Expand the lifetime of the XHR reference

We need to take the self-reference to the XHR object as soon as the request is made. Previously, we were waiting until we got the start callback, but v8 could (and does) drop the reference before that happens. Unfortunately, that means we can no longer use _transfer == null to tell if we own a reference or not, so a new boolean was added.
2026-03-31 09:29:42 +00:00 · 2026-03-31 16:46:31 +08:00
21 changed files with 643 additions and 650 deletions
--- a/src/browser/webapi/net/XMLHttpRequest.zig
+++ b/src/browser/webapi/net/XMLHttpRequest.zig
@@ -44,6 +44,7 @@ _page: *Page,
 _proto: *XMLHttpRequestEventTarget,
 _arena: Allocator,
 _transfer: ?*HttpClient.Transfer = null,
+_has_ref: bool = false,

 _url: [:0]const u8 = "",
 _method: net_http.Method = .GET,
@@ -136,6 +137,14 @@ pub fn deinit(self: *XMLHttpRequest, session: *Session) void {
    session.releaseArena(self._arena);
 }

+fn releaseSelfRef(self: *XMLHttpRequest) void {
+    if (self._has_ref == false) {
+        return;
+    }
+    self.releaseRef(self._page._session);
+    self._has_ref = false;
+}
+
 pub fn releaseRef(self: *XMLHttpRequest, session: *Session) void {
    self._rc.release(self, session);
 }
@@ -252,6 +261,8 @@ pub fn send(self: *XMLHttpRequest, body_: ?[]const u8) !void {
        .error_callback = httpErrorCallback,
        .shutdown_callback = httpShutdownCallback,
    });
+    self.acquireRef();
+    self._has_ref = true;
 }

 fn handleBlobUrl(self: *XMLHttpRequest, page: *Page) !void {
@@ -393,7 +404,6 @@ fn httpStartCallback(transfer: *HttpClient.Transfer) !void {
        log.debug(.http, "request start", .{ .method = self._method, .url = self._url, .source = "xhr" });
    }
    self._transfer = transfer;
-    self.acquireRef();
 }

 fn httpHeaderCallback(transfer: *HttpClient.Transfer, header: net_http.Header) !void {
@@ -501,8 +511,8 @@ fn httpErrorCallback(ctx: *anyopaque, err: anyerror) void {
    self.handleError(err);
    if (self._transfer != null) {
        self._transfer = null;
-        self.releaseRef(self._page._session);
    }
+    self.releaseSelfRef();
 }

 fn httpShutdownCallback(ctx: *anyopaque) void {
@@ -515,8 +525,8 @@ pub fn abort(self: *XMLHttpRequest) void {
    if (self._transfer) |transfer| {
        self._transfer = null;
        transfer.abort(error.Abort);
-        self.releaseRef(self._page._session);
    }
+    self.releaseSelfRef();
 }

 fn handleError(self: *XMLHttpRequest, err: anyerror) void {
--- a/src/cdp/CDP.zig
+++ b/src/cdp/CDP.zig
--- a/src/cdp/domains/accessibility.zig
+++ b/src/cdp/domains/accessibility.zig
@@ -18,9 +18,8 @@

 const std = @import("std");
 const id = @import("../id.zig");
-const CDP = @import("../CDP.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
        disable,
@@ -33,15 +32,15 @@ pub fn processMessage(cmd: *CDP.Command) !void {
        .getFullAXTree => return getFullAXTree(cmd),
    }
 }
-fn enable(cmd: *CDP.Command) !void {
+fn enable(cmd: anytype) !void {
    return cmd.sendResult(null, .{});
 }

-fn disable(cmd: *CDP.Command) !void {
+fn disable(cmd: anytype) !void {
    return cmd.sendResult(null, .{});
 }

-fn getFullAXTree(cmd: *CDP.Command) !void {
+fn getFullAXTree(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        depth: ?i32 = null,
        frameId: ?[]const u8 = null,
--- a/src/cdp/domains/browser.zig
+++ b/src/cdp/domains/browser.zig
@@ -17,7 +17,6 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.

 const std = @import("std");
-const CDP = @import("../CDP.zig");

 // TODO: hard coded data
 const PROTOCOL_VERSION = "1.3";
@@ -36,7 +35,7 @@ const PRODUCT = "Chrome/124.0.6367.29";
 const JS_VERSION = "12.4.254.8";
 const DEV_TOOLS_WINDOW_ID = 1923710101;

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        getVersion,
        setPermission,
@@ -58,7 +57,7 @@ pub fn processMessage(cmd: *CDP.Command) !void {
    }
 }

-fn getVersion(cmd: *CDP.Command) !void {
+fn getVersion(cmd: anytype) !void {
    // TODO: pre-serialize?
    return cmd.sendResult(.{
        .protocolVersion = PROTOCOL_VERSION,
@@ -70,7 +69,7 @@ fn getVersion(cmd: *CDP.Command) !void {
 }

 // TODO: noop method
-fn setDownloadBehavior(cmd: *CDP.Command) !void {
+fn setDownloadBehavior(cmd: anytype) !void {
    // const params = (try cmd.params(struct {
    //     behavior: []const u8,
    //     browserContextId: ?[]const u8 = null,
@@ -81,7 +80,7 @@ fn setDownloadBehavior(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{ .include_session_id = false });
 }

-fn getWindowForTarget(cmd: *CDP.Command) !void {
+fn getWindowForTarget(cmd: anytype) !void {
    // const params = (try cmd.params(struct {
    //     targetId: ?[]const u8 = null,
    // })) orelse return error.InvalidParams;
@@ -92,22 +91,22 @@ fn getWindowForTarget(cmd: *CDP.Command) !void {
 }

 // TODO: noop method
-fn setWindowBounds(cmd: *CDP.Command) !void {
+fn setWindowBounds(cmd: anytype) !void {
    return cmd.sendResult(null, .{});
 }

