Merge branch 'main' into semantic-versioning

src/ArenaPool.zig

@@ -17,12 +17,15 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const builtin = @import("builtin");
 
 const Allocator = std.mem.Allocator;
 const ArenaAllocator = std.heap.ArenaAllocator;
 
 const ArenaPool = @This();
 
+const IS_DEBUG = builtin.mode == .Debug;
+
 allocator: Allocator,
 retain_bytes: usize,
 free_list_len: u16 = 0,
@@ -30,10 +33,17 @@ free_list: ?*Entry = null,
 free_list_max: u16,
 entry_pool: std.heap.MemoryPool(Entry),
 mutex: std.Thread.Mutex = .{},
+// Debug mode: track acquire/release counts per debug name to detect leaks and double-frees
+_leak_track: if (IS_DEBUG) std.StringHashMapUnmanaged(isize) else void = if (IS_DEBUG) .empty else {},
 
 const Entry = struct {
     next: ?*Entry,
     arena: ArenaAllocator,
+    debug: if (IS_DEBUG) []const u8 else void = if (IS_DEBUG) "" else {},
+};
+
+pub const DebugInfo = struct {
+    debug: []const u8 = "",
 };
 
 pub fn init(allocator: Allocator, free_list_max: u16, retain_bytes: usize) ArenaPool {
@@ -42,10 +52,26 @@ pub fn init(allocator: Allocator, free_list_max: u16, retain_bytes: usize) Arena
         .free_list_max = free_list_max,
         .retain_bytes = retain_bytes,
         .entry_pool = .init(allocator),
+        ._leak_track = if (IS_DEBUG) .empty else {},
     };
 }
 
 pub fn deinit(self: *ArenaPool) void {
+    if (IS_DEBUG) {
+        var has_leaks = false;
+        var it = self._leak_track.iterator();
+        while (it.next()) |kv| {
+            if (kv.value_ptr.* != 0) {
+                std.debug.print("ArenaPool leak detected: '{s}' count={d}\n", .{ kv.key_ptr.*, kv.value_ptr.* });
+                has_leaks = true;
+            }
+        }
+        if (has_leaks) {
+            @panic("ArenaPool: leaked arenas detected");
+        }
+        self._leak_track.deinit(self.allocator);
+    }
+
     var entry = self.free_list;
     while (entry) |e| {
         entry = e.next;
@@ -54,13 +80,21 @@ pub fn deinit(self: *ArenaPool) void {
     self.entry_pool.deinit();
 }
 
-pub fn acquire(self: *ArenaPool) !Allocator {
+pub fn acquire(self: *ArenaPool, dbg: DebugInfo) !Allocator {
     self.mutex.lock();
     defer self.mutex.unlock();
 
     if (self.free_list) |entry| {
         self.free_list = entry.next;
         self.free_list_len -= 1;
+        if (IS_DEBUG) {
+            entry.debug = dbg.debug;
+            const gop = try self._leak_track.getOrPut(self.allocator, dbg.debug);
+            if (!gop.found_existing) {
+                gop.value_ptr.* = 0;
+            }
+            gop.value_ptr.* += 1;
+        }
         return entry.arena.allocator();
     }
 
@@ -68,8 +102,16 @@ pub fn acquire(self: *ArenaPool) !Allocator {
     entry.* = .{
         .next = null,
         .arena = ArenaAllocator.init(self.allocator),
+        .debug = if (IS_DEBUG) dbg.debug else {},
     };
 
+    if (IS_DEBUG) {
+        const gop = try self._leak_track.getOrPut(self.allocator, dbg.debug);
+        if (!gop.found_existing) {
+            gop.value_ptr.* = 0;
+        }
+        gop.value_ptr.* += 1;
+    }
     return entry.arena.allocator();
 }
 
@@ -83,6 +125,19 @@ pub fn release(self: *ArenaPool, allocator: Allocator) void {
     self.mutex.lock();
     defer self.mutex.unlock();
 
+    if (IS_DEBUG) {
+        if (self._leak_track.getPtr(entry.debug)) |count| {
+            count.* -= 1;
+            if (count.* < 0) {
+                std.debug.print("ArenaPool double-free detected: '{s}'\n", .{entry.debug});
+                @panic("ArenaPool: double-free detected");
+            }
+        } else {
+            std.debug.print("ArenaPool release of untracked arena: '{s}'\n", .{entry.debug});
+            @panic("ArenaPool: release of untracked arena");
+        }
+    }
+
     const free_list_len = self.free_list_len;
     if (free_list_len == self.free_list_max) {
         arena.deinit();
@@ -106,7 +161,7 @@ test "arena pool - basic acquire and use" {
     var pool = ArenaPool.init(testing.allocator, 512, 1024 * 16);
     defer pool.deinit();
 
-    const alloc = try pool.acquire();
+    const alloc = try pool.acquire(.{ .debug = "test" });
     const buf = try alloc.alloc(u8, 64);
     @memset(buf, 0xAB);
     try testing.expectEqual(@as(u8, 0xAB), buf[0]);
@@ -118,14 +173,14 @@ test "arena pool - reuse entry after release" {
     var pool = ArenaPool.init(testing.allocator, 512, 1024 * 16);
     defer pool.deinit();
 
-    const alloc1 = try pool.acquire();
+    const alloc1 = try pool.acquire(.{ .debug = "test" });
     try testing.expectEqual(@as(u16, 0), pool.free_list_len);
 
     pool.release(alloc1);
     try testing.expectEqual(@as(u16, 1), pool.free_list_len);
 
     // The same entry should be returned from the free list.
-    const alloc2 = try pool.acquire();
+    const alloc2 = try pool.acquire(.{ .debug = "test" });
     try testing.expectEqual(@as(u16, 0), pool.free_list_len);
     try testing.expectEqual(alloc1.ptr, alloc2.ptr);
 
@@ -136,9 +191,9 @@ test "arena pool - multiple concurrent arenas" {
     var pool = ArenaPool.init(testing.allocator, 512, 1024 * 16);
     defer pool.deinit();
 
-    const a1 = try pool.acquire();
+    const a1 = try pool.acquire(.{ .debug = "test1" });
-    const a2 = try pool.acquire();
+    const a2 = try pool.acquire(.{ .debug = "test2" });
-    const a3 = try pool.acquire();
+    const a3 = try pool.acquire(.{ .debug = "test3" });
 
     // All three must be distinct arenas.
     try testing.expect(a1.ptr != a2.ptr);
@@ -161,8 +216,8 @@ test "arena pool - free list respects max limit" {
     var pool = ArenaPool.init(testing.allocator, 1, 1024 * 16);
     defer pool.deinit();
 
-    const a1 = try pool.acquire();
+    const a1 = try pool.acquire(.{ .debug = "test1" });
-    const a2 = try pool.acquire();
+    const a2 = try pool.acquire(.{ .debug = "test2" });
 
     pool.release(a1);
     try testing.expectEqual(@as(u16, 1), pool.free_list_len);
@@ -176,7 +231,7 @@ test "arena pool - reset clears memory without releasing" {
     var pool = ArenaPool.init(testing.allocator, 512, 1024 * 16);
     defer pool.deinit();
 
-    const alloc = try pool.acquire();
+    const alloc = try pool.acquire(.{ .debug = "test" });
 
     const buf = try alloc.alloc(u8, 128);
     @memset(buf, 0xFF);
@@ -200,8 +255,8 @@ test "arena pool - deinit with entries in free list" {
     // detected by the test allocator).
     var pool = ArenaPool.init(testing.allocator, 512, 1024 * 16);
 
-    const a1 = try pool.acquire();
+    const a1 = try pool.acquire(.{ .debug = "test1" });
-    const a2 = try pool.acquire();
+    const a2 = try pool.acquire(.{ .debug = "test2" });
     _ = try a1.alloc(u8, 256);
     _ = try a2.alloc(u8, 512);
     pool.release(a1);

src/Config.zig

@@ -217,6 +217,13 @@ pub const DumpFormat = enum {
     semantic_tree_text,
 };
 
+pub const WaitUntil = enum {
+    load,
+    domcontentloaded,
+    networkidle,
+    fixed,
+};
+
 pub const Fetch = struct {
     url: [:0]const u8,
     dump_mode: ?DumpFormat = null,
@@ -224,6 +231,8 @@ pub const Fetch = struct {
     with_base: bool = false,
     with_frames: bool = false,
     strip: dump.Opts.Strip = .{},
+    wait_ms: u32 = 5000,
+    wait_until: WaitUntil = .load,
 };
 
 pub const Common = struct {
@@ -387,6 +396,13 @@ pub fn printUsageAndExit(self: *const Config, success: bool) void {
         \\
         \\--with_frames   Includes the contents of iframes. Defaults to false.
         \\
+        \\--wait_ms       Wait time in milliseconds.
+        \\                Defaults to 5000.
+        \\
+        \\--wait_until    Wait until the specified event.
+        \\                Supported events: load, domcontentloaded, networkidle, fixed.
+        \\                Defaults to 'load'.
+        \\
     ++ common_options ++
         \\
         \\serve command
@@ -619,8 +635,34 @@ fn parseFetchArgs(
     var url: ?[:0]const u8 = null;
     var common: Common = .{};
     var strip: dump.Opts.Strip = .{};
+    var wait_ms: u32 = 5000;
+    var wait_until: WaitUntil = .load;
 
     while (args.next()) |opt| {
+        if (std.mem.eql(u8, "--wait_ms", opt)) {
+            const str = args.next() orelse {
+                log.fatal(.app, "missing argument value", .{ .arg = "--wait_ms" });
+                return error.InvalidArgument;
+            };
+            wait_ms = std.fmt.parseInt(u32, str, 10) catch |err| {
+                log.fatal(.app, "invalid argument value", .{ .arg = "--wait_ms", .err = err });
+                return error.InvalidArgument;
+            };
+            continue;
+        }
+
+        if (std.mem.eql(u8, "--wait_until", opt)) {
+            const str = args.next() orelse {
+                log.fatal(.app, "missing argument value", .{ .arg = "--wait_until" });
+                return error.InvalidArgument;
+            };
+            wait_until = std.meta.stringToEnum(WaitUntil, str) orelse {
+                log.fatal(.app, "invalid argument value", .{ .arg = "--wait_until", .val = str });
+                return error.InvalidArgument;
+            };
+            continue;
+        }
+
         if (std.mem.eql(u8, "--dump", opt)) {
             var peek_args = args.*;
             if (peek_args.next()) |next_arg| {
@@ -709,6 +751,8 @@ fn parseFetchArgs(
         .common = common,
         .with_base = with_base,
         .with_frames = with_frames,
+        .wait_ms = wait_ms,
+        .wait_until = wait_until,
     };
 }
 

src/browser/Page.zig

@@ -302,7 +302,11 @@ pub fn init(self: *Page, frame_id: u32, session: *Session, parent: ?*Page) !void
     self._script_manager = ScriptManager.init(browser.allocator, browser.http_client, self);
     errdefer self._script_manager.deinit();
 
-    self.js = try browser.env.createContext(self);
+    self.js = try browser.env.createContext(self, .{
+        .identity = &session.identity,
+        .identity_arena = session.page_arena,
+        .call_arena = self.call_arena,
+    });
     errdefer self.js.deinit();
 
     document._page = self;

src/browser/Session.zig

@@ -24,6 +24,7 @@ const log = @import("../log.zig");
 const App = @import("../App.zig");
 
 const js = @import("js/js.zig");
+const v8 = js.v8;
 const storage = @import("webapi/storage/storage.zig");
 const Navigation = @import("webapi/navigation/Navigation.zig");
 const History = @import("webapi/History.zig");
@@ -65,17 +66,14 @@ page_arena: Allocator,
 // Origin map for same-origin context sharing. Scoped to the root page lifetime.
 origins: std.StringHashMapUnmanaged(*js.Origin) = .empty,
 
+// Identity tracking for the main world. All main world contexts share this,
+// ensuring object identity works across same-origin frames.
+identity: js.Identity = .{},
+
 // Shared resources for all pages in this session.
 // These live for the duration of the page tree (root + frames).
 arena_pool: *ArenaPool,
 
