diff --git a/src/_shared/async-queue.ts b/src/_shared/async-queue.ts
new file mode 100644
index 0000000..5da5de2
--- /dev/null
+++ b/src/_shared/async-queue.ts
@@ -0,0 +1,62 @@
+export class AsyncQueue<T> implements AsyncIterableIterator<T> {
+	private readonly values: T[] = [];
+	private readonly waiters: Array<{
+		reject: (reason?: unknown) => void;
+		resolve: (value: IteratorResult<T>) => void;
+	}> = [];
+	private closed = false;
+	private error: unknown;
+
+	[Symbol.asyncIterator](): AsyncIterableIterator<T> {
+		return this;
+	}
+
+	next(): Promise<IteratorResult<T>> {
+		if (this.values.length) {
+			return Promise.resolve({ done: false, value: this.values.shift() as T });
+		}
+		if (this.error) return Promise.reject(this.error);
+		if (this.closed) return Promise.resolve({ done: true, value: undefined });
+
+		return new Promise((resolve, reject) => {
+			this.waiters.push({ reject, resolve });
+		});
+	}
+
+	return(): Promise<IteratorResult<T>> {
+		this.end();
+		return Promise.resolve({ done: true, value: undefined });
+	}
+
+	throw(error?: unknown): Promise<IteratorResult<T>> {
+		this.fail(error);
+		return Promise.reject(error);
+	}
+
+	push(value: T): void {
+		if (this.closed) return;
+		const waiter = this.waiters.shift();
+		if (waiter) {
+			waiter.resolve({ done: false, value });
+			return;
+		}
+		this.values.push(value);
+	}
+
+	end(): void {
+		if (this.closed) return;
+		this.closed = true;
+		for (const waiter of this.waiters.splice(0)) {
+			waiter.resolve({ done: true, value: undefined });
+		}
+	}
+
+	fail(error: unknown): void {
+		if (this.closed) return;
+		this.closed = true;
+		this.error = error;
+		for (const waiter of this.waiters.splice(0)) {
+			waiter.reject(error);
+		}
+	}
+}
diff --git a/src/capsule.ts b/src/capsule.ts
index 195ddd4..dce0485 100644
--- a/src/capsule.ts
+++ b/src/capsule.ts
@@ -4,8 +4,11 @@ import {
 	type OperationQueryParams,
 	WrennClient,
 } from "./client.js";
+import { CommandManager } from "./commands.js";
 import type { ClientConfig } from "./config.js";
 import { TimeoutError, WrennError } from "./exceptions.js";
+import { FileManager } from "./files.js";
+import { PtyManager } from "./pty.js";
 
 export type CapsuleInfo = OperationJsonResponse<"getCapsule", 200>;
 export type CapsuleMetrics = OperationJsonResponse<"getCapsuleMetrics", 200>;
@@ -88,6 +91,9 @@ function delay(ms: number, signal?: AbortSignal): Promise<void> {
 export class Capsule {
 	readonly id: string;
 	readonly client: WrennClient;
+	readonly commands: CommandManager;
+	readonly files: FileManager;
+	readonly pty: PtyManager;
 
 	/**
 	 * Wraps an existing capsule ID without fetching or creating remote resources.
