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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Jul 4, 2026 10:49pm

PR Summary

Low Risk
UI-only scroll and reveal pacing in chat hooks; detach semantics are preserved and behavior is localized to presentation, though file viewers also share the updated useSmoothText pacing.

Overview
Streaming chat auto-scroll no longer jumps to scrollHeight on each DOM mutation. It uses a shared createSmoothBottomChase helper that eases toward the bottom (~12% of the remaining gap per frame), with the same detach/re-attach rules as before; mutation-driven follow and post-stream followToBottom use the same glide instead of instant snaps.

useSmoothText switches from fixed 24ms timer ticks with tiered chunk sizes to a requestAnimationFrame loop: elapsed time builds a character budget via a proportional drain (~400ms horizon, min/max CPS), and reveal advances one word/punctuation boundary at a time so pacing tracks the model’s arrival rate instead of burst-then-pause.

New util: apps/sim/lib/core/utils/smooth-bottom-chase.ts (extracted from subagent viewport behavior), wired from use-auto-scroll.

^{Reviewed by Cursor Bugbot for commit d43a39c. Bugbot is set up for automated code reviews on this repo. Configure here.}

Greptile Summary

This PR replaces two "snap" behaviors in the chat view with smooth, time-based alternatives. Auto-scroll now uses an exponential glide (closing 12% of the remaining gap per frame) shared via a new createSmoothBottomChase utility, and text reveal switches from a fixed-interval setTimeout tick to a per-frame rAF loop that earns a character budget proportional to the current backlog, releasing one word boundary at a time.

• smooth-bottom-chase.ts — new shared utility; exports createSmoothBottomChase with kick/cancel/isActive handle, upward-scroll self-interrupt, and a configurable shouldContinue guard.
• use-auto-scroll.ts — replaces scrollToBottom() + cancelAnimationFrame with chase.kick() throughout; detach/re-attach semantics and followToBottom settle window are unchanged.
• use-smooth-text.ts — setTimeout tick replaced with a requestAnimationFrame loop; introduces drainRate (proportional controller clamped to 45–2400 CPS), fractional budgetRef carry-over, and a 100ms dt clamp to prevent background-tab budget accumulation.

Confidence Score: 4/5

Safe to merge — the scroll and text-reveal changes are self-contained UI improvements with no data-path or state-store impact.

The easing and budget logic are correct, detach/re-attach semantics are preserved, and the new createSmoothBottomChase utility is well-guarded against user-scroll fighting. The stale scrollToBottom dependency in the effect array and the isActive() transient-false window in smooth-bottom-chase are both minor style issues with no observable runtime consequence today.

smooth-bottom-chase.ts — the raf = null at the top of step() creates a brief window where isActive() returns false; worth hardening before this utility gets additional callers beyond use-auto-scroll.ts.

Important Files Changed

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant Stream as Streaming Content
    participant MO as MutationObserver
    participant Chase as createSmoothBottomChase
    participant rAF as requestAnimationFrame
    participant El as scroll container

    Stream->>MO: DOM mutation (new text)
    MO->>Chase: kick()
    Chase->>rAF: schedule step()
    loop "Each frame (gap > CHASE_REST_GAP)"
        rAF->>Chase: step()
        Chase->>El: getTop()
        Chase->>El: setTop(top + max(1, gap x 0.12))
        Chase->>El: "getTop() -> lastTop"
        Chase->>rAF: schedule next step()
    end
    Note over Chase,El: Parks when gap <= 0.5px
    Stream->>MO: DOM mutation (word arrives)
    MO->>Chase: kick() no-op raf not null
    Note over Chase: User scrolls UP
    rAF->>Chase: "step() top < lastTop-1"
    Chase->>Chase: park() stops fighting user
    Note over Stream: isStreaming false
    Stream->>Chase: cancel()
    Stream->>El: followToBottom(300ms) via rAF

%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
sequenceDiagram
    participant Stream as Streaming Content
    participant MO as MutationObserver
    participant Chase as createSmoothBottomChase
    participant rAF as requestAnimationFrame
    participant El as scroll container

    Stream->>MO: DOM mutation (new text)
    MO->>Chase: kick()
    Chase->>rAF: schedule step()
    loop "Each frame (gap > CHASE_REST_GAP)"
        rAF->>Chase: step()
        Chase->>El: getTop()
        Chase->>El: setTop(top + max(1, gap x 0.12))
        Chase->>El: "getTop() -> lastTop"
        Chase->>rAF: schedule next step()
    end
    Note over Chase,El: Parks when gap <= 0.5px
    Stream->>MO: DOM mutation (word arrives)
    MO->>Chase: kick() no-op raf not null
    Note over Chase: User scrolls UP
    rAF->>Chase: "step() top < lastTop-1"
    Chase->>Chase: park() stops fighting user
    Note over Stream: isStreaming false
    Stream->>Chase: cancel()
    Stream->>El: followToBottom(300ms) via rAF

_{Reviews (1): Last reviewed commit: "improvement(chat): time-based word-at-a-..." | Re-trigger Greptile}