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.