@@ -98,6 +104,9 @@ export class Capsule {
 	constructor(id: string, opts?: ClientConfig) {
 		this.id = id;
 		this.client = new WrennClient(opts);
+		this.commands = new CommandManager(id, this.client);
+		this.files = new FileManager(id, this.client);
+		this.pty = new PtyManager(id, this.client);
 	}
 
 	static create(opts?: CapsuleCreateOptions): Promise<Capsule>;
diff --git a/src/client.ts b/src/client.ts
index 550dab6..6cdb35d 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -78,7 +78,7 @@ function createFileFormData(input: FileUploadInput): FormData {
 	const formData = new FormData();
 	formData.append("path", input.path);
 	if (typeof input.file === "string") {
-		formData.append("file", input.file);
+		formData.append("file", new Blob([input.file]), input.filename ?? "file");
 	} else {
 		if (input.filename) {
 			formData.append("file", input.file, input.filename);
diff --git a/src/commands.ts b/src/commands.ts
new file mode 100644
index 0000000..ff467f2
--- /dev/null
+++ b/src/commands.ts
@@ -0,0 +1,139 @@
+import { AsyncQueue } from "./_shared/async-queue.js";
+import type { WsConnection } from "./_shared/websocket.js";
+import type {
+	OperationJsonBody,
+	OperationJsonResponse,
+	WrennClient,
+} from "./client.js";
+
+export type CommandResult = OperationJsonResponse<"execCommand", 200>;
+export type BackgroundProcess = OperationJsonResponse<"execCommand", 202>;
+export type ProcessList = OperationJsonResponse<"listProcesses", 200>;
+
+export interface CommandOptions {
+	args?: string[];
+	timeoutSec?: number;
+}
+
+export interface BackgroundCommandOptions extends CommandOptions {
+	tag?: string;
+	envs?: Record<string, string>;
+	cwd?: string;
+}
+
+export interface CommandStreamOptions {
+	args?: string[];
+	timeoutMs?: number;
+}
+
+export interface CommandStreamEvent {
+	type: string;
+	[key: string]: unknown;
+}
+
+const DEFAULT_COMMAND_TIMEOUT_SEC = 30;
+
+function commandBody(
+	cmd: string,
+	background: boolean,
+	opts?: BackgroundCommandOptions,
+): OperationJsonBody<"execCommand"> {
+	const body: OperationJsonBody<"execCommand"> = {
+		background,
+		cmd,
+		timeout_sec: opts?.timeoutSec ?? DEFAULT_COMMAND_TIMEOUT_SEC,
+	};
+	if (opts?.args) body.args = opts.args;
+	if (opts?.tag) body.tag = opts.tag;
+	if (opts?.envs) body.envs = opts.envs;
+	if (opts?.cwd) body.cwd = opts.cwd;
+	return body;
+}
+
+function isTerminalEvent(event: CommandStreamEvent): boolean {
+	return event.type === "exit" || event.type === "error";
+}
+
+/** User-friendly command execution API bound to one capsule. */
+export class CommandManager {
+	constructor(
+		private readonly capsuleId: string,
+		private readonly client: WrennClient,
+	) {}
+
+	exec(cmd: string, opts?: CommandOptions): Promise<CommandResult> {
+		return this.client.capsules.exec(
+			this.capsuleId,
+			commandBody(cmd, false, opts),
+		) as Promise<CommandResult>;
+	}
+
+	start(
+		cmd: string,
+		opts?: BackgroundCommandOptions,
+	): Promise<BackgroundProcess> {
+		return this.client.capsules.exec(
+			this.capsuleId,
+			commandBody(cmd, true, opts),
+		) as Promise<BackgroundProcess>;
+	}
+
+	list(): Promise<ProcessList> {
+		return this.client.capsules.listProcesses(this.capsuleId);
+	}
+
+	kill(selector: string, signal?: "SIGKILL" | "SIGTERM"): Promise<void> {
+		const params = signal ? { signal } : undefined;
+		return this.client.capsules.killProcess(this.capsuleId, selector, params);
+	}
+
+	async *stream(
+		cmd: string,
+		opts?: CommandStreamOptions,
+	): AsyncGenerator<CommandStreamEvent> {
+		const queue = new AsyncQueue<CommandStreamEvent>();
+		let connection: WsConnection | undefined;
+		const socketOpts: Parameters<typeof this.client.capsules.execStream>[1] = {
+			onClose: () => queue.end(),
+			onError: (error) => queue.fail(error),
+			onMessage: (message) => {
