diff --git a/packages/auth/src/interface-adapters/controllers/sign-in.controller.test.ts b/packages/auth/src/interface-adapters/controllers/sign-in.controller.test.ts
new file mode 100644
index 0000000..1959d02
--- /dev/null
+++ b/packages/auth/src/interface-adapters/controllers/sign-in.controller.test.ts
@@ -0,0 +1,51 @@
+import { beforeEach, describe, expect, it } from "vitest";
+import { authContainer } from "@/di/container";
+import { AUTH_SYMBOLS } from "@/di/symbols";
+import { MockUsersRepository } from "@/infrastructure/repositories/mock-users.repository";
+import { MockAuthenticationService } from "@/infrastructure/services/mock-authentication.service";
+import type { IUsersRepository } from "@/application/repositories/users-repository.interface";
+import type { IAuthenticationService } from "@/application/services/authentication-service.interface";
+import { InputParseError } from "@/entities/errors";
+import { signInController } from "./sign-in.controller";
+
+describe("signInController", () => {
+  let usersRepo: MockUsersRepository;
+  let authService: MockAuthenticationService;
+
+  beforeEach(() => {
+    if (authContainer.isBound(AUTH_SYMBOLS.IUsersRepository)) {
+      authContainer.unbind(AUTH_SYMBOLS.IUsersRepository);
+    }
+    if (authContainer.isBound(AUTH_SYMBOLS.IAuthenticationService)) {
+      authContainer.unbind(AUTH_SYMBOLS.IAuthenticationService);
+    }
+    usersRepo = new MockUsersRepository();
+    authService = new MockAuthenticationService(usersRepo);
+    authContainer
+      .bind<IUsersRepository>(AUTH_SYMBOLS.IUsersRepository)
+      .toConstantValue(usersRepo);
+    authContainer
+      .bind<IAuthenticationService>(AUTH_SYMBOLS.IAuthenticationService)
+      .toConstantValue(authService);
+  });
+
+  it("returns a cookie on valid credentials", async () => {
+    const cookie = await signInController({
+      username: "alice",
+      password: "password_alice",
+    });
+    expect(cookie.name).toBe("session");
+  });
+
+  it("throws InputParseError on missing username", async () => {
+    await expect(
+      signInController({ password: "anything" }),
+    ).rejects.toBeInstanceOf(InputParseError);
+  });
+
+  it("throws InputParseError on too-short password", async () => {
+    await expect(
+      signInController({ username: "alice", password: "abc" }),
+    ).rejects.toBeInstanceOf(InputParseError);
+  });
+});
diff --git a/packages/auth/src/interface-adapters/controllers/sign-in.controller.ts b/packages/auth/src/interface-adapters/controllers/sign-in.controller.ts
new file mode 100644
index 0000000..a6fd143
--- /dev/null
+++ b/packages/auth/src/interface-adapters/controllers/sign-in.controller.ts
@@ -0,0 +1,21 @@
+import { z } from "zod";
+
+import { InputParseError } from "../../entities/errors";
+import type { Cookie } from "../../entities/cookie";
+import { signInUseCase } from "../../application/use-cases/sign-in.use-case";
+
+const inputSchema = z.object({
+  username: z.string().min(3).max(31),
+  password: z.string().min(6).max(255),
+});
+
+export async function signInController(
+  input: Partial<z.infer<typeof inputSchema>>,
+): Promise<Cookie> {
+  const parsed = inputSchema.safeParse(input);
+  if (!parsed.success) {
+    throw new InputParseError("Invalid sign-in input", { cause: parsed.error });
+  }
+  const { cookie } = await signInUseCase(parsed.data);
+  return cookie;
+}
diff --git a/packages/auth/src/interface-adapters/controllers/sign-out.controller.test.ts b/packages/auth/src/interface-adapters/controllers/sign-out.controller.test.ts
new file mode 100644
index 0000000..29dd561
--- /dev/null
+++ b/packages/auth/src/interface-adapters/controllers/sign-out.controller.test.ts
@@ -0,0 +1,40 @@
+import { beforeEach, describe, expect, it } from "vitest";
+import { authContainer } from "@/di/container";
+import { AUTH_SYMBOLS } from "@/di/symbols";
+import { MockUsersRepository } from "@/infrastructure/repositories/mock-users.repository";
+import { MockAuthenticationService } from "@/infrastructure/services/mock-authentication.service";
+import type { IUsersRepository } from "@/application/repositories/users-repository.interface";
+import type { IAuthenticationService } from "@/application/services/authentication-service.interface";
+import { InputParseError } from "@/entities/errors";
+import { signOutController } from "./sign-out.controller";
+
+describe("signOutController", () => {
+  beforeEach(() => {
+    if (authContainer.isBound(AUTH_SYMBOLS.IUsersRepository)) {
+      authContainer.unbind(AUTH_SYMBOLS.IUsersRepository);
+    }
+    if (authContainer.isBound(AUTH_SYMBOLS.IAuthenticationService)) {
+      authContainer.unbind(AUTH_SYMBOLS.IAuthenticationService);
+    }
+    const usersRepo = new MockUsersRepository();
+    const authService = new MockAuthenticationService(usersRepo);
+    authContainer
+      .bind<IUsersRepository>(AUTH_SYMBOLS.IUsersRepository)
+      .toConstantValue(usersRepo);
+    authContainer
