fix(web): stop tool-group flashing and config-menu closure on updates

Reuse existing tool-group DOM elements in rebuildTranscript instead of
tearing them down — preserves CSS transition state and focus. Defer
config-menu DOM rebuild while the menu is open so <select> dropdowns
survive background state updates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/STRUCTURED-VIEW.md

@@ -193,10 +193,13 @@ choices, not daemon ones.
   one collapsed turn activity block. `AgentText` and `AgentThought` rows that
   appear *between* tool rows in the same turn are absorbed into the group
   (intermediate narration); the last `AgentText` with no subsequent tool stays
-  outside as the prominent final answer. The header still reads
-  "N tool calls" (counting only tool rows). Opening the group reveals tools
-  and intermediate text in chronological order, with the text rendered in a
-  subdued style.
+  outside as the prominent final answer. While a turn is still active
+  (responding or thinking), the most recent intermediate `AgentText` or
+  `AgentThought` in the group is kept outside as visible narration — replaced
+  by the next text row when one arrives, and absorbed into the group when the
+  turn ends. The header still reads "N tool calls" (counting only tool rows).
+  Opening the group reveals tools and intermediate text in chronological
+  order, with the text rendered in a subdued style.
 - The web client's user, agent, thought, tool-detail, and notice text blocks
   copy their complete source text when clicked or keyboard-activated.
 - The web client consumes `available_commands_update` notices as the live

web/src/structured.test.ts

@@ -446,6 +446,40 @@ describe("structured connection: data flow", () => {
     conn.dispose();
   });
 
+  it("keeps last intermediate text outside group while turn is active", () => {
+    const ws = new FakeSocket();
+    const conn = mount({ sockets: [ws] });
+    ws.open();
+    const respondingState: ReducedState = {
+      turn: { responding: true, thinking: false, active_tool_calls: [] },
+    };
+    ws.emit({
+      type: "transcript_snapshot",
+      snapshot: {
+        cursor: 6,
+        rows: [
+          row("user:1", "user", { content: { type: "text", text: "do it" } }),
+          toolRow("tool:1", "one"),
+          row("agent:1", "agent_text", { content: { type: "text", text: "Now fixing" } }),
+          toolRow("tool:2", "two"),
+          row("agent:2", "agent_text", { content: { type: "text", text: "Found more" } }),
+          toolRow("tool:3", "three"),
+        ],
+      },
+    });
+    ws.emit({ type: "reduced_state", state: respondingState });
+    // While the turn is active, the last intermediate text (agent:2) stays
+    // outside the collapsed group so it's visible as current narration.
+    expect(conn.el.querySelector('[data-row-id="agent:2"]')?.closest(".st-tool-group")).toBeNull();
+    // Earlier intermediate text (agent:1) is still inside the group.
+    expect(conn.el.querySelector('[data-row-id="agent:1"]')?.closest(".st-tool-group")).not.toBeNull();
+    // When the turn ends, all intermediate text is absorbed.
+    ws.emit({ type: "reduced_state", state: idleState });
+    expect(conn.el.querySelector('[data-row-id="agent:2"]')?.closest(".st-tool-group")).not.toBeNull();
+    expect(conn.el.querySelector('[data-row-id="agent:1"]')?.closest(".st-tool-group")).not.toBeNull();
+    conn.dispose();
+  });
+
   it("keeps an expanded running tool open without emitting a click when patched", () => {
     const ws = new FakeSocket();
     const conn = mount({ sockets: [ws] });

web/src/structured.ts

@@ -85,10 +85,10 @@ export function createStructuredConnection(
       <div class="structured-main">
         <div class="structured-scroll">
           <div class="structured-rows"></div>
-        </div>
-        <div class="structured-activity" role="status" aria-live="polite" hidden>
-          <span class="structured-activity-pulse" aria-hidden="true"></span>
-          <span class="structured-activity-text">Thinking</span>
+          <div class="structured-activity" role="status" aria-live="polite" hidden>
+            <span class="structured-activity-pulse" aria-hidden="true"></span>
+            <span class="structured-activity-text">Thinking</span>
+          </div>
         </div>
         <form class="structured-composer">
           <button type="button" class="btn btn-ghost btn-icon structured-attach" aria-label="Attach files" title="Attach files (up to 20 MiB each)">
@@ -453,6 +453,25 @@ export function createStructuredConnection(
       }
     }
     // pending at end of a turn = final text/approvals, stays outside (not flushed).
+
+    // While the turn is still active, keep the last intermediate text/thought
+    // row outside the collapsed group so it's visible as the agent's current
+    // narration. It gets absorbed on the next rebuild once newer content
+    // arrives or the turn ends.
+    const turnActive = state.turn.responding || state.turn.thinking;
+    if (turnActive) {
+      const lastGroup = groups.get(currentGid);
+      if (lastGroup) {
+        for (let i = lastGroup.rows.length - 1; i >= 0; i--) {
+          const kind = lastGroup.rows[i].kind;
+          if (kind === "agent_text" || kind === "agent_thought") {
+            lastGroup.rows.splice(i, 1);
+            break;
+          }
+        }
+      }
+    }
+
     return groups;
   }
 
@@ -467,6 +486,7 @@ export function createStructuredConnection(
     const liveGroupIds = new Set([...groups.keys()]);
     for (const id of expandedGroupIds) if (!liveGroupIds.has(id)) expandedGroupIds.delete(id);
 
