diff --git a/addons/base_automation/static/tests/base_automation_error_dialog.js b/addons/base_automation/static/tests/base_automation_error_dialog.js
index f0ae2a60417..2d6ff31a62f 100644
--- a/addons/base_automation/static/tests/base_automation_error_dialog.js
+++ b/addons/base_automation/static/tests/base_automation_error_dialog.js
@@ -84,11 +84,7 @@ QUnit.module("base_automation", {}, function () {
         await mount(MainComponentsContainer, target, { env });
 
         const errorEvent = new PromiseRejectionEvent("error", {
-            reason: {
-                message: error,
-                legacy: true,
-                event: $.Event(),
-            },
+            reason: error,
             promise: null,
             cancelable: true,
             bubbles: true,
@@ -112,11 +108,7 @@ QUnit.module("base_automation", {}, function () {
         await mount(MainComponentsContainer, target, { env });
 
         const errorEvent = new PromiseRejectionEvent("error", {
-            reason: {
-                message: error,
-                legacy: true,
-                event: $.Event(),
-            },
+            reason: error,
             promise: null,
             cancelable: true,
             bubbles: true,
diff --git a/addons/bus/__manifest__.py b/addons/bus/__manifest__.py
index f1dfdae281b..d29765fe5d8 100644
--- a/addons/bus/__manifest__.py
+++ b/addons/bus/__manifest__.py
@@ -32,7 +32,6 @@
             ('remove', 'bus/static/tests/helpers/**/*'),
         ],
         'bus.websocket_worker_assets': [
-            'web/static/src/legacy/js/promise_extension.js',
             'web/static/src/module_loader.js',
             'bus/static/src/workers/*',
         ],
diff --git a/addons/mrp_subcontracting/__manifest__.py b/addons/mrp_subcontracting/__manifest__.py
index 3c95ac63297..3740563ac74 100644
--- a/addons/mrp_subcontracting/__manifest__.py
+++ b/addons/mrp_subcontracting/__manifest__.py
@@ -57,7 +57,6 @@
             'web/static/src/views/fields/translation_dialog.scss',
             'web/static/src/scss/fontawesome_overridden.scss',
 
-            'web/static/src/legacy/js/promise_extension.js',
             'web/static/src/module_loader.js',
             'web/static/src/session.js',
 
@@ -128,8 +127,6 @@
             # Form style should be computed before
             'web/static/src/views/form/button_box/*.scss',
 
-            'web/static/src/legacy/legacy_promise_error_handler.js',
-            'web/static/src/legacy/legacy_rpc_error_handler.js',
             'web/static/src/legacy/utils.js',
 
             'mrp_subcontracting/static/src/subcontracting_portal/*',
diff --git a/addons/payment/static/src/js/payment_form.js b/addons/payment/static/src/js/payment_form.js
index fbe1697816e..d5829fc37a4 100644
--- a/addons/payment/static/src/js/payment_form.js
+++ b/addons/payment/static/src/js/payment_form.js
@@ -5,6 +5,7 @@ import { browser } from '@web/core/browser/browser';
 import { ConfirmationDialog } from '@web/core/confirmation_dialog/confirmation_dialog';
 import { _t } from '@web/core/l10n/translation';
 import { renderToMarkup } from '@web/core/utils/render';
+import { RPCError } from '@web/core/network/rpc_service';
 
 publicWidget.registry.PaymentForm = publicWidget.Widget.extend({
     selector: '#o_payment_form',
@@ -91,11 +92,14 @@ publicWidget.registry.PaymentForm = publicWidget.Widget.extend({
             [tokenId],
         ).then(linkedRecordsInfo => {
             this._challengeTokenDeletion(tokenId, linkedRecordsInfo);
-        }).guardedCatch(error => {
-            error.event.preventDefault();
-            this._displayErrorDialog(
-                _t("Cannot delete payment method"), error.message.data.message
-            );
+        }).catch(error => {
+            if (error instanceof RPCError) {
+                this._displayErrorDialog(
+                    _t("Cannot delete payment method"), error.data.message
+                );
+            } else {
+                return Promise.reject(error);
+            }
         });
     },
 
@@ -356,10 +360,13 @@ publicWidget.registry.PaymentForm = publicWidget.Widget.extend({
             'access_token': this.paymentContext['accessToken'],
         }).then(() => {
             window.location = this.paymentContext['landingRoute'];
-        }).guardedCatch(error => {
-            error.event.preventDefault();
-            this._displayErrorDialog(_t("Cannot save payment method"), error.message.data.message);
-            this._enableButton(); // The button has been disabled before initiating the flow.
+        }).catch(error => {
+            if (error instanceof RPCError) {
+                this._displayErrorDialog(_t("Cannot save payment method"), error.data.message);
+                this._enableButton(); // The button has been disabled before initiating the flow.
+            } else {
+                return Promise.reject(error);
+            }
         });
     },
 
