perf(ui): reduce session list churn and message block invalidation

packages/ui/src/components/instance/instance-shell2.tsx

@@ -875,7 +875,6 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
       <div class="session-sidebar flex flex-col flex-1 min-h-0">
         <SessionList
           instanceId={props.instance.id}
-          sessions={allInstanceSessions()}
           threads={sessionThreads()}
           activeSessionId={activeSessionIdForInstance()}
           onSelect={handleSessionSelect}

packages/ui/src/components/message-block.tsx

@@ -1,4 +1,4 @@
-import { For, Match, Show, Switch, createEffect, createMemo, createSignal } from "solid-js"
+import { For, Match, Show, Switch, createEffect, createMemo, createSignal, untrack } from "solid-js"
 import { FoldVertical } from "lucide-solid"
 import MessageItem from "./message-item"
 import ToolCall from "./tool-call"
@@ -235,16 +235,11 @@ export default function MessageBlock(props: MessageBlockProps) {
     const index = props.messageIndex
     const lastAssistantIdx = props.lastAssistantIndex()
     const isQueued = current.role === "user" && (lastAssistantIdx === -1 || index > lastAssistantIdx)
-    const info = messageInfo()
-    const infoTime = (info?.time ?? {}) as { created?: number; updated?: number; completed?: number }
-    const infoTimestamp =
-      typeof infoTime.completed === "number"
-        ? infoTime.completed
-        : typeof infoTime.updated === "number"
-          ? infoTime.updated
-          : infoTime.created ?? 0
-    const infoError = (info as { error?: { name?: string } } | undefined)?.error
-    const infoErrorName = typeof infoError?.name === "string" ? infoError.name : ""
+
+    // Intentionally untracked: messageInfoVersion updates should not trigger
+    // a full message block rebuild; record revision is the invalidation key.
+    const info = untrack(messageInfo)
+
     const cacheSignature = [
       current.id,
       current.revision,
@@ -252,8 +247,6 @@ export default function MessageBlock(props: MessageBlockProps) {
       props.showThinking() ? 1 : 0,
       props.thinkingDefaultExpanded() ? 1 : 0,
       props.showUsageMetrics() ? 1 : 0,
-      infoTimestamp,
-      infoErrorName,
     ].join("|")
 
     const cachedBlock = sessionCache.messageBlocks.get(current.id)

packages/ui/src/components/session-list.tsx

@@ -1,5 +1,5 @@
 import { Component, For, Show, createSignal, createMemo, createEffect, JSX, onCleanup } from "solid-js"
-import type { Session, SessionStatus } from "../types/session"
+import type { SessionStatus } from "../types/session"
 import type { SessionThread } from "../stores/session-state"
 import { getSessionStatus } from "../stores/session-status"
 import { Bot, User, Copy, Trash2, Pencil, ShieldAlert, ChevronDown } from "lucide-solid"
@@ -14,6 +14,7 @@ import {
   isSessionParentExpanded,
   loading,
   renameSession,
+  sessions as sessionStateSessions,
   setActiveSessionFromList,
   toggleSessionParentExpanded,
 } from "../stores/sessions"
@@ -25,7 +26,6 @@ const log = getLogger("session")
 
 interface SessionListProps {
   instanceId: string
-  sessions: Map<string, Session>
   threads: SessionThread[]
   activeSessionId: string | null
   onSelect: (sessionId: string) => void
@@ -58,7 +58,7 @@ const SessionList: Component<SessionListProps> = (props) => {
  
 
   const selectSession = (sessionId: string) => {
-    const session = props.sessions.get(sessionId)
+    const session = sessionStateSessions().get(props.instanceId)?.get(sessionId)
     const parentId = session?.parentId ?? session?.id
     if (parentId) {
       ensureSessionParentExpanded(props.instanceId, parentId)
@@ -132,7 +132,7 @@ const SessionList: Component<SessionListProps> = (props) => {
   }
 
   const openRenameDialog = (sessionId: string) => {
-    const session = props.sessions.get(sessionId)
+    const session = sessionStateSessions().get(props.instanceId)?.get(sessionId)
     if (!session) return
     const label = session.title && session.title.trim() ? session.title : sessionId
     setRenameTarget({ id: sessionId, title: session.title ?? "", label })
@@ -167,7 +167,7 @@ const SessionList: Component<SessionListProps> = (props) => {
     expanded?: boolean
     onToggleExpand?: () => void
   }> = (rowProps) => {
-    const session = () => props.sessions.get(rowProps.sessionId)
+    const session = createMemo(() => sessionStateSessions().get(props.instanceId)?.get(rowProps.sessionId))
     if (!session()) {
       return <></>
     }
@@ -293,7 +293,7 @@ const SessionList: Component<SessionListProps> = (props) => {
     const activeId = props.activeSessionId
     if (!activeId || activeId === "info") return null
 