 // TODO: noop method
-fn grantPermissions(cmd: *CDP.Command) !void {
+fn grantPermissions(cmd: anytype) !void {
    return cmd.sendResult(null, .{});
 }

 // TODO: noop method
-fn setPermission(cmd: *CDP.Command) !void {
+fn setPermission(cmd: anytype) !void {
    return cmd.sendResult(null, .{});
 }

 // TODO: noop method
-fn resetPermissions(cmd: *CDP.Command) !void {
+fn resetPermissions(cmd: anytype) !void {
    return cmd.sendResult(null, .{});
 }

--- a/src/cdp/domains/css.zig
+++ b/src/cdp/domains/css.zig
@@ -17,9 +17,8 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.

 const std = @import("std");
-const CDP = @import("../CDP.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
    }, cmd.input.action) orelse return error.UnknownMethod;
--- a/src/cdp/domains/dom.zig
+++ b/src/cdp/domains/dom.zig
@@ -18,18 +18,17 @@

 const std = @import("std");
 const id = @import("../id.zig");
-const CDP = @import("../CDP.zig");
-const Node = @import("../Node.zig");
-
 const log = @import("../../log.zig");
-const dump = @import("../../browser/dump.zig");
-const js = @import("../../browser/js/js.zig");
+const Node = @import("../Node.zig");
 const DOMNode = @import("../../browser/webapi/Node.zig");
 const Selector = @import("../../browser/webapi/selector/Selector.zig");

+const dump = @import("../../browser/dump.zig");
+const js = @import("../../browser/js/js.zig");
+
 const Allocator = std.mem.Allocator;

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
        getDocument,
@@ -70,7 +69,7 @@ pub fn processMessage(cmd: *CDP.Command) !void {
 }

 // https://chromedevtools.github.io/devtools-protocol/tot/DOM/#method-getDocument
-fn getDocument(cmd: *CDP.Command) !void {
+fn getDocument(cmd: anytype) !void {
    const Params = struct {
        // CDP documentation implies that 0 isn't valid, but it _does_ work in Chrome
        depth: i32 = 3,
@@ -90,7 +89,7 @@ fn getDocument(cmd: *CDP.Command) !void {
 }

 // https://chromedevtools.github.io/devtools-protocol/tot/DOM/#method-performSearch
-fn performSearch(cmd: *CDP.Command) !void {
+fn performSearch(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        query: []const u8,
        includeUserAgentShadowDOM: ?bool = null,
@@ -117,7 +116,7 @@ fn performSearch(cmd: *CDP.Command) !void {
 // hierarchy of each nodes.
 // We dispatch event in the reverse order: from the top level to the direct parents.
 // We should dispatch a node only if it has never been sent.
-fn dispatchSetChildNodes(cmd: *CDP.Command, dom_nodes: []const *DOMNode) !void {
+fn dispatchSetChildNodes(cmd: anytype, dom_nodes: []const *DOMNode) !void {
    const arena = cmd.arena;
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    const session_id = bc.session_id orelse return error.SessionIdNotLoaded;
@@ -173,7 +172,7 @@ fn dispatchSetChildNodes(cmd: *CDP.Command, dom_nodes: []const *DOMNode) !void {
 }

 // https://chromedevtools.github.io/devtools-protocol/tot/DOM/#method-discardSearchResults
-fn discardSearchResults(cmd: *CDP.Command) !void {
+fn discardSearchResults(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        searchId: []const u8,
    })) orelse return error.InvalidParams;
@@ -185,7 +184,7 @@ fn discardSearchResults(cmd: *CDP.Command) !void {
 }

 // https://chromedevtools.github.io/devtools-protocol/tot/DOM/#method-getSearchResults
-fn getSearchResults(cmd: *CDP.Command) !void {
+fn getSearchResults(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        searchId: []const u8,
        fromIndex: u32,
@@ -210,7 +209,7 @@ fn getSearchResults(cmd: *CDP.Command) !void {
    return cmd.sendResult(.{ .nodeIds = node_ids[params.fromIndex..params.toIndex] }, .{});
 }

-fn querySelector(cmd: *CDP.Command) !void {
+fn querySelector(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        nodeId: Node.Id,
        selector: []const u8,
@@ -236,7 +235,7 @@ fn querySelector(cmd: *CDP.Command) !void {
    }, .{});
 }

-fn querySelectorAll(cmd: *CDP.Command) !void {
+fn querySelectorAll(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        nodeId: Node.Id,
        selector: []const u8,
@@ -267,7 +266,7 @@ fn querySelectorAll(cmd: *CDP.Command) !void {
    }, .{});
 }

-fn resolveNode(cmd: *CDP.Command) !void {
+fn resolveNode(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        nodeId: ?Node.Id = null,
        backendNodeId: ?u32 = null,
@@ -328,7 +327,7 @@ fn resolveNode(cmd: *CDP.Command) !void {
    } }, .{});
 }

-fn describeNode(cmd: *CDP.Command) !void {
+fn describeNode(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        nodeId: ?Node.Id = null,
        backendNodeId: ?Node.Id = null,
@@ -375,7 +374,7 @@ fn rectToQuad(rect: DOMNode.Element.DOMRect) Quad {
    };
 }

-fn scrollIntoViewIfNeeded(cmd: *CDP.Command) !void {
+fn scrollIntoViewIfNeeded(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        nodeId: ?Node.Id = null,
        backendNodeId: ?u32 = null,
@@ -398,7 +397,7 @@ fn scrollIntoViewIfNeeded(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{});
 }

