diff --git a/packages/ui/src/components/message-stream-v2.tsx b/packages/ui/src/components/message-stream-v2.tsx
new file mode 100644
index 00000000..44e8fd26
--- /dev/null
+++ b/packages/ui/src/components/message-stream-v2.tsx
@@ -0,0 +1,422 @@
+import { For, Show, createMemo, createSignal, createEffect, onCleanup } from "solid-js"
+import MessageItem from "./message-item"
+import ToolCall from "./tool-call"
+import Kbd from "./kbd"
+import type { Message, MessageInfo, ClientPart } from "../types/message"
+import { computeDisplayParts } from "../stores/session-messages"
+import { getSessionInfo } from "../stores/sessions"
+import { showCommandPalette } from "../stores/command-palette"
+import { messageStoreBus } from "../stores/message-v2/bus"
+import type { MessageRecord } from "../stores/message-v2/types"
+import { useConfig } from "../stores/preferences"
+import { getScrollCache, setScrollCache } from "../lib/scroll-cache"
+import { sseManager } from "../lib/sse-manager"
+import { formatTokenTotal } from "../lib/formatters"
+
+const SCROLL_SCOPE = "session"
+const TOOL_ICON = "🔧"
+const codeNomadLogo = new URL("../images/CodeNomad-Icon.png", import.meta.url).href
+
+function formatTokens(tokens: number): string {
+  return formatTokenTotal(tokens)
+}
+
+
+interface MessageStreamV2Props {
+  instanceId: string
+  sessionId: string
+  loading?: boolean
+  onRevert?: (messageId: string) => void
+  onFork?: (messageId?: string) => void
+}
+
+interface MessageDisplayItem {
+  type: "message"
+  message: Message
+  combinedParts: ClientPart[]
+  messageInfo?: MessageInfo
+  isQueued: boolean
+}
+
+interface ToolDisplayItem {
+  type: "tool"
+  key: string
+  toolPart: ToolCallPart
+  messageInfo?: MessageInfo
+  messageId: string
+  messageVersion: number
+  partVersion: number
+}
+
+type DisplayItem = MessageDisplayItem | ToolDisplayItem
+
+type ToolCallPart = Extract<ClientPart, { type: "tool" }>
+
+function isToolPart(part: ClientPart): part is ToolCallPart {
+  return part.type === "tool"
+}
+
+function recordToMessage(record: MessageRecord): Message {
+  const parts = record.partIds
+    .map((partId) => record.parts[partId]?.data)
+    .filter((part): part is ClientPart => Boolean(part))
+  return {
+    id: record.id,
+    sessionId: record.sessionId,
+    type: record.role,
+    parts,
+    timestamp: record.createdAt,
+    status: record.status,
+    version: record.revision,
+  }
+}
+
+function hasRenderableContent(message: Message, combinedParts: ClientPart[], info?: MessageInfo): boolean {
+  if (message.type !== "assistant" && message.type !== "user") {
+    return false
+  }
+  if (message.type !== "assistant" || combinedParts.length > 0) {
+    return true
+  }
+  if (info && info.role === "assistant" && info.error) {
+    return true
+  }
+  return message.status === "error"
+}
+
+export default function MessageStreamV2(props: MessageStreamV2Props) {
+  const { preferences } = useConfig()
+  const store = createMemo(() => messageStoreBus.getOrCreate(props.instanceId))
+  const messageIds = createMemo(() => store().getSessionMessageIds(props.sessionId))
+  const messageRecords = createMemo(() =>
+    messageIds()
+      .map((id) => store().getMessage(id))
+      .filter((record): record is MessageRecord => Boolean(record)),
+  )
+
+  const usageSnapshot = createMemo(() => store().getSessionUsage(props.sessionId))
+  const sessionInfo = createMemo(() =>
+    getSessionInfo(props.instanceId, props.sessionId) ?? {
+      cost: 0,
+      contextWindow: 0,
+      isSubscriptionModel: false,
+      inputTokens: 0,
+      outputTokens: 0,
+      reasoningTokens: 0,
+      actualUsageTokens: 0,
+      modelOutputLimit: 0,
+      contextAvailableTokens: null,
+    },
+  )
+  const tokenStats = createMemo(() => {
+    const usage = usageSnapshot()
+    const info = sessionInfo()
+    return {
+      used: usage?.actualUsageTokens ?? info.actualUsageTokens ?? 0,
+      avail: info.contextAvailableTokens,
+    }
+  })
+
+  const connectionStatus = () => sseManager.getStatus(props.instanceId)
+  const handleCommandPaletteClick = () => {
+    showCommandPalette(props.instanceId)
+  }
+
+  const messageInfoMap = createMemo(() => {
+    const map = new Map<string, MessageInfo>()
+    messageIds().forEach((id) => {
+      const info = store().getMessageInfo(id)
+      if (info) {
+        map.set(id, info)
+      }
+    })
+    return map
+  })
+  const revertTarget = createMemo(() => store().getSessionRevert(props.sessionId))
+
+  const displayItems = createMemo<DisplayItem[]>(() => {
+    const infoMap = messageInfoMap()
+    const showThinking = preferences().showThinkingBlocks
+    const revert = revertTarget()
+    const items: DisplayItem[] = []
+
+    const records = messageRecords()
+    let lastAssistantIndex = -1
+    for (let i = records.length - 1; i >= 0; i--) {
+      if (records[i].role === "assistant") {
+        lastAssistantIndex = i
+        break
+      }
+    }
+
+    for (let index = 0; index < records.length; index++) {
+      const record = records[index]
+      if (revert?.messageID && record.id === revert.messageID) {
+        break
+      }
+
+      const baseMessage = recordToMessage(record)
+      const displayParts = computeDisplayParts(baseMessage, showThinking)
+      baseMessage.displayParts = displayParts
+      const combinedParts = displayParts.combined
+      const messageInfo = infoMap.get(record.id)
+      const isQueued =
+        baseMessage.type === "user" && (lastAssistantIndex === -1 || index > lastAssistantIndex)
+
+      if (hasRenderableContent(baseMessage, combinedParts, messageInfo)) {
+        items.push({
+          type: "message",
+          message: baseMessage,
+          combinedParts,
+          messageInfo,
+          isQueued,
+        })
+      }
+
+      const toolParts: ToolCallPart[] = displayParts.tool.filter(isToolPart)
+      toolParts.forEach((toolPart, toolIndex) => {
+        const partVersion = typeof toolPart.version === "number" ? toolPart.version : 0
+        const messageVersion = typeof baseMessage.version === "number" ? baseMessage.version : 0
+        const key = toolPart.id || `${record.id}-tool-${toolIndex}`
+        items.push({
+          type: "tool",
+          key,
+          toolPart,
+          messageInfo,
+          messageId: record.id,
+          messageVersion,
+          partVersion,
+        })
+      })
+    }
+
+    return items
+  })
+
+  const changeToken = createMemo(() => {
+    const entries = displayItems()
+    return entries
+      .map((item) => {
+        if (item.type === "message") {
+          return `${item.message.id}:${item.message.version}:${item.combinedParts.length}`
+        }
+        const status = item.toolPart.state?.status || "unknown"
+        return `tool:${item.key}:${item.partVersion}:${status}`
+      })
+      .join("|")
+  })
+
+  const [autoScroll, setAutoScroll] = createSignal(true)
+  const [showScrollButton, setShowScrollButton] = createSignal(false)
+  let containerRef: HTMLDivElement | undefined
+
+  function isNearBottom(element: HTMLDivElement, offset = 48) {
+    const { scrollTop, scrollHeight, clientHeight } = element
+    return scrollHeight - (scrollTop + clientHeight) <= offset
+  }
+
+  function scrollToBottom(immediate = false) {
+    if (!containerRef) return
+    const behavior = immediate ? "auto" : "smooth"
+    containerRef.scrollTo({ top: containerRef.scrollHeight, behavior })
+    setAutoScroll(true)
+    persistScrollState()
+  }
+
+  function persistScrollState() {
+    if (!containerRef) return
+    setScrollCache(
+      { instanceId: props.instanceId, sessionId: props.sessionId, scope: SCROLL_SCOPE },
+      {
+        scrollTop: containerRef.scrollTop,
+        atBottom: isNearBottom(containerRef),
+      },
+    )
+  }
+
+  function handleScroll(event: Event) {
+    if (!containerRef) return
+    const atBottom = isNearBottom(containerRef)
+    setShowScrollButton(!atBottom)
+    if (event.isTrusted) {
+      setAutoScroll(atBottom)
+    }
+    persistScrollState()
+  }
+
+  createEffect(() => {
+    const scrollSnapshot = getScrollCache({ instanceId: props.instanceId, sessionId: props.sessionId, scope: SCROLL_SCOPE })
+    requestAnimationFrame(() => {
+      if (!containerRef) return
+      if (scrollSnapshot) {
+        const maxScrollTop = Math.max(containerRef.scrollHeight - containerRef.clientHeight, 0)
+        containerRef.scrollTop = Math.min(scrollSnapshot.scrollTop, maxScrollTop)
+        setAutoScroll(scrollSnapshot.atBottom)
+        setShowScrollButton(!scrollSnapshot.atBottom)
+      } else {
+        scrollToBottom(true)
+      }
+    })
+  })
+
+  let previousToken: string | undefined
+  createEffect(() => {
+    const token = changeToken()
+    if (!token || token === previousToken) {
+      return
+    }
+    previousToken = token
+    if (autoScroll()) {
+      requestAnimationFrame(() => scrollToBottom(true))
+    }
+  })
+
+  createEffect(() => {
+    if (displayItems().length === 0) {
+      setShowScrollButton(false)
+      setAutoScroll(true)
+    }
+  })
+
+  onCleanup(() => {
+    persistScrollState()
+  })
+
+  return (
+    <div class="message-stream-container">
+      <div class="connection-status">
+        <div class="connection-status-text connection-status-info flex flex-wrap items-center gap-2 text-sm font-medium">
+          <div class="inline-flex items-center gap-1 rounded-full border border-base px-2 py-0.5 text-xs text-primary">
+            <span class="uppercase text-[10px] tracking-wide text-primary/70">Used</span>
+            <span class="font-semibold text-primary">{formatTokens(tokenStats().used)}</span>
+          </div>
+          <div class="inline-flex items-center gap-1 rounded-full border border-base px-2 py-0.5 text-xs text-primary">
+            <span class="uppercase text-[10px] tracking-wide text-primary/70">Avail</span>
+            <span class="font-semibold text-primary">
+              {sessionInfo().contextAvailableTokens !== null ? formatTokens(sessionInfo().contextAvailableTokens ?? 0) : "--"}
+            </span>
+          </div>
+        </div>
+
+        <div class="connection-status-text connection-status-shortcut">
+          <div class="connection-status-shortcut-action">
+            <button type="button" class="connection-status-button" onClick={handleCommandPaletteClick} aria-label="Open command palette">
+              Command Palette
+            </button>
+            <span class="connection-status-shortcut-hint">
+              <Kbd shortcut="cmd+shift+p" />
+            </span>
+          </div>
+        </div>
+        <div class="connection-status-meta flex items-center justify-end gap-3">
+          <Show when={connectionStatus() === "connected"}>
+            <span class="status-indicator connected">
+              <span class="status-dot" />
+              Connected
+            </span>
+          </Show>
+          <Show when={connectionStatus() === "connecting"}>
+            <span class="status-indicator connecting">
+              <span class="status-dot" />
+              Connecting...
+            </span>
+          </Show>
+          <Show when={connectionStatus() === "error" || connectionStatus() === "disconnected"}>
+            <span class="status-indicator disconnected">
+              <span class="status-dot" />
+              Disconnected
+            </span>
+          </Show>
+        </div>
+      </div>
+
+      <div
+        class="message-stream"
+        ref={(element) => {
+          containerRef = element || undefined
+        }}
+        onScroll={handleScroll}
+      >
+        <Show when={!props.loading && displayItems().length === 0}>
+          <div class="empty-state">
+            <div class="empty-state-content">
+              <div class="flex flex-col items-center gap-3 mb-6">
+                <img src={codeNomadLogo} alt="CodeNomad logo" class="h-48 w-auto" loading="lazy" />
+                <h1 class="text-3xl font-semibold text-primary">CodeNomad</h1>
+              </div>
+              <h3>Start a conversation</h3>
+              <p>Type a message below or open the Command Palette:</p>
+              <ul>
+                <li>
+                  <span>Command Palette</span>
+                  <Kbd shortcut="cmd+shift+p" class="ml-2" />
+                </li>
+                <li>Ask about your codebase</li>
+                <li>
+                  Attach files with <code>@</code>
+                </li>
+              </ul>
+            </div>
+          </div>
+        </Show>
+
+        <Show when={props.loading}>
+          <div class="loading-state">
+            <div class="spinner" />
+            <p>Loading messages...</p>
+          </div>
+        </Show>
+
+        <For each={displayItems()}>
+          {(item) => {
+            if (item.type === "message") {
+              return (
+                <MessageItem
+                  message={item.message}
+                  messageInfo={item.messageInfo}
+                  parts={item.combinedParts}
+                  instanceId={props.instanceId}
+                  sessionId={props.sessionId}
+                  isQueued={item.isQueued}
+                  onRevert={props.onRevert}
+                  onFork={props.onFork}
+                />
+              )
+            }
+
+            return (
+              <div class="tool-call-message" data-key={item.key}>
+                <div class="tool-call-header-label">
+                  <div class="tool-call-header-meta">
+                    <span class="tool-call-icon">{TOOL_ICON}</span>
+                    <span>Tool Call</span>
+                    <span class="tool-name">{item.toolPart.tool || "unknown"}</span>
+                  </div>
+                </div>
+                <ToolCall
+                  toolCall={item.toolPart}
+                  toolCallId={item.key}
+                  messageId={item.messageId}
+                  messageVersion={item.messageVersion}
+                  partVersion={item.partVersion}
+                  instanceId={props.instanceId}
+                  sessionId={props.sessionId}
+                />
+              </div>
+            )
+          }}
+        </For>
+      </div>
+
+      <Show when={showScrollButton()}>
+        <div class="message-scroll-button-wrapper">
+          <button type="button" class="message-scroll-button" onClick={() => scrollToBottom()} aria-label="Scroll to latest message">
+            <span class="message-scroll-icon" aria-hidden="true">
+              ↓
+            </span>
+          </button>
+        </div>
+      </Show>
+    </div>
+  )
+}
diff --git a/packages/ui/src/components/session/session-view.tsx b/packages/ui/src/components/session/session-view.tsx
index 04d35b54..dd269be0 100644
--- a/packages/ui/src/components/session/session-view.tsx
+++ b/packages/ui/src/components/session/session-view.tsx
@@ -2,12 +2,17 @@ import { Show, createMemo, createEffect, onCleanup, type Component } from "solid
 import type { Session } from "../../types/session"
 import type { Attachment } from "../../types/attachment"
 import type { ClientPart } from "../../types/message"
-import MessageStream from "../message-stream"
+import MessageStreamV2 from "../message-stream-v2"
+import { messageStoreBus } from "../../stores/message-v2/bus"
 import PromptInput from "../prompt-input"
 import { instances } from "../../stores/instances"
 import { loadMessages, sendMessage, forkSession, isSessionMessagesLoading, setActiveParentSession, setActiveSession, runShellCommand } from "../../stores/sessions"
 import { showAlertDialog } from "../../stores/alerts"
 
