diff --git a/cypress/integration/1-register/register.spec.ts b/cypress/integration/1-register/register.spec.ts
index f719da5547..e06d1e5f28 100644
--- a/cypress/integration/1-register/register.spec.ts
+++ b/cypress/integration/1-register/register.spec.ts
@@ -16,27 +16,25 @@ limitations under the License.
 
 /// <reference types="cypress" />
 
-import { SynapseInstance } from "../../plugins/synapsedocker/index";
+import { SynapseInstance } from "../../plugins/synapsedocker";
 
 describe("Registration", () => {
-    let synapseId;
-    let synapsePort;
+    let synapse: SynapseInstance;
 
     beforeEach(() => {
-        cy.task<SynapseInstance>("synapseStart", "consent").then(result => {
-            synapseId = result.synapseId;
-            synapsePort = result.port;
+        cy.startSynapse("consent").then(data => {
+            synapse = data;
         });
         cy.visit("/#/register");
     });
 
     afterEach(() => {
-        cy.task("synapseStop", synapseId);
+        cy.stopSynapse(synapse);
     });
 
     it("registers an account and lands on the home screen", () => {
         cy.get(".mx_ServerPicker_change", { timeout: 15000 }).click();
-        cy.get(".mx_ServerPickerDialog_otherHomeserver").type(`http://localhost:${synapsePort}`);
+        cy.get(".mx_ServerPickerDialog_otherHomeserver").type(`http://localhost:${synapse.port}`);
         cy.get(".mx_ServerPickerDialog_continue").click();
         // wait for the dialog to go away
         cy.get('.mx_ServerPickerDialog').should('not.exist');
diff --git a/cypress/plugins/index.ts b/cypress/plugins/index.ts
index db01ceceb4..9438d13606 100644
--- a/cypress/plugins/index.ts
+++ b/cypress/plugins/index.ts
@@ -16,8 +16,13 @@ limitations under the License.
 
 /// <reference types="cypress" />
 
-import { synapseDocker } from "./synapsedocker/index";
+import { synapseDocker } from "./synapsedocker";
+import PluginEvents = Cypress.PluginEvents;
+import PluginConfigOptions = Cypress.PluginConfigOptions;
 
-export default function(on, config) {
+/**
+ * @type {Cypress.PluginConfig}
+ */
+export default function(on: PluginEvents, config: PluginConfigOptions) {
     synapseDocker(on, config);
 }
diff --git a/cypress/plugins/synapsedocker/index.ts b/cypress/plugins/synapsedocker/index.ts
index 0f029e7b2e..912e99431e 100644
--- a/cypress/plugins/synapsedocker/index.ts
+++ b/cypress/plugins/synapsedocker/index.ts
@@ -22,6 +22,9 @@ import * as crypto from "crypto";
 import * as childProcess from "child_process";
 import * as fse from "fs-extra";
 
+import PluginEvents = Cypress.PluginEvents;
+import PluginConfigOptions = Cypress.PluginConfigOptions;
+
 // A cypress plugins to add command to start & stop synapses in
 // docker with preset templates.
 
@@ -130,7 +133,7 @@ async function synapseStart(template: string): Promise<SynapseInstance> {
     return synapses.get(synapseId);
 }
 
-async function synapseStop(id) {
+async function synapseStop(id: string): Promise<void> {
     const synCfg = synapses.get(id);
 
     if (!synCfg) throw new Error("Unknown synapse ID");
@@ -186,10 +189,10 @@ async function synapseStop(id) {
 /**
  * @type {Cypress.PluginConfig}
  */
-// eslint-disable-next-line no-unused-vars
-export function synapseDocker(on, config) {
+export function synapseDocker(on: PluginEvents, config: PluginConfigOptions) {
     on("task", {
-        synapseStart, synapseStop,
+        synapseStart,
+        synapseStop,
     });
 
     on("after:spec", async (spec) => {
@@ -197,7 +200,7 @@ export function synapseDocker(on, config) {
         // This is on the theory that we should avoid re-using synapse
         // instances between spec runs: they should be cheap enough to
         // start that we can have a separate one for each spec run or even
-        // test. If we accidentally re-use synapses, we could inadvertantly
+        // test. If we accidentally re-use synapses, we could inadvertently
         // make our tests depend on each other.
         for (const synId of synapses.keys()) {
             console.warn(`Cleaning up synapse ID ${synId} after ${spec.name}`);
diff --git a/cypress/support/index.ts b/cypress/support/index.ts
index 9901ef4cb8..289319fe97 100644
--- a/cypress/support/index.ts
+++ b/cypress/support/index.ts
@@ -1,3 +1,19 @@
-// Empty file to prevent cypress from recreating a helpful example
-// file on every run (their example file doesn't use semicolons and
-// so fails our lint rules).
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+/// <reference types="cypress" />
+
+import "./synapse";
diff --git a/cypress/support/synapse.ts b/cypress/support/synapse.ts
new file mode 100644
index 0000000000..f49f55a19d
--- /dev/null
+++ b/cypress/support/synapse.ts
@@ -0,0 +1,55 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+/// <reference types="cypress" />
+
+import Chainable = Cypress.Chainable;
+import AUTWindow = Cypress.AUTWindow;
+import { SynapseInstance } from "../plugins/synapsedocker";
+
+declare global {
+    // eslint-disable-next-line @typescript-eslint/no-namespace
+    namespace Cypress {
+        interface Chainable {
+            /**
+             * Start a synapse instance with a given config template.
+             * @param template path to template within cypress/plugins/synapsedocker/template/ directory.
+             */
+            startSynapse(template: string): Chainable<SynapseInstance>;
+            /**
+             * Custom command wrapping task:synapseStop whilst preventing uncaught exceptions
+             * for if Synapse stopping races with the app's background sync loop.
+             * @param synapse the synapse instance returned by startSynapse
+             */
+            stopSynapse(synapse: SynapseInstance): Chainable<AUTWindow>;
+        }
+    }
+}
+
+function startSynapse(template: string): Chainable<SynapseInstance> {
+    return cy.task<SynapseInstance>("synapseStart", template);
+}
+
+function stopSynapse(synapse: SynapseInstance): Chainable<AUTWindow> {
+    // Navigate away from app to stop the background network requests which will race with Synapse shutting down
+    return cy.window().then((win) => {
+        win.location.href = 'about:blank';
+        cy.task("synapseStop", synapse.synapseId);
+    });
+}
+
+Cypress.Commands.add("startSynapse", startSynapse);
+Cypress.Commands.add("stopSynapse", stopSynapse);