Merge pull request #3571 from lightpanda-io/nikneym/playwright-id-track

`cdp`: answer inspector commands on the session that sent them

src/browser/js/Inspector.zig

@@ -17,7 +17,6 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
-const lp = @import("lightpanda");
 const js = @import("js.zig");
 const v8 = js.v8;
 
@@ -42,7 +41,6 @@ isolate: *v8.Isolate,
 handle: *v8.Inspector,
 client: *v8.InspectorClientImpl,
 default_context: ?v8.Global,
-session: ?Session,
 
 pub fn init(allocator: Allocator, isolate: *v8.Isolate) !*Inspector {
     const self = try allocator.create(Inspector);
@@ -50,7 +48,6 @@ pub fn init(allocator: Allocator, isolate: *v8.Isolate) !*Inspector {
 
     self.* = .{
         .unique_id = 1,
-        .session = null,
         .isolate = isolate,
         .client = undefined,
         .handle = undefined,
@@ -72,29 +69,11 @@ pub fn deinit(self: *const Inspector, allocator: Allocator) void {
     v8.v8__HandleScope__CONSTRUCT(&hs, self.isolate);
     defer v8.v8__HandleScope__DESTRUCT(&hs);
 
-    if (self.session) |*s| {
-        s.deinit();
-    }
     v8.v8_inspector__Client__IMPL__DELETE(self.client);
     v8.v8_inspector__Inspector__DELETE(self.handle);
     allocator.destroy(self);
 }
 
-pub fn startSession(self: *Inspector, ctx: anytype) *Session {
-    if (comptime lp.IS_DEBUG) {
-        std.debug.assert(self.session == null);
-    }
-
-    self.session = @as(Session, undefined);
-    Session.init(&self.session.?, self, ctx);
-    return &self.session.?;
-}
-
-pub fn stopSession(self: *Inspector) void {
-    self.session.?.deinit();
-    self.session = null;
-}
-
 // From CDP docs
 // https://chromedevtools.github.io/devtools-protocol/tot/Runtime/#type-ExecutionContextDescription
 // ----
@@ -199,7 +178,10 @@ const RemoteObject = struct {
 // Combines a v8::InspectorSession and a v8::InspectorChannelImpl. The
 // InspectorSession is for zig -> v8 (sending messages to the inspector). The
 // Channel is for v8 -> zig, getting events from the Inspector (that we'll pass
-// back to some opaque context, i.e the CDP BrowserContext).
+// back to some opaque context, i.e the CDP AttachedSession).
+// The channel keeps the Session's address, so the owner must not move it
+// between init and deinit. Every Session connects to the same
+// CONTEXT_GROUP_ID and so sees every context.
 // The channel callbacks are defined below, as:
 //   pub export fn v8_inspector__Channel__IMPL__XYZ
 pub const Session = struct {
@@ -212,7 +194,7 @@ pub const Session = struct {
     onNotif: *const fn (ctx: *anyopaque, msg: []const u8) void,
     onResp: *const fn (ctx: *anyopaque, call_id: u32, msg: []const u8) void,
 
-    fn init(self: *Session, inspector: *Inspector, ctx: anytype) void {
+    pub fn init(self: *Session, inspector: *Inspector, ctx: anytype) void {
         const Container = @typeInfo(@TypeOf(ctx)).pointer.child;
 
         const channel = v8.v8_inspector__Channel__IMPL__CREATE(inspector.isolate);
@@ -234,11 +216,23 @@ pub const Session = struct {
         };
     }
 
-    fn deinit(self: *const Session) void {
+    pub fn deinit(self: *Session) void {
+        // Deleting the V8 session fails its pending evaluations, which V8
+        // answers through the channel. The client is gone: drop them.
+        self.onResp = dropResponse;
+        self.onNotif = dropNotification;
+
+        var hs: v8.HandleScope = undefined;
+        v8.v8__HandleScope__CONSTRUCT(&hs, self.inspector.isolate);
+        defer v8.v8__HandleScope__DESTRUCT(&hs);
+
         v8.v8_inspector__Session__DELETE(self.handle);
         v8.v8_inspector__Channel__IMPL__DELETE(self.channel);
     }
 
+    fn dropResponse(_: *anyopaque, _: u32, _: []const u8) void {}
+    fn dropNotification(_: *anyopaque, _: []const u8) void {}
+
     pub fn send(self: *const Session, msg: []const u8) void {
         const isolate = self.inspector.isolate;
         var hs: v8.HandleScope = undefined;

src/server/cdp/CDP.zig

@@ -333,18 +333,8 @@ pub fn resolveSessionId(self: *const CDP, input_session_id: []const u8) ?[]const
             return browser_session_id;
         }
     }
-    const browser_context = &(self.browser_context orelse return null);
-    if (browser_context.session_id) |session_id| {
-        if (std.mem.eql(u8, session_id, input_session_id)) {
-            return session_id;
-        }
-    }
-    for (browser_context.attached_sessions.items) |session| {
-        if (std.mem.eql(u8, session.id, input_session_id)) {
-            return session.id;
-        }
-    }
-    return null;
+    const browser_context = if (self.browser_context) |*bc| bc else return null;
+    return browser_context.attached_sessions.getKey(input_session_id);
 }
 
 fn isValidSessionId(self: *const CDP, input_session_id: []const u8) bool {
@@ -407,9 +397,41 @@ pub const BrowserContext = struct {
         id: u32,
     };
 
-    const AttachedSession = struct {
+    // A CDP session attached to this context's page target. Each owns a V8
+    // inspector session; V8 keeps `Runtime.enable` state and remote object ids
+    // per session, so a command is answered on the session it was sent
+    // through and a session only gets the inspector events it enabled.
+    pub const AttachedSession = struct {
         id: []const u8,
         parent_id: ?[]const u8,
+        bc: *BrowserContext,
+        inspector_session: js.Inspector.Session,
+
+        /// V8 -> this session. Stamp OUR id on responses and events.
+        pub fn onInspectorResponse(ctx: *anyopaque, _: u32, msg: []const u8) void {
+            const self: *AttachedSession = @ptrCast(@alignCast(ctx));
+            self.bc.sendInspectorMessage(msg, self.id) catch |err| {
+                log.err(.cdp, "send inspector response", .{ .err = err });
+            };
+        }
+
+        pub fn onInspectorEvent(ctx: *anyopaque, msg: []const u8) void {
+            const self: *AttachedSession = @ptrCast(@alignCast(ctx));
+            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, .session_id = self.id });
+            }
+
+            self.bc.sendInspectorMessage(msg, self.id) catch |err| {
+                log.err(.cdp, "send inspector event", .{ .err = err });
+            };
+        }
     };
     id: []const u8,
     cdp: *CDP,
@@ -444,16 +466,18 @@ pub const BrowserContext = struct {
     // it). null until the first page is created.
     page_handle: ?Session.PageHandle = null,
 
