diff --git a/ui/src/pages/chat/components/chat-tool-cards.test.ts b/ui/src/pages/chat/components/chat-tool-cards.test.ts
index 5a3b2400959d..103459550748 100644
--- a/ui/src/pages/chat/components/chat-tool-cards.test.ts
+++ b/ui/src/pages/chat/components/chat-tool-cards.test.ts
@@ -6,13 +6,7 @@ import { describe, expect, it, vi } from "vitest";
 vi.mock("../markdown.ts", async (importOriginal) => await importOriginal());
 vi.mock("../tool-display.ts", () => ({
   formatToolDetail: (display: { detail?: string }) => display.detail,
-  resolveToolDisplay: ({
-    name,
-    args,
-  }: {
-    name: string;
-    args?: unknown;
-  }) => {
+  resolveToolDisplay: ({ name, args }: { name: string; args?: unknown }) => {
     const labels: Record<string, string> = {
       sessions_spawn: "Sub-agent",
       skill_workshop: "Skill Workshop",
@@ -39,7 +33,7 @@ import {
   formatCollapsedToolSummaryText,
   isToolErrorOutput,
 } from "../../../lib/chat/tool-cards.ts";
-import { renderToolCard, renderToolCardSidebar } from "./chat-tool-cards.ts";
+import { renderToolCard } from "./chat-tool-cards.ts";
 
 function requireFirstMockArg(
   mock: ReturnType<typeof vi.fn>,
@@ -106,7 +100,6 @@ describe("tool-cards", () => {
     expect(blocks[0]?.querySelector("code")?.textContent).toBe(
       '{\n  "mode": "session",\n  "thread": true\n}',
     );
-    expect(container.querySelector(".chat-tool-card__block-empty")).toBeNull();
   });
 
   it("labels collapsed tool calls with the display summary", () => {
@@ -461,7 +454,7 @@ describe("tool-cards", () => {
     const summaryButton = container.querySelector("button.chat-tool-msg-summary");
     expect(summaryButton?.classList.contains("chat-tool-msg-summary--error")).toBe(true);
     expect(container.querySelector(".chat-tool-msg-summary__error-badge")).not.toBeNull();
-    const expandedCard = container.querySelector(".chat-tool-card--expanded");
+    const expandedCard = container.querySelector(".chat-tool-card");
     expect(expandedCard?.classList.contains("chat-tool-card--error")).toBe(true);
     expect(container.querySelector(".chat-tool-card__status-badge")).not.toBeNull();
   });
@@ -551,71 +544,6 @@ describe("tool-cards", () => {
     expect(container.querySelector(".chat-tool-msg-summary__error-badge")).toBeNull();
   });
 
-  it("does not render View with a checkmark for sidebar cards whose output is an error JSON", () => {
-    const container = document.createElement("div");
-    render(
-      renderToolCardSidebar(
-        {
-          id: "msg:err:sidebar",
-          name: "web_search",
-          outputText: JSON.stringify({
-            error: "missing_brave_api_key",
-            message: "BRAVE_API_KEY is not configured",
-          }),
-        },
-        vi.fn(),
-      ),
-      container,
-    );
-
-    const card = container.querySelector(".chat-tool-card");
-    const action = container.querySelector(".chat-tool-card__action");
-    expect(card?.classList.contains("chat-tool-card--error")).toBe(true);
-    expect(action?.classList.contains("chat-tool-card__action--error")).toBe(true);
-    expect(action?.textContent).toContain("View error");
-    expect(action?.textContent).not.toContain("✓");
-  });
-
-  it("marks Tool not found sidebar output as an error instead of View with a checkmark", () => {
-    const container = document.createElement("div");
-    render(
-      renderToolCardSidebar(
-        {
-          id: "msg:err:sidebar-tool-not-found",
-          name: "Unknown",
-          outputText: "Tool not found",
-        },
-        vi.fn(),
-      ),
-      container,
-    );
-
-    const action = container.querySelector(".chat-tool-card__action");
-    expect(container.querySelector(".chat-tool-card--error")).not.toBeNull();
-    expect(action?.textContent).toContain("View error");
-    expect(action?.textContent).not.toContain("✓");
-  });
-
-  it("marks status-only sidebar output as an error instead of View with a checkmark", () => {
-    const container = document.createElement("div");
-    render(
-      renderToolCardSidebar(
-        {
-          id: "msg:err:sidebar-status",
-          name: "sessions_wait",
-          outputText: JSON.stringify({ status: "timeout" }),
-        },
-        vi.fn(),
-      ),
-      container,
-    );
-
-    const action = container.querySelector(".chat-tool-card__action");
-    expect(container.querySelector(".chat-tool-card--error")).not.toBeNull();
-    expect(action?.textContent).toContain("View error");
-    expect(action?.textContent).not.toContain("✓");
-  });
-
   it("keeps Tool output labelling for successful results", () => {
     const container = document.createElement("div");
     render(
diff --git a/ui/src/pages/chat/components/chat-tool-cards.ts b/ui/src/pages/chat/components/chat-tool-cards.ts
index f4a6628821e9..6eb0ead53a91 100644
--- a/ui/src/pages/chat/components/chat-tool-cards.ts
+++ b/ui/src/pages/chat/components/chat-tool-cards.ts
@@ -21,8 +21,7 @@ import {
 } from "../../../lib/chat/tool-display.ts";
 import type { SidebarContent } from "./chat-sidebar.ts";
 
-const TOOL_PREVIEW_MAX_LINES = 2;
-const TOOL_PREVIEW_MAX_CHARS = 100;
+type FullMessageRequest = NonNullable<SidebarContent["fullMessageRequest"]>;
 
 function formatToolOutputForSidebar(text: string): string {
   if (isMarkdownBlockArtText(text)) {
@@ -40,18 +39,6 @@ function formatToolOutputForSidebar(text: string): string {
   return text;
 }
 
-function getTruncatedPreview(text: string): string {
-  const allLines = text.split("\n");
-  const lines = allLines.slice(0, TOOL_PREVIEW_MAX_LINES);
-  const preview = lines.join("\n");
-  if (preview.length > TOOL_PREVIEW_MAX_CHARS) {
-    return `${preview.slice(0, TOOL_PREVIEW_MAX_CHARS)}…`;
-  }
-  return lines.length < allLines.length ? `${preview}…` : preview;
-}
-
-type FullMessageRequest = NonNullable<SidebarContent["fullMessageRequest"]>;
-
 function renderToolIcon(name: string) {
   return icons[name as IconName] ?? icons.puzzle;
 }
@@ -243,39 +230,22 @@ export function renderRawOutputToggle(text: string) {
         <span class="chat-tool-card__raw-toggle-icon">${icons.chevronDown}</span>
       </button>
       <div class="chat-tool-card__raw-body" hidden>
-        ${renderToolDataBlock({
-          label: "Tool output",
-          text,
-          expanded: true,
-        })}
+        ${renderToolDataBlock({ label: "Tool output", text })}
       </div>
     </div>
   `;
 }
 