-fn getNode(arena: Allocator, bc: *CDP.BrowserContext, node_id: ?Node.Id, backend_node_id: ?Node.Id, object_id: ?[]const u8) !*Node {
+fn getNode(arena: Allocator, bc: anytype, node_id: ?Node.Id, backend_node_id: ?Node.Id, object_id: ?[]const u8) !*Node {
    const input_node_id = node_id orelse backend_node_id;
    if (input_node_id) |input_node_id_| {
        return bc.node_registry.lookup_by_id.get(input_node_id_) orelse return error.NodeNotFound;
@@ -418,7 +417,7 @@ fn getNode(arena: Allocator, bc: *CDP.BrowserContext, node_id: ?Node.Id, backend

 // https://chromedevtools.github.io/devtools-protocol/tot/DOM/#method-getContentQuads
 // Related to: https://drafts.csswg.org/cssom-view/#the-geometryutils-interface
-fn getContentQuads(cmd: *CDP.Command) !void {
+fn getContentQuads(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        nodeId: ?Node.Id = null,
        backendNodeId: ?Node.Id = null,
@@ -444,7 +443,7 @@ fn getContentQuads(cmd: *CDP.Command) !void {
    return cmd.sendResult(.{ .quads = &.{quad} }, .{});
 }

-fn getBoxModel(cmd: *CDP.Command) !void {
+fn getBoxModel(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        nodeId: ?Node.Id = null,
        backendNodeId: ?u32 = null,
@@ -473,7 +472,7 @@ fn getBoxModel(cmd: *CDP.Command) !void {
    } }, .{});
 }

-fn requestChildNodes(cmd: *CDP.Command) !void {
+fn requestChildNodes(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        nodeId: Node.Id,
        depth: i32 = 1,
@@ -497,7 +496,7 @@ fn requestChildNodes(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{});
 }

-fn getFrameOwner(cmd: *CDP.Command) !void {
+fn getFrameOwner(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        frameId: []const u8,
    })) orelse return error.InvalidParams;
@@ -513,7 +512,7 @@ fn getFrameOwner(cmd: *CDP.Command) !void {
    return cmd.sendResult(.{ .nodeId = node.id, .backendNodeId = node.id }, .{});
 }

-fn getOuterHTML(cmd: *CDP.Command) !void {
+fn getOuterHTML(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        nodeId: ?Node.Id = null,
        backendNodeId: ?Node.Id = null,
@@ -535,7 +534,7 @@ fn getOuterHTML(cmd: *CDP.Command) !void {
    return cmd.sendResult(.{ .outerHTML = aw.written() }, .{});
 }

-fn requestNode(cmd: *CDP.Command) !void {
+fn requestNode(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        objectId: []const u8,
    })) orelse return error.InvalidParams;
--- a/src/cdp/domains/emulation.zig
+++ b/src/cdp/domains/emulation.zig
@@ -17,10 +17,9 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.

 const std = @import("std");
-const CDP = @import("../CDP.zig");
 const log = @import("../../log.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        setEmulatedMedia,
        setFocusEmulationEnabled,
@@ -39,7 +38,7 @@ pub fn processMessage(cmd: *CDP.Command) !void {
 }

 // TODO: noop method
-fn setEmulatedMedia(cmd: *CDP.Command) !void {
+fn setEmulatedMedia(cmd: anytype) !void {
    // const input = (try const incoming.params(struct {
    //     media: ?[]const u8 = null,
    //     features: ?[]struct{
@@ -52,7 +51,7 @@ fn setEmulatedMedia(cmd: *CDP.Command) !void {
 }

 // TODO: noop method
-fn setFocusEmulationEnabled(cmd: *CDP.Command) !void {
+fn setFocusEmulationEnabled(cmd: anytype) !void {
    // const input = (try const incoming.params(struct {
    //     enabled: bool,
    // })) orelse return error.InvalidParams;
@@ -60,16 +59,16 @@ fn setFocusEmulationEnabled(cmd: *CDP.Command) !void {
 }

 // TODO: noop method
-fn setDeviceMetricsOverride(cmd: *CDP.Command) !void {
+fn setDeviceMetricsOverride(cmd: anytype) !void {
    return cmd.sendResult(null, .{});
 }

 // TODO: noop method
-fn setTouchEmulationEnabled(cmd: *CDP.Command) !void {
+fn setTouchEmulationEnabled(cmd: anytype) !void {
    return cmd.sendResult(null, .{});
 }

-fn setUserAgentOverride(cmd: *CDP.Command) !void {
+fn setUserAgentOverride(cmd: anytype) !void {
    log.info(.app, "setUserAgentOverride ignored", .{});
    return cmd.sendResult(null, .{});
 }
--- a/src/cdp/domains/fetch.zig
+++ b/src/cdp/domains/fetch.zig
@@ -17,19 +17,17 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.

 const std = @import("std");
+const Allocator = std.mem.Allocator;

 const id = @import("../id.zig");
-const CDP = @import("../CDP.zig");
 const log = @import("../../log.zig");
+const network = @import("network.zig");

 const HttpClient = @import("../../browser/HttpClient.zig");
 const net_http = @import("../../network/http.zig");
 const Notification = @import("../../Notification.zig");

-const network = @import("network.zig");
-const Allocator = std.mem.Allocator;
-
-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        disable,
        enable,
@@ -137,13 +135,13 @@ const ErrorReason = enum {
    BlockedByResponse,
 };

-fn disable(cmd: *CDP.Command) !void {
+fn disable(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    bc.fetchDisable();
    return cmd.sendResult(null, .{});
 }

-fn enable(cmd: *CDP.Command) !void {
+fn enable(cmd: anytype) !void {
    const params = (try cmd.params(EnableParam)) orelse EnableParam{};
    if (!arePatternsSupported(params.patterns)) {
        log.warn(.not_implemented, "Fetch.enable", .{ .params = "pattern" });
@@ -182,7 +180,7 @@ fn arePatternsSupported(patterns: []RequestPattern) bool {
    return true;
 }

