fix(app): preserve paginated timeline order (#38641)

packages/app/src/context/server-session.test.ts

@@ -263,7 +263,7 @@ describe("server session", () => {
     expect(store.data.session_message.root.map((message) => message.id)).toEqual([user.id, assistant.id])
   })
 
-  test("reprojects current assistants when an older page supplies their user", async () => {
+  test("extends a current page to include the user for split assistant turns", async () => {
     const user = { id: "msg_1_user", type: "user", text: "hello", time: { created: 1 } } as const
     const assistant = (id: string, created: number) => ({
       id,
@@ -282,17 +282,22 @@ describe("server session", () => {
       { data: assistants.slice(1).toReversed(), cursor: { previous: null, next: "older" } },
       { data: [assistants[0], user], cursor: { previous: null, next: null } },
     ]
+    const requests: unknown[] = []
     const messageApi = {
-      list: async () => pages.shift()!,
+      list: async (input: unknown) => {
+        requests.push(input)
+        return pages.shift()!
+      },
     } as unknown as MessageApi
     const store = createServerSession({} as OpencodeClient, {} as SessionApi, messageApi)
     store.remember(session("root"))
 
     await store.sync("root")
-    expect(store.data.message.root).toEqual([])
-
-    await store.history.loadMore("root")
 
+    expect(requests).toEqual([
+      { sessionID: "root", limit: 20, order: "desc" },
+      { sessionID: "root", limit: 20, cursor: "older" },
+    ])
     expect(store.data.message.root.map((message) => message.id)).toEqual([
       user.id,
       ...assistants.map((item) => item.id),

packages/app/src/context/server-session.ts

@@ -30,6 +30,17 @@ const historyMessagePageSize = 200
 const sessionInfoLimit = 2_048
 const emptyIDs: ReadonlySet<string> = new Set()
 
+function needsOlderTurnRoot(source: readonly SessionMessageInfo[]) {
+  const boundary = source.find(
+    (message) =>
+      message.type === "user" ||
+      message.type === "shell" ||
+      message.type === "assistant" ||
+      (message.type === "synthetic" && message.description?.trim()),
+  )
+  return boundary?.type === "assistant"
+}
+
 type OptimisticItem = {
   message: Message
   parts: Part[]
@@ -525,11 +536,20 @@ export function createServerSession(
 
   const fetchMessages = async (sessionID: string, limit: number, before?: string, onAttempt?: () => void) => {
     if (messageApi && (await options?.protocol) !== "v1") {
-      const response = await (options?.retry ?? retry)(() => {
-        onAttempt?.()
-        return messageApi.list(before ? { sessionID, limit, cursor: before } : { sessionID, limit, order: "desc" })
-      })
-      const source = [...response.data].reverse()
+      const request = (cursor?: string) =>
+        (options?.retry ?? retry)(() => {
+          onAttempt?.()
+          return messageApi.list(cursor ? { sessionID, limit, cursor } : { sessionID, limit, order: "desc" })
+        })
+      const first = await request(before)
+      const pages = [first]
+      while (pages.at(-1)?.cursor.next && needsOlderTurnRoot(pages.flatMap((page) => page.data).toReversed())) {
+        const response = await request(pages.at(-1)!.cursor.next ?? undefined)
+        pages.push(response)
+        if (!response.data.length) break
+      }
+      const response = pages.at(-1)!
+      const source = pages.flatMap((page) => page.data).toReversed()
       const normalized = normalizeSessionMessages(sessionID, source)
       return {
         session: normalized.messages.sort((a, b) => cmp(a.id, b.id)),