-// In Debug, we use this to see if anything fails to release an arena back to
-// the pool.
-_arena_pool_leak_track: if (IS_DEBUG) std.AutoHashMapUnmanaged(usize, struct {
-    owner: []const u8,
-    count: usize,
-}) else void = if (IS_DEBUG) .empty else {},
-
 page: ?Page,
 
 queued_navigation: std.ArrayList(*Page),
@@ -84,17 +82,17 @@ queued_navigation: std.ArrayList(*Page),
 // about:blank navigations (which may add to queued_navigation).
 queued_queued_navigation: std.ArrayList(*Page),
 
-page_id_gen: u32,
+page_id_gen: u32 = 0,
-frame_id_gen: u32,
+frame_id_gen: u32 = 0,
 
 pub fn init(self: *Session, browser: *Browser, notification: *Notification) !void {
     const allocator = browser.app.allocator;
     const arena_pool = browser.arena_pool;
 
-    const arena = try arena_pool.acquire();
+    const arena = try arena_pool.acquire(.{ .debug = "Session" });
     errdefer arena_pool.release(arena);
 
-    const page_arena = try arena_pool.acquire();
+    const page_arena = try arena_pool.acquire(.{ .debug = "Session.page_arena" });
     errdefer arena_pool.release(page_arena);
 
     self.* = .{
@@ -104,8 +102,6 @@ pub fn init(self: *Session, browser: *Browser, notification: *Notification) !voi
         .page_arena = page_arena,
         .factory = Factory.init(page_arena),
         .history = .{},
-        .page_id_gen = 0,
-        .frame_id_gen = 0,
         // The prototype (EventTarget) for Navigation is created when a Page is created.
         .navigation = .{ ._proto = undefined },
         .storage_shed = .{},
@@ -171,32 +167,11 @@ pub const GetArenaOpts = struct {
 };
 
 pub fn getArena(self: *Session, opts: GetArenaOpts) !Allocator {
-    const allocator = try self.arena_pool.acquire();
+    return self.arena_pool.acquire(.{ .debug = opts.debug });
-    if (comptime IS_DEBUG) {
-        // Use session's arena (not page_arena) since page_arena gets reset between pages
-        const gop = try self._arena_pool_leak_track.getOrPut(self.arena, @intFromPtr(allocator.ptr));
-        if (gop.found_existing and gop.value_ptr.count != 0) {
-            log.err(.bug, "ArenaPool Double Use", .{ .owner = gop.value_ptr.*.owner });
-            @panic("ArenaPool Double Use");
-        }
-        gop.value_ptr.* = .{ .owner = opts.debug, .count = 1 };
-    }
-    return allocator;
 }
 
 pub fn releaseArena(self: *Session, allocator: Allocator) void {
-    if (comptime IS_DEBUG) {
+    self.arena_pool.release(allocator);
-        const found = self._arena_pool_leak_track.getPtr(@intFromPtr(allocator.ptr)).?;
-        if (found.count != 1) {
-            log.err(.bug, "ArenaPool Double Free", .{ .owner = found.owner, .count = found.count });
-            if (comptime builtin.is_test) {
-                @panic("ArenaPool Double Free");
-            }
-            return;
-        }
-        found.count = 0;
-    }
-    return self.arena_pool.release(allocator);
 }
 
 pub fn getOrCreateOrigin(self: *Session, key_: ?[]const u8) !*js.Origin {
@@ -237,18 +212,9 @@ pub fn releaseOrigin(self: *Session, origin: *js.Origin) void {
 /// Reset page_arena and factory for a clean slate.
 /// Called when root page is removed.
 fn resetPageResources(self: *Session) void {
-    // Check for arena leaks before releasing
+    self.identity.deinit();
-    if (comptime IS_DEBUG) {
+    self.identity = .{};
-        var it = self._arena_pool_leak_track.valueIterator();
-        while (it.next()) |value_ptr| {
-            if (value_ptr.count > 0) {
-                log.err(.bug, "ArenaPool Leak", .{ .owner = value_ptr.owner });
-            }
-        }
-        self._arena_pool_leak_track.clearRetainingCapacity();
-    }
 
-    // All origins should have been released when contexts were destroyed
     if (comptime IS_DEBUG) {
         std.debug.assert(self.origins.count() == 0);
     }
@@ -259,10 +225,9 @@ fn resetPageResources(self: *Session) void {
         while (it.next()) |value| {
             value.*.deinit(app);
         }
-        self.origins.clearRetainingCapacity();
+        self.origins = .empty;
     }
 
-    // Release old page_arena and acquire fresh one
     self.frame_id_gen = 0;
     self.arena_pool.reset(self.page_arena, 64 * 1024);
     self.factory = Factory.init(self.page_arena);
@@ -319,10 +284,15 @@ fn findPageBy(page: *Page, comptime field: []const u8, id: u32) ?*Page {
     return null;
 }
 
-pub fn wait(self: *Session, wait_ms: u32) WaitResult {
+const WaitOpts = struct {
+    timeout_ms: u32 = 5000,
+    until: lp.Config.WaitUntil = .load,
+};
+
+pub fn wait(self: *Session, opts: WaitOpts) WaitResult {
     var page = &(self.page orelse return .no_page);
     while (true) {
-        const wait_result = self._wait(page, wait_ms) catch |err| {
+        const wait_result = self._wait(page, opts) catch |err| {
             switch (err) {
                 error.JsError => {}, // already logged (with hopefully more context)
                 else => log.err(.browser, "session wait", .{
@@ -346,9 +316,11 @@ pub fn wait(self: *Session, wait_ms: u32) WaitResult {
     }
 }
 
-fn _wait(self: *Session, page: *Page, wait_ms: u32) !WaitResult {
+fn _wait(self: *Session, page: *Page, opts: WaitOpts) !WaitResult {
+    const wait_until = opts.until;
+
     var timer = try std.time.Timer.start();
-    var ms_remaining = wait_ms;
+    var ms_remaining = opts.timeout_ms;
 
     const browser = self.browser;
     var http_client = browser.http_client;
@@ -372,7 +344,9 @@ fn _wait(self: *Session, page: *Page, wait_ms: u32) !WaitResult {
                 // There's no JS to run, and no reason to run the scheduler.
                 if (http_client.active == 0 and exit_when_done) {
                     // haven't started navigating, I guess.
-                    return .done;
+                    if (wait_until != .fixed) {
+                        return .done;
+                    }
                 }
                 // Either we have active http connections, or we're in CDP
                 // mode with an extra socket. Either way, we're waiting
@@ -423,17 +397,14 @@ fn _wait(self: *Session, page: *Page, wait_ms: u32) !WaitResult {
                         std.debug.assert(http_client.intercepted == 0);
                     }
 
-                    var ms = blk: {
+                    const is_event_done = switch (wait_until) {
-                        // if (wait_ms - ms_remaining < 100) {
+                        .fixed => false,
-                        //     if (comptime builtin.is_test) {
+                        .domcontentloaded => (page._load_state == .load or page._load_state == .complete),
-                        //         return .done;
+                        .load => (page._load_state == .complete),
-                        //     }
+                        .networkidle => (page._notified_network_idle == .done),
-                        //     // Look, we want to exit ASAP, but we don't want
+                    };
-                        //     // to exit so fast that we've run none of the
-                        //     // background jobs.
-                        //     break :blk 50;
-                        // }
 
+                    var ms = blk: {
                         if (browser.hasBackgroundTasks()) {
                             // _we_ have nothing to run, but v8 is working on
                             // background tasks. We'll wait for them.
@@ -441,19 +412,27 @@ fn _wait(self: *Session, page: *Page, wait_ms: u32) !WaitResult {
                             break :blk 20;
                         }
 
-                        break :blk browser.msToNextMacrotask() orelse return .done;
+                        const next_task = browser.msToNextMacrotask();
+                        if (next_task == null and is_event_done) {
+                            return .done;
+                        }
+                        break :blk next_task orelse 20;
                     };
 
                     if (ms > ms_remaining) {
+                        if (is_event_done) {
+                            return .done;
+                        }
                         // Same as above, except we have a scheduled task,
                         // it just happens to be too far into the future
                         // compared to how long we were told to wait.
-                        if (!browser.hasBackgroundTasks()) {
+                        if (browser.hasBackgroundTasks()) {
-                            return .done;
+                            // _we_ have nothing to run, but v8 is working on
+                            // background tasks. We'll wait for them.
+                            browser.waitForBackgroundTasks();
                         }
-                        // _we_ have nothing to run, but v8 is working on
+                        // We're still wait for our wait_until. Not sure for what
-                        // background tasks. We'll wait for them.
+                        // but let's keep waiting. Worst case, we'll timeout.
-                        browser.waitForBackgroundTasks();
                         ms = 20;
                     }
 
@@ -632,16 +611,6 @@ fn processRootQueuedNavigation(self: *Session) !void {
 
     defer self.arena_pool.release(qn.arena);
 
-    // HACK
-    // Mark as released in tracking BEFORE removePage clears the map.
-    // We can't call releaseArena() because that would also return the arena
-    // to the pool, making the memory invalid before we use qn.url/qn.opts.
-    if (comptime IS_DEBUG) {
-        if (self._arena_pool_leak_track.getPtr(@intFromPtr(qn.arena.ptr))) |found| {
-            found.count = 0;
-        }
-    }
-
     self.removePage();
 
     self.page = @as(Page, undefined);
@@ -672,3 +641,36 @@ pub fn nextPageId(self: *Session) u32 {
     self.page_id_gen = id;
     return id;
 }
+
+// A type that has a finalizer can have its finalizer called one of two ways.
+// The first is from V8 via the WeakCallback we give to weakRef. But that isn't
+// guaranteed to fire, so we track this in finalizer_callbacks and call them on
+// page reset.
+pub const FinalizerCallback = struct {
+    arena: Allocator,
+    session: *Session,
+    ptr: *anyopaque,
+    global: v8.Global,
+    identity: *js.Identity,
+    zig_finalizer: *const fn (ptr: *anyopaque, session: *Session) void,
+
+    pub fn deinit(self: *FinalizerCallback) void {
+        self.zig_finalizer(self.ptr, self.session);
+        self.session.releaseArena(self.arena);
+    }
+
+    /// Release this item from the identity tracking maps (called after finalizer runs from V8)
+    pub fn releaseIdentity(self: *FinalizerCallback) void {
+        const session = self.session;
+        const id = @intFromPtr(self.ptr);
+
+        if (self.identity.identity_map.fetchRemove(id)) |kv| {
+            var global = kv.value;
+            v8.v8__Global__Reset(&global);
+        }
+
+        _ = self.identity.finalizer_callbacks.remove(id);
+
+        session.releaseArena(self.arena);
+    }
+};

src/browser/js/Context.zig

@@ -63,7 +63,9 @@ templates: []*const v8.FunctionTemplate,
 // Arena for the lifetime of the context
 arena: Allocator,
 
-// The page.call_arena
+// The call_arena for this context. For main world contexts this is
+// page.call_arena. For isolated world contexts this is a separate arena
+// owned by the IsolatedWorld.
 call_arena: Allocator,
 
 // Because calls can be nested (i.e.a function calling a callback),
@@ -79,6 +81,16 @@ local: ?*const js.Local = null,
 
 origin: *Origin,
 
+// Identity tracking for this context. For main world contexts, this points to
+// Session's Identity. For isolated world contexts (CDP inspector), this points
+// to IsolatedWorld's Identity. This ensures same-origin frames share object
+// identity while isolated worlds have separate identity tracking.
+identity: *js.Identity,
+
+// Allocator to use for identity map operations. For main world contexts this is
+// session.page_arena, for isolated worlds it's the isolated world's arena.
+identity_arena: Allocator,
+
 // Unlike other v8 types, like functions or objects, modules are not shared
 // across origins.
 global_modules: std.ArrayList(v8.Global) = .empty,
@@ -185,9 +197,8 @@ pub fn setOrigin(self: *Context, key: ?[]const u8) !void {
     lp.assert(self.origin.rc == 1, "Ref opaque origin", .{ .rc = self.origin.rc });
 
     const origin = try self.session.getOrCreateOrigin(key);
-    errdefer self.session.releaseOrigin(origin);
-    try origin.takeover(self.origin);
 
