fix(input): mousedown focuses tabindex targets, not only contenteditable

focusEditingHostForMouseDown only walked contenteditable hosts, so a
div[tabindex=0] stayed unfocused after click. Replace it with
focusForMouseDown: still prefer the outermost editing host, then focus
the nearest mouse-focusable element (including tabindex=-1).

Call sites: actions.click, CDP triggerMousePress, WebDriver pointerDown.

Tests cover the MCP selector path, agent Page.click on the HTML fixture,
and a runtime-created child click (ancestor walk, non-focusable must not
steal focus, tabindex=-1 is mouse-focusable).

src/browser/actions.zig

@@ -98,8 +98,8 @@ pub fn click(node: *DOMNode, frame: *Frame) !void {
     const suppress_mouse = try dispatchPointer(el, "pointerdown", 1, 0, frame);
     if (!suppress_mouse) {
         try dispatchMouse(el, "mousedown", 1, frame);
-        Frame.user_input.focusEditingHostForMouseDown(frame, el) catch |err| {
-            lp.log.warn(.app, "click editable focus", .{ .err = err });
+        Frame.user_input.focusForMouseDown(frame, el) catch |err| {
+            lp.log.warn(.app, "click mousedown focus", .{ .err = err });
         };
     }
 

src/browser/frame/user_input.zig

@@ -209,7 +209,7 @@ pub fn triggerMousePress(frame: *Frame, x: f64, y: f64, button: i32) !void {
         });
     }
     try dispatchMouseEventOn(frame, target, "mousedown", x, y, button, 0);
-    try focusEditingHostForMouseDown(frame, target);
+    try focusForMouseDown(frame, target);
 }
 
 pub fn triggerMouseMove(frame: *Frame, x: f64, y: f64) !void {
@@ -353,9 +353,9 @@ fn isEditingHost(node: *Node) bool {
     return std.ascii.eqlIgnoreCase(value, "false") == false;
 }
 
-// A mousedown on editable content focuses its editing host: the outermost
-// element of the contiguous editable chain containing the target.
-pub fn focusEditingHostForMouseDown(frame: *Frame, target: *Element) !void {
+// Find the outermost element of the contiguous editable chain containing the
+// target.
+fn outermostEditingHost(target: *Element) ?*Element {
     var node: ?*Node = target.asNode();
     var editable: ?*Node = null;
     while (node) |n| : (node = n._parent) {
@@ -364,15 +364,55 @@ pub fn focusEditingHostForMouseDown(frame: *Frame, target: *Element) !void {
             break;
         }
     }
-    var host = editable orelse return;
+    var host = editable orelse return null;
     while (host._parent) |p| {
         if (!isEditingHost(p)) {
             break;
         }
         host = p;
     }
-    const host_element = host.is(Element) orelse return;
-    try host_element.focus(frame);
+    return host.is(Element);
+}
+
+/// `null` means the element is not mouse-focusable. Unlike sequential focus,
+/// any explicit tabindex value, including a negative one, is mouse-focusable.
+fn mouseFocusTabIndex(el: *Element) ?i32 {
+    if (el.isDisabled()) return null;
+    if (el.is(Element.Html) == null) return null;
+
+    if (el.getAttributeSafe(comptime .wrap("tabindex"))) |attr| {
+        return Element.Html.parseInteger(attr) orelse 0;
+    }
+
+    const native = switch (el.getTag()) {
+        .button, .select, .textarea, .iframe => true,
+        .input => el.as(Element.Html.Input)._input_type != .hidden,
+        .anchor, .area => el.getAttributeSafe(comptime .wrap("href")) != null,
+        else => false,
+    };
+    return if (native) 0 else null;
+}
+
+fn isMouseFocusable(el: *Element) bool {
+    return mouseFocusTabIndex(el) != null;
+}
+
+/// Mousedown default action: focus the editing host if the click is inside
+/// one, otherwise the nearest mouse-focusable element (self or ancestor).
+pub fn focusForMouseDown(frame: *Frame, target: *Element) !void {
+    if (outermostEditingHost(target)) |host| {
+        try host.focus(frame);
+        return;
+    }
+
+    var node: ?*Node = target.asNode();
+    while (node) |n| : (node = n._parent) {
+        const el = n.is(Element) orelse continue;
+        if (isMouseFocusable(el)) {
+            try el.focus(frame);
+            return;
+        }
+    }
 }
 
 // Per the DOM dispatch algorithm, a click's activation target is the event

src/browser/tests/mcp_actions.html

@@ -21,6 +21,8 @@
     <input id="rad" type="radio" name="group1">
     <button id="btnPreventDefault">Prevent Default</button>
     <button id="btnDisabled" disabled>Disabled</button>
+    <div id="focusTarget" tabindex="0" onclick="window.focusTargetFocused = document.activeElement === this;">Focus me</div>
+    <div id="plain" onclick="window.focusAfterPlain = document.activeElement.id;">Not focusable</div>
     <script>
         window.seq = [];
         const btn = document.getElementById('btn');

src/browser/webapi/WebDriver.zig

@@ -299,8 +299,8 @@ fn performPointerSource(source: js.Object, frame: *Frame) !void {
                 dispatchTouch(el, "touchstart", frame);
             } else {
                 dispatchMouse(el, "mousedown", button, buttonsMask(button), click_count, frame);
-                Frame.user_input.focusEditingHostForMouseDown(frame, el) catch |err| {
-                    log.warn(.app, "webdriver editable focus", .{ .err = err });
+                Frame.user_input.focusForMouseDown(frame, el) catch |err| {
+                    log.warn(.app, "webdriver mousedown focus", .{ .err = err });
                 };
             }
         } else if (action_type.eql(comptime .wrap("pointerUp"))) {

src/mcp/tools.zig

@@ -1084,6 +1084,24 @@ test "MCP - Actions: click, fill, scroll, hover, press, selectOption, setChecked
         out.clearRetainingCapacity();
     }
 