-function renderToolDataBlock(params: {
-  label: string;
-  text: string;
-  expanded: boolean;
-  empty?: boolean;
-}) {
-  const { label, text, expanded, empty } = params;
+function renderToolDataBlock(params: { label: string; text: string }) {
+  const { label, text } = params;
   const codeClass = isMarkdownBlockArtText(text) ? "markdown-block-art" : "";
   return html`
-    <div class="chat-tool-card__block ${expanded ? "chat-tool-card__block--expanded" : ""}">
+    <div class="chat-tool-card__block">
       <div class="chat-tool-card__block-header">
         <span class="chat-tool-card__block-icon">${icons.zap}</span>
         <span class="chat-tool-card__block-label">${label}</span>
       </div>
-      ${empty
-        ? html`<div class="chat-tool-card__block-empty muted">${text}</div>`
-        : expanded
-          ? html`<pre
-              class="chat-tool-card__block-content"
-            ><code class=${codeClass}>${text}</code></pre>`
-          : html`<div class="chat-tool-card__block-preview mono">
-              ${getTruncatedPreview(text)}
-            </div>`}
+      <pre class="chat-tool-card__block-content"><code class=${codeClass}>${text}</code></pre>
     </div>
   `;
 }
@@ -437,7 +407,7 @@ export function renderExpandedToolCardContent(
     : nothing;
 
   return html`
-    <div class="chat-tool-card chat-tool-card--expanded ${isError ? "chat-tool-card--error" : ""}">
+    <div class="chat-tool-card ${isError ? "chat-tool-card--error" : ""}">
       <div class="chat-tool-card__header">
         <div class="chat-tool-card__title">
           <span class="chat-tool-card__icon">${renderToolIcon(display.icon)}</span>
@@ -470,7 +440,6 @@ export function renderExpandedToolCardContent(
         ? renderToolDataBlock({
             label: "Tool input",
             text: card.inputText!,
-            expanded: true,
           })
         : nothing}
       ${hasOutput
@@ -479,110 +448,8 @@ export function renderExpandedToolCardContent(
           : renderToolDataBlock({
               label: isError ? "Tool error" : "Tool output",
               text: card.outputText!,
-              expanded: true,
             })
         : nothing}
     </div>
   `;
 }
-
-export function renderToolCardSidebar(
-  card: ToolCard,
-  onOpenSidebar?: (content: SidebarContent) => void,
-  canvasPluginSurfaceUrl?: string | null,
-  embedSandboxMode: EmbedSandboxMode = "scripts",
-  options?: { sessionKey?: string; agentId?: string },
-) {
-  const display = resolveToolDisplay({ name: card.name, args: card.args });
-  const detail = formatToolDetail(display);
-  const preview = card.preview;
-  const hasText = Boolean(card.outputText?.trim());
-  const hasPreview = Boolean(preview);
-  const isError = isToolCardError(card);
-  const fullMessageRequest = buildToolSidebarFullMessageRequest(card, options?.sessionKey);
-  const sidebarContent =
-    preview?.kind === "canvas"
-      ? buildPreviewSidebarContent(preview, card.outputText, { fullMessageRequest })
-      : buildSidebarContent(buildToolCardSidebarContent(card), {
-          fullMessageRequest,
-          rawText: card.outputText ?? null,
-        });
-  const actionContent =
-    sidebarContent ??
-    buildSidebarContent(buildToolCardSidebarContent(card), {
-      fullMessageRequest,
-      rawText: card.outputText ?? null,
-    });
-  const canClick = Boolean(onOpenSidebar);
-  const handleClick = canClick ? () => onOpenSidebar?.(actionContent) : undefined;
-  const isShort = hasText && !hasPreview && (card.outputText?.length ?? 0) <= 240;
-  const showCollapsed = hasText && !hasPreview && !isShort;
-  const showInline = hasText && !hasPreview && isShort;
-  const isEmpty = !hasText && !hasPreview;
-  const statusIcon = isError ? icons.x : icons.check;
-
-  return html`
-    <div
-      class="chat-tool-card ${canClick ? "chat-tool-card--clickable" : ""} ${isError
-        ? "chat-tool-card--error"
-        : ""}"
-      @click=${handleClick}
-      role=${canClick ? "button" : nothing}
-      tabindex=${canClick ? "0" : nothing}
-      @keydown=${canClick
-        ? (e: KeyboardEvent) => {
-            if (e.key !== "Enter" && e.key !== " ") {
-              return;
-            }
-            e.preventDefault();
-            handleClick?.();
-          }
-        : nothing}
-    >
-      <div class="chat-tool-card__header">
-        <div class="chat-tool-card__title">
-          <span class="chat-tool-card__icon">${renderToolIcon(display.icon)}</span>
-          <span>${display.label}</span>
-        </div>
-        ${canClick
-          ? html`<span
-              class="chat-tool-card__action ${isError ? "chat-tool-card__action--error" : ""}"
-              >${isError ? "View error" : hasText || hasPreview ? "View" : ""} ${statusIcon}</span
-            >`
-          : nothing}
-        ${isEmpty && !canClick
-          ? html`<span
-              class="chat-tool-card__status ${isError ? "chat-tool-card__status--error" : ""}"
-              >${statusIcon}</span
-            >`
-          : nothing}
-      </div>
-      ${detail ? html`<div class="chat-tool-card__detail">${detail}</div>` : nothing}
-      ${isEmpty
-        ? html`<div
-            class="chat-tool-card__status-text ${isError
-              ? "chat-tool-card__status-text--error"
-              : "muted"}"
-          >
-            ${isError ? "Failed" : "Completed"}
-          </div>`
-        : nothing}
-      ${preview
-        ? html`${renderToolPreview(preview, "chat_tool", {
-            onOpenSidebar,
-            rawText: card.outputText,
-            canvasPluginSurfaceUrl,
-            embedSandboxMode,
-          })}`
-        : nothing}
-      ${showCollapsed
-        ? html`<div class="chat-tool-card__preview mono">
-            ${getTruncatedPreview(card.outputText!)}
-          </div>`
-        : nothing}
-      ${showInline
-        ? html`<div class="chat-tool-card__inline mono">${card.outputText}</div>`
-        : nothing}
-    </div>
-  `;
-}
diff --git a/ui/src/styles/chat/grouped.css b/ui/src/styles/chat/grouped.css
index 832e7fd0ad23..f566f8a0d7b4 100644
--- a/ui/src/styles/chat/grouped.css
+++ b/ui/src/styles/chat/grouped.css
@@ -225,15 +225,15 @@ img.chat-avatar {
   word-wrap: break-word;
 }
 
-/* Width-only shell: bubble chrome (border/background/padding) comes from
-   .chat-bubble above. */
+/* Tool messages render flat rows, not bubbles: the shell only constrains
+   width; all bubble chrome (border/background/padding) is reset. */
 .chat-bubble--tool-shell {
   align-self: stretch;
   width: min(100%, 760px);
-}
-
-.chat-bubble--tool-shell:hover {
+  padding: 0;
+  border: 0;
   background: transparent;
+  box-shadow: none;
 }
 