-    // 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.
+    // The primary CDP session's 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. Also included in
+    // `attached_sessions`.
     session_id: ?[]const u8,
-    attached_sessions: std.ArrayList(AttachedSession) = .empty,
+
+    // Every session attached to the page target, the primary included, by
+    // session id. Insertion-ordered so detach events come out in attach order.
+    //
+    // Request with a session id that isn't there is rejected.
+    attached_sessions: std.StringArrayHashMapUnmanaged(*AttachedSession) = .empty,
 
     // A cancelled text-less keyDown drops the char message that follows it
     // (chromedp's keyDown/char/keyUp split), as Chrome does.
@@ -470,7 +494,6 @@ pub const BrowserContext = struct {
     // entries evicted by resetFrame can linger harmlessly until reset.
     set_child_nodes_sent: std.AutoHashMapUnmanaged(NodeRegistry.Id, void) = .empty,
 
-    inspector_session: *js.Inspector.Session,
     isolated_worlds: std.ArrayList(*IsolatedWorld),
 
     // True when Runtime.evaluate has been run in the main world. Optimization
@@ -533,10 +556,6 @@ pub const BrowserContext = struct {
             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 = NodeRegistry.init(allocator);
         errdefer registry.deinit();
 
@@ -552,7 +571,6 @@ pub const BrowserContext = struct {
             .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(),
@@ -585,7 +603,7 @@ pub const BrowserContext = struct {
         // It appends async tasks, so we make sure we run the message loop
         // before deinit it.
         env.inspector.?.resetContextGroup();
-        env.inspector.?.stopSession();
+        self.detachAllSessions();
 
         // abort all intercepted requests before closing the session/page
         // since some of these might callback into the page/scriptmanager.
@@ -622,6 +640,7 @@ pub const BrowserContext = struct {
         self.node_registry.deinit();
         self.node_search_list.deinit();
         self.set_child_nodes_sent.deinit(self.cdp.allocator);
+        self.attached_sessions.deinit(self.cdp.allocator);
 
         // Session.deinit (called via closeSession above) already cleared this
         // notification off any ownerless CorsGate/RobotsGate transfers.
@@ -842,7 +861,7 @@ pub const BrowserContext = struct {
     pub fn closeTarget(self: *BrowserContext) !void {
         const target_id = self.target_id orelse return;
         const cdp = self.cdp;
-        for (self.attached_sessions.items) |session| {
+        for (self.attached_sessions.values()) |session| {
             self.fetchDisableForSession(session.id);
             try cdp.sendEvent("Inspector.detached", .{
                 .reason = "Render process gone.",
@@ -853,21 +872,7 @@ pub const BrowserContext = struct {
                 .reason = "Render process gone.",
             }, .{ .session_id = session.parent_id });
         }
-        self.attached_sessions.clearRetainingCapacity();
-
-        // could be null, created but never attached
-        if (self.session_id) |session_id| {
-            self.fetchDisableForSession(session_id);
-            try cdp.sendEvent("Inspector.detached", .{
-                .reason = "Render process gone.",
-            }, .{ .session_id = session_id });
-            try cdp.sendEvent("Target.detachedFromTarget", .{
-                .targetId = target_id,
-                .sessionId = session_id,
-                .reason = "Render process gone.",
-            }, .{});
-            self.session_id = null;
-        }
+        self.detachAllSessions();
 
         try cdp.sendEvent("Target.targetDestroyed", .{ .targetId = target_id }, .{});
 
@@ -1174,44 +1179,85 @@ pub const BrowserContext = struct {
         }
     }
 
-    pub fn callInspector(self: *const BrowserContext, msg: []const u8) void {
-        self.inspector_session.send(msg);
+    pub inline fn inspector(self: *const BrowserContext) *js.Inspector {
+        return self.cdp.browser.env.inspector.?;
+    }
+
+    /// Attaches `session_id` to the page target with its own inspector
+    /// session. The id is copied into the context's arena.
+    pub fn attachSession(self: *BrowserContext, session_id: []const u8, parent_id: ?[]const u8) !*AttachedSession {
+        if (self.attached_sessions.contains(session_id)) {
+            return error.SessionAlreadyAttached;
+        }
+        const allocator = self.cdp.allocator;
+
+        const attached = try allocator.create(AttachedSession);
+        errdefer allocator.destroy(attached);
+
+        attached.* = .{
+            .id = try self.arena.dupe(u8, session_id),
+            .parent_id = parent_id,
+            .bc = self,
+            .inspector_session = undefined,
+        };
+        attached.inspector_session.init(self.inspector(), attached);
+        errdefer attached.inspector_session.deinit();
+
+        try self.attached_sessions.put(allocator, attached.id, attached);
+        return attached;
+    }
+
+    /// The first session attached to the target.
+    pub fn attachPrimarySession(self: *BrowserContext, session_id: []const u8) !*AttachedSession {
+        lp.assert(self.session_id == null, "CDP.BrowserContext.attachPrimarySession already attached", .{});
+        const attached = try self.attachSession(session_id, null);
+        self.session_id = attached.id;
+        return attached;
+    }
+
+    /// Stops the session's inspector session and forgets it.
+    /// Returns false when no such session is attached.
+    pub fn detachSession(self: *BrowserContext, session_id: []const u8) bool {
+        const kv = self.attached_sessions.fetchOrderedRemove(session_id) orelse return false;
+        if (self.session_id) |primary| {
+            if (std.mem.eql(u8, primary, session_id)) {
+                self.session_id = null;
+            }
+        }
+        self.destroySession(kv.value);
+        return true;
+    }
+
+    pub fn detachAllSessions(self: *BrowserContext) void {
+        for (self.attached_sessions.values()) |attached| {
+            self.destroySession(attached);
+        }
+        self.attached_sessions.clearRetainingCapacity();
+        self.session_id = null;
+    }
+
+    fn destroySession(self: *BrowserContext, attached: *AttachedSession) void {
+        attached.inspector_session.deinit();
+        self.cdp.allocator.destroy(attached);
+    }
+
+    pub fn inspectorSession(self: *const BrowserContext, session_id: ?[]const u8) !*js.Inspector.Session {
+        const id = session_id orelse self.session_id orelse return error.SessionNotAttached;
+        const attached = self.attached_sessions.get(id) orelse return error.SessionNotAttached;
+        return &attached.inspector_session;
+    }
+
+    /// Forwards `cmd`'s raw JSON to the inspector session of the session it was sent through.
+    pub fn callInspector(self: *BrowserContext, cmd: *const Command) !void {
+        const inspector_session = try self.inspectorSession(cmd.input.session_id);
+        inspector_session.send(cmd.input.json);
         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
+    // This is hacky x 2. First, we create the JSON payload by gluing the
     // 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;
-        };
-
+    fn sendInspectorMessage(self: *BrowserContext, msg: []const u8, session_id: []const u8) !void {
         const cdp = self.cdp;
         const allocator = cdp.link.acquireSendArena();
         defer cdp.link.releaseSendArena();

