#!/usr/bin/env node
// pi-chrome-mcp: the Chrome you are already signed into, as an MCP server.
//
// It loads pi-chrome's browser tools - the same code the pi agent runs - against a small stand-in
// for pi's extension API, and serves them over MCP. So Claude Code, Claude Desktop, or any other
// MCP client drives the browser through pi-chrome's companion extension, with one implementation
// of the tools, the page snapshots and the bridge client rather than a second copy to drift.
//
// pi-chrome itself is this repository's own extensions/chrome-profile-bridge, the directory above
// this one; PI_CHROME_PATH points at another copy instead.
//
// Two transports:
//
//   stdio (default)        one client, the process's own. What MCP clients start for themselves.
//   --http HOST:PORT       every client, over streamable HTTP at http://HOST:PORT/mcp. One process
//                          for a machine, rather than one per client session; needs a bearer token.
//
// pi-chrome refuses to load twice in one process, and does not need to: it asks for the session id
// on every bridge command, and the answer here depends on who is calling. Each MCP connection, and
// each session name within it, is its own pi-chrome session - own automation tab, own tab group.
//
// With stdio, stdout belongs to the MCP protocol; everything else goes to stderr.

console.log = console.error;
console.info = console.error;

import { AsyncLocalStorage } from "node:async_hooks";
import { execSync } from "node:child_process";
import { createHash, randomUUID, timingSafeEqual } from "node:crypto";
import { mkdirSync, mkdtempSync, readFileSync, renameSync, writeFileSync } from "node:fs";
import { createServer } from "node:http";
import { homedir, tmpdir } from "node:os";
import { dirname, join, resolve } from "node:path";
import { fileURLToPath } from "node:url";
import { createJiti } from "jiti";
import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { CallToolRequestSchema, isInitializeRequest, ListToolsRequestSchema } from "@modelcontextprotocol/sdk/types.js";

const here = dirname(fileURLToPath(import.meta.url));
const VERSION = JSON.parse(readFileSync(resolve(here, "package.json"), "utf8")).version;
// What clients see this server called, and what its logs, temp files and state file are named.
const NAME = process.env.MCP_SERVER_NAME?.trim() || "chrome";
const log = (message) => console.error(`[${NAME}] ${message}`);
// Base64 grows a file by a third; this keeps the encoded image under Claude Desktop's 1MB limit.
const MAX_INLINE_IMAGE_BYTES = 700 * 1024;

// pi-chrome's tool layer: the one in this repository by default, or any other copy of it.
const EXTENSION = process.env.PI_CHROME_PATH?.trim() || resolve(here, "../extensions/chrome-profile-bridge/index.ts");

// --http HOST:PORT, or unset for stdio.
const HTTP = (() => {
	const at = process.argv.indexOf("--http");
	if (at === -1) return undefined;
	const match = /^([^:\s]+):(\d{1,5})$/.exec(process.argv[at + 1] ?? "");
	if (!match) {
		log("--http needs HOST:PORT");
		process.exit(2);
	}
	return { host: match[1], port: Number(match[2]) };
})();

// Where pi-chrome's bridge listens, which this server also calls directly to close tabs. The
// extension polls that bridge; with a plain pi-chrome it is this process's own, on loopback.
// A fork that drives a browser on another host points PI_CHROME_REMOTE at its broker instead.
const LOCAL_BRIDGE = new Set(["local", "localhost", "off", "none", "0", "no"]);
const remote = process.env.PI_CHROME_REMOTE?.trim();
const BRIDGE = remote && !LOCAL_BRIDGE.has(remote.toLowerCase())
	? remote
	: `127.0.0.1:${process.env.PI_CHROME_BRIDGE_PORT ?? 17318}`;

// An HTTP client's named sessions have their tabs closed after this long without a call. Clients
// rarely say goodbye - Claude Code just drops the connection - so this is what stops an exited
// session's tabs from staying open for good. A session that comes back gets a fresh tab.
const IDLE_CLEANUP_MS = Number(process.env.MCP_IDLE_CLEANUP_MS ?? 60 * 60_000);
// ...and its connection state is dropped after this long. Harmless either way: a client that
// comes back later with the old session id is taken back in (see adopt below).
const IDLE_FORGET_MS = 24 * 60 * 60_000;
// Which pi-chrome sessions are open, so a restart neither loses them nor leaks them. Per port,
// so a test server on another port keeps its own.
const STATE_PATH = process.env.MCP_STATE_FILE
	?? (HTTP ? join(homedir(), ".local", "state", `${NAME}-mcp`, `sessions-${HTTP.port}.json`) : undefined);