 .chat-bubble.has-copy {
@@ -381,10 +381,6 @@ img.chat-avatar {
   box-shadow: 0 0 0 1px color-mix(in srgb, var(--accent) 20%, transparent);
 }
 
-.chat-bubble--tool-shell:hover {
-  background: transparent;
-}
-
 /* User bubbles have different styling */
 .chat-group.user .chat-bubble {
   background: var(--accent-subtle);
@@ -405,6 +401,8 @@ img.chat-avatar {
 }
 
 :root[data-theme-mode="light"] .chat-bubble--tool-shell {
+  border-color: transparent;
+  background: transparent;
   box-shadow: none;
 }
 
diff --git a/ui/src/styles/chat/tool-cards.css b/ui/src/styles/chat/tool-cards.css
index 34bcf18048c9..c66eeccf4e02 100644
--- a/ui/src/styles/chat/tool-cards.css
+++ b/ui/src/styles/chat/tool-cards.css
@@ -1,79 +1,195 @@
-/* Tool Card Styles */
+/* Tool call rendering: flat rows (summary) + inline detail blocks (expanded).
+   Tool rows deliberately carry no card chrome (border/background/shadow) so
+   dense agent activity stays scannable; detail surfaces appear only on expand. */
+
+/* ── Collapsed tool row ── */
+.chat-tool-msg-collapse {
+  width: 100%;
+  min-width: 0;
+  max-width: 100%;
+  margin-top: 2px;
+}
+
+.chat-bubble--tool-shell > .chat-tool-msg-collapse {
+  margin-top: 0;
+}
+
+.chat-tool-msg-summary {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+  min-width: 0;
+  width: 100%;
+  box-sizing: border-box;
+  padding: 4px 8px;
+  cursor: pointer;
+  font-size: var(--control-ui-text-sm);
+  line-height: 1.5;
+  color: var(--muted);
+  user-select: none;
+  list-style: none;
+  border: 0;
+  border-radius: var(--radius-sm);
+  background: transparent;
+  text-align: left;
+  appearance: none;
+  -webkit-appearance: none;
+  font-family: inherit;
+  transition:
+    color 150ms ease,
+    background 150ms ease;
+}
+
+.chat-tool-msg-summary:hover,
+.chat-tool-msg-summary:focus-visible {
+  background: color-mix(in srgb, var(--bg-hover) 60%, transparent);
+  color: var(--text);
+}
+
+.chat-tool-msg-summary::-webkit-details-marker {
+  display: none;
+}
+
+.chat-tool-msg-summary::before {
+  content: "▸";
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 9px;
+  font-size: 12px;
+  line-height: 1;
+  color: var(--muted);
+  opacity: 0.7;
+  flex-shrink: 0;
+  transition: transform 150ms ease;
+}
+
+.chat-tool-msg-summary[aria-expanded="true"]::before {
+  transform: rotate(90deg);
+}
+
+.chat-tool-msg-summary__icon {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 15px;
+  height: 15px;
+  color: var(--muted);
+  flex-shrink: 0;
+}
+
+.chat-tool-msg-summary__icon svg {
+  width: 15px;
+  height: 15px;
+  stroke: currentColor;
+  fill: none;
+  stroke-width: 1.5px;
+  stroke-linecap: round;
+  stroke-linejoin: round;
+}
+
+/* Collapsed rows clamp to one line; the full text is available on expand. */
+.chat-tool-msg-summary__label {
+  flex: 0 1 auto;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  font-weight: 500;
+  color: var(--text);
+}
+
+.chat-tool-msg-summary__names,
+.chat-tool-msg-summary__preview {
+  flex: 1 1 0;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  font-family: var(--mono);
+  font-size: calc(var(--control-ui-text-sm) - 1px);
+  color: color-mix(in srgb, var(--muted) 82%, var(--text) 18%);
+}
+
+.chat-tool-msg-summary--error .chat-tool-msg-summary__icon,
+.chat-tool-msg-summary--error .chat-tool-msg-summary__label {
+  color: var(--destructive, var(--danger, #c0392b));
+}
+
+.chat-tool-msg-summary__error-badge {
+  display: inline-flex;
+  align-items: center;
+  gap: 3px;
+  box-sizing: border-box;
+  padding: 1px 6px;
+  margin-left: auto;
+  border-radius: 999px;
+  background: color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 14%, transparent);
+  color: var(--destructive, var(--danger, #c0392b));
+  font-size: 11px;
+  font-weight: 600;
+  letter-spacing: 0.04em;
+  text-transform: uppercase;
+  line-height: 1.4;
+  flex-shrink: 0;
+}
+
+.chat-tool-msg-summary__error-badge svg {
+  width: 10px;
+  height: 10px;
+  stroke: currentColor;
+  fill: none;
+  stroke-width: 2px;
+  stroke-linecap: round;
+  stroke-linejoin: round;
+}
+
+/* ── Expanded tool row body ── */
+.chat-tool-msg-body {
+  box-sizing: border-box;
+  min-width: 0;
+  max-width: 100%;
+  padding: 2px 8px 8px 24px;
+}
+
+.chat-bubble--tool-shell .chat-tool-msg-body > .chat-text {
+  max-height: min(46vh, 540px);
+  margin: 0;
+  overflow: auto;
+  font-family: var(--mono);
+  font-size: 12px;
+  line-height: 1.55;
+  white-space: pre-wrap;
+  overflow-wrap: anywhere;
+}
+
+/* ── Expanded tool detail ── */
+.chat-tools-inline {
+  display: grid;
+  gap: 2px;
+}
+
 .chat-tool-card {
   box-sizing: border-box;
   min-width: 0;
   max-width: 100%;
-  border: 1px solid var(--border);
-  border-radius: var(--radius-md);
-  padding: 10px 12px;
-  margin-top: 8px;
-  background: var(--secondary);
-  display: grid;
-  gap: 4px;
-  box-shadow: inset 0 1px 0 color-mix(in srgb, var(--bg) 75%, transparent);
-  transition:
-    border-color var(--duration-fast) ease-out,
-    background var(--duration-fast) ease-out,
-    box-shadow var(--duration-fast) ease-out;
-  max-height: 120px;
-  overflow: hidden;
 }
 