+    self.session.releaseOrigin(self.origin);
     self.origin = origin;
 
     {
@@ -203,16 +214,16 @@ pub fn setOrigin(self: *Context, key: ?[]const u8) !void {
 }
 
 pub fn trackGlobal(self: *Context, global: v8.Global) !void {
-    return self.origin.trackGlobal(global);
+    return self.identity.globals.append(self.identity_arena, global);
 }
 
 pub fn trackTemp(self: *Context, global: v8.Global) !void {
-    return self.origin.trackTemp(global);
+    return self.identity.temps.put(self.identity_arena, global.data_ptr, global);
 }
 
 pub fn weakRef(self: *Context, obj: anytype) void {
     const resolved = js.Local.resolveValue(obj);
-    const fc = self.origin.finalizer_callbacks.get(@intFromPtr(resolved.ptr)) orelse {
+    const fc = self.identity.finalizer_callbacks.get(@intFromPtr(resolved.ptr)) orelse {
         if (comptime IS_DEBUG) {
             // should not be possible
             std.debug.assert(false);
@@ -224,7 +235,7 @@ pub fn weakRef(self: *Context, obj: anytype) void {
 
 pub fn safeWeakRef(self: *Context, obj: anytype) void {
     const resolved = js.Local.resolveValue(obj);
-    const fc = self.origin.finalizer_callbacks.get(@intFromPtr(resolved.ptr)) orelse {
+    const fc = self.identity.finalizer_callbacks.get(@intFromPtr(resolved.ptr)) orelse {
         if (comptime IS_DEBUG) {
             // should not be possible
             std.debug.assert(false);
@@ -237,7 +248,7 @@ pub fn safeWeakRef(self: *Context, obj: anytype) void {
 
 pub fn strongRef(self: *Context, obj: anytype) void {
     const resolved = js.Local.resolveValue(obj);
-    const fc = self.origin.finalizer_callbacks.get(@intFromPtr(resolved.ptr)) orelse {
+    const fc = self.identity.finalizer_callbacks.get(@intFromPtr(resolved.ptr)) orelse {
         if (comptime IS_DEBUG) {
             // should not be possible
             std.debug.assert(false);
@@ -247,6 +258,48 @@ pub fn strongRef(self: *Context, obj: anytype) void {
     v8.v8__Global__ClearWeak(&fc.global);
 }
 
+pub const IdentityResult = struct {
+    value_ptr: *v8.Global,
+    found_existing: bool,
+};
+
+pub fn addIdentity(self: *Context, ptr: usize) !IdentityResult {
+    const gop = try self.identity.identity_map.getOrPut(self.identity_arena, ptr);
+    return .{
+        .value_ptr = gop.value_ptr,
+        .found_existing = gop.found_existing,
+    };
+}
+
+pub fn releaseTemp(self: *Context, global: v8.Global) void {
+    if (self.identity.temps.fetchRemove(global.data_ptr)) |kv| {
+        var g = kv.value;
+        v8.v8__Global__Reset(&g);
+    }
+}
+
+pub fn createFinalizerCallback(
+    self: *Context,
+    global: v8.Global,
+    ptr: *anyopaque,
+    zig_finalizer: *const fn (ptr: *anyopaque, session: *Session) void,
+) !*Session.FinalizerCallback {
+    const session = self.session;
+    const arena = try session.getArena(.{ .debug = "FinalizerCallback" });
+    errdefer session.releaseArena(arena);
+    const fc = try arena.create(Session.FinalizerCallback);
+    fc.* = .{
+        .arena = arena,
+        .session = session,
+        .ptr = ptr,
+        .global = global,
+        .zig_finalizer = zig_finalizer,
+        // Store identity pointer for cleanup when V8 GCs the object
+        .identity = self.identity,
+    };
+    return fc;
+}
+
 // Any operation on the context have to be made from a local.
 pub fn localScope(self: *Context, ls: *js.Local.Scope) void {
     const isolate = self.isolate;
@@ -545,13 +598,13 @@ pub fn dynamicModuleCallback(
 
         break :blk js.String.toSliceZ(.{ .local = &local, .handle = resource_name.? }) catch |err| {
             log.err(.app, "OOM", .{ .err = err, .src = "dynamicModuleCallback1" });
-            return @constCast((local.rejectPromise("Out of memory") catch return null).handle);
+            return @constCast(local.rejectPromise(.{ .generic_error = "Out of memory" }).handle);
         };
     };
 
     const specifier = js.String.toSliceZ(.{ .local = &local, .handle = v8_specifier.? }) catch |err| {
         log.err(.app, "OOM", .{ .err = err, .src = "dynamicModuleCallback2" });
-        return @constCast((local.rejectPromise("Out of memory") catch return null).handle);
+        return @constCast(local.rejectPromise(.{ .generic_error = "Out of memory" }).handle);
     };
 
     const normalized_specifier = self.script_manager.?.resolveSpecifier(
@@ -560,14 +613,14 @@ pub fn dynamicModuleCallback(
         specifier,
     ) catch |err| {
         log.err(.app, "OOM", .{ .err = err, .src = "dynamicModuleCallback3" });
-        return @constCast((local.rejectPromise("Out of memory") catch return null).handle);
+        return @constCast(local.rejectPromise(.{ .generic_error = "Out of memory" }).handle);
     };
 
     const promise = self._dynamicModuleCallback(normalized_specifier, resource, &local) catch |err| blk: {
         log.err(.js, "dynamic module callback", .{
             .err = err,
         });
-        break :blk local.rejectPromise("Failed to load module") catch return null;
+        break :blk local.rejectPromise(.{ .generic_error = "Out of memory" });
     };
     return @constCast(promise.handle);
 }

src/browser/js/Env.zig

@@ -34,6 +34,7 @@ const Snapshot = @import("Snapshot.zig");
 const Inspector = @import("Inspector.zig");
 
 const Page = @import("../Page.zig");
+const Session = @import("../Session.zig");
 const Window = @import("../webapi/Window.zig");
 
 const JsApis = bridge.JsApis;
@@ -254,8 +255,15 @@ pub fn deinit(self: *Env) void {
     allocator.destroy(self.isolate_params);
 }
 
-pub fn createContext(self: *Env, page: *Page) !*Context {
+pub const ContextParams = struct {
-    const context_arena = try self.app.arena_pool.acquire();
+    identity: *js.Identity,
+    identity_arena: Allocator,
+    call_arena: Allocator,
+    debug_name: []const u8 = "Context",
+};
+
+pub fn createContext(self: *Env, page: *Page, params: ContextParams) !*Context {
+    const context_arena = try self.app.arena_pool.acquire(.{ .debug = params.debug_name });
     errdefer self.app.arena_pool.release(context_arena);
 
     const isolate = self.isolate;
@@ -300,33 +308,43 @@ pub fn createContext(self: *Env, page: *Page) !*Context {
         v8.v8__Object__SetAlignedPointerInInternalField(global_obj, 0, tao);
     }
 
-    // our window wrapped in a v8::Global
-    var global_global: v8.Global = undefined;
-    v8.v8__Global__New(isolate.handle, global_obj, &global_global);
-
     const context_id = self.context_id;
     self.context_id = context_id + 1;
 
-    const origin = try page._session.getOrCreateOrigin(null);
+    const session = page._session;
-    errdefer page._session.releaseOrigin(origin);
+    const origin = try session.getOrCreateOrigin(null);
+    errdefer session.releaseOrigin(origin);
 
     const context = try context_arena.create(Context);
     context.* = .{
         .env = self,
         .page = page,
-        .session = page._session,
         .origin = origin,
         .id = context_id,
+        .session = session,
         .isolate = isolate,
         .arena = context_arena,
         .handle = context_global,
         .templates = self.templates,
-        .call_arena = page.call_arena,
+        .call_arena = params.call_arena,
         .microtask_queue = microtask_queue,
         .script_manager = &page._script_manager,
         .scheduler = .init(context_arena),
+        .identity = params.identity,
+        .identity_arena = params.identity_arena,
     };
-    try context.origin.identity_map.putNoClobber(origin.arena, @intFromPtr(page.window), global_global);
+
+    {
+        // Multiple contexts can be created for the same Window (via CDP). We only
+        // need to register the first one.
+        const gop = try params.identity.identity_map.getOrPut(params.identity_arena, @intFromPtr(page.window));
+        if (gop.found_existing == false) {
+            // our window wrapped in a v8::Global
+            var global_global: v8.Global = undefined;
+            v8.v8__Global__New(isolate.handle, global_obj, &global_global);
+            gop.value_ptr.* = global_global;
+        }
+    }
 
     // Store a pointer to our context inside the v8 context so that, given
     // a v8 context, we can get our context out
@@ -495,6 +513,11 @@ pub fn terminate(self: *const Env) void {
 }
 
 fn promiseRejectCallback(message_handle: v8.PromiseRejectMessage) callconv(.c) void {
+    const promise_event = v8.v8__PromiseRejectMessage__GetEvent(&message_handle);
+    if (promise_event != v8.kPromiseRejectWithNoHandler and promise_event != v8.kPromiseHandlerAddedAfterReject) {
+        return;
+    }
+
     const promise_handle = v8.v8__PromiseRejectMessage__GetPromise(&message_handle).?;
     const v8_isolate = v8.v8__Object__GetIsolate(@ptrCast(promise_handle)).?;
     const isolate = js.Isolate{ .handle = v8_isolate };
@@ -508,7 +531,7 @@ fn promiseRejectCallback(message_handle: v8.PromiseRejectMessage) callconv(.c) v
     };
 
     const page = ctx.page;
-    page.window.unhandledPromiseRejection(.{
+    page.window.unhandledPromiseRejection(promise_event == v8.kPromiseRejectWithNoHandler, .{
         .local = &local,
         .handle = &message_handle,
     }, page) catch |err| {

src/browser/js/Function.zig

@@ -21,6 +21,7 @@ const js = @import("js.zig");
 const v8 = js.v8;
 
 const log = @import("../../log.zig");
+const Session = @import("../Session.zig");
 
 const Function = @This();
 
@@ -210,10 +211,10 @@ fn _persist(self: *const Function, comptime is_global: bool) !(if (is_global) Gl
     v8.v8__Global__New(ctx.isolate.handle, self.handle, &global);
     if (comptime is_global) {
         try ctx.trackGlobal(global);
-        return .{ .handle = global, .origin = {} };
+        return .{ .handle = global, .temps = {} };
     }
     try ctx.trackTemp(global);
-    return .{ .handle = global, .origin = ctx.origin };
+    return .{ .handle = global, .temps = &ctx.identity.temps };
 }
 
 pub fn tempWithThis(self: *const Function, value: anytype) !Temp {
@@ -237,7 +238,7 @@ const GlobalType = enum(u8) {
 fn G(comptime global_type: GlobalType) type {
     return struct {
         handle: v8.Global,
-        origin: if (global_type == .temp) *js.Origin else void,
+        temps: if (global_type == .temp) *std.AutoHashMapUnmanaged(usize, v8.Global) else void,
 
         const Self = @This();
 
