@@ -4,9 +4,18 @@ import * as p from "@clack/prompts";
 import { cancelable, spinnerify } from "@solid-cli/utils/ui";
 import { createStart } from "./create-start";
 import { createSolidV2 } from "./create-solid-v2";
-import { GIT_IGNORE, isValidTemplate, LIBRARY_TEMPLATES, PROJECT_TYPES, ProjectType } from "./utils/constants";
+import {
+	GIT_IGNORE,
+	isValidTemplate,
+	LIBRARY_TEMPLATES,
+	PROJECT_TYPES,
+	ProjectType,
+	START_DEVTOOLS_PACKAGE,
+	START_DEVTOOLS_VERSION,
+} from "./utils/constants";
 import { fetchTemplatesManifest, groupKeyFor, ManifestTemplate, resolveGroup } from "./utils/manifest";
 import { fuzzyScore, rankedOptionsFn } from "./utils/fuzzy";
+import { addDevDependency } from "./utils/dev-deps";
 import { detectPackageManager } from "@solid-cli/utils/package-manager";
 import { existsSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
@@ -84,6 +93,11 @@ export const createSolid = (version: string) =>
 				required: false,
 				description: "Enable server-side rendering (Solid 2.0 templates that support it)",
 			},
+			"devtools": {
+				type: "boolean",
+				required: false,
+				description: `Add ${START_DEVTOOLS_PACKAGE} (Solid 2.0 projects only)`,
+			},
 			"ts": {
 				type: "boolean",
 				required: false,
@@ -106,6 +120,7 @@ export const createSolid = (version: string) =>
 				library,
 				vanilla,
 				ssr,
+				devtools,
 				ts,
 				js,
 				v2,
@@ -220,6 +235,18 @@ export const createSolid = (version: string) =>
 				p.log.warn(`--ssr is not supported for this template and will be ignored`);
 			}
 
+			// Dev toolbar: only offered on Solid 2.0 projects (it peer-deps on solid-js 2.0)
+			let addDevtools = false;
+			if (projectType === "solid") {
+				addDevtools =
+					devtools ??
+					(await cancelable(
+						p.confirm({ message: `Add ${START_DEVTOOLS_PACKAGE} (development toolbar)?`, initialValue: false }),
+					));
+			} else if (devtools) {
+				p.log.warn(`--devtools is only supported for Solid 2.0 projects and will be ignored`);
+			}
+
 			// Need to transpile if the user wants Jabascript, but their selected template isn't Javascript
 			const transpileToJS = useJS && !template.startsWith("js");
 			if (projectType === "solid" && chosenTemplate) {
@@ -250,6 +277,11 @@ export const createSolid = (version: string) =>
 				p.log.error(`Template ${template} is not valid for project type ${projectType}`);
 				process.exit(0);
 			}
+			// The Solid vite plugin mounts the toolbar automatically in development,
+			// so adding the dependency is the whole setup
+			if (addDevtools) {
+				await addDevDependency(projectName, START_DEVTOOLS_PACKAGE, START_DEVTOOLS_VERSION);
+			}
 			// Add .gitignore
 			writeFileSync(join(projectName, ".gitignore"), GIT_IGNORE);
 			// Add "Created with Solid CLI" text to bottom of README
 
@@ -130,6 +130,15 @@ export const SOLID_V2_TEMPLATES = [
 ] as const satisfies string[];
 export type SolidV2Template = (typeof SOLID_V2_TEMPLATES)[number];
 
+/**
+ * Dev toolbar offered by the wizard on Solid 2.0 scaffolds. It peer-deps on
+ * solid-js ^2.0.0-rc.0 (so 1.x project types don't qualify) and is mounted
+ * automatically by @solidjs/vite-plugin in development, so adding the
+ * dependency is the whole setup.
+ */
+export const START_DEVTOOLS_PACKAGE = "@solidjs/start-devtools";
+export const START_DEVTOOLS_VERSION = "^1.0.0-next.4";
+
 /**Supported Library Templates */
 export const LIBRARY_TEMPLATES = ["solid-lib-starter"] as const satisfies string[];
 export type LibraryTemplate = (typeof LIBRARY_TEMPLATES)[number];
 
