browser/src/cdp/CDP.zig

// Copyright (C) 2023-2024  Lightpanda (Selecy SAS)
//
// Francis Bouvier <francis@lightpanda.io>
// Pierre Tachoire <pierre@lightpanda.io>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

const std = @import("std");
const lp = @import("lightpanda");

const App = @import("../App.zig");
const Inbox = @import("../Inbox.zig");
const Network = @import("../network/Network.zig");
const Notification = @import("../Notification.zig");
const WS = @import("../network/WS.zig");
const js = @import("../browser/js/js.zig");
const Browser = @import("../browser/Browser.zig");
const Session = @import("../browser/Session.zig");
const Frame = @import("../browser/Frame.zig");
const Mime = @import("../browser/Mime.zig");
const Element = @import("../browser/webapi/Element.zig");
const Label = @import("../browser/webapi/element/html/Label.zig");
const Transfer = @import("../browser/HttpClient.zig").Transfer;

const Connection = @import("Connection.zig");
const Incrementing = @import("id.zig").Incrementing;
const InterceptState = @import("domains/fetch.zig").InterceptState;

const log = lp.log;
const json = std.json;
const posix = std.posix;
const Allocator = std.mem.Allocator;

pub const URL_BASE = "chrome://newtab/";

const IS_DEBUG = @import("builtin").mode == .Debug;

const SessionIdGen = Incrementing(u32, "SID");
const BrowserContextIdGen = Incrementing(u32, "BID");
// webmcp tool invocation
pub const InvocationIdGen = Incrementing(u32, "INV");

// Generic so that we can inject mocks into it.
const CDP = @This();

app: *App,
conn: Connection,
browser: Browser,
allocator: Allocator,

// Network-thread read-side handle for the CDP socket. Populated in
// init; Server.handleConnection calls network.registerCdp(&cdp.link)
// after the worker-side handshake completes, and unregisterCdp before
// teardown.
link: Network.CdpLink,

// when true, any target creation must be attached.
target_auto_attach: bool = false,

session_id_gen: SessionIdGen = .{},
browser_context_id_gen: BrowserContextIdGen = .{},

browser_context: ?BrowserContext,

// Re-used arena for processing a message. We're assuming that we're getting
// 1 message at a time.
message_arena: std.heap.ArenaAllocator,

// Used for processing notifications within a browser context.
notification_arena: std.heap.ArenaAllocator,

// Valid for 1 frame navigation (what CDP calls a "renderer")
frame_arena: std.heap.ArenaAllocator,

// Valid for the entire lifetime of the BrowserContext. Should minimize
// (or altogether eliminate) our use of this.
browser_context_arena: std.heap.ArenaAllocator,

pub fn init(
    self: *CDP,
    app: *App,
    socket: posix.socket_t,
    json_version_response: []const u8,
) !void {
    const allocator = app.allocator;

    self.* = .{
        .app = app,
        .link = undefined,
        .conn = undefined,
        .browser = undefined,
        .allocator = allocator,
        .browser_context = null,
        .frame_arena = std.heap.ArenaAllocator.init(allocator),
        .message_arena = std.heap.ArenaAllocator.init(allocator),
        .notification_arena = std.heap.ArenaAllocator.init(allocator),
        .browser_context_arena = std.heap.ArenaAllocator.init(allocator),
    };

    try self.browser.init(app, .{ .env = .{ .with_inspector = true } }, self);
    const http_client = &self.browser.http_client;

    try self.conn.init(allocator, socket, json_version_response, &http_client.inbox, &app.arena_pool);
    errdefer self.conn.deinit();

    self.link = .{
        .cdp = self,
        .state = .live,
        .socket = socket,
        .handle = http_client.handle,
    };
}

pub fn deinit(self: *CDP) void {
    if (self.browser_context) |*bc| {
        bc.deinit();
    }
    self.browser.deinit();
    self.frame_arena.deinit();
    self.message_arena.deinit();
    self.notification_arena.deinit();
    self.browser_context_arena.deinit();
    self.conn.deinit();
}
// Called by Network when readable bytes arrive on the CDP socket.
// Feeds them through the WS framer and pushes each parsed frame into
// the worker's inbox. Returns false if a close frame was seen (or a
// fatal frame error) so Network drops the link from its poll set.
//
// One network read can carry more bytes than the reader's current
// free space — large CDP messages (Page.addScriptToEvaluateOnNewDocument,
// Runtime evaluation results, etc.) routinely exceed 16 KB, and a
// single read can contain multiple messages, or part of messages. We loop: feed
// what fits, run processMessages (which extracts complete frames, compacts the
// reader, and grows the buffer if it sees a frame header larger than current
// capacity), repeat until the chunk is drained.
pub fn onData(self: *CDP, data: []const u8) anyerror!bool {
    var remaining = data;
    while (remaining.len > 0) {
        const n = self.conn.feedBytes(remaining);
        remaining = remaining[n..];
        if ((try self.conn.processMessages()) == false) {
            return false;
        }
    }
    return true;
}

// Called by Network when it drops the link unsolicited (peer EOF, read
// error, poll HUP/ERR). Push a disconnect into the inbox so the
// worker's drainInbox surfaces error.ClientDisconnected.
pub fn onLinkDisconnect(self: *CDP, err: ?anyerror) void {
    const arena = self.browser.arena_pool.acquire(.tiny, "cdp disconnect") catch |e| switch (e) {
        error.OutOfMemory => @panic("OOM"),
    };

    self.browser.http_client.inbox.push(arena, .{ .disconnect = err });
}

// Called in the Worker to dispatch a single CDP message bubbled up by
// HttpClient.drainInbox. The Network thread already parsed the JSON
// when it pushed the message to the inbox, so we skip straight to
// dispatchParsed without re-parsing. `c.raw` and `c.arena` outlive
// this call (they're owned by the inbox Message which drainInbox
// frees right after we return), so `c.input`'s string slices stay
// valid for the duration of dispatch.
pub fn onMessage(self: *CDP, c: *Inbox.Message.Cdp) anyerror!void {
    const arena = &self.message_arena;
    defer _ = arena.reset(.{ .retain_with_limit = 1024 * 16 });
    return self.dispatchParsed(arena.allocator(), .{ .cdp = self }, c.raw, c.input);
}