@@ -257,7 +258,10 @@ fn G(comptime global_type: GlobalType) type {
         }
 
         pub fn release(self: *const Self) void {
-            self.origin.releaseTemp(self.handle);
+            if (self.temps.fetchRemove(self.handle.data_ptr)) |kv| {
+                var g = kv.value;
+                v8.v8__Global__Reset(&g);
+            }
         }
     };
 }

src/browser/js/Identity.zig

@@ -0,0 +1,76 @@
+// Copyright (C) 2023-2026  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+// Identity manages the mapping between Zig instances and their v8::Object wrappers.
+// This provides object identity semantics - the same Zig instance always maps to
+// the same JS object within a given Identity scope.
+//
+// Main world contexts share a single Identity (on Session), ensuring that
+// `window.top.document === top's document` works across same-origin frames.
+//
+// Isolated worlds (CDP inspector) have their own Identity, ensuring their
+// v8::Global wrappers don't leak into the main world.
+
+const std = @import("std");
+const js = @import("js.zig");
+
+const Session = @import("../Session.zig");
+
+const v8 = js.v8;
+const Allocator = std.mem.Allocator;
+
+const Identity = @This();
+
+// Maps Zig instance pointers to their v8::Global(Object) wrappers.
+identity_map: std.AutoHashMapUnmanaged(usize, v8.Global) = .empty,
+
+// Tracked global v8 objects that need to be released on cleanup.
+globals: std.ArrayList(v8.Global) = .empty,
+
+// Temporary v8 globals that can be released early. Key is global.data_ptr.
+temps: std.AutoHashMapUnmanaged(usize, v8.Global) = .empty,
+
+// Finalizer callbacks for weak references. Key is @intFromPtr of the Zig instance.
+finalizer_callbacks: std.AutoHashMapUnmanaged(usize, *Session.FinalizerCallback) = .empty,
+
+pub fn deinit(self: *Identity) void {
+    {
+        var it = self.finalizer_callbacks.valueIterator();
+        while (it.next()) |finalizer| {
+            finalizer.*.deinit();
+        }
+    }
+
+    {
+        var it = self.identity_map.valueIterator();
+        while (it.next()) |global| {
+            v8.v8__Global__Reset(global);
+        }
+    }
+
+    for (self.globals.items) |*global| {
+        v8.v8__Global__Reset(global);
+    }
+
+    {
+        var it = self.temps.valueIterator();
+        while (it.next()) |global| {
+            v8.v8__Global__Reset(global);
+        }
+    }
+}

src/browser/js/Isolate.zig

@@ -78,6 +78,21 @@ pub fn createError(self: Isolate, msg: []const u8) *const v8.Value {
     return v8.v8__Exception__Error(message).?;
 }
 
+pub fn createRangeError(self: Isolate, msg: []const u8) *const v8.Value {
+    const message = self.initStringHandle(msg);
+    return v8.v8__Exception__RangeError(message).?;
+}
+
+pub fn createReferenceError(self: Isolate, msg: []const u8) *const v8.Value {
+    const message = self.initStringHandle(msg);
+    return v8.v8__Exception__ReferenceError(message).?;
+}
+
+pub fn createSyntaxError(self: Isolate, msg: []const u8) *const v8.Value {
+    const message = self.initStringHandle(msg);
+    return v8.v8__Exception__SyntaxError(message).?;
+}
+
 pub fn createTypeError(self: Isolate, msg: []const u8) *const v8.Value {
     const message = self.initStringHandle(msg);
     return v8.v8__Exception__TypeError(message).?;

src/browser/js/Local.zig

@@ -202,20 +202,20 @@ pub fn compileAndRun(self: *const Local, src: []const u8, name: ?[]const u8) !js
 //      we can just grab it from the identity_map)
 pub fn mapZigInstanceToJs(self: *const Local, js_obj_handle: ?*const v8.Object, value: anytype) !js.Object {
     const ctx = self.ctx;
-    const origin_arena = ctx.origin.arena;
+    const context_arena = ctx.arena;
 
     const T = @TypeOf(value);
     switch (@typeInfo(T)) {
         .@"struct" => {
             // Struct, has to be placed on the heap
-            const heap = try origin_arena.create(T);
+            const heap = try context_arena.create(T);
             heap.* = value;
             return self.mapZigInstanceToJs(js_obj_handle, heap);
         },
         .pointer => |ptr| {
             const resolved = resolveValue(value);
 
-            const gop = try ctx.origin.addIdentity(@intFromPtr(resolved.ptr));
+            const gop = try ctx.addIdentity(@intFromPtr(resolved.ptr));
             if (gop.found_existing) {
                 // we've seen this instance before, return the same object
                 return (js.Object.Global{ .handle = gop.value_ptr.* }).local(self);
@@ -244,7 +244,7 @@ pub fn mapZigInstanceToJs(self: *const Local, js_obj_handle: ?*const v8.Object,
                 // The TAO contains the pointer to our Zig instance as
                 // well as any meta data we'll need to use it later.
                 // See the TaggedOpaque struct for more details.
-                const tao = try origin_arena.create(TaggedOpaque);
+                const tao = try context_arena.create(TaggedOpaque);
                 tao.* = .{
                     .value = resolved.ptr,
                     .prototype_chain = resolved.prototype_chain.ptr,
@@ -276,10 +276,10 @@ pub fn mapZigInstanceToJs(self: *const Local, js_obj_handle: ?*const v8.Object,
                 // Instead, we check if the base has finalizer. The assumption
                 // here is that if a resolve type has a finalizer, then the base
                 // should have a finalizer too.
-                const fc = try ctx.origin.createFinalizerCallback(ctx.session, gop.value_ptr.*, resolved.ptr, resolved.finalizer_from_zig.?);
+                const fc = try ctx.createFinalizerCallback(gop.value_ptr.*, resolved.ptr, resolved.finalizer_from_zig.?);
                 {
                     errdefer fc.deinit();
-                    try ctx.origin.finalizer_callbacks.put(ctx.origin.arena, @intFromPtr(resolved.ptr), fc);
+                    try ctx.identity.finalizer_callbacks.put(ctx.identity_arena, @intFromPtr(resolved.ptr), fc);
                 }
 
                 conditionallyReference(value);
@@ -1206,9 +1206,9 @@ pub fn stackTrace(self: *const Local) !?[]const u8 {
 }
 
 // == Promise Helpers ==
-pub fn rejectPromise(self: *const Local, value: anytype) !js.Promise {
+pub fn rejectPromise(self: *const Local, err: js.PromiseResolver.RejectError) js.Promise {
     var resolver = js.PromiseResolver.init(self);
-    resolver.reject("Local.rejectPromise", value);
+    resolver.rejectError("Local.rejectPromise", err);
     return resolver.promise();
 }
 

src/browser/js/Origin.zig

@@ -16,19 +16,21 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-// Origin represents the shared Zig<->JS bridge state for all contexts within
+// Origin represents the security token for contexts within the same origin.
-// the same origin. Multiple contexts (frames) from the same origin share a
+// Multiple contexts (frames) from the same origin share a single Origin,
-// single Origin, ensuring that JS objects maintain their identity across frames.
+// which provides the V8 SecurityToken that allows cross-context access.
+//
+// Note: Identity tracking (mapping Zig instances to v8::Objects) is managed
+// separately via js.Identity - Session has the main world Identity, and
+// IsolatedWorlds have their own Identity instances.
 
 const std = @import("std");
 const js = @import("js.zig");
 
 const App = @import("../../App.zig");
-const Session = @import("../Session.zig");
 
 const v8 = js.v8;
 const Allocator = std.mem.Allocator;
-const IS_DEBUG = @import("builtin").mode == .Debug;
 
 const Origin = @This();
 
@@ -38,40 +40,12 @@ arena: Allocator,
 // The key, e.g. lightpanda.io:443
 key: []const u8,
 
-// Security token - all contexts in this realm must use the same v8::Value instance
+// Security token - all contexts in this origin must use the same v8::Value instance
 // as their security token for V8 to allow cross-context access
 security_token: v8.Global,
 
-// Serves two purposes. Like `global_objects`, this is used to free
-// every Global(Object) we've created during the lifetime of the realm.
-// More importantly, it serves as an identity map - for a given Zig
-// instance, we map it to the same Global(Object).
-// The key is the @intFromPtr of the Zig value
-identity_map: std.AutoHashMapUnmanaged(usize, v8.Global) = .empty,
-
-// Some web APIs have to manage opaque values. Ideally, they use an
-// js.Object, but the js.Object has no lifetime guarantee beyond the
-// current call. They can call .persist() on their js.Object to get
-// a `Global(Object)`. We need to track these to free them.
-// This used to be a map and acted like identity_map; the key was
-// the @intFromPtr(js_obj.handle). But v8 can re-use address. Without
-// a reliable way to know if an object has already been persisted,
-// we now simply persist every time persist() is called.
-globals: std.ArrayList(v8.Global) = .empty,
-
-// Temp variants stored in HashMaps for O(1) early cleanup.
-// Key is global.data_ptr.
-temps: std.AutoHashMapUnmanaged(usize, v8.Global) = .empty,
-
-// Any type that is stored in the identity_map which has a finalizer declared
-// will have its finalizer stored here. This is only used when shutting down
-// if v8 hasn't called the finalizer directly itself.
-finalizer_callbacks: std.AutoHashMapUnmanaged(usize, *FinalizerCallback) = .empty,
-
-taken_over: std.ArrayList(*Origin),
-
 pub fn init(app: *App, isolate: js.Isolate, key: []const u8) !*Origin {
-    const arena = try app.arena_pool.acquire();
+    const arena = try app.arena_pool.acquire(.{ .debug = "Origin" });
     errdefer app.arena_pool.release(arena);
 
     var hs: js.HandleScope = undefined;
@@ -88,175 +62,12 @@ pub fn init(app: *App, isolate: js.Isolate, key: []const u8) !*Origin {
         .rc = 1,
         .arena = arena,
         .key = owned_key,
-        .temps = .empty,
-        .globals = .empty,
-        .taken_over = .empty,
         .security_token = token_global,
     };
     return self;
 }
 
