Adversarial-review follow-up to the S2 slice. The S1 rule froze ALL window
recomputes while renderer.getSelection()?.isActive — but a finished mouse
selection persists by design (boundary/renderer.ts keeps the highlight so
Ctrl+C can re-copy), so a long streaming turn behind a lingering highlight
ballooned the mounted set exactly like pre-windowing (and permanently
ratcheted the Yoga-WASM high-water).
Refinement:
- full freeze only while selection.isDragging (the native walk touches the
live tree on every drag update — destroying a row mid-walk corrupts the
highlight; unchanged from S1 where it matters),
- a finished highlight instead PINS the rows containing
selection.selectedRenderables (parent-climb to the row wrapper via a
WeakMap) as neverWindow — the highlight and a later Ctrl+C copy stay
byte-exact while everything else keeps windowing,
- an active highlight counts as activity (no idle measure churn under it).
Test (headless mock-mouse drag): finished selection persists (isActive,
!isDragging) → 300-row burst keeps peakMounted < 120 AND
getSelectedText() returns the identical text afterward, the selected rows
having been pinned while long scrolled past the margin.
Verified on this build: gate digest otui-capped d5e9558583159eac… (2/2),
mem2000 otui-capped windowing-ON vmhwm 312MB (target ≤ 350), scroll2000
otui-capped p50 2.0ms / p99 6.0ms (gate ≤ 17ms). check exit 0 (648 tests).
Review verdicts on the remaining findings (verified against core source):
- "scrollTop compensation race": rejected — scrollTop is an imperative
scrollbar property (no signal staleness); records fire in document order,
each compensation immediately visible to the next.
- "heights map leak on /new": rejected — the countChanged cleanup prunes
every per-key map against the live key set (test-verified).
- remount-in-viewport estimate shift: only reachable when one frame jumps
past the margin (> 1 viewport); the design's accepted "remounted for
view" path — documented in the header.
- expanded tool/reasoning re-collapse on far-remount: S1-accepted,
deferred (component-local state; out of S2 file ownership).
S2 of docs/plans/opentui-transcript-windowing.md (#27), behind
HERMES_TUI_WINDOWING (OFF path renders the byte-identical legacy tree).
Append-time adjudication: the window now recomputes on transcript GROWTH,
not just scroll — a createComputed on messages.length re-windows
synchronously per append, and while pinned at the bottom computeWindow
anchors to the cumulative content BOTTOM (pinnedBottom) instead of the
stale pre-layout scrollTop, so burst-appended rows are spacer-swapped the
moment they pass the margin. The frame driver additionally treats a
≥ ¼-viewport scrollHeight change (streaming growth) like scroll movement.
Unseen-row default changed from "always mounted" to "mounted iff created
streaming or within the bottom-30" — live rows still paint instantly with
zero added latency; a bulk commitSnapshot (resume) mounts ONLY the bottom
window and everything above starts as line-count-estimate spacers (chip-
and-spacing-aware estimateMessageHeight).
Spacer corrections (zero-jank rule): when a measure lands a height
different from what the spacer occupied, the wrapper's onSizeChange fires
inside the layout traversal, pre-paint. Pinned at bottom the scrollbox's
own sticky re-pin (content onSizeChange runs before the row wrappers')
already compensated — verified by test; otherwise scrollTop is compensated
same-frame for rows fully above the viewport (correctionIsLegal). Frames
stay byte-stable across corrections in both pinned and mid-history tests.
Lazy exact-measure (design §4 — the simple choice, documented): no true
offscreen layout exists in @opentui/core, so an idle pulse (no appends,
no scroll, no turn, no selection for HERMES_TUI_WINDOW_IDLE_MS≈1s) mounts
MEASURE_BATCH_ROWS=10 never-measured rows nearest the bottom window edge
(edgeMeasureBatch), records exact heights (incl. a direct post-layout pull
for rows whose mount changed nothing — no onSizeChange fires), and the
next recompute swaps them back to now-exact spacers. Scrolling itself
still measures the margin band.
DEV counter: windowRowStats (current/peak simultaneously-mounted rows),
exposed on globalThis behind HERMES_TUI_WINDOW_STATS; tests assert it.
Measured (this build, 39f9f433e+S2):
- check: exit 0 (647 tests / 39 files; +11 pure window cases, +4 headless)
- peak mounted: 31 rows over a 1500-row burst; 30 rows on a 600-row
resume snapshot (bound asserted < 120)
- gate digest: otui-capped d5e9558583159eac… — byte-identical, 2/2 reps
- mem2000 (otui-capped, windowing ON, 8GB heap): vmhwm 300MB
(S1 same-heap 518MB; S1 right-sized-heap 427MB; Ink 229-239MB;
target ≤ 350MB)
- scroll2000 otui-capped: p50 2.0ms / p99 5.0ms / max 18ms
(gate ≤ 17ms p99; S1 baseline p99 15ms)
Known S2 limits (deferred to S3, design §5): /compact·/details toggles and
width resizes leave out-of-window spacer heights stale until remount or
the idle march; expanded-body state above the window may re-collapse on
remount (S1-accepted).
Core machinery of docs/plans/opentui-transcript-windowing.md (#27): rows
outside [scrollTop − viewport, scrollTop + 2·viewport) swap to an exact-height
empty <box> (1 yoga node, no text buffers / native handles), so the mounted
set stays ~3 viewports regardless of transcript length.
Flag: HERMES_TUI_WINDOWING — unset → ON; 0/false/no/off → OFF (envFlag
semantics, the bench A/B + one-env escape hatch). OFF renders the exact
legacy tree (no wrapper boxes).
Pieces:
- logic/window.ts (pure, table-tested): computeWindow (viewport ± 1-viewport
margin intersection over cumulative exact heights; null heights fall back
to a per-row line-count estimate), hysteresisFor/shouldRecompute (≥ ¼
viewport between recomputes), correctionIsLegal (the jank rule: corrections
only fully above the viewport with same-frame scrollTop compensation, or
fully below it), estimateMessageHeight (line-count estimate; wrong values
are fixed by remount only — S1 never corrects a spacer in place).
- view/transcript.tsx: per-row measuring wrapper records exact heights via
onSizeChange (only while the real row is mounted); window driver is a
renderer frame callback (setFrameCallback — scroll always renders, so no
extra timer) publishing the mounted set through one signal + createSelector
so only flipped rows re-render. Stable row keys via WeakMap<Message, n>
(messages have no id; store proxies are reference-stable). Solid <Show>
unmount destroys the row's renderables (@opentui/solid _removeNode →
destroyRecursively).
Never-window rules:
- streaming rows (remount would restart native markdown streaming),
- the last row while a turn is running (deltas land there),
- the bottom 30 rows (fixed K — sticky-bottom region; rows under
viewport+margin are mounted by the window calc anyway),
- rows the window has never adjudicated default to MOUNTED (new live rows
paint instantly),
- the whole window FREEZES while a mouse selection is active
(renderer.getSelection()?.isActive — a swap would destroy highlighted
renderables under the native selection walk).
Tests: 30 pure window.test.ts cases + 2 headless integration cases
(transcriptWindow.test.tsx) pinning the zero-jank invariant (scrollHeight
identical ON vs OFF), the renderable shedding, and remount-on-scroll-back.
