'done' }]
+      }
+    }
+  }
+}
+
+function resultFrame() {
+  return {
+    type: 'message' as const,
+    sessionId: 'orca-session',
+    message: {
+      type: 'result',
+      subtype: 'success',
+      session_id: 'claude-session',
+      uuid: 'result-1',
+      result: 'ok'
+    }
+  }
+}
+
+describe('claude journal translation — subagents', () => {
+  it('rosters a spawned subagent and settles it on the spawn call result', () => {
+    const { translator, roster, fallbackRows } = harness()
+    translator.handle(userTurn('user-1'))
+    translator.handle(
+      systemFrame('task_started', {
+        task_id: 'task-1',
+        tool_use_id: 'toolu_1',
+        task_type: 'local_agent',
+        subagent_type: 'explorer',
+        description: 'Map the lane'
+      })
+    )
+    expect(roster()).toEqual([
+      expect.objectContaining({ id: 'task-1', label: 'Map the lane', state: 'working' })
+    ])
+    // The task frames stay status-chrome, so none of them prints an opcode row.
+    expect(fallbackRows()).toEqual([])
+    translator.handle(spawnResult('user-2', 'toolu_1'))
+    expect(roster()).toEqual([expect.objectContaining({ state: 'completed' })])
+  })
+
+  it('marks a child still working at turn end unverifiable', () => {
+    const { translator, roster } = harness()
+    translator.handle(userTurn('user-1'))
+    translator.handle(
+      systemFrame('task_started', {
+        task_id: 'task-1',
+        task_type: 'local_agent',
+        description: 'Map the lane'
+      })
+    )
+    translator.handle(resultFrame())
+    expect(roster()).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+  })
+
+  it('leaves a backgrounded child running past the end of its turn', () => {
+    const { translator, roster } = harness()
+    translator.handle(userTurn('user-1'))
+    translator.handle(
+      systemFrame('task_started', {
+        task_id: 'task-1',
+        tool_use_id: 'toolu_1',
+        task_type: 'local_agent',
+        description: 'Watch the build',
+        is_backgrounded: true
+      })
+    )
+    // A backgrounded spawn returns its tool result immediately; the child runs on.
+    translator.handle(spawnResult('user-2', 'toolu_1'))
+    translator.handle(resultFrame())
+    expect(roster()).toEqual([expect.objectContaining({ state: 'working' })])
+    translator.handle({ type: 'ended', sessionId: 'orca-session', reason: 'closed' })
+    expect(roster()).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+  })
+
+  it('keeps a backgrounded shell task out of the roster entirely', () => {
+    const { translator, groupRows } = harness()
+    translator.handle(userTurn('user-1'))
+    translator.handle(
+      systemFrame('task_started', {
+        task_id: 'task-bash',
+        tool_use_id: 'toolu_bash',
+        task_type: 'local_bash',
+        description: 'sleep 20',
+        is_backgrounded: true
+      })
+    )
+    translator.handle(resultFrame())
+    expect(groupRows()).toEqual([])
+  })
+
+  it('shows a subagent whose release announces no task frames, from its child traffic', () => {
+    const { translator, roster } = harness()
+    translator.handle(userTurn('user-1'))
+    translator.handle({
+      type: 'message' as const,
+      sessionId: 'orca-session',
+      message: {
+        type: 'assistant',
+        uuid: 'child-1',
+        session_id: 'claude-session',
+        parent_tool_use_id: 'toolu_1',
+        message: { role: 'assistant', content: [{ type: 'text', text: 'looking' }] }
+      }
+    })
+    expect(roster()).toEqual([
+      expect.objectContaining({ id: 'toolu_1', label: 'subagent', state: 'working' })
+    ])
+  })
+
+  it('settles the turn a new turn superseded, and leaves the new one running', () => {
+    const { translator, rosterOf } = harness()
+    translator.handle(userTurn('user-1'))
+    translator.handle(
+      systemFrame('task_started', {
+        task_id: 'task-1',
+        task_type: 'local_agent',
+        description: 'First turn'
+      })
+    )
+    // A second turn starts with no result frame for the first: the first turn
+    // ends here, and nothing else will ever name its group again.
+    translator.handle(userTurn('user-2'))
+    translator.handle(
+      systemFrame('task_started', {
+        task_id: 'task-2',
+        task_type: 'local_agent',
+        description: 'Second turn'
+      })
+    )
+    expect(rosterOf('user-1')).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+    expect(rosterOf('user-2')).toEqual([expect.objectContaining({ state: 'working' })])
+  })
+
+  it('does not let an unrelated turn end settle a child announced outside a turn', () => {
+    const { translator, rosterIn } = harness()
+    // No turn is live yet, so this child has no turn key to belong to.
+    translator.handle(
+      systemFrame('task_started', {
+        task_id: 'task-early',
+        task_type: 'local_agent',
+        description: 'Before the turn'
+      })
+    )
+    translator.handle(userTurn('user-1'))
+    translator.handle(resultFrame())
+    expect(rosterIn('outside-turn')).toEqual([expect.objectContaining({ state: 'working' })])
+    // The outcome still lands, which a latched `unverifiable` would have lost.
+    translator.handle(
+      systemFrame('task_updated', { task_id: 'task-early', patch: { status: 'completed' } })
+    )
+    expect(rosterIn('outside-turn')).toEqual([expect.objectContaining({ state: 'completed' })])
+  })
+
+  it('settles a child left outside every turn when the session ends', () => {
+    const { translator, rosterIn } = harness()
+    translator.handle(
+      systemFrame('task_started', {
+        task_id: 'task-early',
+        task_type: 'local_agent',
+        description: 'Before the turn'
+      })
+    )
+    translator.handle(userTurn('user-1'))
+    translator.handle(resultFrame())
+    translator.handle({ type: 'ended', sessionId: 'orca-session', reason: 'closed' })
+    expect(rosterIn('outside-turn')).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+  })
+})
diff --git a/src/main/claude/claude-structured-journal-translation.ts b/src/main/claude/claude-structured-journal-translation.ts
index df8e8e67f53..759c2926763 100644
--- a/src/main/claude/claude-structured-journal-translation.ts
+++ b/src/main/claude/claude-structured-journal-translation.ts
@@ -11,9 +11,8 @@ import {
   claudeMessageBody,
   claudeMessageIdentity,
   claudeHasReplayContent,
-  claudeRecord,
+  claudeOutputEnvelope,
   claudeStreamingMessageBody,
-  claudeText,
   claudeThinkingIdentity,
   claudeThinkingText,
   claudeToolBody,
@@ -29,16 +28,15 @@ import {
   claudeQuestionItems
 } from './claude-structured-prompt-items'
 import type { ClaudePromptRegistry } from './claude-structured-prompt-replies'
-import { readableProviderFrameText } from '../native-chat/agent-session-wire/unhandled-provider-frame'
 import { claudeProviderFrameActivity } from '../native-chat/agent-session-wire/provider-frame-activity'
 import {
-  CLAUDE_UNRENDERABLE_CONTENT_TEXT,
+  appendUnmodeledClaudeContent,
   claudeProviderFrameKind,
   claudeResultFailure,
   createClaudeProviderFrameFallback,
-  isModeledClaudeContent,
   isSettledClaudeResultKind
 } from './claude-structured-provider-fallback'
+import { ClaudeSubagentRoster } from './claude-subagent-roster'
 import { createClaudeStreamedBlockRegistry } from './claude-streamed-block-identity'
 import { createClaudeStreamedTextCheckpoints } from './claude-streamed-text-checkpoints'
 
@@ -89,10 +87,16 @@ export function createClaudeJournalTranslator(
   const promptItems = new Map<string, AgentJournalItemIdentity[]>()
   const streamedBlocks = createClaudeStreamedBlockRegistry()
   let currentTurn: { sessionId: string; turnId: string } | null = null
+  const groupKeyOf = (turn: { sessionId: string; turnId: string } | null): string | null =>
+    turn ? `${turn.sessionId}:${turn.turnId}` : null
   const providerFallback = createClaudeProviderFrameFallback(
     deps.sink,
     deps.fallbackIdPrefix ?? 'acquisition'
   )
+  const subagents = new ClaudeSubagentRoster({
+    sink: deps.sink,
+    currentGroupKey: () => groupKeyOf(currentTurn)
+  })
   const streamedText = createClaudeStreamedTextCheckpoints({
     ...(deps.coalesceMs === undefined ? {} : { coalesceMs: deps.coalesceMs }),
     ...(deps.schedule ? { schedule: deps.schedule } : {}),
@@ -144,14 +148,10 @@ export function createClaudeJournalTranslator(
       return false
     }
     let changed = false
-    // User bubbles belong to the submitted message; SDK user frames carry echoes and tool results.
-    const outputEnvelope =
-      envelope.role === 'user'
-        ? {
-            ...envelope,
-            content: envelope.content.filter((part) => claudeRecord(part)?.type === 'tool_result')
-          }
-        : envelope
+    if (envelope.parentToolUseId) {
+      subagents.observeChildActivity(envelope.parentToolUseId)
+    }
+    const outputEnvelope = claudeOutputEnvelope(envelope)
     const body = claudeMessageBody(outputEnvelope)
     // The final frame of a streamed block lands on the block's identity, not its own uuid.
     const identity =
@@ -180,6 +180,8 @@ export function createClaudeJournalTranslator(
         claudeToolIdentity(envelope.sessionId, result.toolUseId),
         claudeToolBody({ tool, result })
       )
+      // A spawn call's result is the parent turn's evidence its child finished.
+      subagents.observeToolResult(result.toolUseId, result.failed)
       // Tool inputs are only needed until their matching result arrives.
       tools.delete(result.toolUseId)
       changed = true
@@ -192,21 +194,7 @@ export function createClaudeJournalTranslator(
       })
       changed = true
     }
-    const unhandledContent = outputEnvelope.content.filter((part) => !isModeledClaudeContent(part))
-    for (const part of unhandledContent) {
-      const partType = claudeText(claudeRecord(part)?.type) ?? 'unknown'
-      providerFallback.append(
-        `message:${envelope.role}:content:${partType}`,
-        part,
-        readableProviderFrameText(part) ?? CLAUDE_UNRENDERABLE_CONTENT_TEXT
-      )
-      changed = true
-    }
-    // An empty user frame is a replay with nothing to show, not an unknown kind.
-    if (envelope.content.length === 0 && envelope.role === 'assistant') {
-      providerFallback.append(`message:${envelope.role}:empty`, message)
-      changed = true
-    }
+    changed = appendUnmodeledClaudeContent(providerFallback, outputEnvelope, message) || changed
     if (
       envelope.role === 'user' &&
       startsTurn &&
@@ -214,6 +202,9 @@ export function createClaudeJournalTranslator(
       message.parent_tool_use_id === null
     ) {
       if (currentTurn) {
+        // A new turn starting is the only end the previous one gets when its
+        // result never arrives; settling it later would sweep THIS turn.
+        subagents.settleTurn(groupKeyOf(currentTurn))
         publishLifecycle(currentTurn.sessionId, currentTurn.turnId, false)
       }
       currentTurn = { sessionId: envelope.sessionId, turnId: envelope.uuid }
@@ -254,6 +245,8 @@ export function createClaudeJournalTranslator(
     handle: (event) => {
       if (event.type === 'ended') {
         streamedText.flush()
+        // No event will ever settle a child once the provider is gone.
+        subagents.settleSession()
         if (currentTurn) {
           publishLifecycle(currentTurn.sessionId, currentTurn.turnId, false)
           currentTurn = null
@@ -274,6 +267,9 @@ export function createClaudeJournalTranslator(
         promptItems.delete(event.promptKey)
         deps.sink.publish()
       } else if (event.type === 'message' && event.message.type === 'result') {
+        // The turn is over however it ended, so a foreground child still
+        // reported as working will never be settled by an event.
+        subagents.settleTurn(groupKeyOf(currentTurn))
         if (currentTurn) {
           publishLifecycle(currentTurn.sessionId, currentTurn.turnId, false)
           currentTurn = null
@@ -291,6 +287,9 @@ export function createClaudeJournalTranslator(
           providerFallback.append(kind, event.message, failure?.text)
         }
       } else if (event.type === 'message') {
+        // These frames stay `status-chrome`: the roster reads them here, and the
+        // fallback below still drops the raw frame instead of printing an opcode.
+        subagents.observeSystemFrame(event.message)
         const kind = claudeProviderFrameKind(event.message)
         if (!handleMessage(event.message, event.startsTurn === true)) {
           providerFallback.append(kind, event.message)
@@ -310,6 +309,7 @@ export function createClaudeJournalTranslator(
       tools.clear()
       promptItems.clear()
       streamedBlocks.clear()
+      subagents.dispose()
     }
   }
 }
diff --git a/src/main/claude/claude-structured-provider-fallback.ts b/src/main/claude/claude-structured-provider-fallback.ts
index 2528ac027df..68aec07976b 100644
--- a/src/main/claude/claude-structured-provider-fallback.ts
+++ b/src/main/claude/claude-structured-provider-fallback.ts
@@ -4,8 +4,15 @@ import {
   DEFAULT_JOURNAL_PAYLOAD_LIMITS
 } from '../native-chat/agent-session-journal/journal-payload-bounds'
 import { CLAUDE_STREAM_JSON_FRAME_KINDS } from '../native-chat/agent-session-wire/claude-stream-json-frame-schema'
-import { unhandledProviderFrameJournalItem } from '../native-chat/agent-session-wire/unhandled-provider-frame'
-import { claudeRecord, claudeText } from './claude-structured-item-translation'
+import {
+  readableProviderFrameText,
+  unhandledProviderFrameJournalItem
+} from '../native-chat/agent-session-wire/unhandled-provider-frame'
+import {
+  claudeRecord,
+  claudeText,
+  type ClaudeMessageEnvelope
+} from './claude-structured-item-translation'
 