 pub fn deinit(self: *Origin, app: *App) void {
-    for (self.taken_over.items) |o| {
-        o.deinit(app);
-    }
-
-    // Call finalizers before releasing anything
-    {
-        var it = self.finalizer_callbacks.valueIterator();
-        while (it.next()) |finalizer| {
-            finalizer.*.deinit();
-        }
-    }
-
     v8.v8__Global__Reset(&self.security_token);
-
-    {
-        var it = self.identity_map.valueIterator();
-        while (it.next()) |global| {
-            v8.v8__Global__Reset(global);
-        }
-    }
-
-    for (self.globals.items) |*global| {
-        v8.v8__Global__Reset(global);
-    }
-
-    {
-        var it = self.temps.valueIterator();
-        while (it.next()) |global| {
-            v8.v8__Global__Reset(global);
-        }
-    }
-
     app.arena_pool.release(self.arena);
 }
-
-pub fn trackGlobal(self: *Origin, global: v8.Global) !void {
-    return self.globals.append(self.arena, global);
-}
-
-pub const IdentityResult = struct {
-    value_ptr: *v8.Global,
-    found_existing: bool,
-};
-
-pub fn addIdentity(self: *Origin, ptr: usize) !IdentityResult {
-    const gop = try self.identity_map.getOrPut(self.arena, ptr);
-    return .{
-        .value_ptr = gop.value_ptr,
-        .found_existing = gop.found_existing,
-    };
-}
-
-pub fn trackTemp(self: *Origin, global: v8.Global) !void {
-    return self.temps.put(self.arena, global.data_ptr, global);
-}
-
-pub fn releaseTemp(self: *Origin, global: v8.Global) void {
-    if (self.temps.fetchRemove(global.data_ptr)) |kv| {
-        var g = kv.value;
-        v8.v8__Global__Reset(&g);
-    }
-}
-
-/// Release an item from the identity_map (called after finalizer runs from V8)
-pub fn release(self: *Origin, item: *anyopaque) void {
-    var global = self.identity_map.fetchRemove(@intFromPtr(item)) orelse {
-        if (comptime IS_DEBUG) {
-            std.debug.assert(false);
-        }
-        return;
-    };
-    v8.v8__Global__Reset(&global.value);
-
-    // The item has been finalized, remove it from the finalizer callback so that
-    // we don't try to call it again on shutdown.
-    const kv = self.finalizer_callbacks.fetchRemove(@intFromPtr(item)) orelse {
-        if (comptime IS_DEBUG) {
-            std.debug.assert(false);
-        }
-        return;
-    };
-    const fc = kv.value;
-    fc.session.releaseArena(fc.arena);
-}
-
-pub fn createFinalizerCallback(
-    self: *Origin,
-    session: *Session,
-    global: v8.Global,
-    ptr: *anyopaque,
-    zig_finalizer: *const fn (ptr: *anyopaque, session: *Session) void,
-) !*FinalizerCallback {
-    const arena = try session.getArena(.{ .debug = "FinalizerCallback" });
-    errdefer session.releaseArena(arena);
-    const fc = try arena.create(FinalizerCallback);
-    fc.* = .{
-        .arena = arena,
-        .origin = self,
-        .session = session,
-        .ptr = ptr,
-        .global = global,
-        .zig_finalizer = zig_finalizer,
-    };
-    return fc;
-}
-
-pub fn takeover(self: *Origin, original: *Origin) !void {
-    const arena = self.arena;
-
-    try self.globals.ensureUnusedCapacity(arena, original.globals.items.len);
-    for (original.globals.items) |obj| {
-        self.globals.appendAssumeCapacity(obj);
-    }
-    original.globals.clearRetainingCapacity();
-
-    {
-        try self.temps.ensureUnusedCapacity(arena, original.temps.count());
-        var it = original.temps.iterator();
-        while (it.next()) |kv| {
-            try self.temps.put(arena, kv.key_ptr.*, kv.value_ptr.*);
-        }
-        original.temps.clearRetainingCapacity();
-    }
-
-    {
-        try self.finalizer_callbacks.ensureUnusedCapacity(arena, original.finalizer_callbacks.count());
-        var it = original.finalizer_callbacks.iterator();
-        while (it.next()) |kv| {
-            kv.value_ptr.*.origin = self;
-            try self.finalizer_callbacks.put(arena, kv.key_ptr.*, kv.value_ptr.*);
-        }
-        original.finalizer_callbacks.clearRetainingCapacity();
-    }
-
-    {
-        try self.identity_map.ensureUnusedCapacity(arena, original.identity_map.count());
-        var it = original.identity_map.iterator();
-        while (it.next()) |kv| {
-            try self.identity_map.put(arena, kv.key_ptr.*, kv.value_ptr.*);
-        }
-        original.identity_map.clearRetainingCapacity();
-    }
-
-    try self.taken_over.append(self.arena, original);
-}
-
-// A type that has a finalizer can have its finalizer called one of two ways.
-// The first is from V8 via the WeakCallback we give to weakRef. But that isn't
-// guaranteed to fire, so we track this in finalizer_callbacks and call them on
-// origin shutdown.
-pub const FinalizerCallback = struct {
-    arena: Allocator,
-    origin: *Origin,
-    session: *Session,
-    ptr: *anyopaque,
-    global: v8.Global,
-    zig_finalizer: *const fn (ptr: *anyopaque, session: *Session) void,
-
-    pub fn deinit(self: *FinalizerCallback) void {
-        self.zig_finalizer(self.ptr, self.session);
-        self.session.releaseArena(self.arena);
-    }
-};

src/browser/js/Promise.zig

@@ -16,9 +16,12 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+const std = @import("std");
 const js = @import("js.zig");
 const v8 = js.v8;
 
+const Session = @import("../Session.zig");
+
 const Promise = @This();
 
 local: *const js.Local,
@@ -63,10 +66,10 @@ fn _persist(self: *const Promise, comptime is_global: bool) !(if (is_global) Glo
     v8.v8__Global__New(ctx.isolate.handle, self.handle, &global);
     if (comptime is_global) {
         try ctx.trackGlobal(global);
-        return .{ .handle = global, .origin = {} };
+        return .{ .handle = global, .temps = {} };
     }
     try ctx.trackTemp(global);
-    return .{ .handle = global, .origin = ctx.origin };
+    return .{ .handle = global, .temps = &ctx.identity.temps };
 }
 
 pub const Temp = G(.temp);
@@ -80,7 +83,7 @@ const GlobalType = enum(u8) {
 fn G(comptime global_type: GlobalType) type {
     return struct {
         handle: v8.Global,
-        origin: if (global_type == .temp) *js.Origin else void,
+        temps: if (global_type == .temp) *std.AutoHashMapUnmanaged(usize, v8.Global) else void,
 
         const Self = @This();
 
@@ -96,7 +99,10 @@ fn G(comptime global_type: GlobalType) type {
         }
 
         pub fn release(self: *const Self) void {
-            self.origin.releaseTemp(self.handle);
+            if (self.temps.fetchRemove(self.handle.data_ptr)) |kv| {
+                var g = kv.value;
+                v8.v8__Global__Reset(&g);
+            }
         }
     };
 }

src/browser/js/PromiseResolver.zig

@@ -20,6 +20,7 @@ const js = @import("js.zig");
 const v8 = js.v8;
 
 const log = @import("../../log.zig");
+
 const DOMException = @import("../webapi/DOMException.zig");
 
 const PromiseResolver = @This();
@@ -66,19 +67,37 @@ pub fn reject(self: PromiseResolver, comptime source: []const u8, value: anytype
 }
 
 pub const RejectError = union(enum) {
-    generic: []const u8,
+    /// Not to be confused with `DOMException`; this is bare `Error`.
+    generic_error: []const u8,
+    range_error: []const u8,
+    reference_error: []const u8,
+    syntax_error: []const u8,
     type_error: []const u8,
-    dom_exception: anyerror,
+    /// DOM exceptions are unknown to V8, belongs to web standards.
+    dom_exception: struct { err: anyerror },
 };
-pub fn rejectError(self: PromiseResolver, comptime source: []const u8, err: RejectError) void {
+
+/// Rejects the promise w/ an error object.
+pub fn rejectError(
+    self: PromiseResolver,
+    comptime source: []const u8,
+    err: RejectError,
+) void {
     const handle = switch (err) {
-        .type_error => |str| self.local.isolate.createTypeError(str),
+        .generic_error => |msg| self.local.isolate.createError(msg),
-        .generic => |str| self.local.isolate.createError(str),
+        .range_error => |msg| self.local.isolate.createRangeError(msg),
+        .reference_error => |msg| self.local.isolate.createReferenceError(msg),
+        .syntax_error => |msg| self.local.isolate.createSyntaxError(msg),
+        .type_error => |msg| self.local.isolate.createTypeError(msg),
+        // "Exceptional".
         .dom_exception => |exception| {
-            self.reject(source, DOMException.fromError(exception));
+            self._reject(DOMException.fromError(exception.err) orelse unreachable) catch |reject_err| {
+                log.err(.bug, "rejectDomException", .{ .source = source, .err = reject_err, .persistent = false });
+            };
             return;
         },
     };
+
     self._reject(js.Value{ .handle = handle, .local = self.local }) catch |reject_err| {
         log.err(.bug, "rejectError", .{ .source = source, .err = reject_err, .persistent = false });
     };

src/browser/js/String.zig

@@ -56,7 +56,7 @@ fn _toSlice(self: String, comptime null_terminate: bool, allocator: Allocator) !
 
 pub fn toSSO(self: String, comptime global: bool) !(if (global) SSO.Global else SSO) {
     if (comptime global) {
-        return .{ .str = try self.toSSOWithAlloc(self.local.ctx.origin.arena) };
+        return .{ .str = try self.toSSOWithAlloc(self.local.ctx.session.page_arena) };
     }
     return self.toSSOWithAlloc(self.local.call_arena);
 }

src/browser/js/Value.zig

@@ -25,6 +25,7 @@ const v8 = js.v8;
 const IS_DEBUG = @import("builtin").mode == .Debug;
 
 const Allocator = std.mem.Allocator;
+const Session = @import("../Session.zig");
 
 const Value = @This();
 
@@ -300,10 +301,10 @@ fn _persist(self: *const Value, comptime is_global: bool) !(if (is_global) Globa
     v8.v8__Global__New(ctx.isolate.handle, self.handle, &global);
     if (comptime is_global) {
         try ctx.trackGlobal(global);
-        return .{ .handle = global, .origin = {} };
+        return .{ .handle = global, .temps = {} };
     }
     try ctx.trackTemp(global);
-    return .{ .handle = global, .origin = ctx.origin };
+    return .{ .handle = global, .temps = &ctx.identity.temps };
 }
 
 pub fn toZig(self: Value, comptime T: type) !T {
@@ -361,7 +362,7 @@ const GlobalType = enum(u8) {
 fn G(comptime global_type: GlobalType) type {
     return struct {
         handle: v8.Global,
-        origin: if (global_type == .temp) *js.Origin else void,
+        temps: if (global_type == .temp) *std.AutoHashMapUnmanaged(usize, v8.Global) else void,
 
         const Self = @This();
 
@@ -381,7 +382,10 @@ fn G(comptime global_type: GlobalType) type {
         }
 
         pub fn release(self: *const Self) void {
-            self.origin.releaseTemp(self.handle);
+            if (self.temps.fetchRemove(self.handle.data_ptr)) |kv| {
+                var g = kv.value;
+                v8.v8__Global__Reset(&g);
+            }
         }
     };
 }

src/browser/js/bridge.zig

@@ -27,7 +27,6 @@ const v8 = js.v8;
 
 const Caller = @import("Caller.zig");
 const Context = @import("Context.zig");
-const Origin = @import("Origin.zig");
 
 const IS_DEBUG = @import("builtin").mode == .Debug;
 
@@ -117,13 +116,12 @@ pub fn Builder(comptime T: type) type {
                 .from_v8 = struct {
                     fn wrap(handle: ?*const v8.WeakCallbackInfo) callconv(.c) void {
                         const ptr = v8.v8__WeakCallbackInfo__GetParameter(handle.?).?;
-                        const fc: *Origin.FinalizerCallback = @ptrCast(@alignCast(ptr));
+                        const fc: *Session.FinalizerCallback = @ptrCast(@alignCast(ptr));
 
-                        const origin = fc.origin;
                         const value_ptr = fc.ptr;
-                        if (origin.finalizer_callbacks.contains(@intFromPtr(value_ptr))) {
+                        if (fc.identity.finalizer_callbacks.contains(@intFromPtr(value_ptr))) {
                             func(@ptrCast(@alignCast(value_ptr)), false, fc.session);
-                            origin.release(value_ptr);
+                            fc.releaseIdentity();
                         } else {
                             // A bit weird, but v8 _requires_ that we release it
                             // If we don't. We'll 100% crash.

src/browser/js/js.zig

@@ -25,6 +25,7 @@ pub const Env = @import("Env.zig");
 pub const bridge = @import("bridge.zig");
 pub const Caller = @import("Caller.zig");
 pub const Origin = @import("Origin.zig");
+pub const Identity = @import("Identity.zig");
 pub const Context = @import("Context.zig");
 pub const Local = @import("Local.zig");
 pub const Inspector = @import("Inspector.zig");

src/browser/tests/shadowroot/basic.html

@@ -5,7 +5,7 @@
 <div id="host2"></div>
 <div id="host3"></div>
 
-<!-- <script id="attachShadow_open">
+<script id="attachShadow_open">
 {
     const host = $('#host1');
     const shadow = host.attachShadow({ mode: 'open' });
@@ -140,7 +140,7 @@
     shadow.replaceChildren('New content');
     testing.expectEqual('New content', shadow.innerHTML);
 }
-</script> -->
+</script>
 
 <script id="getElementById">
 {
@@ -154,3 +154,16 @@
     testing.expectEqual(null, shadow.getElementById('nonexistent'));
 }
 </script>
+
+
+<script id=adoptedStyleSheets>
+  {
+    const host = document.createElement('div');
+    const shadow = host.attachShadow({ mode: 'open' });
+
+    const acss = shadow.adoptedStyleSheets;
+    testing.expectEqual(0, acss.length);
+    acss.push(new CSSStyleSheet());
+    testing.expectEqual(1, acss.length);
+  }
+</script>

src/browser/webapi/CustomElementRegistry.zig

@@ -125,8 +125,8 @@ pub fn whenDefined(self: *CustomElementRegistry, name: []const u8, page: *Page)
         return local.resolvePromise(definition.constructor);
     }
 