+				const event = message as CommandStreamEvent;
+				queue.push(event);
+				if (isTerminalEvent(event)) queue.end();
+			},
+		};
+		if (opts?.timeoutMs !== undefined) socketOpts.timeoutMs = opts.timeoutMs;
+
+		connection = await this.client.capsules.execStream(
+			this.capsuleId,
+			socketOpts,
+		);
+
+		const start: CommandStreamEvent = { cmd, type: "start" };
+		if (opts?.args) start.args = opts.args;
+		connection.send(start);
+
+		try {
+			yield* queue;
+		} finally {
+			if (!connection.isClosed) connection.close();
+		}
+	}
+
+	streamProcess(
+		selector: string,
+		opts?: Pick<CommandStreamOptions, "timeoutMs">,
+	): Promise<WsConnection> {
+		const socketOpts: Parameters<
+			typeof this.client.capsules.connectProcess
+		>[2] = {
+			onMessage: () => undefined,
+		};
+		if (opts?.timeoutMs !== undefined) socketOpts.timeoutMs = opts.timeoutMs;
+		return this.client.capsules.connectProcess(
+			this.capsuleId,
+			selector,
+			socketOpts,
+		);
+	}
+}
diff --git a/src/files.ts b/src/files.ts
new file mode 100644
index 0000000..7a0d75c
--- /dev/null
+++ b/src/files.ts
@@ -0,0 +1,80 @@
+import type { OperationJsonResponse, WrennClient } from "./client.js";
+
+export type FileList = OperationJsonResponse<"listDir", 200>;
+export type MakeDirectoryResult = OperationJsonResponse<"makeDir", 200>;
+
+export interface ListFilesOptions {
+	depth?: number;
+}
+
+export type FileContent = Blob | string | Uint8Array | ArrayBuffer;
+
+async function streamToBuffer(
+	stream: ReadableStream<Uint8Array>,
+): Promise<Buffer> {
+	const chunks: Buffer[] = [];
+	for await (const chunk of stream) {
+		chunks.push(Buffer.from(chunk));
+	}
+	return Buffer.concat(chunks);
+}
+
+function uploadContent(content: FileContent): Blob | string {
+	if (typeof content === "string" || content instanceof Blob) return content;
+	if (content instanceof ArrayBuffer) return new Blob([content]);
+	const buffer = new ArrayBuffer(content.byteLength);
+	new Uint8Array(buffer).set(content);
+	return new Blob([buffer]);
+}
+
+/** User-friendly file API bound to one capsule. */
+export class FileManager {
+	constructor(
+		private readonly capsuleId: string,
+		private readonly client: WrennClient,
+	) {}
+
+	async read(path: string): Promise<Buffer> {
+		return streamToBuffer(
+			await this.client.files.download(this.capsuleId, { path }),
+		);
+	}
+
+	write(path: string, content: FileContent): Promise<void> {
+		return this.client.files.upload(this.capsuleId, {
+			file: uploadContent(content),
+			path,
+		});
+	}
+
+	list(path: string, opts?: ListFilesOptions): Promise<FileList> {
+		return this.client.files.list(this.capsuleId, {
+			depth: opts?.depth ?? 1,
+			path,
+		});
+	}
+
+	mkdir(path: string): Promise<MakeDirectoryResult> {
+		return this.client.files.mkdir(this.capsuleId, { path });
+	}
+
+	remove(path: string): Promise<void> {
+		return this.client.files.remove(this.capsuleId, { path });
+	}
+
+	async *downloadStream(path: string): AsyncGenerator<Buffer> {
+		const stream = await this.client.files.streamDownload(this.capsuleId, {
+			path,
+		});
+		for await (const chunk of stream) {
+			yield Buffer.from(chunk);
+		}
+	}
+
+	uploadStream(path: string, content: FileContent): Promise<void> {
+		return this.client.files.streamUpload(this.capsuleId, {
+			file: uploadContent(content),
+			path,
+		});
+	}
+}
diff --git a/src/index.ts b/src/index.ts
index 021015f..0395fcb 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -31,6 +31,16 @@ export {
 	UsersResource,
 	WrennClient,
 } from "./client.js";
+export type {
+	BackgroundCommandOptions,
+	BackgroundProcess,
+	CommandOptions,
+	CommandResult,
+	CommandStreamEvent,
+	CommandStreamOptions,
+	ProcessList,
+} from "./commands.js";
+export { CommandManager } from "./commands.js";
 export type { ClientConfig, ResolvedClientConfig } from "./config.js";
