diff --git a/packages/ui/src/components/instance-tab.tsx b/packages/ui/src/components/instance-tab.tsx
index 24852a4a..d9681e67 100644
--- a/packages/ui/src/components/instance-tab.tsx
+++ b/packages/ui/src/components/instance-tab.tsx
@@ -1,9 +1,8 @@
-import { Component, Show, createMemo, createSignal, onCleanup } from "solid-js"
+import { Component, Show, createMemo } from "solid-js"
 import type { Instance } from "../types/instance"
 import { getInstanceSessionIndicatorStatus } from "../stores/session-status"
 import { FolderOpen, ShieldAlert, X } from "lucide-solid"
 import { useI18n } from "../lib/i18n"
-import { useConfig } from "../stores/preferences"
 
 interface InstanceTabProps {
   instance: Instance
@@ -21,17 +20,8 @@ function getPathBasename(path: string): string {
 
 const InstanceTab: Component<InstanceTabProps> = (props) => {
   const { t } = useI18n()
-  const { preferences } = useConfig()
-  const [now, setNow] = createSignal(Date.now())
 
-  if (typeof window !== "undefined") {
-    const timer = window.setInterval(() => setNow(Date.now()), 1000)
-    onCleanup(() => window.clearInterval(timer))
-  }
-
-  const aggregatedStatus = createMemo(() =>
-    getInstanceSessionIndicatorStatus(props.instance.id, now(), preferences().keepUnseenSubagentIdleStatus),
-  )
+  const aggregatedStatus = createMemo(() => getInstanceSessionIndicatorStatus(props.instance.id))
   const statusClassName = createMemo(() => {
     const status = aggregatedStatus()
     if (!status) return null
diff --git a/packages/ui/src/components/instance/instance-shell2.tsx b/packages/ui/src/components/instance/instance-shell2.tsx
index badb76ac..727504c9 100644
--- a/packages/ui/src/components/instance/instance-shell2.tsx
+++ b/packages/ui/src/components/instance/instance-shell2.tsx
@@ -44,7 +44,6 @@ import { useDrawerChrome } from "./shell/useDrawerChrome"
 import { getRetrySeconds, getSessionRetry, getSessionStatus, shouldShowSessionStatus } from "../../stores/session-status"
 import { Maximize2, ShieldAlert } from "lucide-solid"
 import type { PromptInputApi } from "../prompt-input/types"
-import { useConfig } from "../../stores/preferences"
 
 import type { LayoutMode } from "./shell/types"
 import {
@@ -91,7 +90,6 @@ interface InstanceShellProps {
 
 const InstanceShell2: Component<InstanceShellProps> = (props) => {
   const { t, locale } = useI18n()
-  const { preferences } = useConfig()
   const isRTL = () => locale() === "he"
 
   const [sessionSidebarWidth, setSessionSidebarWidth] = createSignal(DEFAULT_SESSION_SIDEBAR_WIDTH)
@@ -331,12 +329,7 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
 
     const status = getSessionStatus(props.instance.id, activeSessionId)
     const retry = getSessionRetry(props.instance.id, activeSessionId)
-    const showStatus = shouldShowSessionStatus(
-      props.instance.id,
-      activeSessionId,
-      now(),
-      preferences().keepUnseenSubagentIdleStatus,
-    )
+    const showStatus = shouldShowSessionStatus(props.instance.id, activeSessionId)
     if (!showStatus) {
       return null
     }
diff --git a/packages/ui/src/components/session-list.tsx b/packages/ui/src/components/session-list.tsx
index 6d229520..24a6e7ab 100644
--- a/packages/ui/src/components/session-list.tsx
+++ b/packages/ui/src/components/session-list.tsx
@@ -24,7 +24,6 @@ import {
 import { getGitRepoStatus, getWorktreeSlugForParentSession } from "../stores/worktrees"
 import { getLogger } from "../lib/logger"
 import { copyToClipboard } from "../lib/clipboard"
-import { useConfig } from "../stores/preferences"
 const log = getLogger("session")
 
 
@@ -48,7 +47,6 @@ function formatSessionStatus(status: SessionStatus): string {
 
 const SessionList: Component<SessionListProps> = (props) => {
   const { t } = useI18n()
-  const { preferences } = useConfig()
   const [renameTarget, setRenameTarget] = createSignal<{ id: string; title: string; label: string } | null>(null)
   const [isRenaming, setIsRenaming] = createSignal(false)
 