-    validateName(name) catch |err| {
+    validateName(name) catch |err| switch (err) {
-        return local.rejectPromise(DOMException.fromError(err) orelse unreachable);
+        error.SyntaxError => return local.rejectPromise(.{ .dom_exception = .{ .err = error.SyntaxError } }),
     };
 
     const gop = try self._when_defined.getOrPut(page.arena, name);

src/browser/webapi/IntersectionObserver.zig

@@ -93,12 +93,12 @@ pub fn init(callback: js.Function.Temp, options: ?ObserverInit, page: *Page) !*I
 }
 
 pub fn deinit(self: *IntersectionObserver, shutdown: bool, session: *Session) void {
-    if (shutdown) {
+    self._callback.release();
-        self._callback.release();
+    if ((comptime IS_DEBUG) and !shutdown) {
-        session.releaseArena(self._arena);
+        std.debug.assert(self._observing.items.len == 0);
-    } else if (comptime IS_DEBUG) {
-        std.debug.assert(false);
     }
+
+    session.releaseArena(self._arena);
 }
 
 pub fn observe(self: *IntersectionObserver, target: *Element, page: *Page) !void {
@@ -111,6 +111,7 @@ pub fn observe(self: *IntersectionObserver, target: *Element, page: *Page) !void
 
     // Register with page if this is our first observation
     if (self._observing.items.len == 0) {
+        page.js.strongRef(self);
         try page.registerIntersectionObserver(self);
     }
 
@@ -145,18 +146,22 @@ pub fn unobserve(self: *IntersectionObserver, target: *Element, page: *Page) voi
             break;
         }
     }
+
+    if (self._observing.items.len == 0) {
+        page.js.safeWeakRef(self);
+    }
 }
 
 pub fn disconnect(self: *IntersectionObserver, page: *Page) void {
+    page.unregisterIntersectionObserver(self);
+    self._observing.clearRetainingCapacity();
     self._previous_states.clearRetainingCapacity();
 
     for (self._pending_entries.items) |entry| {
         entry.deinit(false, page._session);
     }
     self._pending_entries.clearRetainingCapacity();
-
+    page.js.safeWeakRef(self);
-    self._observing.clearRetainingCapacity();
-    page.unregisterIntersectionObserver(self);
 }
 
 pub fn takeRecords(self: *IntersectionObserver, page: *Page) ![]*IntersectionObserverEntry {
@@ -358,6 +363,7 @@ pub const JsApi = struct {
         pub const name = "IntersectionObserver";
         pub const prototype_chain = bridge.prototypeChain();
         pub var class_id: bridge.ClassId = undefined;
+        pub const weak = true;
         pub const finalizer = bridge.finalizer(IntersectionObserver.deinit);
     };
 

src/browser/webapi/MutationObserver.zig

@@ -86,12 +86,12 @@ pub fn init(callback: js.Function.Temp, page: *Page) !*MutationObserver {
 }
 
 pub fn deinit(self: *MutationObserver, shutdown: bool, session: *Session) void {
-    if (shutdown) {
+    self._callback.release();
-        self._callback.release();
+    if ((comptime IS_DEBUG) and !shutdown) {
-        session.releaseArena(self._arena);
+        std.debug.assert(self._observing.items.len == 0);
-    } else if (comptime IS_DEBUG) {
-        std.debug.assert(false);
     }
+
+    session.releaseArena(self._arena);
 }
 
 pub fn observe(self: *MutationObserver, target: *Node, options: ObserveOptions, page: *Page) !void {
@@ -158,6 +158,7 @@ pub fn observe(self: *MutationObserver, target: *Node, options: ObserveOptions,
 
     // Register with page if this is our first observation
     if (self._observing.items.len == 0) {
+        page.js.strongRef(self);
         try page.registerMutationObserver(self);
     }
 
@@ -168,13 +169,13 @@ pub fn observe(self: *MutationObserver, target: *Node, options: ObserveOptions,
 }
 
 pub fn disconnect(self: *MutationObserver, page: *Page) void {
+    page.unregisterMutationObserver(self);
+    self._observing.clearRetainingCapacity();
     for (self._pending_records.items) |record| {
         record.deinit(false, page._session);
     }
     self._pending_records.clearRetainingCapacity();
-
+    page.js.safeWeakRef(self);
-    self._observing.clearRetainingCapacity();
-    page.unregisterMutationObserver(self);
 }
 
 pub fn takeRecords(self: *MutationObserver, page: *Page) ![]*MutationRecord {
@@ -440,6 +441,7 @@ pub const JsApi = struct {
         pub const name = "MutationObserver";
         pub const prototype_chain = bridge.prototypeChain();
         pub var class_id: bridge.ClassId = undefined;
+        pub const weak = true;
         pub const finalizer = bridge.finalizer(MutationObserver.deinit);
     };
 

src/browser/webapi/Navigator.zig

@@ -73,7 +73,7 @@ pub fn getStorage(self: *Navigator) *StorageManager {
 
 pub fn getBattery(_: *const Navigator, page: *Page) !js.Promise {
     log.info(.not_implemented, "navigator.getBattery", .{});
-    return page.js.local.?.rejectErrorPromise(.{ .dom_exception = error.NotSupported });
+    return page.js.local.?.rejectErrorPromise(.{ .dom_exception = .{ .err = error.NotSupported } });
 }
 
 pub fn registerProtocolHandler(_: *const Navigator, scheme: []const u8, url: [:0]const u8, page: *const Page) !void {

src/browser/webapi/ShadowRoot.zig

@@ -40,6 +40,7 @@ _mode: Mode,
 _host: *Element,
 _elements_by_id: std.StringHashMapUnmanaged(*Element) = .{},
 _removed_ids: std.StringHashMapUnmanaged(void) = .{},
+_adopted_style_sheets: ?js.Object.Global = null,
 
 pub fn init(host: *Element, mode: Mode, page: *Page) !*ShadowRoot {
     return page._factory.documentFragment(ShadowRoot{
@@ -99,6 +100,20 @@ pub fn getElementById(self: *ShadowRoot, id: []const u8, page: *Page) ?*Element
     return null;
 }
 
+pub fn getAdoptedStyleSheets(self: *ShadowRoot, page: *Page) !js.Object.Global {
+    if (self._adopted_style_sheets) |ass| {
+        return ass;
+    }
+    const js_arr = page.js.local.?.newArray(0);
+    const js_obj = js_arr.toObject();
+    self._adopted_style_sheets = try js_obj.persist();
+    return self._adopted_style_sheets.?;
+}
+
+pub fn setAdoptedStyleSheets(self: *ShadowRoot, sheets: js.Object) !void {
+    self._adopted_style_sheets = try sheets.persist();
+}
+
 pub const JsApi = struct {
     pub const bridge = js.Bridge(ShadowRoot);
 
@@ -121,6 +136,7 @@ pub const JsApi = struct {
         }
         return self.getElementById(try value.toZig([]const u8), page);
     }
+    pub const adoptedStyleSheets = bridge.accessor(ShadowRoot.getAdoptedStyleSheets, ShadowRoot.setAdoptedStyleSheets, .{});
 };
 
 const testing = @import("../../testing.zig");

src/browser/webapi/SubtleCrypto.zig

@@ -96,8 +96,8 @@ pub fn generateKey(
     key_usages: []const []const u8,
     page: *Page,
 ) !js.Promise {
-    const key_or_pair = CryptoKey.init(algorithm, extractable, key_usages, page) catch |err| {
+    const key_or_pair = CryptoKey.init(algorithm, extractable, key_usages, page) catch {
-        return page.js.local.?.rejectPromise(@errorName(err));
+        return page.js.local.?.rejectPromise(.{ .dom_exception = .{ .err = error.SyntaxError } });
     };
 
     return page.js.local.?.resolvePromise(key_or_pair);
@@ -112,7 +112,7 @@ pub fn exportKey(
     page: *Page,
 ) !js.Promise {
     if (!key.canExportKey()) {
-        return error.InvalidAccessError;
+        return page.js.local.?.rejectPromise(.{ .dom_exception = .{ .err = error.InvalidAccessError } });
     }
 
     if (std.mem.eql(u8, format, "raw")) {
@@ -124,9 +124,10 @@ pub fn exportKey(
 
     if (is_unsupported) {
         log.warn(.not_implemented, "SubtleCrypto.exportKey", .{ .format = format });
+        return page.js.local.?.rejectPromise(.{ .dom_exception = .{ .err = error.NotSupported } });
     }
 
-    return page.js.local.?.rejectPromise(@errorName(error.NotSupported));
+    return page.js.local.?.rejectPromise(.{ .type_error = "invalid format" });
 }
 
 /// Derive a secret key from a master key.
@@ -148,7 +149,7 @@ pub fn deriveBits(
                 log.warn(.not_implemented, "SubtleCrypto.deriveBits", .{ .name = name });
             }
 
-            return page.js.local.?.rejectPromise(@errorName(error.NotSupported));
+            return page.js.local.?.rejectPromise(.{ .dom_exception = .{ .err = error.NotSupported } });
         },
     };
 }
@@ -185,19 +186,19 @@ pub fn sign(
         .hmac => {
             // Verify algorithm.
             if (!algorithm.isHMAC()) {
-                return page.js.local.?.rejectPromise(@errorName(error.InvalidAccessError));
+                return page.js.local.?.rejectPromise(.{ .dom_exception = .{ .err = error.InvalidAccessError } });
             }
 
             // Call sign for HMAC.
-            const result = key.signHMAC(data, page) catch |err| {
+            const result = key.signHMAC(data, page) catch {
-                return page.js.local.?.rejectPromise(@errorName(err));
+                return page.js.local.?.rejectPromise(.{ .dom_exception = .{ .err = error.InvalidAccessError } });
             };
 
             return page.js.local.?.resolvePromise(result);
         },
         else => {
             log.warn(.not_implemented, "SubtleCrypto.sign", .{ .key_type = key._type });
-            return page.js.local.?.rejectPromise(@errorName(error.InvalidAccessError));
+            return page.js.local.?.rejectPromise(.{ .dom_exception = .{ .err = error.InvalidAccessError } });
         },
     };
 }
@@ -211,18 +212,20 @@ pub fn verify(
     data: []const u8, // ArrayBuffer.
     page: *Page,
 ) !js.Promise {
-    if (!algorithm.isHMAC()) return error.InvalidAccessError;
+    if (!algorithm.isHMAC()) {
+        return page.js.local.?.rejectPromise(.{ .dom_exception = .{ .err = error.InvalidAccessError } });
+    }
 
     return switch (key._type) {
         .hmac => key.verifyHMAC(signature, data, page),
-        else => return error.InvalidAccessError,
+        else => page.js.local.?.rejectPromise(.{ .dom_exception = .{ .err = error.InvalidAccessError } }),
     };
 }
 
 pub fn digest(_: *const SubtleCrypto, algorithm: []const u8, data: js.TypedArray(u8), page: *Page) !js.Promise {
     const local = page.js.local.?;
     if (algorithm.len > 10) {
-        return local.rejectPromise(DOMException.fromError(error.NotSupported));
+        return local.rejectPromise(.{ .dom_exception = .{ .err = error.NotSupported } });
     }
     const normalized = std.ascii.lowerString(&page.buf, algorithm);
     if (std.mem.eql(u8, normalized, "sha-1")) {
@@ -245,7 +248,7 @@ pub fn digest(_: *const SubtleCrypto, algorithm: []const u8, data: js.TypedArray
         Sha512.hash(data.values, page.buf[0..Sha512.digest_length], .{});
         return local.resolvePromise(js.ArrayBuffer{ .values = page.buf[0..Sha512.digest_length] });
     }
-    return local.rejectPromise(DOMException.fromError(error.NotSupported));
+    return local.rejectPromise(.{ .dom_exception = .{ .err = error.NotSupported } });
 }
 
 /// Returns the desired digest by its name.

