feat: collapse MCP tool results by default (#23568)

Wraps the `GenericToolRenderer` (used for MCP and unrecognized tools) in
`ToolCollapsible` so the result content is hidden behind a
click-to-expand chevron, matching the pattern used by `read_file`,
`write_file`, and other built-in tool renderers.

### Changes

- Move `ToolIcon` + `ToolLabel` into the `ToolCollapsible` `header` prop
- Compute `hasContent` from `writeFileDiff` / `fileContent` /
`resultOutput` — when there's no content, the header renders as a plain
div with no chevron
- Remove `ml-6` from `ScrollArea` classNames (the `ToolCollapsible`
button handles its own layout)
- `defaultExpanded` is `false` by default in `ToolCollapsible`, so
results start collapsed

### Before

MCP tool results were always fully visible inline.

### After

MCP tool results are collapsed by default with a chevron toggle,
consistent with `read_file`, `edit_files`, `list_templates`, etc.

site/src/components/ai-elements/tool.stories.tsx

@@ -1,5 +1,5 @@
 import type { Meta, StoryObj } from "@storybook/react-vite";
-import { expect, spyOn, userEvent, within } from "storybook/test";
+import { expect, spyOn, userEvent, waitFor, within } from "storybook/test";
 import { reactRouterParameters } from "storybook-addon-remix-react-router";
 import { Tool } from "./tool";
 
@@ -469,6 +469,187 @@ export const TaskNameGenericRendering: Story = {
 	},
 };
 