-:root[data-theme-mode="light"] .chat-tool-card {
-  background: var(--bg-muted);
-}
-
-.chat-tool-card--expanded {
-  max-height: none;
-  overflow: hidden;
-}
-
-.chat-tool-card:hover {
-  border-color: color-mix(in srgb, var(--border-strong) 80%, transparent);
-  background: color-mix(in srgb, var(--card) 70%, var(--bg-hover) 30%);
-  box-shadow: inset 0 1px 0 color-mix(in srgb, var(--bg) 85%, transparent);
-}
-
-/* First tool card in a group - no top margin */
-.chat-tool-card:first-child {
-  margin-top: 0;
-}
-
-.chat-tool-card--clickable {
-  cursor: pointer;
-}
-
-.chat-tool-card--clickable:focus-visible {
-  outline: 2px solid var(--accent);
-  outline-offset: 2px;
-}
-
-/* Header with title and chevron */
 .chat-tool-card__header {
   display: flex;
   justify-content: space-between;
-  align-items: flex-start;
+  align-items: center;
   gap: 10px;
   min-width: 0;
 }
 
-.chat-tool-card__actions {
-  display: inline-flex;
-  align-items: center;
-  gap: 6px;
-  flex-wrap: wrap;
-  justify-content: flex-end;
-}
-
 .chat-tool-card__title {
   display: inline-flex;
   align-items: center;
   gap: 6px;
   flex: 1 1 auto;
-  font-family: var(--mono);
-  font-weight: 500;
-  font-size: 12px;
-  color: var(--text);
+  font-weight: 600;
+  font-size: var(--control-ui-text-sm);
   line-height: 1.2;
   min-width: 0;
   max-width: 100%;
@@ -86,6 +202,7 @@
   justify-content: center;
   width: 16px;
   height: 16px;
+  color: var(--muted);
   flex-shrink: 0;
 }
 
@@ -99,33 +216,35 @@
   stroke-linejoin: round;
 }
 
-/* "View >" action link */
-.chat-tool-card__action,
+.chat-tool-card__actions {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  justify-content: flex-end;
+}
+
 .chat-tool-card__action-btn {
   display: inline-flex;
   align-items: center;
   justify-content: center;
-  gap: 4px;
-  flex-shrink: 0;
-  font-size: 12px; /* was 11px */
-  white-space: nowrap;
-  color: var(--muted);
-  opacity: 1;
-  transition:
-    color 150ms ease-out,
-    background 150ms ease-out,
-    border-color 150ms ease-out;
-}
-
-.chat-tool-card__action-btn {
-  width: 28px;
-  height: 28px;
+  width: 24px;
+  height: 24px;
   padding: 0;
-  border: 1px solid color-mix(in srgb, var(--border) 80%, transparent);
-  border-radius: 999px;
-  background: color-mix(in srgb, var(--secondary) 55%, transparent);
+  border: 0;
+  border-radius: var(--radius-sm);
+  background: transparent;
+  color: var(--muted);
   cursor: pointer;
   font: inherit;
+  transition:
+    color 150ms ease-out,
+    background 150ms ease-out;
+}
+
+.chat-tool-card__action-btn:hover,
+.chat-tool-card__action-btn:focus-visible {
+  color: var(--text);
+  background: color-mix(in srgb, var(--bg-hover) 70%, transparent);
 }
 
 .chat-tool-card__action-icon {
@@ -135,8 +254,8 @@
 }
 
 .chat-tool-card__action-icon svg {
-  width: 11px;
-  height: 11px;
+  width: 12px;
+  height: 12px;
   stroke: currentColor;
   fill: none;
   stroke-width: 1.5px;
@@ -144,43 +263,6 @@
   stroke-linejoin: round;
 }
 
-.chat-tool-card--clickable:hover .chat-tool-card__action,
-.chat-tool-card__action-btn:hover,
-.chat-tool-card__action-btn:focus-visible {
-  color: var(--text);
-  background: color-mix(in srgb, var(--bg-hover) 70%, transparent);
-  border-color: color-mix(in srgb, var(--border-strong) 70%, transparent);
-}
-
-/* Status indicator for completed/empty results */
-.chat-tool-card__status {
-  display: inline-flex;
-  align-items: center;
-  color: var(--ok);
-}
-
-.chat-tool-card__status svg {
-  width: 14px;
-  height: 14px;
-  stroke: currentColor;
-  fill: none;
-  stroke-width: 2px;
-  stroke-linecap: round;
-  stroke-linejoin: round;
-}
-
-.chat-tool-card__status-text {
-  font-size: var(--control-ui-text-xs);
-  margin-top: 10px;
-}
-
-/* Error state: tool returned an error payload or "Tool not found" */
-.chat-tool-card__status--error,
-.chat-tool-card__action--error,
-.chat-tool-card__status-text--error {
-  color: var(--destructive, var(--danger, #c0392b));
-}
-
 .chat-tool-card__status-badge {
   display: inline-flex;
   align-items: center;
@@ -188,9 +270,9 @@
   padding: 1px 6px;
   margin-left: 6px;
   border-radius: 999px;
-  background: color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 15%, transparent);
+  background: color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 14%, transparent);
   color: var(--destructive, var(--danger, #c0392b));
-  font-size: 12px; /* was 10px */
+  font-size: 11px;
   font-weight: 600;
   letter-spacing: 0.04em;
   text-transform: uppercase;
@@ -207,215 +289,26 @@
   stroke-linejoin: round;
 }
 
-.chat-tool-card--error {
-  border-color: color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 35%, var(--border));
-  background:
-    linear-gradient(
-      90deg,
-      color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 8%, transparent),
-      transparent 36%
-    ),
-    color-mix(in srgb, var(--card) 86%, var(--secondary) 14%);
-}
-
-.chat-tool-card--error:hover {
-  border-color: color-mix(
-    in srgb,
-    var(--destructive, var(--danger, #c0392b)) 44%,
-    var(--border-strong)
-  );
-  background:
-    linear-gradient(
-      90deg,
-      color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 11%, transparent),
-      transparent 38%
-    ),
-    color-mix(in srgb, var(--card) 78%, var(--bg-hover) 22%);
-}
-
-.chat-tool-card--error .chat-tool-card__icon,
-.chat-tool-msg-summary.chat-tool-msg-summary--error .chat-tool-msg-summary__icon {
+.chat-tool-card--error .chat-tool-card__icon {
   color: var(--destructive, var(--danger, #c0392b));
-  opacity: 0.9;
-}
-
-.chat-tool-msg-summary__error-badge {
-  display: inline-flex;
-  align-items: center;
-  align-self: center;
-  gap: 3px;
-  min-height: 20px;
-  box-sizing: border-box;
-  padding: 1px 6px;
-  margin-left: auto;
-  border-radius: 999px;
-  background: color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 15%, transparent);
-  color: var(--destructive, var(--danger, #c0392b));
-  font-size: 12px; /* was 10px */
-  font-weight: 600;
-  letter-spacing: 0.04em;
-  text-transform: uppercase;
-  line-height: 1;
-  flex-shrink: 0;
-}
-
-.chat-tool-msg-summary__error-badge svg {
-  width: 10px;
-  height: 10px;
-  stroke: currentColor;
-  fill: none;
-  stroke-width: 2px;
-  stroke-linecap: round;
-  stroke-linejoin: round;
 }
 