+function isTextPart(part: ClientPart): part is ClientPart & { type: "text"; text: string } {
+  return part?.type === "text" && typeof (part as any).text === "string"
+}
+
 interface SessionViewProps {
   sessionId: string
   activeSessions: Map<string, Session>
@@ -19,6 +24,7 @@ interface SessionViewProps {
 export const SessionView: Component<SessionViewProps> = (props) => {
   const session = () => props.activeSessions.get(props.sessionId)
   const messagesLoading = createMemo(() => isSessionMessagesLoading(props.instanceId, props.sessionId))
+  const messageStore = createMemo(() => messageStoreBus.getOrCreate(props.instanceId))
 
   createEffect(() => {
     const currentSession = session()
@@ -36,6 +42,17 @@ export const SessionView: Component<SessionViewProps> = (props) => {
   }
 
   function getUserMessageText(messageId: string): string | null {
+    const normalizedMessage = messageStore().getMessage(messageId)
+    if (normalizedMessage && normalizedMessage.role === "user") {
+      const parts = normalizedMessage.partIds
+        .map((partId) => normalizedMessage.parts[partId]?.data)
+        .filter((part): part is ClientPart => Boolean(part))
+      const textParts = parts.filter(isTextPart)
+      if (textParts.length > 0) {
+        return textParts.map((part) => part.text).join("\n")
+      }
+    }
+
     const currentSession = session()
     if (!currentSession) return null
 
@@ -45,7 +62,7 @@ export const SessionView: Component<SessionViewProps> = (props) => {
       return null
     }
 
