diff --git a/config/scripts/vitest-sqlite-runtime-files.mjs b/config/scripts/vitest-sqlite-runtime-files.mjs
index 3d224533442..17d1522c97b 100644
--- a/config/scripts/vitest-sqlite-runtime-files.mjs
+++ b/config/scripts/vitest-sqlite-runtime-files.mjs
@@ -45,6 +45,7 @@ export const SQLITE_RUNTIME_INCLUDE = [
   'src/main/claude/claude-subagent-permission-request.test.ts',
   'src/main/claude/claude-subagent-resume-after-restart.test.ts',
   'src/main/codex/codex-provider-retry-idle-sweep.test.ts',
+  'src/main/codex/codex-subagent-roster-retention.test.ts',
   'src/main/codex/codex-structured-journal-exit-convergence.test.ts',
   'src/main/codex/codex-structured-journal-goal-revision.test.ts',
   'src/main/codex/codex-structured-journal-repeated-questions.test.ts',
diff --git a/src/main/acp/acp-subagent-timeline.test.ts b/src/main/acp/acp-subagent-timeline.test.ts
index 9a8a831cbe9..a3848842816 100644
--- a/src/main/acp/acp-subagent-timeline.test.ts
+++ b/src/main/acp/acp-subagent-timeline.test.ts
@@ -16,7 +16,7 @@ const retainedSchema = z.object({
     })
   ),
   groupOf: z.map(z.string(), z.string()),
-  settledIds: z.object({ size: z.number() })
+  retention: z.object({ settledIdentities: z.object({ size: z.number() }) })
 })
 
 function spawnGroups(
@@ -99,7 +99,7 @@ describe('ACP subagent retention', () => {
     expect(
       [...retained.groups.values()].reduce((total, group) => total + group.results.size, 0)
     ).toBe(31 * 64)
-    expect(retained.settledIds.size).toBe(32 * 64)
+    expect(retained.retention.settledIdentities.size).toBe(32 * 64)
     expect(timeline.has('live')).toBe(true)
     expect(timeline.has('0:0')).toBe(false)
     expect(timeline.has('33:0')).toBe(true)
@@ -149,7 +149,7 @@ describe('ACP subagent retention', () => {
     const retained = retainedSchema.parse(timeline)
     expect(retained.groups.size).toBe(0)
     expect(retained.groupOf.size).toBe(0)
-    expect(retained.settledIds.size).toBe(0)
+    expect(retained.retention.settledIdentities.size).toBe(0)
     expect(timeline.translate([{ id: 'child-1', tokens: 9 }, { id: 'new' }], {}, 101)).toEqual([])
     expect(retainedSchema.parse(timeline).groups.size).toBe(0)
   })
diff --git a/src/main/acp/acp-subagent-timeline.ts b/src/main/acp/acp-subagent-timeline.ts
index 60eed96d175..532f782210c 100644
--- a/src/main/acp/acp-subagent-timeline.ts
+++ b/src/main/acp/acp-subagent-timeline.ts
@@ -1,4 +1,3 @@
-import { BoundedMap } from '../../shared/bounded-map'
 import {
   canReplaceSubagentState,
   isTerminalSubagentState
@@ -15,6 +14,7 @@ import {
 import type { ProviderTimelineJoin } from '../native-chat/agent-session-timeline/provider-timeline-event'
 import { acpSubagentIdentity, type AcpTimelineEvent } from './acp-timeline-event'
 import type { AcpSubagentUpdate } from './acp-dialects/acp-dialect'
+import { SubagentRosterRetention } from '../native-chat/subagent-roster-retention'
 
 /** Settled history budget; live ownership outlives it until an outcome or session close. */
 const MAX_GROUPS = 32
@@ -36,16 +36,22 @@ type RosterGroup = {
 export class AcpSubagentTimeline {
   private readonly groups = new Map<string, RosterGroup>()
   private readonly groupOf = new Map<string, string>()
-  /** An eviction index, re-derived from the changed groups' entries after each batch. */
-  private readonly settledGroups = new Set<string>()
-  private readonly settledIds = new BoundedMap<string, true>({
-    maxEntries: MAX_GROUPS * MAX_SUBAGENTS_PER_GROUP
+  private readonly retention = new SubagentRosterRetention(this.groups, {
+    maxGroups: MAX_GROUPS,
+    maxSettledIdentities: MAX_GROUPS * MAX_SUBAGENTS_PER_GROUP,
+    entries: (group) => group.entries.values(),
+    identities: (group) => group.entries.keys(),
+    onEvict: (group) => {
+      for (const id of group.entries.keys()) {
+        this.groupOf.delete(id)
+      }
+    }
   })
   private disposed = false
 
   /** Known children include recently evicted outcomes, so they cannot become background tasks. */
   has(id: string): boolean {
-    return this.groupOf.has(id) || this.settledIds.has(id)
+    return this.groupOf.has(id) || this.retention.hasSettled(id)
   }
 
   /** The journal owns session-end settlement; no later frame may reacquire working ownership. */
@@ -53,8 +59,7 @@ export class AcpSubagentTimeline {
     this.disposed = true
     this.groups.clear()
     this.groupOf.clear()
-    this.settledGroups.clear()
-    this.settledIds.clear()
+    this.retention.clear()
   }
 
   translate(
@@ -93,7 +98,8 @@ export class AcpSubagentTimeline {
         join: groupJoin(group, join)
       })
     }
-    this.trimSettledGroups(changed)
+    // Emit the final roster and reply before releasing their cached ownership together.
+    this.retention.trim(changed)
     return events
   }
 
@@ -102,7 +108,7 @@ export class AcpSubagentTimeline {
     join: ProviderTimelineJoin,
     at: number
   ): RosterGroup | undefined {
-    if (this.settledIds.has(update.id)) {
+    if (this.retention.hasSettled(update.id)) {
       return undefined
     }
     const known = this.groups.get(this.groupOf.get(update.id) ?? '')
@@ -169,31 +175,6 @@ export class AcpSubagentTimeline {
     return boundSubagentField(seen === 0 ? bounded : `${bounded} ${seen + 1}`, index)
   }
 
-  private trimSettledGroups(changed: Set<RosterGroup>): void {
-    for (const group of changed) {
-      if ([...group.entries.values()].every((entry) => isTerminalSubagentState(entry.state))) {
-        this.settledGroups.add(group.groupId)
-      } else {
-        this.settledGroups.delete(group.groupId)
-      }
-    }
-    // Emit the final roster and reply before releasing their cached ownership together.
-    for (const groupId of this.settledGroups) {
-      if (this.groups.size <= MAX_GROUPS) {
-        break
-      }
-      const group = this.groups.get(groupId)
-      if (group) {
-        for (const id of group.entries.keys()) {
-          this.groupOf.delete(id)
-          this.settledIds.set(id, true)
-        }
-      }
-      this.groups.delete(groupId)
-      this.settledGroups.delete(groupId)
-    }
-  }
-
   private groupEvent(group: RosterGroup, join: ProviderTimelineJoin): AcpTimelineEvent[] {
     const entries = [...group.entries.values()]
     const body = subagentGroupJournalBody(group.groupId, entries)
diff --git a/src/main/claude/claude-subagent-group-row.ts b/src/main/claude/claude-subagent-group-row.ts
index 051970a5b36..be51effa2cc 100644
--- a/src/main/claude/claude-subagent-group-row.ts
+++ b/src/main/claude/claude-subagent-group-row.ts
@@ -93,13 +93,28 @@ export function writeClaudeSubagentGroupRow(
 ): void {
   const agents = [...group.entries.values()].map((tracked) => tracked.entry)
   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) {
+    const serialized = JSON.stringify(claudeSubagentGroupBody(group.groupId, []))
+    if (serialized === group.lastSerialized) {
+      return
+    }
+    // Reclassification removes the row; refused tombstones remain retryable.
+    const admission = sink.tryAppendTombstone?.(group.identity)
+    if (admission && !admission.accepted) {
       group.lastSerialized = null
+      return
+    }
+    if (!admission) {
       sink.appendTombstone(group.identity)
+    }
+    const publication = sink.tryPublish?.()
+    if (publication && !publication.accepted) {
+      group.lastSerialized = null
+      return
+    }
+    if (!publication) {
       sink.publish()
     }
+    group.lastSerialized = serialized
     return
   }
   const body = claudeSubagentGroupBody(group.groupId, agents)
@@ -108,7 +123,22 @@ export function writeClaudeSubagentGroupRow(
     // Nothing changed — a duplicate delivery must not burn a revision.
     return
   }
+  const options = { turnScope: group.turnScope }
+  const admission = sink.tryAppendItem?.(group.identity, body, options)
+  if (admission && !admission.accepted) {
+    group.lastSerialized = null
+    return
+  }
+  if (!admission) {
+    sink.appendItem(group.identity, body, options)
+  }
+  const publication = sink.tryPublish?.()
+  if (publication && !publication.accepted) {
+    group.lastSerialized = null
+    return
+  }
+  if (!publication) {
+    sink.publish()
+  }
   group.lastSerialized = serialized
-  sink.appendItem(group.identity, body, { turnScope: group.turnScope })
-  sink.publish()
 }
diff --git a/src/main/claude/claude-subagent-roster-groups.test.ts b/src/main/claude/claude-subagent-roster-groups.test.ts
index 0a790f44111..eee98ae3eaf 100644
--- a/src/main/claude/claude-subagent-roster-groups.test.ts
+++ b/src/main/claude/claude-subagent-roster-groups.test.ts
@@ -7,6 +7,7 @@ import type { NativeChatSubagentEntry } from '../../shared/native-chat-types'
 import type { JournaledClaudeSubagentGroup } from './claude-subagent-group-row'
 import type { ClaudeJournaledRosterSource } from './claude-subagent-journaled-roster'
 import { ClaudeSubagentRosterGroups } from './claude-subagent-roster-groups'
+import { inheritedClaudeSubagentGroup } from './claude-subagent-group-row'
 