 export function claudeProviderFrameKind(message: Record<string, unknown>): string {
   const type = claudeText(message.type) ?? 'unknown'
@@ -123,3 +130,30 @@ export function createClaudeProviderFrameFallback(
     }
   }
 }
+
+export type ClaudeProviderFrameFallback = ReturnType<typeof createClaudeProviderFrameFallback>
+
+/** Journal each content part this build does not model, plus the empty assistant
+ *  frame a replay leaves behind (an empty USER frame is a replay with nothing to
+ *  show, not an unknown kind). Returns whether anything was appended. */
+export function appendUnmodeledClaudeContent(
+  fallback: ClaudeProviderFrameFallback,
+  envelope: ClaudeMessageEnvelope,
+  message: Record<string, unknown>
+): boolean {
+  let changed = false
+  for (const part of envelope.content.filter((part) => !isModeledClaudeContent(part))) {
+    const partType = claudeText(claudeRecord(part)?.type) ?? 'unknown'
+    fallback.append(
+      `message:${envelope.role}:content:${partType}`,
+      part,
+      readableProviderFrameText(part) ?? CLAUDE_UNRENDERABLE_CONTENT_TEXT
+    )
+    changed = true
+  }
+  if (envelope.content.length === 0 && envelope.role === 'assistant') {
+    fallback.append(`message:${envelope.role}:empty`, message)
+    changed = true
+  }
+  return changed
+}
diff --git a/src/main/claude/claude-subagent-group-row.test.ts b/src/main/claude/claude-subagent-group-row.test.ts
new file mode 100644
index 00000000000..2d5ac56e22c
--- /dev/null
+++ b/src/main/claude/claude-subagent-group-row.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, it } from 'vitest'
+import type { NativeChatSubagentEntry } from '../../shared/native-chat-types'
+import { claudeSubagentGroupBody } from './claude-subagent-group-row'
+
+function entry(id: string, state: NativeChatSubagentEntry['state']): NativeChatSubagentEntry {
+  return { id, label: id, state, startedAt: 1 }
+}
+
+/** The fallback sentence is the WHOLE row on mobile and paired web, which have
+ *  no roster renderer, so these assertions are the entire contract there. */
+function sentence(agents: readonly NativeChatSubagentEntry[]): string {
+  const body = claudeSubagentGroupBody('turn-1', agents)
+  const block = body.kind === 'message' ? body.blocks[0] : undefined
+  return block && block.type === 'text' ? block.text : ''
+}
+
+describe('claudeSubagentGroupBody fallback sentence', () => {
+  it('reads as a plain completion when every child completed', () => {
+    expect(sentence([entry('a', 'completed'), entry('b', 'completed')])).toBe('Ran 2 subagents')
+  })
+
+  it('keeps the singular noun for a lone child', () => {
+    expect(sentence([entry('a', 'completed')])).toBe('Ran 1 subagent')
+    expect(sentence([entry('a', 'working')])).toBe('Kicked off 1 subagent')
+  })
+
+  it('names an unverifiable child instead of claiming the group ran', () => {
+    expect(sentence([entry('a', 'completed'), entry('b', 'unverifiable')])).toBe(
+      'Ran 2 subagents (1 unverifiable)'
+    )
+  })
+
+  it('ranks the adverse outcome worst-first', () => {
+    expect(
+      sentence([entry('a', 'failed'), entry('b', 'unverifiable'), entry('c', 'completed')])
+    ).toBe('Ran 3 subagents (1 failed)')
+    expect(sentence([entry('a', 'stopped'), entry('b', 'unverifiable')])).toBe(
+      'Ran 2 subagents (1 stopped)'
+    )
+  })
+
+  it('shows the adverse outcome while a sibling still works', () => {
+    expect(
+      sentence([entry('a', 'working'), entry('b', 'working'), entry('c', 'unverifiable')])
+    ).toBe('Kicked off 3 subagents (1 unverifiable)')
+  })
+
+  it('leaves a benign settled state out of the sentence', () => {
+    expect(sentence([entry('a', 'idle'), entry('b', 'completed')])).toBe('Ran 2 subagents')
+  })
+
+  it('counts every child holding the worst adverse state', () => {
+    expect(sentence([entry('a', 'failed'), entry('b', 'failed'), entry('c', 'stopped')])).toBe(
+      'Ran 3 subagents (2 failed)'
+    )
+  })
+})
diff --git a/src/main/claude/claude-subagent-group-row.ts b/src/main/claude/claude-subagent-group-row.ts
new file mode 100644
index 00000000000..58af6b6b346
--- /dev/null
+++ b/src/main/claude/claude-subagent-group-row.ts
@@ -0,0 +1,32 @@
+// The journal row one Claude spawn group writes: its durable identity and the
+// body it revises in place.
+
+import type {
+  AgentJournalItemBody,
+  AgentJournalItemIdentity
+} from '../../shared/agent-session-journal-types'
+import { subagentGroupFallbackText } from '../../shared/native-chat-subagent-summary'
+import type { NativeChatSubagentEntry } from '../../shared/native-chat-types'
+
+/** Durable journal identity for the group's row — stable across revisions and
+ *  across a restart, so replay finds the same row instead of appending a new one. */
+export function claudeSubagentGroupIdentity(groupId: string): AgentJournalItemIdentity {
+  return { provider: 'orca', clientMessageId: `claude-subagents:${groupId}` }
+}
+
+/** The roster row: the structured block plus the plain sentence an older client
+ *  renders in its place. A message whose only block is the new variant would
+ *  reach such a client with nothing it can draw. */
+export function claudeSubagentGroupBody(
+  groupId: string,
+  agents: readonly NativeChatSubagentEntry[]
+): AgentJournalItemBody {
+  return {
+    kind: 'message',
+    role: 'system',
+    blocks: [
+      { type: 'text', text: subagentGroupFallbackText(agents) },
+      { type: 'subagent-group', groupId, agents: [...agents] }
+    ]
+  }
+}
diff --git a/src/main/claude/claude-subagent-id-aliases.test.ts b/src/main/claude/claude-subagent-id-aliases.test.ts
new file mode 100644
index 00000000000..bffb549d173
--- /dev/null
+++ b/src/main/claude/claude-subagent-id-aliases.test.ts
@@ -0,0 +1,60 @@
+import { describe, expect, it } from 'vitest'
+import { ClaudeSubagentIds } from './claude-subagent-id-aliases'
+
+describe('ClaudeSubagentIds', () => {
+  it('resolves an aliased tool id to its task, and an unaliased id to itself', () => {
+    const ids = new ClaudeSubagentIds()
+    ids.alias('toolu_1', 'task-1')
+    expect(ids.canonical('toolu_1')).toBe('task-1')
+    expect(ids.canonical('toolu_unknown')).toBe('toolu_unknown')
+  })
+
+  it('remembers an exclusion under either of the ids that named it', () => {
+    const ids = new ClaudeSubagentIds()
+    ids.exclude('task-bash')
+    expect(ids.isExcluded('toolu_bash', 'task-bash')).toBe(true)
+    expect(ids.isExcluded(null, null)).toBe(false)
+    expect(ids.isExcluded('task-agent')).toBe(false)
+  })
+
+  it('drops the oldest alias past the bound and keeps the newest', () => {
+    const ids = new ClaudeSubagentIds()
+    for (let index = 0; index <= 512; index += 1) {
+      ids.alias(`toolu_${index}`, `task-${index}`)
+    }
+    // Evicted: the id now stands only for itself.
+    expect(ids.canonical('toolu_0')).toBe('toolu_0')
+    expect(ids.canonical('toolu_512')).toBe('task-512')
+    expect(ids.canonical('toolu_1')).toBe('task-1')
+  })
+
+  it('drops the oldest exclusion past the bound and keeps the newest', () => {
+    const ids = new ClaudeSubagentIds()
+    for (let index = 0; index <= 512; index += 1) {
+      ids.exclude(`task-${index}`)
+    }
+    expect(ids.isExcluded('task-0')).toBe(false)
+    expect(ids.isExcluded('task-512')).toBe(true)
+    expect(ids.isExcluded('task-1')).toBe(true)
+  })
+
+  it('does not retain oversized aliases or exclusions', () => {
+    const ids = new ClaudeSubagentIds()
+    const oversized = 'x'.repeat(513)
+    ids.alias(oversized, 'task-1')
+    ids.alias('tool-1', oversized)
+    ids.exclude(oversized)
+    expect(ids.canonical(oversized)).toBe(oversized)
+    expect(ids.canonical('tool-1')).toBe('tool-1')
+    expect(ids.isExcluded(oversized)).toBe(false)
+  })
+
+  it('forgets everything on clear', () => {
+    const ids = new ClaudeSubagentIds()
+    ids.alias('toolu_1', 'task-1')
+    ids.exclude('task-1')
+    ids.clear()
+    expect(ids.canonical('toolu_1')).toBe('toolu_1')
+    expect(ids.isExcluded('task-1')).toBe(false)
+  })
+})
diff --git a/src/main/claude/claude-subagent-id-aliases.ts b/src/main/claude/claude-subagent-id-aliases.ts
new file mode 100644
index 00000000000..d06bc00bf8d
--- /dev/null
+++ b/src/main/claude/claude-subagent-id-aliases.ts
@@ -0,0 +1,63 @@
+// Which Claude ids name the same subagent, and which name no subagent at all.
+//
+// Claude re-announces a resumed task under a NEW `tool_use_id` while `task_id`
+// stays put, so tool ids are aliases of a canonical task id — a store keyed on
+// the tool id would show the child twice after every resume.
+//
+// The exclusions matter just as much: `task_updated` carries no `task_type` and
+// child traffic carries no task metadata at all, so the one announcement that
+// said "this is a backgrounded shell, not an agent" has to be remembered or a
+// later frame re-admits it.
+
+import { isBoundedClaudeTaskId } from './claude-background-task-tracker'
+
+/** Both maps are event-accumulated and nothing prunes them, so both are bounded. */
+const MAX_TOOL_USE_ALIASES = 512
+const MAX_EXCLUDED_IDS = 512
+
+export class ClaudeSubagentIds {
+  private readonly canonicalByToolUse = new Map<string, string>()
+  private readonly excluded = new Set<string>()
+
+  /** The task id a tool id stands for, or the id itself when nothing aliases it. */
+  canonical(id: string): string {
+    return this.canonicalByToolUse.get(id) ?? id
+  }
+
+  alias(toolUseId: string, taskId: string): void {
+    if (!isBoundedClaudeTaskId(toolUseId) || !isBoundedClaudeTaskId(taskId)) {
+      return
+    }
+    this.canonicalByToolUse.set(toolUseId, taskId)
+    while (this.canonicalByToolUse.size > MAX_TOOL_USE_ALIASES) {
+      const oldest = this.canonicalByToolUse.keys().next()
+      if (oldest.done || oldest.value === toolUseId) {
+        break
+      }
+      this.canonicalByToolUse.delete(oldest.value)
+    }
+  }
+
+  exclude(id: string): void {
+    if (!isBoundedClaudeTaskId(id)) {
+      return
+    }
+    this.excluded.add(id)
+    while (this.excluded.size > MAX_EXCLUDED_IDS) {
+      const oldest = this.excluded.values().next()
+      if (oldest.done || oldest.value === id) {
+        break
+      }
+      this.excluded.delete(oldest.value)
+    }
+  }
+
+  isExcluded(...ids: (string | null)[]): boolean {
+    return ids.some((id) => id !== null && this.excluded.has(id))
+  }
+
+  clear(): void {
+    this.canonicalByToolUse.clear()
+    this.excluded.clear()
+  }
+}
diff --git a/src/main/claude/claude-subagent-roster-state.ts b/src/main/claude/claude-subagent-roster-state.ts
new file mode 100644
index 00000000000..2fa8971d856
--- /dev/null
+++ b/src/main/claude/claude-subagent-roster-state.ts
@@ -0,0 +1,75 @@
+import type { AgentJournalItemIdentity } from '../../shared/agent-session-journal-types'
+import type { NativeChatSubagentEntry } from '../../shared/native-chat-types'
+import type { ClaudeSubagentTaskFrame } from './claude-subagent-task-frames'
+
+const MAX_INVOCATIONS_PER_SUBAGENT = 16
+
+export type TrackedEntry = {
+  entry: NativeChatSubagentEntry
+  /** The only signal separating a child that dies with its turn from one told to
+   *  outlive it. A turn-end sweep must leave a backgrounded child alone. */
+  backgrounded: boolean
+  toolUseId: string | null
+  invocationIds: Set<string> | null
+  /** Label before its ordinal suffix, so a later announcement can tell a
+   *  provisional row from one that already carries the provider's own name. */
+  labelBase: string
+}
+
+export type RosterGroup = {
+  groupId: string
+  identity: AgentJournalItemIdentity
+  /** Insertion order is the display order; the map holds the state. */
+  entries: Map<string, TrackedEntry>
+  /** Lifetime admissions bound retained labels even when entries are removed. */
+  admittedEntries: number
+  /** Labels remain reserved after removal or provisional-name replacement. */
+  claimedLabels: Set<string>
+  /** Last body written, so an idempotent replay writes no new revision. */
+  lastSerialized: string | null
+}
+
+// Invocation history stays with the entry, independent of the evicting alias cache.
+export function applyClaudeSubagentInvocation(
+  tracked: TrackedEntry,
+  frame: ClaudeSubagentTaskFrame,
+  now: () => number
+): boolean {
+  if (tracked.invocationIds === null) {
+    return false
+  }
+  const newInvocation =
+    frame.announcement && frame.toolUseId !== null && !tracked.invocationIds.has(frame.toolUseId)
+  if (newInvocation && frame.toolUseId) {
+    if (tracked.invocationIds.size >= MAX_INVOCATIONS_PER_SUBAGENT) {
+      tracked.invocationIds = null
+      tracked.entry = { ...tracked.entry, state: 'unverifiable', settledAt: now() }
+      return true
+    }
+    tracked.invocationIds.add(frame.toolUseId)
+    if (tracked.toolUseId !== null && tracked.toolUseId !== frame.toolUseId) {
+      tracked.backgrounded = frame.backgrounded ?? false
+      tracked.entry = { ...tracked.entry, state: frame.state ?? 'working', settledAt: undefined }
+    }
+    tracked.toolUseId = frame.toolUseId
+  } else if (tracked.toolUseId && frame.toolUseId && tracked.toolUseId !== frame.toolUseId) {
+    return false
+  }
+  if (tracked.toolUseId === null) {
+    tracked.toolUseId = frame.toolUseId
+  }
+  return true
+}
+
+/** Two children can share a description; the ordinal keeps their rows apart
+ *  without inventing a name the provider never sent. The probe is over the
+ *  labels actually rendered, not a per-base counter: a generated `Audit 2`
+ *  must not collide with a provider that names its own child `Audit 2`. */
+export function claimClaudeSubagentLabel(group: RosterGroup, base: string): string {
+  let candidate = base
+  for (let ordinal = 2; group.claimedLabels.has(candidate); ordinal++) {
+    candidate = `${base} ${ordinal}`
+  }
+  group.claimedLabels.add(candidate)
+  return candidate
+}
diff --git a/src/main/claude/claude-subagent-roster.test.ts b/src/main/claude/claude-subagent-roster.test.ts
new file mode 100644
index 00000000000..da1f16d0a0e
--- /dev/null
+++ b/src/main/claude/claude-subagent-roster.test.ts
@@ -0,0 +1,602 @@
+import { describe, expect, it, vi } from 'vitest'
+import type {
+  AgentJournalItemBody,
+  AgentJournalItemIdentity
+} from '../../shared/agent-session-journal-types'
+import type {
+  NativeChatSubagentEntry,
+  NativeChatSubagentGroupBlock
+} from '../../shared/native-chat-types'
+import type { AgentSessionJournal } from '../native-chat/agent-session-journal/journal-store'
+import {
+  createDeferredStructuredAgentSessionEventSink,
+  type StructuredAgentSessionEventSink
+} from '../native-chat/agent-session-wire/structured-agent-session-event-sink'
+import { ClaudeSubagentRoster } from './claude-subagent-roster'
+
+const TURN_1 = 'claude-session:turn-1'
+
+function agentsOf(body: AgentJournalItemBody | undefined): NativeChatSubagentEntry[] {
+  if (!body || body.kind !== 'message') {
+    return []
+  }
+  const block = body.blocks.find(
+    (candidate): candidate is NativeChatSubagentGroupBlock => candidate.type === 'subagent-group'
+  )
+  return block ? block.agents : []
+}
+
+function isGroupRow(identity: AgentJournalItemIdentity, groupId: string): boolean {
+  return identity.provider === 'orca' && identity.clientMessageId === `claude-subagents:${groupId}`
+}
+
+function harness(groupKey: string | null = TURN_1) {
+  const items: { identity: AgentJournalItemIdentity; body: AgentJournalItemBody }[] = []
+  const tombstones: AgentJournalItemIdentity[] = []
+  const sink: StructuredAgentSessionEventSink = {
+    appendItem: (identity, body) => items.push({ identity, body }),
+    appendTombstone: (identity) => tombstones.push(identity),
+    publish: vi.fn()
+  }
+  let clock = 1_000
+  let key = groupKey
+  const roster = new ClaudeSubagentRoster({
+    sink,
+    currentGroupKey: () => key,
+    now: () => (clock += 1)
+  })
+  const roles = (): NativeChatSubagentEntry[] => agentsOf(items.at(-1)?.body)
+  /** The last row written for one group, so a test can read a row that is no
+   *  longer the newest one. */
+  const rolesIn = (groupId: string): NativeChatSubagentEntry[] =>
+    agentsOf(items.findLast((item) => isGroupRow(item.identity, groupId))?.body)
+  return {
+    roster,
+    items,
+    tombstones,
+    roles,
+    rolesIn,
+    setGroupKey: (next: string | null) => {
+      key = next
+    }
+  }
+}
+
+function system(subtype: string, fields: Record<string, unknown>): Record<string, unknown> {
+  return { type: 'system', subtype, session_id: 'claude-session', ...fields }
+}
+
+function started(fields: Record<string, unknown>): Record<string, unknown> {
+  return system('task_started', { task_type: 'local_agent', ...fields })
+}
+
+describe('ClaudeSubagentRoster', () => {
+  it('builds the row from task_started, with the fallback sentence beside the block', () => {
+    const { roster, items, roles } = harness()
+    roster.observeSystemFrame(
+      started({ task_id: 'task-1', tool_use_id: 'toolu_1', description: 'Review the diff' })
+    )
+    expect(items).toHaveLength(1)
+    expect(items[0]?.identity).toEqual({
+      provider: 'orca',
+      clientMessageId: 'claude-subagents:claude-session:turn-1'
+    })
+    const body = items[0]?.body
+    expect(body?.kind === 'message' && body.blocks[0]).toEqual({
+      type: 'text',
+      text: 'Kicked off 1 subagent'
+    })
+    expect(roles()).toEqual([
+      expect.objectContaining({ id: 'task-1', label: 'Review the diff', state: 'working' })
+    ])
+  })
+
+  it('keeps a backgrounded shell task out of the roster', () => {
+    const { roster, items } = harness()
+    roster.observeSystemFrame(
+      system('task_started', {
+        task_id: 'task-bash',
+        tool_use_id: 'toolu_bash',
+        task_type: 'local_bash',
+        description: 'sleep 20',
+        is_backgrounded: true
+      })
+    )
+    roster.observeSystemFrame(
+      system('task_updated', { task_id: 'task-bash', patch: { status: 'running' } })
+    )
+    // Its own frames carry a tool_use_id, so only the excluded-id memory stops it.
+    roster.observeChildActivity('toolu_bash')
+    expect(items).toHaveLength(0)
+  })
+
+  it('never renders a task marked skip_transcript', () => {
+    const { roster, items } = harness()
+    roster.observeSystemFrame(
+      started({ task_id: 'task-a', tool_use_id: 'toolu_a', skip_transcript: true })
+    )
+    roster.observeSystemFrame(
+      system('task_updated', { task_id: 'task-a', patch: { status: 'completed' } })
+    )
+    roster.observeChildActivity('toolu_a')
+    expect(items).toHaveLength(0)
+  })
+
+  it('drops a provisional row once an announcement says the task is not a subagent', () => {
+    const { roster, items, tombstones, roles } = harness()
+    roster.observeChildActivity('toolu_bash')
+    expect(roles()).toHaveLength(1)
+    roster.observeSystemFrame(
+      system('task_started', {
+        task_id: 'task-bash',
+        tool_use_id: 'toolu_bash',
+        task_type: 'local_bash'
+      })
+    )
+    expect(tombstones).toEqual([
+      { provider: 'orca', clientMessageId: 'claude-subagents:claude-session:turn-1' }
+    ])
+    expect(items).toHaveLength(1)
+  })
+
+  it('does not duplicate a resumed task re-announced under a new tool_use_id', () => {
+    const { roster, roles } = harness()
+    roster.observeSystemFrame(
+      started({ task_id: 'task-1', tool_use_id: 'toolu_first', description: 'Audit' })
+    )
+    roster.observeChildActivity('toolu_first')
+    roster.observeSystemFrame(
+      started({ task_id: 'task-1', tool_use_id: 'toolu_second', description: 'Audit' })
+    )
+    roster.observeChildActivity('toolu_second')
+    expect(roles()).toEqual([
+      expect.objectContaining({ id: 'task-1', label: 'Audit', state: 'working' })
+    ])
+  })
+
+  it('adopts a row built from child traffic when the announcement finally names it', () => {
+    const { roster, roles } = harness()
+    roster.observeChildActivity('toolu_1')
+    expect(roles()).toEqual([expect.objectContaining({ id: 'toolu_1', label: 'subagent' })])
+    roster.observeSystemFrame(
+      started({ task_id: 'task-1', tool_use_id: 'toolu_1', description: 'Explore' })
+    )
+    expect(roles()).toEqual([
+      expect.objectContaining({ id: 'task-1', label: 'Explore', state: 'working' })
+    ])
+  })
+
+  it('is idempotent: a repeated frame writes no new revision', () => {
+    const { roster, items } = harness()
+    const frame = started({ task_id: 'task-1', tool_use_id: 'toolu_1', description: 'Audit' })
+    roster.observeSystemFrame(frame)
+    roster.observeSystemFrame(frame)
+    roster.observeSystemFrame(
+      system('task_updated', { task_id: 'task-1', patch: { status: 'running' } })
+    )
+    expect(items).toHaveLength(1)
+  })
+
+  it('latches a terminal state against a later live report', () => {
+    const { roster, roles } = harness()
+    roster.observeSystemFrame(started({ task_id: 'task-1', description: 'Audit' }))
+    roster.observeSystemFrame(
+      system('task_updated', { task_id: 'task-1', patch: { status: 'failed' } })
+    )
+    roster.observeSystemFrame(
+      system('task_updated', { task_id: 'task-1', patch: { status: 'running' } })
+    )
+    expect(roles()).toEqual([expect.objectContaining({ state: 'failed' })])
+  })
+
+  it('ignores an update for a task it never rostered', () => {
+    const { roster, items } = harness()
+    roster.observeSystemFrame(
+      system('task_updated', { task_id: 'task-unknown', patch: { status: 'running' } })
+    )
+    expect(items).toHaveLength(0)
+  })
+
+  it('disambiguates children that share a description', () => {
+    const { roster, roles } = harness()
+    roster.observeSystemFrame(started({ task_id: 'task-1', description: 'Explore' }))
+    roster.observeSystemFrame(started({ task_id: 'task-2', description: 'Explore' }))
+    expect(roles().map((agent) => agent.label)).toEqual(['Explore', 'Explore 2'])
+  })
+
+  describe('turn end', () => {
+    it('leaves a backgrounded child working and marks a foreground one unverifiable', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(started({ task_id: 'task-fg', description: 'Foreground' }))
+      roster.observeSystemFrame(
+        started({ task_id: 'task-bg', description: 'Background', is_backgrounded: true })
+      )
+      roster.settleTurn(TURN_1)
+      expect(roles()).toEqual([
+        expect.objectContaining({ label: 'Foreground', state: 'unverifiable' }),
+        expect.objectContaining({ label: 'Background', state: 'working' })
+      ])
+    })
+
+    it('never re-settles a child that already reported an outcome', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(started({ task_id: 'task-1', description: 'Audit' }))
+      roster.observeSystemFrame(
+        system('task_updated', { task_id: 'task-1', patch: { status: 'completed' } })
+      )
+      roster.settleTurn(TURN_1)
+      expect(roles()).toEqual([expect.objectContaining({ state: 'completed' })])
+    })
+
+    it('sweeps backgrounded children only when the provider itself is gone', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(
+        started({ task_id: 'task-bg', description: 'Background', is_backgrounded: true })
+      )
+      roster.settleTurn(TURN_1)