-    const textParts = targetMessage.parts.filter((p): p is ClientPart & { type: "text"; text: string } => p.type === "text")
+    const textParts = targetMessage.parts.filter(isTextPart)
     if (textParts.length === 0) {
       return null
     }
@@ -129,12 +146,9 @@ export const SessionView: Component<SessionViewProps> = (props) => {
     >
       {(s) => (
         <div class="session-view">
-          <MessageStream
+          <MessageStreamV2
             instanceId={props.instanceId}
             sessionId={s().id}
-            messages={s().messages || []}
-            messagesInfo={s().messagesInfo}
-            revert={s().revert}
             loading={messagesLoading()}
             onRevert={handleRevert}
             onFork={handleFork}
diff --git a/packages/ui/src/components/tool-call.tsx b/packages/ui/src/components/tool-call.tsx
index 5c4f996f..5a8a01c0 100644
--- a/packages/ui/src/components/tool-call.tsx
+++ b/packages/ui/src/components/tool-call.tsx
@@ -1,5 +1,6 @@
 import { createSignal, Show, For, createEffect, createMemo, onCleanup } from "solid-js"
 import { isToolCallExpanded, toggleToolCallExpanded, setToolCallExpanded } from "../stores/tool-call-state"
+import { messageStoreBus } from "../stores/message-v2/bus"
 import { Markdown } from "./markdown"
 import { ToolCallDiffViewer } from "./diff-viewer"
 import { useTheme } from "../lib/theme"
@@ -346,7 +347,15 @@ export default function ToolCall(props: ToolCallProps) {
   const { preferences, setDiffViewMode } = useConfig()
   const { isDark } = useTheme()
   const toolCallId = () => props.toolCallId || props.toolCall?.id || ""
-  const pendingPermission = createMemo(() => props.toolCall.pendingPermission)
+  const store = createMemo(() => messageStoreBus.getOrCreate(props.instanceId))
+  const permissionState = createMemo(() => store().getPermissionState(props.messageId, toolCallId() || props.toolCall?.id))
+  const pendingPermission = createMemo(() => {
+    const state = permissionState()
+    if (state) {
+      return { permission: state.entry.permission, active: state.active }
+    }
+    return props.toolCall.pendingPermission
+  })
   const expanded = () => (pendingPermission() ? true : isToolCallExpanded(toolCallId()))
   const toolOutputDefaultExpanded = createMemo(() => (preferences().toolOutputExpansion || "expanded") === "expanded")
   const diagnosticsDefaultExpanded = createMemo(() => (preferences().diagnosticsExpansion || "expanded") === "expanded")
diff --git a/packages/ui/src/lib/global-cache.ts b/packages/ui/src/lib/global-cache.ts
new file mode 100644
index 00000000..2c7b941b
--- /dev/null
+++ b/packages/ui/src/lib/global-cache.ts
@@ -0,0 +1,97 @@
+interface CacheLocation {
+  instanceId?: string
+  sessionId?: string
+  scope?: string
+}
+
+const GLOBAL_KEY = "GLOBAL"
+
+type CacheScope = Map<string, unknown>
+type ScopeCollection = Map<string, CacheScope>
+type SessionMap = Map<string, ScopeCollection>
+const cacheRoot = new Map<string, SessionMap>()
+
+function resolveKey(value?: string) {
+  return value && value.length > 0 ? value : GLOBAL_KEY
+}
+
+function resolveCacheScope(location: CacheLocation, createIfMissing: boolean): CacheScope | undefined {
+  const instanceKey = resolveKey(location.instanceId)
+  const sessionKey = resolveKey(location.sessionId)
+  const scopeKey = resolveKey(location.scope)
+
+  let sessionMap = cacheRoot.get(instanceKey)
+  if (!sessionMap) {
+    if (!createIfMissing) return undefined
+    sessionMap = new Map()
+    cacheRoot.set(instanceKey, sessionMap)
+  }
+
+  let scopeCollection = sessionMap.get(sessionKey)
+  if (!scopeCollection) {
+    if (!createIfMissing) return undefined
+    scopeCollection = new Map()
+    sessionMap.set(sessionKey, scopeCollection)
+  }
+
+  let cacheScope = scopeCollection.get(scopeKey)
+  if (!cacheScope) {
+    if (!createIfMissing) return undefined
+    cacheScope = new Map()
+    scopeCollection.set(scopeKey, cacheScope)
+  }
+
+  return cacheScope
+}
+
+export function setGlobalCacheValue(location: CacheLocation, key: string, value: unknown): void {
+  const cacheScope = resolveCacheScope(location, true)
+  cacheScope?.set(key, value)
+}
+
+export function getGlobalCacheValue<T = unknown>(location: CacheLocation, key: string): T | undefined {
+  const cacheScope = resolveCacheScope(location, false)
+  return (cacheScope?.get(key) as T | undefined) ?? undefined
+}
+
+export function deleteGlobalCacheValue(location: CacheLocation, key: string): void {
+  const cacheScope = resolveCacheScope(location, false)
+  cacheScope?.delete(key)
+}
+
+export function clearGlobalCacheScope(location: CacheLocation): void {
+  const instanceKey = resolveKey(location.instanceId)
+  const sessionKey = resolveKey(location.sessionId)
+  const scopeKey = resolveKey(location.scope)
+  const sessionMap = cacheRoot.get(instanceKey)
+  if (!sessionMap) return
+  const scopeCollection = sessionMap.get(sessionKey)
+  if (!scopeCollection) return
+  scopeCollection.delete(scopeKey)
+  if (scopeCollection.size === 0) {
+    sessionMap.delete(sessionKey)
+  }
+  if (sessionMap.size === 0) {
+    cacheRoot.delete(instanceKey)
+  }
+}
+
+export function clearGlobalCacheSession(instanceId?: string, sessionId?: string): void {
+  const instanceKey = resolveKey(instanceId)
+  const sessionKey = resolveKey(sessionId)
+  const sessionMap = cacheRoot.get(instanceKey)
+  if (!sessionMap) return
+  sessionMap.delete(sessionKey)
+  if (sessionMap.size === 0) {
+    cacheRoot.delete(instanceKey)
+  }
+}
+
+export function clearGlobalCacheInstance(instanceId?: string): void {
+  const instanceKey = resolveKey(instanceId)
+  cacheRoot.delete(instanceKey)
+}
+
+export function clearAllGlobalCache(): void {
+  cacheRoot.clear()
+}
diff --git a/packages/ui/src/lib/hooks/use-commands.ts b/packages/ui/src/lib/hooks/use-commands.ts
index f413081c..1794af61 100644
--- a/packages/ui/src/lib/hooks/use-commands.ts
+++ b/packages/ui/src/lib/hooks/use-commands.ts
@@ -3,6 +3,7 @@ import type { Accessor } from "solid-js"
 import type { Preferences, ExpansionPreference } from "../../stores/preferences"
 import { createCommandRegistry, type Command } from "../commands"
 import { instances, activeInstanceId, setActiveInstanceId } from "../../stores/instances"
+import type { ClientPart, MessageInfo } from "../../types/message"
 import {
   activeParentSessionId,
   activeSessionId as activeSessionMap,
@@ -13,6 +14,8 @@ import {
 import { setSessionCompactionState } from "../../stores/session-compaction"
 import { showAlertDialog } from "../../stores/alerts"
 import type { Instance } from "../../types/instance"
+import type { MessageRecord } from "../../stores/message-v2/types"
+import { messageStoreBus } from "../../stores/message-v2/bus"
 
 export interface UseCommandsOptions {
   preferences: Accessor<Preferences>
@@ -29,6 +32,18 @@ export interface UseCommandsOptions {
   getActiveSessionIdForInstance: () => string | null
 }
 
+function extractUserTextFromRecord(record?: MessageRecord): string | null {
+  if (!record) return null
+  const parts = record.partIds
+    .map((partId) => record.parts[partId]?.data)
+    .filter((part): part is ClientPart => Boolean(part))
+  const textParts = parts.filter((part): part is ClientPart & { type: "text"; text: string } => part.type === "text" && typeof (part as any).text === "string")
+  if (textParts.length === 0) {
+    return null
+  }
+  return textParts.map((part) => (part as any).text as string).join("\n")
+}
+
 export function useCommands(options: UseCommandsOptions) {
   const commandRegistry = createCommandRegistry()
   const [commands, setCommands] = createSignal<Command[]>([])
@@ -232,34 +247,56 @@ export function useCommands(options: UseCommandsOptions) {
         const session = sessions.find((s) => s.id === sessionId)
         if (!session) return
 
-        let after = 0
-        const revert = session.revert
+        const store = messageStoreBus.getOrCreate(instance.id)
+        const messageIds = store.getSessionMessageIds(sessionId)
+        const infoMap = new Map<string, MessageInfo>()
+        messageIds.forEach((id) => {
+          const info = store.getMessageInfo(id)
+          if (info) infoMap.set(id, info)
+        })
 
-        if (revert?.messageID) {
-          for (let i = session.messages.length - 1; i >= 0; i--) {
-            const msg = session.messages[i]
-            const info = session.messagesInfo.get(msg.id)
-            if (info?.id === revert.messageID) {
-              after = info.time?.created || 0
-              break
-            }
-          }
+        const revertState = store.getSessionRevert(sessionId) ?? session.revert
+        let after = 0
+        if (revertState?.messageID) {
+          const revertInfo = infoMap.get(revertState.messageID) ?? session.messagesInfo.get(revertState.messageID)
+          after = revertInfo?.time?.created || 0
         }
 
         let messageID = ""
-        for (let i = session.messages.length - 1; i >= 0; i--) {
-          const msg = session.messages[i]
-          const info = session.messagesInfo.get(msg.id)
-
-          if (msg.type === "user" && info?.time?.created) {
+        let restoredText: string | null = null
+        for (let i = messageIds.length - 1; i >= 0; i--) {
+          const id = messageIds[i]
+          const record = store.getMessage(id)
+          const info = infoMap.get(id)
+          if (record?.role === "user" && info?.time?.created) {
             if (after > 0 && info.time.created >= after) {
               continue
             }
-            messageID = msg.id
+            messageID = id
+            restoredText = extractUserTextFromRecord(record)
             break
           }
         }
 