 const entry = (id: string): NativeChatSubagentEntry => ({
   id,
@@ -51,8 +52,7 @@ describe('ClaudeSubagentRosterGroups', () => {
     ]) {
       const groups = new ClaudeSubagentRosterGroups({
         journaled: journaledTwiceListed(),
-        currentTurnScope: () => AGENT_JOURNAL_THREAD_SCOPE,
-        onEvicted: () => {}
+        currentTurnScope: () => AGENT_JOURNAL_THREAD_SCOPE
       })
       for (const id of order) {
         groups.locateOrInherit(id)
@@ -65,14 +65,16 @@ describe('ClaudeSubagentRosterGroups', () => {
   it('keeps a child placed in a held row when another row listing it is evicted', () => {
     const groups = new ClaudeSubagentRosterGroups({
       journaled: journaledTwiceListed(),
-      currentTurnScope: () => AGENT_JOURNAL_THREAD_SCOPE,
-      onEvicted: () => {}
+      currentTurnScope: () => AGENT_JOURNAL_THREAD_SCOPE
     })
-    groups.locateOrInherit('agent-b')
+    const inherited = groups.locateOrInherit('agent-b')
     groups.locateOrInherit('agent-a')
+    if (inherited) {
+      groups.trim(inherited.group)
+    }
     // Enough of this run's own rows to push the older inherited row out.
     for (let turn = 0; turn < 31; turn += 1) {
-      groups.groupFor(`turn-${turn}-new`)
+      groups.trim(groups.groupFor(`turn-${turn}-new`))
     }
     expect(groups.get('turn-a')).toBeUndefined()
     expect(groups.locate('agent-b')).toBeNull()
@@ -83,10 +85,68 @@ describe('ClaudeSubagentRosterGroups', () => {
     const live = turnScope('turn-live')
     const groups = new ClaudeSubagentRosterGroups({
       journaled: journaledTwiceListed(),
-      currentTurnScope: () => live,
-      onEvicted: () => {}
+      currentTurnScope: () => live
     })
     expect(groups.locateOrInherit('agent-b')?.group.turnScope).toEqual(turnScope('turn-a'))
     expect(groups.groupFor('turn-live').turnScope).toEqual(live)
   })
 })
+
+it('bounds settled groups and invocation identities without evicting live groups', () => {
+  const groups = new ClaudeSubagentRosterGroups({
+    currentTurnScope: () => AGENT_JOURNAL_THREAD_SCOPE
+  })
+  for (let index = 0; index < 35; index++) {
+    const group = groups.groupFor(`live-${index}`)
+    const tracked = inheritedClaudeSubagentGroup(
+      'seed',
+      {
+        entries: [{ ...entry(`live-child-${index}`), state: 'working' }],
+        turnScope: AGENT_JOURNAL_THREAD_SCOPE
+      },
+      () => 1
+    ).entries.get(`live-child-${index}`)
+    if (!tracked) {
+      throw new Error('missing fixture child')
+    }
+    group.entries.set(tracked.entry.id, tracked)
+    group.lastSerialized = 'written'
+    groups.place(tracked.entry.id, group.groupId)
+    groups.trim(group)
+  }
+  for (let index = 0; index < 1100; index++) {
+    const group = groups.groupFor(`settled-${index}`)
+    const id = `settled-child-${index}`
+    const tracked = inheritedClaudeSubagentGroup(
+      'seed',
+      {
+        entries: [entry(id)],
+        turnScope: AGENT_JOURNAL_THREAD_SCOPE
+      },
+      () => 1
+    ).entries.get(id)
+    if (!tracked) {
+      throw new Error('missing fixture child')
+    }
+    tracked.invocationIds = new Set([`tool-${index}`])
+    group.entries.set(id, tracked)
+    group.lastSerialized = 'written'
+    groups.place(id, group.groupId)
+    groups.trim(group)
+  }
+  expect([...groups.values()]).toHaveLength(35)
+  expect(groups.locate('live-child-0')?.tracked.entry.state).toBe('working')
+  expect(groups.locate('settled-child-1099')).toBeNull()
+  expect(groups.hasSettled('settled-child-1099', 'tool-1099')).toBe(true)
+  expect(groups.hasSettled('settled-child-0', 'tool-0')).toBe(false)
+  for (const group of groups.values()) {
+    for (const tracked of group.entries.values()) {
+      tracked.entry.state = 'completed'
+    }
+    groups.trim(group)
+  }
+  expect([...groups.values()]).toHaveLength(32)
+  groups.clear()
+  expect([...groups.values()]).toHaveLength(0)
+  expect(groups.hasSettled('settled-child-1099', 'tool-1099')).toBe(false)
+})
diff --git a/src/main/claude/claude-subagent-roster-groups.ts b/src/main/claude/claude-subagent-roster-groups.ts
index ea4ce76cdfb..757ceb44c61 100644
--- a/src/main/claude/claude-subagent-roster-groups.ts
+++ b/src/main/claude/claude-subagent-roster-groups.ts
@@ -2,6 +2,7 @@
 // wrote, and the ones earlier runs of the session journaled, inherited one at a
 // time as this run's own events reach them.
 
+import { SubagentRosterRetention } from '../native-chat/subagent-roster-retention'
 import {
   claudeSubagentGroupIdentity,
   inheritedClaudeSubagentGroup
@@ -10,8 +11,7 @@ import type { AgentJournalTurnScope } from '../../shared/agent-session-journal-t
 import type { ClaudeJournaledRosterSource } from './claude-subagent-journaled-roster'
 import type { RosterGroup, TrackedEntry } from './claude-subagent-roster-state'
 
-/** Spawn-group rows kept live per session. Bounds an event-accumulated map that
- *  no provider snapshot ever prunes. */
+/** Settled history target; groups with unfinished children remain owned. */
 const MAX_SUBAGENT_GROUPS = 32
 
 export type LocatedClaudeSubagent = { group: RosterGroup; tracked: TrackedEntry }
@@ -22,14 +22,33 @@ export class ClaudeSubagentRosterGroups {
    *  from an earlier turn revises that turn's row instead of the live one. */
   private readonly groupIdByEntry = new Map<string, string>()
 