 .chat-tool-card__detail {
-  font-family: var(--mono);
-  font-size: 12px;
+  font-size: var(--control-ui-text-sm);
   color: var(--muted);
-  margin-top: 6px;
-}
-
-/* Collapsed preview - fixed height with truncation */
-.chat-tools-inline {
-  display: grid;
-  gap: 6px;
+  margin-top: 4px;
 }
 
 .chat-tool-card__block {
-  margin-top: 12px;
-  min-width: 0;
-}
-
-.chat-tool-card__preview,
-.chat-tool-card__raw {
-  margin-top: 12px;
-}
-
-.chat-tool-card__preview {
-  border: 1px solid color-mix(in srgb, var(--border) 78%, transparent);
-  border-radius: var(--radius-md);
-  background: color-mix(in srgb, var(--secondary) 78%, transparent);
-  overflow: hidden;
-}
-
-.chat-tool-card__preview-header {
-  display: flex;
-  align-items: center;
-  justify-content: space-between;
-  gap: 10px;
-  padding: 10px 12px;
-  border-bottom: 1px solid color-mix(in srgb, var(--border) 72%, transparent);
-  background: color-mix(in srgb, var(--card) 82%, transparent);
-}
-
-.chat-tool-card__preview-label {
-  font-size: 12px; /* was 11px */
-  font-weight: 600;
-  letter-spacing: 0.04em;
-  text-transform: uppercase;
-  color: var(--muted);
-}
-
-.chat-tool-card__preview-tabs {
-  display: inline-flex;
-  align-items: center;
-  gap: 4px;
-}
-
-.chat-tool-card__preview-tab {
-  border: 1px solid color-mix(in srgb, var(--border) 76%, transparent);
-  background: color-mix(in srgb, var(--bg) 72%, transparent);
-  color: var(--muted);
-  border-radius: 999px;
-  padding: 4px 10px;
-  font: inherit;
-  font-size: 12px;
-  cursor: pointer;
-  transition:
-    color 150ms ease-out,
-    border-color 150ms ease-out,
-    background 150ms ease-out;
-}
-
-.chat-tool-card__preview-tab.is-active,
-.chat-tool-card__preview-tab:hover,
-.chat-tool-card__preview-tab:focus-visible {
-  color: var(--text);
-  border-color: color-mix(in srgb, var(--border-strong) 80%, transparent);
-  background: color-mix(in srgb, var(--card) 92%, transparent);
-}
-
-.chat-tool-card__preview-panel {
-  padding: 12px;
-}
-
-.chat-tool-card__preview-frame {
-  display: block;
-  width: 100%;
-  min-height: 420px;
-  border: 1px solid color-mix(in srgb, var(--border) 68%, transparent);
-  border-radius: var(--radius-md);
-  background: #fff;
-}
-
-.chat-tool-card__raw-toggle {
-  width: 100%;
-  display: inline-flex;
-  align-items: center;
-  justify-content: space-between;
-  gap: 8px;
-  padding: 10px 12px;
-  border: 1px solid color-mix(in srgb, var(--border) 75%, transparent);
-  border-radius: var(--radius-md);
-  background: color-mix(in srgb, var(--secondary) 68%, transparent);
-  color: var(--muted);
-  font: inherit;
-  font-size: 12px;
-  cursor: pointer;
-  transition:
-    color 150ms ease-out,
-    border-color 150ms ease-out,
-    background 150ms ease-out;
-}
-
-.chat-tool-card__raw-toggle:hover,
-.chat-tool-card__raw-toggle:focus-visible {
-  color: var(--text);
-  border-color: color-mix(in srgb, var(--border-strong) 80%, transparent);
-  background: color-mix(in srgb, var(--card) 92%, transparent);
-}
-
-.chat-tool-card__raw-toggle[aria-expanded="true"] .chat-tool-card__raw-toggle-icon {
-  transform: rotate(180deg);
-}
-
-.chat-tool-card__raw-toggle-icon {
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  transition: transform 150ms ease-out;
-}
-
-.chat-tool-card__raw-toggle-icon svg {
-  width: 14px;
-  height: 14px;
-  stroke: currentColor;
-  fill: none;
-  stroke-width: 1.6px;
-  stroke-linecap: round;
-  stroke-linejoin: round;
-}
-
-.chat-tool-card__raw-body {
   margin-top: 8px;
+  min-width: 0;
 }
 
 .chat-tool-card__block-header {
   display: inline-flex;
   align-items: center;
   gap: 6px;
-  margin-bottom: 6px;
+  margin-bottom: 4px;
   color: var(--muted);
 }
 
@@ -438,38 +331,27 @@
 }
 
 .chat-tool-card__block-label {
-  font-size: 12px; /* was 11px */
+  font-size: 11px;
   font-weight: 600;
   letter-spacing: 0.04em;
   text-transform: uppercase;
   color: inherit;
 }
 
-.chat-tool-card__block-preview,
-.chat-tool-card__block-content,
-.chat-tool-card__block-empty {
+.chat-tool-card__block-content {
   box-sizing: border-box;
   max-width: 100%;
   min-width: 0;
   margin: 0;
-  padding: 11px 12px;
-  border-radius: var(--radius-md);
-  border: 1px solid color-mix(in srgb, var(--border) 75%, transparent);
+  padding: 10px 12px;
+  border-radius: var(--radius-sm);
   background: color-mix(in srgb, var(--secondary) 82%, transparent);
-  font-size: 12px; /* was 11px */
+  color: var(--text);
+  font-size: 12px;
   line-height: 1.45;
   white-space: pre-wrap;
   overflow-wrap: anywhere;
   word-break: break-word;
-}
-
-.chat-tool-card__block-preview,
-.chat-tool-card__block-empty {
-  color: var(--muted);
-}
-
-.chat-tool-card__block-content {
-  color: var(--text);
   overflow: auto;
   max-height: min(520px, 60vh);
 }
@@ -499,100 +381,98 @@
   word-break: normal;
 }
 
-.chat-tool-card__inline {
-  margin-top: 10px;
-  white-space: pre-wrap;
-  overflow-wrap: anywhere;
-  word-break: break-word;
+/* ── Canvas/document preview (frames embedded content, so it keeps a border) ── */
+.chat-tool-card__preview,
+.chat-tool-card__raw {
+  margin-top: 8px;
 }
 
-.chat-tool-card__block-preview {
+.chat-tool-card__preview {
+  border: 1px solid color-mix(in srgb, var(--border) 78%, transparent);
+  border-radius: var(--radius-md);
+  background: color-mix(in srgb, var(--secondary) 78%, transparent);
   overflow: hidden;
-  max-height: 52px;
 }
 