+        if (!messageID) {
+          for (let i = session.messages.length - 1; i >= 0; i--) {
+            const msg = session.messages[i]
+            const info = session.messagesInfo.get(msg.id)
+
+            if (msg.type === "user" && info?.time?.created) {
+              if (after > 0 && info.time.created >= after) {
+                continue
+              }
+              messageID = msg.id
+              const textParts = msg.parts.filter((p): p is ClientPart & { type: "text"; text: string } => p.type === "text" && typeof (p as any).text === "string")
+              if (textParts.length > 0) {
+                restoredText = textParts.map((p) => (p as any).text as string).join("\n")
+              }
+              break
+            }
+          }
+        }
+
         if (!messageID) {
           showAlertDialog("Nothing to undo", {
             title: "No actions to undo",
@@ -274,20 +311,27 @@ export function useCommands(options: UseCommandsOptions) {
             body: { messageID },
           })
 
-          const revertedMessage = session.messages.find((m) => m.id === messageID)
-          const revertedInfo = session.messagesInfo.get(messageID)
-
-          if (revertedMessage && revertedInfo?.role === "user") {
-            const textParts = revertedMessage.parts.filter((p) => p.type === "text")
-            if (textParts.length > 0) {
-              const textarea = document.querySelector(".prompt-input") as HTMLTextAreaElement
-              if (textarea) {
-                textarea.value = textParts.map((p: any) => p.text).join("\n")
-                textarea.dispatchEvent(new Event("input", { bubbles: true }))
-                textarea.focus()
+          if (!restoredText) {
+            const revertedMessage = session.messages.find((m) => m.id === messageID)
+            const revertedInfo = session.messagesInfo.get(messageID)
+            if (revertedMessage && revertedInfo?.role === "user") {
+              const textParts = revertedMessage.parts.filter(
+                (p): p is ClientPart & { type: "text"; text: string } => p.type === "text" && typeof (p as any).text === "string",
+              )
+              if (textParts.length > 0) {
+                restoredText = textParts.map((p) => (p as any).text as string).join("\n")
               }
             }
           }
+
+          if (restoredText) {
+            const textarea = document.querySelector(".prompt-input") as HTMLTextAreaElement
+            if (textarea) {
+              textarea.value = restoredText
+              textarea.dispatchEvent(new Event("input", { bubbles: true }))
+              textarea.focus()
+            }
+          }
         } catch (error) {
           console.error("Failed to revert message:", error)
           showAlertDialog("Failed to revert message", {
diff --git a/packages/ui/src/lib/scroll-cache.ts b/packages/ui/src/lib/scroll-cache.ts
new file mode 100644
index 00000000..ff3f29c7
--- /dev/null
+++ b/packages/ui/src/lib/scroll-cache.ts
@@ -0,0 +1,53 @@
+import type { ScrollSnapshot } from "../stores/message-v2/types"
+
+interface ScrollCacheParams {
+  instanceId?: string
+  sessionId?: string
+  scope?: string
+}
+
+const scrollCache = new Map<string, ScrollSnapshot>()
+const DEFAULT_SCOPE = "session"
+
+function resolve(value?: string) {
+  return value && value.length > 0 ? value : "GLOBAL"
+}
+
+function makeKey(params: ScrollCacheParams) {
+  return `${resolve(params.instanceId)}:${resolve(params.sessionId)}:${params.scope ?? DEFAULT_SCOPE}`
+}
+
+export function setScrollCache(params: ScrollCacheParams, snapshot: Omit<ScrollSnapshot, "updatedAt">) {
+  scrollCache.set(makeKey(params), { ...snapshot, updatedAt: Date.now() })
+}
+
+export function getScrollCache(params: ScrollCacheParams): ScrollSnapshot | undefined {
+  return scrollCache.get(makeKey(params))
+}
+
+export function clearScrollCacheScope(params: ScrollCacheParams) {
+  const key = makeKey(params)
+  scrollCache.delete(key)
+}
+
+export function clearScrollCacheForSession(instanceId?: string, sessionId?: string) {
+  const match = `${resolve(instanceId)}:${resolve(sessionId)}:`
+  for (const key of scrollCache.keys()) {
+    if (key.startsWith(match)) {
+      scrollCache.delete(key)
+    }
+  }
+}
+
+export function clearScrollCacheForInstance(instanceId?: string) {
+  const match = `${resolve(instanceId)}:`
+  for (const key of scrollCache.keys()) {
+    if (key.startsWith(match)) {
+      scrollCache.delete(key)
+    }
+  }
+}
+
+export function clearAllScrollCache() {
+  scrollCache.clear()
+}
diff --git a/packages/ui/src/stores/message-v2/bridge.ts b/packages/ui/src/stores/message-v2/bridge.ts
new file mode 100644
index 00000000..11def492
--- /dev/null
+++ b/packages/ui/src/stores/message-v2/bridge.ts
@@ -0,0 +1,175 @@
+import type { Permission } from "@opencode-ai/sdk"
+import type { Message, MessageInfo, ClientPart } from "../../types/message"
+import type { Session } from "../../types/session"
+import { messageStoreBus } from "./bus"
+import type { MessageStatus, SessionRevertState } from "./types"
+
+interface SessionMetadata {
+  id: string
+  title?: string
+  parentId?: string | null
+}
+
+function resolveSessionMetadata(session?: Session | null): SessionMetadata | undefined {
+  if (!session) return undefined
+  return {
+    id: session.id,
+    title: session.title,
+    parentId: session.parentId ?? null,
+  }
+}
+
+function normalizeStatus(status: Message["status"]): MessageStatus {
+  switch (status) {
+    case "sending":
+    case "sent":
+    case "streaming":
+    case "complete":
+    case "error":
+      return status
+    default:
+      return "complete"
+  }
+}
+
+export function seedSessionMessagesV2(
+  instanceId: string,
+  session: Session | SessionMetadata,
+  messages: Message[],
+  messageInfos?: Map<string, MessageInfo>,
+): void {
+  if (!session || !Array.isArray(messages)) return
+  const store = messageStoreBus.getOrCreate(instanceId)
+  const metadata: SessionMetadata = "id" in session ? { id: session.id, title: session.title, parentId: session.parentId ?? null } : session
+  const messageIds = messages.map((message) => message.id)
+
+  store.addOrUpdateSession({
+    id: metadata.id,
+    title: metadata.title,
+    parentId: metadata.parentId ?? null,
+    messageIds,
+    revert: (session as Session)?.revert ?? undefined,
+  })
+
+  messages.forEach((message) => {
+    store.upsertMessage({
+      id: message.id,
+      sessionId: message.sessionId,
+      role: message.type,
+      status: normalizeStatus(message.status),
+      createdAt: message.timestamp,
+      updatedAt: message.timestamp,
+      parts: message.parts,
+      isEphemeral: message.status === "sending" || message.status === "streaming",
+      bumpRevision: false,
+    })
+    const info = messageInfos?.get(message.id)
+    if (info) {
+      store.setMessageInfo(message.id, info)
+    }
+  })
+
+  if (messageInfos) {
+    store.rebuildUsage(metadata.id, messageInfos.values())
+  }
+}
+
+interface MessageInfoOptions {
+  status?: MessageStatus
+  bumpRevision?: boolean
+}
+
+export function upsertMessageInfoV2(instanceId: string, info: MessageInfo | null | undefined, options?: MessageInfoOptions): void {
+  if (!info || typeof info.id !== "string" || typeof info.sessionID !== "string") {
+    return
+  }
+  const store = messageStoreBus.getOrCreate(instanceId)
+  const timeInfo = (info.time ?? {}) as { created?: number; completed?: number }
+  const createdAt = typeof timeInfo.created === "number" ? timeInfo.created : Date.now()
+  const completedAt = typeof timeInfo.completed === "number" ? timeInfo.completed : undefined
+
+  store.upsertMessage({
+    id: info.id,
+    sessionId: info.sessionID,
+    role: info.role === "user" ? "user" : "assistant",
+    status: options?.status ?? "complete",
+    createdAt,
+    updatedAt: completedAt ?? createdAt,
+    bumpRevision: Boolean(options?.bumpRevision),
+  })
+  store.setMessageInfo(info.id, info)
+}
+
+export function applyPartUpdateV2(instanceId: string, part: ClientPart | null | undefined): void {
+  if (!part || typeof part.messageID !== "string") {
+    return
+  }
+  const store = messageStoreBus.getOrCreate(instanceId)
+  store.applyPartUpdate({
+    messageId: part.messageID,
+    part,
+  })
+}
+
+export function replaceMessageIdV2(instanceId: string, oldId: string, newId: string): void {
+  if (!oldId || !newId || oldId === newId) return
+  const store = messageStoreBus.getOrCreate(instanceId)
+  store.replaceMessageId({ oldId, newId })
+}
+
+function extractPermissionMessageId(permission: Permission): string | undefined {
+  return (permission as any).messageID || (permission as any).messageId
+}
+
+function extractPermissionPartId(permission: Permission): string | undefined {
+  const metadata = (permission as any).metadata || {}
+  return (
+    (permission as any).callID ||
+    (permission as any).callId ||
+    (permission as any).toolCallID ||
+    (permission as any).toolCallId ||
+    metadata.partId ||
+    metadata.partID ||
+    metadata.callID ||
+    metadata.callId ||
+    undefined
+  )
+}
+
+export function upsertPermissionV2(instanceId: string, permission: Permission): void {
+  if (!permission) return
+  const store = messageStoreBus.getOrCreate(instanceId)
+  store.upsertPermission({
+    permission,
+    messageId: extractPermissionMessageId(permission),
+    partId: extractPermissionPartId(permission),
+    enqueuedAt: (permission as any).time?.created ?? Date.now(),
+  })
+}
+
+export function removePermissionV2(instanceId: string, permissionId: string): void {
+  if (!permissionId) return
+  const store = messageStoreBus.getOrCreate(instanceId)
+  store.removePermission(permissionId)
+}
+
+export function ensureSessionMetadataV2(instanceId: string, session: Session | null | undefined): void {
+  if (!session) return
+  const store = messageStoreBus.getOrCreate(instanceId)
+  store.addOrUpdateSession({
+    id: session.id,
+    title: session.title,
+    parentId: session.parentId ?? null,
+    messageIds: session.messages.map((message: Message) => message.id),
+  })
+}
+
+export function getSessionMetadataFromStore(session?: Session | null): SessionMetadata | undefined {
+  return resolveSessionMetadata(session ?? undefined)
+}
+
+export function setSessionRevertV2(instanceId: string, sessionId: string, revert?: SessionRevertState | null): void {
+  if (!sessionId) return
+  const store = messageStoreBus.getOrCreate(instanceId)
+  store.setSessionRevert(sessionId, revert ?? null)
+}
diff --git a/packages/ui/src/stores/message-v2/bus.ts b/packages/ui/src/stores/message-v2/bus.ts
new file mode 100644
index 00000000..ff027818
--- /dev/null
+++ b/packages/ui/src/stores/message-v2/bus.ts
@@ -0,0 +1,41 @@
+import { createInstanceMessageStore } from "./instance-store"
+import type { InstanceMessageStore } from "./instance-store"
+
+class MessageStoreBus {
+  private stores = new Map<string, InstanceMessageStore>()
+