// Parse + dispatch a raw JSON CDP message. Used by tests (which
// don't go through the Network thread / inbox pipeline) and by any
// caller that has bytes rather than a pre-parsed InputMessage.
pub fn processMessage(self: *CDP, msg: []const u8) !void {
    const arena = &self.message_arena;
    defer _ = arena.reset(.{ .retain_with_limit = 1024 * 16 });
    return self.dispatch(arena.allocator(), .{ .cdp = self }, msg);
}

// Called in the worker when a PING message is received
pub fn onPing(self: *CDP, body: []const u8) void {
    self.conn.sendPong(body) catch |err| {
        log.warn(.app, "CDP pong", .{ .err = err });
    };
}

// Called in the Worker when a peer-initiated close with CLOSE_NORMAL. The worker
// loop tears down immediately after; drainInbox returns
// error.ClientDisconnected once we return.
pub fn onClose(self: *CDP) void {
    self.conn.send(&WS.CLOSE_NORMAL) catch |err| {
        log.warn(.app, "CDP close reply", .{ .err = err });
    };
}

// Called in the Worker when the peer disconnected (peer EOF, fatal frame error,
// or right after a peer close was replied to). drainInbox returns
// error.ClientDisconnected, which the worker loop catches to tear down.
//
// If `err` is a recognized WS framing error, send the matching close
// frame back to the peer before tearing down — that's how clients
// observe protocol violations (close code 1002 / 1009 / etc.).
pub fn onDisconnect(self: *CDP, err: ?anyerror) void {
    if (err) |e| {
        if (WS.errorReply(e)) |close_frame| {
            self.conn.send(close_frame) catch {};
        }
    }
    log.info(.cdp, "CDP disconnect", .{ .err = err });
}

pub fn sendJSON(self: *CDP, message: anytype) !void {
    try self.conn.sendJSON(message, .{ .emit_null_optional_fields = false });
}

pub fn tick(self: *CDP) !bool {
    // Liveness is enforced by TCP keepalive configured in
    // Server.configureSocket; the wakeup lets V8 run or terminate.
    const wait_ms: u32 = 1000; // 1s

    self.pageWait(wait_ms) catch |wait_err| switch (wait_err) {
        error.NoPage => {
            // No active page yet (or a teardown is in flight). Fall
            // back to ticking the http client directly so CDP messages
            // still get dispatched.
            self.browser.http_client.tick(wait_ms, .all) catch |err| switch (err) {
                error.ClientDisconnected => return false,
                else => {
                    log.err(.app, "http tick", .{ .err = err });
                    return false;
                },
            };
        },
        error.ClientDisconnected => return false,
        else => return wait_err,
    };
    return true;
}

fn pageWait(self: *CDP, ms: u32) !void {
    const session = &(self.browser.session orelse return error.NoPage);
    var runner = try session.runner(.{});
    return runner.waitCDP(.{ .ms = ms });
}

// Parse-then-dispatch entry point. Used by:
//   - CDP.processMessage (tests, and any other caller that hands us
//     raw JSON bytes).
//   - Target.sendMessageToTarget (a CDP command that wraps another
//     CDP message as a string parameter and forwards it through the
//     dispatch table).
// The normal Network-thread path doesn't go through here — it parses
// once on the Network thread and reaches dispatchParsed directly via
// onMessage.
pub fn dispatch(self: *CDP, arena: Allocator, sender: Command.Sender, str: []const u8) !void {
    const input = json.parseFromSliceLeaky(InputMessage, arena, str, .{
        .ignore_unknown_fields = true,
    }) catch return error.InvalidJSON;
    return self.dispatchParsed(arena, sender, str, input);
}

// Dispatch a pre-parsed CDP message. The caller is responsible for
// keeping `str` and the backing storage for `input`'s string slices
// alive for the duration of the call.
fn dispatchParsed(self: *CDP, arena: Allocator, sender: Command.Sender, str: []const u8, input: InputMessage) !void {
    var command = Command{
        .input = .{
            .json = str,
            .id = input.id,
            .action = "",
            .params = input.params,
            .session_id = input.sessionId,
        },
        .cdp = self,
        .arena = arena,
        .sender = sender,
        .browser_context = if (self.browser_context) |*bc| bc else null,
    };

    // See dispatchStartupCommand for more info on this.
    var is_startup = false;
    if (input.sessionId) |input_session_id| {
        if (std.mem.eql(u8, input_session_id, "STARTUP")) {
            is_startup = true;
        } else if (self.isValidSessionId(input_session_id) == false) {
            return command.sendError(-32001, "Unknown sessionId", .{});
        }
    }

    if (is_startup) {
        dispatchStartupCommand(&command, input.method) catch |err| {
            command.sendError(-31999, @errorName(err), .{}) catch return err;
        };
    } else {
        dispatchCommand(&command, input.method) catch |err| {
            command.sendError(-31998, @errorName(err), .{}) catch return err;
        };
    }
}

// A CDP session isn't 100% fully driven by the driver. There's are
// independent actions that the browser is expected to take. For example
// Puppeteer expects the browser to startup a tab and thus have existing
// targets.
// To this end, we create a [very] dummy BrowserContext, Target and
// Session. There isn't actually a BrowserContext, just a special id.
// When messages are received with the "STARTUP" sessionId, we do
// "special" handling - the bare minimum we need to do until the driver
// switches to a real BrowserContext.
// (I can imagine this logic will become driver-specific)
fn dispatchStartupCommand(command: *Command, method: []const u8) !void {
    // Stagehand parses the response and error if we don't return a
    // correct one for Page.getFrameTree on startup call.
    if (std.mem.eql(u8, method, "Page.getFrameTree")) {
        // The Page.getFrameTree handles startup response gracefully.
        return dispatchCommand(command, method);
    }

    return command.sendResult(null, .{});
}

fn dispatchCommand(command: *Command, method: []const u8) !void {
    const domain = blk: {
        const i = std.mem.indexOfScalarPos(u8, method, 0, '.') orelse {
            return error.InvalidMethod;
        };
        command.input.action = method[i + 1 ..];
        break :blk method[0..i];
    };