+      roster.settleSession()
+      expect(roles()).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+    })
+  })
+
+  describe('spawn tool result', () => {
+    it('settles a foreground child', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: 'toolu_1' }))
+      roster.observeToolResult('toolu_1', false)
+      expect(roles()).toEqual([expect.objectContaining({ state: 'completed' })])
+    })
+
+    it('reports a failed spawn as failed', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: 'toolu_1' }))
+      roster.observeToolResult('toolu_1', true)
+      expect(roles()).toEqual([expect.objectContaining({ state: 'failed' })])
+    })
+
+    it('ignores the immediate result a backgrounded spawn returns', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(
+        started({ task_id: 'task-1', tool_use_id: 'toolu_1', is_backgrounded: true })
+      )
+      roster.observeToolResult('toolu_1', false)
+      expect(roles()).toEqual([expect.objectContaining({ state: 'working' })])
+    })
+
+    it('ignores results for tools that are not spawn calls', () => {
+      const { roster, items } = harness()
+      roster.observeToolResult('toolu_read', false)
+      expect(items).toHaveLength(0)
+    })
+  })
+
+  describe('label ordinals', () => {
+    it('never re-issues an ordinal a removed row gave up', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(started({ task_id: 'task-1', description: 'Audit' }))
+      roster.observeSystemFrame(started({ task_id: 'task-2', description: 'Audit' }))
+      // task-1 is re-announced as a shell task, so its row goes; reclaiming the
+      // ordinal it held would print a second 'Audit 2' beside the one still shown.
+      roster.observeSystemFrame(
+        system('task_started', { task_id: 'task-1', task_type: 'local_bash' })
+      )
+      roster.observeSystemFrame(started({ task_id: 'task-3', description: 'Audit' }))
+      expect(roles().map((agent) => agent.label)).toEqual(['Audit 2', 'Audit 3'])
+    })
+
+    it('never generates a label a provider-supplied one already took', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(started({ task_id: 'task-1', description: 'Audit' }))
+      roster.observeSystemFrame(started({ task_id: 'task-2', description: 'Audit' }))
+      // The provider's own name for the third child is the label the ordinal just
+      // generated for the second; a per-base counter would print it twice.
+      roster.observeSystemFrame(started({ task_id: 'task-3', description: 'Audit 2' }))
+      const labels = roles().map((agent) => agent.label)
+      expect(labels).toEqual(['Audit', 'Audit 2', 'Audit 2 2'])
+      expect(new Set(labels).size).toBe(labels.length)
+    })
+  })
+
+  describe('child traffic for an id the CLI never declared', () => {
+    it('creates nothing once the CLI has announced any task at all', () => {
+      const { roster, items } = harness()
+      // A rejected announcement still proves this CLI declares what it spawns.
+      roster.observeSystemFrame(
+        system('task_started', { task_id: 'task-bash', task_type: 'local_bash' })
+      )
+      roster.observeChildActivity('toolu_never_announced')
+      expect(items).toHaveLength(0)
+    })
+
+    it('rejects an over-long provisional id instead of storing it as an entry id', () => {
+      const { roster, items } = harness()
+      // The announced path drops an id past `claudeTaskId`'s bound; the
+      // provisional one writes the same durable entry id, so it must too.
+      roster.observeChildActivity(`toolu_${'x'.repeat(512)}`)
+      expect(items).toHaveLength(0)
+      roster.observeChildActivity(`toolu_${'x'.repeat(500)}`)
+      expect(items).toHaveLength(1)
+    })
+
+    it('still rosters a subagent announced after a task the filter rejected', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(
+        system('task_started', { task_id: 'task-bash', task_type: 'local_bash' })
+      )
+      // The gate closes the child-traffic fallback, never the announcement path.
+      roster.observeSystemFrame(
+        started({ task_id: 'task-1', tool_use_id: 'toolu_1', description: 'Explore' })
+      )
+      roster.observeChildActivity('toolu_1')
+      expect(roles()).toEqual([
+        expect.objectContaining({ id: 'task-1', label: 'Explore', state: 'working' })
+      ])
+    })
+
+    it('leaves a grandchild parented inside the sidechain out of the roster', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(
+        started({ task_id: 'task-1', tool_use_id: 'toolu_1', description: 'Explore' })
+      )
+      roster.observeChildActivity('toolu_1')
+      // A tool the subagent itself ran: never announced, so never excluded either.
+      roster.observeChildActivity('toolu_inner')
+      expect(roles()).toEqual([
+        expect.objectContaining({ id: 'task-1', label: 'Explore', state: 'working' })
+      ])
+    })
+
+    it('still mints the provisional row for a release that announces no task', () => {
+      const { roster, roles } = harness()
+      roster.observeChildActivity('toolu_1')
+      // Not an announcement: the fallback path stays open for this release.
+      roster.observeSystemFrame(
+        system('task_updated', { task_id: 'task-x', patch: { status: 'running' } })
+      )
+      roster.observeChildActivity('toolu_2')
+      expect(roles().map((agent) => agent.label)).toEqual(['subagent', 'subagent 2'])
+    })
+  })
+
+  describe('groups that no later event can reach', () => {
+    it('loses contact with a group evicted past the bound', () => {
+      const { roster, rolesIn, setGroupKey } = harness('turn-0')
+      for (let index = 0; index < 33; index += 1) {
+        setGroupKey(`turn-${index}`)
+        roster.observeSystemFrame(started({ task_id: `task-${index}`, description: 'Audit' }))
+      }
+      expect(rolesIn('turn-0')).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+      expect(rolesIn('turn-32')).toEqual([expect.objectContaining({ state: 'working' })])
+    })
+
+    it('loses contact with a live child when the translator is disposed without an end', () => {
+      const { roster, roles } = harness()
+      roster.observeSystemFrame(
+        started({ task_id: 'task-bg', description: 'Background', is_backgrounded: true })
+      )
+      roster.dispose()
+      expect(roles()).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+    })
+
+    it('writes nothing on dispose when the session already settled', () => {
+      const { roster, items } = harness()
+      roster.observeSystemFrame(started({ task_id: 'task-1', description: 'Audit' }))
+      roster.settleSession()
+      const written = items.length
+      roster.dispose()
+      expect(items).toHaveLength(written)
+    })
+  })
+
+  it('groups children outside any turn under their own row', () => {
+    const { roster, items } = harness(null)
+    roster.observeSystemFrame(started({ task_id: 'task-1', description: 'Audit' }))
+    expect(items[0]?.identity).toEqual({
+      provider: 'orca',
+      clientMessageId: 'claude-subagents:outside-turn'
+    })
+  })
+})
+
+describe('ClaudeSubagentRoster — the turn that is ending', () => {
+  it('leaves a child announced outside any turn alone when an unrelated turn ends', () => {
+    const { roster, rolesIn, setGroupKey } = harness(null)
+    roster.observeSystemFrame(started({ task_id: 'task-early', description: 'Early' }))
+    setGroupKey(TURN_1)
+    roster.observeSystemFrame(started({ task_id: 'task-turn', description: 'In turn' }))
+    roster.settleTurn(TURN_1)
+    expect(rolesIn('outside-turn')).toEqual([expect.objectContaining({ state: 'working' })])
+    expect(rolesIn(TURN_1)).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+    // `unverifiable` latches, so sweeping it above would have swallowed this.
+    roster.observeSystemFrame(
+      system('task_updated', { task_id: 'task-early', patch: { status: 'completed' } })
+    )
+    expect(rolesIn('outside-turn')).toEqual([expect.objectContaining({ state: 'completed' })])
+  })
+
+  it('sweeps the outside-turn group when a turn with no key of its own ends', () => {
+    const { roster, rolesIn } = harness(null)
+    roster.observeSystemFrame(started({ task_id: 'task-early', description: 'Early' }))
+    roster.settleTurn(null)
+    expect(rolesIn('outside-turn')).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+  })
+
+  it('still settles an outside-turn child once the session itself ends', () => {
+    const { roster, rolesIn, setGroupKey } = harness(null)
+    roster.observeSystemFrame(started({ task_id: 'task-early', description: 'Early' }))
+    setGroupKey(TURN_1)
+    roster.observeSystemFrame(started({ task_id: 'task-turn', description: 'In turn' }))
+    roster.settleTurn(TURN_1)
+    roster.settleSession()
+    expect(rolesIn('outside-turn')).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+  })
+
+  it('sweeps the turn that ended, not whichever turn is live now', () => {
+    const { roster, rolesIn, setGroupKey } = harness()
+    roster.observeSystemFrame(started({ task_id: 'task-1', description: 'First turn' }))
+    setGroupKey('claude-session:turn-2')
+    roster.observeSystemFrame(started({ task_id: 'task-2', description: 'Second turn' }))
+    // Turn 1's result lands after turn 2 has already begun.
+    roster.settleTurn(TURN_1)
+    expect(rolesIn(TURN_1)).toEqual([expect.objectContaining({ state: 'unverifiable' })])
+    expect(rolesIn('claude-session:turn-2')).toEqual([
+      expect.objectContaining({ state: 'working' })
+    ])
+  })
+})
+
+describe('ClaudeSubagentRoster — through the real sink queue', () => {
+  it('lands every revision, not just the one that was already in flight', async () => {
+    const appended: AgentJournalItemBody[] = []
+    let published = 0
+    const journal = {
+      appendItem: async (_identity: AgentJournalItemIdentity, body: AgentJournalItemBody) => {
+        appended.push(body)
+        return { cursor: { epoch: 'e', sequence: appended.length } }
+      },
+      appendTombstone: async () => ({ epoch: 'e', sequence: 0 })
+    } as unknown as AgentSessionJournal
+    const deferred = createDeferredStructuredAgentSessionEventSink()
+    deferred.bind({
+      journal,
+      fence: 1,
+      publish: () => {
+        published += 1
+      }
+    })
+    const roster = new ClaudeSubagentRoster({ sink: deferred.sink, currentGroupKey: () => TURN_1 })
+
+    // The first append is in flight while the rest are submitted, so a publish
+    // sharing the row's coalescing key would evict them.
+    roster.observeSystemFrame(started({ task_id: 'task-1', description: 'One' }))
+    roster.observeSystemFrame(started({ task_id: 'task-2', description: 'Two' }))
+    roster.observeSystemFrame(
+      system('task_updated', { task_id: 'task-1', patch: { status: 'completed' } })
+    )
+    const drained = await deferred.drained()
+
+    expect(drained).toEqual({ ok: true })
+    expect(agentsOf(appended.at(-1))).toEqual([
+      expect.objectContaining({ id: 'task-1', label: 'One', state: 'completed' }),
+      expect.objectContaining({ id: 'task-2', label: 'Two', state: 'working' })
+    ])
+    expect(published).toBeGreaterThan(0)
+  })
+})
+
+describe('ClaudeSubagentRoster — authoritative outcomes and retained budgets', () => {
+  it('accepts a notification after the foreground turn lost contact', () => {
+    const { roster, roles } = harness()
+    roster.observeSystemFrame(started({ task_id: 'task-1' }))
+    roster.settleTurn(TURN_1)
+    roster.observeSystemFrame(
+      system('task_notification', { task_id: 'task-1', status: 'completed' })
+    )
+    expect(roles()).toEqual([expect.objectContaining({ state: 'completed' })])
+  })
+
+  it('settles a background child from its notification without a task_updated', () => {
+    const { roster, roles } = harness()
+    roster.observeSystemFrame(started({ task_id: 'task-1', is_backgrounded: true }))
+    roster.settleTurn(TURN_1)
+    roster.observeSystemFrame(system('task_notification', { task_id: 'task-1', status: 'failed' }))
+    expect(roles()).toEqual([expect.objectContaining({ state: 'failed' })])
+  })
+
+  it('bounds lifetime admissions when reclassification repeatedly removes entries', () => {
+    const { roster, items } = harness()
+    for (let i = 0; i < 100; i++) {
+      roster.observeSystemFrame(started({ task_id: `task-${i}`, description: `Agent ${i}` }))
+      roster.observeSystemFrame(
+        system('task_started', { task_id: `task-${i}`, task_type: 'local_bash' })
+      )
+    }
+    expect(items).toHaveLength(64)
+  })
+})
+
+describe('ClaudeSubagentRoster — resumed invocation', () => {
+  it('reopens one canonical child on a new announcement without replaying old results', () => {
+    const { roster, roles } = harness()
+    roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: 'first' }))
+    roster.observeToolResult('first', false)
+    roster.observeSystemFrame(
+      started({ task_id: 'task-1', tool_use_id: 'resumed', is_backgrounded: true })
+    )
+    expect(roles()).toEqual([expect.objectContaining({ id: 'task-1', state: 'working' })])
+    expect(roles()[0].settledAt).toBeUndefined()
+    roster.observeSystemFrame(
+      system('task_notification', { task_id: 'task-1', tool_use_id: 'first', status: 'completed' })
+    )
+    roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: 'first' }))
+    expect(roles()[0].state).toBe('working')
+    roster.observeSystemFrame(
+      system('task_notification', {
+        task_id: 'task-1',
+        tool_use_id: 'resumed',
+        status: 'completed'
+      })
+    )
+    roster.observeSystemFrame(
+      started({ task_id: 'task-1', tool_use_id: 'resumed', is_backgrounded: true })
+    )
+    expect(roles()[0].state).toBe('completed')
+  })
+})
+
+describe('ClaudeSubagentRoster — invocation fences', () => {
+  it('ignores a previous invocation tool result even without a background flag', () => {
+    const { roster, roles } = harness()
+    roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: 'first' }))
+    roster.observeToolResult('first', false)
+    roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: 'next' }))
+    roster.observeToolResult('first', true)
+    expect(roles()[0].state).toBe('working')
+    roster.observeToolResult('next', false)
+    expect(roles()[0].state).toBe('completed')
+  })
+
+  it('does not treat an evicted alias as a new invocation', () => {
+    const { roster, rolesIn, setGroupKey } = harness()
+    roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: 'first' }))
+    roster.observeToolResult('first', false)
+    setGroupKey('churn')
+    for (let i = 0; i < 513; i++) {
+      roster.observeSystemFrame(
+        system('task_updated', { task_id: `other-${i}`, tool_use_id: `tool-${i}` })
+      )
+    }
+    roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: 'first' }))
+    expect(rolesIn(TURN_1)[0].state).toBe('completed')
+  })
+
+  it('bounds invocation history and refuses to reopen beyond the retained budget', () => {
+    const { roster, roles } = harness()
+    for (let i = 0; i < 20; i++) {
+      roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: `tool-${i}` }))
+      if (i >= 16) {
+        expect(roles()[0].state).toBe('unverifiable')
+      }
+      roster.observeToolResult(`tool-${i}`, false)
+    }
+    roster.observeSystemFrame(started({ task_id: 'task-1', tool_use_id: 'tool-0' }))
+    expect(roles()[0].state).toBe('unverifiable')
+  })
+})
+
+it('merges an explicit foreground patch without clearing on absent metadata', () => {
+  const { roster, roles } = harness()
+  roster.observeSystemFrame(
+    started({ task_id: 'task-1', tool_use_id: 'tool', is_backgrounded: true })
+  )
+  roster.observeSystemFrame(
+    system('task_updated', { task_id: 'task-1', patch: { description: 'Audit' } })
+  )
+  roster.observeToolResult('tool', false)
+  expect(roles()[0].state).toBe('working')
+  roster.observeSystemFrame(
+    system('task_updated', { task_id: 'task-1', patch: { is_backgrounded: false } })
+  )
+  roster.observeToolResult('tool', false)
+  expect(roles()[0].state).toBe('completed')
+})
diff --git a/src/main/claude/claude-subagent-roster.ts b/src/main/claude/claude-subagent-roster.ts
new file mode 100644
index 00000000000..34083f2ee8c
--- /dev/null
+++ b/src/main/claude/claude-subagent-roster.ts
@@ -0,0 +1,388 @@
+// The Claude subagent roster: one journal row per turn that spawned children.
+//
+// Entries are built from `task_started`, never from child traffic: a
+// BACKGROUNDED subagent emits no child frames at all, so a roster fed by
+// `parent_tool_use_id` alone would leave every one of them an unlabelled row
+// forever. Child traffic only creates an entry for CLI releases that announce
+// no task frames.
+//
+// Claude re-announces a resumed task under a NEW `tool_use_id`, so `task_id` is
+// the key and tool ids are aliases; keying on the tool id would duplicate the
+// child on every resume. Outcomes latch within an invocation; a new spawn
+// alias can reopen it, and authoritative evidence can correct lost contact.
+
+import {
+  canReplaceSubagentState,
+  isTerminalSubagentState
+} from '../../shared/native-chat-subagent-summary'
+import type { NativeChatSubagentEntry } from '../../shared/native-chat-types'
+import type { StructuredAgentSessionEventSink } from '../native-chat/agent-session-wire/structured-agent-session-event-sink'
+import { isBoundedClaudeTaskId } from './claude-background-task-tracker'
+import { claudeSubagentGroupBody, claudeSubagentGroupIdentity } from './claude-subagent-group-row'
+import { ClaudeSubagentIds } from './claude-subagent-id-aliases'
+import { readClaudeSubagentTaskFrame } from './claude-subagent-task-frames'
+import {
+  applyClaudeSubagentInvocation,
+  claimClaudeSubagentLabel,
+  type RosterGroup,
+  type TrackedEntry
+} from './claude-subagent-roster-state'
+
+/** Spawn-group rows kept live per session, and children per row. Both bound an
+ *  event-accumulated map that no provider snapshot ever prunes. */
+const MAX_SUBAGENT_GROUPS = 32
+const MAX_SUBAGENTS_PER_GROUP = 64
+
+/** The turn a group belongs to when Claude reports a task outside any turn. */
+const OUTSIDE_TURN = 'outside-turn'
+
+const UNLABELLED_AGENT = 'subagent'
+
+export type ClaudeSubagentRosterDeps = {
+  sink: StructuredAgentSessionEventSink
+  /** The turn that owns children spawned right now; null outside any turn. */
+  currentGroupKey: () => string | null
+  now?: () => number
+}
+
+export class ClaudeSubagentRoster {
+  private readonly groups = new Map<string, RosterGroup>()
+  /** Canonical id → the group holding its entry, so a late update for a child
+   *  from an earlier turn revises that turn's row instead of the live one. */
+  private readonly groupIdByEntry = new Map<string, string>()
+  private readonly ids = new ClaudeSubagentIds()
+  /** Set by ANY `task_started`, including one the subagent filter rejects. Once
+   *  this CLI has proven it declares its tasks, child traffic for an id it never
+   *  announced is a nested tool or a grandchild, not a subagent. */
+  private announcesTasks = false
+  private readonly now: () => number
+
+  constructor(private readonly deps: ClaudeSubagentRosterDeps) {
+    this.now = deps.now ?? (() => Date.now())
+  }
+
+  /** Consume a `message:system:task_*` frame. Returns false when it is not one. */
+  observeSystemFrame(message: Record<string, unknown>): boolean {
+    const frame = readClaudeSubagentTaskFrame(message)
+    if (!frame) {
+      return false
+    }
+    this.announcesTasks ||= frame.announcement
+    if (frame.excluded) {
+      // Child traffic may already have built a provisional row under the tool id;
+      // the announcement is the first frame that says it is not a subagent.
+      for (const id of [frame.taskId, frame.toolUseId]) {
+        if (id !== null) {
+          this.ids.exclude(id)
+          this.remove(id)
+        }
+      }
+      return true
+    }
+    if (this.ids.isExcluded(frame.taskId, frame.toolUseId)) {
+      return true
+    }
+    if (frame.toolUseId) {
+      this.ids.alias(frame.toolUseId, frame.taskId)
+    }
+    const located =
+      this.locate(frame.taskId) ??
+      (frame.toolUseId ? this.adopt(frame.toolUseId, frame.taskId) : null)
+    if (!located) {
+      if (frame.announcesSubagent) {
+        this.create(
+          frame.taskId,
+          frame.label,
+          frame.state ?? 'working',
+          frame.backgrounded ?? false,
+          frame.toolUseId
+        )
+      }
+      return true
+    }
+    const tracked = located.group.entries.get(frame.taskId)
+    if (tracked && !applyClaudeSubagentInvocation(tracked, frame, this.now)) {
+      return true
+    }
+    this.revise(located.group, frame.taskId, {
+      label: frame.label,
+      state: frame.state,
+      backgrounded: frame.backgrounded
+    })
+    return true
+  }
+
+  /**
+   * A frame carrying `parent_tool_use_id` — the child's own traffic. It refreshes
+   * nothing on an announced child; it exists so a CLI release that sends no task
+   * frames still shows the subagent it is running.
+   */
+  observeChildActivity(parentToolUseId: string): void {
+    const canonical = this.ids.canonical(parentToolUseId)
+    if (this.ids.isExcluded(parentToolUseId, canonical)) {
+      return
+    }
+    if (this.locate(canonical)) {
+      return
+    }
+    if (this.announcesTasks) {
+      // A nested Task, a workflow child, or a grandchild parented to a tool id
+      // inside the sidechain all reach here. This CLI announces what it spawns,
+      // so an id it never declared cannot be a subagent — and a row invented for
+      // one is unlabelled forever and can only ever end `unverifiable`. The
+      // bounded exclusion set cannot cover an id that was never announced.
+      return
+    }
+    if (!isBoundedClaudeTaskId(canonical)) {
+      // `claudeTaskId` rejects an over-long announced id rather than truncating
+      // it; a provisional id becomes the same durable entry key, so it cannot
+      // enter under a looser rule.
+      return
+    }
+    this.create(canonical, null, 'working', false, parentToolUseId)
+  }
+
+  /**
+   * The parent turn's tool result for a spawn call. It settles a foreground
+   * child, whose result IS the turn's evidence the child finished. A backgrounded
+   * child's spawn call returns immediately while the child keeps running, so its
+   * result proves nothing and is ignored.
+   */
+  observeToolResult(toolUseId: string, failed: boolean): void {
+    const canonical = this.ids.canonical(toolUseId)
+    const located = this.locate(canonical)
+    if (
+      !located ||
+      located.tracked.invocationIds === null ||
+      located.tracked.backgrounded ||
+      (located.tracked.toolUseId !== null && located.tracked.toolUseId !== toolUseId)
+    ) {
+      return
+    }
+    this.revise(located.group, canonical, {
+      label: null,
+      state: failed ? 'failed' : 'completed',
+      backgrounded: false
+    })
+  }
+
+  /**
+   * The parent turn ended. A foreground child still reported as working will
+   * never be settled by an event, so it becomes `unverifiable`: contact was
+   * lost, which is NOT evidence the child exited. A backgrounded child was