-.chat-tools-summary {
+.chat-tool-card__preview-header {
   display: flex;
   align-items: center;
-  gap: 6px;
-  padding: 8px 12px;
-  cursor: pointer;
-  font-size: 12px;
-  font-weight: 500;
+  justify-content: space-between;
+  gap: 10px;
+  padding: 10px 12px;
+  border-bottom: 1px solid color-mix(in srgb, var(--border) 72%, transparent);
+  background: color-mix(in srgb, var(--card) 82%, transparent);
+}
+
+.chat-tool-card__preview-label {
+  font-size: 11px;
+  font-weight: 600;
+  letter-spacing: 0.04em;
+  text-transform: uppercase;
   color: var(--muted);
-  user-select: none;
-  list-style: none;
-  transition:
-    color 150ms ease,
-    background 150ms ease;
 }
 
-.chat-tools-summary::-webkit-details-marker {
-  display: none;
+.chat-tool-card__preview-panel {
+  padding: 12px;
 }
 
-.chat-tools-summary::before {
-  content: "▸";
-  font-size: 12px; /* was 10px */
-  flex-shrink: 0;
-  transition: transform 150ms ease;
+.chat-tool-card__preview-frame {
+  display: block;
+  width: 100%;
+  min-height: 420px;
+  border: 1px solid color-mix(in srgb, var(--border) 68%, transparent);
+  border-radius: var(--radius-md);
+  background: #fff;
 }
 
-.chat-tools-collapse[open] > .chat-tools-summary::before {
-  transform: rotate(90deg);
-}
-
-.chat-tools-summary:hover {
-  color: var(--text);
-  background: color-mix(in srgb, var(--bg-hover) 50%, transparent);
-}
-
-.chat-tools-summary__icon {
+.chat-tool-card__raw-toggle {
   display: inline-flex;
   align-items: center;
-  width: 14px;
-  height: 14px;
-  color: var(--accent);
-  opacity: 0.7;
-  flex-shrink: 0;
+  gap: 6px;
+  padding: 4px 0;
+  border: 0;
+  background: transparent;
+  color: var(--muted);
+  font: inherit;
+  font-size: 12px;
+  cursor: pointer;
+  transition: color 150ms ease-out;
 }
 
-.chat-tools-summary__icon svg {
+.chat-tool-card__raw-toggle:hover,
+.chat-tool-card__raw-toggle:focus-visible {
+  color: var(--text);
+}
+
+.chat-tool-card__raw-toggle[aria-expanded="true"] .chat-tool-card__raw-toggle-icon {
+  transform: rotate(180deg);
+}
+
+.chat-tool-card__raw-toggle-icon {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  transition: transform 150ms ease-out;
+}
+
+.chat-tool-card__raw-toggle-icon svg {
   width: 14px;
   height: 14px;
   stroke: currentColor;
   fill: none;
-  stroke-width: 1.5px;
+  stroke-width: 1.6px;
   stroke-linecap: round;
   stroke-linejoin: round;
 }
 
-.chat-tools-summary__count {
-  font-weight: 600;
-  color: var(--text);
-}
-
-.chat-tools-summary__names {
-  color: var(--muted);
-  font-weight: 400;
-  overflow: hidden;
-  text-overflow: ellipsis;
-  white-space: nowrap;
-}
-
-.chat-tools-collapse__body {
-  padding: 4px 12px 12px;
-  border-top: 1px solid color-mix(in srgb, var(--border) 60%, transparent);
-}
-
-.chat-tools-collapse__body .chat-tool-card:first-child {
-  margin-top: 8px;
+.chat-tool-card__raw-body {
+  margin-top: 4px;
 }
 
+/* ── Inline JSON disclosure ── */
 .chat-json-collapse {
   margin-top: 4px;
-  border: 1px solid color-mix(in srgb, var(--border) 80%, transparent);
-  border-radius: var(--radius-md);
+  border-radius: var(--radius-sm);
   background: color-mix(in srgb, var(--secondary) 60%, transparent);
   overflow: hidden;
 }
@@ -618,7 +498,7 @@
 
 .chat-json-summary::before {
   content: "▸";
-  font-size: 12px; /* was 10px */
+  font-size: 12px;
   flex-shrink: 0;
   transition: transform 150ms ease;
 }
@@ -639,7 +519,7 @@
   border-radius: var(--radius-sm);
   background: color-mix(in srgb, var(--accent) 15%, transparent);
   color: var(--accent);
-  font-size: 12px; /* was 10px */
+  font-size: 11px;
   font-weight: 600;
   text-transform: uppercase;
   letter-spacing: 0.04em;
@@ -649,7 +529,7 @@
 
 .chat-json-label {
   font-family: var(--mono);
-  font-size: 12px; /* was 11px */
+  font-size: 12px;
   overflow: hidden;
   text-overflow: ellipsis;
   white-space: nowrap;
@@ -673,253 +553,109 @@
   font-size: inherit;
 }
 
-.chat-tool-msg-collapse {
-  width: 100%;
+/* ── Activity group (a turn's run of tool rows) ── */
+.chat-group--activity .chat-group-messages {
+  max-width: min(760px, 100%);
+}
+
+.chat-activity-group {
   min-width: 0;
   max-width: 100%;
-  margin-top: 6px;
 }
 