+// ---------------------------------------------------------------------------
+// MCP tool stories (generic renderer with MCP server context)
+// ---------------------------------------------------------------------------
+
+const sampleMCPServers = [
+	{
+		id: "mcp-server-1",
+		slug: "linear",
+		display_name: "Linear",
+		description: "Project management",
+		icon_url: "https://linear.app/favicon.ico",
+		transport: "streamable_http",
+		url: "https://mcp.linear.app",
+		auth_type: "oauth2",
+		has_oauth2_secret: false,
+		has_api_key: false,
+		has_custom_headers: false,
+		tool_allow_list: [],
+		tool_deny_list: [],
+		availability: "default_on",
+		enabled: true,
+		auth_connected: true,
+		created_at: "2025-01-01T00:00:00Z",
+		updated_at: "2025-01-01T00:00:00Z",
+	},
+] satisfies readonly import("api/typesGenerated").MCPServerConfig[];
+
+export const MCPToolRunning: Story = {
+	args: {
+		name: "linear__list_issues",
+		status: "running",
+		args: { project: "backend" },
+		mcpServerConfigId: "mcp-server-1",
+		mcpServers: sampleMCPServers,
+	},
+	play: async ({ canvasElement }) => {
+		// Spinner should be visible while running.
+		expect(canvasElement.querySelector(".animate-spin")).not.toBeNull();
+		// Icon should be monochrome (brightness-0 filter).
+		const icon = canvasElement.querySelector(".brightness-0");
+		expect(icon).not.toBeNull();
+	},
+};
+
+export const MCPToolCompleted: Story = {
+	args: {
+		name: "linear__list_issues",
+		status: "completed",
+		args: { project: "backend" },
+		result: {
+			issues: [
+				{ id: "LIN-123", title: "Fix auth flow" },
+				{ id: "LIN-456", title: "Update dashboard" },
+			],
+		},
+		mcpServerConfigId: "mcp-server-1",
+		mcpServers: sampleMCPServers,
+	},
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+		// No spinner when completed.
+		expect(canvasElement.querySelector(".animate-spin")).toBeNull();
+		// Icon should still be monochrome when completed.
+		expect(canvasElement.querySelector(".brightness-0")).not.toBeNull();
+		// Result should be collapsed by default.
+		const toggle = canvas.getByRole("button");
+		expect(toggle).toBeInTheDocument();
+		// Expand to see result content.
+		await userEvent.click(toggle);
+		// @pierre/diffs renders inside a Shadow DOM (<diffs-container>)
+		// so textContent on the host element can't see the content.
+		// Query into the shadow root to verify the JSON rendered.
+		await waitFor(() => {
+			const shadow = canvasElement.querySelector("diffs-container")?.shadowRoot;
+			expect(shadow?.textContent).toContain("Fix auth flow");
+		});
+	},
+};
+
+export const MCPToolError: Story = {
+	args: {
+		name: "linear__list_issues",
+		status: "error",
+		isError: true,
+		args: { project: "backend" },
+		result: { error: "Authentication token expired" },
+		mcpServerConfigId: "mcp-server-1",
+		mcpServers: sampleMCPServers,
+	},
+	play: async ({ canvasElement }) => {
+		// Error alert icon should be present.
+		expect(canvasElement.querySelector(".lucide-circle-alert")).not.toBeNull();
+		// Label text should use the destructive color.
+		const label = canvasElement.querySelector(
+			".\\[\\&\\>\\*\\]\\:text-content-destructive",
+		);
+		expect(label).not.toBeNull();
+	},
+};
+
+export const MCPToolNoResult: Story = {
+	args: {
+		name: "linear__create_issue",
+		status: "completed",
+		args: { title: "New issue" },
+		mcpServerConfigId: "mcp-server-1",
+		mcpServers: sampleMCPServers,
+	},
+	play: async ({ canvasElement }) => {
+		// No toggle button when there is no result content.
+		expect(canvasElement.querySelector("button")).toBeNull();
+	},
+};
+
+export const MCPToolSlackIcon: Story = {
+	args: {
+		name: "slack__post_message",
+		status: "completed",
+		result: { ok: true, channel: "#general" },
+		mcpServerConfigId: "mcp-server-1",
+		mcpServers: [
+			{
+				...sampleMCPServers[0],
+				slug: "slack",
+				display_name: "Slack",
+				icon_url:
+					"https://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Slack_icon_2019.svg/500px-Slack_icon_2019.svg.png",
+			},
+		],
+	},
+};
+
+export const MCPToolGitHubIcon: Story = {
+	args: {
+		name: "github__list_prs",
+		status: "completed",
+		result: { prs: [{ id: 1, title: "Fix bug" }] },
+		mcpServerConfigId: "mcp-server-1",
+		mcpServers: [
+			{
+				...sampleMCPServers[0],
+				slug: "github",
+				display_name: "GitHub",
+				icon_url:
+					"https://upload.wikimedia.org/wikipedia/commons/9/91/Octicons-mark-github.svg",
+			},
+		],
+	},
+};
+
+export const MCPToolFigmaIcon: Story = {
+	args: {
+		name: "figma__get_file",
+		status: "completed",
+		result: { file: "design.fig" },
+		mcpServerConfigId: "mcp-server-1",
+		mcpServers: [
+			{
+				...sampleMCPServers[0],
+				slug: "figma",
+				display_name: "Figma",
+				icon_url:
+					"https://upload.wikimedia.org/wikipedia/commons/3/33/Figma-logo.svg",
+			},
+		],
+	},
+};
+
+export const MCPToolNoServer: Story = {
+	args: {
+		name: "some_custom_tool",
+		status: "completed",
+		result: { output: "Tool finished successfully" },
+	},
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+		// Falls through to generic wrench icon + raw tool name.
+		expect(canvas.getByText("some_custom_tool")).toBeInTheDocument();
+	},
+};
+
 // ---------------------------------------------------------------------------
 // WriteFile stories
 // ---------------------------------------------------------------------------