 export {
 	DEFAULT_BASE_URL,
@@ -53,3 +63,12 @@ export {
 	throwErrorFromResponse,
 	WrennError,
 } from "./exceptions.js";
+export type {
+	FileContent,
+	FileList,
+	ListFilesOptions,
+	MakeDirectoryResult,
+} from "./files.js";
+export { FileManager } from "./files.js";
+export type { PtyEvent, PtyStartOptions } from "./pty.js";
+export { PtyManager, PtySession } from "./pty.js";
diff --git a/src/pty.ts b/src/pty.ts
new file mode 100644
index 0000000..b7b094f
--- /dev/null
+++ b/src/pty.ts
@@ -0,0 +1,98 @@
+import { AsyncQueue } from "./_shared/async-queue.js";
+import type { WsConnection } from "./_shared/websocket.js";
+import type { WrennClient } from "./client.js";
+
+export interface PtyStartOptions {
+	cmd?: string;
+	args?: string[];
+	cols?: number;
+	rows?: number;
+	envs?: Record<string, string>;
+	cwd?: string;
+	user?: string;
+	timeoutMs?: number;
+}
+
+export interface PtyEvent {
+	type: string;
+	[key: string]: unknown;
+}
+
+export class PtySession {
+	readonly events: AsyncIterableIterator<PtyEvent>;
+
+	constructor(
+		private readonly connection: WsConnection,
+		queue: AsyncQueue<PtyEvent>,
+	) {
+		this.events = queue;
+	}
+
+	input(data: string | Uint8Array): void {
+		this.connection.send({
+			data: Buffer.from(data).toString("base64"),
+			type: "input",
+		});
+	}
+
+	resize(cols: number, rows: number): void {
+		this.connection.send({ cols, rows, type: "resize" });
+	}
+
+	kill(): void {
+		this.connection.send({ type: "kill" });
+	}
+
+	close(): void {
+		this.connection.close();
+	}
+}
+
+/** Interactive terminal API bound to one capsule. */
+export class PtyManager {
+	constructor(
+		private readonly capsuleId: string,
+		private readonly client: WrennClient,
+	) {}
+
+	async start(opts?: PtyStartOptions): Promise<PtySession> {
+		const session = await this.open(opts?.timeoutMs);
+		const message: PtyEvent = { type: "start" };
+		if (opts?.cmd) message.cmd = opts.cmd;
+		if (opts?.args) message.args = opts.args;
+		if (opts?.cols) message.cols = opts.cols;
+		if (opts?.rows) message.rows = opts.rows;
+		if (opts?.envs) message.envs = opts.envs;
+		if (opts?.cwd) message.cwd = opts.cwd;
+		if (opts?.user) message.user = opts.user;
+		session.connection.send(message);
+		return session.value;
+	}
+
+	async connect(
+		tag: string,
+		opts?: Pick<PtyStartOptions, "timeoutMs">,
+	): Promise<PtySession> {
+		const session = await this.open(opts?.timeoutMs);
+		session.connection.send({ tag, type: "connect" });
+		return session.value;
+	}
+
+	private async open(timeoutMs?: number): Promise<{
+		connection: WsConnection;
+		value: PtySession;
+	}> {
+		const queue = new AsyncQueue<PtyEvent>();
+		const socketOpts: Parameters<typeof this.client.capsules.ptySession>[1] = {
+			onClose: () => queue.end(),
+			onError: (error) => queue.fail(error),
+			onMessage: (message) => queue.push(message as PtyEvent),
+		};
+		if (timeoutMs !== undefined) socketOpts.timeoutMs = timeoutMs;
+		const connection = await this.client.capsules.ptySession(
+			this.capsuleId,
+			socketOpts,
+		);
+		return { connection, value: new PtySession(connection, queue) };
+	}
+}
diff --git a/tests/client.test.ts b/tests/client.test.ts
index 169dbf9..8fc8ea4 100644
--- a/tests/client.test.ts
+++ b/tests/client.test.ts
@@ -323,6 +323,9 @@ describe("WrennClient", () => {
 			url: "https://api.example.com/v1/capsules/cap_1/files/write",
 		});
 		expect(calls.at(-1)?.init.body).toBeInstanceOf(FormData);
+		expect((calls.at(-1)?.init.body as FormData).get("file")).toBeInstanceOf(
+			Blob,
+		);
 		await client.files.download("cap_1", {} as never);
 		expectLastCall(calls, {
 			body: {},
diff --git a/tests/commands.test.ts b/tests/commands.test.ts
new file mode 100644
index 0000000..8f8efe4
--- /dev/null
+++ b/tests/commands.test.ts