    switch (domain.len) {
        2 => switch (@as(u16, @bitCast(domain[0..2].*))) {
            asUint(u16, "LP") => return @import("domains/lp.zig").processMessage(command),
            else => {},
        },
        3 => switch (@as(u24, @bitCast(domain[0..3].*))) {
            asUint(u24, "DOM") => return @import("domains/dom.zig").processMessage(command),
            asUint(u24, "Log") => return @import("domains/log.zig").processMessage(command),
            asUint(u24, "CSS") => return @import("domains/css.zig").processMessage(command),
            else => {},
        },
        4 => switch (@as(u32, @bitCast(domain[0..4].*))) {
            asUint(u32, "Page") => return @import("domains/page.zig").processMessage(command),
            else => {},
        },
        5 => switch (@as(u40, @bitCast(domain[0..5].*))) {
            asUint(u40, "Fetch") => return @import("domains/fetch.zig").processMessage(command),
            asUint(u40, "Input") => return @import("domains/input.zig").processMessage(command),
            else => {},
        },
        6 => switch (@as(u48, @bitCast(domain[0..6].*))) {
            asUint(u48, "Target") => return @import("domains/target.zig").processMessage(command),
            asUint(u48, "Audits") => return @import("domains/audits.zig").processMessage(command),
            asUint(u48, "WebMCP") => return @import("domains/webmcp.zig").processMessage(command),
            else => {},
        },
        7 => switch (@as(u56, @bitCast(domain[0..7].*))) {
            asUint(u56, "Browser") => return @import("domains/browser.zig").processMessage(command),
            asUint(u56, "Runtime") => return @import("domains/runtime.zig").processMessage(command),
            asUint(u56, "Network") => return @import("domains/network.zig").processMessage(command),
            asUint(u56, "Storage") => return @import("domains/storage.zig").processMessage(command),
            asUint(u56, "Console") => return @import("domains/console.zig").processMessage(command),
            else => {},
        },
        8 => switch (@as(u64, @bitCast(domain[0..8].*))) {
            asUint(u64, "Security") => return @import("domains/security.zig").processMessage(command),
            else => {},
        },
        9 => switch (@as(u72, @bitCast(domain[0..9].*))) {
            asUint(u72, "Emulation") => return @import("domains/emulation.zig").processMessage(command),
            asUint(u72, "Inspector") => return @import("domains/inspector.zig").processMessage(command),
            else => {},
        },
        11 => switch (@as(u88, @bitCast(domain[0..11].*))) {
            asUint(u88, "Performance") => return @import("domains/performance.zig").processMessage(command),
            else => {},
        },
        13 => switch (@as(u104, @bitCast(domain[0..13].*))) {
            asUint(u104, "Accessibility") => return @import("domains/accessibility.zig").processMessage(command),
            else => {},
        },

        else => {},
    }

    return error.UnknownDomain;
}

fn isValidSessionId(self: *const CDP, input_session_id: []const u8) bool {
    const browser_context = &(self.browser_context orelse return false);
    const session_id = browser_context.session_id orelse return false;
    return std.mem.eql(u8, session_id, input_session_id);
}

pub fn createBrowserContext(self: *CDP) ![]const u8 {
    if (self.browser_context != null) {
        return error.AlreadyExists;
    }
    const id = self.browser_context_id_gen.next();

    self.browser_context = @as(BrowserContext, undefined);
    const browser_context = &self.browser_context.?;

    try BrowserContext.init(browser_context, id, self);
    return id;
}

pub fn disposeBrowserContext(self: *CDP, browser_context_id: []const u8) bool {
    const bc = &(self.browser_context orelse return false);
    if (std.mem.eql(u8, bc.id, browser_context_id) == false) {
        return false;
    }
    bc.deinit();
    self.browser.closeSession();
    self.browser_context = null;
    _ = self.browser_context_arena.reset(.{ .retain_with_limit = 1024 * 16 });
    return true;
}

const SendEventOpts = struct {
    session_id: ?[]const u8 = null,
};
pub fn sendEvent(self: *CDP, method: []const u8, p: anytype, opts: SendEventOpts) !void {
    return self.sendJSON(.{
        .method = method,
        .params = if (comptime @typeInfo(@TypeOf(p)) == .null) struct {}{} else p,
        .sessionId = opts.session_id,
    });
}

pub const BrowserContext = struct {
    const Node = @import("Node.zig");
    const AXNode = @import("AXNode.zig");

    const CapturedResponse = struct {
        must_encode: bool,
        data: std.ArrayList(u8),
    };

    // Key for `captured_responses`. Documents are keyed by `loader_id`,
    // everything else by `request_id` — the two id-spaces are independent
    // counters and overlap numerically (loader 1 / request 1, loader 2 /
    // request 2, ...), so the map key has to carry the namespace or
    // entries collide. The wire-format prefix (`LID-` / `REQ-`) provides
    // the same disambiguation on lookup; see `idFromRequestId` in
    // domains/network.zig.
    pub const CapturedResponseKey = struct {
        kind: enum { request, loader },
        id: u32,
    };

    id: []const u8,
    cdp: *CDP,

    // Represents the browser session. There is no equivalent in CDP. For
    // all intents and purpose, from CDP's point of view our Browser and
    // our Session more or less maps to a BrowserContext. THIS HAS ZERO
    // RELATION TO SESSION_ID
    session: *Session,

    // Tied to the lifetime of the BrowserContext
    arena: Allocator,

    // Tied to the lifetime of 1 page rendered in the BrowserContext.
    frame_arena: Allocator,

    // From the parent's notification_arena.allocator(). Most of the CDP
    // code paths deal with a cmd which has its own arena (from the
    // message_arena). But notifications happen outside of the typical CDP
    // request->response, and thus don't have a cmd and don't have an arena.
    notification_arena: Allocator,

    // Maps to our Page. (There are other types of targets, but we only
    // deal with "pages" for now). Since we only allow 1 open page at a
    // time, we only have 1 target_id.
    target_id: ?[14]u8,