src/server/cdp/domains/accessibility.zig

@@ -89,7 +89,7 @@ fn queryAXTree(cmd: *CDP.Command) !void {
     const params = (try cmd.params(Params)) orelse return error.InvalidParams;
 
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
-    const node = try dom.getNode(cmd.arena, bc, params.nodeId, params.backendNodeId, params.objectId);
+    const node = try dom.getNode(cmd.arena, bc, cmd.input.session_id, params.nodeId, params.backendNodeId, params.objectId);
 
     const frame = bc.mainFrame() orelse return error.FrameNotLoaded;
     const temp_arena = try frame.getArena(.medium, "AXNode");
@@ -124,7 +124,7 @@ fn getPartialAXTree(cmd: *CDP.Command) !void {
     }
 
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
-    const node = try dom.getNode(cmd.arena, bc, params.nodeId, params.backendNodeId, params.objectId);
+    const node = try dom.getNode(cmd.arena, bc, cmd.input.session_id, params.nodeId, params.backendNodeId, params.objectId);
 
     const frame = bc.mainFrame() orelse return error.FrameNotLoaded;
     const temp_arena = try frame.getArena(.medium, "AXNode");

src/server/cdp/domains/dom.zig

@@ -365,9 +365,12 @@ fn resolveNode(cmd: *CDP.Command) !void {
     js_context.localScope(&ls);
     defer ls.deinit();
 
+    // The object id is minted on the command's session; only that session can unwrap it later.
+    const inspector_session = try bc.inspectorSession(cmd.input.session_id);
+
     // node._node is a *DOMNode we need this to be able to find its most derived type e.g. Node -> Element -> HTMLElement
     // So we use the Node.Union when retrieve the value from the environment
-    const remote_object = try bc.inspector_session.getRemoteObject(
+    const remote_object = try inspector_session.getRemoteObject(
         &ls.local,
         params.objectGroup orelse "",
         node.dom,
@@ -433,7 +436,7 @@ fn describeNode(cmd: *CDP.Command) !void {
     }
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
 
-    const node = try getNode(cmd.arena, bc, params.nodeId, params.backendNodeId, params.objectId);
+    const node = try getNode(cmd.arena, bc, cmd.input.session_id, params.nodeId, params.backendNodeId, params.objectId);
 
     return cmd.sendResult(.{ .node = bc.nodeWriter(node, .{ .depth = params.depth }) }, .{});
 }
@@ -477,7 +480,7 @@ fn scrollIntoViewIfNeeded(cmd: *CDP.Command) !void {
 
     // We retrieve the node to at least check if it exists and is valid.
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
-    const node = try getNode(cmd.arena, bc, params.nodeId, params.backendNodeId, params.objectId);
+    const node = try getNode(cmd.arena, bc, cmd.input.session_id, params.nodeId, params.backendNodeId, params.objectId);
 
     switch (node.dom._type) {
         .element => {},
@@ -489,7 +492,9 @@ fn scrollIntoViewIfNeeded(cmd: *CDP.Command) !void {
     return cmd.sendResult(null, .{});
 }
 
-pub fn getNode(arena: Allocator, bc: *CDP.BrowserContext, node_id: ?NodeRegistry.Id, backend_node_id: ?NodeRegistry.Id, object_id: ?[]const u8) !*NodeRegistry.Node {
+/// `session_id` belongs to the command; a remote object id only resolves on
+/// the inspector session that minted it.
+pub fn getNode(arena: Allocator, bc: *CDP.BrowserContext, session_id: ?[]const u8, node_id: ?NodeRegistry.Id, backend_node_id: ?NodeRegistry.Id, object_id: ?[]const u8) !*NodeRegistry.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;
@@ -501,7 +506,8 @@ pub fn getNode(arena: Allocator, bc: *CDP.BrowserContext, node_id: ?NodeRegistry
         defer ls.deinit();
 
         // Retrieve the object from which ever context it is in.
-        const parser_node = try bc.inspector_session.getNodePtr(arena, object_id_, &ls.local);
+        const inspector_session = try bc.inspectorSession(session_id);
+        const parser_node = try inspector_session.getNodePtr(arena, object_id_, &ls.local);
         return try bc.node_registry.register(@ptrCast(@alignCast(parser_node)));
     }
     return error.MissingParams;
@@ -519,7 +525,7 @@ fn getContentQuads(cmd: *CDP.Command) !void {
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
     const frame = bc.mainFrame() orelse return error.FrameNotLoaded;
 
-    const node = try getNode(cmd.arena, bc, params.nodeId, params.backendNodeId, params.objectId);
+    const node = try getNode(cmd.arena, bc, cmd.input.session_id, params.nodeId, params.backendNodeId, params.objectId);
 
     // TODO likely if the following CSS properties are set the quads should be empty
     // visibility: hidden
@@ -545,7 +551,7 @@ fn getBoxModel(cmd: *CDP.Command) !void {
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
     const frame = bc.mainFrame() orelse return error.FrameNotLoaded;
 
-    const node = try getNode(cmd.arena, bc, params.nodeId, params.backendNodeId, params.objectId);
+    const node = try getNode(cmd.arena, bc, cmd.input.session_id, params.nodeId, params.backendNodeId, params.objectId);
 
