fix(chat): one-line activity rows sit 22 apart again (#27580 regression)

webviews/src/agent-session/acpmux/continuationSpacing.test.ts

@@ -126,3 +126,21 @@ test("estimated grid rows follow the Interface Size", () => {
     g.getComputedStyle = saved.getComputedStyle;
   }
 });
+
+test("the live line sits flush under a run of one-line rows: 22 apart top to top (#29965)", () => {
+  const run = row("run", "activity", {
+    items: [{ kind: "tool", text: "", tool: { id: "c", title: "ls", kind: "execute", status: "completed" } }],
+  } as Partial<AcpmuxRow>);
+  const next = row("next", "activity", {
+    items: [{ kind: "tool", text: "", tool: { id: "d", title: "cat x", kind: "execute", status: "completed" } }],
+  } as Partial<AcpmuxRow>);
+  const live = row("live", "thinking", { below: true } as Partial<AcpmuxRow>);
+  const layout = layoutConversation([run, next, live], 720);
+  expect(layout.heights[0]).toBe(22);
+  expect(layout.tops[1]! - layout.tops[0]!).toBe(22);
+  expect(layout.tops[2]! - layout.tops[1]!).toBe(22);
+  // The same live line right under its prompt still waits a block gap under it (grid.md 5.5).
+  const prompt = row("p", "user", { text: "Go" });
+  const waiting = layoutConversation([prompt, live], 720);
+  expect(waiting.tops[1]! - waiting.heights[0]!).toBe(TRANSCRIPT_BLOCK_GAP);
+});

