feat(session): rework message pagination

Add bidirectional cursor pagination with Link headers across the server, app, TUI, and experimental HttpApi surfaces. Keep large-history revert and restore flows correct with server-backed revert previews, bounded client windows, and paged boundary hydration.

Author: CasualDeveloper

packages/app/src/context/global-sync/event-reducer.ts

@@ -15,8 +15,14 @@ import type { State, VcsCache } from "./types"
 import { trimSessions } from "./session-trim"
 import { dropSessionCaches } from "./session-cache"
 import { diffs as list, message as clean } from "@/utils/diffs"
+import { compareMessages } from "@/context/revert-page"
 
 const SKIP_PARTS = new Set(["patch", "step-start", "step-finish"])
+const messageIndex = (messages: readonly Message[], id: string) => messages.findIndex((message) => message.id === id)
+const messageInsertIndex = (messages: readonly Message[], message: Message) => {
+  const index = messages.findIndex((item) => compareMessages(message, item) < 0)
+  return index === -1 ? messages.length : index
+}
 
 export function applyGlobalEvent(input: {
   event: { type: string; properties?: unknown }
@@ -188,16 +194,16 @@ export function applyDirectoryEvent(input: {
         input.setStore("message", info.sessionID, [info])
         break
       }
-      const result = Binary.search(messages, info.id, (m) => m.id)
-      if (result.found) {
-        input.setStore("message", info.sessionID, result.index, reconcile(info))
+      const index = messageIndex(messages, info.id)
+      if (index !== -1) {
+        input.setStore("message", info.sessionID, index, reconcile(info))
         break
       }
       input.setStore(
         "message",
         info.sessionID,
         produce((draft) => {
-          draft.splice(result.index, 0, info)
+          draft.splice(messageInsertIndex(draft, info), 0, info)
         }),
       )
       break
@@ -208,8 +214,8 @@ export function applyDirectoryEvent(input: {
         produce((draft) => {
           const messages = draft.message[props.sessionID]
           if (messages) {
-            const result = Binary.search(messages, props.messageID, (m) => m.id)
-            if (result.found) messages.splice(result.index, 1)
+            const index = messageIndex(messages, props.messageID)
+            if (index !== -1) messages.splice(index, 1)
           }
           delete draft.part[props.messageID]
         }),

packages/app/src/context/revert-page.test.ts

@@ -0,0 +1,147 @@
+import { describe, expect, test } from "bun:test"
+import type { Message, Part } from "@opencode-ai/sdk/v2/client"
+import { hasVisibleUserBeforeRevert, loadRevertAwareLatestPage } from "./revert-page"
+
+const message = (id: string, role: Message["role"]): Message =>
+  role === "assistant"
+    ? ({
+        id,
+        sessionID: "ses_1",
+        role: "assistant",
+        agent: "default",
+        model: { providerID: "openai", modelID: "gpt-4" },
+        time: { created: Number(id.slice(2)) },
+      } as unknown as Message)
+    : ({
+        id,
+        sessionID: "ses_1",
+        role: "user",
+        agent: "default",
+        model: { providerID: "openai", modelID: "gpt-4" },
+        time: { created: Number(id.slice(2)) },
+      } as unknown as Message)
+
+const textPart = (id: string, messageID: string): Extract<Part, { type: "text" }> => ({
+  id,
+  sessionID: "ses_1",
+  messageID,
+  type: "text",
+  text: id,
+})
+
+describe("revert page helpers", () => {
+  test("detects when the loaded page has no visible user before revert", () => {
+    expect(hasVisibleUserBeforeRevert([message("m6", "user"), message("m7", "assistant")], "m6")).toBe(false)
+    expect(hasVisibleUserBeforeRevert([message("m5", "user"), message("m6", "user")], "m6")).toBe(true)
+  })
+
+  test("loads and merges an older boundary window when latest page is fully reverted", async () => {
+    const olderPart = textPart("p5", "m5")
+    const boundaryPart = textPart("p6", "m6")
+
+    const result = await loadRevertAwareLatestPage({
+      current: {
+        session: [message("m6", "user"), message("m7", "assistant"), message("m8", "user")],
+        part: [
+          { id: "m6", part: [boundaryPart] },
+          { id: "m7", part: [] },
+          { id: "m8", part: [] },
+        ],
+        cursor: undefined,
+        complete: true,
+      },
+      revertMessageID: "m6",
+      fetchMessage: async () => ({ info: message("m6", "user"), parts: [boundaryPart], cursor: "boundary" }),
+      fetchPage: async (before) => {
+        expect(before).toBe("boundary")
+        return {
+          session: [message("m4", "assistant"), message("m5", "user")],
+          part: [
+            { id: "m4", part: [] },
+            { id: "m5", part: [olderPart] },
+          ],
+          cursor: "older",
+          complete: false,
+        }
+      },
+    })
+
+    expect(result.session.map((item) => item.id)).toEqual(["m4", "m5", "m6", "m7", "m8"])
+    expect(result.part.find((item) => item.id === "m5")?.part).toEqual([olderPart])
+    expect(result.part.find((item) => item.id === "m6")?.part).toEqual([boundaryPart])
+    expect(result.cursor).toBe("older")
+    expect(result.complete).toBe(false)
+  })
+
+  test("keeps loading older pages until a visible user exists before revert", async () => {
+    const boundaryPart = textPart("p6", "m6")
+    const olderPart = textPart("p3", "m3")
+    let call = 0
+
+    const result = await loadRevertAwareLatestPage({
+      current: {
+        session: [message("m6", "user"), message("m7", "assistant"), message("m8", "user")],
+        part: [
+          { id: "m6", part: [boundaryPart] },
+          { id: "m7", part: [] },
+          { id: "m8", part: [] },
+        ],
+        cursor: undefined,
+        complete: true,
+      },
+      revertMessageID: "m6",
+      fetchMessage: async () => ({ info: message("m6", "user"), parts: [boundaryPart], cursor: "boundary" }),
+      fetchPage: async () => {
+        call += 1
+        if (call === 1) {
+          return {
+            session: [message("m4", "assistant"), message("m5", "assistant")],
+            part: [
+              { id: "m4", part: [] },
+              { id: "m5", part: [] },
+            ],
+            cursor: "older-2",
+            complete: false,
+          }
+        }
+        return {
+          session: [message("m3", "user")],
+          part: [{ id: "m3", part: [olderPart] }],
+          cursor: undefined,
+          complete: true,
+        }
+      },
+    })
+
+    expect(call).toBe(2)
+    expect(result.session.map((item) => item.id)).toEqual(["m3", "m4", "m5", "m6", "m7", "m8"])
+    expect(result.part.find((item) => item.id === "m3")?.part).toEqual([olderPart])
+    expect(result.cursor).toBeUndefined()
+    expect(result.complete).toBe(true)
+  })
+
+  test("marks stale revert boundaries for clearing when the boundary message is missing", async () => {
+    const result = await loadRevertAwareLatestPage({
+      current: {
+        session: [message("m7", "assistant"), message("m8", "user")],
+        part: [
+          { id: "m7", part: [] },
+          { id: "m8", part: [] },
+        ],
+        cursor: undefined,
+        complete: true,
+      },
+      revertMessageID: "m6",
+      fetchMessage: async () => undefined,
+      fetchPage: async () => ({
+        session: [],
+        part: [],
+        cursor: undefined,
+        complete: true,
+      }),
+    })
+
+    expect(result.clearedRevert).toBe(true)
+    expect(result.session.map((item) => item.id)).toEqual(["m7", "m8"])
+  })
+})