src/browser/webapi/Window.zig

@@ -67,7 +67,8 @@ _on_pageshow: ?js.Function.Global = null,
 _on_popstate: ?js.Function.Global = null,
 _on_error: ?js.Function.Global = null,
 _on_message: ?js.Function.Global = null,
-_on_unhandled_rejection: ?js.Function.Global = null, // TODO: invoke on error
+_on_rejection_handled: ?js.Function.Global = null,
+_on_unhandled_rejection: ?js.Function.Global = null,
 _current_event: ?*Event = null,
 _location: *Location,
 _timer_id: u30 = 0,
@@ -222,6 +223,14 @@ pub fn setOnMessage(self: *Window, setter: ?FunctionSetter) void {
     self._on_message = getFunctionFromSetter(setter);
 }
 
+pub fn getOnRejectionHandled(self: *const Window) ?js.Function.Global {
+    return self._on_rejection_handled;
+}
+
+pub fn setOnRejectionHandled(self: *Window, setter: ?FunctionSetter) void {
+    self._on_rejection_handled = getFunctionFromSetter(setter);
+}
+
 pub fn getOnUnhandledRejection(self: *const Window) ?js.Function.Global {
     return self._on_unhandled_rejection;
 }
@@ -572,7 +581,7 @@ pub fn scrollBy(self: *Window, opts: ScrollToOpts, y: ?i32, page: *Page) !void {
     return self.scrollTo(.{ .x = absx }, absy, page);
 }
 
-pub fn unhandledPromiseRejection(self: *Window, rejection: js.PromiseRejection, page: *Page) !void {
+pub fn unhandledPromiseRejection(self: *Window, no_handler: bool, rejection: js.PromiseRejection, page: *Page) !void {
     if (comptime IS_DEBUG) {
         log.debug(.js, "unhandled rejection", .{
             .value = rejection.reason(),
@@ -580,13 +589,20 @@ pub fn unhandledPromiseRejection(self: *Window, rejection: js.PromiseRejection,
         });
     }
 
+    const event_name, const attribute_callback = blk: {
+        if (no_handler) {
+            break :blk .{ "unhandledrejection", self._on_unhandled_rejection };
+        }
+        break :blk .{ "rejectionhandled", self._on_rejection_handled };
+    };
+
     const target = self.asEventTarget();
-    if (page._event_manager.hasDirectListeners(target, "unhandledrejection", self._on_unhandled_rejection)) {
+    if (page._event_manager.hasDirectListeners(target, event_name, attribute_callback)) {
-        const event = (try @import("event/PromiseRejectionEvent.zig").init("unhandledrejection", .{
+        const event = (try @import("event/PromiseRejectionEvent.zig").init(event_name, .{
             .reason = if (rejection.reason()) |r| try r.temp() else null,
             .promise = try rejection.promise().temp(),
         }, page)).asEvent();
-        try page._event_manager.dispatchDirect(target, event, self._on_unhandled_rejection, .{ .context = "window.unhandledrejection" });
+        try page._event_manager.dispatchDirect(target, event, attribute_callback, .{ .context = "window.unhandledrejection" });
     }
 }
 
@@ -813,6 +829,7 @@ pub const JsApi = struct {
     pub const onpopstate = bridge.accessor(Window.getOnPopState, Window.setOnPopState, .{});
     pub const onerror = bridge.accessor(Window.getOnError, Window.setOnError, .{});
     pub const onmessage = bridge.accessor(Window.getOnMessage, Window.setOnMessage, .{});
+    pub const onrejectionhandled = bridge.accessor(Window.getOnRejectionHandled, Window.setOnRejectionHandled, .{});
     pub const onunhandledrejection = bridge.accessor(Window.getOnUnhandledRejection, Window.setOnUnhandledRejection, .{});
     pub const event = bridge.accessor(Window.getEvent, null, .{ .null_as_undefined = true });
     pub const fetch = bridge.function(Window.fetch, .{});

src/browser/webapi/net/Fetch.zig

@@ -243,7 +243,7 @@ fn httpErrorCallback(ctx: *anyopaque, err: anyerror) void {
     defer ls.deinit();
 
     // fetch() must reject with a TypeError on network errors per spec
-    ls.toLocal(self._resolver).rejectError("fetch error", .{ .type_error = @errorName(err) });
+    ls.toLocal(self._resolver).rejectError("fetch error", .{ .type_error = "fetch error" });
 }
 
 fn httpShutdownCallback(ctx: *anyopaque) void {

src/browser/webapi/net/Request.zig

@@ -192,8 +192,8 @@ pub fn text(self: *const Request, page: *Page) !js.Promise {
 pub fn json(self: *const Request, page: *Page) !js.Promise {
     const body = self._body orelse "";
     const local = page.js.local.?;
-    const value = local.parseJSON(body) catch |err| {
+    const value = local.parseJSON(body) catch {
-        return local.rejectPromise(.{@errorName(err)});
+        return local.rejectPromise(.{ .syntax_error = "failed to parse" });
     };
     return local.resolvePromise(try value.persist());
 }

src/browser/webapi/net/Response.zig

@@ -139,8 +139,8 @@ pub fn getText(self: *const Response, page: *Page) !js.Promise {
 pub fn getJson(self: *Response, page: *Page) !js.Promise {
     const body = self._body orelse "";
     const local = page.js.local.?;
-    const value = local.parseJSON(body) catch |err| {
+    const value = local.parseJSON(body) catch {
-        return local.rejectPromise(.{@errorName(err)});
+        return local.rejectPromise(.{ .syntax_error = "failed to parse" });
     };
     return local.resolvePromise(try value.persist());
 }

src/browser/webapi/streams/ReadableStream.zig

@@ -255,7 +255,7 @@ pub fn pipeThrough(self: *ReadableStream, transform: PipeTransform, page: *Page)
 /// Returns a promise that resolves when piping is complete.
 pub fn pipeTo(self: *ReadableStream, destination: *WritableStream, page: *Page) !js.Promise {
     if (self.getLocked()) {
-        return page.js.local.?.rejectPromise("ReadableStream is locked");
+        return page.js.local.?.rejectPromise(.{ .type_error = "ReadableStream is locked" });
     }
 
     const local = page.js.local.?;

src/browser/webapi/streams/ReadableStreamDefaultReader.zig

@@ -58,12 +58,12 @@ pub const ReadResult = struct {
 
 pub fn read(self: *ReadableStreamDefaultReader, page: *Page) !js.Promise {
     const stream = self._stream orelse {
-        return page.js.local.?.rejectPromise("Reader has been released");
+        return page.js.local.?.rejectPromise(.{ .type_error = "Reader has been released" });
     };
 
     if (stream._state == .errored) {
-        const err = stream._stored_error orelse "Stream errored";
+        //const err = stream._stored_error orelse "Stream errored";
-        return page.js.local.?.rejectPromise(err);
+        return page.js.local.?.rejectPromise(.{ .type_error = "Stream errored" });
     }
 
     if (stream._controller.dequeue()) |chunk| {
@@ -95,7 +95,7 @@ pub fn releaseLock(self: *ReadableStreamDefaultReader) void {
 
 pub fn cancel(self: *ReadableStreamDefaultReader, reason_: ?[]const u8, page: *Page) !js.Promise {
     const stream = self._stream orelse {
-        return page.js.local.?.rejectPromise("Reader has been released");
+        return page.js.local.?.rejectPromise(.{ .type_error = "Reader has been released" });
     };
 
     self.releaseLock();

src/browser/webapi/streams/WritableStreamDefaultWriter.zig

@@ -32,11 +32,11 @@ pub fn init(stream: *WritableStream, page: *Page) !*WritableStreamDefaultWriter
 
 pub fn write(self: *WritableStreamDefaultWriter, chunk: js.Value, page: *Page) !js.Promise {
     const stream = self._stream orelse {
-        return page.js.local.?.rejectPromise("Writer has been released");
+        return page.js.local.?.rejectPromise(.{ .type_error = "Writer has been released" });
     };
 
     if (stream._state != .writable) {
-        return page.js.local.?.rejectPromise("Stream is not writable");
+        return page.js.local.?.rejectPromise(.{ .type_error = "Stream is not writable" });
     }
 
     try stream.writeChunk(chunk, page);
@@ -46,11 +46,11 @@ pub fn write(self: *WritableStreamDefaultWriter, chunk: js.Value, page: *Page) !
 
 pub fn close(self: *WritableStreamDefaultWriter, page: *Page) !js.Promise {
     const stream = self._stream orelse {
-        return page.js.local.?.rejectPromise("Writer has been released");
+        return page.js.local.?.rejectPromise(.{ .type_error = "Writer has been released" });
     };
 
     if (stream._state != .writable) {
-        return page.js.local.?.rejectPromise("Stream is not writable");
+        return page.js.local.?.rejectPromise(.{ .type_error = "Stream is not writable" });
     }
 
     try stream.closeStream(page);
@@ -67,7 +67,7 @@ pub fn releaseLock(self: *WritableStreamDefaultWriter) void {
 
 pub fn getClosed(self: *WritableStreamDefaultWriter, page: *Page) !js.Promise {
     const stream = self._stream orelse {
-        return page.js.local.?.rejectPromise("Writer has been released");
+        return page.js.local.?.rejectPromise(.{ .type_error = "Writer has been released" });
     };
 
     if (stream._state == .closed) {

src/cdp/cdp.zig

@@ -131,7 +131,7 @@ pub fn CDPT(comptime TypeProvider: type) type {
         // timeouts (or http events) which are ready to be processed.
         pub fn pageWait(self: *Self, ms: u32) Session.WaitResult {
             const session = &(self.browser.session orelse return .no_page);
-            return session.wait(ms);
+            return session.wait(.{ .timeout_ms = ms });
         }
 
         // Called from above, in processMessage which handles client messages
@@ -489,12 +489,16 @@ pub fn BrowserContext(comptime CDP_T: type) type {
 
         pub fn createIsolatedWorld(self: *Self, world_name: []const u8, grant_universal_access: bool) !*IsolatedWorld {
             const browser = &self.cdp.browser;
-            const arena = try browser.arena_pool.acquire();
+            const arena = try browser.arena_pool.acquire(.{ .debug = "IsolatedWorld" });
             errdefer browser.arena_pool.release(arena);
 
+            const call_arena = try browser.arena_pool.acquire(.{ .debug = "IsolatedWorld.call_arena" });
+            errdefer browser.arena_pool.release(call_arena);
+
             const world = try arena.create(IsolatedWorld);
             world.* = .{
                 .arena = arena,
+                .call_arena = call_arena,
                 .context = null,
                 .browser = browser,
                 .name = try arena.dupe(u8, world_name),
@@ -745,13 +749,20 @@ pub fn BrowserContext(comptime CDP_T: type) type {
 /// An object id is unique across all contexts, different object ids can refer to the same Node in different contexts.
 const IsolatedWorld = struct {
     arena: Allocator,
+    call_arena: Allocator,
     browser: *Browser,
     name: []const u8,
     context: ?*js.Context = null,
     grant_universal_access: bool,
 
+    // Identity tracking for this isolated world (separate from main world).
+    // This ensures CDP inspector contexts don't share v8::Globals with main world.
+    identity: js.Identity = .{},
+
     pub fn deinit(self: *IsolatedWorld) void {
         self.removeContext() catch {};
+        self.identity.deinit();
+        self.browser.arena_pool.release(self.call_arena);
         self.browser.arena_pool.release(self.arena);
     }
 
@@ -759,6 +770,8 @@ const IsolatedWorld = struct {
         const ctx = self.context orelse return error.NoIsolatedContextToRemove;
         self.browser.env.destroyContext(ctx);
         self.context = null;
+        self.identity.deinit();
+        self.identity = .{};
     }
 