    // The CDP session_id. After the target/page is created, the client
    // "attaches" to it (either explicitly or automatically). We return a
    // "sessionId" which identifies this link. `sessionId` is the how
    // the CDP client informs us what it's trying to manipulate. Because we
    // only support 1 BrowserContext at a time, and 1 page at a time, this
    // is all pretty straightforward, but it still needs to be enforced, i.e.
    // if we get a request with a sessionId that doesn't match the current one
    // we should reject it.
    session_id: ?[]const u8,

    security_origin: []const u8,
    page_life_cycle_events: bool,
    secure_context_type: []const u8,
    node_registry: Node.Registry,
    node_search_list: Node.Search.List,

    inspector_session: *js.Inspector.Session,
    isolated_worlds: std.ArrayList(*IsolatedWorld),

    // Scripts registered via Page.addScriptToEvaluateOnNewDocument.
    // Evaluated in each new document after navigation completes.
    scripts_on_new_document: std.ArrayList(ScriptOnNewDocument) = .empty,
    next_script_id: u32 = 1,

    http_proxy_changed: bool = false,
    user_agent_changed: bool = false,

    // Extra headers to add to all requests.
    extra_headers: std.ArrayList([*c]const u8) = .empty,

    intercept_state: InterceptState,

    // When network is enabled, we'll capture the transfer.id -> body
    // This is awfully memory intensive, but our underlying http client and
    // its users (script manager and frame) correctly do not hold the body
    // memory longer than they have to. In fact, the main request is only
    // ever streamed. So if CDP is the only thing that needs bodies in
    // memory for an arbitrary amount of time, then that's where we're going
    // to store the,
    captured_responses: std.AutoHashMapUnmanaged(CapturedResponseKey, CapturedResponse),

    notification: *Notification,

    // Pre-armed response for the next JS dialog (alert/confirm/prompt).
    // Set by Page.handleJavaScriptDialog; consumed (and cleared) when the
    // next javascript_dialog_opening notification is dispatched. Strings
    // are duplicated into self.arena so they outlive the CDP command's
    // own message arena.
    pending_dialog_response: ?Notification.DialogResponse = null,

    // webmcp tool invocation
    invocation_id_gen: InvocationIdGen = .{},
    // WebMCP domain state. Populated when `WebMCP.enable` is received.
    webmcp_invocations: std.AutoHashMapUnmanaged(u32, *@import("domains/webmcp.zig").Invocation) = .empty,

    fn init(self: *BrowserContext, id: []const u8, cdp: *CDP) !void {
        const allocator = cdp.allocator;

        // Create notification for this BrowserContext
        const notification = try Notification.init(allocator);
        errdefer notification.deinit();

        const session = try cdp.browser.newSession(notification);
        if (cdp.app.config.cookieFile()) |cookie_path| {
            lp.cookies.loadFromFile(session, cookie_path);
        }

        const browser = &cdp.browser;
        const inspector_session = browser.env.inspector.?.startSession(self);
        errdefer browser.env.inspector.?.stopSession();

        var registry = Node.Registry.init(allocator);
        errdefer registry.deinit();

        self.* = .{
            .id = id,
            .cdp = cdp,
            .target_id = null,
            .session_id = null,
            .session = session,
            .security_origin = URL_BASE,
            .secure_context_type = "Secure", // TODO = enum
            .page_life_cycle_events = false, // TODO; Target based value
            .node_registry = registry,
            .node_search_list = undefined,
            .isolated_worlds = .empty,
            .inspector_session = inspector_session,
            .frame_arena = cdp.frame_arena.allocator(),
            .arena = cdp.browser_context_arena.allocator(),
            .notification_arena = cdp.notification_arena.allocator(),
            .intercept_state = try InterceptState.init(allocator),
            .captured_responses = .empty,
            .notification = notification,
        };
        self.node_search_list = Node.Search.List.init(allocator, &self.node_registry);
        errdefer self.deinit();

        try notification.register(.frame_remove, self, onFrameRemove);
        try notification.register(.frame_created, self, onFrameCreated);
        try notification.register(.frame_navigate, self, onFrameNavigate);
        try notification.register(.frame_navigated, self, onFrameNavigated);
        try notification.register(.frame_child_frame_created, self, onFrameChildFrameCreated);
        try notification.register(.frame_dom_content_loaded, self, onFrameDOMContentLoaded);
        try notification.register(.frame_loaded, self, onFrameLoaded);
        try notification.register(.javascript_dialog_opening, self, onJavascriptDialogOpening);
    }

    pub fn deinit(self: *BrowserContext) void {
        const browser = &self.cdp.browser;
        const env = &browser.env;

        // resetContextGroup detach the inspector from all contexts.
        // It appends async tasks, so we make sure we run the message loop
        // before deinit it.
        env.inspector.?.resetContextGroup();
        env.inspector.?.stopSession();

        // abort all intercepted requests before closing the session/page
        // since some of these might callback into the page/scriptmanager.
        // intercept_state stores ids — look each one up; if it's already
        // gone (out-of-band destroy), there's nothing to abort, but the
        // intercepted counter still needs decrementing because we
        // incremented it on pause.
        const http_client = &browser.http_client;
        for (self.intercept_state.pendingIntercepts()) |transfer_id| {
            lp.assert(
                http_client.interception_layer.intercepted > 0,
                "BrowserContext.deinit.intercepted",
                .{ .value = http_client.interception_layer.intercepted },
            );
            http_client.interception_layer.intercepted -= 1;
            if (http_client.findTransfer(transfer_id)) |transfer| {
                transfer.abort(error.ClientDisconnect);
            }
        }

        // Notify any CDP client waiting on an in-flight WebMCP invocation
        // before the V8 context (and its promise callbacks) get torn down
        // by browser.closeSession below.
        @import("domains/webmcp.zig").cancelAllPending(self);

        for (self.isolated_worlds.items) |world| {
            world.deinit();
        }
        self.isolated_worlds.clearRetainingCapacity();

        // do this before closeSession, since we don't want to process any
        // new notification (Or maybe, instead of the deinit above, we just
        // rely on those notifications to do our normal cleanup?)

        self.notification.unregisterAll(self);