@@ -429,14 +427,7 @@ const SessionList: Component<SessionListProps> = (props) => {
     const needsQuestion = () => Boolean((session() as any)?.pendingQuestion)
     const needsInput = () => needsPermission() || needsQuestion()
     const statusClassName = () => (needsInput() ? "session-permission" : `session-${retry() ? "retrying" : status()}`)
-    const showStatus = () =>
-      needsInput() ||
-      shouldShowSessionStatus(
-        props.instanceId,
-        rowProps.sessionId,
-        now(),
-        preferences().keepUnseenSubagentIdleStatus,
-      )
+    const showStatus = () => needsInput() || shouldShowSessionStatus(props.instanceId, rowProps.sessionId)
     const statusText = () =>
       needsPermission()
         ? t("sessionList.status.needsPermission")
diff --git a/packages/ui/src/components/session/session-view.tsx b/packages/ui/src/components/session/session-view.tsx
index 3efbd542..0ce385cd 100644
--- a/packages/ui/src/components/session/session-view.tsx
+++ b/packages/ui/src/components/session/session-view.tsx
@@ -8,7 +8,7 @@ import PromptInput from "../prompt-input"
 import PromptAttachmentsBar from "../prompt-input/PromptAttachmentsBar"
 import { getAttachments, removeAttachment } from "../../stores/attachments"
 import { instances } from "../../stores/instances"
-import { loadMessages, sendMessage, forkSession, renameSession, isSessionMessagesLoading, markSessionIdleSeen, setActiveParentSession, setActiveSession, runShellCommand, abortSession } from "../../stores/sessions"
+import { loadMessages, sendMessage, forkSession, renameSession, isSessionMessagesLoading, markViewedSessionIdleSeen, setActiveParentSession, setActiveSession, runShellCommand, abortSession } from "../../stores/sessions"
 import { IDLE_STATUS_VISIBILITY_MS, isSessionBusy as getSessionBusyStatus } from "../../stores/session-status"
 import { deleteMessage } from "../../stores/session-actions"
 import { showAlertDialog } from "../../stores/alerts"
@@ -17,6 +17,7 @@ import { requestData } from "../../lib/opencode-api"
 import { useI18n } from "../../lib/i18n"
 import type { PromptInputApi, PromptInsertMode } from "../prompt-input/types"
 import { clearConversationPlaybackForSession } from "../../stores/conversation-speech"
+import { useConfig } from "../../stores/preferences"
 
 const log = getLogger("session")
 
@@ -41,6 +42,7 @@ interface SessionViewProps {
 
 export const SessionView: Component<SessionViewProps> = (props) => {
   const { t } = useI18n()
+  const { preferences } = useConfig()
   const session = () => props.activeSessions.get(props.sessionId)
   const messagesLoading = createMemo(() => isSessionMessagesLoading(props.instanceId, props.sessionId))
   const messageStore = createMemo(() => messageStoreBus.getOrCreate(props.instanceId))
@@ -80,6 +82,26 @@ export const SessionView: Component<SessionViewProps> = (props) => {
       requestAnimationFrame(() => scrollToBottomHandle?.())
     })
   }
+
+  function getSeenIdleSignature(currentSession: Session, keepUnseenSubagentIdleStatus: boolean): string {
+    const ids: string[] = []
+
+    if (currentSession.status === "idle" && typeof currentSession.idleSince === "number") {
+      ids.push(`${currentSession.id}:${currentSession.idleSince}`)
+    }
+
+    if (currentSession.parentId === null && !keepUnseenSubagentIdleStatus) {
+      for (const child of props.activeSessions.values()) {
+        if (child.parentId !== currentSession.id) continue
+        if (child.status !== "idle") continue
+        if (typeof child.idleSince !== "number") continue
+        ids.push(`${child.id}:${child.idleSince}`)
+      }
+    }
+
+    return ids.sort().join("|")
+  }
+
   createEffect(
     on(
       () => props.isActive,
@@ -95,16 +117,17 @@ export const SessionView: Component<SessionViewProps> = (props) => {
   createEffect(() => {
     const currentSession = session()
     if (!props.isActive || !currentSession) return
-    if (currentSession.status !== "idle") return
-    if (typeof currentSession.idleSince !== "number") return
 
