Keep compact Codex history loading

Restart the history observer after every successful page so a collapsed tool page cannot consume the only layout invalidation that would request the next one.\n\nVerified with a cold 365-event tool-heavy sandbox transcript: without scrolling or expanding a group, cache coverage advanced continuously to sequence 1. Android format, compile, lint, and JVM tests pass. Transcript bench: 26 rows/26 units loaded, transcript draw 0.72 ms per frame (debug emulator).

AGENTS.md

@@ -408,6 +408,16 @@ belongs in `~/.claude/TOOLCHAIN.md` or `~/.claude/MACHINE.md` instead.
   the reader hit the end of what was loaded on every swipe and stood there
   for a round trip. It is `HISTORY_SCREENS` viewports now, counted from what
   is actually on screen.
+- **A page landing while the history observer was fetching it could spend the
+  layout change meant to ask for the next one.** The observer collected only
+  `LazyListState.layoutInfo`; while its collector was suspended in
+  `loadOlderPage`, a compact page could be composed and laid out without
+  leaving another change to observe afterward. Codex exposed it because a
+  page full of calls collapses into one tool group: loading stopped until
+  expanding that group forced a layout. The observer is also keyed on
+  `oldestSeq` now, so every successful page restarts it against the settled
+  layout. A failed page does not advance that cursor and still waits for the
+  next scroll instead of retrying in a loop.
 - **Only `fetchTranscript` was off the main thread; the fold was not.**
   `foldEvent` returns a new list per event, so a page is that many copies of
   a growing list — fine at 80 events and about 300,000 element copies at 800,

app/androidApp/src/main/kotlin/com/example/aiapp/SessionScreen.kt

@@ -1041,7 +1041,10 @@ fun SessionScreen(
     // There is no correction beside this one. Following the newest message is not an effect: the
     // list is reversed, so an arriving message extends the end the viewport is pinned to.
     val unitSizes = remember(address) { HashMap<Any, Int>() }
-    LaunchedEffect(listState, moreHistory) {
+    // A successful page advances `oldestSeq` even when its collapsed rows add too little height to
+    // produce another layout after this collector returns. Restarting on that cursor makes the
+    // promised re-check happen; a failed page leaves it unchanged and still waits for a scroll.
+    LaunchedEffect(listState, moreHistory, oldestSeq) {
         snapshotFlow { listState.layoutInfo }
             .collect { info ->
                 val visible = info.visibleItemsInfo