        // If the session has a frame, we need to clear it first. The page
        // context is always nested inside of the isolated world context,
        // so we need to shutdown the page one first.
        browser.closeSession();

        self.node_registry.deinit();
        self.node_search_list.deinit();
        self.notification.deinit();

        if (self.http_proxy_changed) {
            // has to be called after browser.closeSession, since it won't
            // work if there are active connections.
            browser.http_client.changeProxy(null) catch |err| {
                log.warn(.http, "changeProxy", .{ .err = err });
            };
        }
        if (self.user_agent_changed) {
            browser.http_client.clearUserAgentOverride();
        }
        self.intercept_state.deinit();
    }

    pub fn reset(self: *BrowserContext) void {
        self.node_registry.reset();
        self.node_search_list.reset();
    }

    pub fn createIsolatedWorld(self: *BrowserContext, world_name: []const u8, grant_universal_access: bool) !*IsolatedWorld {
        const browser = &self.cdp.browser;
        const arena = try browser.arena_pool.acquire(.small, "IsolatedWorld");
        errdefer browser.arena_pool.release(arena);

        const call_arena = try browser.arena_pool.acquire(.tiny, "IsolatedWorld.call_arena");
        errdefer browser.arena_pool.release(call_arena);

        const world = try arena.create(IsolatedWorld);
        world.* = .{
            .arena = arena,
            .call_arena = call_arena,
            .context = null,
            .browser = browser,
            .name = try arena.dupe(u8, world_name),
            .grant_universal_access = grant_universal_access,
        };

        try self.isolated_worlds.append(self.arena, world);

        return world;
    }

    pub fn nodeWriter(self: *BrowserContext, root: *const Node, opts: Node.Writer.Opts) Node.Writer {
        return .{
            .root = root,
            .depth = opts.depth,
            .exclude_root = opts.exclude_root,
            .registry = &self.node_registry,
        };
    }

    pub fn axnodeWriter(self: *BrowserContext, temp_arena: Allocator, root: *const Node, opts: AXNode.Writer.Opts) !AXNode.Writer {
        // Bind the writer to the frame that owns the root node, not whatever
        // happens to be `currentFrame`. Name resolution (`Label.findLabelByFor`
        // against `ownerDocument`) and visibility checks (`frame._style_manager`)
        // are per-frame; getting this wrong on cross-frame queries produces
        // names/visibility from the wrong document.
        const fallback = self.session.currentFrame() orelse return error.FrameNotLoaded;
        const frame = root.dom.ownerFrame(fallback);
        const cache = try frame.call_arena.create(Element.VisibilityCache);
        cache.* = .empty;
        const label_index = try frame.call_arena.create(Label.LabelByForIndex);
        label_index.* = .{};
        return .{
            .frame = frame,
            .root = root,
            .registry = &self.node_registry,
            .visibility_cache = cache,
            .label_index = label_index,
            .temp_arena = temp_arena,
            .filter = opts.filter,
        };
    }

    pub fn getURL(self: *const BrowserContext) ?[:0]const u8 {
        const frame = self.session.currentFrame() orelse return null;
        const url = frame.url;
        return if (url.len == 0) null else url;
    }

    pub fn getTitle(self: *const BrowserContext) ?[]const u8 {
        const frame = self.session.currentFrame() orelse return null;
        return frame.getTitle() catch |err| {
            log.err(.cdp, "page title", .{ .err = err });
            return null;
        };
    }

    pub fn networkEnable(self: *BrowserContext) !void {
        try self.notification.register(.http_request_fail, self, onHttpRequestFail);
        try self.notification.register(.http_request_start, self, onHttpRequestStart);
        try self.notification.register(.http_request_done, self, onHttpRequestDone);
        try self.notification.register(.http_response_data, self, onHttpResponseData);
        try self.notification.register(.http_response_header_done, self, onHttpResponseHeadersDone);
        try self.notification.register(.http_request_served_from_cache, self, onHttpRequestServedFromCache);
    }

    pub fn networkDisable(self: *BrowserContext) void {
        self.notification.unregister(.http_request_fail, self);
        self.notification.unregister(.http_request_start, self);
        self.notification.unregister(.http_request_done, self);
        self.notification.unregister(.http_response_data, self);
        self.notification.unregister(.http_response_header_done, self);
        self.notification.unregister(.http_request_served_from_cache, self);
    }

    pub fn fetchEnable(self: *BrowserContext, authRequests: bool) !void {
        try self.notification.register(.http_request_intercept, self, onHttpRequestIntercept);
        if (authRequests) {
            try self.notification.register(.http_request_auth_required, self, onHttpRequestAuthRequired);
        }
    }

    pub fn fetchDisable(self: *BrowserContext) void {
        self.notification.unregister(.http_request_intercept, self);
        self.notification.unregister(.http_request_auth_required, self);
    }

    pub fn lifecycleEventsEnable(self: *BrowserContext) !void {
        self.page_life_cycle_events = true;
        try self.notification.register(.frame_network_idle, self, onFrameNetworkIdle);
        try self.notification.register(.frame_network_almost_idle, self, onFrameNetworkAlmostIdle);
    }

    pub fn lifecycleEventsDisable(self: *BrowserContext) void {
        self.page_life_cycle_events = false;
        self.notification.unregister(.frame_network_idle, self);
        self.notification.unregister(.frame_network_almost_idle, self);
    }

    pub fn consoleEnable(self: *BrowserContext) !void {
        try self.notification.register(.console_message, self, onConsoleMessage);
    }

    pub fn consoleDisable(self: *BrowserContext) void {
        self.notification.unregister(.console_message, self);
    }

    pub fn runtimeEnable(self: *BrowserContext) !void {
        try self.notification.register(.runtime_console_message, self, onRuntimeConsoleMessage);
    }

    pub fn runtimeDisable(self: *BrowserContext) void {
        self.notification.unregister(.runtime_console_message, self);
    }

    pub fn webmcpEnable(self: *BrowserContext) !void {
        try self.notification.register(.model_context_tool_added, self, onModelContextToolAdded);
        try self.notification.register(.model_context_tool_removed, self, onModelContextToolRemoved);
    }