@@ -399,10 +406,13 @@ publicWidget.registry.PaymentForm = publicWidget.Widget.extend({
                     providerCode, paymentOptionId, paymentMethodCode, processingValues
                 );
             }
-        }).guardedCatch(error => {
-            error.event.preventDefault();
-            this._displayErrorDialog(_t("Payment processing failed"), error.message.data.message);
-            this._enableButton(); // The button has been disabled before initiating the flow.
+        }).catch(error => {
+            if (error instanceof RPCError) {
+                this._displayErrorDialog(_t("Payment processing failed"), error.data.message);
+                this._enableButton(); // The button has been disabled before initiating the flow.
+            } else {
+                return Promise.reject(error);
+            }
         });
     },
 
@@ -500,11 +510,14 @@ publicWidget.registry.PaymentForm = publicWidget.Widget.extend({
             'token_id': tokenId,
         }).then(() => {
             browser.location.reload();
-        }).guardedCatch(error => {
-            error.event.preventDefault();
-            this._displayErrorDialog(
-                _t("Cannot delete payment method"), error.message.data.message
-            );
+        }).catch(error => {
+            if (error instanceof RPCError) {
+                this._displayErrorDialog(
+                    _t("Cannot delete payment method"), error.data.message
+                );
+            } else {
+                return Promise.reject(error);
+            }
         });
     },
 
diff --git a/addons/payment/static/src/js/post_processing.js b/addons/payment/static/src/js/post_processing.js
index 83b383d36f4..fc9556397f0 100644
--- a/addons/payment/static/src/js/post_processing.js
+++ b/addons/payment/static/src/js/post_processing.js
@@ -4,6 +4,7 @@ import publicWidget from '@web/legacy/js/public/public_widget';
 import { renderToElement } from '@web/core/utils/render';
 import { markup } from "@odoo/owl";
 import { _t } from '@web/core/l10n/translation';
+import { ConnectionLostError, RPCError } from '@web/core/network/rpc_service';
 
 publicWidget.registry.PaymentPostProcessing = publicWidget.Widget.extend({
     selector: 'div[name="o_payment_status"]',
@@ -46,10 +47,9 @@ publicWidget.registry.PaymentPostProcessing = publicWidget.Widget.extend({
                 } else {
                     self._poll();
                 }
-            }).guardedCatch(error => {
-                error.event.preventDefault();
-                if (error.message.data) { // Server error.
-                    switch (error.message.data.message) {
+            }).catch(error => {
+                if (error instanceof RPCError) { // Server error.
+                    switch (error.data.message) {
                         case 'retry':
                             self._poll();
                             break;
@@ -58,13 +58,15 @@ publicWidget.registry.PaymentPostProcessing = publicWidget.Widget.extend({
                             break;
                         default:
                             self._renderTemplate(
-                                'payment.exception', { error_message: error.message.data.message }
+                                'payment.exception', { error_message: error.data.message }
                             );
                             break;
                     }
-                } else { // RPC error (server unreachable).
+                } else if (error instanceof ConnectionLostError) { // RPC error (server unreachable).
                     self._renderTemplate('payment.rpc_error');
                     self._poll();
+                } else {
+                    return Promise.reject(error);
                 }
             });
         }, this.timeout);
diff --git a/addons/payment_adyen/static/src/js/payment_form.js b/addons/payment_adyen/static/src/js/payment_form.js
index d19ebd586b1..2fd502da0ef 100644
--- a/addons/payment_adyen/static/src/js/payment_form.js
+++ b/addons/payment_adyen/static/src/js/payment_form.js
@@ -3,6 +3,7 @@
 
 import { _t } from '@web/core/l10n/translation';
 import paymentForm from '@payment/js/payment_form';
+import { RPCError } from '@web/core/network/rpc_service';
 
 paymentForm.include({
 
@@ -72,12 +73,15 @@ paymentForm.include({
                     onSubmit: this._adyenOnSubmit.bind(this),
                 };
                 this.adyenCheckout = await AdyenCheckout(configuration);
-            }).guardedCatch((error) => {
-                error.event.preventDefault();
-                this._displayErrorDialog(
-                    _t("Cannot display the payment form"), error.message.data.message
-                );
-                this._enableButton();
+            }).catch((error) => {
+                if (error instanceof RPCError) {
+                    this._displayErrorDialog(
+                        _t("Cannot display the payment form"), error.data.message
+                    );
+                    this._enableButton();
+                } else {
+                    return Promise.reject(error);
+                }
             });
         }
 
@@ -182,10 +186,13 @@ paymentForm.include({
             } else { // The payment reached a final state; redirect to the status page.
                 window.location = '/payment/status';
             }
-        }).guardedCatch((error) => {
-            error.event.preventDefault();
-            this._displayErrorDialog(_t("Payment processing failed"), error.message.data.message);
-            this._enableButton();
+        }).catch((error) => {
+            if (error instanceof RPCError) {
+                this._displayErrorDialog(_t("Payment processing failed"), error.data.message);
+                this._enableButton();
+            } else {
+                return Promise.reject(error);
+            }
         });
     },
 