     // TODO implement for document or text
     const element = node.dom.is(DOMNode.Element) orelse return error.NodeIsNotAnElement;
@@ -626,7 +632,7 @@ fn getOuterHTML(cmd: *CDP.Command) !void {
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
     const frame = bc.mainFrame() orelse return error.FrameNotLoaded;
 
-    const node = try getNode(cmd.arena, bc, params.nodeId, params.backendNodeId, params.objectId);
+    const node = try getNode(cmd.arena, bc, cmd.input.session_id, params.nodeId, params.backendNodeId, params.objectId);
 
     var aw = std.Io.Writer.Allocating.init(cmd.arena);
     try dump.deep(node.dom, .{}, &aw.writer, frame);
@@ -640,7 +646,7 @@ fn requestNode(cmd: *CDP.Command) !void {
     })) orelse return error.InvalidParams;
 
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
-    const node = try getNode(cmd.arena, bc, null, null, params.objectId);
+    const node = try getNode(cmd.arena, bc, cmd.input.session_id, null, null, params.objectId);
 
     return cmd.sendResult(.{ .nodeId = node.id }, .{});
 }
@@ -661,7 +667,7 @@ fn setFileInputFiles(cmd: *CDP.Command) !void {
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
     const root = bc.mainFrame() orelse return error.FrameNotLoaded;
 
-    const node = try getNode(cmd.arena, bc, params.nodeId, params.backendNodeId, params.objectId);
+    const node = try getNode(cmd.arena, bc, cmd.input.session_id, params.nodeId, params.backendNodeId, params.objectId);
     const element = node.dom.is(DOMNode.Element) orelse return error.NodeIsNotAnElement;
     const input = element.is(Input) orelse return error.NotAnInputElement;
     if (input._input_type != .file) return error.NotAFileInput;
@@ -694,7 +700,7 @@ fn focus(cmd: *CDP.Command) !void {
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
     const frame = bc.mainFrame() orelse return error.FrameNotLoaded;
 
-    const node = try getNode(cmd.arena, bc, params.nodeId, params.backendNodeId, params.objectId);
+    const node = try getNode(cmd.arena, bc, cmd.input.session_id, params.nodeId, params.backendNodeId, params.objectId);
     const element = node.dom.is(DOMNode.Element) orelse return error.NodeIsNotAnElement;
     if (element.isFocusable(frame) == false) {
         return cmd.sendError(-32000, "Element is not focusable", .{});
@@ -1400,7 +1406,49 @@ fn mainWorldContextId(bc: *CDP.BrowserContext, frame: *const Frame) !i32 {
     var ls: js.Local.Scope = undefined;
     frame.js.localScope(&ls);
     defer ls.deinit();
-    return bc.inspector_session.inspector.getContextId(&ls.local);
+    return bc.inspector().getContextId(&ls.local);
+}
+
+test "cdp.dom: remote object ids belong to the session that minted them" {
+    var ctx = try testing.context();
+    defer ctx.deinit();
+
+    const bc = try ctx.loadBrowserContext(.{ .id = "BID-RO", .url = "cdp/dom1.html", .target_id = "FID-000000000R".*, .session_id = "SID-PRIMARY" });
+    _ = try bc.attachSession("SID-AUX", null);
+
+    const root = bc.mainFrame() orelse unreachable;
+    const html = root.document.getDocumentElement() orelse unreachable;
+    const html_node = try bc.node_registry.register(html.asNode());
+    const document_node = try bc.node_registry.register(root.document.asNode());
+
+    // The auxiliary session mints an id for <html> and resolves it.
+    try ctx.processMessage(.{ .id = 20, .method = "DOM.resolveNode", .sessionId = "SID-AUX", .params = .{ .backendNodeId = html_node.id } });
+    const aux_object_id = try sentObjectId(&ctx, 20);
+    try ctx.processMessage(.{ .id = 21, .method = "DOM.requestNode", .sessionId = "SID-AUX", .params = .{ .objectId = aux_object_id } });
+    try ctx.expectSentResult(.{ .nodeId = html_node.id }, .{ .id = 21, .session_id = "SID-AUX" });
+
+    // The primary has minted nothing yet: the auxiliary's id is not its.
+    try ctx.processMessage(.{ .id = 22, .method = "Runtime.callFunctionOn", .sessionId = "SID-PRIMARY", .params = .{
+        .objectId = aux_object_id,
+        .functionDeclaration = "function() { return this.localName; }",
+        .returnByValue = true,
+    } });
+    try ctx.expectSentError(-32000, "Could not find object with given id", .{ .id = 22 });
+
+    // Each session numbers its ids by itself, so the primary's first id may
+    // well be the same string as the auxiliary's: the session a command comes
+    // through, not the id, tells the objects apart. Mint a different node on
+    // the primary and check that each id describes its own.
+    try ctx.processMessage(.{ .id = 23, .method = "DOM.resolveNode", .sessionId = "SID-PRIMARY", .params = .{ .backendNodeId = document_node.id } });
+    const primary_object_id = try sentObjectId(&ctx, 23);
+    try ctx.processMessage(.{ .id = 24, .method = "DOM.describeNode", .sessionId = "SID-PRIMARY", .params = .{ .objectId = primary_object_id } });
+    try ctx.expectSentResult(.{ .node = .{ .nodeId = document_node.id, .nodeName = "#document" } }, .{ .id = 24, .session_id = "SID-PRIMARY" });
+    try ctx.processMessage(.{ .id = 25, .method = "DOM.describeNode", .sessionId = "SID-AUX", .params = .{ .objectId = aux_object_id } });
+    try ctx.expectSentResult(.{ .node = .{ .nodeId = html_node.id, .localName = "html" } }, .{ .id = 25, .session_id = "SID-AUX" });
+    try ctx.processMessage(.{ .id = 26, .method = "DOM.requestNode", .sessionId = "SID-PRIMARY", .params = .{ .objectId = primary_object_id } });
+    try ctx.expectSentResult(.{ .nodeId = document_node.id }, .{ .id = 26, .session_id = "SID-PRIMARY" });
+    try ctx.processMessage(.{ .id = 27, .method = "DOM.requestNode", .sessionId = "SID-AUX", .params = .{ .objectId = aux_object_id } });
+    try ctx.expectSentResult(.{ .nodeId = html_node.id }, .{ .id = 27, .session_id = "SID-AUX" });
 }
 