+  registerInstance(instanceId: string, store?: InstanceMessageStore): InstanceMessageStore {
+    if (this.stores.has(instanceId)) {
+      return this.stores.get(instanceId) as InstanceMessageStore
+    }
+
+    const resolved = store ?? createInstanceMessageStore(instanceId)
+    this.stores.set(instanceId, resolved)
+    return resolved
+  }
+
+  getInstance(instanceId: string): InstanceMessageStore | undefined {
+    return this.stores.get(instanceId)
+  }
+
+  getOrCreate(instanceId: string): InstanceMessageStore {
+    return this.registerInstance(instanceId)
+  }
+
+  unregisterInstance(instanceId: string) {
+    const store = this.stores.get(instanceId)
+    if (store) {
+      store.clearInstance()
+    }
+    this.stores.delete(instanceId)
+  }
+
+  clearAll() {
+    for (const [instanceId, store] of this.stores.entries()) {
+      store.clearInstance()
+      this.stores.delete(instanceId)
+    }
+  }
+}
+
+export const messageStoreBus = new MessageStoreBus()
diff --git a/packages/ui/src/stores/message-v2/instance-store.ts b/packages/ui/src/stores/message-v2/instance-store.ts
new file mode 100644
index 00000000..82cb5751
--- /dev/null
+++ b/packages/ui/src/stores/message-v2/instance-store.ts
@@ -0,0 +1,523 @@
+import { createStore, produce, reconcile } from "solid-js/store"
+import type { SetStoreFunction } from "solid-js/store"
+import type { ClientPart, MessageInfo } from "../../types/message"
+import type {
+  InstanceMessageState,
+  MessageRecord,
+  MessageUpsertInput,
+  PartUpdateInput,
+  PendingPartEntry,
+  PermissionEntry,
+  ReplaceMessageIdOptions,
+  ScrollSnapshot,
+  SessionRecord,
+  SessionUpsertInput,
+  SessionUsageState,
+  UsageEntry,
+} from "./types"
+
+function createInitialState(instanceId: string): InstanceMessageState {
+  return {
+    instanceId,
+    sessions: {},
+    sessionOrder: [],
+    messages: {},
+    messageInfo: {},
+    pendingParts: {},
+    permissions: {
+      queue: [],
+      active: null,
+      byMessage: {},
+    },
+    usage: {},
+    scrollState: {},
+  }
+}
+
+function ensurePartId(messageId: string, part: ClientPart, index: number): string {
+  if (typeof part.id === "string" && part.id.length > 0) {
+    return part.id
+  }
+  return `${messageId}-part-${index}`
+}
+
+function clonePart(part: ClientPart): ClientPart {
+  return JSON.parse(JSON.stringify(part)) as ClientPart
+}
+
+function createEmptyUsageState(): SessionUsageState {
+  return {
+    entries: {},
+    totalInputTokens: 0,
+    totalOutputTokens: 0,
+    totalReasoningTokens: 0,
+    totalCost: 0,
+    actualUsageTokens: 0,
+    latestMessageId: undefined,
+  }
+}
+
+function extractUsageEntry(info: MessageInfo | undefined): UsageEntry | null {
+  if (!info || info.role !== "assistant") return null
+  const messageId = typeof info.id === "string" ? info.id : undefined
+  if (!messageId) return null
+  const tokens = info.tokens
+  if (!tokens) return null
+  const inputTokens = tokens.input ?? 0
+  const outputTokens = tokens.output ?? 0
+  const reasoningTokens = tokens.reasoning ?? 0
+  const cacheReadTokens = tokens.cache?.read ?? 0
+  const cacheWriteTokens = tokens.cache?.write ?? 0
+  if (inputTokens === 0 && outputTokens === 0 && reasoningTokens === 0 && cacheReadTokens === 0 && cacheWriteTokens === 0) {
+    return null
+  }
+  const combinedTokens = info.summary ? outputTokens : inputTokens + cacheReadTokens + cacheWriteTokens + outputTokens + reasoningTokens
+  return {
+    messageId,
+    inputTokens,
+    outputTokens,
+    reasoningTokens,
+    cacheReadTokens,
+    cacheWriteTokens,
+    combinedTokens,
+    cost: info.cost ?? 0,
+    timestamp: info.time?.created ?? 0,
+    hasContextUsage: inputTokens + cacheReadTokens + cacheWriteTokens > 0,
+  }
+}
+
+function applyUsageState(state: SessionUsageState, entry: UsageEntry | null) {
+  if (!entry) return
+  state.entries[entry.messageId] = entry
+  state.totalInputTokens += entry.inputTokens
+  state.totalOutputTokens += entry.outputTokens
+  state.totalReasoningTokens += entry.reasoningTokens
+  state.totalCost += entry.cost
+  if (!state.latestMessageId || entry.timestamp >= (state.entries[state.latestMessageId]?.timestamp ?? 0)) {
+    state.latestMessageId = entry.messageId
+    state.actualUsageTokens = entry.combinedTokens
+  }
+}
+
+function removeUsageEntry(state: SessionUsageState, messageId: string | undefined) {
+  if (!messageId) return
+  const existing = state.entries[messageId]
+  if (!existing) return
+  state.totalInputTokens -= existing.inputTokens
+  state.totalOutputTokens -= existing.outputTokens
+  state.totalReasoningTokens -= existing.reasoningTokens
+  state.totalCost -= existing.cost
+  delete state.entries[messageId]
+  if (state.latestMessageId === messageId) {
+    state.latestMessageId = undefined
+    state.actualUsageTokens = 0
+    let latest: UsageEntry | null = null
+    for (const candidate of Object.values(state.entries) as UsageEntry[]) {
+      if (!latest || candidate.timestamp >= latest.timestamp) {
+        latest = candidate
+      }
+    }
+    if (latest) {
+      state.latestMessageId = latest.messageId
+      state.actualUsageTokens = latest.combinedTokens
+    }
+  }
+}
+
+function rebuildUsageStateFromInfos(infos: Iterable<MessageInfo>): SessionUsageState {
+  const usageState = createEmptyUsageState()
+  for (const info of infos) {
+    const entry = extractUsageEntry(info)
+    if (entry) {
+      applyUsageState(usageState, entry)
+    }
+  }
+  return usageState
+}
+
+export interface InstanceMessageStore {
+
+  instanceId: string
+  state: InstanceMessageState
+  setState: SetStoreFunction<InstanceMessageState>
+  addOrUpdateSession: (input: SessionUpsertInput) => void
+  upsertMessage: (input: MessageUpsertInput) => void
+  applyPartUpdate: (input: PartUpdateInput) => void
+  bufferPendingPart: (entry: PendingPartEntry) => void
+  flushPendingParts: (messageId: string) => void
+  replaceMessageId: (options: ReplaceMessageIdOptions) => void
+  setMessageInfo: (messageId: string, info: MessageInfo) => void
+  getMessageInfo: (messageId: string) => MessageInfo | undefined
+  upsertPermission: (entry: PermissionEntry) => void
+  removePermission: (permissionId: string) => void
+  getPermissionState: (messageId?: string, partId?: string) => { entry: PermissionEntry; active: boolean } | null
+  setSessionRevert: (sessionId: string, revert?: SessionRecord["revert"] | null) => void
+  getSessionRevert: (sessionId: string) => SessionRecord["revert"] | undefined | null
+  rebuildUsage: (sessionId: string, infos: Iterable<MessageInfo>) => void
+  getSessionUsage: (sessionId: string) => SessionUsageState | undefined
+  setScrollSnapshot: (sessionId: string, scope: string, snapshot: Omit<ScrollSnapshot, "updatedAt">) => void
+  getScrollSnapshot: (sessionId: string, scope: string) => ScrollSnapshot | undefined
+  getSessionMessageIds: (sessionId: string) => string[]
+  getMessage: (messageId: string) => MessageRecord | undefined
+  clearInstance: () => void
+}
+
+export function createInstanceMessageStore(instanceId: string): InstanceMessageStore {
+  const [state, setState] = createStore<InstanceMessageState>(createInitialState(instanceId))
+
+  function withUsageState(sessionId: string, updater: (draft: SessionUsageState) => void) {
+    setState("usage", sessionId, (current) => {
+      const draft = current
+        ? {
+            ...current,
+            entries: { ...current.entries },
+          }
+        : createEmptyUsageState()
+      updater(draft)
+      return draft
+    })
+  }
+
+  function updateUsageWithInfo(info: MessageInfo | undefined) {
+    if (!info || typeof info.sessionID !== "string") return
+    const messageId = typeof info.id === "string" ? info.id : undefined
+    if (!messageId) return
+    withUsageState(info.sessionID, (draft) => {
+      removeUsageEntry(draft, messageId)
+      const entry = extractUsageEntry(info)
+      if (entry) {
+        applyUsageState(draft, entry)
+      }
+    })
+  }
+
+  function rebuildUsage(sessionId: string, infos: Iterable<MessageInfo>) {
+    const usageState = rebuildUsageStateFromInfos(infos)
+    setState("usage", sessionId, usageState)
+  }
+
+  function getSessionUsage(sessionId: string) {
+    return state.usage[sessionId]
+  }
+
+  function ensureSessionEntry(sessionId: string): SessionRecord {
+    const existing = state.sessions[sessionId]
+    if (existing) {
+      return existing
+    }
+
+    const now = Date.now()
+    const session: SessionRecord = {
+      id: sessionId,
+      createdAt: now,
+      updatedAt: now,
+      messageIds: [],
+    }
+
+    setState("sessions", sessionId, session)
+    setState("sessionOrder", (order) => (order.includes(sessionId) ? order : [...order, sessionId]))
+    return session
+  }
+
+  function addOrUpdateSession(input: SessionUpsertInput) {
+    const session = ensureSessionEntry(input.id)
+    const nextMessageIds = Array.isArray(input.messageIds) ? input.messageIds : session.messageIds
+
+    setState("sessions", input.id, {
+      ...session,
+      title: input.title ?? session.title,
+      parentId: input.parentId ?? session.parentId ?? null,
+      updatedAt: Date.now(),
+      messageIds: nextMessageIds,
+      revert: input.revert ?? session.revert ?? null,
+    })
+  }
+
+  function insertMessageIntoSession(sessionId: string, messageId: string) {
+    ensureSessionEntry(sessionId)
+    setState("sessions", sessionId, "messageIds", (ids = []) => {
+      if (ids.includes(messageId)) {
+        return ids
+      }
+      return [...ids, messageId]
+    })
+  }
+
+  function normalizeParts(messageId: string, parts: ClientPart[] | undefined) {
+    if (!parts || parts.length === 0) {
+      return null
+    }
+    const map: MessageRecord["parts"] = {}
+    const ids: string[] = []
+
+    parts.forEach((part, index) => {
+      const id = ensurePartId(messageId, part, index)
+      const cloned = clonePart(part)
+      if (typeof cloned.version !== "number") {
+        cloned.version = 0
+      }
+      map[id] = {
+        id,
+        data: cloned,
+        revision: cloned.version,
+      }
+      ids.push(id)
+    })
+
+    return { map, ids }
+  }
+
+  function upsertMessage(input: MessageUpsertInput) {
+    const normalizedParts = normalizeParts(input.id, input.parts)
+    const shouldBump = Boolean(input.bumpRevision || normalizedParts)
+    const now = Date.now()
+
+    setState("messages", input.id, (previous) => {
+      const revision = previous ? previous.revision + (shouldBump ? 1 : 0) : 0
+      return {
+        id: input.id,
+        sessionId: input.sessionId,
+        role: input.role,
+        status: input.status,
+        createdAt: input.createdAt ?? previous?.createdAt ?? now,
+        updatedAt: input.updatedAt ?? now,
+        isEphemeral: input.isEphemeral ?? previous?.isEphemeral ?? false,
+        revision,
+        partIds: normalizedParts ? normalizedParts.ids : previous?.partIds ?? [],
+        parts: normalizedParts ? normalizedParts.map : previous?.parts ?? {},