+   * explicitly told to outlive the turn and is left alone.
+   */
+  settleTurn(groupKey: string | null): void {
+    // Only the group this key names. `OUTSIDE_TURN` belongs to no turn, so an
+    // unrelated turn ending is no evidence about a child announced outside it.
+    // `settleSession` reaches what no turn does.
+    this.sweep(this.groups.get(groupKey ?? OUTSIDE_TURN), false)
+  }
+
+  /** The provider is gone. Nothing more will arrive for any child, backgrounded
+   *  or not, so every one of them loses contact at once. */
+  settleSession(): void {
+    for (const group of this.groups.values()) {
+      this.sweep(group, true)
+    }
+  }
+
+  dispose(): void {
+    // Teardown paths reach here without an `ended` event, so a row still
+    // reporting `working` would have nothing left to revise it. A session that
+    // did settle first leaves every child terminal, so this writes nothing.
+    this.settleSession()
+    this.groups.clear()
+    this.groupIdByEntry.clear()
+    this.ids.clear()
+    this.announcesTasks = false
+  }
+
+  private sweep(group: RosterGroup | undefined, includeBackgrounded: boolean): void {
+    if (!group) {
+      return
+    }
+    let changed = false
+    for (const [id, tracked] of group.entries) {
+      if (isTerminalSubagentState(tracked.entry.state)) {
+        continue
+      }
+      if (tracked.backgrounded && !includeBackgrounded) {
+        continue
+      }
+      group.entries.set(id, {
+        ...tracked,
+        entry: { ...tracked.entry, state: 'unverifiable', settledAt: this.now() }
+      })
+      changed = true
+    }
+    if (changed) {
+      this.write(group)
+    }
+  }
+
+  private create(
+    id: string,
+    label: string | null,
+    state: NativeChatSubagentEntry['state'],
+    backgrounded: boolean,
+    toolUseId: string | null
+  ): void {
+    const group = this.groupFor()
+    if (group.admittedEntries >= MAX_SUBAGENTS_PER_GROUP) {
+      return
+    }
+    group.admittedEntries += 1
+    const now = this.now()
+    const labelBase = label ?? UNLABELLED_AGENT
+    group.entries.set(id, {
+      backgrounded,
+      toolUseId,
+      invocationIds: new Set(toolUseId ? [toolUseId] : []),
+      labelBase,
+      entry: {
+        id,
+        label: claimClaudeSubagentLabel(group, labelBase),
+        state,
+        startedAt: now,
+        ...(isTerminalSubagentState(state) ? { settledAt: now } : {})
+      }
+    })
+    this.groupIdByEntry.set(id, group.groupId)
+    this.write(group)
+  }
+
+  private revise(
+    group: RosterGroup,
+    id: string,
+    change: {
+      label: string | null
+      state: NativeChatSubagentEntry['state'] | null
+      backgrounded: boolean | null
+    }
+  ): void {
+    const tracked = group.entries.get(id)
+    if (!tracked) {
+      return
+    }
+    const next: TrackedEntry = {
+      ...tracked,
+      backgrounded: change.backgrounded ?? tracked.backgrounded,
+      entry: { ...tracked.entry }
+    }
+    // A provisional row built from child traffic takes the real name the first
+    // announcement carries; an announced row keeps the name it was given.
+    if (
+      change.label &&
+      tracked.labelBase === UNLABELLED_AGENT &&
+      change.label !== UNLABELLED_AGENT
+    ) {
+      next.labelBase = change.label
+      next.entry.label = claimClaudeSubagentLabel(group, change.label)
+    }
+    // Proven outcomes latch; lost contact can still receive a later verdict.
+    if (change.state && canReplaceSubagentState(tracked.entry.state, change.state)) {
+      next.entry.state = change.state
+      if (isTerminalSubagentState(change.state)) {
+        next.entry.settledAt = this.now()
+      }
+    }
+    group.entries.set(id, next)
+    this.write(group)
+  }
+
+  /** Re-key a provisional entry from its tool id onto the canonical task id the
+   *  announcement finally named, so the child does not appear twice. */
+  private adopt(toolUseId: string, taskId: string): { group: RosterGroup } | null {
+    if (toolUseId === taskId) {
+      return null
+    }
+    const located = this.locate(toolUseId)
+    if (!located) {
+      return null
+    }
+    located.group.entries.delete(toolUseId)
+    located.group.entries.set(taskId, {
+      ...located.tracked,
+      entry: { ...located.tracked.entry, id: taskId }
+    })
+    this.groupIdByEntry.delete(toolUseId)
+    this.groupIdByEntry.set(taskId, located.group.groupId)
+    return { group: located.group }
+  }
+
+  private remove(id: string): void {
+    const located = this.locate(id)
+    if (!located) {
+      return
+    }
+    located.group.entries.delete(id)
+    this.groupIdByEntry.delete(id)
+    this.write(located.group)
+  }
+
+  private locate(id: string): { group: RosterGroup; tracked: TrackedEntry } | null {
+    const groupId = this.groupIdByEntry.get(id)
+    const group = groupId === undefined ? undefined : this.groups.get(groupId)
+    const tracked = group?.entries.get(id)
+    return group && tracked ? { group, tracked } : null
+  }
+
+  private groupFor(): RosterGroup {
+    const groupId = this.deps.currentGroupKey() ?? OUTSIDE_TURN
+    const existing = this.groups.get(groupId)
+    if (existing) {
+      return existing
+    }
+    const group: RosterGroup = {
+      groupId,
+      identity: claudeSubagentGroupIdentity(groupId),
+      entries: new Map(),
+      admittedEntries: 0,
+      claimedLabels: new Set(),
+      lastSerialized: null
+    }
+    this.groups.set(groupId, group)
+    while (this.groups.size > MAX_SUBAGENT_GROUPS) {
+      const oldest = this.groups.keys().next()
+      if (oldest.done || oldest.value === groupId) {
+        break
+      }
+      const evicted = this.groups.get(oldest.value)
+      // Once the group leaves the map nothing can reach its children again —
+      // not even a session sweep — so contact is lost here.
+      this.sweep(evicted, true)
+      for (const id of evicted?.entries.keys() ?? []) {
+        this.groupIdByEntry.delete(id)
+      }
+      this.groups.delete(oldest.value)
+    }
+    return group
+  }
+
+  private write(group: RosterGroup): void {
+    const agents = [...group.entries.values()].map((tracked) => tracked.entry)
+    const options = { coalescingKey: `claude-subagents:${group.groupId}` }
+    if (agents.length === 0) {
+      // The row's last child turned out not to be a subagent. An empty roster is
+      // not a roster of nothing, so the row goes rather than reading "Ran 0".
+      if (group.lastSerialized !== null) {
+        group.lastSerialized = null
+        this.deps.sink.appendTombstone(group.identity, options)
+        this.deps.sink.publish()
+      }
+      return
+    }
+    const body = claudeSubagentGroupBody(group.groupId, agents)
+    const serialized = JSON.stringify(body)
+    if (serialized === group.lastSerialized) {
+      // Nothing changed — a duplicate delivery must not burn a revision.
+      return
+    }
+    group.lastSerialized = serialized
+    this.deps.sink.appendItem(group.identity, body, options)
+    // Publish keeps the sink's own coalescing slot: sharing the row's key makes
+    // each queued publish evict the append it was meant to flush.
+    this.deps.sink.publish()
+  }
+}
diff --git a/src/main/claude/claude-subagent-task-frames.test.ts b/src/main/claude/claude-subagent-task-frames.test.ts
new file mode 100644
index 00000000000..230ef45e19c
--- /dev/null
+++ b/src/main/claude/claude-subagent-task-frames.test.ts
@@ -0,0 +1,201 @@
+import { describe, expect, it } from 'vitest'
+import { readClaudeSubagentTaskFrame } from './claude-subagent-task-frames'
+
+function system(subtype: string, fields: Record<string, unknown>): Record<string, unknown> {
+  return { type: 'system', subtype, session_id: 'claude-session', ...fields }
+}
+
+describe('readClaudeSubagentTaskFrame', () => {
+  it('ignores frames that are not task frames', () => {
+    expect(readClaudeSubagentTaskFrame({ type: 'assistant', subtype: 'task_started' })).toBeNull()
+    expect(readClaudeSubagentTaskFrame(system('init', { task_id: 'task-1' }))).toBeNull()
+    expect(readClaudeSubagentTaskFrame(system('task_started', {}))).toBeNull()
+    expect(readClaudeSubagentTaskFrame(system('task_started', { task_id: '' }))).toBeNull()
+  })
+
+  describe('task_type triage', () => {
+    it('announces a local_agent task', () => {
+      const frame = readClaudeSubagentTaskFrame(
+        system('task_started', {
+          task_id: 'task-1',
+          tool_use_id: 'toolu_1',
+          task_type: 'local_agent',
+          subagent_type: 'code-reviewer',
+          description: 'Review the diff'
+        })
+      )
+      expect(frame).toMatchObject({
+        taskId: 'task-1',
+        toolUseId: 'toolu_1',
+        label: 'Review the diff',
+        announcesSubagent: true,
+        excluded: false
+      })
+    })
+
+    it('excludes a backgrounded shell command even though it carries a tool_use_id', () => {
+      const frame = readClaudeSubagentTaskFrame(
+        system('task_started', {
+          task_id: 'task-bash',
+          tool_use_id: 'toolu_bash',
+          task_type: 'local_bash',
+          description: 'sleep 20',
+          is_backgrounded: true
+        })
+      )
+      expect(frame).toMatchObject({
+        taskId: 'task-bash',
+        toolUseId: 'toolu_bash',
+        announcesSubagent: false,
+        excluded: true
+      })
+    })
+
+    it('excludes workflows and monitors', () => {
+      for (const taskType of ['local_workflow', 'monitor']) {
+        expect(
+          readClaudeSubagentTaskFrame(
+            system('task_started', { task_id: `task-${taskType}`, task_type: taskType })
+          )
+        ).toMatchObject({ announcesSubagent: false, excluded: true })
+      }
+    })
+
+    it('caps a subagent_type label the way a description is capped', () => {
+      const frame = readClaudeSubagentTaskFrame(
+        system('task_started', { task_id: 'task-1', subagent_type: 'a'.repeat(900) })
+      )
+      // The roster stores this label verbatim, so nothing downstream bounds it.
+      expect(frame?.label).toHaveLength(512)
+    })
+
+    it('falls back to subagent_type only when the release sends no task_type', () => {
+      expect(
+        readClaudeSubagentTaskFrame(
+          system('task_started', { task_id: 'task-old', subagent_type: 'explorer' })
+        )
+      ).toMatchObject({ announcesSubagent: true, label: 'explorer' })
+      expect(
+        readClaudeSubagentTaskFrame(system('task_started', { task_id: 'task-bare' }))
+      ).toMatchObject({ announcesSubagent: false, excluded: true })
+      // A type this build does not recognise is not an agent on subagent_type's word.
+      expect(
+        readClaudeSubagentTaskFrame(
+          system('task_started', {
+            task_id: 'task-new',
+            task_type: 'local_something_new',
+            subagent_type: 'explorer'
+          })
+        )
+      ).toMatchObject({ announcesSubagent: false, excluded: true })
+    })
+
+    it('excludes ambient housekeeping tasks', () => {
+      for (const suppression of [{ skip_transcript: true }, { ambient: true }]) {
+        expect(
+          readClaudeSubagentTaskFrame(
+            system('task_started', {
+              task_id: 'task-ambient',
+              task_type: 'local_agent',
+              subagent_type: 'watcher',
+              ...suppression
+            })
+          )
+        ).toMatchObject({ announcesSubagent: false, excluded: true })
+      }
+    })
+  })
+
+  describe('status', () => {
+    it('collapses every in-flight status to working', () => {
+      for (const status of ['pending', 'running', 'paused']) {
+        expect(
+          readClaudeSubagentTaskFrame(
+            system('task_updated', { task_id: 'task-1', patch: { status } })
+          )
+        ).toMatchObject({ state: 'working' })
+      }
+    })
+
+    it('maps the settled statuses onto the carrier vocabulary', () => {
+      const mapped: [string, string][] = [
+        ['completed', 'completed'],
+        ['failed', 'failed'],
+        ['killed', 'stopped'],
+        ['stopped', 'stopped']
+      ]
+      for (const [status, state] of mapped) {
+        expect(
+          readClaudeSubagentTaskFrame(
+            system('task_updated', { task_id: 'task-1', patch: { status } })
+          )
+        ).toMatchObject({ state })
+      }
+    })
+
+    it('reports no state for a status it cannot map', () => {
+      for (const status of ['__proto__', 'toString', 'invented', 7, null]) {
+        expect(
+          readClaudeSubagentTaskFrame(
+            system('task_updated', { task_id: 'task-1', patch: { status } })
+          )
+        ).toMatchObject({ state: null })
+      }
+    })
+
+    it('treats progress as no lifecycle verdict', () => {
+      for (const subtype of ['task_progress']) {
+        expect(
+          readClaudeSubagentTaskFrame(
+            system(subtype, { task_id: 'task-1', status: 'completed', patch: { status: 'failed' } })
+          )
+        ).toMatchObject({ state: null })
+      }
+    })
+  })
+
+  it('reads the notification verdict from its top-level status', () => {
+    for (const state of ['completed', 'failed', 'stopped']) {
+      expect(
+        readClaudeSubagentTaskFrame(
+          system('task_notification', {
+            task_id: 'task-1',
+            status: state,
+            patch: { status: 'running' }
+          })
+        )
+      ).toMatchObject({ state })
+    }
+  })
+
+  it('reads the backgrounded flag from the frame or its patch', () => {
+    expect(
+      readClaudeSubagentTaskFrame(
+        system('task_started', {
+          task_id: 'task-1',
+          task_type: 'local_agent',
+          is_backgrounded: true
+        })
+      )
+    ).toMatchObject({ backgrounded: true })
+    expect(
+      readClaudeSubagentTaskFrame(
+        system('task_updated', { task_id: 'task-1', patch: { is_backgrounded: true } })
+      )
+    ).toMatchObject({ backgrounded: true })
+    expect(
+      readClaudeSubagentTaskFrame(system('task_updated', { task_id: 'task-1', patch: {} }))
+    ).toMatchObject({ backgrounded: null })
+  })
+
+  it('collapses a multi-line description into one bounded label', () => {
+    expect(
+      readClaudeSubagentTaskFrame(
+        system('task_updated', {
+          task_id: 'task-1',
+          patch: { description: '  audit\n  the   lockfile  ' }
+        })
+      )
+    ).toMatchObject({ label: 'audit the lockfile' })
+  })
+})
diff --git a/src/main/claude/claude-subagent-task-frames.ts b/src/main/claude/claude-subagent-task-frames.ts
new file mode 100644
index 00000000000..e5f361fa8c4
--- /dev/null
+++ b/src/main/claude/claude-subagent-task-frames.ts
@@ -0,0 +1,123 @@
+// Claude's declarative task protocol, read as subagent roster events.
+//
+// `local_agent`, `local_workflow` and `local_bash` tasks all arrive on the same
+// `message:system:task_*` channel and ALL carry a `tool_use_id`, so id presence
+// discriminates nothing: filtering on it alone puts a backgrounded `sleep 20` in
+// the subagent roster. `task_type` is the discriminator, with `subagent_type`
+// covering CLI releases that predate it.
+
+import type { NativeChatSubagentState } from '../../shared/native-chat-types'
+import {
+  classifyClaudeBackgroundTaskKind,
+  claudeTaskDescription,
+  claudeTaskId,
+  isBoundedClaudeTaskId
+} from './claude-background-task-tracker'
+import { claudeRecord, claudeText } from './claude-structured-item-translation'
+
+const TASK_SUBTYPES: ReadonlySet<string> = new Set([
+  'task_started',
+  'task_updated',
+  'task_progress',
+  'task_notification'
+])
+
+/** Provider status → the carrier's vocabulary. `killed` and `stopped` both mean
+ *  the task was deliberately ended, which the carrier calls `stopped`; every
+ *  in-flight status collapses to `working`. A Map, not an object, so a payload
+ *  carrying `__proto__` as its status cannot resolve to an inherited value. */
+const TASK_STATES: ReadonlyMap<string, NativeChatSubagentState> = new Map([
+  ['pending', 'working'],
+  ['running', 'working'],
+  ['paused', 'working'],
+  ['completed', 'completed'],
+  ['failed', 'failed'],
+  ['killed', 'stopped'],
+  ['stopped', 'stopped']
+] satisfies [string, NativeChatSubagentState][])
+
+export type ClaudeSubagentTaskFrame = {
+  /** Canonical, resume-stable id — the roster key. */
+  taskId: string
+  /** Re-minted when Claude re-announces a resumed task, so it is only an alias. */
+  toolUseId: string | null
+  label: string | null
+  /** null when the frame reported no lifecycle status. */
+  state: NativeChatSubagentState | null
+  backgrounded: boolean | null
+  /** Any `task_started`, subagent or not. Proof this CLI declares its tasks. */
+  announcement: boolean
+  /** `task_started` for a task the roster should show. Only an announcement
+   *  creates an entry: an update carries no `task_type`, so honouring one for an
+   *  unknown id would roster whatever else shares this channel. */
+  announcesSubagent: boolean
+  /** Ambient housekeeping, or a task that is not a subagent at all. Its ids must
+   *  never reach the roster, by this frame or by later child traffic. */
+  excluded: boolean
+}
+
+/** True when the task Claude announced is a subagent rather than a backgrounded
+ *  shell command or a workflow. */
+export function isClaudeSubagentTask(message: Record<string, unknown>): boolean {
+  if (classifyClaudeBackgroundTaskKind(message.task_type) === 'agent') {
+    return true
+  }
+  // Releases predating `task_type` still name the child in `subagent_type`. A
+  // task_type Orca does not recognise is NOT covered: it is a type this build
+  // has no reason to believe is an agent.
+  return (
+    (message.task_type === undefined || message.task_type === null) &&
+    claudeText(message.subagent_type) !== null
+  )
+}
+
+function taskState(value: unknown): NativeChatSubagentState | null {
+  return typeof value === 'string' ? (TASK_STATES.get(value) ?? null) : null
+}
+
+export function readClaudeSubagentTaskFrame(
+  message: Record<string, unknown>
+): ClaudeSubagentTaskFrame | null {
+  if (message.type !== 'system') {
+    return null
+  }
+  const subtype = claudeText(message.subtype)
+  if (!subtype || !TASK_SUBTYPES.has(subtype)) {
+    return null
+  }
+  const taskId = claudeTaskId(message)
+  if (!taskId) {
+    return null
+  }
+  const patch = claudeRecord(message.patch)
+  const toolUseId = claudeText(message.tool_use_id) ?? claudeText(patch?.tool_use_id)
+  const announcement = subtype === 'task_started'
+  // Housekeeping Claude runs for itself; the user never asked for it.
+  const suppressed = message.ambient === true || message.skip_transcript === true
+  const subagent = announcement && !suppressed && isClaudeSubagentTask(message)
+  return {
+    taskId,
+    toolUseId: toolUseId && isBoundedClaudeTaskId(toolUseId) ? toolUseId : null,
+    label:
+      claudeTaskDescription(message.description) ??
+      claudeTaskDescription(patch?.description) ??
+      // Bounded like a description: the roster stores whatever this returns.
+      (announcement ? (claudeTaskDescription(message.subagent_type) ?? null) : null),
+    // Notifications carry terminal evidence; progress carries usage only.
+    state:
+      subtype === 'task_notification'
+        ? taskState(message.status)
+        : announcement || subtype === 'task_updated'
+          ? taskState(patch?.status ?? message.status)
+          : null,
+    backgrounded:
+      typeof patch?.is_backgrounded === 'boolean'
+        ? patch.is_backgrounded
+        : typeof message.is_backgrounded === 'boolean'
+          ? message.is_backgrounded
+          : null,
+    announcement,
+    announcesSubagent: subagent,
+    excluded: announcement && !subagent
+  }
+}
diff --git a/src/main/native-chat/agent-session-journal/journal-legacy-import.test.ts b/src/main/native-chat/agent-session-journal/journal-legacy-import.test.ts
index ed86d81861e..13673626ebc 100644
--- a/src/main/native-chat/agent-session-journal/journal-legacy-import.test.ts
+++ b/src/main/native-chat/agent-session-journal/journal-legacy-import.test.ts
@@ -432,6 +432,86 @@ describe('payload bounds on import', () => {
     expect(body.output.byteLength).toBe(64 * 1024)
     expect(body.output.head).toHaveLength(1_024)
   })
+
+  it('bounds an imported subagent roster by entry count, label and id', async () => {
+    // The import reads an untrusted file: nothing upstream bounded either string.
+    const oversized = 'z'.repeat(20 * 1024)
+    const journal = await open('claude', CLAUDE_SESSION)
+    await appendLegacyTranscriptMessages({
+      journal,
+      agent: 'claude',
+      sessionId: CLAUDE_SESSION,
+      fence: 1,
+      messages: [
+        {
+          id: 'legacy-roster',
+          role: 'assistant',
+          timestamp: null,
+          source: 'transcript',
+          blocks: [
+            {
+              type: 'subagent-group',
+              groupId: 'group-1',
+              agents: Array.from({ length: 80 }, (_, index) => ({
+                id: index === 0 ? oversized : `task-${index}`,
+                label: index === 0 ? oversized : `label-${index}`,
+                state: 'working' as const
+              }))
+            }
+          ]
+        }
+      ]
+    })
+
+    const body = journal.snapshot().items[0]?.body
+    const block = body?.kind === 'message' ? body.blocks[0] : undefined
+    if (block?.type !== 'subagent-group') {
+      throw new Error('expected a subagent-group block')
+    }
+    expect(block.agents).toHaveLength(64)
+    expect(block.agents[0]?.label.length).toBeLessThan(oversized.length)
+    expect(block.agents[0]?.id.length).toBeLessThan(oversized.length)
+    expect(block.agents[0]?.id.startsWith('z')).toBe(true)
+  })
+
+  it('bounds a roster id in the shared format, keeping a shared prefix distinct', async () => {
+    // The id is the roster key: it takes the same bounded-id format the wires
+    // use, so a later wire bound is a no-op instead of a second, merging clip.
+    const head = 'y'.repeat(512)
+    const journal = await open('claude', CLAUDE_SESSION)
+    await appendLegacyTranscriptMessages({
+      journal,
+      agent: 'claude',
+      sessionId: CLAUDE_SESSION,
+      fence: 1,
+      messages: [
+        {
+          id: 'legacy-roster-collision',
+          role: 'assistant',
+          timestamp: null,
+          source: 'transcript',
+          blocks: [
+            {
+              type: 'subagent-group',
+              groupId: 'group-1',
+              agents: [
+                { id: `${head}-one`, label: 'Audit', state: 'working' as const },
+                { id: `${head}-two`, label: 'Audit', state: 'working' as const }
+              ]
+            }
+          ]
+        }
+      ]
+    })
+
+    const body = journal.snapshot().items[0]?.body
+    const block = body?.kind === 'message' ? body.blocks[0] : undefined
+    if (block?.type !== 'subagent-group') {
+      throw new Error('expected a subagent-group block')
+    }
+    expect(block.agents[0]?.id).not.toBe(block.agents[1]?.id)
+    expect(block.agents[0]?.id).toHaveLength(512)
+  })
 })
 