+  private readonly retention = new SubagentRosterRetention(this.groups, {
+    maxGroups: MAX_SUBAGENT_GROUPS,
+    maxSettledIdentities: 2048,
+    entries: (group) => [...group.entries.values()].map((tracked) => tracked.entry),
+    identities: (group) =>
+      [...group.entries]
+        .filter(([id]) => this.groupIdByEntry.get(id) === group.groupId)
+        .flatMap(([id, tracked]) => [
+          claudeSubagentRetentionIdentity(id, null),
+          ...[...new Set([...(tracked.invocationIds ?? []), tracked.toolUseId])].map((toolUseId) =>
+            claudeSubagentRetentionIdentity(id, toolUseId)
+          )
+        ]),
+    onEvict: (group) => {
+      for (const id of group.entries.keys()) {
+        if (this.groupIdByEntry.get(id) === group.groupId) {
+          this.groupIdByEntry.delete(id)
+        }
+      }
+    }
+  })
+
   constructor(
     private readonly deps: {
       journaled?: ClaudeJournaledRosterSource
       /** The open turn's scope, which a group this run creates belongs to. */
       currentTurnScope: () => AgentJournalTurnScope
-      /** Once a group leaves the map nothing can reach its children again — not
-       *  even a session sweep — so contact is lost here. */
-      onEvicted: (group: RosterGroup) => void
     }
   ) {}
 
@@ -88,7 +107,16 @@ export class ClaudeSubagentRosterGroups {
     this.groupIdByEntry.delete(id)
   }
 
+  hasSettled(id: string, toolUseId: string | null): boolean {
+    return this.retention.hasSettled(claudeSubagentRetentionIdentity(id, toolUseId))
+  }
+
+  trim(group: RosterGroup, retainAccessed = false): void {
+    this.retention.trim([group], retainAccessed ? group.groupId : undefined)
+  }
+
   clear(): void {
+    this.retention.clear()
     this.groups.clear()
     this.groupIdByEntry.clear()
   }
@@ -114,21 +142,9 @@ export class ClaudeSubagentRosterGroups {
 
   private admit(group: RosterGroup): void {
     this.groups.set(group.groupId, group)
-    while (this.groups.size > MAX_SUBAGENT_GROUPS) {
-      const oldest = this.groups.keys().next()
-      if (oldest.done || oldest.value === group.groupId) {
-        break
-      }
-      const evicted = this.groups.get(oldest.value)
-      if (evicted) {
-        this.deps.onEvicted(evicted)
-      }
-      for (const id of evicted?.entries.keys() ?? []) {
-        if (this.groupIdByEntry.get(id) === oldest.value) {
-          this.groupIdByEntry.delete(id)
-        }
-      }
-      this.groups.delete(oldest.value)
-    }
   }
 }
+
+function claudeSubagentRetentionIdentity(id: string, toolUseId: string | null): string {
+  return JSON.stringify([id, toolUseId])
+}
diff --git a/src/main/claude/claude-subagent-roster-retention.test.ts b/src/main/claude/claude-subagent-roster-retention.test.ts
new file mode 100644
index 00000000000..17776d48b27
--- /dev/null
+++ b/src/main/claude/claude-subagent-roster-retention.test.ts
@@ -0,0 +1,196 @@
+import { describe, expect, it } from 'vitest'
+import {
+  AGENT_JOURNAL_THREAD_SCOPE,
+  type AgentJournalItemBody,
+  type AgentJournalItemIdentity
+} from '../../shared/agent-session-journal-types'
+import { isSubagentGroupBlock } from '../../shared/native-chat-types'
+import type { StructuredAgentSessionEventSink } from '../native-chat/agent-session-wire/structured-agent-session-event-sink'
+import { ClaudeSubagentRoster } from './claude-subagent-roster'
+import type { ClaudeJournaledRosterSource } from './claude-subagent-journaled-roster'
+
+function harness(journaled?: ClaudeJournaledRosterSource) {
+  const rows = new Map<string, AgentJournalItemBody>()
+  let group = 'oldest'
+  let writes = 0
+  let refuseAppend = false
+  let refusePublish = false
+  const append = (identity: AgentJournalItemIdentity, body: AgentJournalItemBody): void => {
+    if (identity.provider !== 'orca') {
+      throw new Error('unexpected roster identity')
+    }
+    rows.set(identity.clientMessageId, body)
+    writes++
+  }
+  const sink: StructuredAgentSessionEventSink = {
+    appendItem: append,
+    appendTombstone: () => {},
+    publish: () => {},
+    tryAppendItem: (identity, body) => {
+      if (refuseAppend) {
+        return { accepted: false, reason: 'backpressure' }
+      }
+      append(identity, body)
+      return { accepted: true }
+    },
+    tryPublish: () =>
+      refusePublish ? { accepted: false, reason: 'backpressure' } : { accepted: true }
+  }
+  const roster = new ClaudeSubagentRoster({
+    sink,
+    journaled,
+    currentGroupKey: () => group,
+    currentTurnScope: () => AGENT_JOURNAL_THREAD_SCOPE
+  })
+  const start = (id: string, tool = id, backgrounded = false): void => {
+    roster.observeSystemFrame({
+      type: 'system',
+      subtype: 'task_started',
+      task_type: 'local_agent',
+      task_id: id,
+      tool_use_id: tool,
+      description: id,
+      is_backgrounded: backgrounded
+    })
+  }
+  const finish = (id: string, tool = id): void => {
+    roster.observeSystemFrame({
+      type: 'system',
+      subtype: 'task_notification',
+      task_id: id,
+      tool_use_id: tool,
+      status: 'completed'
+    })
+  }
+  const agents = (key: string) => {
+    const body = rows.get(`claude-subagents:${key}`)
+    return body?.kind === 'message' ? (body.blocks.find(isSubagentGroupBlock)?.agents ?? []) : []
+  }
+  const churn = (count: number, settled = true): void => {
+    for (let index = 0; index < count; index++) {
+      group = `later-${index}`
+      start(`later-child-${index}`)
+      if (settled) {
+        finish(`later-child-${index}`)
+      }
+    }
+  }
+  return {
+    roster,
+    start,
+    finish,
+    agents,
+    churn,
+    writes: () => writes,
+    setGroup: (key: string) => {
+      group = key
+    },
+    refuse: (append: boolean, publish: boolean) => {
+      refuseAppend = append
+      refusePublish = publish
+    }
+  }
+}
+
+describe('Claude shared settled-only roster retention', () => {
+  it('keeps every child of the oldest live group past 33 later spawn groups', () => {
+    const h = harness()
+    h.start('a', 'tool-a', true)
+    h.start('b', 'tool-b', true)
+    h.roster.settleTurn('oldest')
+    h.churn(34)
+    expect(h.agents('oldest').map((entry) => entry.state)).toEqual(['working', 'working'])
+    h.finish('a', 'tool-a')
+    expect(h.agents('oldest').map((entry) => entry.state)).toEqual(['completed', 'working'])
+    h.finish('b', 'tool-b')
+    expect(h.agents('oldest').map((entry) => entry.id)).toEqual(['a', 'b'])
+    expect(h.agents('oldest').map((entry) => entry.state)).toEqual(['completed', 'completed'])
+  })
+
+  it('reaches every still-running group in the session-end sweep', () => {
+    const h = harness()
+    h.start('a', 'tool-a', true)
+    h.start('b')
+    h.churn(34, false)
+    h.roster.settleSession()
+    expect(h.agents('oldest').map((entry) => entry.state)).toEqual(['unverifiable', 'unverifiable'])
+    expect(h.agents('later-33')[0].state).toBe('unverifiable')
+  })
+
+  it('ignores old announcements after settled eviction and alias-cache churn, but admits a new invocation', () => {
+    const h = harness()
+    h.start('a', 'first')
+    h.finish('a', 'first')
+    h.start('a', 'second')
+    h.finish('a', 'second')
+    h.churn(600)
+    const before = h.writes()
+    h.start('a', 'first')
+    h.start('a', 'second')
+    h.roster.observeSystemFrame({
+      type: 'system',
+      subtype: 'task_started',
+      task_type: 'local_agent',
+      task_id: 'a'
+    })
+    h.roster.observeChildActivity('first')
+    expect(h.writes()).toBe(before)
+    expect(h.roster.linkage.settledLinkageFor('first').linkage.agentId).toBe('a')
+    h.setGroup('resumed')
+    h.start('a', 'third')
+    expect(h.agents('resumed')).toEqual([expect.objectContaining({ id: 'a', state: 'working' })])
+  })
+
+  it('keeps an inherited row reachable when child traffic precedes its resume announcement', () => {
+    let claimed = false
+    const h = harness({
+      canonical: (tool) => (tool === 'original-spawn' ? 'a' : null),
+      groupOf: (id) => (['a', 'b'].includes(id) ? 'inherited' : null),
+      claimGroup: (group) => {
+        if (group !== 'inherited' || claimed) {
+          return null
+        }
+        claimed = true
+        return {
+          entries: ['a', 'b'].map((id) => ({
+            id,
+            label: id,
+            state: 'completed',
+            startedAt: 1,
+            settledAt: 2
+          })),
+          turnScope: AGENT_JOURNAL_THREAD_SCOPE
+        }
+      },
+      attempt: () => 4
+    })
+    h.churn(32, false)
+    h.roster.observeChildActivity('original-spawn')
+    h.setGroup('resumed')
+    h.start('a', 'resume-tool', true)
+    expect(h.agents('inherited').map((entry) => entry.state)).toEqual(['working', 'completed'])
+    expect(h.agents('resumed')).toHaveLength(0)
+    expect(h.roster.linkage.settledLinkageFor('original-spawn').linkage).toMatchObject({
+      agentId: 'a',
+      attempt: 5
+    })
+  })
+
+  for (const failure of ['append', 'publish']) {
+    it(`retains a terminal group whose final ${failure} was refused and retries it`, () => {
+      const h = harness()
+      h.start('a')
+      h.start('b')
+      h.refuse(failure === 'append', failure === 'publish')
+      h.finish('a')
+      h.finish('b')
+      h.refuse(false, false)
+      h.churn(34)
+      h.finish('b')
+      expect(h.agents('oldest').map((entry) => entry.state)).toEqual(['completed', 'completed'])
+      const before = h.writes()
+      h.start('a')
+      expect(h.writes()).toBe(before)
+    })
+  }
+})
diff --git a/src/main/claude/claude-subagent-roster.test.ts b/src/main/claude/claude-subagent-roster.test.ts
index db942502ee0..1547f4bd330 100644
--- a/src/main/claude/claude-subagent-roster.test.ts
+++ b/src/main/claude/claude-subagent-roster.test.ts
@@ -367,13 +367,13 @@ describe('ClaudeSubagentRoster', () => {
   })
 