site/src/components/ai-elements/tool/Tool.tsx

@@ -1,9 +1,15 @@
 import { useTheme } from "@emotion/react";
 import { FileDiff, File as FileViewer } from "@pierre/diffs/react";
 import type * as TypesGen from "api/typesGenerated";
+import { CircleAlertIcon, LoaderIcon } from "lucide-react";
 import { type ComponentPropsWithRef, type FC, memo } from "react";
 import { cn } from "utils/cn";
 import { ScrollArea } from "#/components/ScrollArea/ScrollArea";
+import {
+	Tooltip,
+	TooltipContent,
+	TooltipTrigger,
+} from "#/components/Tooltip/Tooltip";
 import { ChatSummarizedTool } from "./ChatSummarizedTool";
 import { ComputerTool } from "./ComputerTool";
 import { CreateWorkspaceTool } from "./CreateWorkspaceTool";
@@ -19,6 +25,7 @@ import { ProposePlanTool } from "./ProposePlanTool";
 import { ReadFileTool } from "./ReadFileTool";
 import { ReadTemplateTool } from "./ReadTemplateTool";
 import { SubagentTool } from "./SubagentTool";
+import { ToolCollapsible } from "./ToolCollapsible";
 import { ToolIcon } from "./ToolIcon";
 import { ToolLabel } from "./ToolLabel";
 import {
@@ -480,24 +487,50 @@ const GenericToolRenderer: FC<ToolRendererProps> = ({
 		? mcpServers?.find((s) => s.id === mcpServerConfigId)
 		: undefined;
 
+	const hasContent = Boolean(writeFileDiff || fileContent || resultOutput);
+	const isRunning = status === "running";
+	const rec = asRecord(result);
+	const errorMessage = rec ? asString(rec.error || rec.message) : "";
+
 	return (
-		<>
-			<div className="flex items-center gap-2">
-				<ToolIcon
-					name={name}
-					isError={status === "error" || isError}
-					iconUrl={mcpServer?.icon_url}
-				/>
-				<ToolLabel
-					name={name}
-					args={args}
-					result={result}
-					mcpSlug={mcpServer?.slug}
-				/>
-			</div>
+		<ToolCollapsible
+			hasContent={hasContent}
+			header={
+				<>
+					<ToolIcon
+						name={name}
+						isError={status === "error" || isError}
+						iconUrl={mcpServer?.icon_url}
+						isRunning={isRunning}
+						serverName={mcpServer?.display_name}
+					/>
+					<span className={cn(isError && "[&>*]:text-content-destructive")}>
+						<ToolLabel
+							name={name}
+							args={args}
+							result={result}
+							mcpSlug={mcpServer?.slug}
+						/>
+					</span>
+					{isError && (
+						<Tooltip>
+							<TooltipTrigger asChild>
+								<CircleAlertIcon className="h-3.5 w-3.5 shrink-0 text-content-destructive" />
+							</TooltipTrigger>
+							<TooltipContent>
+								{errorMessage || "Tool call failed"}
+							</TooltipContent>
+						</Tooltip>
+					)}
+					{isRunning && (
+						<LoaderIcon className="h-3.5 w-3.5 shrink-0 animate-spin motion-reduce:animate-none text-content-secondary" />
+					)}
+				</>
+			}
+		>
 			{writeFileDiff ? (
 				<ScrollArea
-					className="mt-1.5 ml-6 rounded-md border border-solid border-border-default text-2xs"
+					className="mt-1.5 rounded-md border border-solid border-border-default text-2xs"
 					viewportClassName="max-h-64"
 					scrollBarClassName="w-1.5"
 				>
@@ -509,7 +542,7 @@ const GenericToolRenderer: FC<ToolRendererProps> = ({
 				</ScrollArea>
 			) : fileContent ? (
 				<ScrollArea
-					className="mt-1.5 ml-6 rounded-md border border-solid border-border-default text-2xs"
+					className="mt-1.5 rounded-md border border-solid border-border-default text-2xs"
 					viewportClassName="max-h-64"
 					scrollBarClassName="w-1.5"
 				>
@@ -524,7 +557,7 @@ const GenericToolRenderer: FC<ToolRendererProps> = ({
 			) : (
 				resultOutput && (
 					<ScrollArea
-						className="mt-1.5 ml-6 rounded-md border border-solid border-border-default text-2xs"
+						className="mt-1.5 rounded-md border border-solid border-border-default text-2xs"
 						viewportClassName="max-h-64"
 						scrollBarClassName="w-1.5"
 					>
@@ -539,7 +572,7 @@ const GenericToolRenderer: FC<ToolRendererProps> = ({
 					</ScrollArea>
 				)
 			)}
-		</>
+		</ToolCollapsible>
 	);
 };
 