// The MCP client's own permission prompts gate each tool call, so pi-chrome's /chrome authorize
// has no equivalent here - and no way to be run: it is a pi command.
//
// pi-chrome keeps that grant on globalThis, so that a pi /reload - which re-evaluates the module -
// does not silently drop one, and reads it back as it loads. Setting it before the load is
// therefore how this server starts authorized. PI_CHROME_AUTHORIZE does the same in forks that
// read it; both are set, and either alone is enough.
globalThis.__piChromeProfileBridgeAuth__ ??= { until: "indefinite" };
process.env.PI_CHROME_AUTHORIZE ??= "indefinite";

// --- instructions -------------------------------------------------------------------------------
//
// Claude Code keeps only the first 2KB of a server's instructions, so what matters leads: anything
// the operator supplied, then how sessions work, then pi-chrome's own primer.

const EXTRA = (() => {
	const path = process.env.MCP_INSTRUCTIONS_FILE?.trim();
	if (!path) return "";
	try {
		return `${readFileSync(path, "utf8").trim()}\n`;
	} catch (error) {
		log(`could not read MCP_INSTRUCTIONS_FILE ${path}: ${error.message}`);
		return "";
	}
})();

const ESSENTIALS = `${EXTRA}This server drives the user's own browser, signed in as they are, through the pi-chrome companion extension. Every action acts as the user: ask before posting, sending, buying, deleting, or changing account settings.
- Every call needs a session: a short name you choose, e.g. main or research-a. Calls with the same session share its tabs, and a call without targetId acts on that session's automation tab; a new name starts fresh with its own. Parallel subagents must each use a different session - give each one its name.
- chrome_snapshot before interacting; prefer uid over selector; includeSnapshot=true on click/type/fill/key verifies in one call.
- Screenshots come back inline. Uploads take absolute paths that the browser's machine can read.`;

// --- sessions the agent names -----------------------------------------------------------------
//
// pi gets one pi-chrome session per process, and runs one agent per process. An MCP client does
// not: Claude Code gives every subagent the parent's connection to this server, and nothing in an
// MCP call says which agent made it. So the caller names its session on every call. Each name is
// its own pi-chrome session - its own automation tab, tab group and cleanup - and the same name is
// the caller's way of deliberately continuing one. Names are scoped to the connection, so two
// clients that both pick "main" still never share.
//
// The name is applied where pi-chrome asks for the current session id rather than threaded through
// each tool's params, so every bridge command a call sends is keyed to it, whatever the tool does
// with its arguments.

const SESSION_PATTERN = /^[A-Za-z0-9][A-Za-z0-9._-]{0,47}$/;
const SESSION_PARAM = {
	type: "string",
	pattern: SESSION_PATTERN.source,
	description:
		'Required. A short name you choose for this line of work, e.g. "main" or "research-a" (letters, digits, . _ -). Calls with the same session share its tabs; a new name starts fresh with its own tab. Parallel subagents must each use a different session.',
};
const SESSION_ERROR =
	'Missing or invalid "session". Every call to this server needs one: a short name you choose for this line of work, e.g. "main" (letters, digits, . _ -, up to 48 characters). Calls with the same session share its tabs; a new name starts fresh with its own tab. Parallel subagents must each use a different session.';

// What a call runs under: { conn, name }. conn is one MCP connection (stdio has exactly one);
// name is the session the call named.
const callSession = new AsyncLocalStorage();

// --- a stand-in for the parts of pi's extension API that pi-chrome uses ----------------------

const sessionId = randomUUID();