   describe('groups that no later event can reach', () => {
-    it('loses contact with a group evicted past the bound', () => {
+    it('retains live groups past the settled-history 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-0')).toEqual([expect.objectContaining({ state: 'working' })])
       expect(rolesIn('turn-32')).toEqual([expect.objectContaining({ state: 'working' })])
     })
 
diff --git a/src/main/claude/claude-subagent-roster.ts b/src/main/claude/claude-subagent-roster.ts
index baeb72e3ffb..548613136d0 100644
--- a/src/main/claude/claude-subagent-roster.ts
+++ b/src/main/claude/claude-subagent-roster.ts
@@ -87,8 +87,7 @@ export class ClaudeSubagentRoster {
     this.now = deps.now ?? (() => Date.now())
     this.groups = new ClaudeSubagentRosterGroups({
       journaled: deps.journaled,
-      currentTurnScope: deps.currentTurnScope,
-      onEvicted: (group) => this.sweep(group, true)
+      currentTurnScope: deps.currentTurnScope
     })
     this.ids = new ClaudeSubagentIds(deps.journaled?.canonical)
     this.linkage = new ClaudeSubagentLinkage({
@@ -124,6 +123,12 @@ export class ClaudeSubagentRoster {
     if (frame.toolUseId) {
       this.ids.alias(frame.toolUseId, frame.taskId)
     }
+    if (
+      this.groups.hasSettled(frame.taskId, frame.toolUseId) &&
+      (frame.toolUseId !== null || !this.groups.locate(frame.taskId))
+    ) {
+      return true
+    }
     const located =
       this.groups.locateOrInherit(frame.taskId) ??
       (frame.toolUseId ? this.adopt(frame.toolUseId, frame.taskId) : null)
@@ -158,10 +163,20 @@ export class ClaudeSubagentRoster {
    */
   observeChildActivity(parentToolUseId: string): void {
     const canonical = this.ids.canonical(parentToolUseId)
-    if (this.ids.isExcluded(parentToolUseId, canonical)) {
+    if (
+      this.ids.isExcluded(parentToolUseId, canonical) ||
+      this.groups.hasSettled(canonical, parentToolUseId) ||
+      (!this.groups.locate(canonical) && this.groups.hasSettled(canonical, null))
+    ) {
       return
     }
-    if (this.groups.locateOrInherit(canonical)) {
+    if (this.groups.locate(canonical)) {
+      return
+    }
+    const inherited = this.groups.locateOrInherit(canonical)
+    if (inherited) {
+      // Child traffic can precede the announcement that reopens an inherited row.
+      this.groups.trim(inherited.group, true)
       return
     }
     if (this.announcesTasks) {
@@ -242,7 +257,6 @@ export class ClaudeSubagentRoster {
     if (!group) {
       return
     }
-    let changed = false
     for (const [id, tracked] of group.entries) {
       if (isTerminalSubagentState(tracked.entry.state)) {
         continue
@@ -254,11 +268,13 @@ export class ClaudeSubagentRoster {
         ...tracked,
         entry: { ...tracked.entry, state: 'unverifiable', settledAt: this.now() }
       })
-      changed = true
-    }
-    if (changed) {
-      writeClaudeSubagentGroupRow(this.deps.sink, group)
     }
+    this.write(group)
+  }
+
+  private write(group: RosterGroup): void {
+    writeClaudeSubagentGroupRow(this.deps.sink, group)
+    this.groups.trim(group)
   }
 
   private create(
@@ -270,6 +286,7 @@ export class ClaudeSubagentRoster {
   ): void {
     const group = this.groups.groupFor(this.deps.currentGroupKey() ?? OUTSIDE_TURN)
     if (group.admittedEntries >= MAX_SUBAGENTS_PER_GROUP) {
+      this.write(group)
       return
     }
     group.admittedEntries += 1
@@ -291,7 +308,7 @@ export class ClaudeSubagentRoster {
       }
     })
     this.groups.place(id, group.groupId)
-    writeClaudeSubagentGroupRow(this.deps.sink, group)
+    this.write(group)
   }
 
   private revise(
@@ -332,7 +349,7 @@ export class ClaudeSubagentRoster {
       }
     }
     group.entries.set(id, next)
-    writeClaudeSubagentGroupRow(this.deps.sink, group)
+    this.write(group)
   }
 
