fix(app): use fixed message page size (#42743)

packages/app/e2e/regression/session-timeline-history-root.spec.ts

@@ -16,9 +16,8 @@ import { mockOpenCodeServer } from "../utils/mock-server"
 import { installSseTransport } from "../utils/sse-transport"
 import { expectSessionTitle } from "../utils/waits"
 
-const initialPageSize = 20
-const historyPageSize = 200
-const messages = Array.from({ length: initialPageSize + 1 }, (_, index) => {
+const messagePageSize = 200
+const messages = Array.from({ length: messagePageSize / 2 + 1 }, (_, index) => {
   const id = `msg_${String(index + 1001).padStart(4, "0")}_history_root_user`
   return [
     userMessage(undefined, { id, created: 1700000000000 + index * 2_000 }),
@@ -26,7 +25,7 @@ const messages = Array.from({ length: initialPageSize + 1 }, (_, index) => {
       id: `msg_${String(index + 1001).padStart(4, "0")}_history_root_assistant`,
       parentID: id,
       created: 1700000001000 + index * 2_000,
-      completed: index < initialPageSize,
+      completed: index < messagePageSize / 2,
     }),
   ]
 }).flat()
@@ -160,21 +159,18 @@ for (const scenario of scenarios) {
     await expect(page.locator(`[data-timeline-part-id="${userPartID}"]`)).toBeVisible()
     const viewport = page.locator(".scroll-view__viewport", { has: page.locator("[data-timeline-row]") })
     await viewport.hover()
-    const deadline = Date.now() + 10_000
+    const deadline = Date.now() + 30_000
     while (requests.filter((request) => request.phase === "start").length < 2) {
       if (Date.now() >= deadline) throw new Error("Timed out scrolling to the history boundary")
-      await page.mouse.wheel(0, -240)
+      await page.mouse.wheel(0, -1_200)
       await page.waitForTimeout(20)
     }
     expect(requests.filter((request) => request.phase === "end")).toHaveLength(1)
     expect(sequence.slice(0, 3)).toEqual([
       "messages:start:latest",
       "messages:end:latest",
-      `messages:start:${messages.at(-initialPageSize)!.info.id}`,
+      `messages:start:${messages.at(-messagePageSize)!.info.id}`,
     ])
-    await expect(page.locator('[data-timeline-part-id*="_history_root_assistant:text:0"]')).toHaveCount(
-      initialPageSize / 2,
-    )
     await page.evaluate(() => {
       ;(
         window as Window & {
@@ -186,15 +182,12 @@ for (const scenario of scenarios) {
     expect(await visibleContentHidden(page)).toBe(false)
     const beforeHistory = await probeSamples(page)
     history.resolve()
-    await expect
-      .poll(() => page.locator('[data-timeline-part-id*="_history_root_assistant:text:0"]').count())
-      .toBeGreaterThan(initialPageSize / 2)
     await expect.poll(() => requests.filter((request) => request.phase === "end").length).toBe(2)
     await expect(page.getByRole("button", { name: "Stop" })).toBeVisible()
     await waitForProbeSamples(page, beforeHistory)
     expect(pages).toEqual([
-      { before: undefined, limit: initialPageSize },
-      { before: messages.at(-initialPageSize)!.info.id, limit: historyPageSize },
+      { before: undefined, limit: messagePageSize },
+      { before: messages.at(-messagePageSize)!.info.id, limit: messagePageSize },
     ])
     expect(roots).toEqual([])
 

packages/app/e2e/smoke/session-timeline.fixture.ts

@@ -222,7 +222,7 @@ function turn(index: number): Message[] {
   return [user, assistantMessage(targetID, index, user.info.id, parts)]
 }
 