    pub fn webmcpDisable(self: *BrowserContext) void {
        self.notification.unregister(.model_context_tool_added, self);
        self.notification.unregister(.model_context_tool_removed, self);
    }

    pub fn onModelContextToolAdded(ctx: *anyopaque, event: *const Notification.ModelContextToolEvent) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/webmcp.zig").onToolAdded(self, event);
    }

    pub fn onModelContextToolRemoved(ctx: *anyopaque, event: *const Notification.ModelContextToolEvent) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/webmcp.zig").onToolRemoved(self, event);
    }

    pub fn onFrameRemove(ctx: *anyopaque, _: Notification.FrameRemove) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        @import("domains/page.zig").frameRemove(self);
    }

    pub fn onFrameCreated(ctx: *anyopaque, frame: *Frame) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/page.zig").frameCreated(self, frame);
    }

    pub fn onFrameNavigate(ctx: *anyopaque, msg: *const Notification.FrameNavigate) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/page.zig").frameNavigate(self, msg);
    }

    pub fn onFrameNavigated(ctx: *anyopaque, msg: *const Notification.FrameNavigated) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        defer self.resetNotificationArena();
        return @import("domains/page.zig").frameNavigated(self.notification_arena, self, msg);
    }

    pub fn onFrameChildFrameCreated(ctx: *anyopaque, msg: *const Notification.FrameChildFrameCreated) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/page.zig").frameChildFrameCreated(self, msg);
    }

    pub fn onFrameNetworkIdle(ctx: *anyopaque, msg: *const Notification.FrameNetworkIdle) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/page.zig").frameNetworkIdle(self, msg);
    }

    pub fn onFrameNetworkAlmostIdle(ctx: *anyopaque, msg: *const Notification.FrameNetworkAlmostIdle) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/page.zig").frameNetworkAlmostIdle(self, msg);
    }

    pub fn onHttpRequestStart(ctx: *anyopaque, msg: *const Notification.RequestStart) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        try @import("domains/network.zig").httpRequestStart(self, msg);
    }

    pub fn onHttpRequestIntercept(ctx: *anyopaque, msg: *const Notification.RequestIntercept) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        try @import("domains/fetch.zig").requestIntercept(self, msg);
    }

    pub fn onHttpRequestFail(ctx: *anyopaque, msg: *const Notification.RequestFail) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/network.zig").httpRequestFail(self, msg);
    }

    pub fn onFrameDOMContentLoaded(ctx: *anyopaque, msg: *const Notification.FrameDOMContentLoaded) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/page.zig").frameDOMContentLoaded(self, msg);
    }

    pub fn onFrameLoaded(ctx: *anyopaque, msg: *const Notification.FrameLoaded) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/page.zig").frameLoaded(self, msg);
    }

    pub fn onJavascriptDialogOpening(ctx: *anyopaque, msg: *const Notification.JavascriptDialogOpening) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/page.zig").javascriptDialogOpening(self, msg);
    }

    fn keyFromTransfer(transfer: *const Transfer) CDP.BrowserContext.CapturedResponseKey {
        return if (transfer.req.resource_type == .document)
            .{ .kind = .loader, .id = transfer.req.loader_id }
        else
            .{ .kind = .request, .id = transfer.id };
    }

    pub fn onHttpResponseHeadersDone(ctx: *anyopaque, msg: *const Notification.ResponseHeaderDone) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        defer self.resetNotificationArena();

        const arena = self.frame_arena;

        // Prepare the captured response value.
        const key = keyFromTransfer(msg.transfer);
        const gop = try self.captured_responses.getOrPut(arena, key);
        if (!gop.found_existing) {
            gop.value_ptr.* = .{
                .data = .empty,
                // Encode the data in base64 by default, but don't encode
                // for well known content-type.
                .must_encode = blk: {
                    const response = msg.response;
                    if (response.contentType()) |ct| {
                        const mime = try Mime.parse(ct);

                        if (!mime.isText()) {
                            break :blk true;
                        }

                        if (std.mem.eql(u8, "UTF-8", mime.charsetString())) {
                            break :blk false;
                        }
                    }
                    break :blk true;
                },
            };
        }

        return @import("domains/network.zig").httpResponseHeaderDone(self.notification_arena, self, msg);
    }

    pub fn onHttpRequestDone(ctx: *anyopaque, msg: *const Notification.RequestDone) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/network.zig").httpRequestDone(self, msg);
    }

    pub fn onHttpResponseData(ctx: *anyopaque, msg: *const Notification.ResponseData) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        const arena = self.frame_arena;

        const key = keyFromTransfer(msg.transfer);
        const resp = self.captured_responses.getPtr(key) orelse lp.assert(false, "onHttpResponseData missing captured response", .{});

        return resp.data.appendSlice(arena, msg.data);
    }

    pub fn onHttpRequestAuthRequired(ctx: *anyopaque, data: *const Notification.RequestAuthRequired) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        defer self.resetNotificationArena();
        try @import("domains/fetch.zig").requestAuthRequired(self, data);
    }

    pub fn onHttpRequestServedFromCache(ctx: *anyopaque, msg: *const Notification.RequestServedFromCache) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        return @import("domains/network.zig").httpServedFromCache(self, msg);
    }

    pub fn onConsoleMessage(ctx: *anyopaque, msg: *const Notification.ConsoleMessage) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        defer self.resetNotificationArena();
        return @import("domains/console.zig").consoleMessage(self.notification_arena, self, msg);
    }

    pub fn onRuntimeConsoleMessage(ctx: *anyopaque, msg: *const Notification.ConsoleMessage) !void {
        const self: *BrowserContext = @ptrCast(@alignCast(ctx));
        defer self.resetNotificationArena();
        return @import("domains/runtime.zig").consoleMessage(self.notification_arena, self, msg);
    }

    fn resetNotificationArena(self: *BrowserContext) void {
        defer _ = self.cdp.notification_arena.reset(.{ .retain_with_limit = 1024 * 64 });
    }

    pub fn callInspector(self: *const BrowserContext, msg: []const u8) void {
        self.inspector_session.send(msg);
        self.session.browser.env.runMicrotasks();
    }