// One MCP connection. key prefixes every pi-chrome session id made for it, so two connections that
// both name "main" never meet; label is what its tab groups show.
function newConn(key, label) {
	return { key, label, clientName: "mcp", used: new Set(), lastUsed: Date.now() };
}
// Screenshots land here rather than in whatever project the client was started in.
const cwd = mkdtempSync(join(tmpdir(), `${NAME}-mcp-`));
const tools = new Map();
let active = new Set();
const handlers = new Map();

const ui = {
	notify: (message, level = "info") => log(`${level}: ${message}`),
	setStatus: () => {},
	confirm: async () => false,
	select: async () => undefined,
	input: async () => undefined,
	theme: { fg: (_color, text) => text },
};

const ctx = {
	cwd,
	ui,
	hasUI: false,
	sessionManager: {
		// Read by pi-chrome on every bridge command: inside a tool call, the caller's named session.
		getSessionId: () => {
			const call = callSession.getStore();
			return call ? `${call.conn.key}:${call.name}` : sessionId;
		},
		// Names the session's tab group in the browser, e.g. "Pi Session: claude-code 1a2b research-a".
		getSessionName: () => {
			const call = callSession.getStore();
			return call ? `${call.conn.clientName} ${call.conn.label} ${call.name}` : `mcp ${sessionId.slice(0, 4)}`;
		},
	},
};

const pi = {
	// pi makes a tool active as it is registered; pi-chrome's own active-tool list omits some
	// (chrome_find, chrome_inspect) and relies on that.
	registerTool(tool) {
		tools.set(tool.name, tool);
		active.add(tool.name);
	},
	// /chrome's authorize, background and doctor controls have no MCP equivalent.
	registerCommand() {},
	registerFlag() {},
	getFlag: () => undefined,
	on(event, handler) {
		if (!handlers.has(event)) handlers.set(event, []);
		handlers.get(event).push(handler);
	},
	getActiveTools: () => [...active],
	setActiveTools(names) {
		active = new Set(names);
	},
	sendMessage() {},
	// pi-chrome logs authorization changes to the session history; there is none here.
	appendEntry() {},
	exec: async () => ({ code: 1, stdout: "", stderr: "not available in the MCP server" }),
};

async function emit(event, payload) {
	let last;
	for (const handler of handlers.get(event) ?? []) last = await handler(payload, ctx);
	return last;
}

// --- load pi-chrome ---------------------------------------------------------------------------

// pi-chrome imports typebox at runtime, and its own directory may have no node_modules: point it
// at the copy pinned here, the version pi ships, and pi-tui at a stand-in. jiti rather than Node's
// type stripping, because pi-chrome uses constructor parameter properties, which strip-only mode
// rejects.
const jiti = createJiti(import.meta.url, {
	alias: {
		typebox: fileURLToPath(import.meta.resolve("typebox")),
		"@earendil-works/pi-tui": fileURLToPath(new URL("pi-tui.mjs", import.meta.url)),
	},
});
const extension = await jiti.import(EXTENSION, { default: true });
extension(pi);
await emit("session_start", { reason: "startup" });

if (active.size === 0) {
	// pi-chrome registers its tools only once authorized, so this means the grant above did not
	// take: most likely its authorization moved in a version this server has not been tried with.
	log(`pi-chrome at ${EXTENSION} registered no tools. Its authorization hook may have changed; this server is pinned to the pi-chrome in package.json.`);
	process.exit(1);
}

// pi-chrome's primer: its usage rules, and anything its own configuration adds. Lines about
// /chrome commands are dropped, since none exist here.
//
// A fork's primer may name another browser's tools, which differ by client: browser_* in pi,
// mcp__<server>__* elsewhere. pi-chrome reads PI_CHROME_OTHER_BROWSER_TOOLS as it builds the
// primer, synchronously inside the handler, so the variable only has to hold for that call.
const UPSTREAM_SECTION = "chrome-profile-bridge";
async function instructionsWith(otherTools) {
	const saved = process.env.PI_CHROME_OTHER_BROWSER_TOOLS;
	if (otherTools) process.env.PI_CHROME_OTHER_BROWSER_TOOLS = otherTools;
	// pi-chrome adds its primer as named prompt sections, one per handler (upstream's and a fork's),
	// or, written for an older pi, returns a whole systemPrompt instead. Take both; upstream's goes
	// first.
	const sections = {};
	const pending = emit("before_agent_start", { systemPrompt: "", systemPromptOptions: { sections } });
	process.env.PI_CHROME_OTHER_BROWSER_TOOLS = saved;
	const returned = (await pending)?.systemPrompt ?? "";
	const names = Object.keys(sections).sort((a, b) => (b === UPSTREAM_SECTION) - (a === UPSTREAM_SECTION));
	const primer = [...names.map((name) => `<${name}>\n${sections[name]}\n</${name}>`), returned].join("\n");
	return [ESSENTIALS, primer.split("\n").filter((line) => !/\/chrome\b/.test(line)).join("\n")].join("\n");
}
const OTHER_BROWSER_TOOLS = process.env.PI_CHROME_OTHER_BROWSER_TOOLS?.trim();
const instructions = await instructionsWith(OTHER_BROWSER_TOOLS);
// pi's built-in MCP support introduces itself as pi, and pi-mcp-adapter as pi-mcp-<server name>;
// in pi, the other browser's tools are pi's own, not another MCP server's.
const piInstructions = OTHER_BROWSER_TOOLS ? await instructionsWith("browser_*") : instructions;