-const targetMessages = Array.from({ length: 72 }, (_, index) => turn(index)).flat()
+const targetMessages = Array.from({ length: 101 }, (_, index) => turn(index)).flat()
 const sourceMessages = Array.from({ length: 12 }, (_, index) => [
   userMessage(sourceID, index + 1000, 120),
   assistantMessage(sourceID, index + 1000, id("msg_user", index + 1000), [textPart(index + 1000, 0, 240)]),

packages/app/e2e/smoke/session-timeline.spec.ts

@@ -727,7 +727,7 @@ function expectCompleteScroll(
   ).toEqual([])
   expect(new Set(expectedPartIDs).size).toBe(expectedPartIDs.length)
   expect(new Set(expectedMessageIDs).size).toBe(expectedMessageIDs.length)
-  expect(expectedPartIDs.length).toBe(331)
+  expect(expectedPartIDs.length).toBe(465)
 }
 
 async function selectHomeProject(page: Page, projectName: string) {

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

@@ -618,7 +618,7 @@ describe("server session", () => {
     await ctx.store.sync("root")
 
     expect(ctx.get).toEqual([{ sessionID: "root" }])
-    expect(ctx.messages).toEqual([{ sessionID: "root", limit: 20, order: "desc" }])
+    expect(ctx.messages).toEqual([{ sessionID: "root", limit: 200, order: "desc" }])
     expect(ctx.store.data.message.root).toEqual([])
   })
 
@@ -629,8 +629,32 @@ describe("server session", () => {
     ctx.store.invalidate()
     await ctx.store.sync("root")
 
+    expect(ctx.store.data.message.root).toEqual([])
     expect(ctx.get).toHaveLength(2)
-    expect(ctx.messages).toHaveLength(2)
+    expect(ctx.messages).toEqual([
+      { sessionID: "root", limit: 200, order: "desc" },
+      { sessionID: "root", limit: 200, order: "desc" },
+    ])
+  })
+
+  test("keeps a fixed page size after the local message cache exceeds the API limit", async () => {
+    const client = messageClient(response(), response())
+    const store = createServerSession(client)
+    await store.sync("child")
+    Array.from({ length: 428 }, (_, index) =>
+      store.apply({
+        type: "message.updated",
+        properties: { info: userMessage(`message-${index}`, { time: { created: index } }) },
+      }),
+    )
+
+    expect(store.data.message.child).toHaveLength(428)
+    await store.sync("child", { force: true })
+
+    expect(client.requests).toEqual([
+      { sessionID: "child", limit: 200, order: "desc" },
+      { sessionID: "child", limit: 200, order: "desc" },
+    ])
   })
 
   test("loads current session content through the current message API", async () => {
@@ -655,7 +679,7 @@ describe("server session", () => {
 
     await store.sync("root")
 
-    expect(requests).toEqual([{ sessionID: "root", limit: 20, order: "desc" }])
+    expect(requests).toEqual([{ sessionID: "root", limit: 200, order: "desc" }])
     expect(store.data.session_message.root.map((message) => message.id)).toEqual([user.id, assistant.id])
     expect(store.data.message.root.map((message) => message.id)).toEqual([user.id, assistant.id])
   })
@@ -731,8 +755,8 @@ describe("server session", () => {
     await store.sync("root")
 
     expect(requests).toEqual([
-      { sessionID: "root", limit: 20, order: "desc" },
-      { sessionID: "root", limit: 20, cursor: "older" },
+      { sessionID: "root", limit: 200, order: "desc" },
+      { sessionID: "root", limit: 200, cursor: "older" },
     ])
     expect(store.data.message.root.map((message) => message.id)).toEqual([
       user.id,
@@ -741,6 +765,26 @@ describe("server session", () => {
     expect(assistants.map((item) => store.data.part[item.id]?.[0]?.type)).toEqual(["text", "text", "text"])
   })
 