    pub fn onInspectorResponse(ctx: *anyopaque, _: u32, msg: []const u8) void {
        sendInspectorMessage(@ptrCast(@alignCast(ctx)), msg) catch |err| {
            log.err(.cdp, "send inspector response", .{ .err = err });
        };
    }

    pub fn onInspectorEvent(ctx: *anyopaque, msg: []const u8) void {
        if (log.enabled(.cdp, .debug)) {
            // msg should be {"method":<method>,...
            lp.assert(std.mem.startsWith(u8, msg, "{\"method\":"), "onInspectorEvent prefix", .{});
            const method_end = std.mem.indexOfScalar(u8, msg, ',') orelse {
                log.err(.cdp, "invalid inspector event", .{ .msg = msg });
                return;
            };
            const method = msg[10..method_end];
            log.debug(.cdp, "inspector event", .{ .method = method });
        }

        sendInspectorMessage(@ptrCast(@alignCast(ctx)), msg) catch |err| {
            log.err(.cdp, "send inspector event", .{ .err = err });
        };
    }

    // This is hacky x 2. First, we create the JSON payload by gluing our
    // session_id onto it. Second, we're much more client/websocket aware than
    // we should be.
    fn sendInspectorMessage(self: *BrowserContext, msg: []const u8) !void {
        const session_id = self.session_id orelse {
            // We no longer have an active session. What should we do
            // in this case?
            return;
        };

        const cdp = self.cdp;
        const allocator = cdp.conn.send_arena.allocator();

        const field = ",\"sessionId\":\"";

        // + 1 for the closing quote after the session id
        // + 10 for the max websocket header
        const message_len = msg.len + session_id.len + 1 + field.len + 10;

        var buf: std.ArrayList(u8) = .{};
        buf.ensureTotalCapacity(allocator, message_len) catch |err| {
            log.err(.cdp, "inspector buffer", .{ .err = err });
            return;
        };

        // reserve 10 bytes for websocket header
        buf.appendSliceAssumeCapacity(&.{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 });

        // -1  because we dont' want the closing brace '}'
        buf.appendSliceAssumeCapacity(msg[0 .. msg.len - 1]);
        buf.appendSliceAssumeCapacity(field);
        buf.appendSliceAssumeCapacity(session_id);
        buf.appendSliceAssumeCapacity("\"}");
        if (comptime IS_DEBUG) {
            std.debug.assert(buf.items.len == message_len);
        }

        try cdp.conn.sendJSONRaw(buf);
    }
};

/// see: https://chromium.googlesource.com/chromium/src/+/master/third_party/blink/renderer/bindings/core/v8/V8BindingDesign.md#world
/// The current understanding. An isolated world lives in the same isolate, but a separated context.
/// Clients create this to be able to create variables and run code without interfering with the
/// normal namespace and values of the webframe. Similar to the main context we need to pretend to recreate it after
/// a executionContextsCleared event which happens when navigating to a new frame. A client can have a command be executed
const ScriptOnNewDocument = struct {
    identifier: u32,
    source: []const u8,
};

/// in the isolated world by using its Context ID or the worldName.
/// grantUniversalAccess Indicates whether the isolated world can reference objects like the DOM or other JS Objects.
/// An isolated world has it's own instance of globals like Window.
/// Generally the client needs to resolve a node into the isolated world to be able to work with it.
/// An object id is unique across all contexts, different object ids can refer to the same Node in different contexts.
const IsolatedWorld = struct {
    arena: Allocator,
    call_arena: Allocator,
    browser: *Browser,
    name: []const u8,
    context: ?*js.Context = null,
    grant_universal_access: bool,

    // Identity tracking for this isolated world (separate from main world).
    // This ensures CDP inspector contexts don't share v8::Globals with main world.
    identity: js.Identity = .{},

    pub fn deinit(self: *IsolatedWorld) void {
        self.removeContext();
        self.browser.arena_pool.release(self.call_arena);
        self.browser.arena_pool.release(self.arena);
    }

    pub fn removeContext(self: *IsolatedWorld) void {
        if (self.context) |ctx| {
            self.browser.env.destroyContext(ctx);
            self.context = null;
        }
        // I don't think it's possible to have any identity without a context,
        // but there's no harm in being safe.
        self.identity.deinit();
        self.identity = .{};
    }

    // The isolate world must share at least some of the state with the related frame, specifically the DocumentHTML
    // (assuming grantUniversalAccess will be set to True!).
    // We just created the world and the frame. The frame's state lives in the session, but is update on navigation.
    // This also means this pointer becomes invalid after removePage until a new frame is created.
    // Currently we have only 1 frame and thus also only 1 state in the isolate world.
    pub fn createContext(self: *IsolatedWorld, frame: *Frame) !*js.Context {
        if (self.context == null) {
            const ctx = try self.browser.env.createContext(frame, .{
                .identity = &self.identity,
                .identity_arena = self.arena,
                .call_arena = self.call_arena,
                .debug_name = "IsolatedContext",
            });
            self.context = ctx;
        } else {
            log.warn(.cdp, "not implemented", .{
                .feature = "createContext: Not implemented second isolated context creation",
                .info = "reuse existing context",
            });
        }
        return self.context.?;
    }
};

// This is a generic because when we send a result we have two different
// behaviors. Normally, we're sending the result to the client. But in some cases
// we want to capture the result. So we want the command.sendResult to be
// generic.
pub const Command = struct {
    // A misc arena that can be used for any allocation for processing
    // the message
    arena: Allocator,

    // reference to our CDP instance
    cdp: *CDP,

    // The browser context this command targets
    browser_context: ?*BrowserContext,

    // The command input (the id, optional session_id, params, ...)
    input: Input,