   /** Re-key a provisional entry from its tool id onto the canonical task id the
@@ -362,6 +379,6 @@ export class ClaudeSubagentRoster {
     }
     located.group.entries.delete(id)
     this.groups.forget(id)
-    writeClaudeSubagentGroupRow(this.deps.sink, located.group)
+    this.write(located.group)
   }
 }
diff --git a/src/main/codex/codex-structured-journal-limits.ts b/src/main/codex/codex-structured-journal-limits.ts
index d4c9bcfa0de..82ad7a38235 100644
--- a/src/main/codex/codex-structured-journal-limits.ts
+++ b/src/main/codex/codex-structured-journal-limits.ts
@@ -11,9 +11,9 @@ export const MAX_CODEX_PENDING_PROMPTS = 128
 export const MAX_CODEX_IDENTITY_ENTRIES = 512
 export const MAX_CODEX_DETAIL_ENTRIES = 512
 export const MAX_CODEX_DETAIL_BYTES = 64 * 1024
-/** Spawn-group rows kept live per session, and children per row. Both bound an
- *  event-accumulated map that no provider snapshot ever prunes. */
+/** Settled spawn-group history budget; live groups remain until their final write succeeds. */
 export const MAX_CODEX_SUBAGENT_GROUPS = 32
+/** Children admitted per spawn-group row. */
 export const MAX_CODEX_SUBAGENTS_PER_GROUP = 64
 /** Threads whose latest token total is retained. Usage frames arrive for
  *  threads that are not yet (or never become) roster children. */
diff --git a/src/main/codex/codex-subagent-roster-retention.test.ts b/src/main/codex/codex-subagent-roster-retention.test.ts
new file mode 100644
index 00000000000..92de0fc2aea
--- /dev/null
+++ b/src/main/codex/codex-subagent-roster-retention.test.ts
@@ -0,0 +1,322 @@
+import { mkdtemp, rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, describe, expect, it } from 'vitest'
+import { codexProviderHandle } from '../../shared/agent-session-provider-handle-encoding'
+import { isSubagentGroupBlock, type NativeChatSubagentState } from '../../shared/native-chat-types'
+import { createTrackedJournalOpener } from '../native-chat/agent-session-journal/journal-host-database-test-support'
+import {
+  createDeferredStructuredAgentSessionEventSink,
+  type StructuredAgentSessionEventSink
+} from '../native-chat/agent-session-wire/structured-agent-session-event-sink'
+import { testEventSinkLogging } from '../native-chat/agent-session-wire/structured-agent-session-logger-test-support'
+import { CodexSubagentRoster } from './codex-subagent-roster'
+import { MAX_CODEX_SUBAGENT_GROUPS } from './codex-structured-journal-limits'
+
+const THREAD = 'parent'
+const ORIGINAL = 'original'
+const journals = createTrackedJournalOpener()
+const cleanups: (() => Promise<void>)[] = []
+afterEach(async () => {
+  for (const cleanup of cleanups.splice(0)) {
+    await cleanup()
+  }
+  await journals.closeAll()
+})
+
+async function session(refuse?: 'append' | 'publish') {
+  const root = await mkdtemp(join(tmpdir(), 'orca-codex-roster-retention-'))
+  const journal = await journals.open({
+    identity: {
+      sessionId: 'session-codex-roster-retention',
+      workspaceId: 'workspace-1',
+      hostId: 'local',
+      agent: 'codex',
+      providerHandle: codexProviderHandle(THREAD)
+    },
+    stateDirectory: root,
+    now: () => 1_000
+  })
+  const deferred = createDeferredStructuredAgentSessionEventSink(testEventSinkLogging())
+  deferred.bind({ journal, fence: 1, publish: () => {} })
+  const append = deferred.sink.tryAppendItem
+  const publish = deferred.sink.tryPublish
+  if (!append || !publish) {
+    throw new Error('the deferred sink must expose append and publish admission')
+  }
+  let refusing = false
+  let writingOriginal = false
+  const refusal = { accepted: false, reason: 'backpressure' } as const
+  const sink: StructuredAgentSessionEventSink = {
+    ...deferred.sink,
+    tryAppendItem: (identity, body, options) => {
+      writingOriginal =
+        identity.provider === 'orca' &&
+        identity.clientMessageId === `codex-subagents:${THREAD}:${ORIGINAL}`
+      return refusing && writingOriginal && refuse === 'append'
+        ? refusal
+        : append(identity, body, options)
+    },
+    tryPublish: () => (refusing && writingOriginal && refuse === 'publish' ? refusal : publish())
+  }
+  let parentTurn = ORIGINAL
+  let clock = 1_000
+  const roster = new CodexSubagentRoster({
+    sink,
+    primaryThreadId: () => THREAD,
+    activeTurn: () => parentTurn,
+    turnScopeFor: (_thread, turnId) => ({ kind: 'turn', turnItemId: turnId ?? 'outside-turn' }),
+    now: () => ++clock
+  })
+  cleanups.push(async () => {
+    roster.dispose()
+    deferred.close()
+    await journal.close()
+    await rm(root, { recursive: true, force: true })
+  })
+  const turn = (id: string, state: NativeChatSubagentState, turnId = `execution:${id}`) =>
+    roster.handleTurn({ threadId: id, turnId, state })
+  const announce = (id: string, kind = 'started') =>
+    roster.handleItem({
+      threadId: THREAD,
+      turnId: parentTurn,
+      item: {
+        type: 'subAgentActivity',
+        id: `activity:${id}:${kind}`,
+        agentThreadId: id,
+        agentPath: '/root/task',
+        kind
+      }
+    })
+  function spawn(id: string, parent = ORIGINAL) {
+    parentTurn = parent
+    expect(turn(id, 'working')).toEqual({ accepted: true })
+    expect(announce(id)).toEqual({ accepted: true })
+  }
+  async function rows() {
+    await deferred.drained()
+    return journal
+      .snapshot()
+      .items.flatMap((row) =>
+        row.body.kind === 'message'
+          ? row.body.blocks.filter(isSubagentGroupBlock).map((group) => ({ row, group }))
+          : []
+      )
+  }
+  return {
+    roster,
+    turn,
+    announce,
+    spawn,
+    rows,
+    original: async () =>
+      (await rows()).find(({ group }) => group.groupId === `${THREAD}:${ORIGINAL}`),
+    parent: (turnId: string) => {
+      parentTurn = turnId
+    },
+    refuse: (value: boolean) => {
+      refusing = value
+    }
+  }
+}
+
+type Session = Awaited<ReturnType<typeof session>>
+async function laterGroups(s: Session, settled: boolean, count = MAX_CODEX_SUBAGENT_GROUPS + 2) {
+  for (let index = 0; index < count; index++) {
+    const id = `later-child-${index}`
+    s.spawn(id, `later-parent-${index}`)
+    if (settled) {
+      expect(s.turn(id, 'completed')).toEqual({ accepted: true })
+    }
+    if (index % 32 === 31) {
+      await s.rows()
+    }
+  }
+  await s.rows()
+}
+
+function states(s: Awaited<ReturnType<Session['original']>>) {
+  return s?.group.agents.map(({ id, state }) => ({ id, state }))
+}
+
+describe('Codex roster retention through the real sink and journal', () => {
+  it.each([
+    [false, 'completed'],
+    [true, 'completed'],
+    [false, 'sweep'],
+    [true, 'sweep']
+  ] as const)(
+    'preserves all oldest live children when later groups settled=%s and final event=%s',
+    async (settled, final) => {
+      const s = await session()
+      for (const id of ['old-a', 'old-b', 'old-c']) {
+        s.spawn(id)
+      }
+      const before = await s.original()
+      expect(before?.group.agents).toHaveLength(3)
+      await laterGroups(s, settled)
+      s.parent('current')
+      s.announce('old-a', 'interacted')
+      expect(states(await s.original())).toEqual(
+        ['old-a', 'old-b', 'old-c'].map((id) => ({ id, state: 'working' }))
+      )
+      if (final === 'sweep') {
+        expect(s.roster.settleSession()).toEqual({ accepted: true })
+      } else {
+        for (const id of ['old-a', 'old-b', 'old-c']) {
+          s.turn(id, 'completed')
+        }
+      }
+      const after = await s.original()
+      expect(after?.row.itemId).toBe(before?.row.itemId)
+      expect(after?.row.turnScope).toEqual(before?.row.turnScope)
+      expect(states(after)).toEqual(
+        ['old-a', 'old-b', 'old-c'].map((id) => ({
+          id,
+          state: final === 'sweep' ? 'unverifiable' : 'completed'
+        }))
+      )
+      expect(after?.group.agents.every((entry) => entry.settledAt !== undefined)).toBe(true)
+      expect(
+        (await s.rows()).flatMap(({ group }) =>
+          group.agents.filter((entry) => entry.id === 'old-a')
+        )
+      ).toHaveLength(1)
+    }
+  )
+
+  it('ignores late reports for evicted settled executions even after the execution cache has pruned them', async () => {
+    const s = await session()
+    s.spawn('old-a')
+    s.spawn('old-b')
+    s.turn('old-a', 'stopped')
+    s.turn('old-b', 'completed')
+    const before = await s.original()
+    await laterGroups(s, true, 270)
+    expect(s.roster.executions.find('old-a')).toBeUndefined()
+    expect(s.roster.retentionSizes().groups).toBe(MAX_CODEX_SUBAGENT_GROUPS)
+    s.parent('current')
+    s.turn('old-a', 'working')
+    s.announce('old-a')
+    s.announce('old-a', 'interacted')
+    s.turn('old-a', 'completed')
+    s.announce('old-a', 'completed')
+    s.roster.handleTokenUsage({ threadId: 'old-a', tokenUsage: { total: { totalTokens: 123 } } })
+    expect(await s.original()).toEqual(before)
+    expect(s.roster.executions.find('old-a')?.execution).toBeNull()
+    expect(
+      (await s.rows()).flatMap(({ group }) => group.agents.filter((entry) => entry.id === 'old-a'))
+    ).toHaveLength(1)
+  })
+
+  it.each([
+    ['before', false],
+    ['after', false],
+    ['before', true],
+    ['after', true]
+  ] as const)(
+    'admits a genuine new child turn when the announcement is %s its start and execution cache pruned=%s',
+    async (order, pruned) => {
+      const s = await session()
+      s.spawn('old-a')
+      s.turn('old-a', 'completed')
+      const before = await s.original()
+      await laterGroups(s, true, pruned ? 270 : MAX_CODEX_SUBAGENT_GROUPS + 2)
+      s.parent('follow-up')
+      if (order === 'before') {
+        s.announce('old-a', 'interacted')
+      }
+      s.turn('old-a', 'working', 'new-execution')
+      if (order === 'after') {
+        s.announce('old-a', 'interacted')
+      }
+      const followup = () =>
+        s.rows().then((rows) => rows.find(({ group }) => group.groupId === `${THREAD}:follow-up`))
+      expect(states(await followup())).toEqual([{ id: 'old-a', state: 'working' }])
+      s.turn('old-a', 'working')
+      s.turn('old-a', 'completed')
+      expect(states(await followup())).toEqual([{ id: 'old-a', state: 'working' }])
+      s.turn('old-a', 'completed', 'new-execution')
+      expect(states(await followup())).toEqual([{ id: 'old-a', state: 'completed' }])
+      expect(await s.original()).toEqual(before)
+    }
+  )
+
+  it('suppresses both settled executions after same-group reuse, eviction and execution-cache churn', async () => {
+    const s = await session()
+    s.spawn('old-a')
+    s.spawn('old-b')
+    s.turn('old-a', 'completed')
+    s.announce('old-a', 'interacted')
+    s.turn('old-a', 'working', 'second-execution')
+    s.turn('old-a', 'completed', 'second-execution')
+    s.turn('old-b', 'completed')
+    const original = await s.original()
+    await laterGroups(s, true, 270)
+    expect(s.roster.executions.find('old-a')).toBeUndefined()
+    expect(s.roster.retentionSizes().settledIdentities).toBeLessThan(2048)
+    const before = await s.rows()
+    s.parent('current')
+    for (const turnId of ['execution:old-a', 'second-execution']) {
+      s.turn('old-a', 'working', turnId)
+      s.announce('old-a')
+      s.turn('old-a', 'completed', turnId)
+      s.announce('old-a', 'completed')
+    }
+    expect(await s.rows()).toEqual(before)
+    s.announce('old-a', 'interacted')
+    s.turn('old-a', 'working', 'third-execution')
+    const current = (await s.rows()).find(({ group }) => group.groupId === `${THREAD}:current`)
+    expect(states(current)).toEqual([{ id: 'old-a', state: 'working' }])
+    s.turn('old-a', 'completed', 'third-execution')
+    expect(await s.original()).toEqual(original)
+  })
+
+  it.each(['append', 'publish'] as const)(
+    'retains final retry ownership after %s refuses settlement under group pressure',
+    async (refuse) => {
+      const s = await session(refuse)
+      s.spawn('old-a')
+      s.spawn('old-b')
+      const before = await s.original()
+      await laterGroups(s, false)
+      s.turn('old-b', 'completed')
+      s.refuse(true)
+      expect(s.turn('old-a', 'completed')).toEqual({ accepted: false, reason: 'backpressure' })
+      s.spawn('more-live', 'current')
+      expect(s.roster.retentionSizes().groups).toBeGreaterThan(MAX_CODEX_SUBAGENT_GROUPS)
+      s.refuse(false)
+      expect(s.roster.settleSession()).toEqual({ accepted: true })
+      const after = await s.original()
+      expect(after?.row.itemId).toBe(before?.row.itemId)
+      expect(states(after)).toEqual([
+        { id: 'old-a', state: 'completed' },
+        { id: 'old-b', state: 'completed' }
+      ])
+      expect(s.roster.retentionSizes().groups).toBe(MAX_CODEX_SUBAGENT_GROUPS)
+    }
+  )
+
+  it.each(['append', 'publish'] as const)(
+    'retries a refused final sweep %s after more live groups arrive',
+    async (refuse) => {
+      const s = await session(refuse)
+      s.spawn('old-a')
+      s.spawn('old-b')
+      const before = await s.original()
+      await laterGroups(s, false)
+      s.refuse(true)
+      expect(s.roster.settleSession()).toEqual({ accepted: false, reason: 'backpressure' })
+      s.spawn('more-live', 'current')
+      s.refuse(false)
+      expect(s.roster.settleSession()).toEqual({ accepted: true })
+      const after = await s.original()
+      expect(after?.row.itemId).toBe(before?.row.itemId)
+      expect(states(after)).toEqual([
+        { id: 'old-a', state: 'unverifiable' },
+        { id: 'old-b', state: 'unverifiable' }
+      ])
+      expect(s.roster.retentionSizes().groups).toBe(MAX_CODEX_SUBAGENT_GROUPS)
+    }
+  )
+})
diff --git a/src/main/codex/codex-subagent-roster-state.ts b/src/main/codex/codex-subagent-roster-state.ts
index 02c79411b79..ccbef83ade6 100644
--- a/src/main/codex/codex-subagent-roster-state.ts
+++ b/src/main/codex/codex-subagent-roster-state.ts
@@ -5,6 +5,12 @@ import type {
   AgentJournalTurnScope
 } from '../../shared/agent-session-journal-types'
 import type { NativeChatSubagentEntry } from '../../shared/native-chat-types'
+import { isTerminalSubagentState } from '../../shared/native-chat-subagent-summary'
+import { SubagentRosterRetention } from '../native-chat/subagent-roster-retention'
+import {
+  MAX_CODEX_SUBAGENT_GROUPS,
+  MAX_CODEX_SUBAGENTS_PER_GROUP
+} from './codex-structured-journal-limits'
 