-pub fn requestIntercept(bc: *CDP.BrowserContext, intercept: *const Notification.RequestIntercept) !void {
+pub fn requestIntercept(bc: anytype, intercept: *const Notification.RequestIntercept) !void {
    // detachTarget could be called, in which case, we still have a page doing
    // things, but no session.
    const session_id = bc.session_id orelse return;
@@ -217,7 +215,7 @@ pub fn requestIntercept(bc: *CDP.BrowserContext, intercept: *const Notification.
    intercept.wait_for_interception.* = true;
 }

-fn continueRequest(cmd: *CDP.Command) !void {
+fn continueRequest(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    const params = (try cmd.params(struct {
        requestId: []const u8, // INT-{d}"
@@ -277,7 +275,7 @@ const AuthChallengeResponse = enum {
    ProvideCredentials,
 };

-fn continueWithAuth(cmd: *CDP.Command) !void {
+fn continueWithAuth(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    const params = (try cmd.params(struct {
        requestId: []const u8, // "INT-{d}"
@@ -320,7 +318,7 @@ fn continueWithAuth(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{});
 }

-fn fulfillRequest(cmd: *CDP.Command) !void {
+fn fulfillRequest(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;

    const params = (try cmd.params(struct {
@@ -362,7 +360,7 @@ fn fulfillRequest(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{});
 }

-fn failRequest(cmd: *CDP.Command) !void {
+fn failRequest(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    const params = (try cmd.params(struct {
        requestId: []const u8, // "INT-{d}"
@@ -384,7 +382,7 @@ fn failRequest(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{});
 }

-pub fn requestAuthRequired(bc: *CDP.BrowserContext, intercept: *const Notification.RequestAuthRequired) !void {
+pub fn requestAuthRequired(bc: anytype, intercept: *const Notification.RequestAuthRequired) !void {
    // detachTarget could be called, in which case, we still have a page doing
    // things, but no session.
    const session_id = bc.session_id orelse return;
--- a/src/cdp/domains/input.zig
+++ b/src/cdp/domains/input.zig
@@ -17,9 +17,8 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.

 const std = @import("std");
-const CDP = @import("../CDP.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        dispatchKeyEvent,
        dispatchMouseEvent,
@@ -34,7 +33,7 @@ pub fn processMessage(cmd: *CDP.Command) !void {
 }

 // https://chromedevtools.github.io/devtools-protocol/tot/Input/#method-dispatchKeyEvent
-fn dispatchKeyEvent(cmd: *CDP.Command) !void {
+fn dispatchKeyEvent(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        type: Type,
        key: []const u8 = "",
@@ -75,7 +74,7 @@ fn dispatchKeyEvent(cmd: *CDP.Command) !void {
 }

 // https://chromedevtools.github.io/devtools-protocol/tot/Input/#method-dispatchMouseEvent
-fn dispatchMouseEvent(cmd: *CDP.Command) !void {
+fn dispatchMouseEvent(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        x: f64,
        y: f64,
@@ -105,7 +104,7 @@ fn dispatchMouseEvent(cmd: *CDP.Command) !void {
 }

 // https://chromedevtools.github.io/devtools-protocol/tot/Input/#method-insertText
-fn insertText(cmd: *CDP.Command) !void {
+fn insertText(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        text: []const u8, // The text to insert
    })) orelse return error.InvalidParams;
--- a/src/cdp/domains/inspector.zig
+++ b/src/cdp/domains/inspector.zig
@@ -17,9 +17,8 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.

 const std = @import("std");
-const CDP = @import("../CDP.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
        disable,
--- a/src/cdp/domains/log.zig
+++ b/src/cdp/domains/log.zig
@@ -17,9 +17,8 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.

 const std = @import("std");
-const CDP = @import("../CDP.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
        disable,
--- a/src/cdp/domains/lp.zig
+++ b/src/cdp/domains/lp.zig
@@ -18,18 +18,14 @@

 const std = @import("std");
 const lp = @import("lightpanda");
-
-const CDP = @import("../CDP.zig");
-
-const Node = @import("../Node.zig");
-const DOMNode = @import("../../browser/webapi/Node.zig");
-
 const markdown = lp.markdown;
 const SemanticTree = lp.SemanticTree;
 const interactive = lp.interactive;
 const structured_data = lp.structured_data;
+const Node = @import("../Node.zig");
+const DOMNode = @import("../../browser/webapi/Node.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        getMarkdown,
        getSemanticTree,
--- a/src/cdp/domains/network.zig
+++ b/src/cdp/domains/network.zig
@@ -18,21 +18,18 @@

 const std = @import("std");
 const lp = @import("lightpanda");
-
+const Allocator = std.mem.Allocator;
 const log = @import("../../log.zig");

-const id = @import("../id.zig");
-const CDP = @import("../CDP.zig");
+const CdpStorage = @import("storage.zig");

+const id = @import("../id.zig");
 const URL = @import("../../browser/URL.zig");
 const Transfer = @import("../../browser/HttpClient.zig").Transfer;
 const Notification = @import("../../Notification.zig");
 const Mime = @import("../../browser/Mime.zig");

-const CdpStorage = @import("storage.zig");
-const Allocator = std.mem.Allocator;
-
-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
        disable,
@@ -62,19 +59,19 @@ pub fn processMessage(cmd: *CDP.Command) !void {
    }
 }

-fn enable(cmd: *CDP.Command) !void {
+fn enable(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    try bc.networkEnable();
    return cmd.sendResult(null, .{});
 }

-fn disable(cmd: *CDP.Command) !void {
+fn disable(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    bc.networkDisable();
    return cmd.sendResult(null, .{});
 }

-fn setExtraHTTPHeaders(cmd: *CDP.Command) !void {
+fn setExtraHTTPHeaders(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        headers: std.json.ArrayHashMap([]const u8),
    })) orelse return error.InvalidParams;
@@ -113,7 +110,7 @@ fn cookieMatches(cookie: *const Cookie, name: []const u8, domain: ?[]const u8, p
    return true;
 }