@@ -0,0 +1,116 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { Capsule } from "../src/capsule.js";
+
+describe("CommandManager", () => {
+	it("executes foreground commands through the capsule client", async () => {
+		const capsule = new Capsule("cap_1", {
+			baseUrl: "https://api.example.com",
+		});
+		const exec = vi.spyOn(capsule.client.capsules, "exec").mockResolvedValue({
+			exit_code: 0,
+			stdout: "ok\n",
+		});
+
+		await expect(
+			capsule.commands.exec("node", {
+				args: ["--version"],
+				timeoutSec: 5,
+			}),
+		).resolves.toMatchObject({ stdout: "ok\n" });
+
+		expect(exec).toHaveBeenCalledWith("cap_1", {
+			args: ["--version"],
+			background: false,
+			cmd: "node",
+			timeout_sec: 5,
+		});
+	});
+
+	it("starts, lists, and kills background processes", async () => {
+		const capsule = new Capsule("cap_1", {
+			baseUrl: "https://api.example.com",
+		});
+		const exec = vi.spyOn(capsule.client.capsules, "exec").mockResolvedValue({
+			pid: 123,
+			tag: "worker",
+		});
+		const listProcesses = vi
+			.spyOn(capsule.client.capsules, "listProcesses")
+			.mockResolvedValue({ processes: [{ pid: 123, tag: "worker" }] });
+		const killProcess = vi
+			.spyOn(capsule.client.capsules, "killProcess")
+			.mockResolvedValue(undefined);
+
+		await expect(
+			capsule.commands.start("sleep", {
+				args: ["60"],
+				cwd: "/tmp",
+				envs: { A: "1" },
+				tag: "worker",
+			}),
+		).resolves.toMatchObject({ tag: "worker" });
+		await expect(capsule.commands.list()).resolves.toMatchObject({
+			processes: [{ tag: "worker" }],
+		});
+		await expect(
+			capsule.commands.kill("worker", "SIGTERM"),
+		).resolves.toBeUndefined();
+
+		expect(exec).toHaveBeenCalledWith("cap_1", {
+			args: ["60"],
+			background: true,
+			cmd: "sleep",
+			cwd: "/tmp",
+			envs: { A: "1" },
+			tag: "worker",
+			timeout_sec: 30,
+		});
+		expect(listProcesses).toHaveBeenCalledWith("cap_1");
+		expect(killProcess).toHaveBeenCalledWith("cap_1", "worker", {
+			signal: "SIGTERM",
+		});
+	});
+
+	it("streams command events over the exec WebSocket", async () => {
+		const capsule = new Capsule("cap_1", {
+			baseUrl: "https://api.example.com",
+		});
+		const sent: unknown[] = [];
+		let onMessage: ((message: unknown) => void) | undefined;
+		vi.spyOn(capsule.client.capsules, "execStream").mockImplementation(
+			async (_id, opts) => {
+				onMessage = opts.onMessage;
+				return {
+					close: vi.fn(),
+					get isClosed() {
+						return false;
+					},
+					send: (message: unknown) => sent.push(message),
+				} as never;
+			},
+		);
+
+		const events = capsule.commands.stream("printf", { args: ["hello"] });
+		const first = events.next();
+		await vi.waitFor(() => expect(sent).toHaveLength(1));
+		expect(sent).toEqual([{ args: ["hello"], cmd: "printf", type: "start" }]);
+
+		onMessage?.({ data: "hello", type: "stdout" });
+		await expect(first).resolves.toEqual({
+			done: false,
+			value: { data: "hello", type: "stdout" },
+		});
+
+		const done = events.next();
+		onMessage?.({ exit_code: 0, type: "exit" });
+		await expect(done).resolves.toEqual({
+			done: false,
+			value: { exit_code: 0, type: "exit" },
+		});
+		await expect(events.next()).resolves.toEqual({
+			done: true,
+			value: undefined,
+		});
+	});
+});
diff --git a/tests/files.test.ts b/tests/files.test.ts
new file mode 100644
index 0000000..e5e2a71
--- /dev/null
+++ b/tests/files.test.ts
@@ -0,0 +1,92 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { Capsule } from "../src/capsule.js";
+
+function streamFrom(text: string): ReadableStream<Uint8Array> {
+	return new ReadableStream({
+		start(controller) {
+			controller.enqueue(Buffer.from(text));
+			controller.close();
+		},
+	});
+}
+
+describe("FileManager", () => {
+	it("reads and writes files through the capsule file client", async () => {