-.chat-bubble--tool-shell > .chat-tool-msg-collapse {
-  margin-top: 0;
-}
-
-.chat-tool-msg-summary {
+.chat-activity-group__summary {
   display: flex;
   align-items: center;
-  align-content: center;
-  flex-wrap: wrap;
-  gap: 12px;
-  min-width: 0;
-  box-sizing: border-box;
-  padding: 8px 11px;
-  cursor: pointer;
-  font-size: var(--control-ui-text-sm);
-  line-height: 1;
-  color: var(--text);
-  user-select: none;
-  list-style: none;
-  border: 1px solid color-mix(in srgb, var(--border) 75%, transparent);
-  border-radius: var(--radius-md);
-  background:
-    linear-gradient(90deg, color-mix(in srgb, var(--accent) 9%, transparent), transparent 34%),
-    color-mix(in srgb, var(--card) 86%, var(--secondary) 14%);
-  box-shadow:
-    inset 0 1px 0 color-mix(in srgb, var(--bg) 76%, transparent),
-    0 8px 22px color-mix(in srgb, black 12%, transparent);
+  gap: 8px;
   width: 100%;
-  text-align: left;
-  appearance: none;
-  -webkit-appearance: none;
-  font-family: inherit;
-  transition:
-    color 150ms ease,
-    background 150ms ease,
-    border-color 150ms ease;
-}
-
-.chat-tool-msg-summary svg,
-.chat-tool-msg-summary__icon {
-  flex-shrink: 0;
-}
-
-.chat-tool-msg-summary span {
-  display: inline-flex;
-  align-items: center;
-  line-height: var(--control-ui-text-sm);
-}
-
-.chat-tool-msg-summary[type="button"] {
-  background:
-    linear-gradient(90deg, color-mix(in srgb, var(--accent) 9%, transparent), transparent 34%),
-    color-mix(in srgb, var(--card) 86%, var(--secondary) 14%);
-}
-
-.chat-tool-msg-summary.chat-tool-msg-summary--error {
-  border-color: color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 30%, var(--border));
-  background:
-    linear-gradient(
-      90deg,
-      color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 11%, transparent),
-      transparent 36%
-    ),
-    color-mix(in srgb, var(--card) 86%, var(--secondary) 14%);
-}
-
-.chat-tool-msg-summary::-webkit-details-marker {
-  display: none;
-}
-
-.chat-tool-msg-summary::before {
-  content: "▸";
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  width: 8px;
-  height: 20px;
-  font-size: 12px; /* was 10px */
-  line-height: 1;
-  flex-shrink: 0;
-  transition: transform 150ms ease;
-}
-
-.chat-tool-msg-collapse--static > .chat-tool-msg-summary::before {
-  display: none;
-}
-
-.chat-tool-msg-collapse--manual.is-open > .chat-tool-msg-summary::before,
-.chat-tool-msg-summary[aria-expanded="true"]::before {
-  transform: rotate(90deg);
-}
-
-.chat-tool-msg-collapse[open] > .chat-tool-msg-summary::before {
-  transform: rotate(90deg);
-}
-
-.chat-tool-msg-summary:hover {
-  color: var(--text);
-  background:
-    linear-gradient(90deg, color-mix(in srgb, var(--accent) 13%, transparent), transparent 38%),
-    color-mix(in srgb, var(--card) 76%, var(--bg-hover) 24%);
-  border-color: color-mix(in srgb, var(--border-strong) 70%, transparent);
-}
-
-.chat-tool-msg-summary.chat-tool-msg-summary--error:hover {
-  background:
-    linear-gradient(
-      90deg,
-      color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 14%, transparent),
-      transparent 38%
-    ),
-    color-mix(in srgb, var(--card) 78%, var(--bg-hover) 22%);
-  border-color: color-mix(
-    in srgb,
-    var(--destructive, var(--danger, #c0392b)) 38%,
-    var(--border-strong)
-  );
-}
-
-.chat-tool-msg-collapse--manual.is-open > .chat-tool-msg-summary,
-.chat-tool-msg-collapse[open] > .chat-tool-msg-summary {
-  border-bottom-right-radius: 0;
-  border-bottom-left-radius: 0;
-}
-
-.chat-tool-msg-summary__icon {
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  align-self: center;
-  width: 18px;
-  height: 18px;
-  color: var(--accent);
-  opacity: 0.75;
-}
-
-.chat-tool-msg-summary__icon svg {
-  width: 18px;
-  height: 18px;
-  stroke: currentColor;
-  fill: none;
-  stroke-width: 1.5px;
-  stroke-linecap: round;
-  stroke-linejoin: round;
-}
-
-.chat-tool-msg-summary__label {
-  align-self: center;
-  min-height: 20px;
-  font-weight: 600;
-  color: var(--text);
-  flex: 0 1 auto;
   min-width: 0;
-  max-width: 100%;
-  overflow: visible;
-  overflow-wrap: anywhere;
-  text-overflow: clip;
-  white-space: normal;
-}
-
-.chat-tool-msg-summary__names,
-.chat-tool-msg-summary__preview {
-  align-self: center;
-  min-height: 20px;
-  font-family: var(--mono);
-  font-size: var(--control-ui-text-sm);
-  transform: translateY(0.8px);
-  color: color-mix(in srgb, var(--text) 76%, var(--muted) 24%);
-  flex: 0 1 auto;
-  max-width: 100%;
-  overflow: visible;
-  overflow-wrap: anywhere;
-  text-overflow: clip;
-  white-space: normal;
-  min-width: 0;
-}
-
-.chat-tool-msg-summary__spacer {
-  flex: 1 1 auto;
-}
-
-.chat-tool-msg-summary__btn {
-  width: 24px;
-  height: 24px;
-  padding: 0;
-  border: 1px solid color-mix(in srgb, var(--border) 70%, transparent);
-  border-radius: 999px;
-  background: color-mix(in srgb, var(--secondary) 55%, transparent);
-  color: var(--muted);
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  cursor: pointer;
-  flex-shrink: 0;
-}
-
-.chat-tool-msg-summary__btn:hover,
-.chat-tool-msg-summary__btn:focus-visible {
-  color: var(--text);
-  background: color-mix(in srgb, var(--bg-hover) 70%, transparent);
-  border-color: color-mix(in srgb, var(--border-strong) 70%, transparent);
-}
-
-.chat-tool-msg-summary__btn svg {
-  width: 11px;
-  height: 11px;
-  stroke: currentColor;
-  fill: none;
-  stroke-width: 1.5px;
-  stroke-linecap: round;
-  stroke-linejoin: round;
-}
-
-.chat-tool-msg-body {
   box-sizing: border-box;
+  padding: 5px 8px;
+  border: 0;
+  border-radius: var(--radius-sm);
+  background: transparent;
+  color: var(--text);
+  font: inherit;
+  text-align: left;
+  cursor: pointer;
+  transition: background 150ms ease;
+}
+
+.chat-activity-group__summary:hover,
+.chat-activity-group__summary:focus-visible {
+  background: color-mix(in srgb, var(--bg-hover) 60%, transparent);
+}
+
+.chat-activity-group__summary--error {
+  color: var(--destructive, var(--danger, #c0392b));
+}
+
+.chat-activity-group__icon,
+.chat-activity-group__badge {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  flex-shrink: 0;
+}
+
+.chat-activity-group__icon {
+  color: var(--muted);
+}
+
+.chat-activity-group__summary--error .chat-activity-group__icon {
+  color: inherit;
+}
+
+.chat-activity-group__icon svg,
+.chat-activity-group__badge svg {
+  width: 14px;
+  height: 14px;
+  fill: none;
+  stroke: currentColor;
+  stroke-width: 1.8px;
+  stroke-linecap: round;
+  stroke-linejoin: round;
+}
+
+.chat-activity-group__label {
+  flex-shrink: 0;
+  font-size: var(--control-ui-text-sm);
+  font-weight: 600;
+  line-height: 1.4;
+}
+
+.chat-activity-group__preview {
+  flex: 1 1 0;
   min-width: 0;
-  max-width: 100%;
-  padding-top: 8px;
-}
-
-.chat-bubble--tool-shell .chat-tool-msg-body {
-  margin-top: 0;
-  padding: 12px 14px 14px;
-  border: 1px solid color-mix(in srgb, var(--border) 75%, transparent);
-  border-top: 0;
-  border-radius: 0 0 var(--radius-md) var(--radius-md);
-  background: color-mix(in srgb, var(--card) 82%, var(--secondary) 18%);
-  box-shadow: inset 0 1px 0 color-mix(in srgb, var(--bg) 68%, transparent);
   overflow: hidden;
+  color: var(--muted);
+  font-size: var(--control-ui-text-sm);
+  line-height: 1.4;
+  text-overflow: ellipsis;
+  white-space: nowrap;
 }
 