 describe('import failures', () => {
diff --git a/src/main/native-chat/agent-session-journal/journal-legacy-import.ts b/src/main/native-chat/agent-session-journal/journal-legacy-import.ts
index 0907ebd28f2..801c91fb534 100644
--- a/src/main/native-chat/agent-session-journal/journal-legacy-import.ts
+++ b/src/main/native-chat/agent-session-journal/journal-legacy-import.ts
@@ -28,6 +28,7 @@ import {
   decodeOmpTranscriptLine
 } from '../transcript-line-decoders'
 import { decodeTranscriptStream } from '../transcript-stream-lines'
+import { boundSubagentEntryId } from '../subagent-entry-id-bounds'
 import { createLegacyIdentityTracker } from './journal-legacy-identity'
 import type { JournalReplacementItem } from './journal-epoch-replacement'
 import {
@@ -47,6 +48,8 @@ export type LegacyImportOptions = ResolveSessionFileOptions & {
 }
 
 const MAX_LEGACY_IMPORT_SOURCE_BYTES = 16 * 1024 * 1024
+/** A roster is a status list; an imported one is as untrusted as any other block. */
+const MAX_LEGACY_IMPORT_SUBAGENTS = 64
 
 export type LegacyImportResult =
   | {
@@ -271,5 +274,17 @@ function boundBlock(block: NativeChatBlock, limits: JournalPayloadLimits): Nativ
   if (block.type === 'tool-call') {
     return { ...block, input: boundToolInput(block.input, limits) }
   }
+  if (block.type === 'subagent-group') {
+    return {
+      ...block,
+      agents: block.agents.slice(0, MAX_LEGACY_IMPORT_SUBAGENTS).map((agent) => ({
+        ...agent,
+        // The id is the roster key, so it is bounded with a digest rather than
+        // clipped to a prefix that two distinct children could share.
+        id: boundSubagentEntryId(agent.id),
+        label: boundInlineText(agent.label, limits).text
+      }))
+    }
+  }
   return block
 }
diff --git a/src/main/native-chat/agent-session-journal/journal-reducer.test.ts b/src/main/native-chat/agent-session-journal/journal-reducer.test.ts
index 2dc0ac1aeb2..255e4ed184c 100644
--- a/src/main/native-chat/agent-session-journal/journal-reducer.test.ts
+++ b/src/main/native-chat/agent-session-journal/journal-reducer.test.ts
@@ -5,7 +5,10 @@ import {
   boundJournalKeyComponent,
   MAX_JOURNAL_KEY_COMPONENT_CHARS
 } from '../../../shared/agent-session-journal-item-key'
-import type { AgentJournalMessageItem } from '../../../shared/agent-session-journal-types'
+import type {
+  AgentJournalItemIdentity,
+  AgentJournalMessageItem
+} from '../../../shared/agent-session-journal-types'
 import { structuredAgentSessionPayloadFingerprint } from '../../../shared/structured-agent-session-mutation'
 import {
   applyJournalRow,
@@ -14,6 +17,7 @@ import {
   renderJournalState,
   type JournalReducerState
 } from './journal-reducer'
+import { buildJournalItemRow, buildJournalTombstoneRow } from './journal-row-builders'
 import type { JournalRow } from './journal-row-schema'
 