 // The result.object.objectId of the response to command `msg_id`.

src/server/cdp/domains/fetch.zig

@@ -595,10 +595,7 @@ test "cdp.Fetch: interception events belong to the enabling session" {
         .session_id = "SID-PRIMARY",
         .target_id = "TID-000000000B".*,
     });
-    try bc.attached_sessions.append(bc.arena, .{
-        .id = "SID-AUX",
-        .parent_id = null,
-    });
+    _ = try bc.attachSession("SID-AUX", null);
 
     try ctx.processMessage(.{
         .id = 1,

src/server/cdp/domains/network.zig

@@ -1591,7 +1591,7 @@ test "cdp.Network: worker requests emit network events" {
     _ = try cdp.createBrowserContext();
     var bc = &cdp.browser_context.?;
     bc.id = "BID-NW";
-    bc.session_id = "SID-NW";
+    _ = try bc.attachPrimarySession("SID-NW");
     bc.target_id = "TID-NW-0000000".*;
 
     try ctx.processMessage(.{ .id = 1, .method = "Network.enable" });

src/server/cdp/domains/page.zig

@@ -284,7 +284,7 @@ fn createIsolatedWorld(cmd: *CDP.Command) !void {
     var ls: js.Local.Scope = undefined;
     js_context.localScope(&ls);
     defer ls.deinit();
-    const context_id = bc.inspector_session.inspector.getContextId(&ls.local);
+    const context_id = bc.inspector().getContextId(&ls.local);
     return cmd.sendResult(.{ .executionContextId = context_id }, .{});
 }
 
@@ -315,7 +315,7 @@ fn registerIsolatedWorldContext(arena: Allocator, bc: *CDP.BrowserContext, world
     js_context.localScope(&ls);
     defer ls.deinit();
 
-    bc.inspector_session.inspector.contextCreated(
+    bc.inspector().contextCreated(
         &ls.local,
         world.name,
         frame.origin orelse "",
@@ -558,7 +558,7 @@ pub fn frameNavigate(bc: *CDP.BrowserContext, event: *const Notification.FrameNa
 pub fn frameRemove(bc: *CDP.BrowserContext) void {
     // Clear all remote object mappings to prevent stale objectIds from being used
     // after the context is destroy
-    bc.inspector_session.inspector.resetContextGroup();
+    bc.inspector().resetContextGroup();
 
     // The main frame is going to be removed, we need to remove contexts from other worlds first.
     for (bc.isolated_worlds.items) |isolated_world| {
@@ -743,7 +743,7 @@ pub fn frameNavigated(arena: Allocator, bc: *CDP.BrowserContext, event: *const N
         frame.js.localScope(&ls);
         defer ls.deinit();
 
-        bc.inspector_session.inspector.contextCreated(
+        bc.inspector().contextCreated(
             &ls.local,
             "",
             frame.origin orelse "",
@@ -1735,7 +1735,7 @@ fn isolatedWorldContextId(bc: *CDP.BrowserContext, frame: *const Frame) !i32 {
     var ls: js.Local.Scope = undefined;
     js_context.localScope(&ls);
     defer ls.deinit();
-    return bc.inspector_session.inspector.getContextId(&ls.local);
+    return bc.inspector().getContextId(&ls.local);
 }
 
 test "cdp.frame: child frame metadata" {
@@ -2170,7 +2170,7 @@ test "cdp.frame: reload replays POST navigation" {
     _ = try cdp_inst.createBrowserContext();
     var bc = &cdp_inst.browser_context.?;
     bc.id = "BID-A6";
-    bc.session_id = "SID-X";
+    _ = try bc.attachPrimarySession("SID-X");
     bc.target_id = "TID-A6-0000000".*;
 
     // First navigation: POST a form-style payload to /echo_method.
@@ -2222,7 +2222,7 @@ test "cdp.frame: reload after POST→redirect drops the POST" {
     _ = try cdp_inst.createBrowserContext();
     var bc = &cdp_inst.browser_context.?;
     bc.id = "BID-A6R";
-    bc.session_id = "SID-XR";
+    _ = try bc.attachPrimarySession("SID-XR");
     bc.target_id = "TID-A6R-000000".*;
 
     // First navigation: POST /redirect_to_echo → 302 → GET /echo_method.
@@ -2486,7 +2486,7 @@ test "cdp.frame: first navigation of a pristine bootstrap about:blank navigates
     defer ctx.deinit();
 
     var bc = try ctx.loadBrowserContext(.{ .id = "BID-PRS", .target_id = "TID-PRS-000000".* });
-    bc.session_id = "SID-PRS";
+    _ = try bc.attachPrimarySession("SID-PRS");
     _ = try bc.session.createPage();
     const before = bc.mainFrame() orelse unreachable;
     try testing.expectEqualSlices(u8, "about:blank", before.url);
@@ -2515,7 +2515,7 @@ test "cdp.frame: anchor click sends Referer matching the originating page" {
     _ = try cdp_inst.createBrowserContext();
     var bc = &cdp_inst.browser_context.?;
     bc.id = "BID-A18";
-    bc.session_id = "SID-A18";
+    _ = try bc.attachPrimarySession("SID-A18");
     bc.target_id = "TID-A18-000000".*;
 
     // Initial navigation to the page hosting the anchor — driven directly via
@@ -2564,7 +2564,7 @@ test "cdp.frame: address-bar Page.navigate sends no Referer" {
     _ = try cdp_inst.createBrowserContext();
     var bc = &cdp_inst.browser_context.?;
     bc.id = "BID-A18B";
-    bc.session_id = "SID-A18B";
+    _ = try bc.attachPrimarySession("SID-A18B");
     bc.target_id = "TID-A18B-00000".*;
 
     {

src/server/cdp/domains/runtime.zig

@@ -80,7 +80,7 @@ fn sendInspector(cmd: *CDP.Command) !void {
     const bc = cmd.browser_context orelse return error.BrowserContextNotLoaded;
 
     // the result to return is handled directly by the inspector.
-    bc.callInspector(cmd.input.json);
+    try bc.callInspector(cmd);
 }
 