-fn deleteCookies(cmd: *CDP.Command) !void {
+fn deleteCookies(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        name: []const u8,
        url: ?[:0]const u8 = null,
@@ -147,14 +144,14 @@ fn deleteCookies(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{});
 }

-fn clearBrowserCookies(cmd: *CDP.Command) !void {
+fn clearBrowserCookies(cmd: anytype) !void {
    if (try cmd.params(struct {}) != null) return error.InvalidParams;
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    bc.session.cookie_jar.clearRetainingCapacity();
    return cmd.sendResult(null, .{});
 }

-fn setCookie(cmd: *CDP.Command) !void {
+fn setCookie(cmd: anytype) !void {
    const params = (try cmd.params(
        CdpStorage.CdpCookie,
    )) orelse return error.InvalidParams;
@@ -165,7 +162,7 @@ fn setCookie(cmd: *CDP.Command) !void {
    try cmd.sendResult(.{ .success = true }, .{});
 }

-fn setCookies(cmd: *CDP.Command) !void {
+fn setCookies(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        cookies: []const CdpStorage.CdpCookie,
    })) orelse return error.InvalidParams;
@@ -181,7 +178,7 @@ fn setCookies(cmd: *CDP.Command) !void {
 const GetCookiesParam = struct {
    urls: ?[]const [:0]const u8 = null,
 };
-fn getCookies(cmd: *CDP.Command) !void {
+fn getCookies(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    const params = (try cmd.params(GetCookiesParam)) orelse GetCookiesParam{};

@@ -204,7 +201,7 @@ fn getCookies(cmd: *CDP.Command) !void {
    try cmd.sendResult(.{ .cookies = writer }, .{});
 }

-fn getResponseBody(cmd: *CDP.Command) !void {
+fn getResponseBody(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        requestId: []const u8, // "REQ-{d}"
    })) orelse return error.InvalidParams;
@@ -230,7 +227,7 @@ fn getResponseBody(cmd: *CDP.Command) !void {
    }, .{});
 }

-pub fn httpRequestFail(bc: *CDP.BrowserContext, msg: *const Notification.RequestFail) !void {
+pub fn httpRequestFail(bc: anytype, msg: *const Notification.RequestFail) !void {
    // It's possible that the request failed because we aborted when the client
    // sent Target.closeTarget. In that case, bc.session_id will be cleared
    // already, and we can skip sending these messages to the client.
@@ -250,7 +247,7 @@ pub fn httpRequestFail(bc: *CDP.BrowserContext, msg: *const Notification.Request
    }, .{ .session_id = session_id });
 }

-pub fn httpRequestStart(bc: *CDP.BrowserContext, msg: *const Notification.RequestStart) !void {
+pub fn httpRequestStart(bc: anytype, msg: *const Notification.RequestStart) !void {
    // detachTarget could be called, in which case, we still have a page doing
    // things, but no session.
    const session_id = bc.session_id orelse return;
@@ -279,7 +276,7 @@ pub fn httpRequestStart(bc: *CDP.BrowserContext, msg: *const Notification.Reques
    }, .{ .session_id = session_id });
 }

-pub fn httpResponseHeaderDone(arena: Allocator, bc: *CDP.BrowserContext, msg: *const Notification.ResponseHeaderDone) !void {
+pub fn httpResponseHeaderDone(arena: Allocator, bc: anytype, msg: *const Notification.ResponseHeaderDone) !void {
    // detachTarget could be called, in which case, we still have a page doing
    // things, but no session.
    const session_id = bc.session_id orelse return;
@@ -296,7 +293,7 @@ pub fn httpResponseHeaderDone(arena: Allocator, bc: *CDP.BrowserContext, msg: *c
    }, .{ .session_id = session_id });
 }

-pub fn httpRequestDone(bc: *CDP.BrowserContext, msg: *const Notification.RequestDone) !void {
+pub fn httpRequestDone(bc: anytype, msg: *const Notification.RequestDone) !void {
    // detachTarget could be called, in which case, we still have a page doing
    // things, but no session.
    const session_id = bc.session_id orelse return;
--- a/src/cdp/domains/page.zig
+++ b/src/cdp/domains/page.zig
@@ -1,5 +1,4 @@
 // Copyright (C) 2023-2025  Lightpanda (Selecy SAS)
-
 //
 // Francis Bouvier <francis@lightpanda.io>
 // Pierre Tachoire <pierre@lightpanda.io>
@@ -23,8 +22,6 @@ const lp = @import("lightpanda");
 const screenshot_png = @embedFile("screenshot.png");

 const id = @import("../id.zig");
-const CDP = @import("../CDP.zig");
-
 const log = @import("../../log.zig");
 const js = @import("../../browser/js/js.zig");
 const URL = @import("../../browser/URL.zig");
@@ -34,7 +31,7 @@ const Notification = @import("../../Notification.zig");

 const Allocator = std.mem.Allocator;

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
        getFrameTree,
@@ -81,7 +78,7 @@ const Frame = struct {
    gatedAPIFeatures: [][]const u8 = &[0][]const u8{},
 };

-fn getFrameTree(cmd: *CDP.Command) !void {
+fn getFrameTree(cmd: anytype) !void {
    // Stagehand parses the response and error if we don't return a
    // correct one for this call when browser context or target id are missing.
    const startup = .{
@@ -111,7 +108,7 @@ fn getFrameTree(cmd: *CDP.Command) !void {
    }, .{});
 }

-fn setLifecycleEventsEnabled(cmd: *CDP.Command) !void {
+fn setLifecycleEventsEnabled(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        enabled: bool,
    })) orelse return error.InvalidParams;
@@ -152,7 +149,7 @@ fn setLifecycleEventsEnabled(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{});
 }