@@ -208,10 +215,13 @@ paymentForm.include({
             } else { // The payment reached a final state; redirect to the status page.
                 window.location = '/payment/status';
             }
-        }).guardedCatch((error) => {
-            error.event.preventDefault();
-            this._displayErrorDialog(_t("Payment processing failed"), error.message.data.message);
-            this._enableButton();
+        }).catch((error) => {
+            if (error instanceof RPCError) {
+                this._displayErrorDialog(_t("Payment processing failed"), error.data.message);
+                this._enableButton();
+            } else {
+                return Promise.reject(error);
+            }
         });
     },
 
diff --git a/addons/payment_authorize/static/src/js/payment_form.js b/addons/payment_authorize/static/src/js/payment_form.js
index 4f85bc07198..beba66e971b 100644
--- a/addons/payment_authorize/static/src/js/payment_form.js
+++ b/addons/payment_authorize/static/src/js/payment_form.js
@@ -5,6 +5,7 @@ import { _t } from '@web/core/l10n/translation';
 import { loadJS } from '@web/core/assets';
 
 import paymentForm from '@payment/js/payment_form';
+import { RPCError } from '@web/core/network/rpc_service';
 
 paymentForm.include({
 
@@ -145,10 +146,13 @@ paymentForm.include({
             'access_token': processingValues.access_token,
         }).then(() => {
             window.location = '/payment/status';
-        }).guardedCatch((error) => {
-            error.event.preventDefault();
-            this._displayErrorDialog(_t("Payment processing failed"), error.message.data.message);
-            this._enableButton();
+        }).catch((error) => {
+            if (error instanceof RPCError) {
+                this._displayErrorDialog(_t("Payment processing failed"), error.data.message);
+                this._enableButton();
+            } else {
+                return Promise.reject(error);
+            }
         });
     },
 
diff --git a/addons/payment_demo/static/src/js/payment_demo_mixin.js b/addons/payment_demo/static/src/js/payment_demo_mixin.js
index c25673761db..09614c584c1 100644
--- a/addons/payment_demo/static/src/js/payment_demo_mixin.js
+++ b/addons/payment_demo/static/src/js/payment_demo_mixin.js
@@ -1,7 +1,7 @@
 /** @odoo-module **/
 
 import { _t } from "@web/core/l10n/translation";
-import { jsonrpc } from "@web/core/network/rpc_service";
+import { jsonrpc, RPCError } from "@web/core/network/rpc_service";
 
 export default {
 
@@ -22,10 +22,13 @@ export default {
             'simulated_state': simulatedPaymentState,
         }).then(() => {
             window.location = '/payment/status';
-        }).guardedCatch(error => {
-            error.event.preventDefault();
-            this._displayErrorDialog(_t("Payment processing failed"), error.message.data.message);
-            this._enableButton?.(); // This method doesn't exists in Express Checkout form.
+        }).catch(error => {
+            if (error instanceof RPCError) {
+                this._displayErrorDialog(_t("Payment processing failed"), error.data.message);
+                this._enableButton?.(); // This method doesn't exists in Express Checkout form.
+            } else {
+                return Promise.reject(error);
+            }
         });
     },
 
diff --git a/addons/point_of_sale/__manifest__.py b/addons/point_of_sale/__manifest__.py
index 4141441a938..fd2d5a9dd1c 100644
--- a/addons/point_of_sale/__manifest__.py
+++ b/addons/point_of_sale/__manifest__.py
@@ -110,8 +110,6 @@
             'web/static/lib/owl/odoo_module.js',
             'web_editor/static/lib/html2canvas.js',
             'web/static/lib/zxing-library/zxing-library.js',
-            # FIXME POSREF legacy dependencies to remove
-            'web/static/src/legacy/js/promise_extension.js',
             # JS framework
             ('include', 'web._assets_core'),
             ('remove', 'web/static/src/core/errors/error_handlers.js'), # error handling in PoS is different from the webclient
diff --git a/addons/point_of_sale/static/src/app/navbar/closing_popup/closing_popup.js b/addons/point_of_sale/static/src/app/navbar/closing_popup/closing_popup.js
index ba5c5f6788d..0afd936ca74 100644
--- a/addons/point_of_sale/static/src/app/navbar/closing_popup/closing_popup.js
+++ b/addons/point_of_sale/static/src/app/navbar/closing_popup/closing_popup.js
@@ -186,11 +186,7 @@ export class ClosePosPopup extends AbstractAwaitablePopup {
             // We have to handle the error manually otherwise the validation check stops the script.
             // In case of "rescue session", we want to display the next popup with "handleClosingError".
             // FIXME
-            if (
-                !error.message &&
-                !error.message.data &&
-                error.message.data.message !== "This session is already closed."
-            ) {
+            if (!error.data && error.data.message !== "This session is already closed.") {
                 throw error;
             }
         }
diff --git a/addons/portal/static/src/js/portal_composer.js b/addons/portal/static/src/js/portal_composer.js
index fed8af22af9..3f66c6be5d8 100644
--- a/addons/portal/static/src/js/portal_composer.js
+++ b/addons/portal/static/src/js/portal_composer.js
@@ -6,6 +6,7 @@ import { renderToElement } from "@web/core/utils/render";
 import publicWidget from "@web/legacy/js/public/public_widget";
 import { post } from "@web/core/network/http_service";
 import { Component } from "@odoo/owl";
+import { RPCError } from "@web/core/network/rpc_service";
 