+    const prevGroupEls = new Map(groupEls);
     rowEls.clear();
     groupEls.clear();
     const children: HTMLElement[] = [];
@@ -485,23 +505,37 @@ export function createStructuredConnection(
           rowEls.set(memberRow.id, memberEl);
           return [memberEl];
         });
-        const groupEl = buildToolGroup(
-          groupId,
-          group.rows,
-          memberEls,
-          expandedGroupIds.has(groupId),
-          (expanded) => {
-            if (expanded) expandedGroupIds.add(groupId);
-            else expandedGroupIds.delete(groupId);
-            settleDisclosureLayout();
-          },
-          group.toolCount,
-        );
-        if (group.rows.some((r) => enteringRowIds.has(r.id))) {
-          groupEl.classList.add("st-row-enter");
+
+        // Reuse existing group element when possible — avoids tearing down
+        // and recreating the wrapper, which restarts CSS transitions (visible
+        // flash) and destroys keyboard/focus state.
+        const existing = prevGroupEls.get(groupId);
+        if (existing) {
+          const titleEl = existing.querySelector<HTMLElement>(".st-tool-group-title");
+          if (titleEl) titleEl.textContent = `${group.toolCount} tool calls`;
+          const inner = existing.querySelector<HTMLElement>(".st-disclosure-inner");
+          if (inner) inner.replaceChildren(...memberEls);
+          groupEls.set(groupId, existing);
+          children.push(existing);
+        } else {
+          const groupEl = buildToolGroup(
+            groupId,
+            group.rows,
+            memberEls,
+            expandedGroupIds.has(groupId),
+            (expanded) => {
+              if (expanded) expandedGroupIds.add(groupId);
+              else expandedGroupIds.delete(groupId);
+              settleDisclosureLayout();
+            },
+            group.toolCount,
+          );
+          if (group.rows.some((r) => enteringRowIds.has(r.id))) {
+            groupEl.classList.add("st-row-enter");
+          }
+          groupEls.set(groupId, groupEl);
+          children.push(groupEl);
         }
-        groupEls.set(groupId, groupEl);
-        children.push(groupEl);
         continue;
       }
       // Resolved approvals not absorbed into a tool group are hidden — the
@@ -616,12 +650,14 @@ export function createStructuredConnection(
     }
   }
 
+  let configDirty = false;
   function renderConfig(): void {
     const options = sessionConfigOptions();
     configEl.hidden = options.length === 0;
     if (options.length === 0) {
       configMenu.hidden = true;
       configTrigger.setAttribute("aria-expanded", "false");
+      configDirty = false;
       return;
     }
     const ordered = [...options].sort((a, b) => {
@@ -635,6 +671,15 @@ export function createStructuredConnection(
     configTrigger.title = summary;
     configTrigger.setAttribute("aria-label", `Session settings. ${summary.replaceAll("\n", ". ")}`);
     configTrigger.disabled = configBusy;
+
+    // When the menu is open and the user is interacting (not mid-change),
+    // skip the DOM rebuild so open <select> dropdowns aren't destroyed.
+    // Mark dirty so the next open rebuilds with fresh data.
+    if (!configMenu.hidden && !configBusy) {
+      configDirty = true;
+      return;
+    }
+    configDirty = false;
     configMenu.replaceChildren();
     for (const option of ordered) {
       const row = document.createElement("label");
@@ -698,6 +743,7 @@ export function createStructuredConnection(
 
   function renderActivity(): void {
     const active = state.turn.responding || state.turn.thinking || awaitingBeginGeneration !== null;
+    const wasHidden = activityEl.hidden;
     activityEl.hidden = !active;
     if (!active) {
       optimisticTurnStartedAt = null;
@@ -720,6 +766,11 @@ export function createStructuredConnection(
     }
     activityText.textContent = parts.join(" · ");
     if (activityTimer === null) activityTimer = window.setInterval(renderActivity, 1_000);
+    // Activity lives inside the scroll area; nudge scroll when it first appears.
+    if (wasHidden && followingBottom) {
+      beginTranscriptLayout(true);
+      finishTranscriptLayout();
+    }
   }
 
   function reconcileAwaitingBegin(): void {
@@ -735,15 +786,17 @@ export function createStructuredConnection(
   }
 
   function applyState(next: ReducedState, connectionGeneration: number): void {
+    const wasTurnActive = state.turn.responding || state.turn.thinking;
     state = next;
     stateSocketGeneration = connectionGeneration;
     reconcileAwaitingBegin();
+    const isTurnActive = state.turn.responding || state.turn.thinking;
     const newPendingId = state.pending_approval ? lastRowIdOfKind("approval") : null;
-    if (newPendingId !== pendingApprovalRowId) {
+    const needsRebuild = newPendingId !== pendingApprovalRowId || wasTurnActive !== isTurnActive;
+    if (needsRebuild) {
       updateTranscriptLayout(() => {
-        const prev = pendingApprovalRowId;
         pendingApprovalRowId = newPendingId;
-        if (prev !== null || newPendingId !== null) rebuildTranscript();
+        rebuildTranscript();
       });
     }
     renderConfig();
@@ -758,6 +811,7 @@ export function createStructuredConnection(
 
   configTrigger.addEventListener("click", () => {
     const opening = configMenu.hidden;
+    if (opening && configDirty) renderConfig();
     configMenu.hidden = !opening;
     configTrigger.setAttribute("aria-expanded", String(opening));
   });

web/src/styles.css

@@ -2318,9 +2318,7 @@ input.leaf-rename:focus {
   gap: var(--sp-2);
   min-height: 30px;
   padding: var(--sp-1) var(--sp-3);
-  border-top: 1px solid var(--border);
   color: var(--muted);
-  background: var(--surface-2);
   font-size: var(--fs-11);
   font-variant-numeric: tabular-nums;
 }