+      }
+    })
+
+    insertMessageIntoSession(input.sessionId, input.id)
+    flushPendingParts(input.id)
+  }
+
+  function bufferPendingPart(entry: PendingPartEntry) {
+    setState("pendingParts", entry.messageId, (list = []) => [...list, entry])
+  }
+
+  function applyPartUpdate(input: PartUpdateInput) {
+    const message = state.messages[input.messageId]
+    if (!message) {
+      bufferPendingPart({ messageId: input.messageId, part: input.part, receivedAt: Date.now() })
+      return
+    }
+
+    const partId = ensurePartId(input.messageId, input.part, message.partIds.length)
+    const cloned = clonePart(input.part)
+
+    setState(
+      "messages",
+      input.messageId,
+      produce((draft: MessageRecord) => {
+        if (!draft.partIds.includes(partId)) {
+          draft.partIds = [...draft.partIds, partId]
+        }
+        const existing = draft.parts[partId]
+        const nextRevision = existing ? existing.revision + 1 : cloned.version ?? 0
+        draft.parts[partId] = {
+          id: partId,
+          data: cloned,
+          revision: nextRevision,
+        }
+        draft.updatedAt = Date.now()
+        if (input.bumpRevision ?? true) {
+          draft.revision += 1
+        }
+      }),
+    )
+  }
+
+  function flushPendingParts(messageId: string) {
+    const pending = state.pendingParts[messageId]
+    if (!pending || pending.length === 0) {
+      return
+    }
+    pending.forEach((entry) => applyPartUpdate({ messageId, part: entry.part }))
+    setState("pendingParts", (prev) => {
+      const next = { ...prev }
+      delete next[messageId]
+      return next
+    })
+  }
+
+  function replaceMessageId(options: ReplaceMessageIdOptions) {
+    if (options.oldId === options.newId) return
+    const existing = state.messages[options.oldId]
+    if (!existing) return
+
+    const cloned: MessageRecord = {
+      ...existing,
+      id: options.newId,
+      isEphemeral: false,
+      updatedAt: Date.now(),
+    }
+
+    setState("messages", options.newId, cloned)
+    setState("messages", (prev) => {
+      const next = { ...prev }
+      delete next[options.oldId]
+      return next
+    })
+
+    Object.values(state.sessions).forEach((session) => {
+      const index = session.messageIds.indexOf(options.oldId)
+      if (index === -1) return
+      setState("sessions", session.id, "messageIds", (ids) => {
+        const next = [...ids]
+        next[index] = options.newId
+        return next
+      })
+    })
+
+    const infoEntry = state.messageInfo[options.oldId]
+    if (infoEntry) {
+      setState("messageInfo", options.newId, infoEntry)
+      setState("messageInfo", (prev) => {
+        const next = { ...prev }
+        delete next[options.oldId]
+        return next
+      })
+    }
+
+    const permissionMap = state.permissions.byMessage[options.oldId]
+    if (permissionMap) {
+      setState("permissions", "byMessage", options.newId, permissionMap)
+      setState("permissions", (prev) => {
+        const next = { ...prev }
+        const nextByMessage = { ...next.byMessage }
+        delete nextByMessage[options.oldId]
+        next.byMessage = nextByMessage
+        return next
+      })
+    }
+
+    const pending = state.pendingParts[options.oldId]
+    if (pending) {
+      setState("pendingParts", options.newId, pending)
+      setState("pendingParts", (prev) => {
+        const next = { ...prev }
+        delete next[options.oldId]
+        return next
+      })
+    }
+  }
+
+  function setMessageInfo(messageId: string, info: MessageInfo) {
+    if (!messageId) return
+    setState("messageInfo", messageId, info)
+    updateUsageWithInfo(info)
+  }
+
+  function getMessageInfo(messageId: string) {
+    return state.messageInfo[messageId]
+  }
+
+  function upsertPermission(entry: PermissionEntry) {
+    const messageKey = entry.messageId ?? "__global__"
+    const partKey = entry.partId ?? "__global__"
+
+    setState(
+      "permissions",
+      produce((draft) => {
+        draft.byMessage[messageKey] = draft.byMessage[messageKey] ?? {}
+        draft.byMessage[messageKey][partKey] = entry
+        const existingIndex = draft.queue.findIndex((item) => item.permission.id === entry.permission.id)
+        if (existingIndex === -1) {
+          draft.queue.push(entry)
+        } else {
+          draft.queue[existingIndex] = entry
+        }
+        if (!draft.active || draft.active.permission.id === entry.permission.id) {
+          draft.active = entry
+        }
+      }),
+    )
+  }
+
+  function removePermission(permissionId: string) {
+    setState(
+      "permissions",
+      produce((draft) => {
+        draft.queue = draft.queue.filter((item) => item.permission.id !== permissionId)
+        if (draft.active?.permission.id === permissionId) {
+          draft.active = draft.queue[0] ?? null
+        }
+        Object.keys(draft.byMessage).forEach((messageKey) => {
+          const partEntries = draft.byMessage[messageKey]
+          Object.keys(partEntries).forEach((partKey) => {
+            if (partEntries[partKey].permission.id === permissionId) {
+              delete partEntries[partKey]
+            }
+          })
+          if (Object.keys(partEntries).length === 0) {
+            delete draft.byMessage[messageKey]
+          }
+        })
+      }),
+    )
+  }
+
+  function getPermissionState(messageId?: string, partId?: string) {
+    const messageKey = messageId ?? "__global__"
+    const partKey = partId ?? "__global__"
+    const entry = state.permissions.byMessage[messageKey]?.[partKey]
+    if (!entry) return null
+    const active = state.permissions.active?.permission.id === entry.permission.id
+    return { entry, active }
+  }
+
+  function setSessionRevert(sessionId: string, revert?: SessionRecord["revert"] | null) {
+    if (!sessionId) return
+    ensureSessionEntry(sessionId)
+    setState("sessions", sessionId, "revert", revert ?? null)
+  }
+
+  function getSessionRevert(sessionId: string) {
+    return state.sessions[sessionId]?.revert ?? null
+  }
+
+  function makeScrollKey(sessionId: string, scope: string) {
+    return `${sessionId}:${scope}`
+  }
+
+  function setScrollSnapshot(sessionId: string, scope: string, snapshot: Omit<ScrollSnapshot, "updatedAt">) {
+    const key = makeScrollKey(sessionId, scope)
+    setState("scrollState", key, { ...snapshot, updatedAt: Date.now() })
+  }
+
+  function getScrollSnapshot(sessionId: string, scope: string) {
+    const key = makeScrollKey(sessionId, scope)
+    return state.scrollState[key]
+  }
+
+  function clearInstance() {
+    setState(reconcile(createInitialState(instanceId)))
+  }
+
+  return {
+    instanceId,
+    state,
+    setState,
+    addOrUpdateSession,
+    upsertMessage,
+    applyPartUpdate,
+    bufferPendingPart,
+    flushPendingParts,
+    replaceMessageId,
+    setMessageInfo,
+    getMessageInfo,
+    upsertPermission,
+    removePermission,
+    getPermissionState,
+    setSessionRevert,
+    getSessionRevert,
+    rebuildUsage,
+    getSessionUsage,
+    setScrollSnapshot,
+    getScrollSnapshot,
+    getSessionMessageIds: (sessionId: string) => state.sessions[sessionId]?.messageIds ?? [],
+    getMessage: (messageId: string) => state.messages[messageId],
+    clearInstance,
+  }
+}
diff --git a/packages/ui/src/stores/message-v2/types.ts b/packages/ui/src/stores/message-v2/types.ts
new file mode 100644
index 00000000..946c4dbf
--- /dev/null
+++ b/packages/ui/src/stores/message-v2/types.ts
@@ -0,0 +1,138 @@
+import type { ClientPart, MessageInfo } from "../../types/message"
+import type { Permission } from "@opencode-ai/sdk"
+
+export type MessageStatus = "sending" | "sent" | "streaming" | "complete" | "error"
+export type MessageRole = "user" | "assistant"
+
+export interface NormalizedPartRecord {
+  id: string
+  data: ClientPart
+  revision: number
+}
+
+export interface MessageRecord {
+  id: string
+  sessionId: string
+  role: MessageRole
+  status: MessageStatus
+  createdAt: number
+  updatedAt: number
+  revision: number
+  isEphemeral?: boolean
+  partIds: string[]
+  parts: Record<string, NormalizedPartRecord>
+}
+
+export interface SessionRevertState {
+  messageID?: string
+  partID?: string
+  snapshot?: string
+  diff?: string
+}
+
+export interface SessionRecord {
+  id: string
+  title?: string
+  parentId?: string | null
+  createdAt: number
+  updatedAt: number
+  messageIds: string[]
+  revert?: SessionRevertState | null
+}
+
+export interface PendingPartEntry {
+  messageId: string
+  part: ClientPart
+  receivedAt: number
+}
+
+export interface PermissionEntry {
+  permission: Permission
+  messageId?: string
+  partId?: string
+  enqueuedAt: number
+}
+
+export interface InstancePermissionState {
+  queue: PermissionEntry[]
+  active: PermissionEntry | null
+  byMessage: Record<string, Record<string, PermissionEntry>>
+}
+
+export interface ScrollSnapshot {
+  scrollTop: number
+  atBottom: boolean
+  updatedAt: number
+}
+
+export interface UsageEntry {
+  messageId: string
+  inputTokens: number
+  outputTokens: number
+  reasoningTokens: number
+  cacheReadTokens: number
+  cacheWriteTokens: number
+  combinedTokens: number
+  cost: number
+  timestamp: number
+  hasContextUsage: boolean
+}
+
+export interface SessionUsageState {
+  entries: Record<string, UsageEntry>
+  totalInputTokens: number
+  totalOutputTokens: number
+  totalReasoningTokens: number
+  totalCost: number
+  actualUsageTokens: number
+  latestMessageId?: string
+}
+
+export interface InstanceMessageState {
+  instanceId: string
+  sessions: Record<string, SessionRecord>
+  sessionOrder: string[]
+  messages: Record<string, MessageRecord>
+  messageInfo: Record<string, MessageInfo>
+  pendingParts: Record<string, PendingPartEntry[]>
+  permissions: InstancePermissionState
+  usage: Record<string, SessionUsageState>
+  scrollState: Record<string, ScrollSnapshot>
+}
+
+export interface SessionUpsertInput {
+  id: string
+  title?: string
+  parentId?: string | null
+  messageIds?: string[]
+  revert?: SessionRevertState | null
+}
+
+export interface MessageUpsertInput {
+  id: string
+  sessionId: string
+  role: MessageRole
+  status: MessageStatus
+  parts?: ClientPart[]
+  createdAt?: number
+  updatedAt?: number
+  isEphemeral?: boolean
+  bumpRevision?: boolean
+}
+
+export interface PartUpdateInput {
+  messageId: string
+  part: ClientPart
+  bumpRevision?: boolean
+}
+
+export interface ReplaceMessageIdOptions {
+  oldId: string
+  newId: string
+}
+
+export interface ScrollCacheKey {
+  instanceId: string
+  sessionId: string
+  scope: string
+}
diff --git a/packages/ui/src/stores/session-api.ts b/packages/ui/src/stores/session-api.ts
index b9f28b09..ccc8d581 100644
--- a/packages/ui/src/stores/session-api.ts
+++ b/packages/ui/src/stores/session-api.ts
@@ -32,6 +32,7 @@ import {
   rebuildSessionUsage,
   updateSessionInfo,
 } from "./session-messages"
+import { seedSessionMessagesV2 } from "./message-v2/bridge"
 