 /**
  * Widget PortalComposer
@@ -124,12 +125,14 @@ var PortalComposer = publicWidget.Widget.extend({
                     self.attachments.push(attachment);
                     self._updateAttachments();
                     resolve();
-                }).guardedCatch(function (error) {
-                    self.notification.add(
-                        _t("Could not save file <strong>%s</strong>", escape(file.name)),
-                        { type: 'warning', sticky: true }
-                    );
-                    resolve();
+                }).catch(function (error) {
+                    if (error instanceof RPCError) {
+                        self.notification.add(
+                            _t("Could not save file <strong>%s</strong>", escape(file.name)),
+                            { type: 'warning', sticky: true }
+                        );
+                        resolve();
+                    }
                 });
             });
         })).then(function () {
diff --git a/addons/project/__manifest__.py b/addons/project/__manifest__.py
index cc14f87e338..907aae927b5 100644
--- a/addons/project/__manifest__.py
+++ b/addons/project/__manifest__.py
@@ -107,7 +107,6 @@
             'web/static/src/views/fields/translation_dialog.scss',
             'web/static/src/scss/fontawesome_overridden.scss',
 
-            'web/static/src/legacy/js/promise_extension.js',
             'web/static/src/module_loader.js',
             'web/static/src/session.js',
 
@@ -180,8 +179,6 @@
             # Form style should be computed before
             'web/static/src/views/form/button_box/*.scss',
 
-            'web/static/src/legacy/legacy_promise_error_handler.js',
-            'web/static/src/legacy/legacy_rpc_error_handler.js',
             'web/static/src/legacy/utils.js',
 
             'web_editor/static/src/js/editor/odoo-editor/src/base_style.scss',
diff --git a/addons/web/__manifest__.py b/addons/web/__manifest__.py
index aee3c669aeb..31991dbaeaf 100644
--- a/addons/web/__manifest__.py
+++ b/addons/web/__manifest__.py
@@ -62,8 +62,6 @@ This module provides the core of the Odoo Web Client.
             'web/static/src/views/fields/translation_dialog.scss',
             'web/static/src/legacy/scss/ui.scss',
 
-            'web/static/src/legacy/js/promise_extension.js',
-
             'web/static/lib/jquery/jquery.js',
             'web/static/lib/jquery.ui/jquery-ui.js',
             'web/static/lib/popper/popper.js',
@@ -117,8 +115,6 @@ This module provides the core of the Odoo Web Client.
             # Form style should be computed before
             'web/static/src/views/form/button_box/*.scss',
 
-            'web/static/src/legacy/legacy_promise_error_handler.js',
-            'web/static/src/legacy/legacy_rpc_error_handler.js',
             'web/static/src/legacy/utils.js',
 
             'web/static/src/legacy/xml/base.xml',
@@ -131,7 +127,6 @@ This module provides the core of the Odoo Web Client.
             'web/static/src/start.js',
         ],
         'web.assets_frontend_minimal': [
-            'web/static/src/legacy/js/promise_extension.js',
             'web/static/src/module_loader.js',
             'web/static/src/session.js',
             'web/static/src/core/browser/cookie.js',
@@ -228,14 +223,11 @@ This module provides the core of the Odoo Web Client.
             'web/static/src/legacy/js/public/public_root_instance.js',
             'web/static/src/legacy/js/public/public_widget.js',
             'web/static/src/legacy/js/public/signin.js',
-            'web/static/src/legacy/legacy_promise_error_handler.js',
-            'web/static/src/legacy/legacy_rpc_error_handler.js',
 