-.chat-bubble--tool-shell .chat-tool-msg-body > .chat-text {
-  max-height: min(46vh, 540px);
-  margin: 0;
-  overflow: auto;
-  font-family: var(--mono);
-  font-size: 12px;
-  line-height: 1.55;
-  white-space: pre-wrap;
-  overflow-wrap: anywhere;
+.chat-activity-group__badge {
+  gap: 3px;
+  padding: 2px 6px;
+  border-radius: var(--radius-full);
+  background: color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 14%, transparent);
+  color: var(--destructive, var(--danger, #c0392b));
+  font-size: 11px;
+  font-weight: 650;
+  letter-spacing: 0.04em;
+  line-height: 1;
+  text-transform: uppercase;
+}
+
+/* Left rule groups the rows without wrapping them in another card. */
+.chat-activity-group__body {
+  display: flex;
+  flex-direction: column;
+  gap: 0;
+  margin: 2px 0 0 14px;
+  padding-left: 8px;
+  border-left: 1px solid color-mix(in srgb, var(--border) 85%, transparent);
 }
 
 /* Reading Indicator: bubble chrome and sizing come from .chat-bubble and
@@ -980,149 +716,28 @@
   }
 }
 
-.chat-group--activity .chat-group-messages {
-  max-width: min(760px, 100%);
-}
-
-.chat-activity-group {
-  overflow: hidden;
-  border: 1px solid color-mix(in srgb, var(--border) 75%, transparent);
-  border-radius: var(--radius-md);
-  background: color-mix(in srgb, var(--card) 88%, var(--secondary) 12%);
-}
-
-.chat-activity-group__summary {
-  display: flex;
-  align-items: center;
-  gap: 8px;
-  width: 100%;
-  min-height: 40px;
-  padding: 9px 12px;
-  border: 0;
-  background: transparent;
-  color: var(--text);
-  font: inherit;
-  text-align: left;
-  cursor: pointer;
-}
-
-.chat-activity-group__summary:hover,
-.chat-activity-group__summary:focus-visible {
-  background: color-mix(in srgb, var(--bg-hover) 70%, transparent);
-}
-
-.chat-activity-group__summary--error {
-  color: var(--destructive, var(--danger, #c0392b));
-}
-
-.chat-activity-group__icon,
-.chat-activity-group__badge {
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  flex-shrink: 0;
-}
-
-.chat-activity-group__icon svg,
-.chat-activity-group__badge svg {
-  width: 14px;
-  height: 14px;
-  fill: none;
-  stroke: currentColor;
-  stroke-width: 1.8px;
-  stroke-linecap: round;
-  stroke-linejoin: round;
-}
-
-.chat-activity-group__label {
-  flex-shrink: 0;
-  font-size: var(--control-ui-text-sm);
-  font-weight: 650;
-  line-height: 1.2;
-}
-
-.chat-activity-group__preview {
-  min-width: 0;
-  overflow: hidden;
-  color: var(--muted);
-  font-size: var(--control-ui-text-sm);
-  line-height: 1.2;
-  text-overflow: ellipsis;
-  white-space: nowrap;
-}
-
-.chat-activity-group__badge {
-  gap: 3px;
-  margin-left: auto;
-  padding: 2px 6px;
-  border-radius: var(--radius-full);
-  background: color-mix(in srgb, var(--destructive, var(--danger, #c0392b)) 15%, transparent);
-  color: var(--destructive, var(--danger, #c0392b));
-  font-size: 12px; /* was 10px */
-  font-weight: 650;
-  letter-spacing: 0.04em;
-  line-height: 1;
-  text-transform: uppercase;
-}
-
-.chat-activity-group__body {
-  display: flex;
-  flex-direction: column;
-  gap: 8px;
-  padding: 0 10px 10px;
+@media (pointer: coarse) {
+  .chat-tool-msg-summary,
+  .chat-activity-group__summary {
+    padding-top: 8px;
+    padding-bottom: 8px;
+  }
 }
 
 @media (max-width: 768px) {
-  .chat-tool-card {
-    max-height: 100px;
-  }
-
-  .chat-tool-card--expanded {
-    max-height: none;
-  }
-
-  .chat-tool-card__title {
-    font-size: 12px;
-  }
-
-  .chat-tool-card__preview {
-    padding: 6px 8px;
-    margin-top: 6px;
-    font-size: 12px; /* was 10px */
-    max-height: 36px;
-  }
-
-  .chat-tool-card__detail {
-    font-size: 12px; /* was 11px */
-  }
-
-  .chat-tools-summary {
-    padding: 6px 10px;
-  }
-
-  .chat-tools-collapse__body {
-    padding: 4px 10px 10px;
+  .chat-tool-msg-body {
+    padding-left: 16px;
   }
 
   .chat-json-content {
     padding: 8px 10px;
-    font-size: 12px; /* was 11px */
     max-height: 300px;
   }
 }
 
 @media (max-width: 480px) {
-  .chat-tool-card {
-    max-height: 80px;
-  }
-
-  .chat-tool-card--expanded {
-    max-height: none;
-  }
-
-  .chat-tool-card__preview {
-    padding: 4px 6px;
-    max-height: 28px;
+  .chat-tool-card__block-content {
+    max-height: min(360px, 55vh);
   }
 
   .chat-json-content {
diff --git a/ui/src/styles/components.css b/ui/src/styles/components.css
index 9fc1051cc45b..1bade9093933 100644
--- a/ui/src/styles/components.css
+++ b/ui/src/styles/components.css
@@ -3956,62 +3956,6 @@ td.data-table-key-col {
   }
 }
 
-/* Tool cards: canonical card/title/detail styles live in chat/tool-cards.css;
-   the details/summary/output rules below have no counterpart there. */
-.chat-tool-card__details {
-  margin-top: 6px;
-}
-
-.chat-tool-card__summary {
-  font-family: var(--mono);
-  font-size: 12px; /* was 11px */
-  color: var(--muted);
-  cursor: pointer;
-  list-style: none;
-  display: inline-flex;
-  align-items: center;
-  gap: 6px;
-}
-
-.chat-tool-card__summary::-webkit-details-marker {
-  display: none;
-}
-
-.chat-tool-card__summary-meta {
-  color: var(--muted);
-  opacity: 0.7;
-}
-
-.chat-tool-card__details[open] .chat-tool-card__summary {
-  color: var(--text);
-}
-
-.chat-tool-card__output {
-  margin-top: 8px;
-  font-family: var(--mono);
-  font-size: 12px; /* was 11px */
-  line-height: 1.5;
-  white-space: pre-wrap;
-  color: var(--chat-text);
-  padding: 8px 10px;
-  border-radius: var(--radius-md);
-  border: 1px solid var(--border);
-  background: var(--card);
-}
-
-:root[data-theme-mode="light"] .chat-tool-card__output {
-  background: var(--bg);
-}
-
-.chat-stamp {
-  font-size: 12px; /* was 11px */
-  color: var(--muted);
-}
-
-.chat-line.user .chat-stamp {
-  text-align: right;
-}
-
 /* ===========================================
    QR Code
    =========================================== */