diff --git a/.github/workflows/test-api-contract.yaml b/.github/workflows/test-api-contract.yaml
index 3707f4de..4ca36da0 100644
--- a/.github/workflows/test-api-contract.yaml
+++ b/.github/workflows/test-api-contract.yaml
@@ -15,6 +15,9 @@ jobs:
       - uses: actions/setup-python@v4
         with:
           python-version: "3.10"
+      - uses: actions/setup-node@v3
+        with:
+          node-version: 16
 
       - run: cd oasst-shared && pip install -e .
 
@@ -22,9 +25,14 @@ jobs:
 
       - run: cd backend && pip install -r requirements.txt
 
+      - run: cd website && npm install
+
       - run: ./scripts/backend-development/start-mock-server.sh
 
-      - name: Run contract tests
+      - name: Run Python OasstApiClient contract tests
         run: ./scripts/oasst-shared-development/test.sh
 
+      - name: Run JavaScript OasstApiClient contract tests
+        run: ./scripts/frontend-development/run-contract-test.sh
+
       - run: ./scripts/backend-development/stop-mock-server.sh
diff --git a/scripts/frontend-development/run-contract-test.sh b/scripts/frontend-development/run-contract-test.sh
new file mode 100755
index 00000000..6bedc903
--- /dev/null
+++ b/scripts/frontend-development/run-contract-test.sh
@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+parent_path=$( cd "$(dirname "${BASH_SOURCE[0]}")" ; pwd -P )
+
+# switch to website directory
+pushd "$parent_path/../../website"
+
+set -xe
+
+npm run cypress:run:contract
+
+popd
diff --git a/website/cypress.config.contract.js b/website/cypress.config.contract.js
new file mode 100644
index 00000000..f4461158
--- /dev/null
+++ b/website/cypress.config.contract.js
@@ -0,0 +1,9 @@
+import { defineConfig } from "cypress";
+
+export default defineConfig({
+  e2e: {
+    // No baseUrl here, because we don't need it for contract testing
+    baseUrl: null,
+    specPattern: "cypress/contract/*.cy.{ts,js}",
+  },
+});
diff --git a/website/cypress/contract/oasst_api_contract_tests.cy.ts b/website/cypress/contract/oasst_api_contract_tests.cy.ts
new file mode 100644
index 00000000..ff5bb156
--- /dev/null
+++ b/website/cypress/contract/oasst_api_contract_tests.cy.ts
@@ -0,0 +1,29 @@
+import OasstApiClient from "src/lib/oasst_api_client";
+
+describe("Contract test for Oasst API", function () {
+  // Assumes this is running the mock server.
+  const oasstApiClient = new OasstApiClient("http://localhost:8080", "test");
+
+  it("can fetch a task", async () => {
+    expect(
+      await oasstApiClient.fetchTask("random", {
+        sub: "test",
+        name: "test",
+        email: "test",
+      })
+    ).to.be.not.null;
+  });
+
+  it("can ack a task", async () => {
+    const task = await oasstApiClient.fetchTask("random", {
+      sub: "test",
+      name: "test",
+      email: "test",
+    });
+    expect(await oasstApiClient.ackTask(task.id, "321")).to.be.null;
+  });
+
+  // TODO(#354): Add test for 204
+  // TODO(#354): Add test for parsing >=300, throwing an OasstError
+  // TODO(#354): Add test for parsing >=300, throwing a generic error
+});
diff --git a/website/package.json b/website/package.json
index c66e10ca..7d3b680e 100644
--- a/website/package.json
+++ b/website/package.json
@@ -12,6 +12,7 @@
     "build-storybook": "build-storybook",
     "cypress": "cypress open",
     "cypress:run": "cypress run",
+    "cypress:run:contract": "cypress run --config-file ./cypress.config.contract.js",
     "cypress:image-baseline": "cypress-image-diff -u",
     "fix:lint": "eslint --fix src/ --ext .js,.jsx,.ts,.tsx",
     "fix:format": "prettier --write ./src",
diff --git a/website/src/lib/oasst_api_client.ts b/website/src/lib/oasst_api_client.ts
new file mode 100644
index 00000000..45a0859e
--- /dev/null
+++ b/website/src/lib/oasst_api_client.ts
@@ -0,0 +1,64 @@
+import { JWT } from "next-auth/jwt";
+
+class OasstError {
+  message: string;
+  errorCode: number;
+  httpStatusCode: number;
+
+  constructor(message: string, errorCode: number, httpStatusCode: number) {
+    this.message = message;
+    this.errorCode = errorCode;
+    this.httpStatusCode = httpStatusCode;
+  }
+}
+
+export default class OasstApiClient {
+  constructor(private readonly oasstApiUrl: string, private readonly oasstApiKey: string) {}
+
+  private async post(path: string, body: any): Promise<any> {
+    const resp = await fetch(`${this.oasstApiUrl}${path}`, {
+      method: "POST",
+      headers: {
+        "X-API-Key": this.oasstApiKey,
+        "Content-Type": "application/json",
+      },
+      body: JSON.stringify(body),
+    });
+
+    if (resp.status == 204) {
+      return null;
+    }
+
+    if (resp.status >= 300) {
+      const errorText = await resp.text();
+      try {
+        const error = JSON.parse(errorText);
+        throw new OasstError(error.message, error.error_code, resp.status);
+      } catch (e) {
+        throw new OasstError(errorText, 0, resp.status);
+      }
+    }
+
+    return await resp.json();
+  }
+
+  // TODO return a strongly typed Task?
+  // This method is used to store a task in RegisteredTask.task.
+  // This is a raw Json type, so we can't use it to strongly type the task.
+  async fetchTask(taskType: string, userToken: JWT): Promise<any> {
+    return this.post("/api/v1/tasks/", {
+      type: taskType,
+      user: {
+        id: userToken.sub,
+        display_name: userToken.name || userToken.email,
+        auth_method: "local",
+      },
+    });
+  }
+
+  async ackTask(taskId: string, messageId: string): Promise<void> {
+    return this.post(`/api/v1/tasks/${taskId}/ack`, {
+      message_id: messageId,
+    });
+  }
+}
diff --git a/website/src/pages/api/new_task/[task_type].ts b/website/src/pages/api/new_task/[task_type].ts
index 50f0b4e2..bbe31bef 100644
--- a/website/src/pages/api/new_task/[task_type].ts
+++ b/website/src/pages/api/new_task/[task_type].ts
@@ -1,4 +1,5 @@
 import { getToken } from "next-auth/jwt";
+import OasstApiClient from "src/lib/oasst_api_client";
 import prisma from "src/lib/prismadb";
 