// --- MCP --------------------------------------------------------------------------------------

function inputSchema(toolName, parameters) {
	// TypeBox schemas are JSON Schema plus symbol-keyed metadata, which a JSON round trip drops.
	const schema = JSON.parse(JSON.stringify(parameters ?? {}));
	if (schema.properties?.session) throw new Error(`${toolName} already has a "session" parameter; the MCP session name needs another`);
	return {
		...schema,
		type: "object",
		properties: { session: SESSION_PARAM, ...(schema.properties ?? {}) },
		required: ["session", ...(schema.required ?? [])],
	};
}

function toMcpContent(toolName, result) {
	const content = [];
	for (const item of result?.content ?? []) {
		if (item.type === "text") content.push({ type: "text", text: item.text });
		else if (item.type === "image") content.push({ type: "image", data: item.data, mimeType: item.mimeType });
	}
	// pi-chrome saves screenshots to a file and returns only the path. Hand the image itself back
	// too, so the model can see it without another tool call; full-page tiles stay as the manifest.
	// Claude Desktop refuses a returned file over 1MB, so a bigger image stays a path.
	const details = result?.details ?? {};
	if (toolName === "chrome_screenshot" && typeof details.path === "string") {
		try {
			const bytes = readFileSync(details.path);
			const mimeType = details.format === "jpeg" ? "image/jpeg" : "image/png";
			if (bytes.length > MAX_INLINE_IMAGE_BYTES) {
				content.push({ type: "text", text: `(screenshot is ${Math.round(bytes.length / 1024)}KB, too big to attach; retake it with format "jpeg" to see it inline)` });
			} else {
				content.push({ type: "image", data: bytes.toString("base64"), mimeType });
			}
		} catch (error) {
			content.push({ type: "text", text: `(could not attach the screenshot: ${error.message})` });
		}
	}
	return content;
}

function slug(name) {
	return (name ?? "mcp").toLowerCase().replace(/[^a-z0-9.-]+/g, "-");
}

// Set by the HTTP server, which demands the same token from its clients; a bridge on another host
// wants it too. With a bridge of our own on loopback there is none, and none is needed.
let TOKEN;

// Close named sessions: their tabs and tab groups. Sent to the bridge directly rather than through
// pi-chrome's session_shutdown, which also stops its bridge client - for every session at once, so
// the first one to run would strand the rest.
async function closeSessions(key, names, label, why) {
	if (!names.length) return;
	log(`closing ${label}: sessions ${names.join(", ")} (${why})`);
	await Promise.allSettled(
		names.map((name) =>
			fetch(`http://${BRIDGE}/command`, {
				method: "POST",
				headers: { "content-type": "application/json", ...(TOKEN ? { authorization: `Bearer ${TOKEN}` } : {}) },
				body: JSON.stringify({ action: "automation.cleanup", params: { sessionKey: `session:${key}:${name}` }, timeoutMs: 2_000 }),
				signal: AbortSignal.timeout(4_000),
			}),
		),
	);
}