 const EPOCH = 'epoch-1'
@@ -444,3 +448,49 @@ describe('bounded item-key collisions', () => {
     ])
   })
 })
+
+describe('re-adding a tombstoned row', () => {
+  it('builds the rebuilt row above the tombstone that removed it', () => {
+    const identity: AgentJournalItemIdentity = { provider: 'orca', clientMessageId: 'roster' }
+    const itemId = agentJournalItemKey(identity)
+    const state = createJournalReducerState('session-1', EPOCH)
+    applyJournalRow(
+      state,
+      buildJournalItemRow({ state, identity, body: text('first'), seq: 1, fence: 1, ts: 1_001 })
+    )
+    applyJournalRow(state, buildJournalTombstoneRow({ state, itemId, seq: 2, fence: 1, ts: 1_002 }))
+    expect(renderJournalState(state).items).toEqual([])
+
+    // Same identity, re-added later in the session: a revision built only from
+    // `items` would restart at 1 and lose to the tombstone forever.
+    applyJournalRow(
+      state,
+      buildJournalItemRow({ state, identity, body: text('second'), seq: 3, fence: 1, ts: 1_003 })
+    )
+    expect(renderJournalState(state).items.map((item) => item.body)).toEqual([text('second')])
+  })
+
+  // `upsertItem` clearing the tombstone on a re-add is a map-state invariant:
+  // `items` and `tombstones` stay disjoint, so a re-added row is never both
+  // present and removed. Revision ordering is now independent of it —
+  // `buildJournalTombstoneRow` takes `max(itemRevision, tombstoneRevision) + 1`
+  // — so what this pins is the map state itself, not the ranking.
+  it('removes the row again after it was re-added', () => {
+    const identity: AgentJournalItemIdentity = { provider: 'orca', clientMessageId: 'roster' }
+    const itemId = agentJournalItemKey(identity)
+    const state = createJournalReducerState('session-1', EPOCH)
+    applyJournalRow(
+      state,
+      buildJournalItemRow({ state, identity, body: text('first'), seq: 1, fence: 1, ts: 1_001 })
+    )
+    applyJournalRow(state, buildJournalTombstoneRow({ state, itemId, seq: 2, fence: 1, ts: 1_002 }))
+    applyJournalRow(
+      state,
+      buildJournalItemRow({ state, identity, body: text('second'), seq: 3, fence: 1, ts: 1_003 })
+    )
+    expect(state.tombstones.get(itemId)).toBeUndefined()
+
+    applyJournalRow(state, buildJournalTombstoneRow({ state, itemId, seq: 4, fence: 1, ts: 1_004 }))
+    expect(renderJournalState(state).items).toEqual([])
+  })
+})
diff --git a/src/main/native-chat/agent-session-journal/journal-row-builders.ts b/src/main/native-chat/agent-session-journal/journal-row-builders.ts
index 5c77c180c68..db82e86318f 100644
--- a/src/main/native-chat/agent-session-journal/journal-row-builders.ts
+++ b/src/main/native-chat/agent-session-journal/journal-row-builders.ts
@@ -148,7 +148,13 @@ export function buildJournalItemRow(input: {
 }): JournalItemRow {
   const itemId = agentJournalItemKey(input.identity)
   const resolved = input.state.aliases.get(itemId) ?? itemId
-  const revision = (input.state.items.get(resolved)?.revision ?? 0) + 1
+  // A tombstoned row keeps its revision in `tombstones`, and the reducer drops
+  // any item at or below it — so a re-add has to outrank the tombstone too.
+  const revision =
+    Math.max(
+      input.state.items.get(resolved)?.revision ?? 0,
+      input.state.tombstones.get(resolved) ?? 0
+    ) + 1
   return {
     kind: 'item',
     itemId,
@@ -170,7 +176,15 @@ export function buildJournalTombstoneRow(input: {
   return {
     kind: 'tombstone',
     itemId: input.itemId,
-    revision: (input.state.items.get(resolved)?.revision ?? 0) + 1,
+    // Symmetric with the item builder: `upsertItem` clearing the tombstone on a
+    // re-add is what keeps the two maps disjoint, and that invariant lives in the
+    // reducer. Outranking both here means a repeat removal cannot be dropped as a
+    // stale revision if it ever stops holding.
+    revision:
+      Math.max(
+        input.state.items.get(resolved)?.revision ?? 0,
+        input.state.tombstones.get(resolved) ?? 0
+      ) + 1,
     ...journalRowBase(input.state.epoch, input.seq, input.fence, input.ts)
   }
 }
diff --git a/src/main/native-chat/subagent-entry-id-bounds.test.ts b/src/main/native-chat/subagent-entry-id-bounds.test.ts
new file mode 100644
index 00000000000..56d0edece66
--- /dev/null
+++ b/src/main/native-chat/subagent-entry-id-bounds.test.ts
@@ -0,0 +1,26 @@
+import { describe, expect, it } from 'vitest'
+import { boundSubagentEntryId, MAX_SUBAGENT_ENTRY_ID_CHARS } from './subagent-entry-id-bounds'
+
+const SHARED_HEAD = 'a'.repeat(MAX_SUBAGENT_ENTRY_ID_CHARS)
+
+describe('boundSubagentEntryId', () => {
+  it('leaves an id that already fits untouched', () => {
+    const id = 'task-1'
+    expect(boundSubagentEntryId(id)).toBe(id)
+    expect(boundSubagentEntryId(SHARED_HEAD)).toBe(SHARED_HEAD)
+  })
+
+  it('keeps two ids sharing the whole cap-length head distinct', () => {
+    const first = boundSubagentEntryId(`${SHARED_HEAD}-one`)
+    const second = boundSubagentEntryId(`${SHARED_HEAD}-two`)
+    expect(first).not.toBe(second)
+    expect(first).toHaveLength(MAX_SUBAGENT_ENTRY_ID_CHARS)
+    expect(second).toHaveLength(MAX_SUBAGENT_ENTRY_ID_CHARS)
+  })
+
+  it('is deterministic and a no-op on an already bounded id', () => {
+    const bounded = boundSubagentEntryId(`${SHARED_HEAD}-one`)
+    expect(boundSubagentEntryId(`${SHARED_HEAD}-one`)).toBe(bounded)
+    expect(boundSubagentEntryId(bounded)).toBe(bounded)
+  })
+})
diff --git a/src/main/native-chat/subagent-entry-id-bounds.ts b/src/main/native-chat/subagent-entry-id-bounds.ts
new file mode 100644
index 00000000000..3abf19a4ff6
--- /dev/null
+++ b/src/main/native-chat/subagent-entry-id-bounds.ts
@@ -0,0 +1,27 @@
+// Bounding a subagent entry's id — a KEY, not display text.
+//
+// `NativeChatSubagentEntry.id` keys the roster, so clipping it to a fixed prefix
+// merges two distinct children whose ids agree that far and associates one's
+// state with the other. An id long enough to need bounding only reaches us from
+// an imported legacy transcript, but a bound is still required, so keep a head
+// for readability plus a digest of the WHOLE id to keep distinct ids distinct.
+
+import { createHash } from 'node:crypto'
+
+/** Shared by every site that puts a roster entry on a wire, so a journal-bound
+ *  id survives the RPC and transcript bounds untouched instead of being clipped
+ *  a second time into a different string. */
+export const MAX_SUBAGENT_ENTRY_ID_CHARS = 512
+
+const DIGEST_CHARS = 16
+
+/** Returns `id` unchanged when it fits, else a head plus a digest suffix whose
+ *  total length is exactly the cap — so bounding a bounded id is a no-op. */
+export function boundSubagentEntryId(id: string): string {
+  if (id.length <= MAX_SUBAGENT_ENTRY_ID_CHARS) {
+    return id
+  }
+  const digest = createHash('sha256').update(id, 'utf8').digest('base64url').slice(0, DIGEST_CHARS)
+  const suffix = `…#${digest}`
+  return `${id.slice(0, MAX_SUBAGENT_ENTRY_ID_CHARS - suffix.length)}${suffix}`
+}
diff --git a/src/main/runtime/orchestration/worker-transcript-payload.test.ts b/src/main/runtime/orchestration/worker-transcript-payload.test.ts
index f47a46605e1..aaa3fdcfcc1 100644
--- a/src/main/runtime/orchestration/worker-transcript-payload.test.ts
+++ b/src/main/runtime/orchestration/worker-transcript-payload.test.ts
@@ -146,6 +146,36 @@ describe('worker transcript wire bounds', () => {
     expect(result).toMatchObject({ limited: false, warnings: [] })
   })
 