 /** The turn a group belongs to when Codex reports activity outside any turn.
  *  Mirrors the generic-frame bucket name so the two read alike in the journal. */
@@ -22,6 +28,41 @@ export type RosterGroup = {
   lastSerialized: string | null
 }
 
+/** A reused child thread starts a new execution only when its turn id changes. */
+export function codexSubagentExecutionIdentity(threadId: string, turnId: string): string {
+  return JSON.stringify([threadId, turnId])
+}
+
+export function retainSupersededCodexExecution(
+  group: RosterGroup,
+  threadId: string,
+  nextTurnId: string | null,
+  retention: SubagentRosterRetention<RosterGroup>
+): void {
+  const previousTurnId = group.executionTurns.get(threadId)
+  const previous = group.entries.get(threadId)
+  if (
+    typeof previousTurnId === 'string' &&
+    previousTurnId !== nextTurnId &&
+    previous &&
+    isTerminalSubagentState(previous.state)
+  ) {
+    retention.rememberSettled(codexSubagentExecutionIdentity(threadId, previousTurnId))
+  }
+}
+
+export function createCodexSubagentRosterRetention(groups: Map<string, RosterGroup>) {
+  return new SubagentRosterRetention(groups, {
+    maxGroups: MAX_CODEX_SUBAGENT_GROUPS,
+    maxSettledIdentities: MAX_CODEX_SUBAGENT_GROUPS * MAX_CODEX_SUBAGENTS_PER_GROUP,
+    entries: (group) => group.entries.values(),
+    identities: (group) =>
+      [...group.executionTurns].flatMap(([threadId, turnId]) =>
+        turnId === null ? [] : [codexSubagentExecutionIdentity(threadId, turnId)]
+      )
+  })
+}
+
 /** Group identity: the parent turn that spawned the children. `agentPath` is a
  *  tree rooted at the parent thread, so every child of one turn shares a row
  *  no matter which thread's stream carried its activity item. */
diff --git a/src/main/codex/codex-subagent-roster.test.ts b/src/main/codex/codex-subagent-roster.test.ts
index 3f411fff1a3..ac56c042ba2 100644
--- a/src/main/codex/codex-subagent-roster.test.ts
+++ b/src/main/codex/codex-subagent-roster.test.ts
@@ -569,10 +569,7 @@ describe('CodexSubagentRoster', () => {
     expect(appended).toHaveLength(atCap)
   })
 
-  // The eviction is the KNOWN LIMITATION the module documents: `groups` is never
-  // seeded from the journal, so the evicted group's next child rebuilds its
-  // durable row from that one child. Pinned so the boundary cannot move silently.
-  it('caps live spawn groups, and an evicted group rebuilds its row from one child', () => {
+  it('retains live spawn groups beyond the settled history budget', () => {
     const { roster, appended, agents } = createHarness()
     for (let index = 0; index <= MAX_CODEX_SUBAGENT_GROUPS; index++) {
       deliver(
@@ -581,10 +578,7 @@ describe('CodexSubagentRoster', () => {
         `turn-${index}`
       )
     }
-    const evicted = codexSubagentGroupIdentity(codexSubagentGroupId(THREAD, 'turn-0'))
-    const rowsFor = (identity: AgentJournalItemIdentity): Appended[] =>
-      appended.filter((entry) => JSON.stringify(entry.identity) === JSON.stringify(identity))
-    expect(rowsFor(evicted)).toHaveLength(1)
+    const original = codexSubagentGroupIdentity(codexSubagentGroupId(THREAD, 'turn-0'))
 
     deliver(
       roster,
@@ -592,8 +586,9 @@ describe('CodexSubagentRoster', () => {
       'turn-0'
     )
 
