Codex round 2 caught that _structuralCount() only enumerated .tool-call-group/
.tool-card-row/.tool-worklog-group but NOT the live Worklog shell
(.live-worklog[data-live-worklog-shell=1]) or its .wl-reason content (built by
_flushPendingSegmentRender / ensureLiveWorklogContainer, see messages.js:2386 +
ui.js:6712/6655). So a turn whose live-ahead structure is a Worklog (not a bare
tool-call-group) undercounted preserved structure → wrongly took the segment-swap
path → detached the visible live Worklog container for a frame.
Fix: add .live-worklog[data-live-worklog-shell=1] and .wl-reason to the structural
count (mirrors the canonical 'has current worklog content' selector set at
sessions.js:1125-1131). Added a structural-test assertion + verified live: a
preserved turn with a live worklog .wl-reason the rebuild lacks now takes the
whole-turn restore path and the worklog + parser both survive.
Convergence: Codex findings narrowing each round (tie-guard → tail-segment →
worklog-selector), all real, all fixed + empirically verified.
Opus flagged a tool-card-frame-loss edge in the segment-only swap: the premise of
#3877 is that the live DOM can be AHEAD of S.messages, so a tool/worklog group can
land in the live turn between the last throttled persist and a mid-stream rebuild.
The rebuild (built from the lagging S.messages) would then lack that group, and a
segment-only swap would drop it for a frame (empirically confirmed: a live-only
tool card present before the rebuild was absent after).
Fix: count structural blocks ([data-live-assistant=1] + tool/worklog/thinking
groups) on both turns. Segment-swap only when the rebuild is the structural
SUPERSET (rebuilt >= preserved); otherwise restore the WHOLE preserved turn so
live-only structure the user already saw never vanishes. Verified live: tool-card-
ahead → whole-turn restore keeps the card + parser; single-segment tie → segment
swap, parser connected; multi-live-segment tail → tail parser connected, both
segments kept.
Also addresses Opus's dead-code note implicitly — the dataset.sessionId stamp now
matters on the whole-turn restore path (it's the branch that actually inserts the
preserved wrapper).
Codex caught an asymmetry in the first cut: the rebuilt side selected the tail
live segment ([...].pop()) but the preserved side used querySelector() = the
FIRST [data-live-assistant=1] segment. In a multi-live-segment turn (reconnect /
post-tool activity boundaries — see messages.js ensureAssistantRow re-attaching
to the LAST live segment), the smd parser writes into the tail segment, so
swapping the first preserved segment would move the wrong node and leave the
parser-owned tail detached — re-introducing the flicker for multi-segment turns.
Fix: select the preserved segment from querySelectorAll, defaulting to the LAST
(tail), and prefer the one whose data-live-segment-seq matches the rebuilt tail;
compute _preservedLen from that segment. Added a structural regression test
pinning the tail selection.
Verified live: a 2-live-segment turn (seq 1 + seq 2, parser on seq 2) keeps the
parser-owned tail connected across a mid-stream rebuild (was orphaned with the
first-segment selection).
The #3877 fix (#3892) preserves the live assistant turn's DOM node across a
mid-stream renderMessages() rebuild and swaps it back in when the rebuilt turn
has less streamed text than the preserved (smd-parser-referenced) node. But the
guard was strict: _rebuiltLen < _preservedLen. At the throttled session
write-back boundary the rebuilt turn's live segment can carry EXACTLY the same
text length as the preserved node, so the strict guard skipped the swap and left
the streaming parser writing into the now-detached original node — the residual
'disappears, then reappears' frame the reporter still saw on v0.51.347.
Fix:
- Relax the guard to _rebuiltLen <= _preservedLen so the equal-length tie also
restores the parser-referenced node (on a tie the preserved node is strictly
preferable: it holds the live parser reference and nothing is lost). When the
rebuilt turn genuinely has MORE content (reconnect where S.messages caught up
past the parser) the guard still skips and the parser re-resolves to the fuller
node.
- Swap at the SEGMENT level (replace only the rebuilt live segment with the
preserved one) instead of a whole-turn replaceWith, so a multi-segment turn
(earlier settled segments + tool/worklog groups built by the rebuild) keeps
that rebuilt-only structure. Whole-turn replace remains the fallback when the
rebuilt turn has no live segment to target.
Verified live (isolated server on the edited ui.js, real shipped renderMessages):
- single-segment tie: parser node stays connected (was orphaned on master);
- multi-segment tie: parser connected AND both assistant segments preserved;
- rebuilt-longer: correctly keeps the fuller rebuilt node, no content loss.
Updated the #3877 structural tests to pin the <= guard + segment-level swap.
Closes#3877.
Hermes Agent