[brucesantos]

Stacked on #8195. This branch contains #8195's three commits; review only the last commit, feat(desktop): open the user's sent message into the timeline. I'll rebase once #8195 lands.

Summary

A sent message appeared in a single frame, and the bottom-pinned timeline jumped up by a whole row at the same moment, so every send read as a pop (#8214).

A row that first mounts while its send is pending now opens into the timeline once:

• SendEntrance (new, desktop/src/features/messages/ui/SendEntrance.tsx) wraps the row. The row grows from zero height (grid-template-rows: 0fr → 1fr) while it fades in, over the shared --motion-duration-standard / --motion-ease-standard tokens. The timeline re-pins to the bottom on each resize, so earlier messages glide up instead of jumping.
• No transforms or filters. Grid track sizing and opacity only, because transform/filter animations inside virtualized rows leave stale paint in WKWebView (Prevent ghost-painted timeline messages in the desktop app #2441).
• Clipping is temporary. The child clips only while growing. The class is dropped on animationend or animationcancel, so the hover action rail is never cut off afterwards.
• Reduced motion: the class is never applied. The pending → sent body dim from fix(desktop): keep pending messages grouped so sends don't shift the timeline #8195 also gets motion-reduce:transition-none.
• MessageRow only decides when: mountedWhilePending is captured at mount. The row keeps its render key through the acknowledgement, so the entrance never replays when the send lands, and rows that arrive already sent (other people's messages, history) never play it.

Measured first, so the scope stays small:

• The composer → optimistic-insert gap is 5–15 ms for plain messages, so the send path is unchanged.
• Messages with links wait ~440 ms for link-preview resolution before the optimistic insert. That's a separate change and is not included here.

Not covered / follow-ups

• Same-second acknowledged order (Desktop: messages sent within the same second can swap places when acknowledged #8192) can still move a row just after its entrance.
• Remounting a still-pending row (scrolling it out of the virtualizer window and back during a slow send) replays the entrance. It's low impact at typical acknowledgement latency, and a per-localKey one-shot set would fix it.
• The entrance tests inject pending rows through the mock bridge. A composer-driven test needs a delayed mock acknowledgement, which the bridge doesn't offer yet.

Related issue

Closes #8214. Related: #8194 / #8195, #8192, #2441.

Testing

• motion.test.mjs: the send entrance uses the shared tokens, its keyframes contain no transform/filter, and it has a reduced-motion rule.

• message-feedback-snapshots.spec.ts, 3 new e2e tests:

  • an own pending message opens once, drops its clipping class afterwards, and neither replays nor resizes on acknowledgement;
  • already-sent messages don't play it;
  • no animation with reduced motion.

  The first and third fail without the feature. All 5 tests in the spec passed 3× in a row.

• Desktop unit suite and tsc --noEmit. Smoke e2e for messaging, virtualization, scroll-history, timeline-no-shift and the feedback spec: 130/131. The one failure, "editing a broadcast reply from a thread returns to the main composer", is pre-existing flakiness: 3/10 failures without this change vs 1/10 with it.

• Manual: rapid sends in a DM on the macOS app, verified frame by frame in a 120 fps recording. The timeline glides monotonically over ~5 frames with no jitter.

Before / after, real speed:

smooth-send-before-after.mp4

buzz-review-completed

🤖 Generated with Claude Code

[github-actions]

🔐 Codex Security Review

Status: review required for the current range.

The current range is 1e80066c932250b87bd8a794f4143c0a88021c30...788fae04a74268092aae2cb9cd3be81cf9eae6b5.
A new review must complete for this exact range. When manual authorization
is required, a user with write access must comment exactly
@buzz-security-review 788fae04a74268092aae2cb9cd3be81cf9eae6b5 to authorize a new review.
Any previous review applies only to its recorded range.