 // Object arguments stay remote handles; serializing them would execute page JS.
@@ -127,18 +127,21 @@ const ConsoleMessage = struct {
 };
 
 pub fn consoleMessage(arena: Allocator, bc: *CDP.BrowserContext, event: *const Notification.ConsoleMessage) !void {
+    // The event goes to the primary session, so its argument handles are
+    // minted on the primary's inspector session.
     const session_id = bc.session_id orelse return;
+    const inspector_session = try bc.inspectorSession(session_id);
     const frame = bc.mainFrame() orelse return error.FrameNotLoaded;
 
     var ls: js.Local.Scope = undefined;
     frame.js.localScope(&ls);
     defer ls.deinit();
 
-    const context_id = bc.inspector_session.inspector.getContextId(&ls.local);
+    const context_id = bc.inspector().getContextId(&ls.local);
 
     var args: std.ArrayList(RemoteObject) = .empty;
     for (event.values) |value| {
-        const remote_object = try bc.inspector_session.getRemoteObject(
+        const remote_object = try inspector_session.getRemoteObject(
             &ls.local,
             "",
             value,
@@ -180,6 +183,77 @@ test "cdp.runtime: inspector-handled methods pass through" {
     try ctx.expectSentResult(null, .{ .id = 52 });
 }
 
+// Playwright's browserContext.newCDPSession attaches a second session to the
+// page and sends Runtime commands through it. The inspector's answer must
+// carry that session's id: the driver keys its pending callbacks by session
+// and asserts on a response it can't match (lightpanda-io/browser#1838).
+test "cdp.runtime: inspector responses go to the session that sent the command" {
+    var ctx = try testing.context();
+    defer ctx.deinit();
+
+    const bc = try ctx.loadBrowserContext(.{ .id = "BID-RT2", .url = "hi.html", .target_id = "FID-0000000RT2".*, .session_id = "SID-PRIMARY" });
+    _ = try bc.attachSession("SID-AUX", null);
+
+    try ctx.processMessage(.{ .id = 60, .method = "Runtime.evaluate", .sessionId = "SID-AUX", .params = .{ .expression = "1 + 1", .returnByValue = true } });
+    try ctx.expectSentResult(.{ .result = .{ .type = "number", .value = 2, .description = "2" } }, .{ .id = 60, .session_id = "SID-AUX" });
+
+    // The primary session keeps working as before.
+    try ctx.processMessage(.{ .id = 61, .method = "Runtime.evaluate", .sessionId = "SID-PRIMARY", .params = .{ .expression = "2 + 2", .returnByValue = true } });
+    try ctx.expectSentResult(.{ .result = .{ .type = "number", .value = 4, .description = "4" } }, .{ .id = 61, .session_id = "SID-PRIMARY" });
+
+    // A response the inspector produces after the dispatch (awaitPromise
+    // answers from a microtask) still finds its session.
+    try ctx.processMessage(.{ .id = 62, .method = "Runtime.evaluate", .sessionId = "SID-AUX", .params = .{ .expression = "Promise.resolve('late')", .awaitPromise = true, .returnByValue = true } });
+    try ctx.expectSentResult(.{ .result = .{ .type = "string", .value = "late" } }, .{ .id = 62, .session_id = "SID-AUX" });
+
+    // A command with no sessionId is answered on the primary session.
+    try ctx.processMessage(.{ .id = 63, .method = "Runtime.evaluate", .params = .{ .expression = "3 + 3", .returnByValue = true } });
+    try ctx.expectSentResult(.{ .result = .{ .type = "number", .value = 6, .description = "6" } }, .{ .id = 63, .session_id = "SID-PRIMARY" });
+}
+
+// Number of `method` events the client received on `session_id`.
+fn countSentEvents(ctx: *testing.TestContext, method: []const u8, session_id: []const u8) !usize {
+    var count: usize = 0;
+    var i: usize = 0;
+    while (try ctx.getSentMessage(i)) |msg| : (i += 1) {
+        const obj = switch (msg) {
+            .object => |o| o,
+            else => continue,
+        };
+        const sent_method = obj.get("method") orelse continue;
+        if (sent_method != .string or !std.mem.eql(u8, sent_method.string, method)) {
+            continue;
+        }
+        const sent_session_id = obj.get("sessionId") orelse continue;
+        if (sent_session_id == .string and std.mem.eql(u8, sent_session_id.string, session_id)) {
+            count += 1;
+        }
+    }
+    return count;
+}
+
+// V8 keeps Runtime.enable per inspector session: a session only gets the
+// executionContextCreated events it asked for, stamped with its own id.
+test "cdp.runtime: inspector events go to the session that enabled them" {
+    var ctx = try testing.context();
+    defer ctx.deinit();
+
+    const bc = try ctx.loadBrowserContext(.{ .id = "BID-RT3", .url = "hi.html", .target_id = "FID-0000000RT3".*, .session_id = "SID-PRIMARY" });
+    _ = try bc.attachSession("SID-AUX", null);
+
+    try ctx.processMessage(.{ .id = 70, .method = "Runtime.enable", .sessionId = "SID-AUX" });
+    try ctx.expectSentResult(null, .{ .id = 70, .session_id = "SID-AUX" });
+    try ctx.expectSentEvent("Runtime.executionContextCreated", .{ .context = .{ .auxData = .{ .isDefault = true, .type = "default" } } }, .{ .session_id = "SID-AUX" });
+    try testing.expectEqual(1, try countSentEvents(&ctx, "Runtime.executionContextCreated", "SID-AUX"));
+    try testing.expectEqual(0, try countSentEvents(&ctx, "Runtime.executionContextCreated", "SID-PRIMARY"));
+
+    try ctx.processMessage(.{ .id = 71, .method = "Runtime.enable", .sessionId = "SID-PRIMARY" });
+    try ctx.expectSentResult(null, .{ .id = 71, .session_id = "SID-PRIMARY" });
+    try ctx.expectSentEvent("Runtime.executionContextCreated", .{ .context = .{ .auxData = .{ .isDefault = true, .type = "default" } } }, .{ .session_id = "SID-PRIMARY" });
+    try testing.expectEqual(1, try countSentEvents(&ctx, "Runtime.executionContextCreated", "SID-AUX"));
+    try testing.expectEqual(1, try countSentEvents(&ctx, "Runtime.executionContextCreated", "SID-PRIMARY"));
+}
+
 test "cdp.runtime: consoleAPICalled type matches the console method" {
     testing.silenceLog(&.{.js});
 

src/server/cdp/domains/target.zig

@@ -196,7 +196,7 @@ fn createTarget(cmd: *CDP.Command) !void {
         defer ls.deinit();
 