@@ -0,0 +1,21 @@
+import { existsSync } from "node:fs";
+import { readFile, writeFile } from "node:fs/promises";
+import { join } from "node:path";
+
+/**
+ * Add a package to the scaffolded project's `devDependencies`, keeping the
+ * block alphabetized like the templates ship it. Indentation and the
+ * trailing newline are detected from the file so the rewrite doesn't churn
+ * the template's formatting. No-op when the project has no package.json.
+ */
+export const addDevDependency = async (projectDir: string, name: string, version: string) => {
+	const pkgPath = join(projectDir, "package.json");
+	if (!existsSync(pkgPath)) return;
+	const raw = (await readFile(pkgPath)).toString();
+	const pkg = JSON.parse(raw);
+	pkg.devDependencies = Object.fromEntries(
+		Object.entries({ ...pkg.devDependencies, [name]: version }).sort(([a], [b]) => a.localeCompare(b)),
+	);
+	const indent = raw.match(/^([ \t]+)"/m)?.[1] ?? "  ";
+	await writeFile(pkgPath, JSON.stringify(pkg, null, indent) + (raw.endsWith("\n") ? "\n" : ""));
+};
@@ -0,0 +1,88 @@
+import { runCommand } from "citty";
+import { afterEach, beforeEach, expect, it, vi } from "vitest";
+import { mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { addDevDependency } from "../src/utils/dev-deps";
+import { START_DEVTOOLS_PACKAGE, START_DEVTOOLS_VERSION } from "../src/utils/constants";
+
+const { confirm, createSolidV2 } = vi.hoisted(() => ({
+	confirm: vi.fn(),
+	createSolidV2: vi.fn(),
+}));
+
+vi.mock("@clack/prompts", async (importOriginal) => ({
+	...(await importOriginal<typeof import("@clack/prompts")>()),
+	confirm,
+}));
+
+vi.mock("../src/create-solid-v2", async (importOriginal) => ({
+	...(await importOriginal<typeof import("../src/create-solid-v2")>()),
+	createSolidV2,
+}));
+
+import { createSolid } from "../src";
+
+const TEMPLATE_PKG = {
+	name: "example-basic",
+	devDependencies: { "typescript": "^5.9.2", "vite": "^8.1.5" },
+	dependencies: { "solid-js": "^2.0.0-rc.0" },
+};
+
+let projectDir: string;
+beforeEach(() => {
+	// Unroutable address: fetchTemplatesManifest fails fast and falls back to the
+	// baked-in template lists, same trick used in manifest.test.ts / cli.test.ts.
+	process.env.SOLID_CLI_TEMPLATES_MANIFEST_URL = "http://127.0.0.1:1/templates.json";
+	projectDir = join(mkdtempSync(join(tmpdir(), "solid-cli-devtools-")), "app");
+	// Stand in for the template download: just materialize a package.json
+	createSolidV2.mockImplementation(async ({ destination }: { destination: string }) => {
+		mkdirSync(destination, { recursive: true });
+		writeFileSync(join(destination, "package.json"), JSON.stringify(TEMPLATE_PKG, null, 2) + "\n");
+	});
+});
+afterEach(() => {
+	delete process.env.SOLID_CLI_TEMPLATES_MANIFEST_URL;
+	rmSync(join(projectDir, ".."), { recursive: true, force: true });
+	vi.clearAllMocks();
+});
+
+const readPkg = () => JSON.parse(readFileSync(join(projectDir, "package.json")).toString());
+
+it("prompts for start-devtools on Solid 2.0 projects and adds it on yes", async () => {
+	confirm.mockResolvedValueOnce(true);
+
+	// --ssr answers the SSR toggle up front, so the only confirm left is devtools
+	await runCommand(createSolid("test"), { rawArgs: [projectDir, "basic", "--solid", "--ts", "--ssr"] });
+
+	expect(confirm).toHaveBeenCalledTimes(1);
+	expect(confirm.mock.calls[0][0].message).toContain(START_DEVTOOLS_PACKAGE);
+	expect(readPkg().devDependencies[START_DEVTOOLS_PACKAGE]).toBe(START_DEVTOOLS_VERSION);
+});
+
+it("leaves the project untouched when the devtools prompt is declined", async () => {
+	confirm.mockResolvedValueOnce(false);
+
+	await runCommand(createSolid("test"), { rawArgs: [projectDir, "basic", "--solid", "--ts", "--ssr"] });
+
+	expect(readPkg().devDependencies[START_DEVTOOLS_PACKAGE]).toBeUndefined();
+});
+
+it("skips the prompt when --devtools is passed", async () => {
+	await runCommand(createSolid("test"), { rawArgs: [projectDir, "basic", "--solid", "--ts", "--ssr", "--devtools"] });
+
+	expect(confirm).not.toHaveBeenCalled();
+	expect(readPkg().devDependencies[START_DEVTOOLS_PACKAGE]).toBe(START_DEVTOOLS_VERSION);
+});
+
+it("keeps devDependencies alphabetized and preserves the template's formatting", async () => {
+	mkdirSync(projectDir, { recursive: true });
+	writeFileSync(join(projectDir, "package.json"), JSON.stringify(TEMPLATE_PKG, null, 2) + "\n");
+
+	await addDevDependency(projectDir, START_DEVTOOLS_PACKAGE, START_DEVTOOLS_VERSION);
+
+	const raw = readFileSync(join(projectDir, "package.json")).toString();
+	expect(raw.endsWith("\n")).toBe(true);
+	expect(raw).toContain('  "devDependencies"');
+	expect(Object.keys(readPkg().devDependencies)).toEqual([START_DEVTOOLS_PACKAGE, "typescript", "vite"]);
+});