-    const activeSession = props.sessions.get(activeId)
+    const activeSession = sessionStateSessions().get(props.instanceId)?.get(activeId)
     if (!activeSession) return null
 
     return activeSession.parentId ?? activeSession.id

packages/ui/src/stores/session-events.ts

@@ -240,8 +240,20 @@ function handleMessageUpdate(instanceId: string, event: MessageUpdateEvent | Mes
     const messageId = typeof info.id === "string" ? info.id : undefined
     if (!sessionId || !messageId) return
 
+    const timeInfo = (info.time ?? {}) as { created?: number; updated?: number; completed?: number }
+    const nextUpdated =
+      typeof timeInfo.completed === "number" && timeInfo.completed > 0
+        ? timeInfo.completed
+        : typeof timeInfo.updated === "number" && timeInfo.updated > 0
+          ? timeInfo.updated
+          : typeof timeInfo.created === "number" && timeInfo.created > 0
+            ? timeInfo.created
+            : Date.now()
+
     withSession(instanceId, sessionId, (session) => {
-      session.time = { ...(session.time ?? {}), updated: Date.now() }
+      const currentUpdated = session.time?.updated ?? 0
+      if (nextUpdated <= currentUpdated) return false
+      session.time = { ...(session.time ?? {}), updated: nextUpdated }
     })
 
     const store = messageStoreBus.getOrCreate(instanceId)

packages/ui/src/stores/session-state.ts

@@ -390,9 +390,35 @@ function getSessionFamily(instanceId: string, parentId: string): Session[] {
   return [parent, ...children]
 }
 
+type SessionThreadCacheEntry = {
+  signature: string
+  thread: SessionThread
+}
+
+type SessionThreadCache = {
+  byParentId: Map<string, SessionThreadCacheEntry>
+}
+
+const sessionThreadCache = new Map<string, SessionThreadCache>()
+
+function getOrCreateSessionThreadCache(instanceId: string): SessionThreadCache {
+  let cache = sessionThreadCache.get(instanceId)
+  if (!cache) {
+    cache = { byParentId: new Map() }
+    sessionThreadCache.set(instanceId, cache)
+  }
+  return cache
+}
+
 function getSessionThreads(instanceId: string): SessionThread[] {
   const instanceSessions = sessions().get(instanceId)
-  if (!instanceSessions || instanceSessions.size === 0) return []
+  if (!instanceSessions || instanceSessions.size === 0) {
+    sessionThreadCache.delete(instanceId)
+    return []
+  }
+
+  const cache = getOrCreateSessionThreadCache(instanceId)
+  const seenParents = new Set<string>()
 
   const parents: Session[] = []
   const childrenByParent = new Map<string, Session[]>()
@@ -416,6 +442,8 @@ function getSessionThreads(instanceId: string): SessionThread[] {
   const threads: SessionThread[] = []
 
   for (const parent of parents) {
+    seenParents.add(parent.id)
+
     const children = childrenByParent.get(parent.id) ?? []
     if (children.length > 1) {
       children.sort((a, b) => (b.time.updated ?? 0) - (a.time.updated ?? 0))
@@ -425,7 +453,23 @@ function getSessionThreads(instanceId: string): SessionThread[] {
     const latestChild = children[0]?.time.updated ?? 0
     const latestUpdated = Math.max(parentUpdated, latestChild)
 
-    threads.push({ parent, children, latestUpdated })
+    const childIds = children.map((child) => child.id).join(",")
+    const signature = `${parentUpdated}:${latestChild}:${childIds}`
+
+    const cached = cache.byParentId.get(parent.id)
+    if (cached && cached.signature === signature) {
+      threads.push(cached.thread)
+    } else {
+      const thread: SessionThread = { parent, children, latestUpdated }
+      cache.byParentId.set(parent.id, { signature, thread })
+      threads.push(thread)
+    }
+  }
+
+  for (const parentId of Array.from(cache.byParentId.keys())) {
+    if (!seenParents.has(parentId)) {
+      cache.byParentId.delete(parentId)
+    }
   }
 
   threads.sort((a, b) => {