-    expect(latestIdentity(appended)).toEqual(evicted)
-    expect(agents().map((agent) => agent.id)).toEqual(['child-late'])
+    expect(latestIdentity(appended)).toEqual(original)
+    expect(agents().map((agent) => agent.id)).toEqual(['child-0', 'child-late'])
+    expect(roster.retentionSizes().groups).toBe(MAX_CODEX_SUBAGENT_GROUPS + 1)
   })
 
   it('keeps a token count a later thread-map eviction would otherwise retract', () => {
diff --git a/src/main/codex/codex-subagent-roster.ts b/src/main/codex/codex-subagent-roster.ts
index 43d31756954..0b55d231fbe 100644
--- a/src/main/codex/codex-subagent-roster.ts
+++ b/src/main/codex/codex-subagent-roster.ts
@@ -5,15 +5,11 @@
 // child turn events supply execution state.
 //
 // KNOWN LIMITATION: `groups` is process-local and is never seeded from the
-// journal, while the row's identity is keyed on the group id alone. So once a
-// group leaves the map its row stays, and the next activity item rebuilds that
-// row from one child — rewriting N down to one. Two ways in: eviction past
-// MAX_CODEX_SUBAGENT_GROUPS, which drops the oldest-inserted group in-process
-// even while it is live, and skips the sweep so its children never latch
-// `unverifiable`; and a restart on `threadId:outside-turn`, the one group id
-// that outlives the process — `thread/resume` is verified to return the same
-// thread, and a real turn id is assumed freshly minted per turn. Seeding from
-// the journal is the fix.
+// journal, while the row's identity is keyed on the group id alone. After a
+// restart loses membership for `threadId:outside-turn`, the next activity
+// rebuilds that row from one child — rewriting N down to one. This group id
+// outlives the process: `thread/resume` returns the same thread, while real turn
+// ids are assumed freshly minted per turn. Seeding from the journal is the fix.
 
 import type { AgentJournalTurnScope } from '../../shared/agent-session-journal-types'
 import { isTerminalSubagentState } from '../../shared/native-chat-subagent-summary'
@@ -43,13 +39,13 @@ export { codexSubagentGroupId, codexSubagentGroupIdentity } from './codex-subage
 import {
   codexSubagentGroupId,
   codexSubagentGroupIdentity,
+  codexSubagentExecutionIdentity as executionIdentity,
+  createCodexSubagentRosterRetention,
+  retainSupersededCodexExecution,
   type RosterGroup
 } from './codex-subagent-roster-state'
 import type { CodexThreadItem } from './codex-structured-item-translation'
-import {
-  MAX_CODEX_SUBAGENT_GROUPS,
-  MAX_CODEX_SUBAGENTS_PER_GROUP
-} from './codex-structured-journal-limits'
+import { MAX_CODEX_SUBAGENTS_PER_GROUP } from './codex-structured-journal-limits'
 import { CodexThreadTokenTotals } from './codex-thread-token-totals'
 
 const ADMITTED: StructuredAgentSessionSinkAdmission = { accepted: true }
@@ -66,6 +62,7 @@ export type CodexSubagentRosterDeps = {
 
 export class CodexSubagentRoster {
   private readonly groups = new Map<string, RosterGroup>()
+  private readonly retention = createCodexSubagentRosterRetention(this.groups)
   /** Every thread's total, members or not; children are selected at write time. */
   private readonly tokensByThread = new CodexThreadTokenTotals()
   private readonly now: () => number
@@ -115,7 +112,10 @@ export class CodexSubagentRoster {
       // Only a spawn names the spawner: other announcements ride whichever agent acted.
       announcement.spawned ? input.threadId : undefined
     )
-    if (!child?.execution) {
+    if (
+      !child?.execution ||
+      this.retention.hasSettled(executionIdentity(child.agentThreadId, child.execution.turnId))
+    ) {
       return ADMITTED
     }
     const group =
@@ -150,7 +150,10 @@ export class CodexSubagentRoster {
     turnId: string
     state: NativeChatSubagentState
   }): StructuredAgentSessionSinkAdmission {
-    if (input.threadId === this.deps.primaryThreadId()) {
+    if (
+      input.threadId === this.deps.primaryThreadId() ||
+      this.retention.hasSettled(executionIdentity(input.threadId, input.turnId))
+    ) {
       return ADMITTED
     }
     const observed = this.executions.observeTurn(input.threadId, input.turnId, input.state)
@@ -162,7 +165,10 @@ export class CodexSubagentRoster {
     child: Readonly<CodexExecutionChild>,
     execution: CodexChildExecution
   ): StructuredAgentSessionSinkAdmission {
-    if (!child.registered) {
+    if (
+      !child.registered ||
+      this.retention.hasSettled(executionIdentity(child.agentThreadId, execution.turnId))
+    ) {
       return ADMITTED
     }
     if (execution.state === 'working') {
@@ -227,13 +233,15 @@ export class CodexSubagentRoster {
   dispose(): void {
     this.unfollow()
     this.groups.clear()
+    this.retention.clear()
     this.tokensByThread.clear()
   }
 
-  private sweep(group: RosterGroup | undefined): StructuredAgentSessionSinkAdmission {
-    if (!group) {
-      return ADMITTED
-    }
+  retentionSizes(): { groups: number; settledIdentities: number } {
+    return this.retention.sizes()
+  }
+
+  private sweep(group: RosterGroup): StructuredAgentSessionSinkAdmission {
     let changed = false
     for (const [id, entry] of group.entries) {
       if (isTerminalSubagentState(entry.state)) {
@@ -268,13 +276,6 @@ export class CodexSubagentRoster {
       lastSerialized: null
     }
     this.groups.set(groupId, group)
-    while (this.groups.size > MAX_CODEX_SUBAGENT_GROUPS) {
-      const oldest = this.groups.keys().next().value
-      if (typeof oldest !== 'string' || oldest === groupId) {
-        break
-      }
-      this.groups.delete(oldest)
-    }
     return group
   }
 