         ],
         'web.assets_frontend_lazy': [
             ('include', 'web.assets_frontend'),
             # Remove assets_frontend_minimal
-            ('remove', 'web/static/src/legacy/js/promise_extension.js'),
             ('remove', 'web/static/src/module_loader.js'),
             ('remove', 'web/static/src/session.js'),
             ('remove', 'web/static/src/core/browser/cookie.js'),
diff --git a/addons/web/static/src/core/errors/error_service.js b/addons/web/static/src/core/errors/error_service.js
index 3e147222594..2a291351dd6 100644
--- a/addons/web/static/src/core/errors/error_service.js
+++ b/addons/web/static/src/core/errors/error_service.js
@@ -61,7 +61,11 @@ export const errorService = {
                     return;
                 }
             }
-            if (uncaughtError.event && !uncaughtError.event.defaultPrevented) {
+            if (
+                uncaughtError.event &&
+                !uncaughtError.event.defaultPrevented &&
+                uncaughtError.traceback
+            ) {
                 // Log the full traceback instead of letting the browser log the incomplete one
                 uncaughtError.event.preventDefault();
                 console.error(uncaughtError.traceback);
diff --git a/addons/web/static/src/legacy/js/core/dialog.js b/addons/web/static/src/legacy/js/core/dialog.js
index f39a1b605f1..822eff5dcb4 100644
--- a/addons/web/static/src/legacy/js/core/dialog.js
+++ b/addons/web/static/src/legacy/js/core/dialog.js
@@ -427,8 +427,9 @@ Dialog.confirm = function (owner, message, options) {
             }
             isBlocked = true;
             const callbackRes = callback && callback.apply(this, arguments);
-            Promise.resolve(callbackRes).guardedCatch(() => {
+            Promise.resolve(callbackRes).catch((e) => {
                 isBlocked = false;
+                return Promise.reject(e);
             });
             return callbackRes;
         };
diff --git a/addons/web/static/src/legacy/js/core/dom.js b/addons/web/static/src/legacy/js/core/dom.js
index 636feda7f10..80b693341ed 100644
--- a/addons/web/static/src/legacy/js/core/dom.js
+++ b/addons/web/static/src/legacy/js/core/dom.js
@@ -302,7 +302,7 @@ var dom = {
 
             _lock();
             var result = fct.apply(this, arguments);
-            Promise.resolve(result).then(_unlock).guardedCatch(_unlock);
+            Promise.resolve(result).finally(_unlock);
             return result;
         };
     },
@@ -342,7 +342,7 @@ var dom = {
             Promise.resolve(dom.DEBOUNCE && delay(dom.DEBOUNCE)).then(function () {
                 $button.removeClass('pe-none');
                 const restore = dom.addButtonLoadingEffect($button[0]);
-                return Promise.resolve(result).then(restore).guardedCatch(restore);
+                return Promise.resolve(result).finally(restore);
             });
 
             return result;
diff --git a/addons/web/static/src/legacy/js/core/mixins.js b/addons/web/static/src/legacy/js/core/mixins.js
index cfad2af7473..5a5d64064fd 100644
--- a/addons/web/static/src/legacy/js/core/mixins.js
+++ b/addons/web/static/src/legacy/js/core/mixins.js
@@ -84,7 +84,7 @@ var ParentedMixin = {
                 } else if (shouldReject) {
                     reject();
                 }
-            }).guardedCatch(function (reason) {
+            }).catch(function (reason) {
                 if (!self.isDestroyed()) {
                     reject(reason);
                 } else if (shouldReject) {
diff --git a/addons/web/static/src/legacy/js/core/service_mixins.js b/addons/web/static/src/legacy/js/core/service_mixins.js
index 6e2a21a1755..ffddedc5d13 100644
--- a/addons/web/static/src/legacy/js/core/service_mixins.js
+++ b/addons/web/static/src/legacy/js/core/service_mixins.js
@@ -1,11 +1,6 @@
 /** @odoo-module **/
 
 import { SERVICES_METADATA } from "@web/env";
-import {
-    ConnectionAbortedError,
-    ConnectionLostError,
-    RPCError,
-} from "@web/core/network/rpc_service";
 import { Component } from "@odoo/owl";
 
 function protectMethod(widget, fn) {
@@ -19,15 +14,7 @@ function protectMethod(widget, fn) {
                 })
                 .catch((reason) => {
                     if (!widget.isDestroyed()) {
-                        if (reason instanceof RPCError || reason instanceof ConnectionLostError) {
-                            // we do not reject an error here because we want to pass through
-                            // the legacy guardedCatch code
-                            reject({ message: reason, event: $.Event(), legacy: true });
-                        } else if (reason instanceof ConnectionAbortedError) {
-                            reject({ message: reason.message, event: $.Event("abort") });
-                        } else {
-                            reject(reason);
-                        }
+                        reject(reason);
                     }
                 });
         });
diff --git a/addons/web/static/src/legacy/js/promise_extension.js b/addons/web/static/src/legacy/js/promise_extension.js
deleted file mode 100644
index 9e12e1cc713..00000000000
--- a/addons/web/static/src/legacy/js/promise_extension.js
+++ /dev/null
@@ -1,23 +0,0 @@
-/**
- * This file adds a 'guardedCatch' function to the Promise API. This function
- * has to be used when we don't want to swallow real errors (crashes), like
- * 'catch' does (i.e. basically all the time in Odoo). We only execute the
- * 'onRejected' handler if the rejection's reason is not an Error, and we always
- * return a rejected Promise to let the rejection bubble up (and trigger the
- * 'unhandledrejection' event).
- */
-
-(function () {
-    var _catch = Promise.prototype.catch;
-    Promise.prototype.guardedCatch = function (onRejected) {
-        return _catch.call(this, function (reason) {
-            const error = (reason instanceof Error && "cause" in reason) ? reason.cause : reason;
-            if (!error || !(error instanceof Error)) {
-                if (onRejected) {
-                    onRejected.call(this, reason);
-                }
-            }
-            return Promise.reject(reason);
-        });
-    };
-})();
diff --git a/addons/web/static/src/legacy/js/public/public_root.js b/addons/web/static/src/legacy/js/public/public_root.js
index 177efbfc778..27bb5bc46dd 100644
--- a/addons/web/static/src/legacy/js/public/public_root.js
+++ b/addons/web/static/src/legacy/js/public/public_root.js
@@ -15,6 +15,7 @@ import { MainComponentsContainer } from "@web/core/main_components_container";
 import { browser } from '@web/core/browser/browser';
 import { _t } from "@web/core/l10n/translation";
 import { App, Component, whenReady } from "@odoo/owl";
+import { RPCError } from '@web/core/network/rpc_service';
 
