feat(tui): add load conversation and session history UI

Adds UI for loading older messages in long-running sessions:
- 'Load more messages' banner appears when 100+ messages present
- Two loading modes: conversation history (stops at compaction) and full session
- Toast notifications show count of messages loaded

Depends on: PR anomalyco#8996 (ts_before and breakpoint API params)

Author: ryanwyler

packages/opencode/src/cli/cmd/tui/context/sync.tsx

@@ -419,6 +419,57 @@ export const { use: useSync, provider: SyncProvider } = createSimpleContext({
           )
           fullSyncedSessions.add(sessionID)
         },
+        async loadConversationHistory(sessionID: string) {
+          const messages = store.message[sessionID]
+          if (!messages || messages.length === 0) return
+
+          const earliest = messages[0]
+          const result = await sdk.client.session.messages({
+            sessionID,
+            ts_before: earliest.time.created,
+            breakpoint: true,
+          })
+
+          if (!result.data || result.data.length === 0) {
+            return 0
+          }
+
+          setStore(
+            produce((draft) => {
+              const existing = draft.message[sessionID] ?? []
+              draft.message[sessionID] = [...result.data!.map((x) => x.info), ...existing]
+              for (const message of result.data!) {
+                draft.part[message.info.id] = message.parts
+              }
+            }),
+          )
+          return result.data.length
+        },
+        async loadFullSessionHistory(sessionID: string) {
+          const messages = store.message[sessionID]
+          if (!messages || messages.length === 0) return
+
+          const earliest = messages[0]
+          const result = await sdk.client.session.messages({
+            sessionID,
+            ts_before: earliest.time.created,
+          })
+
+          if (!result.data || result.data.length === 0) {
+            return 0
+          }
+
+          setStore(
+            produce((draft) => {
+              const existing = draft.message[sessionID] ?? []
+              draft.message[sessionID] = [...result.data!.map((x) => x.info), ...existing]
+              for (const message of result.data!) {
+                draft.part[message.info.id] = message.parts
+              }
+            }),
+          )
+          return result.data.length
+        },
       },
       bootstrap,
     }

packages/opencode/src/cli/cmd/tui/routes/session/index.tsx

@@ -119,6 +119,22 @@ export function Session() {
       .toSorted((a, b) => (a.id < b.id ? -1 : a.id > b.id ? 1 : 0))
   })
   const messages = createMemo(() => sync.data.message[route.sessionID] ?? [])
+
+  const messagesDisplay = createMemo(() => {
+    const msgs = messages()
+    if (msgs.length >= 100) {
+      const synthetic = {
+        id: "__load_more__",
+        sessionID: route.sessionID,
+        role: "system" as const,
+        time: { created: 0, updated: 0, completed: null },
+        _synthetic: true,
+      } as any
+      return [synthetic, ...msgs]
+    }
+    return msgs
+  })
+
   const permissions = createMemo(() => {
     if (session()?.parentID) return []
     return children().flatMap((x) => sync.data.permission[x.id] ?? [])
@@ -921,9 +937,78 @@ export function Session() {
               flexGrow={1}
               scrollAcceleration={scrollAcceleration()}
             >
-              <For each={messages()}>
+              <For each={messagesDisplay()}>
                 {(message, index) => (
                   <Switch>
+                    <Match when={message.id === "__load_more__"}>
+                      {(function () {
+                        const [hoveredButton, setHoveredButton] = createSignal<"conversation" | "full" | null>(null)
+                        const [loading, setLoading] = createSignal(false)
+
+                        const handleLoadConversation = async () => {
+                          if (loading()) return
+                          setLoading(true)
+                          try {
+                            const count = await sync.session.loadConversationHistory(route.sessionID)
+                            if (count === 0) {
+                              toast.show({ message: "No more messages loaded", variant: "info" })
+                            } else {
+                              toast.show({ message: `History loaded (${count} messages)`, variant: "success" })
+                            }
+                          } finally {
+                            setLoading(false)
+                          }
+                        }
+
+                        const handleLoadFull = async () => {
+                          if (loading()) return
+                          setLoading(true)
+                          try {
+                            const count = await sync.session.loadFullSessionHistory(route.sessionID)
+                            if (count === 0) {
+                              toast.show({ message: "No more messages loaded", variant: "info" })
+                            } else {
+                              toast.show({ message: `History loaded (${count} messages)`, variant: "success" })
+                            }
+                          } finally {
+                            setLoading(false)
+                          }
+                        }
+
+                        return (
+                          <box
+                            paddingLeft={2}
+                            paddingRight={2}
+                            paddingTop={1}
+                            paddingBottom={1}
+                            marginBottom={1}
+                            flexDirection="row"
+                            backgroundColor={theme.backgroundPanel}
+                          >
+                            <text fg={theme.textMuted}>Load more messages: </text>
+                            <box
+                              onMouseOver={() => setHoveredButton("conversation")}
+                              onMouseOut={() => setHoveredButton(null)}
+                              onMouseUp={handleLoadConversation}
+                            >
+                              <text fg={hoveredButton() === "conversation" ? theme.accent : theme.text}>
+                                load conversation history
+                              </text>
+                            </box>
+                            <text fg={theme.textMuted}> or </text>
+                            <box
+                              onMouseOver={() => setHoveredButton("full")}
+                              onMouseOut={() => setHoveredButton(null)}
+                              onMouseUp={handleLoadFull}
+                            >
+                              <text fg={hoveredButton() === "full" ? theme.accent : theme.text}>
+                                load full session history
+                              </text>
+                            </box>
+                          </box>
+                        )
+                      })()}
+                    </Match>
                     <Match when={message.id === revert()?.messageID}>
                       {(function () {
                         const command = useCommandDialog()