     // The isolate world must share at least some of the state with the related page, specifically the DocumentHTML
@@ -768,7 +781,13 @@ const IsolatedWorld = struct {
     // Currently we have only 1 page/frame and thus also only 1 state in the isolate world.
     pub fn createContext(self: *IsolatedWorld, page: *Page) !*js.Context {
         if (self.context == null) {
-            self.context = try self.browser.env.createContext(page);
+            const ctx = try self.browser.env.createContext(page, .{
+                .identity = &self.identity,
+                .identity_arena = self.arena,
+                .call_arena = self.call_arena,
+                .debug_name = "IsolatedContext",
+            });
+            self.context = ctx;
         } else {
             log.warn(.cdp, "not implemented", .{
                 .feature = "createContext: Not implemented second isolated context creation",

src/cdp/domains/lp.zig

@@ -288,7 +288,7 @@ test "cdp.lp: action tools" {
     const page = try bc.session.createPage();
     const url = "http://localhost:9582/src/browser/tests/mcp_actions.html";
     try page.navigate(url, .{ .reason = .address_bar, .kind = .{ .push = null } });
-    _ = bc.session.wait(5000);
+    _ = bc.session.wait(.{});
 
     // Test Click
     const btn = page.document.getElementById("btn", page).?.asNode();

src/cdp/domains/target.zig

@@ -394,15 +394,13 @@ fn sendMessageToTarget(cmd: anytype) !void {
 }
 
 fn detachFromTarget(cmd: anytype) !void {
-    // TODO check if sessionId/targetId match.
-    // const params = (try cmd.params(struct {
-    //     sessionId: ?[]const u8,
-    //     targetId: ?[]const u8,
-    // })) orelse return error.InvalidParams;
-
     if (cmd.browser_context) |bc| {
+        if (bc.session_id) |session_id| {
+            try cmd.sendEvent("Target.detachedFromTarget", .{
+                .sessionId = session_id,
+            }, .{});
+        }
         bc.session_id = null;
-        // TODO should we send a Target.detachedFromTarget event?
     }
 
     return cmd.sendResult(null, .{});
@@ -427,8 +425,12 @@ fn setAutoAttach(cmd: anytype) !void {
     if (cmd.cdp.target_auto_attach == false) {
         // detach from all currently attached targets.
         if (cmd.browser_context) |bc| {
+            if (bc.session_id) |session_id| {
+                try cmd.sendEvent("Target.detachedFromTarget", .{
+                    .sessionId = session_id,
+                }, .{});
+            }
             bc.session_id = null;
-            // TODO should we send a Target.detachedFromTarget event?
         }
         try cmd.sendResult(null, .{});
         return;
@@ -759,9 +761,11 @@ test "cdp.target: detachFromTarget" {
         try ctx.expectSentResult(.{ .targetId = bc.target_id.? }, .{ .id = 10 });
 
         try ctx.processMessage(.{ .id = 11, .method = "Target.attachToTarget", .params = .{ .targetId = bc.target_id.? } });
-        try ctx.expectSentResult(.{ .sessionId = bc.session_id.? }, .{ .id = 11 });
+        const session_id = bc.session_id.?;
+        try ctx.expectSentResult(.{ .sessionId = session_id }, .{ .id = 11 });
 
         try ctx.processMessage(.{ .id = 12, .method = "Target.detachFromTarget", .params = .{ .targetId = bc.target_id.? } });
+        try ctx.expectSentEvent("Target.detachedFromTarget", .{ .sessionId = session_id }, .{});
         try testing.expectEqual(null, bc.session_id);
         try ctx.expectSentResult(null, .{ .id = 12 });
 
@@ -769,3 +773,36 @@ test "cdp.target: detachFromTarget" {
         try ctx.expectSentResult(.{ .sessionId = bc.session_id.? }, .{ .id = 13 });
     }
 }
+
+test "cdp.target: detachFromTarget without session" {
+    var ctx = testing.context();
+    defer ctx.deinit();
+    _ = try ctx.loadBrowserContext(.{ .id = "BID-9" });
+    {
+        // detach when no session is attached should not send event
+        try ctx.processMessage(.{ .id = 10, .method = "Target.detachFromTarget" });
+        try ctx.expectSentResult(null, .{ .id = 10 });
+        try ctx.expectSentCount(0);
+    }
+}
+
+test "cdp.target: setAutoAttach false sends detachedFromTarget" {
+    var ctx = testing.context();
+    defer ctx.deinit();
+    const bc = try ctx.loadBrowserContext(.{ .id = "BID-9" });
+    {
+        try ctx.processMessage(.{ .id = 10, .method = "Target.createTarget", .params = .{ .browserContextId = "BID-9" } });
+        try testing.expectEqual(true, bc.target_id != null);
+        try ctx.expectSentResult(.{ .targetId = bc.target_id.? }, .{ .id = 10 });
+
+        try ctx.processMessage(.{ .id = 11, .method = "Target.attachToTarget", .params = .{ .targetId = bc.target_id.? } });
+        const session_id = bc.session_id.?;
+        try ctx.expectSentResult(.{ .sessionId = session_id }, .{ .id = 11 });
+
+        // setAutoAttach false should fire detachedFromTarget event
+        try ctx.processMessage(.{ .id = 12, .method = "Target.setAutoAttach", .params = .{ .autoAttach = false, .waitForDebuggerOnStart = false } });
+        try ctx.expectSentEvent("Target.detachedFromTarget", .{ .sessionId = session_id }, .{});
+        try testing.expectEqual(null, bc.session_id);
+        try ctx.expectSentResult(null, .{ .id = 12 });
+    }
+}

src/cdp/testing.zig

@@ -136,7 +136,7 @@ const TestContext = struct {
                 0,
             );
             try page.navigate(full_url, .{});
-            _ = bc.session.wait(2000);
+            _ = bc.session.wait(.{});
         }
         return bc;
     }

src/lightpanda.zig

@@ -46,6 +46,7 @@ const IS_DEBUG = @import("builtin").mode == .Debug;
 
 pub const FetchOpts = struct {
     wait_ms: u32 = 5000,
+    wait_until: Config.WaitUntil = .load,
     dump: dump.Opts,
     dump_mode: ?Config.DumpFormat = null,
     writer: ?*std.Io.Writer = null,
@@ -107,7 +108,7 @@ pub fn fetch(app: *App, url: [:0]const u8, opts: FetchOpts) !void {
         .reason = .address_bar,
         .kind = .{ .push = null },
     });
-    _ = session.wait(opts.wait_ms);
+    _ = session.wait(.{ .timeout_ms = opts.wait_ms, .until = opts.wait_until });
 
     const writer = opts.writer orelse return;
     if (opts.dump_mode) |mode| {

src/main.zig

@@ -121,7 +121,8 @@ fn run(allocator: Allocator, main_arena: Allocator) !void {
             log.debug(.app, "startup", .{ .mode = "fetch", .dump_mode = opts.dump_mode, .url = url, .snapshot = app.snapshot.fromEmbedded() });
 
             var fetch_opts = lp.FetchOpts{
-                .wait_ms = 5000,
+                .wait_ms = opts.wait_ms,
+                .wait_until = opts.wait_until,
                 .dump_mode = opts.dump_mode,
                 .dump = .{
                     .strip = opts.strip,

src/main_legacy_test.zig

@@ -106,7 +106,7 @@ pub fn run(allocator: Allocator, file: []const u8, session: *lp.Session) !void {
     defer try_catch.deinit();
 
     try page.navigate(url, .{});
-    _ = session.wait(2000);
+    _ = session.wait(.{});
 
     ls.local.eval("testing.assertOk()", "testing.assertOk()") catch |err| {
         const caught = try_catch.caughtOrError(allocator, err);

src/mcp/Server.zig

@@ -87,7 +87,7 @@ pub fn sendResult(self: *Self, id: std.json.Value, result: anytype) !void {
 }
 
 pub fn sendError(self: *Self, id: std.json.Value, code: protocol.ErrorCode, message: []const u8) !void {
-    try self.sendResponse(.{
+    try self.sendResponse(protocol.Response{
         .id = id,
         .@"error" = protocol.Error{
             .code = @intFromEnum(code),
@@ -114,7 +114,7 @@ test "MCP.Server - Integration: synchronous smoke test" {
 
     try router.processRequests(server, &in_reader);
 
-    try testing.expectJson(.{ .id = 1 }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = 1 }, out_alloc.writer.buffered());
 }
 
 test "MCP.Server - Integration: ping request returns an empty result" {
@@ -135,5 +135,5 @@ test "MCP.Server - Integration: ping request returns an empty result" {
 
     try router.processRequests(server, &in_reader);
 
-    try testing.expectJson(.{ .id = "ping-1", .result = .{} }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = "ping-1", .result = .{} }, out_alloc.writer.buffered());
 }

src/mcp/router.zig

@@ -120,7 +120,7 @@ test "MCP.router - handleMessage - synchronous unit tests" {
         \\{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test-client","version":"1.0.0"}}}
     );
     try testing.expectJson(
-        \\{ "id": 1, "result": { "capabilities": { "tools": {} } } }
+        \\{ "jsonrpc": "2.0", "id": 1, "result": { "capabilities": { "tools": {} } } }
     , out_alloc.writer.buffered());
     out_alloc.writer.end = 0;
 
@@ -128,14 +128,14 @@ test "MCP.router - handleMessage - synchronous unit tests" {
     try handleMessage(server, aa,
         \\{"jsonrpc":"2.0","id":2,"method":"ping"}
     );
-    try testing.expectJson(.{ .id = 2, .result = .{} }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = 2, .result = .{} }, out_alloc.writer.buffered());
     out_alloc.writer.end = 0;
 
     // 3. Tools list
     try handleMessage(server, aa,
         \\{"jsonrpc":"2.0","id":3,"method":"tools/list"}
     );
-    try testing.expectJson(.{ .id = 3 }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = 3 }, out_alloc.writer.buffered());
     try testing.expect(std.mem.indexOf(u8, out_alloc.writer.buffered(), "\"name\":\"goto\"") != null);
     out_alloc.writer.end = 0;
 
@@ -143,7 +143,7 @@ test "MCP.router - handleMessage - synchronous unit tests" {
     try handleMessage(server, aa,
         \\{"jsonrpc":"2.0","id":4,"method":"unknown_method"}
     );
-    try testing.expectJson(.{ .id = 4, .@"error" = .{ .code = -32601 } }, out_alloc.writer.buffered());
+    try testing.expectJson(.{ .jsonrpc = "2.0", .id = 4, .@"error" = .{ .code = -32601 } }, out_alloc.writer.buffered());
     out_alloc.writer.end = 0;
 
     // 5. Parse error
@@ -152,6 +152,6 @@ test "MCP.router - handleMessage - synchronous unit tests" {
         defer filter.deinit();
 
         try handleMessage(server, aa, "invalid json");
-        try testing.expectJson("{\"id\": null, \"error\": {\"code\": -32700}}", out_alloc.writer.buffered());
+        try testing.expectJson("{\"jsonrpc\": \"2.0\", \"id\": null, \"error\": {\"code\": -32700}}", out_alloc.writer.buffered());
     }
 }

src/mcp/tools.zig

@@ -558,7 +558,7 @@ fn performGoto(server: *Server, url: [:0]const u8, id: std.json.Value) !void {
         return error.NavigationFailed;
     };
 
-    _ = server.session.wait(5000);
+    _ = server.session.wait(.{});
 }
 
 const testing = @import("../testing.zig");
@@ -623,7 +623,7 @@ test "MCP - Actions: click, fill, scroll" {
     const page = try server.session.createPage();
     const url = "http://localhost:9582/src/browser/tests/mcp_actions.html";
     try page.navigate(url, .{ .reason = .address_bar, .kind = .{ .push = null } });
-    _ = server.session.wait(5000);
+    _ = server.session.wait(.{});
 
     // Test Click
     const btn = page.document.getElementById("btn", page).?.asNode();

src/testing.zig

@@ -415,7 +415,7 @@ fn runWebApiTest(test_file: [:0]const u8) !void {
     defer try_catch.deinit();
 
     try page.navigate(url, .{});
-    _ = test_session.wait(2000);
+    _ = test_session.wait(.{});
 
     test_browser.runMicrotasks();
 
@@ -439,7 +439,7 @@ pub fn pageTest(comptime test_file: []const u8) !*Page {
     );
 
     try page.navigate(url, .{});
-    _ = test_session.wait(2000);
+    _ = test_session.wait(.{});
     return page;
 }