 const { Settings } = luxon;
 
@@ -258,7 +259,12 @@ export const PublicRoot = publicWidget.RootWidget.extend({
     _onWidgetsStartRequest: function (ev) {
         this._startWidgets(ev.data.$target, ev.data.options)
             .then(ev.data.onSuccess)
-            .guardedCatch(ev.data.onFailure);
+            .catch((e) => {
+                ev.data.onFailure(e);
+                if (!(e instanceof RPCError)) {
+                    return Promise.reject(e);
+                }
+            });
     },
     /**
      * Called when the root is notified that the public widgets have to be
diff --git a/addons/web/static/src/legacy/legacy_promise_error_handler.js b/addons/web/static/src/legacy/legacy_promise_error_handler.js
deleted file mode 100644
index 0b5eab6c0a1..00000000000
--- a/addons/web/static/src/legacy/legacy_promise_error_handler.js
+++ /dev/null
@@ -1,38 +0,0 @@
-/** @odoo-module **/
-
-import { registry } from "@web/core/registry";
-
-/**
- * @typedef {import("../env").OdooEnv} OdooEnv
- * @typedef {import("../core/errors/error_service").UncaughtPromiseError} UncaughtPromiseError
- */
-
-// -----------------------------------------------------------------------------
-// Legacy Promise error handling
-// -----------------------------------------------------------------------------
-
-/**
- * @param {OdooEnv} env
- * @param {Error} error
- * @param {Error} originalError
- * @returns {boolean}
- */
-function legacyRejectPromiseHandler(env, error, originalError) {
-    if (error.name.startsWith("UncaughtPromiseError")) {
-        const isLegitError = originalError && originalError instanceof Error;
-        const isLegacyRPC = originalError && originalError.legacy;
-        if (!isLegitError && !isLegacyRPC) {
-            // we consider that a code throwing something that is not an error is
-            // a case where it is meant as an asynchronous control flow (as legacy
-            // code is sadly doing). For now, we just want to consider this as a non
-            // error, so we prevent default it.
-            error.unhandledRejectionEvent.preventDefault();
-            return true;
-        }
-    }
-    return false;
-}
-
-registry
-    .category("error_handlers")
-    .add("legacyRejectPromiseHandler", legacyRejectPromiseHandler, { sequence: 1 });
diff --git a/addons/web/static/src/legacy/legacy_rpc_error_handler.js b/addons/web/static/src/legacy/legacy_rpc_error_handler.js
deleted file mode 100644
index 15158225b8d..00000000000
--- a/addons/web/static/src/legacy/legacy_rpc_error_handler.js
+++ /dev/null
@@ -1,47 +0,0 @@
-/** @odoo-module **/
-
-import { registry } from "@web/core/registry";
-import { ConnectionLostError, RPCError } from "../core/network/rpc_service";
-import { lostConnectionHandler, rpcErrorHandler } from "@web/core/errors/error_handlers";
-
-const errorHandlerRegistry = registry.category("error_handlers");
-
-/**
- * @typedef {import("../env").OdooEnv} OdooEnv
- * @typedef {import("../core/errors/error_service").UncaughtError} UncaughError
- */
-
-// -----------------------------------------------------------------------------
-// Legacy RPC error handling
-// -----------------------------------------------------------------------------
-
-/**
- * @param {OdooEnv} env
- * @param {UncaughError} error
- * @param {Error} originalError
- * @returns {boolean}
- */
-function legacyRPCErrorHandler(env, error, originalError) {
-    if (
-        originalError &&
-        originalError.legacy &&
-        originalError.message &&
-        (originalError.message instanceof RPCError ||
-            originalError.message instanceof ConnectionLostError)
-    ) {
-        const event = originalError.event;
-        originalError = originalError.message;
-        if (event.isDefaultPrevented()) {
-            // in theory, here, event was already handled
-            error.unhandledRejectionEvent.preventDefault();
-            return true;
-        }
-        event.preventDefault();
-        if (originalError instanceof ConnectionLostError) {
-            return lostConnectionHandler(env, error, originalError);
-        }
-        return rpcErrorHandler(env, error, originalError);
-    }
-    return false;
-}
-errorHandlerRegistry.add("legacyRPCErrorHandler", legacyRPCErrorHandler, { sequence: 97 });
diff --git a/addons/web_editor/__manifest__.py b/addons/web_editor/__manifest__.py
index 3a3cb1f0095..f2740e33eb5 100644
--- a/addons/web_editor/__manifest__.py
+++ b/addons/web_editor/__manifest__.py
@@ -47,7 +47,6 @@ Odoo Web Editor widget.
             'web/static/src/views/fields/translation_dialog.scss',
             'web/static/src/scss/fontawesome_overridden.scss',
 