+		const capsule = new Capsule("cap_1", {
+			baseUrl: "https://api.example.com",
+		});
+		const download = vi
+			.spyOn(capsule.client.files, "download")
+			.mockResolvedValue(streamFrom("hello"));
+		const upload = vi
+			.spyOn(capsule.client.files, "upload")
+			.mockResolvedValue(undefined);
+
+		await expect(capsule.files.read("/tmp/a.txt")).resolves.toEqual(
+			Buffer.from("hello"),
+		);
+		await expect(
+			capsule.files.write("/tmp/a.txt", "hello"),
+		).resolves.toBeUndefined();
+
+		expect(download).toHaveBeenCalledWith("cap_1", { path: "/tmp/a.txt" });
+		expect(upload).toHaveBeenCalledWith("cap_1", {
+			file: "hello",
+			path: "/tmp/a.txt",
+		});
+	});
+
+	it("maps directory operations", async () => {
+		const capsule = new Capsule("cap_1", {
+			baseUrl: "https://api.example.com",
+		});
+		const list = vi.spyOn(capsule.client.files, "list").mockResolvedValue({
+			entries: [{ name: "a.txt", path: "/tmp/a.txt", type: "file" }],
+		});
+		const mkdir = vi.spyOn(capsule.client.files, "mkdir").mockResolvedValue({
+			entry: { path: "/tmp/new", type: "directory" },
+		});
+		const remove = vi
+			.spyOn(capsule.client.files, "remove")
+			.mockResolvedValue(undefined);
+
+		await expect(
+			capsule.files.list("/tmp", { depth: 2 }),
+		).resolves.toMatchObject({
+			entries: [{ name: "a.txt" }],
+		});
+		await expect(capsule.files.mkdir("/tmp/new")).resolves.toMatchObject({
+			entry: { type: "directory" },
+		});
+		await expect(capsule.files.remove("/tmp/a.txt")).resolves.toBeUndefined();
+
+		expect(list).toHaveBeenCalledWith("cap_1", { depth: 2, path: "/tmp" });
+		expect(mkdir).toHaveBeenCalledWith("cap_1", { path: "/tmp/new" });
+		expect(remove).toHaveBeenCalledWith("cap_1", { path: "/tmp/a.txt" });
+	});
+
+	it("streams downloads as Buffer chunks and uploads streaming content", async () => {
+		const capsule = new Capsule("cap_1", {
+			baseUrl: "https://api.example.com",
+		});
+		vi.spyOn(capsule.client.files, "streamDownload").mockResolvedValue(
+			streamFrom("hello"),
+		);
+		const streamUpload = vi
+			.spyOn(capsule.client.files, "streamUpload")
+			.mockResolvedValue(undefined);
+
+		const chunks: Buffer[] = [];
+		for await (const chunk of capsule.files.downloadStream("/tmp/a.txt")) {
+			chunks.push(chunk);
+		}
+		await capsule.files.uploadStream("/tmp/a.txt", Buffer.from("hello"));
+
+		expect(Buffer.concat(chunks).toString()).toBe("hello");
+		expect(streamUpload).toHaveBeenCalledWith("cap_1", {
+			file: expect.any(Blob),
+			path: "/tmp/a.txt",
+		});
+	});
+});
diff --git a/tests/integration/capsule-features.integration.test.ts b/tests/integration/capsule-features.integration.test.ts
new file mode 100644
index 0000000..12316cc
--- /dev/null
+++ b/tests/integration/capsule-features.integration.test.ts
@@ -0,0 +1,180 @@
+import { describe, expect, it } from "vitest";
+
+import { Capsule, type CapsuleCreateOptions } from "../../src/capsule.js";
+import type { CommandStreamEvent } from "../../src/commands.js";
+import { DEFAULT_BASE_URL } from "../../src/config.js";
+import type { PtyEvent } from "../../src/pty.js";
+
+const baseUrl = process.env.WRENN_BASE_URL ?? DEFAULT_BASE_URL;
+const apiKey = process.env.WRENN_API_KEY;
+const template = process.env.WRENN_TEST_TEMPLATE ?? "minimal";
+const waitTimeoutMs = Number(process.env.WRENN_TEST_WAIT_TIMEOUT_MS ?? 120_000);
+const testTimeoutMs = waitTimeoutMs + 45_000;
+const describeWithApiKey = apiKey ? describe : describe.skip;
+
+const clientOpts = { apiKey, baseUrl } satisfies CapsuleCreateOptions;
+
+async function withLiveCapsule(
+	fn: (capsule: Capsule) => Promise<void>,
+): Promise<void> {
+	let capsule: Capsule | undefined;
+	try {
+		capsule = await Capsule.create(template, {
+			...clientOpts,
+			timeout_sec: 120,
+		});
+		await capsule.waitForReady({
+			intervalMs: 2_000,