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

@@ -58,7 +58,12 @@
   --cv-message-gap: 0px;
   --cv-turn-gap: 0px;
   --cv-continuation-gap: 0px;
-  --cv-tool-row-height: var(--grid-row);
+  /* One-line activity rows (tool runs, calls, notices, inbox and message lines) sit 22 apart top to
+     top, flush, as Codex lists them (design/chat-transcript.md "One-line row pitch", #29965; Leo,
+     2026-11-01: "doesn't make sense for these to be spaced differently"). #27580 drew them on the
+     28 list row with a 24 block gap between each, about 50 apart (Leo, 2026-11-02: "well now
+     there's sometimes too much spacing between tool calls"). */
+  --cv-tool-row-height: 22px;
   --cv-glyph-slot: var(--grid-transcript-icon-box);
   --cv-glyph-line: var(--grid-transcript-icon-box);
   --cv-disclosure-slot: var(--grid-transcript-icon-box);
@@ -79,18 +84,18 @@
   --cv-message-line: var(--cv-tool-row-height);
   --cv-message-subhead: 22px; /* a sender's head inside that group */
   --cv-live-gap: 10px; /* over the running turn's live line, inside its row */
-  --cv-disclosure-line-height: var(--grid-row);
+  --cv-disclosure-line-height: var(--cv-tool-row-height);
   /* A status row between two replies (model.ts `isStatusRow`) sits in the middle of the gap (Leo,
      2026-10-30: "see how claude code has those centered tool calls / id like more alignment too"):
      the block gap on both sides already centres it, so the status gaps add nothing (model.ts
      STATUS_GAP, STATUS_GAP_PLAIN). */
   --cv-status-gap: 0px;
   --cv-status-gap-plain: 0px;
   --cv-status-gap-plain-over: 0px;
-  /* #30865's reply room and #30400's note gap on the grid: the stack's block gap is the room under a
-     reply and around a note, so neither adds its own. */
+  /* #30865's reply room on the grid: the stack's block gap is the room under a reply. A note in a
+     run of flush lines keeps --cv-note-gap (below) around it. */
   --cv-reply-room: 0px;
-  --cv-note-gap: 0px;
+  --cv-note-gap: var(--grid-gap-block);
   --cv-status-reply-tail: 0px;
   --cv-tool-gap: var(--grid-gap);
   /* One icon column for every transcript meta row (Leo, 2026-10-31: "YOU GUYS CANNOT FUCKIGN
@@ -1999,7 +2004,8 @@ pre.cv-math-source {
 .cv-tools {
   display: flex;
   flex-direction: column;
-  gap: var(--grid-gap-block);
+  /* Flush lines, 22 apart (--cv-tool-row-height); a note keeps --cv-note-gap around it. */
+  gap: 0;
   margin: 0;
   font-family: var(--cv-font);
   font-size: var(--cv-font-size);
@@ -2181,10 +2187,10 @@ pre.cv-math-source {
   pointer-events: none;
 }
 /* A short interim note folded into a run of calls (turns.ts mergeShortNotes): the agent's words in
-   the run's quiet color, wrapped on the rows' 20px lines, with the plain status gap (12px, the
-   transcript's inner gap) to the tool rows above and below it, as a longer reply between two runs
-   has (Leo, 2026-11-01: "the thoughts in between tool calls probably want a bit more padding").
-   model.ts `activityStepHeight` estimates it with the same numbers (NOTE_LINE, NOTE_GAP). */
+   the run's quiet color, wrapped on the rows' 20px lines, with the block gap (--cv-note-gap, 24) to
+   the flush tool rows above and below it (Leo, 2026-11-01: "the thoughts in between tool calls
+   probably want a bit more padding"). model.ts `activityStepHeight` estimates it with the same
+   numbers (NOTE_LINE, noteGap). */
 .cv-tool-note {
   margin: var(--cv-note-gap) 0;
   line-height: 20px;
@@ -2661,7 +2667,7 @@ button.cv-video-frames__frame:focus-visible {
 .cv-tool-group {
   display: flex;
   flex-direction: column;
-  gap: var(--grid-gap-block);
+  gap: 0;
   margin: 0;
   padding-left: var(--grid-icon-box);
   box-shadow: inset 1px 0 var(--cv-rule);
@@ -3167,7 +3173,7 @@ button.cv-video-frames__frame:focus-visible {
   background: color-mix(in srgb, var(--cv-text) 6%, transparent);
 }
 .cv-received .cv-disclosure__toggle {
-  height: var(--grid-row);
+  height: var(--cv-tool-row-height);
   box-sizing: border-box;
   padding-block: 0;
   padding-inline: 0;
@@ -5380,9 +5386,9 @@ article.acpmux-row:not(:has(> :not(.acpmux-row__gap))) {
 .cv-tool-run {
   display: flex;
   flex-direction: column;
-  gap: var(--grid-gap-block);
+  /* Flush lines, 22 apart (--cv-tool-row-height); a note keeps --cv-note-gap around it. */
+  gap: 0;
 }
-.cv-tool-note { margin: 0; }
 .cv-tool-label {
   display: inline-flex;
   max-width: 100%;

webviews/src/agent-session/acpmux/model.ts

@@ -1,6 +1,7 @@
 import {
   footerAfter,
   gridLength,
+  MARK_STEP,
   rowMark,
   gridScale,
   restBand,
@@ -1094,7 +1095,14 @@ function replyHeight(reply: string): number {
 
