improvement(mothership): stable thinking indicator and jump-free streaming scroll

[TheodoreSpeaks]

Summary

• Rework the thinking indicator into a single fixed-height slot on the last turn — shimmer swaps with arriving output via opacity only, so it never shifts the transcript (previously 4 mount/unmount sites caused up/down jumps)
• Contextual labels derived from the stream (Thinking/Dispatching/Returning); dispatch yields to the agent lane's own shimmer once open
• Fix auto-scroll jerk: followToBottom spawned a new chase loop per animationstart (up to 20 concurrent writers snapping the scroll) — now folded into createSmoothBottomChase via a deadline-extending kickUntil
• Prevent transcript drops from transient markdown re-parse shrinks: sizer min-height floored at the scrolled-to extent while streaming

Type of Change

• Improvement

Testing

Verified with in-browser scroll instrumentation (0 stacked scroll writers, 0 downward transcript moves during streaming, 0px phantom space at settle); vitest 107/107 in the touched tree; lint + strict boundary validation pass

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Jul 22, 2026 1:32am

[cursor]

PR Summary

Medium Risk
Touches live streaming UI, virtualizer sizing, and auto-scroll in the main chat path; behavior is intricate but limited to presentation and scroll, with no auth or data-layer changes.

Overview
Mothership chat streaming UX is reworked so the “waiting” state no longer mounts in several places or shifts layout mid-turn.

The turn-level thinking shimmer lives in a fixed-height slot on the last assistant message only (MessageContent + isLast). It fades in/out with opacity instead of inserting/removing rows; PendingTagIndicator is removed from inline ChatContent and from empty-stream rows in mothership-chat. deriveThinkingLabel replaces shouldShowTrailingThinking, picking Thinking… / Dispatching… / Returning… from the latest content block and hiding the turn shimmer when an open subagent lane owns delegation. ChatContent reports pending special tags separately via onPendingTagChange so mid-stream tags can show the shimmer without treating them as active text painting.

Copy/thumbs move into MessageContent as an actions slot that swaps with the thinking area in one render when the turn settles, instead of appearing below with a separate phase gate.

Scroll stability: createSmoothBottomChase gains kickUntil so use-auto-scroll uses one chase loop (including post-stream settle and coalesced animationstart events) instead of spawning per-animation followToBottom writers. mothership-chat floors the virtualizer sizer minHeight to the current scrolled extent while streaming/reveal animates, reducing transcript drops when markdown re-parse briefly shrinks row height. Chase rate is slightly increased (0.12 → 0.16).

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[greptile-apps]

Greptile Summary

This PR makes streaming chat activity and automatic scrolling more stable. The main changes are:

• Replaces multiple thinking indicators with one fixed activity slot.
• Adds stream-aware Thinking, Dispatching, and Returning labels.
• Coalesces animation-driven scrolling into one deadline-based chase loop.
• Floors the transcript height during streaming to prevent scroll jumps.
• Swaps the activity slot for message actions when the turn settles.

Confidence Score: 5/5

This looks safe to merge.

• The executing-tool suppression and scroll restart fixes cover the reported failure paths.
• No distinct blocking issue remains in the latest changed code.

Important Files Changed

Filename	Overview
apps/sim/app/workspace/[workspaceId]/home/components/message-content/message-content.tsx	Adds the fixed activity slot, contextual activity labels, pending-tag tracking, and settled action swap.
apps/sim/app/workspace/[workspaceId]/home/components/message-content/components/chat-content/chat-content.tsx	Separates visible text-reveal activity from pending special-tag activity.
apps/sim/app/workspace/[workspaceId]/home/components/message-content/components/special-tags/special-tags.tsx	Makes the activity indicator label configurable.
apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx	Integrates the final-turn activity slot and adds a streaming transcript height floor.
apps/sim/hooks/use-auto-scroll.ts	Uses the shared chase loop for animation following and post-stream settling.
apps/sim/lib/core/utils/smooth-bottom-chase.ts	Adds deadline extension, restart baseline seeding, and deadline cleanup to the scroll chase.

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Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

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[cursor]

Stop collapses slot during reveal

Medium Severity

thinkingExpanded forces the reserved slot closed whenever the last segment is stopped, even while phase is still revealing. That contradicts the nearby comment about keeping the slot through post-stream reveal, and with actions gated as already settled it swaps the shimmer slot for the actions row while paced text can still be draining — the layout jump this change set out to avoid.

Additional Locations (1)

• apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx#L224-L230

 

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