+    {
+        const msg =
+            \\{"jsonrpc":"2.0","id":12,"method":"tools/call","params":{"name":"click","arguments":{"selector":"#focusTarget"}}}
+        ;
+        try router.handleMessage(server, aa, msg);
+        try testing.expect(std.mem.indexOf(u8, out.written(), "Clicked element") != null);
+        out.clearRetainingCapacity();
+    }
+
+    {
+        const msg =
+            \\{"jsonrpc":"2.0","id":13,"method":"tools/call","params":{"name":"click","arguments":{"selector":"#plain"}}}
+        ;
+        try router.handleMessage(server, aa, msg);
+        try testing.expect(std.mem.indexOf(u8, out.written(), "Clicked element") != null);
+        out.clearRetainingCapacity();
+    }
+
     {
         const inp = frame.document.getElementById("inp", frame).?.asNode();
         const inp_id = (try server.active_session.registry.register(inp)).id;
@@ -1189,6 +1207,7 @@ test "MCP - Actions: click, fill, scroll, hover, press, selectOption, setChecked
         \\ ]) &&
         \\ JSON.stringify(window.seqPrevented) === JSON.stringify(['pointerdown', 'pointerup', 'click']) &&
         \\ window.disabledMousedowned === false &&
+        \\ window.focusTargetFocused === true && window.focusAfterPlain === 'focusTarget' &&
         \\ window.clicked === true && window.inputVal === 'hello' &&
         \\ window.changed === true && window.selChanged === 'opt2' &&
         \\ window.scrolled === true &&

src/script/Runtime.zig

@@ -1441,6 +1441,56 @@ test "agent script runtime: tool errors throw and stop execution" {
     );
 }
 
+test "agent script runtime: selector click preserves pointer mouse semantics" {
+    defer testing.test_session.closeAllPages();
+
+    var registry = CDPNode.Registry.init(testing.allocator);
+    defer registry.deinit();
+
+    const runtime = try Runtime.init(testing.allocator, testing.test_app, testing.test_session, &registry);
+    defer runtime.deinit();
+
+    try runTestScript(runtime,
+        \\const page = new Page();
+        \\await page.goto("http://localhost:9582/src/browser/tests/mcp_actions.html");
+        \\page.click("#btn");
+        \\const full = page.evaluate("JSON.stringify(window.seq)");
+        \\if (full !== '["pointerdown:0:1:mouse:true","mousedown:0:1::true","pointerup:0:0:mouse:true","mouseup:0:0::true","click:0:0:mouse:true"]') throw new Error("wrong full click sequence: " + full);
+        \\page.click("#btnPreventDefault");
+        \\const suppressed = page.evaluate("JSON.stringify(window.seqPrevented)");
+        \\if (suppressed !== '["pointerdown","pointerup","click"]') throw new Error("wrong suppressed sequence: " + suppressed);
+        \\page.click("#btnDisabled");
+        \\if (page.evaluate("String(window.disabledMousedowned)") !== "false") throw new Error("disabled button received mousedown");
+        \\page.click("#focusTarget");
+        \\if (page.evaluate("document.activeElement.id") !== "focusTarget") throw new Error("mousedown focus default action was lost");
+    );
+}
+
+// Different workflow from the fixture above: the tabindex node is created at
+// runtime, the click lands on a child (ancestor walk), a following click on a
+// non-focusable node must not steal focus, and tabindex=-1 is still mouse-focusable.
+test "agent script runtime: dynamic tabindex child click focuses ancestor" {
+    defer testing.test_session.closeAllPages();
+
+    var registry = CDPNode.Registry.init(testing.allocator);
+    defer registry.deinit();
+
+    const runtime = try Runtime.init(testing.allocator, testing.test_app, testing.test_session, &registry);
+    defer runtime.deinit();
+
+    try runTestScript(runtime,
+        \\const page = new Page();
+        \\await page.goto("http://localhost:9582/src/browser/tests/mcp_actions.html");
+        \\page.evaluate("const p=document.createElement('div');p.id='dynFocus';p.setAttribute('tabindex','0');const s=document.createElement('span');s.id='dynChild';s.textContent='x';p.appendChild(s);document.body.appendChild(p);const n=document.createElement('div');n.id='dynNeg';n.setAttribute('tabindex','-1');n.textContent='neg';document.body.appendChild(n)");
+        \\page.click("#dynChild");
+        \\if (page.evaluate("document.activeElement.id") !== "dynFocus") throw new Error("child click did not focus tabindex ancestor: " + page.evaluate("document.activeElement && document.activeElement.id"));
+        \\page.click("#plain");
+        \\if (page.evaluate("document.activeElement.id") !== "dynFocus") throw new Error("plain click stole focus: " + page.evaluate("document.activeElement && document.activeElement.id"));
+        \\page.click("#dynNeg");
+        \\if (page.evaluate("document.activeElement.id") !== "dynNeg") throw new Error("tabindex=-1 was not mouse-focusable: " + page.evaluate("document.activeElement && document.activeElement.id"));
+    );
+}
+
 test "agent script runtime: builtin argument marshalling (positional + options)" {
     defer testing.test_session.closeAllPages();