 interface SessionForkResponse {
   id: string
@@ -610,6 +611,14 @@ async function loadMessages(instanceId: string, sessionId: string, force = false
       return next
     })
 
+    const sessionForV2 = sessions().get(instanceId)?.get(sessionId) ?? {
+      id: sessionId,
+      title: session?.title,
+      parentId: session?.parentId ?? null,
+      revert: session?.revert,
+    }
+    seedSessionMessagesV2(instanceId, sessionForV2, messages, messagesInfo)
+
   } catch (error) {
     console.error("Failed to load messages:", error)
     throw error
diff --git a/packages/ui/src/stores/session-events.ts b/packages/ui/src/stores/session-events.ts
index 8a466860..0f1e6378 100644
--- a/packages/ui/src/stores/session-events.ts
+++ b/packages/ui/src/stores/session-events.ts
@@ -34,6 +34,14 @@ import {
 } from "./session-messages"
 import { loadMessages } from "./session-api"
 import { setSessionCompactionState } from "./session-compaction"
+import {
+  applyPartUpdateV2,
+  replaceMessageIdV2,
+  upsertMessageInfoV2,
+  upsertPermissionV2,
+  removePermissionV2,
+  setSessionRevertV2,
+} from "./message-v2/bridge"
 
 interface TuiToastEvent {
   type: "tui.toast.show"
@@ -195,6 +203,7 @@ function handleMessageUpdate(instanceId: string, event: MessageUpdateEvent | Mes
           index.partIndex.delete(oldId)
           index.partIndex.set(message.id, existingPartMap)
         }
+        replaceMessageIdV2(instanceId, oldId, message.id)
       }
 
       if (filteredSynthetics || replacedTemp) {
@@ -212,6 +221,7 @@ function handleMessageUpdate(instanceId: string, event: MessageUpdateEvent | Mes
       /* mutations already applied above */
     })
 