-            'web/static/src/legacy/js/promise_extension.js',
             'web/static/src/module_loader.js',
             'web/static/src/session.js',
 
@@ -249,7 +248,6 @@ Odoo Web Editor widget.
             'web_editor/static/src/js/editor/odoo-editor/test/utils.js'
         ],
         'web_editor.mocha_tests': [
-            'web/static/src/legacy/js/promise_extension.js',
             'web/static/src/module_loader.js',
             # insert module dependencies here
             'web/static/src/core/utils/concurrency.js',
diff --git a/addons/web_editor/static/src/js/editor/snippets.editor.js b/addons/web_editor/static/src/js/editor/snippets.editor.js
index 8ff6e0b6df8..052cf837250 100644
--- a/addons/web_editor/static/src/js/editor/snippets.editor.js
+++ b/addons/web_editor/static/src/js/editor/snippets.editor.js
@@ -26,6 +26,7 @@ import { LinkTools } from '@web_editor/js/wysiwyg/widgets/link_tools';
 import { touching, closest } from "@web/core/utils/ui";
 import { _t } from "@web/core/l10n/translation";
 import { renderToElement } from "@web/core/utils/render";
+import { RPCError } from "@web/core/network/rpc_service";
 
 let cacheSnippetTemplate = {};
 
@@ -3948,14 +3949,17 @@ var SnippetsMenu = Widget.extend({
                             _toMutex: true,
                             reloadWebClient: true,
                         });
-                    }).guardedCatch(reason => {
-                        reason.event.preventDefault();
-                        this.close();
-                        const message = markup(_t("Could not install module <strong>%s</strong>", escape(name)));
-                        self.notification.add(message, {
-                            type: 'danger',
-                            sticky: true,
-                        });
+                    }).catch(reason => {
+                        if (reason instanceof RPCError) {
+                            this.close();
+                            const message = markup(_t("Could not install module <strong>%s</strong>", escape(name)));
+                            self.notification.add(message, {
+                                type: 'danger',
+                                sticky: true,
+                            });
+                        } else {
+                            return Promise.reject(reason);
+                        }
                     });
                 },
             }, {
diff --git a/addons/web_editor/static/src/js/wysiwyg/wysiwyg.js b/addons/web_editor/static/src/js/wysiwyg/wysiwyg.js
index f7a79b3220a..3c7c72c1ce0 100644
--- a/addons/web_editor/static/src/js/wysiwyg/wysiwyg.js
+++ b/addons/web_editor/static/src/js/wysiwyg/wysiwyg.js
@@ -2597,7 +2597,7 @@ export class Wysiwyg extends Component {
                 return this[saveElementFuncName]($els, context || this.options.context)
                 .then(function () {
                     $els.removeClass('o_dirty');
-                }).guardedCatch(function (response) {
+                }).catch(function (response) {
                     // because ckeditor regenerates all the dom, we can't just
                     // setup the popover here as everything will be destroyed by
                     // the DOM regeneration. Add markings instead, and returns a
@@ -2617,7 +2617,7 @@ export class Wysiwyg extends Component {
         });
         return Promise.all(proms).then(function () {
             window.onbeforeunload = null;
-        }).guardedCatch((failed) => {
+        }).catch((failed) => {
             // If there were errors, re-enable edition
             this.cancel(false);
         });
diff --git a/addons/website/static/src/js/editor/widget_link.js b/addons/website/static/src/js/editor/widget_link.js
index 201b1642a67..5bc26ac4401 100644
--- a/addons/website/static/src/js/editor/widget_link.js
+++ b/addons/website/static/src/js/editor/widget_link.js
@@ -81,8 +81,7 @@ patch(LinkTools.prototype, {
                     $option.data('value', anchor);
                     $selectMenu.append($option);
                 }
-                always();
-            }).guardedCatch(always);
+            }).finally(always);
         }
         $selectMenu.data("anchor-for", urlInputValue);
     },
diff --git a/addons/website/static/src/snippets/s_website_form/000.js b/addons/website/static/src/snippets/s_website_form/000.js
index a50c33df54a..051b509e083 100644
--- a/addons/website/static/src/snippets/s_website_form/000.js
+++ b/addons/website/static/src/snippets/s_website_form/000.js
@@ -456,7 +456,7 @@ const { DateTime } = luxon;
                     self.restoreBtnLoading();
                 }
             })
-            .guardedCatch(error => {
+            .catch(error => {
                 this.update_status(
                     'error',
                     error.status && error.status === 413 ? _t("Uploaded file is too large.") : "",
diff --git a/addons/website_crm_partner_assign/static/src/js/crm_partner_assign.js b/addons/website_crm_partner_assign/static/src/js/crm_partner_assign.js
index 55251d906e8..12d7e13d19a 100644
--- a/addons/website_crm_partner_assign/static/src/js/crm_partner_assign.js
+++ b/addons/website_crm_partner_assign/static/src/js/crm_partner_assign.js
@@ -3,6 +3,7 @@
 import { _t } from "@web/core/l10n/translation";
 import publicWidget from "@web/legacy/js/public/public_widget";
 import { parseDate, formatDate, serializeDate } from "@web/core/l10n/dates";
+import { RPCError } from "@web/core/network/rpc_service";
 const { DateTime } = luxon;
 