 /**
@@ -20,25 +21,10 @@ const handler = async (req, res) => {
     return;
   }
 
+  const oasstApiClient = new OasstApiClient(process.env.FASTAPI_URL, process.env.FASTAPI_KEY);
+
   // Fetch the new task.
-  //
-  // This needs to be refactored into an easier to use library.
-  const taskRes = await fetch(`${process.env.FASTAPI_URL}/api/v1/tasks/`, {
-    method: "POST",
-    headers: {
-      "X-API-Key": process.env.FASTAPI_KEY,
-      "Content-Type": "application/json",
-    },
-    body: JSON.stringify({
-      type: task_type,
-      user: {
-        id: token.sub,
-        display_name: token.name || token.email,
-        auth_method: "local",
-      },
-    }),
-  });
-  const task = await taskRes.json();
+  const task = await oasstApiClient.fetchTask(task_type, token);
 
   // Store the task and link it to the user..
   const registeredTask = await prisma.registeredTask.create({
@@ -53,16 +39,7 @@ const handler = async (req, res) => {
   });
 
   // Update the backend with our Task ID
-  await fetch(`${process.env.FASTAPI_URL}/api/v1/tasks/${task.id}/ack`, {
-    method: "POST",
-    headers: {
-      "X-API-Key": process.env.FASTAPI_KEY,
-      "Content-Type": "application/json",
-    },
-    body: JSON.stringify({
-      message_id: registeredTask.id,
-    }),
-  });
+  await oasstApiClient.ackTask(task.id, registeredTask.id);
 
   // Send the results to the client.
   res.status(200).json(registeredTask);
diff --git a/website/src/pages/api/update_task.ts b/website/src/pages/api/update_task.ts
index 9582040b..2d371354 100644
--- a/website/src/pages/api/update_task.ts
+++ b/website/src/pages/api/update_task.ts
@@ -36,6 +36,7 @@ const handler = async (req, res) => {
 
   // Send the interaction to the Task Backend.  This automatically fetches the
   // next task in the sequence (or the done task).
+  // TODO(#353): Move this into OasstApiClient.
   const interactionRes = await fetch(`${process.env.FASTAPI_URL}/api/v1/tasks/interaction`, {
     method: "POST",
     headers: {