// One MCP server object per connection, all serving the same loaded tools.
function makeServer(conn, serverInstructions) {
	const server = new Server({ name: NAME, version: VERSION }, { capabilities: { tools: {} }, instructions: serverInstructions });

	server.oninitialized = () => {
		conn.clientName = slug(server.getClientVersion()?.name);
	};

	server.setRequestHandler(ListToolsRequestSchema, async () => ({
		tools: [...tools.values()]
			.filter((tool) => active.has(tool.name))
			.map((tool) => ({
				name: tool.name,
				title: tool.label,
				description: tool.description,
				inputSchema: inputSchema(tool.name, tool.parameters),
			})),
	}));

	server.setRequestHandler(CallToolRequestSchema, async (request, extra) => {
		const tool = tools.get(request.params.name);
		if (!tool || !active.has(tool.name)) {
			return { content: [{ type: "text", text: `Unknown tool: ${request.params.name}` }], isError: true };
		}
		// Refused rather than defaulted: a default would be one shared session again.
		const { session, ...args } = request.params.arguments ?? {};
		if (typeof session !== "string" || !SESSION_PATTERN.test(session)) {
			return { content: [{ type: "text", text: SESSION_ERROR }], isError: true };
		}
		if (!conn.used.has(session)) {
			conn.used.add(session);
			// Only the HTTP server sets this: it records the session so a restart can hand it back.
			conn.onUse?.();
		}
		conn.lastUsed = Date.now();
		try {
			const result = await callSession.run({ conn, name: session }, () => tool.execute(randomUUID(), args, extra.signal, () => {}, ctx));
			return { content: toMcpContent(tool.name, result) };
		} catch (error) {
			return { content: [{ type: "text", text: error?.message ?? String(error) }], isError: true };
		} finally {
			conn.lastUsed = Date.now();
		}
	});

	return server;
}

// --- stdio ------------------------------------------------------------------------------------

async function serveStdio() {
	const conn = newConn(sessionId, sessionId.slice(0, 4));
	const server = makeServer(conn, instructions);

	// Close every session's tabs through the bridge, then go. pi-chrome's own session_shutdown is
	// not used: it stops the bridge as it runs, so only the first session would be cleaned, and
	// with the bridge in this process, exiting closes it anyway.
	let closing = false;
	async function shutdown(why) {
		if (closing) return;
		closing = true;
		const names = [...conn.used];
		if (!names.length) process.exit(0);
		await Promise.race([
			closeSessions(conn.key, names, `${conn.label} (${conn.clientName})`, why),
			new Promise((r) => setTimeout(r, 3_000)),
		]);
		process.exit(0);
	}

	const transport = new StdioServerTransport();
	transport.onclose = () => void shutdown("transport closed");
	process.stdin.on("end", () => void shutdown("stdin closed"));
	process.on("SIGTERM", () => void shutdown("SIGTERM"));
	process.on("SIGINT", () => void shutdown("SIGINT"));
	await server.connect(transport);
	log(`v${VERSION} ready: ${active.size} tools, session ${sessionId.slice(0, 8)}`);
}

// --- streamable HTTP --------------------------------------------------------------------------

// Over HTTP anything that can reach the port could drive the browser, so a token is required.
// MCP_TOKEN, or MCP_TOKEN_COMMAND for a secret store; --no-auth is the deliberate way out.
function loadToken() {
	const fromEnv = process.env.MCP_TOKEN?.trim();
	if (fromEnv) return fromEnv;
	const command = process.env.MCP_TOKEN_COMMAND?.trim();
	if (command) {
		const token = execSync(command, { encoding: "utf8", stdio: ["ignore", "pipe", "pipe"] }).trim();
		if (!token) throw new Error(`MCP_TOKEN_COMMAND produced nothing: ${command}`);
		return token;
	}
	if (process.argv.includes("--no-auth")) return undefined;
	log("--http needs a token: set MCP_TOKEN, or MCP_TOKEN_COMMAND to read one from a secret store (or pass --no-auth deliberately)");
	process.exit(2);
}

async function serveHttp() {
	const token = loadToken();
	TOKEN = token;
	// A bridge that wants the same token (a broker on another host) would otherwise go looking for
	// it itself; hand it the one we have.
	if (token) process.env.PI_CHROME_TOKEN ??= token;
	const tokenDigest = token ? createHash("sha256").update(token).digest() : undefined;
	// Compare digests: timingSafeEqual needs equal lengths, and a guess's length must not leak.
	const hasValidToken = (request) => {
		if (!tokenDigest) return true;
		const match = /^Bearer\s+(.+)$/i.exec(String(request.headers.authorization ?? ""));
		return !!match && timingSafeEqual(createHash("sha256").update(match[1].trim()).digest(), tokenDigest);
	};