-    const idleSince = currentSession.idleSince
+    const keepUnseenSubagentIdleStatus = preferences().keepUnseenSubagentIdleStatus
+    const seenIdleSignature = getSeenIdleSignature(currentSession, keepUnseenSubagentIdleStatus)
+    if (!seenIdleSignature) return
+
     const timeout = window.setTimeout(() => {
       const latestSession = session()
       if (!props.isActive || !latestSession) return
-      if (latestSession.status !== "idle") return
-      if (latestSession.idleSince !== idleSince) return
-      markSessionIdleSeen(props.instanceId, latestSession.id)
+      const latestKeepUnseenSubagentIdleStatus = preferences().keepUnseenSubagentIdleStatus
+      if (getSeenIdleSignature(latestSession, latestKeepUnseenSubagentIdleStatus) !== seenIdleSignature) return
+      markViewedSessionIdleSeen(props.instanceId, latestSession.id, latestKeepUnseenSubagentIdleStatus)
     }, IDLE_STATUS_VISIBILITY_MS)
 
     onCleanup(() => window.clearTimeout(timeout))
diff --git a/packages/ui/src/stores/session-state.ts b/packages/ui/src/stores/session-state.ts
index d2292313..f5e82cbd 100644
--- a/packages/ui/src/stores/session-state.ts
+++ b/packages/ui/src/stores/session-state.ts
@@ -322,6 +322,44 @@ function markSessionIdleSeen(instanceId: string, sessionId: string): void {
   })
 }
 
+function markViewedSessionIdleSeen(
+  instanceId: string,
+  sessionId: string,
+  keepUnseenSubagentIdleStatus: boolean,
+): void {
+  setSessions((prev) => {
+    const instanceSessions = prev.get(instanceId)
+    if (!instanceSessions) return prev
+
+    const viewedSession = instanceSessions.get(sessionId)
+    if (!viewedSession) return prev
+
+    const idsToClear = new Set<string>([sessionId])
+    if (viewedSession.parentId === null && !keepUnseenSubagentIdleStatus) {
+      for (const session of instanceSessions.values()) {
+        if (session.parentId === sessionId) idsToClear.add(session.id)
+      }
+    }
+
+    let changed = false
+    const updatedSessions = new Map(instanceSessions)
+    for (const id of idsToClear) {
+      const session = updatedSessions.get(id)
+      if (!session) continue
+      if (session.status !== "idle") continue
+      if (typeof session.idleSince !== "number") continue
+      updatedSessions.set(id, { ...session, idleSince: null })
+      changed = true
+    }
+
+    if (!changed) return prev
+
+    const next = new Map(prev)
+    next.set(instanceId, updatedSessions)
+    return next
+  })
+}
+
 function setActiveSession(instanceId: string, sessionId: string): void {
   setActiveSessionId((prev) => {
     const next = new Map(prev)
@@ -745,6 +783,7 @@ export {
   setSessionPendingPermission,
   setSessionPendingQuestion,
   markSessionIdleSeen,
+  markViewedSessionIdleSeen,
   setSessionStatus,
   setActiveSession,
  
diff --git a/packages/ui/src/stores/session-status.test.ts b/packages/ui/src/stores/session-status.test.ts
index 8fdcd1f2..29d7329b 100644
--- a/packages/ui/src/stores/session-status.test.ts
+++ b/packages/ui/src/stores/session-status.test.ts
@@ -30,40 +30,34 @@ describe("idle status visibility", () => {
     const idleSince = getIdleSinceForStatusTransition("working", "idle", null, 1_000)
 
     assert.equal(idleSince, 1_000)
-    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: null }, 1_000), true)
-    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: null }, 1_000 + IDLE_STATUS_VISIBILITY_MS), true)
+    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: null }), true)
+    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: null }), true)
   })
 
-  it("auto-hides subagent idle after the transient delay by default", () => {
+  it("keeps subagent idle visible until the parent or child session is seen", () => {
     const idleSince = getIdleSinceForStatusTransition("working", "idle", null, 1_000)
 
-    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: "parent" }, 1_000), true)
-    assert.equal(
-      shouldShowIdleStatus({ status: "idle", idleSince, parentId: "parent" }, 1_000 + IDLE_STATUS_VISIBILITY_MS),
-      false,
-    )
+    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: "parent" }), true)
+    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: "parent" }), true)
   })
 