site/src/components/ai-elements/tool/ToolIcon.tsx

@@ -12,34 +12,72 @@ import type React from "react";
 import { useState } from "react";
 import { cn } from "utils/cn";
 import { ExternalImage } from "#/components/ExternalImage/ExternalImage";
+import {
+	Tooltip,
+	TooltipContent,
+	TooltipTrigger,
+} from "#/components/Tooltip/Tooltip";
 
 export const ToolIcon: React.FC<{
 	name: string;
 	isError: boolean;
 	iconUrl?: string;
-}> = ({ name, isError, iconUrl }) => {
+	isRunning?: boolean;
+	serverName?: string;
+}> = ({ name, isError, iconUrl, isRunning, serverName }) => {
 	const [imgError, setImgError] = useState(false);
 	const color = isError ? "text-content-destructive" : "text-content-secondary";
-	const base = cn("h-4 w-4 shrink-0", color);
+	const base = cn("h-4 w-4 shrink-0", color, isRunning && "grayscale");
 
 	// If an MCP icon URL is provided and hasn't failed, render it.
+	// Strip colour so external icons match the monochrome lucide
+	// style. brightness-0 forces every pixel to black, then in dark
+	// mode we invert to white and tune opacity to approximate
+	// content-secondary (light ≈ 34% lightness, dark ≈ 65%).
 	if (iconUrl && !imgError) {
-		return (
-			<div
-				className={cn(
-					"flex h-4 w-4 shrink-0 items-center justify-center",
-					"rounded-full bg-surface-secondary",
-					isError && "ring-1 ring-content-destructive",
-				)}
-			>
+		// Always render the same DOM shape so React never unmounts
+		// the <img> when isError changes (avoids a reload flicker).
+		//
+		// The wrapper clips a translated copy of the image so the
+		// drop-shadow trick can work on error (see image classes).
+		// In the normal state the image is not translated and the
+		// wrapper's overflow-hidden is a harmless no-op.
+		const img = (
+			<div className="h-4 w-4 shrink-0 overflow-hidden">
 				<ExternalImage
 					src={iconUrl}
 					alt={`${name} icon`}
-					className="h-3 w-3"
+					className={cn(
+						"block h-4 w-4",
+						isError
+							? // Drop-shadow recolor: brightness-0 makes every
+								// pixel black, drop-shadow casts an exact-color
+								// copy 16px to the right following the alpha
+								// channel, -translate-x-4 shifts the colored copy
+								// into the original position, and the wrapper's
+								// overflow-hidden clips the black original.
+								"-translate-x-4 [filter:brightness(0)_drop-shadow(16px_0_0_hsl(var(--content-destructive)))]"
+							: // Monochrome: brightness-0 strips colour to black,
+								// dark:invert flips to white for dark backgrounds,
+								// opacity tuned per-theme to match content-secondary
+								// (light ~35% lightness, dark ~65%).
+								"brightness-0 opacity-[0.35] dark:invert dark:opacity-[0.65]",
+					)}
 					onError={() => setImgError(true)}
 				/>
 			</div>
 		);
+
+		if (serverName) {
+			return (
+				<Tooltip>
+					<TooltipTrigger asChild>{img}</TooltipTrigger>
+					<TooltipContent>{serverName}</TooltipContent>
+				</Tooltip>
+			);
+		}
+
+		return img;
 	}
 
 	switch (name) {