fix(app): use chronological message boundaries

packages/app/src/components/session/session-context-tab.tsx

@@ -123,7 +123,8 @@ export function SessionContextTab() {
     () => {
       const revert = info()?.revert?.messageID
       if (!revert) return userMessages()
-      return userMessages().filter((m) => m.id < revert)
+      const boundary = userMessages().findIndex((message) => message.id === revert)
+      return boundary < 0 ? userMessages() : userMessages().slice(0, boundary)
     },
     emptyUserMessages,
     { equals: same },

packages/app/src/pages/session.tsx

@@ -1851,7 +1851,9 @@ export default function Page() {
 
       const session = sdk().api.session
       const target = sync()
-      const next = userMessages().find((item) => item.id > id)
+      const index = userMessages().findIndex((item) => item.id === id)
+      if (index < 0) return
+      const next = userMessages()[index + 1]
       const last = target.session.get(sessionID)?.revert
 
       await runPromptRollbackMutation({
@@ -1891,8 +1893,10 @@ export default function Page() {
   const rolled = createMemo(() => {
     const id = revertMessageID()
     if (!id) return []
+    const index = userMessages().findIndex((item) => item.id === id)
+    if (index < 0) return []
     return userMessages()
-      .filter((item) => item.id >= id)
+      .slice(index)
       .map((item) => ({ id: item.id, text: line(item.id) }))
   })
 

packages/app/src/pages/session/timeline/message-timeline.tsx

@@ -287,7 +287,9 @@ export function MessageTimeline(props: {
     const visible = new Set(props.userMessages.map((message) => message.id))
     const boundary = sessionMessages().find((message) => message.role === "user" && !visible.has(message.id))?.id
     const messages = sync().data.session_message[id] ?? []
-    return boundary ? messages.filter((message) => message.id < boundary) : messages
+    if (!boundary) return messages
+    const index = messages.findIndex((message) => message.id === boundary)
+    return index < 0 ? messages : messages.slice(0, index)
   })
   const info = createMemo(() => {
     const id = sessionID()

packages/app/src/pages/session/timeline/model.test.ts

@@ -7,11 +7,11 @@ const assistant = (id: string) => ({ id, role: "assistant" }) as AssistantMessag
 
 describe("timeline model", () => {
   test("selects users and applies the revert boundary", () => {
-    const messages: Message[] = [user("msg_1"), assistant("msg_2"), user("msg_3"), user("msg_5")]
+    const messages: Message[] = [user("msg_z"), assistant("msg_a"), user("msg_b"), user("msg_c")]
     const users = selectUserMessages(messages)
 
-    expect(users.map((message) => message.id)).toEqual(["msg_1", "msg_3", "msg_5"])
-    expect(selectVisibleUserMessages(users, "msg_5").map((message) => message.id)).toEqual(["msg_1", "msg_3"])
+    expect(users.map((message) => message.id)).toEqual(["msg_z", "msg_b", "msg_c"])
+    expect(selectVisibleUserMessages(users, "msg_b").map((message) => message.id)).toEqual(["msg_z"])
     expect(selectVisibleUserMessages(users)).toBe(users)
   })
 

packages/app/src/pages/session/timeline/model.ts

@@ -104,7 +104,8 @@ export function isTimelineReady(messages: Message[] | undefined, loading: boolea
 
 export function selectVisibleUserMessages(messages: UserMessage[], revertMessageID?: string) {
   if (!revertMessageID) return messages
-  return messages.filter((message) => message.id < revertMessageID)
+  const boundary = messages.findIndex((message) => message.id === revertMessageID)
+  return boundary < 0 ? messages : messages.slice(0, boundary)
 }
 
 export async function loadOlderTimeline(input: {

packages/app/src/pages/session/timeline/rows-current.test.ts

@@ -137,11 +137,11 @@ describe("current session timeline rows", () => {
 
   test("renders an optimistic user turn and thinking before the protocol message arrives", () => {
     const source = [
-      { id: "msg_1", type: "user", text: "existing", time: { created: 1 } },
+      { id: "msg_z", type: "user", text: "existing", time: { created: 1 } },
     ] satisfies SessionMessageInfo[]
     const normalized = normalizeSessionMessages("ses_1", source)
     const optimistic = {
-      id: "msg_2",
+      id: "msg_a",
       sessionID: "ses_1",
       role: "user" as const,
       time: { created: 2 },
@@ -161,10 +161,10 @@ describe("current session timeline rows", () => {
 