    // In most cases, Sender is going to be cdp itself. We'll call
    // sender.sendJSON() and CDP will send it to the client. But some
    // commands are dispatched internally, in which cases the Sender will
    // be code to capture the data that we were "sending".
    sender: Sender,

    const Sender = union(enum) {
        cdp: *CDP,
        capture: *std.Io.Writer,

        pub fn sendJSON(self: Sender, message: anytype) !void {
            switch (self) {
                .cdp => |cdp| return cdp.sendJSON(message),
                .capture => |writer| {
                    return std.json.Stringify.value(message, .{
                        .emit_null_optional_fields = false,
                    }, writer);
                },
            }
        }
    };

    pub fn params(self: *const Command, comptime T: type) !?T {
        if (self.input.params) |p| {
            return try json.parseFromSliceLeaky(
                T,
                self.arena,
                p.raw,
                .{ .ignore_unknown_fields = true },
            );
        }
        return null;
    }

    pub fn createBrowserContext(self: *Command) !*BrowserContext {
        _ = try self.cdp.createBrowserContext();
        self.browser_context = &(self.cdp.browser_context.?);
        return self.browser_context.?;
    }

    const SendResultOpts = struct {
        include_session_id: bool = true,
    };
    pub fn sendResult(self: *Command, result: anytype, opts: SendResultOpts) !void {
        return self.sender.sendJSON(.{
            .id = self.input.id,
            .result = if (comptime @typeInfo(@TypeOf(result)) == .null) struct {}{} else result,
            .sessionId = if (opts.include_session_id) self.input.session_id else null,
        });
    }

    pub fn sendEvent(self: *Command, method: []const u8, p: anytype, opts: SendEventOpts) !void {
        // Events ALWAYS go to the client. self.sender should not be used
        return self.cdp.sendEvent(method, p, opts);
    }

    const SendErrorOpts = struct {
        include_session_id: bool = true,
    };
    pub fn sendError(self: *Command, code: i32, message: []const u8, opts: SendErrorOpts) !void {
        return self.sender.sendJSON(.{
            .id = self.input.id,
            .@"error" = .{ .code = code, .message = message },
            .sessionId = if (opts.include_session_id) self.input.session_id else null,
        });
    }

    const Input = struct {
        // When we reply to a message, we echo back the message id
        id: ?i64,

        // The "action" of the message.Given a method of "LOG.enable", the
        // action is "enable"
        action: []const u8,

        // See notes in BrowserContext about session_id
        session_id: ?[]const u8,

        // Unparsed / untyped input.params.
        params: ?InputParams,

        // The full raw json input
        json: []const u8,
    };
};

// When we parse a JSON message from the client, this is the structure
// we always expect. Parsed on the Network thread inside
// Connection.handleMessage; the slices reference the raw JSON bytes
// (or arena allocations for fields that needed unescaping). Both
// outlive the InputMessage for the inbox message's lifetime.
pub const InputMessage = struct {
    id: ?i64 = null,
    method: []const u8,
    params: ?InputParams = null,
    sessionId: ?[]const u8 = null,
};

// The JSON "params" field changes based on the "method". Initially, we just
// capture the raw json object (including the opening and closing braces).
// Then, when we're processing the message, and we know what type it is, we
// can parse it (in Disaptch(T).params).
pub const InputParams = struct {
    raw: []const u8,

    pub fn jsonParse(
        _: Allocator,
        scanner: *json.Scanner,
        _: json.ParseOptions,
    ) !InputParams {
        const height = scanner.stackHeight();

        const start = scanner.cursor;
        if (try scanner.next() != .object_begin) {
            return error.UnexpectedToken;
        }
        try scanner.skipUntilStackHeight(height);
        const end = scanner.cursor;

        return .{ .raw = scanner.input[start..end] };
    }
};

fn asUint(comptime T: type, comptime string: []const u8) T {
    return @bitCast(string[0..string.len].*);
}

const testing = @import("testing.zig");
test "cdp: invalid json" {
    var ctx = try testing.context();
    defer ctx.deinit();

    try testing.expectError(error.InvalidJSON, ctx.processMessage("invalid"));

    // method is required
    try testing.expectError(error.InvalidJSON, ctx.processMessage(.{}));

    try ctx.processMessage(.{
        .method = "Target",
    });
    try ctx.expectSentError(-31998, "InvalidMethod", .{});

    try ctx.processMessage(.{
        .method = "Unknown.domain",
    });
    try ctx.expectSentError(-31998, "UnknownDomain", .{});

    try ctx.processMessage(.{
        .method = "Target.over9000",
    });
    try ctx.expectSentError(-31998, "UnknownMethod", .{});
}

test "cdp: invalid sessionId" {
    var ctx = try testing.context();
    defer ctx.deinit();

    {
        // we have no browser context
        try ctx.processMessage(.{ .method = "Hi", .sessionId = "nope" });
        try ctx.expectSentError(-32001, "Unknown sessionId", .{});
    }

    {
        // we have a browser context but no session_id
        _ = try ctx.loadBrowserContext(.{});
        try ctx.processMessage(.{ .method = "Hi", .sessionId = "BC-Has-No-SessionId" });
        try ctx.expectSentError(-32001, "Unknown sessionId", .{});
    }

    {
        // we have a browser context with a different session_id
        _ = try ctx.loadBrowserContext(.{ .session_id = "SESS-2" });
        try ctx.processMessage(.{ .method = "Hi", .sessionId = "SESS-1" });
        try ctx.expectSentError(-32001, "Unknown sessionId", .{});
    }
}

test "cdp: STARTUP sessionId" {
    var ctx = try testing.context();
    defer ctx.deinit();

    {
        // we have no browser context
        try ctx.processMessage(.{ .id = 2, .method = "Hi", .sessionId = "STARTUP" });
        try ctx.expectSentResult(null, .{ .id = 2, .index = 0, .session_id = "STARTUP" });
    }

    {
        // we have a browser context but no session_id
        _ = try ctx.loadBrowserContext(.{});
        try ctx.processMessage(.{ .id = 3, .method = "Hi", .sessionId = "STARTUP" });
        try ctx.expectSentResult(null, .{ .id = 3, .index = 1, .session_id = "STARTUP" });
    }

    {
        // we have a browser context with a different session_id
        _ = try ctx.loadBrowserContext(.{ .session_id = "SESS-2" });
        try ctx.processMessage(.{ .id = 4, .method = "Hi", .sessionId = "STARTUP" });
        try ctx.expectSentResult(null, .{ .id = 4, .index = 2, .session_id = "STARTUP" });
    }
}