	// Taking back a session id this process never issued relies on two private fields of the
	// SDK's transport. The SDK is pinned; this makes a bump that renames them fail at startup
	// rather than as 400s later.
	{
		const probe = new StreamableHTTPServerTransport({ sessionIdGenerator: () => "probe" });
		if (!probe._webStandardTransport || !("_initialized" in probe._webStandardTransport)) {
			throw new Error("the MCP SDK's streamable HTTP transport changed shape; adopt() needs updating");
		}
	}

	const conns = new Map(); // MCP session id -> conn
	// Sessions this process is not serving right now: read back from the state file at startup,
	// after a restart. Each is either claimed by the client coming back (adopt) or swept like any
	// other idle session, so a restart leaves no tabs behind either way.
	const pending = new Map(); // MCP session id -> { key, names, lastUsed }

	function save() {
		if (!STATE_PATH) return;
		const open = {};
		for (const [id, conn] of conns) if (conn.used.size) open[id] = { key: conn.key, names: [...conn.used], lastUsed: conn.lastUsed };
		for (const [id, held] of pending) open[id] = { key: held.key, names: [...held.names], lastUsed: held.lastUsed };
		try {
			mkdirSync(dirname(STATE_PATH), { recursive: true });
			writeFileSync(`${STATE_PATH}.tmp`, JSON.stringify(open));
			renameSync(`${STATE_PATH}.tmp`, STATE_PATH);
		} catch (error) {
			log(`could not save ${STATE_PATH}: ${error.message}`);
		}
	}

	if (STATE_PATH) {
		try {
			for (const [id, held] of Object.entries(JSON.parse(readFileSync(STATE_PATH, "utf8")))) {
				pending.set(id, { key: held.key, names: new Set(held.names), lastUsed: held.lastUsed ?? Date.now() });
			}
			if (pending.size) log(`${pending.size} session(s) from a previous run; each is taken back or swept when idle`);
		} catch (error) {
			if (error.code !== "ENOENT") log(`could not read ${STATE_PATH}: ${error.message}`);
		}
	}

	async function cleanup(conn, why) {
		const names = [...conn.used];
		conn.used.clear();
		save();
		await closeSessions(conn.key, names, `${conn.label} (${conn.clientName})`, why);
	}

	async function forget(conn, why) {
		conns.delete(conn.id);
		await cleanup(conn, why);
		await conn.transport.close().catch(() => {});
	}

	async function dropPending(id, held, why) {
		pending.delete(id);
		save();
		await closeSessions(held.key, [...held.names], `${id.slice(0, 4)} (previous run)`, why);
	}

	// A connection for a new client (id undefined, taken from the initialize request it is about to
	// handle) or, with id, one that already holds a session id this process does not know.
	//
	// The second case is adopt: a client whose session this process forgot, or which predates a
	// restart. The protocol answer is 404 and the client re-initializes, but Claude Code does not:
	// it reports the error and the tools stay dead until someone runs /mcp. So the id is taken back
	// in, as if it had just been initialized. Nothing is lost that mattered - the tools, their
	// schemas and the instructions are the same for everyone.
	async function open(id, clientName) {
		const conn = newConn(undefined, undefined);
		conn.clientName = clientName;
		conn.onUse = save;
		const adopt = (sid) => {
			conn.id = sid;
			// The MCP session id alone, not this process's: a client taken back after a restart must
			// key the same pi-chrome sessions, or its tabs are stranded and it gets a blank one.
			conn.key = `mcp-${sid}`;
			conn.label = sid.slice(0, 4);
			conns.set(sid, conn);
			const held = pending.get(sid);
			if (held) {
				pending.delete(sid);
				for (const name of held.names) conn.used.add(name);
			}
			save();
		};
		conn.transport = new StreamableHTTPServerTransport({
			sessionIdGenerator: () => randomUUID(),
			onsessioninitialized: adopt,
			// The transport closes itself once this returns.
			onsessionclosed: () => {
				conns.delete(conn.id);
				void cleanup(conn, "client ended the session");
			},
			enableDnsRebindingProtection: true,
			allowedHosts: [`${HTTP.host}:${HTTP.port}`],
		});
		conn.server = makeServer(conn, (clientName === "pi" || clientName.startsWith("pi-mcp")) ? piInstructions : instructions);
		await conn.server.connect(conn.transport);
		if (id) {
			conn.transport._webStandardTransport._initialized = true;
			conn.transport._webStandardTransport.sessionId = id;
			adopt(id);
			log(`took back session ${id.slice(0, 8)}`);
		}
		return conn;
	}