 /// The compact tool run rhythm (`conversation.css --cv-tool-row-height` and its run bottom gap).
 const TOOL_RUN_TOP = 0;
-const TOOL_ROW_PT = gridLength("row");
+/// The running turn's live run line (conversation/turns.ts ACTIVITY_LINE), by value: turns.ts imports
+/// this module.
+const ACTIVITY_LINE_KIND = "activityLine";
+/// A step row: a tool run, the live run line, or a one-line row (transcriptGrid.ts MARK_STEP).
+const isStepRow = (row: AcpmuxRow) => row.kind === "activity" || row.kind === ACTIVITY_LINE_KIND || isLineRow(row);
+/// One-line activity rows are 22 apart top to top (design/chat-transcript.md "One-line row pitch",
+/// #29965), `--cv-tool-row-height`.
+const TOOL_ROW_PT = 22;
 const toolRowHeight = () => TOOL_ROW_PT * chromeScale;
 const TOOL_RUN_BOTTOM = 0;
 /// A one-line row that is not a tool run (`isLineRow`) draws one tool row's line, as a one-call run
@@ -1108,12 +1116,12 @@ const lineRow = () => LINE_FRAME + toolRowHeight();
 /// A short interim note folded into a run (conversation.css `.cv-tool-note`): one 20px line with
 /// the plain status gap above and below it.
 const NOTE_LINE = 20;
-/// The room around a note (#30400's --cv-note-gap): 0 on the grid, where the run's block gap between
-/// its lines is the room (conversation.css `.cv-tool-note { margin: 0 }`, foldedRunSteps).
-const NOTE_GAP = 0;
+/// The room above and below a note (#30400's --cv-note-gap): the block gap, since a run's lines are
+/// otherwise flush (conversation.css `.cv-tool-note`).
+const noteGap = () => TRANSCRIPT_BLOCK_GAP * chromeScale;
 function activityStepHeight(item: AcpmuxActivity): number {
   const tool = item.tool;
-  if (!tool) return item.kind === "note" ? NOTE_LINE + 2 * NOTE_GAP : 26;
+  if (!tool) return item.kind === "note" ? NOTE_LINE + 2 * noteGap() : 26;
   // A message to another agent (SendMessage, `acpmux send`, a sub-session's `send_message`) is one
   // line on the tool rows' line (AgentMessageRow.tsx), as every one-line row is.
   if (agentMessage(tool)) return toolRowHeight();
@@ -1163,27 +1171,23 @@ function activityStepHeight(item: AcpmuxActivity): number {
 /// "when I'm seeing all of these agent messages back and forth, that's when it sort of, like, gets
 /// confused").
 function foldedRunSteps(row: AcpmuxRow, groups: readonly ToolGroup[]): number {
-  // `.cv-tools` and `.cv-tool-run` stack their children with the block gap (conversation.css).
+  // `.cv-tools` and `.cv-tool-run` stack their lines flush (conversation.css), 22 apart.
   const stretches = runStretches(row, groups);
-  const children = stretches.reduce((count, stretch) => count + (stretch.fold ? 1 : stretch.groups.length), 0);
   return stretches.reduce(
     (height, stretch) =>
       height +
       (stretch.fold ? toolRowHeight() : stretch.groups.reduce((sum, group) => sum + foldedGroupHeight(group), 0)),
-    Math.max(0, children - 1) * TRANSCRIPT_BLOCK_GAP * chromeScale,
+    0,
   );
 }
 
 /// An entry a folded run keeps on its own line: a group starts closed there (ToolGroupRow.tsx
 /// `folded`), one line, as a sent message's row is (SentMessageLine.tsx); anything else is its calls.
 function foldedGroupHeight(group: ToolGroup): number {
   if (group.type === "group" || group.type === "send") return toolRowHeight();
-  // `.cv-tool-group` stacks its calls with the block gap too.
+  // `.cv-tool-group` lists its calls flush too.
   const items = "items" in group ? group.items : [group.item];
-  return items.reduce(
-    (sum, item) => sum + activityStepHeight(item),
-    Math.max(0, items.length - 1) * TRANSCRIPT_BLOCK_GAP * chromeScale,
-  );
+  return items.reduce((sum, item) => sum + activityStepHeight(item), 0);
 }
 
 /// The prepared texts of those messages, for their estimates; cleared past 256, as a row's are.
@@ -1567,8 +1571,7 @@ function fallbackRowHeight(
     }
     const items = row.items ?? [];
     const steps = items.length
-      ? items.reduce((height, item) => height + activityStepHeight(item), 0) +
-        Math.max(0, items.length - 1) * TRANSCRIPT_BLOCK_GAP * chromeScale
+      ? items.reduce((height, item) => height + activityStepHeight(item), 0)
       : toolRowHeight();
     return finish(TOOL_RUN_TOP + TOOL_RUN_BOTTOM + steps);
   }
@@ -2108,7 +2111,8 @@ export function layoutConversation(
   let prevDrawn = prevDrawnRow(rows, start);
   for (let index = start; index < rows.length; index += 1) {
     const row = rows[index]!;
-    marks[index] = rowMark(row);
+    // A step row (a tool run or a one-line row) joins the step row before it flush (transcriptGap).
+    marks[index] = isStepRow(row) ? MARK_STEP : rowMark(row);
     messages.visit(row, index, previous?.rows[index]);
     if (nextDrawn <= index) {
       nextDrawn = index + 1;