+  it('keeps two roster ids sharing a 512-char prefix distinct', () => {
+    // The id is the roster key: a plain prefix clip would merge the two children.
+    const head = 'a'.repeat(512)
+    const result = boundWorkerTranscriptMessages([
+      {
+        id: 'message-1',
+        role: 'assistant',
+        timestamp: null,
+        source: 'transcript',
+        blocks: [
+          {
+            type: 'subagent-group',
+            groupId: 'g',
+            agents: [
+              { id: `${head}-one`, label: 'Audit', state: 'working' },
+              { id: `${head}-two`, label: 'Audit', state: 'working' }
+            ]
+          }
+        ]
+      }
+    ])
+
+    const block = result.messages[0]?.blocks[0]
+    if (block?.type !== 'subagent-group') {
+      throw new Error('expected a subagent-group block')
+    }
+    expect(block.agents[0]?.id).not.toBe(block.agents[1]?.id)
+    expect(block.agents[0]?.id).toHaveLength(512)
+  })
+
   it('keeps fallback identifiers stable without exposing the transcript path', () => {
     const transcriptPath = 'C:\\Users\\worker\\.codex\\session.jsonl'
     const message = {
diff --git a/src/main/runtime/orchestration/worker-transcript-payload.ts b/src/main/runtime/orchestration/worker-transcript-payload.ts
index f9d83e20c62..0f50aa8309c 100644
--- a/src/main/runtime/orchestration/worker-transcript-payload.ts
+++ b/src/main/runtime/orchestration/worker-transcript-payload.ts
@@ -5,6 +5,7 @@ import type {
   NativeChatMessage,
   NativeChatSubagentState
 } from '../../../shared/native-chat-types'
+import { boundSubagentEntryId } from '../../native-chat/subagent-entry-id-bounds'
 