@@ -307,6 +308,7 @@ export class CodexSubagentRoster {
       return
     }
     const now = this.now()
+    retainSupersededCodexExecution(group, child.agentThreadId, turnId, this.retention)
     group.executionTurns.set(child.agentThreadId, turnId)
     group.entries.set(child.agentThreadId, {
       id: child.agentThreadId,
@@ -345,6 +347,7 @@ export class CodexSubagentRoster {
       : (this.deps.sink.appendItem(group.identity, body, options), ADMITTED)
     if (!admission.accepted) {
       group.lastSerialized = null
+      this.retention.trim([group])
       return admission
     }
     const published = this.deps.sink.tryPublish
@@ -357,6 +360,7 @@ export class CodexSubagentRoster {
       // roster stays queued but never reaches the renderer.
       group.lastSerialized = null
     }
+    this.retention.trim([group])
     return published
   }
 }
diff --git a/src/main/native-chat/subagent-roster-retention.test.ts b/src/main/native-chat/subagent-roster-retention.test.ts
new file mode 100644
index 00000000000..5eaacca3568
--- /dev/null
+++ b/src/main/native-chat/subagent-roster-retention.test.ts
@@ -0,0 +1,150 @@
+import { describe, expect, it } from 'vitest'
+import type {
+  NativeChatSubagentEntry,
+  NativeChatSubagentState
+} from '../../shared/native-chat-types'
+import { SubagentRosterRetention } from './subagent-roster-retention'
+
+type Group = {
+  groupId: string
+  entries: Map<string, NativeChatSubagentEntry>
+  lastSerialized: string | null
+}
+
+function group(groupId: string, state: NativeChatSubagentState, children = 64): Group {
+  return {
+    groupId,
+    lastSerialized: 'admitted',
+    entries: new Map(
+      Array.from({ length: children }, (_, index) => {
+        const id = `${groupId}:${index}`
+        return [id, { id, label: id, state }]
+      })
+    )
+  }
+}
+
+describe('host subagent roster settled retention', () => {
+  it('shares one bound between superseded executions and evicted group identities', () => {
+    const groups = new Map<string, Group>()
+    const retention = new SubagentRosterRetention(groups, {
+      maxGroups: 1,
+      maxSettledIdentities: 2048,
+      entries: (group) => group.entries.values(),
+      identities: (roster) => roster.entries.keys()
+    })
+    const live = group('live', 'working', 1)
+    groups.set(live.groupId, live)
+    for (let index = 0; index < 2100; index++) {
+      retention.rememberSettled(`superseded-${index}`)
+    }
+    const settled = group('settled', 'completed', 1)
+    groups.set(settled.groupId, settled)
+    retention.trim([settled])
+    expect(retention.sizes()).toEqual({ groups: 1, settledIdentities: 2048 })
+    expect(retention.hasSettled('superseded-52')).toBe(false)
+    expect(retention.hasSettled('superseded-2099')).toBe(true)
+    expect(retention.hasSettled('settled:0')).toBe(true)
+    retention.clear()
+    expect(retention.sizes().settledIdentities).toBe(0)
+  })
+
+  it('bounds settled groups and recent identities while retaining every live group', () => {
+    const groups = new Map<string, Group>()
+    const retention = new SubagentRosterRetention(groups, {
+      maxGroups: 32,
+      maxSettledIdentities: 32 * 64,
+      entries: (group) => group.entries.values(),
+      identities: (roster) => roster.entries.keys()
+    })
+    for (let index = 0; index < 35; index++) {
+      const live = group(`live-${index}`, 'working')
+      groups.set(live.groupId, live)
+      retention.trim([live])
+    }
+    for (let index = 0; index < 70; index++) {
+      const settled = group(`settled-${index}`, 'completed')
+      groups.set(settled.groupId, settled)
+      retention.trim([settled])
+    }
+    expect(retention.sizes()).toEqual({ groups: 35, settledIdentities: 32 * 64 })
+    expect(retention.hasSettled('settled-0:0')).toBe(false)
+    expect(retention.hasSettled('settled-69:0')).toBe(true)
+    expect([...groups.keys()].every((id) => id.startsWith('live-'))).toBe(true)
+    for (let index = 0; index < 70; index++) {
+      const settled = group(`more-settled-${index}`, 'completed')
+      const live = groups.get(`live-${index}`)
+      if (live) {
+        for (const entry of live.entries.values()) {
+          entry.state = 'completed'
+        }
+        retention.trim([live])
+      }
+      groups.set(settled.groupId, settled)
+      retention.trim([settled])
+    }
+    expect(retention.sizes()).toEqual({ groups: 32, settledIdentities: 32 * 64 })
+  })
+
+  it('re-derives settled eligibility when a retained child runs again or its write is refused', () => {
+    const groups = new Map<string, Group>()
+    const retention = new SubagentRosterRetention(groups, {
+      maxGroups: 1,
+      maxSettledIdentities: 64,
+      entries: (group) => group.entries.values(),
+      identities: (roster) => roster.entries.keys()
+    })
+    const old = group('old', 'completed', 1)
+    groups.set(old.groupId, old)
+    retention.trim([old])
+    old.entries.set('old:0', { id: 'old:0', label: 'old', state: 'working' })
+    retention.trim([old])
+    const newGroup = group('new', 'working', 1)
+    groups.set(newGroup.groupId, newGroup)
+    retention.trim([newGroup])
+    expect(groups.has('old')).toBe(true)
+    old.entries.set('old:0', { id: 'old:0', label: 'old', state: 'completed' })
+    old.lastSerialized = null
+    retention.trim([old])
+    expect(groups.has('old')).toBe(true)
+    old.lastSerialized = 'admitted'
+    retention.trim([old])
+    expect(groups.has('old')).toBe(false)
+    expect(retention.hasSettled('old:0')).toBe(true)
+    groups.clear()
+    retention.clear()
+    expect(retention.sizes()).toEqual({ groups: 0, settledIdentities: 0 })
+  })
+})
+
+it('keeps only the accessed inherited row during a trim and re-derives it on the next event', () => {
+  const groups = new Map<string, Group>()
+  const retention = new SubagentRosterRetention(groups, {
+    maxGroups: 32,
+    maxSettledIdentities: 2048,
+    entries: (roster) => roster.entries.values(),
+    identities: (roster) => roster.entries.keys()
+  })
+  for (let index = 0; index < 32; index++) {
+    const live = group(`live-${index}`, 'working', 1)
+    groups.set(live.groupId, live)
+    retention.trim([live])
+  }
+  for (let index = 0; index < 70; index++) {
+    const inherited = group(`inherited-${index}`, 'completed', 1)
+    groups.set(inherited.groupId, inherited)
+    retention.trim([inherited], inherited.groupId)
+    expect(groups.size).toBe(33)
+    expect(groups.has(inherited.groupId)).toBe(true)
+  }
+  retention.trim([])
+  expect(groups.size).toBe(32)
+  expect(retention.hasSettled('inherited-69:0')).toBe(true)
+  const resumed = group('resumed', 'completed', 1)
+  groups.set(resumed.groupId, resumed)
+  retention.trim([resumed], resumed.groupId)
+  resumed.entries.set('resumed:0', { id: 'resumed:0', label: 'resumed', state: 'working' })
+  retention.trim([resumed])
+  expect(groups.has(resumed.groupId)).toBe(true)
+  expect(groups.size).toBe(33)
+})
diff --git a/src/main/native-chat/subagent-roster-retention.ts b/src/main/native-chat/subagent-roster-retention.ts
new file mode 100644
index 00000000000..6d4f5d865f5
--- /dev/null
+++ b/src/main/native-chat/subagent-roster-retention.ts
@@ -0,0 +1,75 @@
+import { BoundedMap } from '../../shared/bounded-map'
+import { isTerminalSubagentState } from '../../shared/native-chat-subagent-summary'
+import type { NativeChatSubagentEntry } from '../../shared/native-chat-types'
+
+type RetainedRosterGroup = {
+  groupId: string
+  lastSerialized: string | null
+}
+
+/** Bounds settled history; live children and refused final writes keep their ownership. */
+export class SubagentRosterRetention<Group extends RetainedRosterGroup> {
+  private readonly settledGroups = new Set<string>()
+  private readonly settledIdentities: BoundedMap<string, true>
+
+  constructor(
+    private readonly groups: Map<string, Group>,
+    private readonly options: {
+      maxGroups: number
+      maxSettledIdentities: number
+      entries: (group: Group) => Iterable<NativeChatSubagentEntry>
+      identities: (group: Group) => Iterable<string>
+      onEvict?: (group: Group) => void
+    }
+  ) {
+    this.settledIdentities = new BoundedMap({ maxEntries: options.maxSettledIdentities })
+  }
+
+  hasSettled(identity: string): boolean {
+    return this.settledIdentities.has(identity)
+  }
+
+  /** Superseded executions share the evicted history's single bounded budget. */
+  rememberSettled(identity: string): void {
+    this.settledIdentities.set(identity, true)
+  }
+
+  trim(changed: Iterable<Group>, retainedGroupId?: string): void {
+    for (const group of changed) {
+      if (
+        group.lastSerialized !== null &&
+        [...this.options.entries(group)].every((entry) => isTerminalSubagentState(entry.state))
+      ) {
+        this.settledGroups.add(group.groupId)
+      } else {
+        this.settledGroups.delete(group.groupId)
+      }
+    }
+    for (const groupId of this.settledGroups) {
+      if (this.groups.size <= this.options.maxGroups) {
+        break
+      }
+      if (groupId === retainedGroupId) {
+        continue
+      }
+      const group = this.groups.get(groupId)
+      if (group) {
+        for (const identity of this.options.identities(group)) {
+          this.rememberSettled(identity)
+        }
+        this.options.onEvict?.(group)
+      }
+      this.groups.delete(groupId)
+      this.settledGroups.delete(groupId)
+    }
+  }
+
+  sizes(): { groups: number; settledIdentities: number } {
+    return { groups: this.groups.size, settledIdentities: this.settledIdentities.size }
+  }
+
+  clear(): void {
+    this.settledGroups.clear()
+    this.settledIdentities.clear()
+  }
+}