-  it("can keep subagent idle visible until viewed", () => {
+  it("does not use the keep-unseen setting to age out visible idle markers", () => {
     const idleSince = getIdleSinceForStatusTransition("working", "idle", null, 1_000)
 
-    assert.equal(
-      shouldShowIdleStatus({ status: "idle", idleSince, parentId: "parent" }, 1_000 + IDLE_STATUS_VISIBILITY_MS, true),
-      true,
-    )
+    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: "parent" }), true)
   })
 
   it("does not show idle for sessions that started idle", () => {
     const idleSince = getIdleSinceForStatusTransition(undefined, "idle", null, 1_000)
 
     assert.equal(idleSince, null)
-    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: null }, 1_000), false)
+    assert.equal(shouldShowIdleStatus({ status: "idle", idleSince, parentId: null }), false)
   })
 
   it("clears idle visibility when work resumes", () => {
     const idleSince = getIdleSinceForStatusTransition("idle", "working", 1_000, 2_000)
 
     assert.equal(idleSince, null)
-    assert.equal(shouldShowIdleStatus({ status: "working", idleSince, parentId: null }, 2_000), false)
+    assert.equal(shouldShowIdleStatus({ status: "working", idleSince, parentId: null }), false)
   })
 })
diff --git a/packages/ui/src/stores/session-status.ts b/packages/ui/src/stores/session-status.ts
index ab557cdc..503b7fde 100644
--- a/packages/ui/src/stores/session-status.ts
+++ b/packages/ui/src/stores/session-status.ts
@@ -39,8 +39,6 @@ export function getSessionRetry(instanceId: string, sessionId: string): SessionR
 
 export function shouldShowIdleStatus(
   session: Pick<Session, "status" | "idleSince" | "parentId"> | null | undefined,
-  now = Date.now(),
-  keepUnseenSubagentIdleStatus = false,
 ): boolean {
   if (!session || session.status !== "idle") {
     return false
@@ -50,18 +48,12 @@ export function shouldShowIdleStatus(
     return false
   }
 
-  if (session.parentId && !keepUnseenSubagentIdleStatus) {
-    return now - session.idleSince < IDLE_STATUS_VISIBILITY_MS
-  }
-
   return true
 }
 
 export function shouldShowSessionStatus(
   instanceId: string,
   sessionId: string,
-  now = Date.now(),
-  keepUnseenSubagentIdleStatus = false,
 ): boolean {
   const session = getSession(instanceId, sessionId)
   if (!session) {
@@ -72,7 +64,7 @@ export function shouldShowSessionStatus(
     return true
   }
 
-  return session.status !== "idle" || shouldShowIdleStatus(session, now, keepUnseenSubagentIdleStatus)
+  return session.status !== "idle" || shouldShowIdleStatus(session)
 }
 
 export function getRetrySeconds(next: number, now = Date.now()): number {
@@ -83,8 +75,6 @@ export type InstanceSessionIndicatorStatus = "permission" | SessionStatus
 
 export function getInstanceSessionIndicatorStatus(
   instanceId: string,
-  now = Date.now(),
-  keepUnseenSubagentIdleStatus = false,
 ): InstanceSessionIndicatorStatus | null {
   const aggregated = getInstanceSessionIndicatorStatusCached(instanceId)
   if (aggregated !== "idle") {
@@ -97,7 +87,7 @@ export function getInstanceSessionIndicatorStatus(
   }
 
   for (const session of instanceSessions.values()) {
-    if (shouldShowIdleStatus(session, now, keepUnseenSubagentIdleStatus)) {
+    if (shouldShowIdleStatus(session)) {
       return "idle"
     }
   }
diff --git a/packages/ui/src/stores/sessions.ts b/packages/ui/src/stores/sessions.ts
index fe138047..96ac43e6 100644
--- a/packages/ui/src/stores/sessions.ts
+++ b/packages/ui/src/stores/sessions.ts
@@ -25,6 +25,7 @@ import {
   isSessionParentExpanded,
   loading,
   markSessionIdleSeen,
+  markViewedSessionIdleSeen,
   providers,
   sessionInfoByInstance,
   sessions,
@@ -126,6 +127,7 @@ export {
   loadMessages,
   loading,
   markSessionIdleSeen,
+  markViewedSessionIdleSeen,
   providers,
   sendMessage,
   sessionInfoByInstance,