The RED gate-cert (Codex-verified) found the keep-open was NOT the one-frame
transient the PR claimed: _disarmKeepSettledWorklogOpen() only cleared the token
with no follow-up render, so the just-settled worklog stayed force-open and could
be cached into _sessionHtmlCache and persist across session restores.
Two coordinated fixes:
1. Don't cache the forced-open DOM. Add _isKeepSettledWorklogOpenArmed() and gate
the _sessionHtmlCache.set() population on a typeof-safe !_keepOpenArmed local, so
the armed settle render is never cached. The typeof guard also keeps standalone
renderMessages() node harnesses (which don't define the helper) working.
2. Collapse pass after disarm for BOTH pin states. The STREAM_DONE handler disarms,
then runs _renderMessagesWithScrollSnapshot() UNCONDITIONALLY (a scroll-preserving
re-render that collapses the worklog back to its copied live/user disclosure
state), and only THEN scrollToBottom() for followers to re-settle at the tail.
The second RED gate-cert caught that gating the collapse pass to the non-following
path left a pinned follower forced-open, because scrollToBottom() only settles
scroll position and does NOT re-render. Running the collapse render before the
follower re-settle fixes both pin states. The same-frame JS restore absorbs the
collapse height change instead of leaving it to native scroll-anchoring (which
mobile suppresses mid-render), so there is no jump, and this unarmed render is
the one that populates the cache.
Net: keep-open is genuinely one settle render for pinned AND unpinned readers —
neither persists nor caches — and a user-collapsed worklog is preserved. Verified
e2e on an isolated debug instance for both pin states (worklog open-while-armed ->
collapsed-after-pass; pinned follower stays pinned at tail). Regression tests lock
the cache-skip and the collapse-before-scrollToBottom ordering; the scrollToBottom
adjacency keeps the #1360 done-follow test green.
The STREAM_DONE keep-open exception (#4970 round 6/7) was scoped to PINNED
followers only, on the assumption that unpinned readers 'preserve their viewport
normally'. That holds on desktop (overflow-anchor:none + JS snapshot restore) but
NOT on mobile.
Repro (isolated debug instance + CDP touch emulation, faithful to a real phone):
a reader who scrolls UP to read inside the just-settled turn is UNPINNED. At
STREAM_DONE the live worklog/thinking cards collapse into a compact summary,
shrinking the transcript by hundreds of px ABOVE their viewport. On mobile the
CSS resting value is overflow-anchor:auto, but _fixMobileScrollJank() flips an
inline overflow-anchor:none over the settle render — so native scroll-anchoring
is suppressed during exactly the frame the unpinned reader needs it to absorb the
above-viewport shrink. The content then leaps to the top of the latest turn (the
'往回大跳' report). Single-variable measurement: collapse-with-auto shifts the
reader 0px; collapse-with-none shifts -248px.
Fix: keep the just-settled worklog open for BOTH pin states (still one-shot
scoped to the turn that just settled, so historical worklogs still collapse
compact). This removes the shrink entirely, fixing the jump for every
device/anchor-mode instead of fighting the anchor engine. The #4856 guard and the
mobile overflow-anchor:auto CSS are untouched, so Boev's Android DOM-wipe fix and
akrhin's #MOBILESCROLL fix both stay intact.
- Rename _shouldKeepSettledWorklogOpenForPinnedFollow ->
_shouldKeepSettledWorklogOpenForStreamSettle (drops the _scrollPinned /
_messageUserUnpinned gate; keeps the one-shot stream-id token).
- Update the #4970 behavioral regression test to assert keep-open is TRUE for the
armed turn under BOTH pin states, FALSE for historical turns and after disarm.
Address maintainer must-fix: _shouldKeepSettledWorklogOpenForPinnedFollow()
keyed only on global pin state, so every historical settled worklog re-expanded
on any pinned re-render — defeating the compact default. Gate the keep-open
exception on a one-shot token = the just-settled stream id (armed at STREAM_DONE
renderMessages, disarmed right after), threaded as _shouldKeep...(streamId).
Unpinned path unchanged. Replace source-string test with a behavioral Node test
that drives a second pinned turn and asserts it collapses.
Follow-up to maintainer review on #5058: make the pinned-follower helper comment
explicit that avoiding the visible STREAM_DONE shrink jump intentionally takes
precedence over a transient user-collapsed live worklog while the reader remains
pinned. Add a source lock so that intent stays documented.
Focused scroll locks remain green (22 passed), node --check clean.
A new post-#4970 scroll-jump class surfaced after Release YH: when a streamed
assistant turn with a large live worklog/tool trace settles, the settled compact
worklog collapses hundreds of pixels at STREAM_DONE. The reader is still pinned
and scroll state is correct, but the net scrollHeight shrink makes the browser
clamp scrollTop down by the same amount, which is visible as a large backward
jump.
Fix by keeping the just-settled activity worklog open for pinned followers
(_scrollPinned && !_messageUserUnpinned), so the live->settled DOM swap is
height-stable. Unpinned readers still get compact settled worklogs and keep their
viewport normally. Also make _anchorSceneWorklogGroup respect opts.collapsed;
previously it hard-coded collapsed: !live so the caller could not request an open
settled group.
Regression locks assert the pinned-follow helper, that settled rendering passes
collapsed:!keepSettledWorklogOpen, and that _anchorSceneWorklogGroup honors an
explicit opts.collapsed. Verified locally with a Playwright repro: before the
fix a large tool-worklog answer produced scrollHeight -367/-422px and scrollTop
-367/-422px at STREAM_DONE; after the fix nShrinks=0 and nBack=0. Local focused
scroll locks pass: 22 passed.