webviews/src/agent-session/acpmux/rowEstimates.test.ts

@@ -24,7 +24,6 @@ import {
 import { turnView } from "./conversation/turns";
 import { COLLAPSED_PROMPT_LINES, PASTE_CHIP_HEIGHT, PROMPT_MORE_HEIGHT } from "./conversation/promptCollapse";
 import { currentChatMetrics } from "./chatDisplay";
-import { gridLength } from "./transcriptGrid";
 
 const reply = (id: string, text: string) => ({ id, version: 1, at: 0, kind: "assistant", text });
 // A footer carries its answer's text, for Copy (conversation/turns.ts), so the estimate never reads it.
@@ -278,7 +277,7 @@ test("another agent's message is one 22px tool line in the one-line rows' frame,
     incoming: { kind: "message", message: { name: "cmux16/glass-lens", text, raw: text } },
   });
   const [short, long] = heightsOf([row("m1", "Draft is up."), row("m2", "Line of the report.\n".repeat(40))]);
-  expect(short).toBe(28);
+  expect(short).toBe(22);
   expect(long).toBe(short);
 });
 
@@ -295,14 +294,14 @@ test("a message this agent sent another one is one 22px tool line in the one-lin
     },
   };
   const [height] = heightsOf([{ id: "s", version: 1, at: 0, kind: "activity", items: [send] }]);
-  expect(height).toBe(2 + 22 + 4);
+  expect(height).toBe(22);
 });
 
 test("a task notice is a tool row's line in the one-line rows' frame", () => {
   const [height] = heightsOf([
     { id: "n", version: 1, at: 0, kind: "user", text: "Task done", incoming: { kind: "notice", text: "Task done" } },
   ]);
-  expect(height).toBe(28);
+  expect(height).toBe(22);
 });
 
 // A waiting steer's Send now leads the existing action row, so it adds no height to a text prompt.
@@ -416,8 +415,9 @@ test("a status row between two replies is estimated under the reply's kept room"
   } else {
     // No reply draws its own action row (a turn's copy lives in its footer). On the grid (grid.md
     // 5.5) the stack's block gap above and below the run centres it, so neither row adds room: the
-    // run is its one 28 row and the reply is as tall as it is over a prompt.
-    expect(step).toBe(gridLength("row"));
+    // run is its one 22 line (design/chat-transcript.md "One-line row pitch") and the reply is as tall
+    // as it is over a prompt.
+    expect(step).toBe(22);
     expect(reply).toBe(overPrompt!);
   }
   expect(alone).toBeGreaterThan(0);
@@ -478,9 +478,9 @@ test("a folded run with messages to other agents is estimated as the lines it dr
   const run = (items: unknown[]) => [
     { id: "run", version: 1, at: 0, kind: "activity", settled: true, foldRun: true, items },
   ];
-  // On the grid a run adds no margin of its own (grid.md 5.5): its lines are 28 rows, stacked with the
-  // block gap `.cv-tools`, `.cv-tool-run` and `.cv-tool-group` draw between them (conversation.css).
-  const lines = (n: number) => n * gridLength("row") + (n - 1) * gridLength("gap-block");
+  // A run adds no margin of its own (grid.md 5.5): its lines are flush 22px lines, one apart top to top
+  // (design/chat-transcript.md "One-line row pitch", #29965).
+  const lines = (n: number) => n * 22;
   // Plain work still folds to its one summary line.
   expect(heightsOf(run([shell("a", "git status"), read]))[0]).toBe(lines(1));
   // A send between two commands: a line each.