     expect(result.activeMessageID).toBe(optimistic.id)
     expect(result.rows.map(TimelineRow.key)).toEqual([
-      "user-message:msg_1",
-      "turn-gap:msg_2",
-      "user-message:msg_2",
-      "thinking:msg_2",
+      "user-message:msg_z",
+      "turn-gap:msg_a",
+      "user-message:msg_a",
+      "thinking:msg_a",
     ])
   })
 

packages/app/src/pages/session/timeline/rows.ts

@@ -4,6 +4,7 @@ import { AssistantMessage, Part, SessionStatus, UserMessage } from "@opencode-ai
 import { groupParts, renderable, type PartGroup } from "@opencode-ai/session-ui/message-part"
 import { TimelineRow, type SummaryDiff } from "./timeline-row"
 import { uniqueSummaryDiffs } from "./summary-diffs"
+import { compareMessages } from "@/utils/session-message"
 
 export { TimelineRow, type SummaryDiff } from "./timeline-row"
 
@@ -71,12 +72,12 @@ export namespace Timeline {
       turns.push(turn)
       turnByUserID.set(user.id, turn)
     })
-    const latestUserMessageID = turns.at(-1)?.user.id
     projectedUserMessages.forEach((user) => {
       if (turnByUserID.has(user.id)) return
-      if (latestUserMessageID && user.id < latestUserMessageID) return
       const turn = { user, assistants: [] }
-      turns.push(turn)
+      const index = turns.findIndex((item) => compareMessages(user, item.user) < 0)
+      if (index < 0) turns.push(turn)
+      if (index >= 0) turns.splice(index, 0, turn)
       turnByUserID.set(user.id, turn)
     })
     const activeMessageID = turns.at(-1)?.user.id

packages/app/src/pages/session/use-session-commands.tsx

@@ -100,7 +100,8 @@ export const useSessionCommands = (actions: SessionCommandContext) => {
   const visibleUserMessages = () => {
     const revert = info()?.revert?.messageID
     if (!revert) return userMessages()
-    return userMessages().filter((m) => m.id < revert)
+    const boundary = userMessages().findIndex((message) => message.id === revert)
+    return boundary < 0 ? userMessages() : userMessages().slice(0, boundary)
   }
 
   const showAllFiles = () => {
@@ -337,7 +338,9 @@ export const useSessionCommands = (actions: SessionCommandContext) => {
     const promptSession = prompt.capture()
     const revert = info()?.revert?.messageID
     const messages = userMessages()
-    const message = findLast(messages, (x) => !revert || x.id < revert)
+    const boundary = revert ? messages.findIndex((message) => message.id === revert) : messages.length
+    if (boundary < 0) return
+    const message = messages[boundary - 1]
     if (!message) return
     const parts = sync().data.part[message.id]
 
@@ -352,7 +355,7 @@ export const useSessionCommands = (actions: SessionCommandContext) => {
       updatePrompt: (promptSession) => {
         if (parts) promptSession.set(extractPromptFromParts(parts, { directory }))
       },
-      updateViewport: () => setActiveMessage(findLast(messages, (x) => x.id < message.id)),
+      updateViewport: () => setActiveMessage(messages[boundary - 2]),
     })
   }
 
@@ -367,14 +370,16 @@ export const useSessionCommands = (actions: SessionCommandContext) => {
     const revertMessageID = info()?.revert?.messageID
     if (!revertMessageID) return
 
-    const next = messages.find((x) => x.id > revertMessageID)
+    const boundary = messages.findIndex((message) => message.id === revertMessageID)
+    if (boundary < 0) return
+    const next = messages[boundary + 1]
     if (!next) {
       await runCommand({
         owner,
         prompt: promptSession,
         request: () => session.revert.clear({ sessionID }),
         updatePrompt: (promptSession) => promptSession.reset(),
-        updateViewport: () => setActiveMessage(findLast(messages, (x) => x.id >= revertMessageID)),
+        updateViewport: () => setActiveMessage(messages.at(-1)),
       })
       return
     }
@@ -384,7 +389,7 @@ export const useSessionCommands = (actions: SessionCommandContext) => {
       prompt: promptSession,
       request: () => session.revert.stage({ sessionID, messageID: next.id }),
       updatePrompt: () => undefined,
-      updateViewport: () => setActiveMessage(findLast(messages, (x) => x.id < next.id)),
+      updateViewport: () => setActiveMessage(messages[boundary]),
     })
   }