+  test("loads older messages by cursor with the fixed page size", async () => {
+    const older = userMessage("message-1")
+    const latest = userMessage("message-2", { time: { created: 2 } })
+    const client = messageClient(
+      response([{ info: latest, parts: [] }], "older"),
+      response([{ info: older, parts: [] }]),
+    )
+    const store = createServerSession(client)
+    await store.sync("child")
+
+    await store.history.loadMore("child")
+
+    expect(client.requests).toEqual([
+      { sessionID: "child", limit: 200, order: "desc" },
+      { sessionID: "child", limit: 200, cursor: "older" },
+    ])
+    expect(store.data.message.child).toEqual([older, latest])
+    expect(store.history.more("child")).toBe(false)
+  })
+
   // V2 messages are ordered projections and do not expose V1 assistant parent IDs.
   describe.skip("V1 assistant parent projections", () => {
     test("backfills an assistant-only initial page through its user root", async () => {
@@ -754,7 +798,7 @@ describe("server session", () => {
 
       await store.sync("child")
 
-      expect(client.requests).toEqual([{ sessionID: "child", limit: 20, order: "desc" }])
+      expect(client.requests).toEqual([{ sessionID: "child", limit: 200, order: "desc" }])
       expect(client.rootRequests).toEqual([{ sessionID: "child", messageID: user.id }])
       expect(store.data.message.child).toEqual([user, ...assistants])
       expect(store.history.more("child")).toBe(false)

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

@@ -30,8 +30,7 @@ type MessageApi = ServerApi["message"]
 
 const cmp = (a: string, b: string) => (a < b ? -1 : a > b ? 1 : 0)
 const SKIP_PARTS = new Set(["patch", "step-start", "step-finish"])
-const initialMessagePageSize = 20
-const historyMessagePageSize = 200
+const messagePageSize = 200
 const sessionInfoLimit = 2_048
 const emptyIDs: ReadonlySet<string> = new Set()
 
@@ -242,7 +241,6 @@ export function createServerSession(
     return created
   }
   const [meta, setMeta] = createStore({
-    limit: {} as Record<string, number | undefined>,
     cursor: {} as Record<string, string | undefined>,
     complete: {} as Record<string, boolean | undefined>,
     loading: {} as Record<string, boolean | undefined>,
@@ -423,7 +421,6 @@ export function createServerSession(
     setMeta(
       produce((draft) => {
         for (const sessionID of sessionIDs) {
-          delete draft.limit[sessionID]
           delete draft.cursor[sessionID]
           delete draft.complete[sessionID]
           delete draft.loading[sessionID]
@@ -457,11 +454,15 @@ export function createServerSession(
       pickSessionCacheEvictions({ seen, keep: sessionID, limit: SESSION_CACHE_LIMIT, preserve: protectedSessions() }),
     )
 
-  const fetchMessages = async (sessionID: string, limit: number, before?: string, onAttempt?: () => void) => {
+  const fetchMessages = async (sessionID: string, before?: string, onAttempt?: () => void) => {
     const request = (cursor?: string) =>
       (options?.retry ?? retry)(() => {
         onAttempt?.()
-        return messageApi.list(cursor ? { sessionID, limit, cursor } : { sessionID, limit, order: "desc" })
+        return messageApi.list(
+          cursor
+            ? { sessionID, limit: messagePageSize, cursor }
+            : { sessionID, limit: messagePageSize, order: "desc" },
+        )
       })
     const first = await request(before)
     const pages = [first]
@@ -632,14 +633,13 @@ export function createServerSession(
         }
         orphanParts.delete(sessionID)
       }
-      setMeta("limit", sessionID, messages.length)
       setMeta("cursor", sessionID, merged.cursor)
       setMeta("complete", sessionID, merged.complete)
       setMeta("at", sessionID, Date.now())
     })
   }
 