	async function readJson(request) {
		const chunks = [];
		let size = 0;
		for await (const chunk of request) {
			size += chunk.length;
			if (size > 4 * 1024 * 1024) throw new Error("request body too large");
			chunks.push(chunk);
		}
		return chunks.length ? JSON.parse(Buffer.concat(chunks).toString("utf8")) : undefined;
	}

	const reply = (response, status, message) => {
		response.writeHead(status, { "content-type": "application/json" });
		response.end(JSON.stringify({ jsonrpc: "2.0", error: { code: -32000, message }, id: null }));
	};

	const http = createServer(async (request, response) => {
		try {
			if (new URL(request.url ?? "/", "http://x").pathname !== "/mcp") return reply(response, 404, "Not found: the endpoint is /mcp");
			if (!hasValidToken(request)) return reply(response, 401, "Unauthorized: this server needs its bearer token");
			const body = request.method === "POST" ? await readJson(request) : undefined;
			const id = request.headers["mcp-session-id"];
			let conn = typeof id === "string" ? conns.get(id) : undefined;
			if (!conn) {
				const initialize = [body].flat().find((message) => message && isInitializeRequest(message));
				if (initialize) conn = await open(undefined, slug(initialize.params?.clientInfo?.name));
				else if (typeof id === "string" && id && request.method !== "DELETE") conn = await open(id, "mcp");
				else if (request.method === "DELETE") {
					// A client saying goodbye to a session restored from the state file: close its
					// tabs now rather than leaving them to the idle sweep.
					const held = typeof id === "string" ? pending.get(id) : undefined;
					if (!held) return reply(response, 404, "Session not found");
					await dropPending(id, held, "client ended the session");
					response.writeHead(200).end();
					return;
				}
				else return reply(response, 400, "Bad Request: Mcp-Session-Id header is required");
			}
			conn.lastUsed = Date.now();
			await conn.transport.handleRequest(request, response, body);
		} catch (error) {
			log(`${request.method} failed: ${error?.message ?? error}`);
			if (!response.headersSent) reply(response, error instanceof SyntaxError ? 400 : 500, error?.message ?? "error");
		}
	});

	const sweep = setInterval(() => {
		const now = Date.now();
		for (const conn of conns.values()) {
			const idle = now - conn.lastUsed;
			if (idle > IDLE_FORGET_MS) void forget(conn, "idle");
			else if (idle > IDLE_CLEANUP_MS && conn.used.size) void cleanup(conn, "idle");
		}
		for (const [id, held] of pending) {
			if (now - held.lastUsed > IDLE_CLEANUP_MS) void dropPending(id, held, "idle, from a previous run");
		}
	}, 60_000);
	sweep.unref();

	let closing = false;
	// Tabs are deliberately left open. A client whose session this process was serving is still
	// alive and will be taken back when the server returns (a restart is seconds), so closing its
	// tabs would strand it: it would find a blank automation tab, and a navigation it had just been
	// told succeeded would be gone. What the next run does not reclaim, its sweep closes once idle,
	// from the state file saved here.
	async function shutdown(why) {
		if (closing) return;
		closing = true;
		log(`stopping (${why}): ${conns.size} connections, tabs left for the next run`);
		http.close();
		save();
		process.exit(0);
	}
	process.on("SIGTERM", () => void shutdown("SIGTERM"));
	process.on("SIGINT", () => void shutdown("SIGINT"));

	await new Promise((resolveListen, rejectListen) => {
		http.once("error", rejectListen);
		http.listen(HTTP.port, HTTP.host, resolveListen);
	});
	log(`v${VERSION} ready: ${active.size} tools at http://${HTTP.host}:${HTTP.port}/mcp, bridge ${BRIDGE}${token ? "" : ", NO AUTH"}`);
}

await (HTTP ? serveHttp() : serveStdio());