+      .bind<IAuthenticationService>(AUTH_SYMBOLS.IAuthenticationService)
+      .toConstantValue(authService);
+  });
+
+  it("returns a blank cookie", async () => {
+    const cookie = await signOutController("session_anything");
+    expect(cookie.name).toBe("session");
+    expect(cookie.value).toBe("");
+  });
+
+  it("throws InputParseError when sessionId is missing", async () => {
+    await expect(signOutController(undefined)).rejects.toBeInstanceOf(
+      InputParseError,
+    );
+  });
+});
diff --git a/packages/auth/src/interface-adapters/controllers/sign-out.controller.ts b/packages/auth/src/interface-adapters/controllers/sign-out.controller.ts
new file mode 100644
index 0000000..7017f57
--- /dev/null
+++ b/packages/auth/src/interface-adapters/controllers/sign-out.controller.ts
@@ -0,0 +1,13 @@
+import { InputParseError } from "../../entities/errors";
+import type { Cookie } from "../../entities/cookie";
+import { signOutUseCase } from "../../application/use-cases/sign-out.use-case";
+
+export async function signOutController(
+  sessionId: string | undefined,
+): Promise<Cookie> {
+  if (!sessionId) {
+    throw new InputParseError("Must provide a session ID");
+  }
+  const { blankCookie } = await signOutUseCase(sessionId);
+  return blankCookie;
+}
diff --git a/packages/auth/src/interface-adapters/controllers/sign-up.controller.test.ts b/packages/auth/src/interface-adapters/controllers/sign-up.controller.test.ts
new file mode 100644
index 0000000..04d2e45
--- /dev/null
+++ b/packages/auth/src/interface-adapters/controllers/sign-up.controller.test.ts
@@ -0,0 +1,50 @@
+import { beforeEach, describe, expect, it } from "vitest";
+import { authContainer } from "@/di/container";
+import { AUTH_SYMBOLS } from "@/di/symbols";
+import { MockUsersRepository } from "@/infrastructure/repositories/mock-users.repository";
+import { MockAuthenticationService } from "@/infrastructure/services/mock-authentication.service";
+import type { IUsersRepository } from "@/application/repositories/users-repository.interface";
+import type { IAuthenticationService } from "@/application/services/authentication-service.interface";
+import { InputParseError } from "@/entities/errors";
+import { signUpController } from "./sign-up.controller";
+
+describe("signUpController", () => {
+  let usersRepo: MockUsersRepository;
+  let authService: MockAuthenticationService;
+
+  beforeEach(() => {
+    if (authContainer.isBound(AUTH_SYMBOLS.IUsersRepository)) {
+      authContainer.unbind(AUTH_SYMBOLS.IUsersRepository);
+    }
+    if (authContainer.isBound(AUTH_SYMBOLS.IAuthenticationService)) {
+      authContainer.unbind(AUTH_SYMBOLS.IAuthenticationService);
+    }
+    usersRepo = new MockUsersRepository();
+    authService = new MockAuthenticationService(usersRepo);
+    authContainer
+      .bind<IUsersRepository>(AUTH_SYMBOLS.IUsersRepository)
+      .toConstantValue(usersRepo);
+    authContainer
+      .bind<IAuthenticationService>(AUTH_SYMBOLS.IAuthenticationService)
+      .toConstantValue(authService);
+  });
+
+  it("creates a new user when passwords match", async () => {
+    const result = await signUpController({
+      username: "carol",
+      password: "secret_password",
+      confirmPassword: "secret_password",
+    });
+    expect(result.user.username).toBe("carol");
+  });
+
+  it("throws InputParseError when passwords do not match", async () => {
+    await expect(
+      signUpController({
+        username: "dave",
+        password: "secret_password",
+        confirmPassword: "different_password",
+      }),
+    ).rejects.toBeInstanceOf(InputParseError);
+  });
+});
diff --git a/packages/auth/src/interface-adapters/controllers/sign-up.controller.ts b/packages/auth/src/interface-adapters/controllers/sign-up.controller.ts
new file mode 100644
index 0000000..8455cd4
--- /dev/null
+++ b/packages/auth/src/interface-adapters/controllers/sign-up.controller.ts
@@ -0,0 +1,35 @@
+import { z } from "zod";
+
+import { InputParseError } from "../../entities/errors";
+import { signUpUseCase } from "../../application/use-cases/sign-up.use-case";
+
+const inputSchema = z
+  .object({
+    username: z.string().min(3).max(31),
+    password: z.string().min(6).max(255),
+    confirmPassword: z.string().min(6).max(255),
+  })
+  .superRefine(({ password, confirmPassword }, ctx) => {
+    if (confirmPassword !== password) {
+      ctx.addIssue({
+        code: "custom",
+        message: "The passwords did not match",
+        path: ["password"],
+      });
+      ctx.addIssue({
+        code: "custom",
+        message: "The passwords did not match",
+        path: ["confirmPassword"],
+      });
+    }
+  });
+
+export async function signUpController(
+  input: Partial<z.infer<typeof inputSchema>>,
+): Promise<ReturnType<typeof signUpUseCase>> {
+  const parsed = inputSchema.safeParse(input);
+  if (!parsed.success) {
+    throw new InputParseError("Invalid sign-up input", { cause: parsed.error });
+  }
+  return await signUpUseCase(parsed.data);
+}