 export const DEFAULT_WORKER_TRANSCRIPT_MESSAGE_LIMIT = 40
 export const MAX_WORKER_TRANSCRIPT_MESSAGE_LIMIT = 50
@@ -153,7 +154,7 @@ function boundBlock(block: NativeChatBlock, state: TranscriptBoundState): Native
       groupId: clipMetadata(block.groupId, state),
       agents: agents.map((agent) => ({
         ...agent,
-        id: clipMetadata(agent.id, state),
+        id: boundEntryId(agent.id, state),
         label: clipMetadata(agent.label, state),
         state: clipSubagentState(agent.state, state)
       }))
@@ -194,6 +195,18 @@ function isLocalFileLocator(value: string): boolean {
   )
 }
 
+/** A roster entry's id is the roster KEY, so it is redacted like other metadata
+ *  but bounded with a digest rather than clipped: two ids sharing a 512-char
+ *  head must not collapse onto one entry. */
+function boundEntryId(value: string, state: TranscriptBoundState): string {
+  const redacted = redactSensitiveText(value, state.warnings)
+  const bounded = boundSubagentEntryId(redacted)
+  if (bounded !== redacted) {
+    markClipped(state, 'Oversized transcript metadata was clipped.')
+  }
+  return bounded
+}
+
 function clipMetadata(value: string, state: TranscriptBoundState): string {
   const redacted = redactSensitiveText(value, state.warnings)
   if (redacted.length <= MAX_WORKER_TRANSCRIPT_METADATA_CHARS) {
diff --git a/src/main/runtime/rpc/methods/native-chat-rpc-block-sanitize.test.ts b/src/main/runtime/rpc/methods/native-chat-rpc-block-sanitize.test.ts
new file mode 100644
index 00000000000..de25ea7e45d
--- /dev/null
+++ b/src/main/runtime/rpc/methods/native-chat-rpc-block-sanitize.test.ts
@@ -0,0 +1,35 @@
+import { describe, expect, it } from 'vitest'
+import type { NativeChatBlock } from '../../../../shared/native-chat-types'
+import { sanitizeNativeChatRpcBlock } from './native-chat-rpc-block-sanitize'
+
+const SHARED_HEAD = 'a'.repeat(512)
+
+function rosterBlock(ids: readonly string[]): NativeChatBlock {
+  return {
+    type: 'subagent-group',
+    groupId: 'group-1',
+    agents: ids.map((id) => ({ id, label: 'l'.repeat(900), state: 'working' as const }))
+  }
+}
+
+describe('mobile subagent roster bounds', () => {
+  it('keeps two ids sharing a 512-char prefix distinct', () => {
+    const block = sanitizeNativeChatRpcBlock(
+      rosterBlock([`${SHARED_HEAD}-one`, `${SHARED_HEAD}-two`]),
+      'mobile'
+    )
+
+    if (block.type !== 'subagent-group') {
+      throw new Error('expected a subagent-group block')
+    }
+    expect(block.agents[0]?.id).not.toBe(block.agents[1]?.id)
+    expect(block.agents[0]?.id).toHaveLength(512)
+    // The label is display text and still clips.
+    expect(block.agents[0]?.label).toContain('… (truncated)')
+  })
+
+  it('leaves a short id alone', () => {
+    const block = sanitizeNativeChatRpcBlock(rosterBlock(['task-1']), 'mobile')
+    expect(block.type === 'subagent-group' && block.agents[0]?.id).toBe('task-1')
+  })
+})
diff --git a/src/main/runtime/rpc/methods/native-chat-rpc-block-sanitize.ts b/src/main/runtime/rpc/methods/native-chat-rpc-block-sanitize.ts
index fc19273d5ca..79f1da4fc53 100644
--- a/src/main/runtime/rpc/methods/native-chat-rpc-block-sanitize.ts
+++ b/src/main/runtime/rpc/methods/native-chat-rpc-block-sanitize.ts
@@ -3,6 +3,7 @@ import {
   normalizeSubagentState
 } from '../../../../shared/native-chat-subagent-summary'
 import type { NativeChatBlock, NativeChatSubagentState } from '../../../../shared/native-chat-types'
+import { boundSubagentEntryId } from '../../../native-chat/subagent-entry-id-bounds'
 import type { RpcContext } from '../core'
 import { sanitizeNativeChatRpcImageBlock } from './native-chat-rpc-image-block'
 
@@ -63,7 +64,9 @@ export function sanitizeNativeChatRpcBlock(
       groupId: clip(block.groupId, MAX_SUBAGENT_FIELD_CHARS),
       agents: block.agents.slice(0, MOBILE_SUBAGENT_CAP).map((agent) => ({
         ...agent,
-        id: clip(agent.id, MAX_SUBAGENT_FIELD_CHARS),
+        // The id is the roster KEY: a prefix clip would merge two children, so
+        // it takes the shared digest bound the other wires use.
+        id: boundSubagentEntryId(agent.id),
         label: clip(agent.label, MAX_SUBAGENT_FIELD_CHARS),
         state: clipSubagentState(agent.state)
       }))
diff --git a/src/main/runtime/rpc/methods/native-chat.test.ts b/src/main/runtime/rpc/methods/native-chat.test.ts
index 1417e716770..47a6d9e855e 100644
--- a/src/main/runtime/rpc/methods/native-chat.test.ts
+++ b/src/main/runtime/rpc/methods/native-chat.test.ts
@@ -1,5 +1,8 @@
 import { describe, expect, it, vi } from 'vitest'
-import type { NativeChatMessage } from '../../../../shared/native-chat-types'
+import type {
+  NativeChatMessage,
+  NativeChatSubagentEntry
+} from '../../../../shared/native-chat-types'
 import type { RpcContext } from '../core'
 
 // Stub the bounded tail reader so the handler returns a deterministic transcript with
@@ -88,6 +91,7 @@ vi.mock('../../../native-chat/transcript-watch', () => ({
   }
 }))
 
+import { boundSubagentEntryId } from '../../../native-chat/subagent-entry-id-bounds'
 import { NATIVE_CHAT_METHODS } from './native-chat'
 
 function makeMessage(text: string): NativeChatMessage {
@@ -191,6 +195,35 @@ describe('nativeChat.readSession clientKind truncation gating', () => {
     expect(block.text).toBe(text)
   })
 
+  it('bounds a subagent roster before it reaches mobile', async () => {
+    const agents: NativeChatSubagentEntry[] = Array.from({ length: 100 }, (_, index) => ({
+      id: `task-${index}-${'i'.repeat(600)}`,
+      label: 'l'.repeat(600),
+      state: 'working'
+    }))
+    cachedResult.value = {
+      messages: [
+        {
+          ...makeMessage(''),
+          blocks: [{ type: 'subagent-group', groupId: 'g', agents }]
+        }
+      ]
+    }
+    const result = await readSessionHandler()(
+      { agent: 'claude', sessionId: 's' },
+      ctxWith('mobile')
+    )
+    const block = (result as { messages: NativeChatMessage[] }).messages[0].blocks[0] as {
+      agents: { id: string; label: string }[]
+    }
+    expect(block.agents).toHaveLength(64)
+    expect(block.agents[0].label).toBe(`${'l'.repeat(512)}\n… (truncated)`)
+    // The id is as untrusted as the label on an imported roster, but it is the
+    // roster key: it is bounded with a digest, never clipped to a bare prefix.
+    expect(block.agents[0].id).toHaveLength(512)
+    expect(block.agents[0].id).toBe(boundSubagentEntryId(`task-0-${'i'.repeat(600)}`))
+  })
+
   it('clips a pathological text block at the safety ceiling for mobile clients', async () => {
     const text = 'y'.repeat(70_000)
     cachedResult.value = { messages: [makeTextMessage(text)] }
diff --git a/src/shared/agent-session-journal-schemas.test.ts b/src/shared/agent-session-journal-schemas.test.ts
index ac7dafacfd2..93b2b460bb0 100644
--- a/src/shared/agent-session-journal-schemas.test.ts
+++ b/src/shared/agent-session-journal-schemas.test.ts
@@ -33,7 +33,15 @@ const CANONICAL_BODIES: AgentJournalItemBody[] = [
       },
       { type: 'tool-call', name: 'Read', input: { path: 'a' } },
       { type: 'tool-result', output: 'ok', isError: false },
-      { type: 'image-ref', path: '/tmp/a.png', alt: 'screenshot' }
+      { type: 'image-ref', path: '/tmp/a.png', alt: 'screenshot' },
+      {
+        type: 'subagent-group',
+        groupId: 'claude-session:turn-1',
+        agents: [
+          { id: 'task-1', label: 'Explore', state: 'working', startedAt: 1_000 },
+          { id: 'task-2', label: 'Review', state: 'completed', tokens: 42, settledAt: 2_000 }
+        ]
+      }
     ]
   },
   { kind: 'tool-call', name: 'Read', input: undefined, state: 'running' },
@@ -143,6 +151,41 @@ describe('nested corruption is rejected', () => {
     ).toBe(false)
   })
 
+  it('rejects a subagent roster whose entries are malformed', () => {
+    // A KNOWN block type stays a known block: it must not fall through to the
+    // forward-tolerant arm just because its payload is wrong.
+    expect(
+      isAdmissibleAgentJournalItemBody({
+        kind: 'message',
+        role: 'system',
+        blocks: [{ type: 'subagent-group', groupId: 'g', agents: [{ id: 'a', label: 'x' }] }]
+      })
+    ).toBe(false)
+    expect(
+      isAdmissibleAgentJournalItemBody({
+        kind: 'message',
+        role: 'system',
+        blocks: [{ type: 'subagent-group', groupId: 'g', agents: 'not-a-roster' }]
+      })
+    ).toBe(false)
+  })
+
+  it('keeps a state string a newer build might write admissible', () => {
+    expect(
+      isAdmissibleAgentJournalItemBody({
+        kind: 'message',
+        role: 'system',
+        blocks: [
+          {
+            type: 'subagent-group',
+            groupId: 'g',
+            agents: [{ id: 'a', label: 'x', state: 'some-future-state' }]
+          }
+        ]
+      })
+    ).toBe(true)
+  })
+
   it('rejects shallow render items and submissions', () => {
     expect(
       isAdmissibleAgentJournalRenderItem({