fix(next): stop transcript activity jolts and remove running pill

webviews/src/agent-session/acpmux/App.tsx

@@ -259,7 +259,6 @@ import {
   type SubagentScope,
 } from "./inspector/subagentScope";
 import { pendingToolCalls, waitingSubagents } from "./summary/SubagentStatusList";
-import { AgentsPill } from "./subagents/AgentsPill";
 import { SubagentTray } from "./subagents/SubagentTray";
 import { BackgroundTasksPanel } from "./backgroundTasks/BackgroundTasksPanel";
 import { backgroundGroups, type TaskCache } from "./backgroundTasks/backgroundTasks";
@@ -7567,10 +7566,9 @@ function AcpmuxPane() {
     (id) => showSubagent(id, false),
     snapshot.clockOffsetMs ?? 0,
   );
-  // The agents pill (subagents/AgentsPill.tsx) and each subagent's color (agentTones.ts), which
-  // the pill's list and the transcript's subagent rows share. A streamed chunk makes a new list of
-  // the same agents: the last one stays while nothing the pill shows changed, so a snapshot that
-  // streams text redraws neither the pill nor a subagent row.
+  // Each subagent's color (agentTones.ts), which the transcript's subagent rows share. A streamed
+  // chunk makes a new list of the same agents: the last one stays while nothing a row shows changed,
+  // so a snapshot that streams text redraws neither the row nor its tone.
   const agentsKey = freshAgents
     .map((agent) =>
       [
@@ -11880,20 +11878,6 @@ function AcpmuxPane() {
         {/* The tray (subagents/SubagentTray.tsx): in the bottom stack, right above the composer, every
           running or recently ended subagent, background command and started chat, one card each. */}
         {trayPlacement === "tray" && trayNode}
-        {/* The agents pill (subagents/AgentsPill.tsx), with the tray off (Debug Settings): in the bottom
-          stack, right above the composer, while the turn works; an agent a cancel or a reconnect left
-          "running" shows none. */}
-        {!subagentTray && !quick && !freshView && snapshot.isWorking && chatTones && chatAgents.some(running) && (
-          <SubagentClockContext.Provider value={snapshot.clockOffsetMs ?? 0}>
-            <AgentsPill
-              key={shownSessionId}
-              agents={chatAgents}
-              waiting={waitingAgents}
-              tones={chatTones}
-              onOpen={showSubagent}
-            />
-          </SubagentClockContext.Provider>
-        )}
         {statusCardOpen && (
           <HarnessStatusCard
             summary={snapshot.summary}

webviews/src/agent-session/acpmux/bottomStack.css

@@ -1,6 +1,6 @@
 /* The chat's bottom stack (hq#1957, Leo 2026-10-14), .acpmux-dock: everything under the transcript,
    in this order: a question waiting for an answer (.acpmux-asks-stack), notices, the tray while subagents or background commands run
-   (subagents/SubagentTray.tsx; the agents pill, subagents/AgentsPill.tsx, with it off),
+   (subagents/SubagentTray.tsx),
    then the composer form, which holds the queued prompts (ComposerQueue.tsx), the location strip and
    the card. Every part takes its own height in the stack's own flow, so none draws over another or
    under the pane's edge; a new part joins that flow here.
@@ -37,9 +37,9 @@
 .acpmux-main[data-dock="float"]:has(.acpmux-composer-foot) > .acpmux-dock {
   max-height: calc(100% - 44px - max(64px, var(--acpmux-transcript-min, 96px) - 32px));
 }
-/* A part of the floating stack is a band the pane's width wide whose card, bar or pill sits inset in
-   it by the column's gutters (--cv-inset): the question card, the pull request dock, an error card,
-   the agents pill. The band takes the pointer, since the transcript's rows under the stack are only
+/* A part of the floating stack is a band the pane's width wide whose card or bar sits inset in it by
+   the column's gutters (--cv-inset): the question card, the pull request dock, or an error card. The
+   band takes the pointer, since the transcript's rows under the stack are only
    masked: a hover, click or drag in its gutters or empty room must not reach a row no one sees. The
    wheel there scrolls the transcript all the same (wheelPassThrough.ts forwards it), and a band that
    scrolls itself (the pull request dock, the question card in a short pane) keeps its wheel and its
@@ -49,12 +49,6 @@
 .acpmux-main[data-dock="float"] > .acpmux-dock > .acpmux-composer > * {
   pointer-events: auto;
 }
-.acpmux-dock > .acpmux-agents-pill-anchor {
-  position: relative;
-  flex: none;
-  display: flex;
-  padding: 0 var(--cv-inset-end, var(--cv-inset)) 8px var(--cv-inset);
-}
 /* The tray of running subagents and background commands (subagents/SubagentTray.tsx), aligned
    with the composer card; in a short pane it gives up its height like the parts below. */
 .acpmux-dock > .acpmux-running-tray {
@@ -191,10 +185,9 @@
   }
 }
 