webviews/src/agent-session/acpmux/transcriptGrid.ts

@@ -29,6 +29,10 @@ export const MARK_MESSAGE = 2;
 export const MARK_INDICATOR = 3;
 /// A settled turn's footer: no height of its own, its action row laid in the gap under the reply.
 export const MARK_FOOTER = 4;
+/// A step row: a tool run or a one-line activity row (model.ts `isLineRow`). Consecutive step rows
+/// sit flush, one 22px line apart top to top (design/chat-transcript.md "One-line row pitch", #29965);
+/// the block gap is around a run of them only.
+export const MARK_STEP = 5;
 
 type MarkedRow = { kind: string; incoming?: unknown; received?: unknown; text?: string };
 export function rowMark(row: MarkedRow): number {
@@ -46,6 +50,8 @@ export function transcriptGap(previous: number, next: number): number {
   // Waiting for the first output: the indicator right under its prompt takes the block gap.
   if (next === MARK_INDICATOR && previous === MARK_PROMPT) return TRANSCRIPT_BLOCK_GAP;
   if (previous === MARK_PROMPT || next === MARK_PROMPT) return TRANSCRIPT_TURN_GAP;
+  // The live line under a run is one more line of it (#29965): flush too.
+  if (previous === MARK_STEP && (next === MARK_STEP || next === MARK_INDICATOR)) return 0;
   return TRANSCRIPT_BLOCK_GAP;
 }
 

webviews/test/agent-pane-working-counts.test.ts

@@ -258,8 +258,15 @@ await requireBrowserLane("agent-pane-working-counts.test.ts", async () => {
         const box = await line(page).evaluate((node) => {
           const label = node.querySelector(".cv-thinking")!.getBoundingClientRect();
           const row = node.getBoundingClientRect();
-          const style = getComputedStyle(node);
-          const px = (name: string) => parseFloat(style.getPropertyValue(name));
+          // The tokens are var() chains, so resolve each through a probe's height.
+          const px = (name: string) => {
+            const probe = document.createElement("div");
+            probe.style.height = `var(${name})`;
+            node.append(probe);
+            const value = probe.getBoundingClientRect().height;
+            probe.remove();
+            return value;
+          };
           return {
             height: row.height,
             labelLeft: label.left - row.left,

webviews/test/browser/transcript-rhythm.test.ts

@@ -114,7 +114,9 @@ await requireBrowserLane("transcript-rhythm.test.ts", async () => {
               toolIcon,
               chevron,
               copy,
-              gaps: [message.top - header.bottom, group.top - message.bottom, live.top - group.bottom],
+              gaps: [message.top - header.bottom, group.top - message.bottom],
+              // The live line is one more line of the tool run over it: flush (#29965).
+              liveUnderRun: live.top - group.bottom,
               inner: paragraphs[1]!.top - paragraphs[0]!.bottom,
               composerGap: composer.top - live.bottom,
               floating: Boolean(document.querySelector(".acpmux-main[data-dock=float]")),
@@ -140,6 +142,7 @@ await requireBrowserLane("transcript-rhythm.test.ts", async () => {
           if (state.actionMid !== undefined)
             expect(Math.abs(state.actionMid - 12 * scale), "action glyph center in block gap").toBeLessThanOrEqual(0.5);
           for (const gap of state.gaps) expect(Math.abs(gap - 24 * scale), "block gap").toBeLessThanOrEqual(0.5);
+          expect(Math.abs(state.liveUnderRun), "live line flush under its run").toBeLessThanOrEqual(0.5);
           expect(Math.abs(state.inner - 12 * scale), "paragraph gap").toBeLessThanOrEqual(0.5);
           // Over a floating stack the newest line rests the rest gap over it (model.ts REST_GAP, Leo
           // 2026-11-01: "more space between composer and latest messages"); docked in flow, the