-fn addScriptToEvaluateOnNewDocument(cmd: *CDP.Command) !void {
+fn addScriptToEvaluateOnNewDocument(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        source: []const u8,
        worldName: ?[]const u8 = null,
@@ -182,7 +179,7 @@ fn addScriptToEvaluateOnNewDocument(cmd: *CDP.Command) !void {
    }, .{});
 }

-fn removeScriptToEvaluateOnNewDocument(cmd: *CDP.Command) !void {
+fn removeScriptToEvaluateOnNewDocument(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        identifier: []const u8,
    })) orelse return error.InvalidParams;
@@ -201,7 +198,7 @@ fn removeScriptToEvaluateOnNewDocument(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{});
 }

-fn close(cmd: *CDP.Command) !void {
+fn close(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;

    const target_id = bc.target_id orelse return error.TargetNotLoaded;
@@ -238,7 +235,7 @@ fn close(cmd: *CDP.Command) !void {
    bc.target_id = null;
 }

-fn createIsolatedWorld(cmd: *CDP.Command) !void {
+fn createIsolatedWorld(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        frameId: []const u8,
        worldName: []const u8,
@@ -258,7 +255,7 @@ fn createIsolatedWorld(cmd: *CDP.Command) !void {
    return cmd.sendResult(.{ .executionContextId = js_context.id }, .{});
 }

-fn navigate(cmd: *CDP.Command) !void {
+fn navigate(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        url: [:0]const u8,
        // referrer: ?[]const u8 = null,
@@ -292,7 +289,7 @@ fn navigate(cmd: *CDP.Command) !void {
    });
 }

-fn doReload(cmd: *CDP.Command) !void {
+fn doReload(cmd: anytype) !void {
    const params = try cmd.params(struct {
        ignoreCache: ?bool = null,
        scriptToEvaluateOnLoad: ?[]const u8 = null,
@@ -322,7 +319,7 @@ fn doReload(cmd: *CDP.Command) !void {
    });
 }

-pub fn pageNavigate(bc: *CDP.BrowserContext, event: *const Notification.PageNavigate) !void {
+pub fn pageNavigate(bc: anytype, event: *const Notification.PageNavigate) !void {
    // detachTarget could be called, in which case, we still have a page doing
    // things, but no session.
    const session_id = bc.session_id orelse return;
@@ -374,7 +371,7 @@ pub fn pageNavigate(bc: *CDP.BrowserContext, event: *const Notification.PageNavi
    }, .{ .session_id = session_id });
 }

-pub fn pageRemove(bc: *CDP.BrowserContext) !void {
+pub fn pageRemove(bc: anytype) !void {
    // Clear all remote object mappings to prevent stale objectIds from being used
    // after the context is destroy
    bc.inspector_session.inspector.resetContextGroup();
@@ -385,7 +382,7 @@ pub fn pageRemove(bc: *CDP.BrowserContext) !void {
    }
 }

-pub fn pageCreated(bc: *CDP.BrowserContext, page: *Page) !void {
+pub fn pageCreated(bc: anytype, page: *Page) !void {
    _ = bc.cdp.page_arena.reset(.{ .retain_with_limit = 1024 * 512 });

    for (bc.isolated_worlds.items) |isolated_world| {
@@ -397,7 +394,7 @@ pub fn pageCreated(bc: *CDP.BrowserContext, page: *Page) !void {
    bc.captured_responses = .empty;
 }

-pub fn pageFrameCreated(bc: *CDP.BrowserContext, event: *const Notification.PageFrameCreated) !void {
+pub fn pageFrameCreated(bc: anytype, event: *const Notification.PageFrameCreated) !void {
    const session_id = bc.session_id orelse return;

    const cdp = bc.cdp;
@@ -418,7 +415,7 @@ pub fn pageFrameCreated(bc: *CDP.BrowserContext, event: *const Notification.Page
    }
 }

-pub fn pageNavigated(arena: Allocator, bc: *CDP.BrowserContext, event: *const Notification.PageNavigated) !void {
+pub fn pageNavigated(arena: Allocator, bc: anytype, event: *const Notification.PageNavigated) !void {
    // detachTarget could be called, in which case, we still have a page doing
    // things, but no session.
    const session_id = bc.session_id orelse return;
@@ -621,15 +618,15 @@ pub fn pageLoaded(bc: anytype, event: *const Notification.PageLoaded) !void {
    }, .{ .session_id = session_id });
 }

-pub fn pageNetworkIdle(bc: *CDP.BrowserContext, event: *const Notification.PageNetworkIdle) !void {
+pub fn pageNetworkIdle(bc: anytype, event: *const Notification.PageNetworkIdle) !void {
    return sendPageLifecycle(bc, "networkIdle", event.timestamp, &id.toFrameId(event.frame_id), &id.toLoaderId(event.req_id));
 }

-pub fn pageNetworkAlmostIdle(bc: *CDP.BrowserContext, event: *const Notification.PageNetworkAlmostIdle) !void {
+pub fn pageNetworkAlmostIdle(bc: anytype, event: *const Notification.PageNetworkAlmostIdle) !void {
    return sendPageLifecycle(bc, "networkAlmostIdle", event.timestamp, &id.toFrameId(event.frame_id), &id.toLoaderId(event.req_id));
 }

-fn sendPageLifecycle(bc: *CDP.BrowserContext, name: []const u8, timestamp: u64, frame_id: []const u8, loader_id: []const u8) !void {
+fn sendPageLifecycle(bc: anytype, name: []const u8, timestamp: u64, frame_id: []const u8, loader_id: []const u8) !void {
    // detachTarget could be called, in which case, we still have a page doing
    // things, but no session.
    const session_id = bc.session_id orelse return;
@@ -664,7 +661,7 @@ fn base64Encode(comptime input: []const u8) [std.base64.standard.Encoder.calcSiz
    return buf;
 }