         const aux_data = try std.fmt.allocPrint(cmd.arena, "{{\"isDefault\":true,\"type\":\"default\",\"frameId\":\"{s}\"}}", .{target_id});
-        bc.inspector_session.inspector.contextCreated(
+        bc.inspector().contextCreated(
             &ls.local,
             "",
             "", // @ZIGDOM
@@ -267,14 +267,10 @@ fn attachToTarget(cmd: *CDP.Command) !void {
         cmd.cdp.resolveSessionId(session_id) orelse return error.UnknownSessionId
     else
         null;
-    const session_id = try bc.arena.dupe(u8, cmd.cdp.session_id_gen.next());
-    try bc.attached_sessions.append(bc.arena, .{
-        .id = session_id,
-        .parent_id = parent_id,
-    });
+    const session = try bc.attachSession(cmd.cdp.session_id_gen.next(), parent_id);
 
     try cmd.sendEvent("Target.attachedToTarget", AttachToTarget{
-        .sessionId = session_id,
+        .sessionId = session.id,
         .targetInfo = TargetInfo{
             .targetId = target_id,
             .title = bc.getTitle() orelse "",
@@ -283,7 +279,7 @@ fn attachToTarget(cmd: *CDP.Command) !void {
         },
     }, .{ .session_id = parent_id });
 
-    return cmd.sendResult(.{ .sessionId = session_id }, .{});
+    return cmd.sendResult(.{ .sessionId = session.id }, .{});
 }
 
 fn attachToBrowserTarget(cmd: *CDP.Command) !void {
@@ -402,31 +398,18 @@ fn detachFromTarget(cmd: *CDP.Command) !void {
     const params = (try cmd.params(Params)) orelse Params{};
 
     if (cmd.browser_context) |bc| {
-        if (params.sessionId) |requested_session_id| {
-            for (bc.attached_sessions.items, 0..) |session, index| {
-                if (!std.mem.eql(u8, session.id, requested_session_id)) continue;
+        // Without a sessionId, detach the primary session (if any).
+        if (params.sessionId orelse bc.session_id) |requested_session_id| {
+            const session = bc.attached_sessions.get(requested_session_id) orelse return error.UnknownSessionId;
+            const session_id = session.id;
+            const parent_id = session.parent_id;
 
-                _ = bc.attached_sessions.orderedRemove(index);
-                bc.fetchDisableForSession(session.id);
-                try cmd.sendEvent("Target.detachedFromTarget", .{
-                    .sessionId = session.id,
-                }, .{ .session_id = session.parent_id });
-                return cmd.sendResult(null, .{});
-            }
-
-            const session_id = bc.session_id orelse return error.UnknownSessionId;
-            if (!std.mem.eql(u8, session_id, requested_session_id)) {
-                return error.UnknownSessionId;
-            }
-        }
-
-        if (bc.session_id) |session_id| {
             bc.fetchDisableForSession(session_id);
             try cmd.sendEvent("Target.detachedFromTarget", .{
                 .sessionId = session_id,
-            }, .{});
+            }, .{ .session_id = parent_id });
+            _ = bc.detachSession(session_id);
         }
-        bc.session_id = null;
     }
 
     return cmd.sendResult(null, .{});
@@ -456,8 +439,8 @@ fn setAutoAttach(cmd: *CDP.Command) !void {
                 try cmd.sendEvent("Target.detachedFromTarget", .{
                     .sessionId = session_id,
                 }, .{});
+                _ = bc.detachSession(session_id);
             }
-            bc.session_id = null;
         }
         try cmd.sendResult(null, .{});
         return;
@@ -500,27 +483,24 @@ fn setAutoAttach(cmd: *CDP.Command) !void {
 
 fn doAttachtoTarget(cmd: *CDP.Command, target_id: []const u8) !void {
     const bc = cmd.browser_context.?;
-    const session_id = bc.session_id orelse blk: {
-        break :blk try bc.arena.dupe(u8, cmd.cdp.session_id_gen.next());
-    };
+    const parent_id = bc.session_id;
 
     if (bc.session_id == null) {
         // extra_headers should not be kept on a new frame or tab,
         // currently we have only 1 frame, we clear it just in case
         bc.extra_headers.clearRetainingCapacity();
+        _ = try bc.attachPrimarySession(cmd.cdp.session_id_gen.next());
     }
 
     try cmd.sendEvent("Target.attachedToTarget", AttachToTarget{
-        .sessionId = session_id,
+        .sessionId = bc.session_id.?,
         .targetInfo = TargetInfo{
             .targetId = target_id,
             .title = bc.getTitle() orelse "",
             .url = bc.getURL() orelse "about:blank",
             .browserContextId = bc.id,
         },
-    }, .{ .session_id = bc.session_id });
-
-    bc.session_id = session_id;
+    }, .{ .session_id = parent_id });
 }
 
 const AttachToTarget = struct {
@@ -629,7 +609,9 @@ test "cdp.target: disposeBrowserContext detaches target sessions" {
         .sessionId = "BSID-1",
         .params = .{ .targetId = target_id },
     });
-    const auxiliary_id = try testing.arena_allocator.dupe(u8, bc.attached_sessions.items[0].id);
+    // the primary is attached first, the auxiliary session after it
+    try testing.expectEqual(2, bc.attached_sessions.count());
+    const auxiliary_id = try testing.arena_allocator.dupe(u8, bc.attached_sessions.keys()[1]);
 
     try ctx.processMessage(.{
         .id = 5,
@@ -909,7 +891,8 @@ test "cdp.target: attachToTarget" {
         const session_id = bc.session_id.?;
         try ctx.expectSentResult(.{ .sessionId = session_id }, .{ .id = 11 });
         try ctx.expectSentEvent("Target.attachedToTarget", .{ .sessionId = session_id, .targetInfo = .{ .url = "about:blank", .title = "", .attached = true, .type = "page", .canAccessOpener = false, .browserContextId = "BID-9", .targetId = bc.target_id.? } }, .{});
-        try testing.expectEqual(0, bc.attached_sessions.items.len);
+        try testing.expectEqual(1, bc.attached_sessions.count());
+        try testing.expect(bc.attached_sessions.contains(session_id));
     }
 }
 
@@ -930,7 +913,9 @@ test "cdp.target: auxiliary session is unique and routed through its parent" {
         .params = .{ .targetId = "TID-000000000B" },
     });
 
