diff --git a/project_ux/__manifest__.py b/project_ux/__manifest__.py
index 6feeced6..0740b8e8 100644
--- a/project_ux/__manifest__.py
+++ b/project_ux/__manifest__.py
@@ -19,7 +19,7 @@
 ##############################################################################
 {
     "name": "Project UX",
-    "version": "19.0.2.1.0",
+    "version": "19.0.2.2.0",
     "category": "Project Management",
     "sequence": 14,
     "author": "ADHOC SA",
@@ -35,6 +35,12 @@
         "views/project_project_views.xml",
         "views/project_task_type_views.xml",
     ],
+    "assets": {
+        "web.assets_backend": [
+            "project_ux/static/src/**/*.js",
+            "project_ux/static/src/**/*.xml",
+        ],
+    },
     "demo": [],
     "installable": True,
     "auto_install": False,
diff --git a/project_ux/static/src/js/project_task_control_panel_patch.js b/project_ux/static/src/js/project_task_control_panel_patch.js
new file mode 100644
index 00000000..282913fa
--- /dev/null
+++ b/project_ux/static/src/js/project_task_control_panel_patch.js
@@ -0,0 +1,23 @@
+import { patch } from "@web/core/utils/patch";
+import { ProjectTaskControlPanel } from "@project/views/project_task_control_panel/project_task_control_panel";
+import { hasSubtaskLeaf } from "./subtask_domain";
+
+patch(ProjectTaskControlPanel.prototype, {
+    /**
+     * The "Is Sub-Task" filter forces sub-tasks to be visible: the model drops
+     * the `display_in_project` restriction while that filter is active (see
+     * project_task_list_model_patch). While it is active the "Show Sub-Tasks"
+     * toggle has no real effect.
+     */
+    get isSubtaskFilterActive() {
+        return hasSubtaskLeaf(this.env.searchModel.domain);
+    },
+
+    /**
+     * State the toggle is painted with: also selected when the filter forces
+     * it, to avoid the confusing "off but showing sub-tasks" state.
+     */
+    get effectiveShowSubtasks() {
+        return this.state.showSubtasks || this.isSubtaskFilterActive;
+    },
+});
diff --git a/project_ux/static/src/js/project_task_list_model_patch.js b/project_ux/static/src/js/project_task_list_model_patch.js
new file mode 100644
index 00000000..413ebeb5
--- /dev/null
+++ b/project_ux/static/src/js/project_task_list_model_patch.js
@@ -0,0 +1,25 @@
+import { patch } from "@web/core/utils/patch";
+import { Domain } from "@web/core/domain";
+import { ProjectTaskRelationalModel } from "@project/views/project_task_relational_model";
+import { hasSubtaskLeaf } from "./subtask_domain";
+
+patch(ProjectTaskRelationalModel.prototype, {
+    /**
+     * When the user filters explicitly by sub-tasks ("Is Sub-Task" filter),
+     * the core still hides them while the "Show Sub-Tasks" mode is off: it
+     * injects `display_in_project = True`, which is False for any sub-task
+     * sharing its parent's project. The result is an empty list with no hint,
+     * so the sub-task looks like it does not exist.
+     *
+     * If the sub-task filter is active, drop that leaf to honor the filter and
+     * show the sub-tasks without requiring the user to toggle the display mode
+     * by hand.
+     */
+    _processSearchDomain(domain) {
+        const processed = super._processSearchDomain(domain);
+        if (hasSubtaskLeaf(domain)) {
+            return Domain.removeDomainLeaves(processed, ["display_in_project"]).toList({});
+        }
+        return processed;
+    },
+});
diff --git a/project_ux/static/src/js/subtask_domain.js b/project_ux/static/src/js/subtask_domain.js
new file mode 100644
index 00000000..570545c8
--- /dev/null
+++ b/project_ux/static/src/js/subtask_domain.js
@@ -0,0 +1,26 @@
+/**
+ * Whether a search domain explicitly restricts results to sub-tasks, i.e. it
+ * contains a `parent_id != False` leaf (as emitted by the "Is Sub-Task"
+ * filter). Walks the domain in list form, including nested sub-domains.
+ *
+ * @param {Array} domain domain in list form
+ * @returns {boolean}
+ */
+export function hasSubtaskLeaf(domain) {
+    if (!Array.isArray(domain)) {
+        return false;
+    }
+    for (const item of domain) {
+        if (!Array.isArray(item)) {
+            continue;
+        }
+        if (item.length === 3) {
+            if (item[0] === "parent_id" && item[1] === "!=" && item[2] === false) {
+                return true;
+            }
+        } else if (hasSubtaskLeaf(item)) {
+            return true;
+        }
+    }
+    return false;
+}
diff --git a/project_ux/static/src/xml/project_task_control_panel.xml b/project_ux/static/src/xml/project_task_control_panel.xml
new file mode 100644
index 00000000..9c44022b
--- /dev/null
+++ b/project_ux/static/src/xml/project_task_control_panel.xml
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<templates xml:space="preserve">
+
+    <t t-name="project_ux.ProjectTaskControlPanel"
+       t-inherit="project.ProjectTaskControlPanel"
+       t-inherit-mode="extension">
+        <xpath expr="//DropdownItem[@onSelected=&quot;() =&gt; this.onClickShowSubtasks()&quot;]" position="attributes">
+            <attribute name="class">effectiveShowSubtasks ? 'selected' : ''</attribute>
+        </xpath>
+    </t>
+
+    <t t-name="project_ux.MobileCombinedActionsDropdown"
+       t-inherit="project.MobileCombinedActionsDropdown"
+       t-inherit-mode="extension">
+        <xpath expr="//DropdownItem[@onSelected=&quot;() =&gt; this.onClickShowSubtasks()&quot;]" position="attributes">
+            <attribute name="class">effectiveShowSubtasks ? 'selected' : ''</attribute>
+        </xpath>
+    </t>
+
+</templates>