-/* What joins the bottom stack rises out of the composer as it appears (Leo 2026-10-20, directional
-   motion): a question, a notice, the pull request dock, the agents pill and a queued prompt fade in
-   from a few points below where they land (ui-enter, ui/popupSurface.css). Their space opens in one
-   frame, as the stack's flow takes it; only the drawing travels. */
+/* What joins the bottom stack enters from the composer as it appears (Leo 2026-10-20): a question,
+   a notice, the pull request dock, the running tray and a queued prompt use the shared entry tokens.
+   Their space opens in one frame, as the stack's flow takes it; only the drawing travels. */
 .acpmux-dock > :not(.acpmux-composer, .acpmux-home-area, .acpmux-asks-stack),
 .acpmux-asks-stack > *,
 .acpmux-composer-queue > li {

webviews/src/agent-session/acpmux/conversation/conversation.css

@@ -3516,6 +3516,12 @@ a.cv-sha:focus-visible {
   .acpmux-row--enter {
     animation: cv-enter var(--agent-motion-in, 180ms) var(--agent-ease-out, ease-out) both;
   }
+  /* Live activity is absolutely placed by VirtualTranscript. Its first paint must not slide the
+     visible transcript when a subagent or command arrives; the row's measured box is already in
+     the layout, so only its ink fades in. Message rows keep their dedicated presentation motion. */
+  .acpmux-row.acpmux-row--enter:not(.acpmux-user):not(.acpmux-assistant) {
+    animation: cv-enter-fade var(--agent-motion-in, 180ms) var(--agent-ease-out, ease-out) both;
+  }
   .acpmux-row__message-presentation {
     transform-origin: center bottom;
     animation: cv-message-enter var(--agent-motion-in, 180ms) var(--agent-ease-out, ease-out) both;

webviews/src/agent-session/acpmux/conversation/scrollAnchor.test.ts

@@ -66,6 +66,25 @@ test("does not move the row itself when its streaming text grows", () => {
   expect(next).toBe(oldTop);
 });
 
+test("keeps a reader's anchor when a live activity row is appended below it", () => {
+  const oldRows = [row("prompt", "prompt"), row("anchor", "the row in view"), row("reply", "reply")];
+  const activity = row("subagent-done", "Subagent finished");
+  activity.kind = "activity";
+  const newRows = [...oldRows, activity];
+  const oldLayout = layoutConversation(oldRows, 420);
+  const newLayout = layoutConversation(newRows, 420);
+  const oldTop = oldLayout.tops[1]! + 9;
+  const next = preserveScrollAnchorTop({
+    oldLayout,
+    newLayout,
+    oldRows,
+    newRows,
+    liveTop: oldTop,
+    anchorTop: oldTop,
+  });
+  expect(next! - newLayout.tops[1]!).toBe(9);
+});
+
 test("finds the same anchor after older history is inserted above it", () => {
   const oldRows = [row("before", "before"), row("anchor", "the row in view"), row("tail", "tail")];
   const inserted = Array.from({ length: 120 }, (_, index) => row(`old-${index}`, `old ${index}`));

webviews/src/agent-session/acpmux/subagents/runningTray.ts

@@ -8,10 +8,10 @@
 // (conversation/BackgroundTaskNote.tsx).
 //
 // Debug Settings `agentPane.debug.subagentTray` (AgentPaneTunables+SubagentTray.swift) turns it off:
-// the transcript then draws the old group card where the subagents started (SubagentGroup.tsx),
-// the agents pill sits above the composer (AgentsPill.tsx) and the running turn's line counts the
-// work (conversation/WorkingFor.tsx). The host sends it with the theme (`subagentTray`); absent
-// means on.
+// the transcript then draws the old group card where the subagents started (SubagentGroup.tsx) and
+// the running turn's line counts the work (conversation/WorkingFor.tsx). The separate running
+// activity pill above the composer is intentionally not rendered. The host sends the setting with
+// the theme (`subagentTray`); absent means on.
 import { useSyncExternalStore } from "react";
 import type { AcpmuxRow } from "../model";
 import type { StartedSession } from "../started/startedSessions";

webviews/src/agent-session/acpmux/subagents/subagents.css

@@ -1,3 +1,3 @@
 /* Subagent groups (SubagentGroup.tsx), after the ChatGPT and T3 Code apps. Heights are fixed
    and match model.ts: the group line is 48px with 8px above it, each listed subagent 48px, and
    the list's last row adds 8px below. */
@@ -937,24 +937,25 @@
 