-    const session_id = bc.attached_sessions.items[0].id;
+    // the primary is attached first, the auxiliary session after it
+    try testing.expectEqual(2, bc.attached_sessions.count());
+    const session_id = bc.attached_sessions.keys()[1];
     try testing.expect(!std.mem.eql(u8, session_id, bc.session_id.?));
     try ctx.expectSentEvent("Target.attachedToTarget", .{
         .sessionId = session_id,
@@ -1045,16 +1030,78 @@ test "cdp.target: detachFromTarget auxiliary session" {
     });
 
     try ctx.processMessage(.{ .id = 10, .method = "Target.attachToTarget", .params = .{ .targetId = "TID-000000000B" } });
-    const session_id = bc.attached_sessions.items[0].id;
+    try testing.expectEqual(2, bc.attached_sessions.count());
+    const session_id = bc.attached_sessions.keys()[1];
     try testing.expect(!std.mem.eql(u8, session_id, bc.session_id.?));
 
     try ctx.processMessage(.{ .id = 11, .method = "Target.detachFromTarget", .params = .{ .sessionId = session_id } });
     try ctx.expectSentEvent("Target.detachedFromTarget", .{ .sessionId = session_id }, .{});
-    try testing.expectEqual(0, bc.attached_sessions.items.len);
+    try testing.expectEqual(1, bc.attached_sessions.count());
     try testing.expectEqual(true, bc.session_id != null);
     try ctx.expectSentResult(null, .{ .id = 11 });
 }
 
+// A detached session's inspector session goes with it: commands on the old
+// id are rejected up front and the primary is unaffected.
+test "cdp.target: detachFromTarget releases the auxiliary session's inspector session" {
+    var ctx = try testing.context();
+    defer ctx.deinit();
+    const bc = try ctx.loadBrowserContext(.{
+        .id = "BID-9",
+        .url = "hi.html",
+        .session_id = "SID-PRIMARY",
+        .target_id = "TID-000000000B".*,
+    });
+    _ = try bc.attachSession("SID-AUX", null);
+
+    try ctx.processMessage(.{ .id = 10, .method = "Runtime.evaluate", .sessionId = "SID-AUX", .params = .{ .expression = "1 + 1", .returnByValue = true } });
+    try ctx.expectSentResult(.{ .result = .{ .type = "number", .value = 2 } }, .{ .id = 10, .session_id = "SID-AUX" });
+
+    try ctx.processMessage(.{ .id = 11, .method = "Target.detachFromTarget", .params = .{ .sessionId = "SID-AUX" } });
+    try ctx.expectSentEvent("Target.detachedFromTarget", .{ .sessionId = "SID-AUX" }, .{});
+    try ctx.expectSentResult(null, .{ .id = 11 });
+    try testing.expectEqual(1, bc.attached_sessions.count());
+
+    try ctx.processMessage(.{ .id = 12, .method = "Runtime.evaluate", .sessionId = "SID-AUX", .params = .{ .expression = "1 + 1", .returnByValue = true } });
+    try ctx.expectSentError(-32001, "Unknown sessionId", .{ .id = 12 });
+
+    try ctx.processMessage(.{ .id = 13, .method = "Runtime.evaluate", .sessionId = "SID-PRIMARY", .params = .{ .expression = "2 + 2", .returnByValue = true } });
+    try ctx.expectSentResult(.{ .result = .{ .type = "number", .value = 4 } }, .{ .id = 13, .session_id = "SID-PRIMARY" });
+}
+
+// Stopping an inspector session fails its pending evaluations. The client was
+// already told the session is detached, so, like Chrome, nothing more is sent.
+test "cdp.target: detachFromTarget drops the auxiliary session's pending responses" {
+    var ctx = try testing.context();
+    defer ctx.deinit();
+    const bc = try ctx.loadBrowserContext(.{
+        .id = "BID-9",
+        .url = "hi.html",
+        .session_id = "SID-PRIMARY",
+        .target_id = "TID-000000000B".*,
+    });
+    _ = try bc.attachSession("SID-AUX", null);
+
+    try ctx.processMessage(.{ .id = 10, .method = "Runtime.enable", .sessionId = "SID-AUX" });
+    try ctx.expectSentResult(null, .{ .id = 10, .session_id = "SID-AUX" });
+    try ctx.processMessage(.{ .id = 11, .method = "Runtime.evaluate", .sessionId = "SID-AUX", .params = .{ .expression = "({a: 1})" } });
+    try ctx.expectSentResult(.{ .result = .{ .type = "object" } }, .{ .id = 11, .session_id = "SID-AUX" });
+    try ctx.processMessage(.{ .id = 12, .method = "Runtime.evaluate", .sessionId = "SID-AUX", .params = .{ .expression = "new Promise(() => {})", .awaitPromise = true } });
+
+    try ctx.processMessage(.{ .id = 13, .method = "Target.detachFromTarget", .params = .{ .sessionId = "SID-AUX" } });
+    try ctx.expectSentEvent("Target.detachedFromTarget", .{ .sessionId = "SID-AUX" }, .{});
+    try ctx.expectSentResult(null, .{ .id = 13 });
+
+    var i: usize = 0;
+    while (try ctx.getSentMessage(i)) |msg| : (i += 1) {
+        const msg_id = msg.object.get("id") orelse continue;
+        try testing.expect(msg_id != .integer or msg_id.integer != 12);
+    }
+
+    try ctx.processMessage(.{ .id = 14, .method = "Runtime.evaluate", .sessionId = "SID-PRIMARY", .params = .{ .expression = "2 + 2", .returnByValue = true } });
+    try ctx.expectSentResult(.{ .result = .{ .type = "number", .value = 4 } }, .{ .id = 14, .session_id = "SID-PRIMARY" });
+}
+
 test "cdp.target: detachFromTarget without session" {
     var ctx = try testing.context();
     defer ctx.deinit();

src/server/cdp/testing.zig

@@ -95,12 +95,12 @@ pub const TestContext = struct {
         }
 
         if (opts.session_id) |sid| {
-            bc.session_id = sid;
+            _ = try bc.attachPrimarySession(sid);
         }
 
         if (opts.url) |url| {
             if (bc.session_id == null) {
-                bc.session_id = "SID-X";
+                _ = try bc.attachPrimarySession("SID-X");
             }
             if (bc.target_id == null) {
                 bc.target_id = "TID-000000000Z".*;