fix(tui): fix pagination bugs - error display, scroll triggers, and boundary hints

- Fix '[object Object]' error display: extract message from non-Error thrown objects
- Fix PgUp/PgDn/line/half-page scroll not triggering page loads at boundaries
- Make '(scroll up/down for more)' hints only show near page boundaries
- Add missing Binary.lowerBound helper that PR anomalyco#8535 referenced but didn't include

Author: NamedIdentity

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

@@ -619,13 +619,21 @@ export const { use: useSync, provider: SyncProvider } = createSimpleContext({
             )
           } catch (e) {
             const page = store.message_page[sessionID]
+            const msg =
+              e instanceof Error
+                ? e.message
+                : typeof e === "object" && e !== null && "message" in e
+                  ? String((e as Record<string, unknown>).message)
+                  : typeof e === "string"
+                    ? e
+                    : "Unknown error"
             setStore("message_page", sessionID, {
               hasOlder: page?.hasOlder ?? false,
               hasNewer: page?.hasNewer ?? false,
               loading: false,
               oldest: page?.oldest,
               newest: page?.newest,
-              error: e instanceof Error ? e.message : String(e),
+              error: msg,
             })
           } finally {
             loadingGuard.delete(sessionID)
@@ -688,13 +696,21 @@ export const { use: useSync, provider: SyncProvider } = createSimpleContext({
             )
           } catch (e) {
             const page = store.message_page[sessionID]
+            const msg =
+              e instanceof Error
+                ? e.message
+                : typeof e === "object" && e !== null && "message" in e
+                  ? String((e as Record<string, unknown>).message)
+                  : typeof e === "string"
+                    ? e
+                    : "Unknown error"
             setStore("message_page", sessionID, {
               hasOlder: page?.hasOlder ?? false,
               hasNewer: page?.hasNewer ?? false,
               loading: false,
               oldest: page?.oldest,
               newest: page?.newest,
-              error: e instanceof Error ? e.message : String(e),
+              error: msg,
             })
           } finally {
             loadingGuard.delete(sessionID)

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

@@ -199,6 +199,9 @@ export function Session() {
   const [showScrollbar, setShowScrollbar] = kv.signal("scrollbar_visible", false)
   const [diffWrapMode] = kv.signal<"word" | "none">("diff_wrap_mode", "word")
   const [animationsEnabled, setAnimationsEnabled] = kv.signal("animations_enabled", true)
+  const [nearTop, setNearTop] = createSignal(false)
+  const [nearBottom, setNearBottom] = createSignal(false)
+  const BOUNDARY_THRESHOLD = 20
 
   const wide = createMemo(() => dimensions().width > 120)
   const sidebarVisible = createMemo(() => {
@@ -633,6 +636,7 @@ export function Session() {
       hidden: true,
       onSelect: (dialog) => {
         scroll.scrollBy(-scroll.height / 2)
+        setTimeout(loadOlder, 0)
         dialog.clear()
       },
     },
@@ -644,6 +648,7 @@ export function Session() {
       hidden: true,
       onSelect: (dialog) => {
         scroll.scrollBy(scroll.height / 2)
+        setTimeout(loadNewer, 0)
         dialog.clear()
       },
     },
@@ -655,6 +660,7 @@ export function Session() {
       disabled: true,
       onSelect: (dialog) => {
         scroll.scrollBy(-1)
+        setTimeout(loadOlder, 0)
         dialog.clear()
       },
     },
@@ -666,6 +672,7 @@ export function Session() {
       disabled: true,
       onSelect: (dialog) => {
         scroll.scrollBy(1)
+        setTimeout(loadNewer, 0)
         dialog.clear()
       },
     },
@@ -677,6 +684,7 @@ export function Session() {
       hidden: true,
       onSelect: (dialog) => {
         scroll.scrollBy(-scroll.height / 4)
+        setTimeout(loadOlder, 0)
         dialog.clear()
       },
     },
@@ -688,6 +696,7 @@ export function Session() {
       hidden: true,
       onSelect: (dialog) => {
         scroll.scrollBy(scroll.height / 4)
+        setTimeout(loadNewer, 0)
         dialog.clear()
       },
     },
@@ -1032,7 +1041,7 @@ export function Session() {
                 <text fg={theme.textMuted}>Loading older messages...</text>
               </box>
             </Show>
-            <Show when={!paging()?.loading && paging()?.hasOlder}>
+            <Show when={!paging()?.loading && paging()?.hasOlder && nearTop()}>
               <box flexShrink={0} paddingLeft={1}>
                 <text fg={theme.textMuted}>(scroll up for more)</text>
               </box>
@@ -1046,16 +1055,24 @@ export function Session() {
             <scrollbox
               ref={(r) => (scroll = r)}
               onMouseScroll={() => {
+                setNearTop(scroll.scrollTop <= BOUNDARY_THRESHOLD)
+                setNearBottom(scroll.scrollHeight - scroll.scrollTop - scroll.viewport.height <= BOUNDARY_THRESHOLD)
                 loadOlder()
                 loadNewer()
               }}
               onKeyDown={(e) => {
                 // Standard scroll triggers incremental load
                 if (["up", "pageup", "home"].includes(e.name)) {
-                  setTimeout(loadOlder, 0)
+                  setTimeout(() => {
+                    setNearTop(scroll.scrollTop <= BOUNDARY_THRESHOLD)
+                    loadOlder()
+                  }, 0)
                 }
                 if (["down", "pagedown", "end"].includes(e.name)) {
-                  setTimeout(loadNewer, 0)
+                  setTimeout(() => {
+                    setNearBottom(scroll.scrollHeight - scroll.scrollTop - scroll.viewport.height <= BOUNDARY_THRESHOLD)
+                    loadNewer()
+                  }, 0)
                 }
               }}
               viewportCulling={true}
@@ -1176,7 +1193,7 @@ export function Session() {
                 <text fg={theme.textMuted}>Loading newer messages...</text>
               </box>
             </Show>
-            <Show when={!paging()?.loading && paging()?.hasNewer}>
+            <Show when={!paging()?.loading && paging()?.hasNewer && nearBottom()}>
               <box flexShrink={0} paddingLeft={1}>
                 <text fg={theme.textMuted}>(scroll down for more)</text>
               </box>

packages/util/src/binary.ts

@@ -19,6 +19,26 @@ export namespace Binary {
     return { found: false, index: left }
   }
 
+  /**
+   * Find the index of the first element >= id (lower bound).
+   * Returns array.length if all elements are less than id.
+   */
+  export function lowerBound(array: string[], id: string): number {
+    let left = 0
+    let right = array.length
+
+    while (left < right) {
+      const mid = Math.floor((left + right) / 2)
+      if (array[mid] < id) {
+        left = mid + 1
+      } else {
+        right = mid
+      }
+    }
+
+    return left
+  }
+
   export function insert<T>(array: T[], item: T, compare: (item: T) => string): T[] {
     const id = compare(item)
     let left = 0