packages/app/src/context/revert-page.ts

@@ -0,0 +1,77 @@
+import type { Message, Part } from "@opencode-ai/sdk/v2/client"
+
+type MessagePage = {
+  session: Message[]
+  part: { id: string; part: Part[] }[]
+  cursor?: string
+  complete: boolean
+  clearedRevert?: boolean
+}
+
+type MessageWithParts = {
+  info: Message
+  parts: Part[]
+  cursor?: string
+}
+
+const cmp = (a: string, b: string) => (a < b ? -1 : a > b ? 1 : 0)
+export const compareMessages = (a: Message, b: Message) => a.time.created - b.time.created || cmp(a.id, b.id)
+export const messageBefore = (message: Message, boundary: Message) => compareMessages(message, boundary) < 0
+
+const sortParts = (parts: Part[]) => parts.filter((part) => !!part?.id).sort((a, b) => cmp(a.id, b.id))
+
+export function hasVisibleUserBeforeRevert(messages: Message[], revertMessageID?: string, boundary?: Message) {
+  if (!revertMessageID) return true
+  const revert = boundary ?? messages.find((message) => message.id === revertMessageID)
+  if (!revert) return messages.some((message) => message.role === "user" && message.id < revertMessageID)
+  return messages.some((message) => message.role === "user" && messageBefore(message, revert))
+}
+
+function mergeMessages(current: Message[], older: Message[], boundary: Message) {
+  const merged = new Map(current.filter((message) => !!message?.id).map((message) => [message.id, message] as const))
+  for (const message of older) {
+    if (!message?.id) continue
+    merged.set(message.id, message)
+  }
+  merged.set(boundary.id, boundary)
+  return [...merged.values()].sort(compareMessages)
+}
+
+function mergeParts(current: MessagePage["part"], older: MessagePage["part"], boundary: MessageWithParts) {
+  const merged = new Map(current.filter((item) => !!item?.id).map((item) => [item.id, sortParts(item.part)] as const))
+  for (const item of older) {
+    if (!item?.id) continue
+    merged.set(item.id, sortParts(item.part))
+  }
+  merged.set(boundary.info.id, sortParts(boundary.parts))
+  return [...merged.entries()].sort((a, b) => cmp(a[0], b[0])).map(([id, part]) => ({ id, part }))
+}
+
+export async function loadRevertAwareLatestPage(input: {
+  current: MessagePage
+  revertMessageID?: string
+  fetchMessage: (messageID: string) => Promise<MessageWithParts | undefined>
+  fetchPage: (before: string) => Promise<MessagePage>
+}) {
+  if (!input.revertMessageID) return input.current
+
+  const boundary = await input.fetchMessage(input.revertMessageID)
+  if (!boundary) return { ...input.current, clearedRevert: true }
+  if (hasVisibleUserBeforeRevert(input.current.session, input.revertMessageID, boundary.info)) return input.current
+  if (!boundary.cursor) return input.current
+
+  let older = await input.fetchPage(boundary.cursor)
+  let session = mergeMessages(input.current.session, older.session, boundary.info)
+  let part = mergeParts(input.current.part, older.part, boundary)
+  while (!hasVisibleUserBeforeRevert(session, input.revertMessageID) && older.cursor) {
+    older = await input.fetchPage(older.cursor)
+    session = mergeMessages(session, older.session, boundary.info)
+    part = mergeParts(part, older.part, boundary)
+  }
+  return {
+    session,
+    part,
+    cursor: older.cursor,
+    complete: older.complete,
+  }
+}