 publicWidget.registry.crmPartnerAssign = publicWidget.Widget.extend({
@@ -37,8 +38,11 @@ publicWidget.registry.crmPartnerAssign = publicWidget.Widget.extend({
     _buttonExec: function ($btn, callback) {
         // TODO remove once the automatic system which does this lands in master
         $btn.prop('disabled', true);
-        return callback.call(this).guardedCatch(function () {
+        return callback.call(this).catch(function (e) {
             $btn.prop('disabled', false);
+            if (!(e instanceof RPCError)) {
+                return Promise.reject(e);
+            }
         });
     },
     /**
diff --git a/addons/website_mail/static/src/js/follow.js b/addons/website_mail/static/src/js/follow.js
index ee95dce05f0..58e9e193856 100644
--- a/addons/website_mail/static/src/js/follow.js
+++ b/addons/website_mail/static/src/js/follow.js
@@ -41,7 +41,7 @@ publicWidget.registry.follow = publicWidget.Widget.extend({
 
         this.rpc('/website_mail/is_follower', {
             records: records,
-        }).then(always).guardedCatch(always);
+        }).then(always, always);
 
         // not if editable mode to allow designer to edit
         if (!this.editableMode) {
diff --git a/addons/website_mass_mailing/static/src/js/website_mass_mailing.js b/addons/website_mass_mailing/static/src/js/website_mass_mailing.js
index fe0c6137b52..117b5d7afc5 100644
--- a/addons/website_mass_mailing/static/src/js/website_mass_mailing.js
+++ b/addons/website_mass_mailing/static/src/js/website_mass_mailing.js
@@ -43,7 +43,7 @@ publicWidget.registry.subscribe = publicWidget.Widget.extend({
         return Promise.all([def, this.rpc('/website_mass_mailing/is_subscriber', {
             'list_id': this._getListId(),
             'subscription_type': inputName,
-        }).then(always).guardedCatch(always)]);
+        }).then(always, always)]);
     },
     /**
      * @override
diff --git a/addons/website_sale_wishlist/static/src/js/website_sale_wishlist.js b/addons/website_sale_wishlist/static/src/js/website_sale_wishlist.js
index b457d4cbcee..f0a798f10dc 100644
--- a/addons/website_sale_wishlist/static/src/js/website_sale_wishlist.js
+++ b/addons/website_sale_wishlist/static/src/js/website_sale_wishlist.js
@@ -3,6 +3,7 @@
 import publicWidget from "@web/legacy/js/public/public_widget";
 import wSaleUtils from "@website_sale/js/website_sale_utils";
 import VariantMixin from "@website_sale/js/sale_variant_mixin";
+import { RPCError } from "@web/core/network/rpc_service";
 
 // VariantMixin events are overridden on purpose here
 // to avoid registering them more than once since they are already registered
@@ -116,12 +117,18 @@ publicWidget.registry.ProductWishlist = publicWidget.Widget.extend(VariantMixin,
                     if (productId === currentProductId) {
                         $el.prop("disabled", true).addClass('disabled');
                     }
-                }).guardedCatch(function () {
+                }).catch(function (e) {
                     $el.prop("disabled", false).removeClass('disabled');
+                    if (!(e instanceof RPCError)) {
+                        return Promise.reject(e);
+                    }
                 });
             }
-        }).guardedCatch(function () {
+        }).catch(function (e) {
             $el.prop("disabled", false).removeClass('disabled');
+            if (!(e instanceof RPCError)) {
+                return Promise.reject(e);
+            }
         });
     },
     /**
diff --git a/addons/website_slides/__manifest__.py b/addons/website_slides/__manifest__.py
index 522e48eae7f..fb0cac56db9 100644
--- a/addons/website_slides/__manifest__.py
+++ b/addons/website_slides/__manifest__.py
@@ -147,7 +147,6 @@ Featuring
             'web/static/src/legacy/scss/modal.scss',
             'website/static/src/libs/zoomodoo/zoomodoo.scss',
 
-            'web/static/src/legacy/js/promise_extension.js',
             'web/static/src/module_loader.js',
             'web/static/src/session.js',