+    applyPartUpdateV2(instanceId, part)
     updateSessionInfo(instanceId, part.sessionID)
     refreshPermissionsForSession(instanceId, part.sessionID)
   } else if (event.type === "message.updated") {
@@ -270,6 +280,7 @@ function handleMessageUpdate(instanceId: string, event: MessageUpdateEvent | Mes
             index.partIndex.delete(oldId)
             index.partIndex.set(message.id, existingPartMap)
           }
+          replaceMessageIdV2(instanceId, oldId, message.id)
         }
       } else {
         const newMessage: any = {
@@ -305,8 +316,11 @@ function handleMessageUpdate(instanceId: string, event: MessageUpdateEvent | Mes
       message.displayParts = computeDisplayParts(message, preferences().showThinkingBlocks)
     }
 
+    upsertMessageInfoV2(instanceId, info, { status: "complete" })
+
     session.messagesInfo.set(info.id, info)
     updateUsageFromMessageInfo(instanceId, info.sessionID, info)
+
     withSession(instanceId, info.sessionID, () => {
       /* ensure reactivity */
     })
@@ -359,6 +373,7 @@ function handleSessionUpdate(instanceId: string, event: EventSessionUpdated): vo
       next.set(instanceId, updated)
       return next
     })
+    setSessionRevertV2(instanceId, info.id, info.revert ?? null)
 
     console.log(`[SSE] New session created: ${info.id}`, newSession)
   } else {
@@ -391,6 +406,7 @@ function handleSessionUpdate(instanceId: string, event: EventSessionUpdated): vo
       next.set(instanceId, updated)
       return next
     })
+    setSessionRevertV2(instanceId, info.id, info.revert ?? null)
   }
 }
 
@@ -490,6 +506,7 @@ function handlePermissionUpdated(instanceId: string, event: EventPermissionUpdat
 
   console.log(`[SSE] Permission updated: ${permission.id} (${permission.type})`)
   addPermissionToQueue(instanceId, permission)
+  upsertPermissionV2(instanceId, permission)
 }
 
 function handlePermissionReplied(instanceId: string, event: EventPermissionReplied): void {
@@ -498,6 +515,7 @@ function handlePermissionReplied(instanceId: string, event: EventPermissionRepli
 
   console.log(`[SSE] Permission replied: ${permissionID}`)
   removePermissionFromQueue(instanceId, permissionID)
+  removePermissionV2(instanceId, permissionID)
 }
 
 export {
diff --git a/packages/ui/src/stores/session-status.ts b/packages/ui/src/stores/session-status.ts
index b38cb936..54588104 100644
--- a/packages/ui/src/stores/session-status.ts
+++ b/packages/ui/src/stores/session-status.ts
@@ -1,7 +1,9 @@
 import type { Session, SessionStatus } from "../types/session"
 import type { Message, MessageInfo } from "../types/message"
+import type { MessageRecord } from "./message-v2/types"
 import { sessions } from "./sessions"
 import { isSessionCompactionActive } from "./session-compaction"
+import { messageStoreBus } from "./message-v2/bus"
 
 function getSession(instanceId: string, sessionId: string): Session | null {
   const instanceSessions = sessions().get(instanceId)
@@ -17,21 +19,49 @@ function isSessionCompacting(session: Session): boolean {
   return Boolean(compactingFlag)
 }
 
-function getMessageTimestamp(session: Session, message?: Message): number {
-  if (!message) return Number.NEGATIVE_INFINITY
-  if (typeof message.timestamp === "number" && Number.isFinite(message.timestamp)) {
-    return message.timestamp
+function getLatestInfoFromStore(instanceId: string, sessionId: string, role?: MessageInfo["role"]): MessageInfo | undefined {
+  const store = messageStoreBus.getOrCreate(instanceId)
+  const messageIds = store.getSessionMessageIds(sessionId)
+  let latest: MessageInfo | undefined
+  let latestTimestamp = Number.NEGATIVE_INFINITY
+  for (const id of messageIds) {
+    const info = store.getMessageInfo(id)
+    if (!info) continue
+    if (role && info.role !== role) continue
+    const timestamp = info.time?.created ?? 0
+    if (timestamp >= latestTimestamp) {
+      latest = info
+      latestTimestamp = timestamp
+    }
   }
-  const info = session.messagesInfo.get(message.id)
-  return info?.time?.created ?? Number.NEGATIVE_INFINITY
+  return latest
 }
 
-function getLastMessage(session: Session): Message | undefined {
+function getLastMessageFromStore(instanceId: string, sessionId: string): MessageRecord | undefined {
+  const store = messageStoreBus.getOrCreate(instanceId)
+  const messageIds = store.getSessionMessageIds(sessionId)
+  let latest: MessageRecord | undefined
+  let latestTimestamp = Number.NEGATIVE_INFINITY
+  for (const id of messageIds) {
+    const record = store.getMessage(id)
+    if (!record) continue
+    const info = store.getMessageInfo(id)
+    const timestamp = info?.time?.created ?? record.createdAt ?? Number.NEGATIVE_INFINITY
+    if (timestamp >= latestTimestamp) {
+      latest = record
+      latestTimestamp = timestamp
+    }
+  }
+  return latest
+}
+
+function getLegacyLastMessage(session: Session): Message | undefined {
   let latest: Message | undefined
   let latestTimestamp = Number.NEGATIVE_INFINITY
   for (const message of session.messages) {
     if (!message) continue
-    const timestamp = getMessageTimestamp(session, message)
+    const info = session.messagesInfo.get(message.id)
+    const timestamp = info?.time?.created ?? message.timestamp ?? Number.NEGATIVE_INFINITY
     if (timestamp >= latestTimestamp) {
       latest = message
       latestTimestamp = timestamp
@@ -40,7 +70,7 @@ function getLastMessage(session: Session): Message | undefined {
   return latest
 }
 
-function getLastMessageInfo(session: Session, role?: MessageInfo["role"]): MessageInfo | undefined {
+function getLegacyLastMessageInfo(session: Session, role?: MessageInfo["role"]): MessageInfo | undefined {
   if (session.messagesInfo.size === 0) {
     return undefined
   }
@@ -92,7 +122,28 @@ function isAssistantInfoPending(info?: MessageInfo): boolean {
   return completed < created
 }
 
-function isAssistantStillGenerating(message: Message, info?: MessageInfo): boolean {
+function isAssistantStillGeneratingRecord(record: MessageRecord, info?: MessageInfo): boolean {
+  if (record.role !== "assistant") {
+    return false
+  }
+
+  if (record.status === "error") {
+    return false
+  }
+
+  if (record.status === "streaming" || record.status === "sending") {
+    return true
+  }
+
+  const completedAt = (info?.time as { completed?: number } | undefined)?.completed
+  if (completedAt !== undefined && completedAt !== null) {
+    return false
+  }
+
+  return !(record.status === "complete" || record.status === "sent")
+}
+
+function isAssistantStillGeneratingLegacy(message: Message, info?: MessageInfo): boolean {
   if (message.type !== "assistant") {
     return false
   }
@@ -119,15 +170,20 @@ export function getSessionStatus(instanceId: string, sessionId: string): Session
     return "idle"
   }
 
+  const store = messageStoreBus.getOrCreate(instanceId)
+
   if (isSessionCompactionActive(instanceId, sessionId) || isSessionCompacting(session)) {
     return "compacting"
   }
 
-  const latestUserInfo = getLastMessageInfo(session, "user")
-  const latestAssistantInfo = getLastMessageInfo(session, "assistant")
-  const lastMessage = getLastMessage(session)
-  if (!lastMessage) {
-    const latestInfo = getLastMessageInfo(session)
+  const latestUserInfo = getLatestInfoFromStore(instanceId, sessionId, "user") ?? getLegacyLastMessageInfo(session, "user")
+  const latestAssistantInfo = getLatestInfoFromStore(instanceId, sessionId, "assistant") ?? getLegacyLastMessageInfo(session, "assistant")
+
+  const lastRecord = getLastMessageFromStore(instanceId, sessionId)
+  const legacyFallbackMessage = lastRecord ? undefined : getLegacyLastMessage(session)
+
+  if (!lastRecord && !legacyFallbackMessage) {
+    const latestInfo = latestUserInfo ?? latestAssistantInfo ?? getLegacyLastMessageInfo(session)
     if (!latestInfo) {
       return "idle"
     }
@@ -138,13 +194,22 @@ export function getSessionStatus(instanceId: string, sessionId: string): Session
     return infoCompleted ? "idle" : "working"
   }
 
-  if (lastMessage.type === "user") {
-    return "working"
-  }
-
-  const infoForMessage = session.messagesInfo.get(lastMessage.id) ?? latestAssistantInfo
-  if (isAssistantStillGenerating(lastMessage, infoForMessage)) {
-    return "working"
+  if (lastRecord) {
+    if (lastRecord.role === "user") {
+      return "working"
+    }
+    const infoForRecord = store.getMessageInfo(lastRecord.id) ?? latestAssistantInfo
+    if (infoForRecord && isAssistantStillGeneratingRecord(lastRecord, infoForRecord)) {
+      return "working"
+    }
+  } else if (legacyFallbackMessage) {
+    if (legacyFallbackMessage.type === "user") {
+      return "working"
+    }
+    const infoForLegacy = session.messagesInfo.get(legacyFallbackMessage.id) ?? latestAssistantInfo
+    if (isAssistantStillGeneratingLegacy(legacyFallbackMessage, infoForLegacy)) {
+      return "working"
+    }
   }
 
   if (isAssistantInfoPending(latestAssistantInfo)) {