-fn captureScreenshot(cmd: *CDP.Command) !void {
+fn captureScreenshot(cmd: anytype) !void {
    const Params = struct {
        format: ?[]const u8 = "png",
        quality: ?u8 = null,
@@ -700,7 +697,7 @@ fn captureScreenshot(cmd: *CDP.Command) !void {
    }, .{});
 }

-fn getLayoutMetrics(cmd: *CDP.Command) !void {
+fn getLayoutMetrics(cmd: anytype) !void {
    const width = 1920;
    const height = 1080;

--- a/src/cdp/domains/performance.zig
+++ b/src/cdp/domains/performance.zig
@@ -17,9 +17,8 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.

 const std = @import("std");
-const CDP = @import("../CDP.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
        disable,
--- a/src/cdp/domains/runtime.zig
+++ b/src/cdp/domains/runtime.zig
@@ -19,9 +19,7 @@
 const std = @import("std");
 const builtin = @import("builtin");

-const CDP = @import("../CDP.zig");
-
-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
        runIfWaitingForDebugger,
@@ -38,7 +36,7 @@ pub fn processMessage(cmd: *CDP.Command) !void {
    }
 }

-fn sendInspector(cmd: *CDP.Command, action: anytype) !void {
+fn sendInspector(cmd: anytype, action: anytype) !void {
    // save script in file at debug mode
    if (builtin.mode == .Debug) {
        try logInspector(cmd, action);
@@ -50,7 +48,7 @@ fn sendInspector(cmd: *CDP.Command, action: anytype) !void {
    bc.callInspector(cmd.input.json);
 }

-fn logInspector(cmd: *CDP.Command, action: anytype) !void {
+fn logInspector(cmd: anytype, action: anytype) !void {
    const script = switch (action) {
        .evaluate => blk: {
            const params = (try cmd.params(struct {
--- a/src/cdp/domains/security.zig
+++ b/src/cdp/domains/security.zig
@@ -17,9 +17,8 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.

 const std = @import("std");
-const CDP = @import("../CDP.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        enable,
        disable,
@@ -33,7 +32,7 @@ pub fn processMessage(cmd: *CDP.Command) !void {
    }
 }

-fn setIgnoreCertificateErrors(cmd: *CDP.Command) !void {
+fn setIgnoreCertificateErrors(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        ignore: bool,
    })) orelse return error.InvalidParams;
--- a/src/cdp/domains/storage.zig
+++ b/src/cdp/domains/storage.zig
@@ -18,16 +18,13 @@

 const std = @import("std");

-const CDP = @import("../CDP.zig");
-
 const log = @import("../../log.zig");
 const URL = @import("../../browser/URL.zig");
 const Cookie = @import("../../browser/webapi/storage/storage.zig").Cookie;
-
 const CookieJar = Cookie.Jar;
 pub const PreparedUri = Cookie.PreparedUri;

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        clearCookies,
        setCookies,
@@ -43,7 +40,7 @@ pub fn processMessage(cmd: *CDP.Command) !void {

 const BrowserContextParam = struct { browserContextId: ?[]const u8 = null };

-fn clearCookies(cmd: *CDP.Command) !void {
+fn clearCookies(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    const params = (try cmd.params(BrowserContextParam)) orelse BrowserContextParam{};

@@ -58,7 +55,7 @@ fn clearCookies(cmd: *CDP.Command) !void {
    return cmd.sendResult(null, .{});
 }

-fn getCookies(cmd: *CDP.Command) !void {
+fn getCookies(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    const params = (try cmd.params(BrowserContextParam)) orelse BrowserContextParam{};

@@ -72,7 +69,7 @@ fn getCookies(cmd: *CDP.Command) !void {
    try cmd.sendResult(.{ .cookies = writer }, .{});
 }

-fn setCookies(cmd: *CDP.Command) !void {
+fn setCookies(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
    const params = (try cmd.params(struct {
        cookies: []const CdpCookie,
--- a/src/cdp/domains/target.zig
+++ b/src/cdp/domains/target.zig
@@ -20,13 +20,11 @@ const std = @import("std");
 const lp = @import("lightpanda");

 const id = @import("../id.zig");
-const CDP = @import("../CDP.zig");
-
 const log = @import("../../log.zig");
 const URL = @import("../../browser/URL.zig");
 const js = @import("../../browser/js/js.zig");

-pub fn processMessage(cmd: *CDP.Command) !void {
+pub fn processMessage(cmd: anytype) !void {
    const action = std.meta.stringToEnum(enum {
        getTargets,
        attachToTarget,
@@ -62,7 +60,7 @@ pub fn processMessage(cmd: *CDP.Command) !void {
    }
 }

-fn getTargets(cmd: *CDP.Command) !void {
+fn getTargets(cmd: anytype) !void {
    // If no context available, return an empty array.
    const bc = cmd.browser_context orelse {
        return cmd.sendResult(.{
@@ -88,7 +86,7 @@ fn getTargets(cmd: *CDP.Command) !void {
    }, .{ .include_session_id = false });
 }

-fn getBrowserContexts(cmd: *CDP.Command) !void {
+fn getBrowserContexts(cmd: anytype) !void {
    var browser_context_ids: []const []const u8 = undefined;
    if (cmd.browser_context) |bc| {
        browser_context_ids = &.{bc.id};
@@ -101,7 +99,7 @@ fn getBrowserContexts(cmd: *CDP.Command) !void {
    }, .{ .include_session_id = false });
 }

-fn createBrowserContext(cmd: *CDP.Command) !void {
+fn createBrowserContext(cmd: anytype) !void {
    const params = try cmd.params(struct {
        disposeOnDetach: bool = false,
        proxyServer: ?[:0]const u8 = null,
@@ -132,7 +130,7 @@ fn createBrowserContext(cmd: *CDP.Command) !void {
    }, .{});
 }

