diff --git a/desktop/src/shared/api/onboardingAccountStubs.test.mjs b/desktop/src/shared/api/onboardingAccountStubs.test.mjs
new file mode 100644
index 000000000..d49ad1ae1
--- /dev/null
+++ b/desktop/src/shared/api/onboardingAccountStubs.test.mjs
@@ -0,0 +1,119 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  connectInvitedCommunity,
+  createCommunity,
+  isValidEmail,
+  listInvitedCommunities,
+  logIn,
+  MIN_PASSWORD_LENGTH,
+  OnboardingAccountError,
+  sendCommunityInvites,
+  signUp,
+} from "./onboardingAccountStubs.ts";
+
+test("isValidEmail accepts plausible addresses and rejects junk", () => {
+  assert.equal(isValidEmail("cynthia@example.com"), true);
+  assert.equal(isValidEmail("  padded@example.com  "), true);
+  assert.equal(isValidEmail("no-at-sign.example.com"), false);
+  assert.equal(isValidEmail("missing@tld"), false);
+  assert.equal(isValidEmail("spaces in@example.com"), false);
+  assert.equal(isValidEmail(""), false);
+});
+
+test("signUp resolves for a valid email and strong-enough password", async () => {
+  const result = await signUp({
+    email: "cynthia@example.com",
+    password: "a".repeat(MIN_PASSWORD_LENGTH),
+  });
+  assert.deepEqual(result, { ok: true });
+});
+
+test("signUp rejects an invalid email with a stable error code", async () => {
+  await assert.rejects(
+    signUp({ email: "not-an-email", password: "long-enough-password" }),
+    (error) =>
+      error instanceof OnboardingAccountError && error.code === "email_invalid",
+  );
+});
+
+test("signUp rejects a short password with password_weak", async () => {
+  await assert.rejects(
+    signUp({
+      email: "cynthia@example.com",
+      password: "a".repeat(MIN_PASSWORD_LENGTH - 1),
+    }),
+    (error) =>
+      error instanceof OnboardingAccountError && error.code === "password_weak",
+  );
+});
+
+test("logIn resolves for a plausible credential shape", async () => {
+  assert.deepEqual(
+    await logIn({ email: "cynthia@example.com", password: "hunter22" }),
+    { ok: true },
+  );
+});
+
+test("logIn rejects bad shapes with credentials_invalid", async () => {
+  for (const attempt of [
+    { email: "not-an-email", password: "hunter22" },
+    { email: "cynthia@example.com", password: "" },
+  ]) {
+    await assert.rejects(
+      logIn(attempt),
+      (error) =>
+        error instanceof OnboardingAccountError &&
+        error.code === "credentials_invalid",
+    );
+  }
+});
+
+test("listInvitedCommunities returns fixture invites with the fields the hub renders", async () => {
+  const invites = await listInvitedCommunities();
+  assert.ok(invites.length >= 1);
+  for (const invite of invites) {
+    assert.equal(typeof invite.inviteId, "string");
+    assert.equal(typeof invite.name, "string");
+    assert.equal(typeof invite.host, "string");
+    assert.match(invite.relayWsUrl, /^wss?:\/\//);
+  }
+});
+
+test("connectInvitedCommunity resolves a known invite and rejects an unknown one", async () => {
+  const [invite] = await listInvitedCommunities();
+  const result = await connectInvitedCommunity(invite.inviteId);
+  assert.equal(result.relayWsUrl, invite.relayWsUrl);
+
+  await assert.rejects(
+    connectInvitedCommunity("definitely-not-an-invite"),
+    (error) => error instanceof OnboardingAccountError,
+  );
+});
+
+test("createCommunity slugs the relay host from the name", async () => {
+  const created = await createCommunity({
+    name: "The Land of Ooo",
+    description: "A magical workspace",
+  });
+  assert.equal(created.name, "The Land of Ooo");
+  assert.equal(
+    created.relayWsUrl,
+    "wss://the-land-of-ooo.communities.buzz.xyz",
+  );
+});
+
+test("createCommunity rejects an empty name", async () => {
+  await assert.rejects(
+    createCommunity({ name: "   ", description: "" }),
+    (error) => error instanceof OnboardingAccountError,
+  );
+});
+
+test("sendCommunityInvites counts only valid emails", async () => {
+  const result = await sendCommunityInvites({
+    emails: ["kalvin@example.com", "not-an-email", "wes@example.com"],
+  });
+  assert.deepEqual(result, { sent: 2 });
+});
diff --git a/desktop/src/shared/api/onboardingAccountStubs.ts b/desktop/src/shared/api/onboardingAccountStubs.ts
new file mode 100644
index 000000000..b7611877d
--- /dev/null
+++ b/desktop/src/shared/api/onboardingAccountStubs.ts
@@ -0,0 +1,176 @@
+/**
+ * Frontend-only stubs for the onboarding v2 "standard flow" backend seams.
+ *
+ * The signup-first onboarding (see PLANS/ONBOARDING_V2_STANDARD_FLOW.md in the
+ * workspace) needs endpoints that do not exist on the relay yet: email/password
+ * accounts, invitee-bound community invites, in-app community creation, and
+ * email invites. This module is the typed contract for those endpoints; every
+ * function currently resolves fixture data after a short delay so the whole
+ * flow is walkable in the UI with zero backend changes.