 /* ---------- The tray's motion (trayMotion.tsx, Leo 2026-10-26: "following along with the exact
    same things as everything else") ---------- */
-/* The card's entrance and its kept copy's exit. Shipped: the new message's own (the gallery's other
-   arms, trayMotion.experiment.ts, live in gallery/fixtures/trayMotionArms.css only): a live transcript row's cv-enter (conversation.css) on the same
-   tokens, and what leaves on --agent-motion-out. */
+/* The card's entrance and its kept copy's exit. Shipped: the new message's own opacity-only arrival
+   (the gallery's other arms, trayMotion.experiment.ts, live in gallery/fixtures/trayMotionArms.css
+   only), and what leaves on --agent-motion-out. */
 .acpmux-running-tray {
-  --acpmux-tray-enter: cv-enter var(--agent-motion-in, 120ms) var(--agent-ease-out, ease-out) both;
+  /* The tray's box is part of the transcript's dock. Its arrival must not move visible rows; the
+     dock and VirtualTranscript settle their measured height in one frame, then the ink fades in. */
+  --acpmux-tray-enter: cv-enter-fade var(--agent-motion-in, 120ms) var(--agent-ease-out, ease-out) both;
   --acpmux-tray-leave: acpmux-tray-leave var(--agent-motion-out, 80ms) var(--agent-ease-out, ease-out) both;
-  /* A line that joins the open list arrives as a live transcript row does (Leo 2026-10-27: "the
-     bottom running situation still not animating correctly"): the same cv-enter on the same tokens
-     as the card, not the popup's ui-enter (8px on --ui-enter-duration and --ui-enter-ease) that its
-     `data-enter` gives it in ui/popupSurface.css. The attribute stays: SubagentTray.tsx listens for
-     the line's animationend through it, and trayMotion.tsx's leaving copy holds it where it is drawn. */
-  --acpmux-tray-line-enter: cv-enter var(--agent-motion-in, 120ms) var(--agent-ease-out, ease-out) both;
+  /* A line that joins the open list arrives as a live transcript row does: opacity only, so the
+     dock can reserve its measured height without moving the rows already on screen. The attribute
+     stays: SubagentTray.tsx listens for the line's animationend through it, and trayMotion.tsx's
+     leaving copy holds it where it is drawn. */
+  --acpmux-tray-line-enter: cv-enter-fade var(--agent-motion-in, 120ms) var(--agent-ease-out, ease-out) both;
 }
 .acpmux-running-tray__list > li[data-enter] {
   animation: var(--acpmux-tray-line-enter);
 }
-/* Reduce Motion keeps a transcript row's fade without its rise (conversation.css cv-enter-fade); the
-   tray marks no arrival then (SubagentTray.tsx), so this only keeps the two in step if one is marked. */
+/* Reduce Motion keeps the same opacity-only arrival (conversation.css cv-enter-fade); the tray marks
+   no arrival then (SubagentTray.tsx), so this only keeps the two in step if one is marked. */
 @media (prefers-reduced-motion: reduce) {
   .acpmux-running-tray__list > li[data-enter] {
     animation: cv-enter-fade var(--agent-motion-in, 120ms) var(--agent-ease-out, ease-out) both;
@@ -1009,13 +1010,11 @@
 @keyframes acpmux-tick-in {
   from {
     opacity: 0;
-    translate: 0 0.4em;
   }
 }
 @keyframes acpmux-tick-out {
   to {
     opacity: 0;
-    translate: 0 -0.4em;
   }
 }
 

webviews/src/agent-session/acpmux/subagents/trayMotion.tsx

@@ -1,15 +1,15 @@
 // The tray's motion (SubagentTray.tsx), on the same train as the transcript's (Leo 2026-10-26: "Like
 // why is this not animating and, like, following along with the exact same things as everything
-// else?"). Its tokens are the new message's: a live row's entrance (conversation.css `cv-enter`, a
-// fade and a 4px rise on `--agent-motion-in` and `--agent-ease-out`), and `--agent-motion-out` for
-// what leaves; trayMotion.experiment.ts compares two other curves in the gallery.
+// else?"). Its tokens are the new message's opacity-only entrance (conversation.css
+// `cv-enter-fade`) and `--agent-motion-out` for what leaves; trayMotion.experiment.ts compares two
+// other curves in the gallery.
 // - The card eases in when it appears in a chat that already showed without it (the first subagent,
 //   command or chat starting), never when a chat opens with work already running.
 // - It leaves on a kept snapshot: when the last line goes, the card's node is copied in place, over
 //   the bottom stack, and the copy fades and sinks while the real card is already gone, so nothing
 //   waits on the motion and the stack takes its new height at once. A chat switch plays nothing.
-// - Its header's words tick (`Tick`): "2 running" turns to "3 running" with the old words leaving up
-//   and the new rising in, never a jump.
+// - Its header's words tick (`Tick`): "2 running" turns to "3 running" with the old words fading out
+//   and the new fading in, never a positional jump.
 // Reduce Motion, the host's motion switch (`data-agent-motion="off"`, a 0 ms token) and a page that
 // is away apply every change at once, and no copy is made.
 import { useCallback, useRef, useState, type ReactNode } from "react";