Keep compact transcript history loading

AGENTS.md

@@ -408,16 +408,19 @@ 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.
+- **A page landing while the history observer was fetching it must trigger its
+  own successor.** The observer once 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.
+  Keying the effect on `oldestSeq` still missed the opening prefetch: that key
+  changed while `loadingHistory` was true, so the restarted effect declined to
+  overlap it and never noticed the flag returning to false. Codex exposes both
+  failures because a page full of calls collapses into one tool group: loading
+  stopped until expanding that group forced a layout. The observer now collects
+  the cursor, loading, restoring and failure state with the layout, so returning
+  to not-loading always rechecks the settled height. A failed page turns the
+  history boundary into a Try again control rather than retrying in a loop or
+  requiring another scroll.
 - **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,