+ *
+ * Engineers: replace the bodies (not the signatures) when the real endpoints
+ * land. Error cases are expressed as thrown `OnboardingAccountError`s with
+ * stable `code` values the UI already branches on.
+ */
+
+export type OnboardingAccountErrorCode =
+  | "email_invalid"
+  | "email_taken"
+  | "password_weak"
+  | "credentials_invalid"
+  | "community_name_taken"
+  | "network";
+
+export class OnboardingAccountError extends Error {
+  readonly code: OnboardingAccountErrorCode;
+
+  constructor(code: OnboardingAccountErrorCode, message: string) {
+    super(message);
+    this.name = "OnboardingAccountError";
+    this.code = code;
+  }
+}
+
+export type InvitedCommunity = {
+  /** Opaque invite identifier used to claim the invite. */
+  inviteId: string;
+  /** Human-readable community name, e.g. "The Land of Ooo". */
+  name: string;
+  /** Community hostname shown under the name in the hub list. */
+  host: string;
+  /** Relay websocket URL to connect to on accept. */
+  relayWsUrl: string;
+};
+
+export type CreatedCommunity = {
+  name: string;
+  relayWsUrl: string;
+};
+
+const EMAIL_PATTERN = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
+/** Minimum password length enforced client-side until the backend owns policy. */
+export const MIN_PASSWORD_LENGTH = 8;
+
+function delay(ms: number) {
+  return new Promise<void>((resolve) => setTimeout(resolve, ms));
+}
+
+/** Client-side email shape check shared by the signup and login forms. */
+export function isValidEmail(email: string): boolean {
+  return EMAIL_PATTERN.test(email.trim());
+}
+
+/**
+ * Create an email/password account. In the real flow this pairs the account
+ * with the freshly generated identity key; the stub only validates shape.
+ */
+export async function signUp({
+  email,
+  password,
+}: {
+  email: string;
+  password: string;
+}): Promise<{ ok: true }> {
+  await delay(400);
+  if (!isValidEmail(email)) {
+    throw new OnboardingAccountError(
+      "email_invalid",
+      "Enter a valid email address.",
+    );
+  }
+  if (password.length < MIN_PASSWORD_LENGTH) {
+    throw new OnboardingAccountError(
+      "password_weak",
+      `Password must be at least ${MIN_PASSWORD_LENGTH} characters.`,
+    );
+  }
+  return { ok: true };
+}
+
+/** Log in a returning email/password user. Stub accepts any valid shape. */
+export async function logIn({
+  email,
+  password,
+}: {
+  email: string;
+  password: string;
+}): Promise<{ ok: true }> {
+  await delay(400);
+  if (!isValidEmail(email) || password.length === 0) {
+    throw new OnboardingAccountError(
+      "credentials_invalid",
+      "Email or password is incorrect.",
+    );
+  }
+  return { ok: true };
+}
+
+/**
+ * Communities the current account has been invited to. Invites are bound to
+ * the invitee server-side, so onboarding can list them without a pasted link.
+ */
+export async function listInvitedCommunities(): Promise<InvitedCommunity[]> {
+  await delay(300);
+  return [
+    {
+      inviteId: "stub-invite-1",
+      name: "The Land of Ooo",
+      host: "land-of-ooo.communities.buzz.xyz",
+      relayWsUrl: "wss://land-of-ooo.communities.buzz.xyz",
+    },
+  ];
+}
+
+/** Accept an invitee-bound invite and return the relay to connect to. */
+export async function connectInvitedCommunity(
+  inviteId: string,
+): Promise<{ relayWsUrl: string }> {
+  await delay(300);
+  const invites = await listInvitedCommunities();
+  const invite = invites.find((candidate) => candidate.inviteId === inviteId);
+  if (!invite) {
+    throw new OnboardingAccountError("network", "Invite is no longer valid.");
+  }
+  return { relayWsUrl: invite.relayWsUrl };
+}
+
+/** Create a new hosted community from inside onboarding. */
+export async function createCommunity({
+  name,
+  description,
+  avatarUrl,
+}: {
+  name: string;
+  description: string;
+  avatarUrl?: string;
+}): Promise<CreatedCommunity> {
+  await delay(500);
+  void description;
+  void avatarUrl;
+  const trimmed = name.trim();
+  if (!trimmed) {
+    throw new OnboardingAccountError(
+      "community_name_taken",
+      "Enter a community name.",
+    );
+  }
+  const slug = trimmed
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, "-")
+    .replace(/^-+|-+$/g, "");
+  return {
+    name: trimmed,
+    relayWsUrl: `wss://${slug || "community"}.communities.buzz.xyz`,
+  };
+}
+
+/** Send email invites to join the newly created community. */
+export async function sendCommunityInvites({
+  emails,
+}: {
+  emails: string[];
+}): Promise<{ sent: number }> {
+  await delay(300);
+  const valid = emails.filter((email) => isValidEmail(email));
+  return { sent: valid.length };
+}