-  const loadMessages = async (sessionID: string, limit: number, before?: string, mode?: "replace" | "prepend") => {
+  const loadMessages = async (sessionID: string, before?: string, mode?: "replace" | "prepend") => {
     if (meta.loading[sessionID]) return
     const active = generation(sessionID)
     const load: MessageLoadState = {
@@ -658,7 +658,7 @@ export function createServerSession(
     setMeta("loading", sessionID, true)
     let applied = false
     try {
-      const page = await fetchMessages(sessionID, limit, before, () => resetMessageLoad(sessionID, load))
+      const page = await fetchMessages(sessionID, before, () => resetMessageLoad(sessionID, load))
       const first = page.session.reduce<Message | undefined>(
         (oldest, message) => (!oldest || compareMessages(message, oldest) < 0 ? message : oldest),
         undefined,
@@ -737,32 +737,30 @@ export function createServerSession(
     }
   }
 
-  const sync = (sessionID: string, options?: { force?: boolean; messageLimit?: number }) => {
+  const sync = (sessionID: string, options?: { force?: boolean }) => {
     touch(sessionID)
     return runInflight(inflight, sessionID, async () => {
-      const cached = data.message[sessionID] !== undefined && meta.limit[sessionID] !== undefined
+      const cached = data.message[sessionID] !== undefined && meta.complete[sessionID] !== undefined
       const invalid = invalidated.has(sessionID)
       const revision = invalidationRevision
       if (cached && data.info[sessionID] && !invalid && !options?.force) return
       await Promise.all([
         resolve(sessionID, invalid ? { ...options, force: true } : options),
-        cached && !invalid && !options?.force
-          ? Promise.resolve()
-          : loadMessages(sessionID, options?.messageLimit ?? meta.limit[sessionID] ?? initialMessagePageSize),
+        cached && !invalid && !options?.force ? Promise.resolve() : loadMessages(sessionID),
       ])
       if (invalid && invalidationRevision === revision) invalidated.delete(sessionID)
     })
   }
 
-  const prefetch = async (sessionID: string, limit: number) => {
+  const prefetch = async (sessionID: string, messageCount: number) => {
     touch(sessionID)
     await inflight.get(sessionID)
     if (
       Date.now() - (meta.at[sessionID] ?? 0) <= 15_000 &&
-      (meta.complete[sessionID] || (data.message[sessionID]?.length ?? 0) >= limit)
+      (meta.complete[sessionID] || (data.message[sessionID]?.length ?? 0) >= messageCount)
     )
       return
-    await runInflight(inflight, sessionID, () => loadMessages(sessionID, limit))
+    await runInflight(inflight, sessionID, () => loadMessages(sessionID))
   }
 
   const eventSessionID = (event: { type: string; properties?: unknown }) => {
@@ -1354,11 +1352,11 @@ export function createServerSession(
       setMeta("at", {})
     },
     prefetch,
-    shouldPrefetch(sessionID: string, limit: number) {
+    shouldPrefetch(sessionID: string, messageCount: number) {
       if (data.message[sessionID] === undefined) return true
       if (Date.now() - (meta.at[sessionID] ?? 0) > 15_000) return true
       if (meta.complete[sessionID]) return false
-      return (meta.limit[sessionID] ?? 0) <= limit
+      return (data.message[sessionID]?.length ?? 0) <= messageCount
     },
     fresh(sessionID: string, ttl: number) {
       return Date.now() - (meta.at[sessionID] ?? 0) <= ttl
@@ -1440,14 +1438,14 @@ export function createServerSession(
     history: {
       more: (sessionID: string) =>
         data.message[sessionID] !== undefined &&
-        meta.limit[sessionID] !== undefined &&
+        meta.complete[sessionID] !== undefined &&
         !meta.complete[sessionID] &&
         !!meta.cursor[sessionID],
       loading: (sessionID: string) => meta.loading[sessionID] ?? false,
-      async loadMore(sessionID: string, count = historyMessagePageSize) {
+      async loadMore(sessionID: string) {
         touch(sessionID)
         if (meta.loading[sessionID] || meta.complete[sessionID] || !meta.cursor[sessionID]) return
-        await loadMessages(sessionID, count, meta.cursor[sessionID], "prepend")
+        await loadMessages(sessionID, meta.cursor[sessionID], "prepend")
       },
     },
     evict(sessionID: string) {