-fn disposeBrowserContext(cmd: *CDP.Command) !void {
+fn disposeBrowserContext(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        browserContextId: []const u8,
    })) orelse return error.InvalidParams;
@@ -143,7 +141,7 @@ fn disposeBrowserContext(cmd: *CDP.Command) !void {
    try cmd.sendResult(null, .{});
 }

-fn createTarget(cmd: *CDP.Command) !void {
+fn createTarget(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        url: [:0]const u8 = "about:blank",
        // width: ?u64 = null,
@@ -232,7 +230,7 @@ fn createTarget(cmd: *CDP.Command) !void {
    }, .{});
 }

-fn attachToTarget(cmd: *CDP.Command) !void {
+fn attachToTarget(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        targetId: []const u8,
        flatten: bool = true,
@@ -249,7 +247,7 @@ fn attachToTarget(cmd: *CDP.Command) !void {
    return cmd.sendResult(.{ .sessionId = bc.session_id }, .{});
 }

-fn attachToBrowserTarget(cmd: *CDP.Command) !void {
+fn attachToBrowserTarget(cmd: anytype) !void {
    const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;

    const session_id = bc.session_id orelse cmd.cdp.session_id_gen.next();
@@ -271,7 +269,7 @@ fn attachToBrowserTarget(cmd: *CDP.Command) !void {
    return cmd.sendResult(.{ .sessionId = bc.session_id }, .{});
 }

-fn closeTarget(cmd: *CDP.Command) !void {
+fn closeTarget(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        targetId: []const u8,
    })) orelse return error.InvalidParams;
@@ -312,7 +310,7 @@ fn closeTarget(cmd: *CDP.Command) !void {
    bc.target_id = null;
 }

-fn getTargetInfo(cmd: *CDP.Command) !void {
+fn getTargetInfo(cmd: anytype) !void {
    const Params = struct {
        targetId: ?[]const u8 = null,
    };
@@ -349,7 +347,7 @@ fn getTargetInfo(cmd: *CDP.Command) !void {
    }, .{ .include_session_id = false });
 }

-fn sendMessageToTarget(cmd: *CDP.Command) !void {
+fn sendMessageToTarget(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        message: []const u8,
        sessionId: []const u8,
@@ -367,19 +365,32 @@ fn sendMessageToTarget(cmd: *CDP.Command) !void {
        return error.UnknownSessionId;
    }

-    var aw = std.Io.Writer.Allocating.init(cmd.arena);
-    cmd.cdp.dispatch(cmd.arena, .{ .capture = &aw.writer }, params.message) catch |err| {
+    const Capture = struct {
+        aw: std.Io.Writer.Allocating,
+
+        pub fn sendJSON(self: *@This(), message: anytype) !void {
+            return std.json.Stringify.value(message, .{
+                .emit_null_optional_fields = false,
+            }, &self.aw.writer);
+        }
+    };
+
+    var capture = Capture{
+        .aw = .init(cmd.arena),
+    };
+
+    cmd.cdp.dispatch(cmd.arena, &capture, params.message) catch |err| {
        log.err(.cdp, "internal dispatch error", .{ .err = err, .id = cmd.input.id, .message = params.message });
        return err;
    };

    try cmd.sendEvent("Target.receivedMessageFromTarget", .{
-        .message = aw.written(),
+        .message = capture.aw.written(),
        .sessionId = params.sessionId,
    }, .{});
 }

-fn detachFromTarget(cmd: *CDP.Command) !void {
+fn detachFromTarget(cmd: anytype) !void {
    if (cmd.browser_context) |bc| {
        if (bc.session_id) |session_id| {
            try cmd.sendEvent("Target.detachedFromTarget", .{
@@ -393,11 +404,11 @@ fn detachFromTarget(cmd: *CDP.Command) !void {
 }

 // TODO: noop method
-fn setDiscoverTargets(cmd: *CDP.Command) !void {
+fn setDiscoverTargets(cmd: anytype) !void {
    return cmd.sendResult(null, .{});
 }

-fn setAutoAttach(cmd: *CDP.Command) !void {
+fn setAutoAttach(cmd: anytype) !void {
    const params = (try cmd.params(struct {
        autoAttach: bool,
        waitForDebuggerOnStart: bool,
@@ -457,7 +468,7 @@ fn setAutoAttach(cmd: *CDP.Command) !void {
    try cmd.sendResult(null, .{});
 }

-fn doAttachtoTarget(cmd: *CDP.Command, target_id: []const u8) !void {
+fn doAttachtoTarget(cmd: anytype, target_id: []const u8) !void {
    const bc = cmd.browser_context.?;
    const session_id = bc.session_id orelse cmd.cdp.session_id_gen.next();

--- a/src/cdp/testing.zig
+++ b/src/cdp/testing.zig
@@ -64,7 +64,7 @@ const TestContext = struct {
        session_id: ?[]const u8 = null,
        url: ?[:0]const u8 = null,
    };
-    pub fn loadBrowserContext(self: *TestContext, opts: BrowserContextOpts) !*CDP.BrowserContext {
+    pub fn loadBrowserContext(self: *TestContext, opts: BrowserContextOpts) !*CDP.BrowserContext(CDP) {
        var c = self.cdp();
        if (c.browser_context) |bc| {
            _ = c.disposeBrowserContext(bc.id);
--- a/src/lightpanda.zig
+++ b/src/lightpanda.zig
@@ -237,6 +237,10 @@ pub fn RC(comptime T: type) type {
                session.releaseArena(kv.value.arena);
            }
        }
+
+        pub fn format(self: @This(), writer: *std.Io.Writer) !void {
+            return writer.print("{d}", .{self._refs});
+        }
    };
 }