+			timeoutMs: waitTimeoutMs,
+		});
+		await fn(capsule);
+	} finally {
+		if (capsule) {
+			await capsule.destroy().catch(() => undefined);
+		}
+	}
+}
+
+async function collectCommandEvents(
+	events: AsyncGenerator<CommandStreamEvent>,
+): Promise<CommandStreamEvent[]> {
+	const collected: CommandStreamEvent[] = [];
+	for await (const event of events) {
+		collected.push(event);
+		if (event.type === "exit" || event.type === "error") break;
+	}
+	return collected;
+}
+
+async function nextPtyEvent(
+	events: AsyncIterableIterator<PtyEvent>,
+): Promise<PtyEvent> {
+	const timeout = new Promise<never>((_, reject) => {
+		setTimeout(
+			() => reject(new Error("Timed out waiting for PTY event")),
+			15_000,
+		);
+	});
+	const result = await Promise.race([events.next(), timeout]);
+	if (result.done) throw new Error("PTY closed before next event");
+	return result.value;
+}
+
+describeWithApiKey("Phase 4 live integration", () => {
+	it(
+		"executes foreground, streaming, and background commands",
+		async () => {
+			await withLiveCapsule(async (capsule) => {
+				const result = await capsule.commands.exec("printf", {
+					args: ["phase4-command"],
+					timeoutSec: 10,
+				});
+				expect(result.exit_code).toBe(0);
+				expect(result.stdout).toContain("phase4-command");
+
+				const streamEvents = await collectCommandEvents(
+					capsule.commands.stream("printf", { args: ["phase4-stream"] }),
+				);
+				expect(streamEvents.some((event) => event.type === "stdout")).toBe(
+					true,
+				);
+				expect(streamEvents.at(-1)).toMatchObject({ type: "exit" });
+
+				const tag = `phase4-${Date.now()}`;
+				const process = await capsule.commands.start("sleep", {
+					args: ["60"],
+					tag,
+				});
+				expect(process.tag).toBe(tag);
+
+				const processes = await capsule.commands.list();
+				expect(processes.processes?.some((entry) => entry.tag === tag)).toBe(
+					true,
+				);
+
+				await expect(
+					capsule.commands.kill(tag, "SIGTERM"),
+				).resolves.toBeUndefined();
+			});
+		},
+		testTimeoutMs,
+	);
+
+	it(
+		"performs file read/write/list/remove and streaming transfers",
+		async () => {
+			await withLiveCapsule(async (capsule) => {
+				const dir = `/tmp/wrenn-phase4-${Date.now()}`;
+				const file = `${dir}/hello.txt`;
+				const streamFile = `${dir}/stream.txt`;
+
+				await capsule.files.mkdir(dir);
+				await capsule.files.write(file, "phase4-file");
+
+				const content = await capsule.files.read(file);
+				expect(content.toString()).toBe("phase4-file");
+
+				const listing = await capsule.files.list(dir, { depth: 1 });
+				expect(
+					listing.entries?.some((entry) => entry.name === "hello.txt"),
+				).toBe(true);
+
+				await capsule.files.uploadStream(
+					streamFile,
+					Buffer.from("phase4-stream-file"),
+				);
+				const chunks: Buffer[] = [];
+				for await (const chunk of capsule.files.downloadStream(streamFile)) {
+					chunks.push(chunk);
+				}
+				expect(Buffer.concat(chunks).toString()).toBe("phase4-stream-file");
+
+				await expect(capsule.files.remove(file)).resolves.toBeUndefined();
+				await expect(capsule.files.remove(streamFile)).resolves.toBeUndefined();
+				await expect(capsule.files.remove(dir)).resolves.toBeUndefined();
+			});
+		},
+		testTimeoutMs,
+	);
+
+	it(
+		"starts and controls an interactive PTY session",
+		async () => {
+			await withLiveCapsule(async (capsule) => {
+				const session = await capsule.pty.start({
+					cmd: "/bin/sh",
+					cols: 80,
+					rows: 24,
+				});
+
+				const started = await nextPtyEvent(session.events);
+				expect(started.type).toBe("started");
+
+				session.resize(100, 30);
+				session.input("printf phase4-pty\\n\nexit\n");
+
+				const events: PtyEvent[] = [];
+				for (let i = 0; i < 10; i += 1) {
+					const event = await nextPtyEvent(session.events);
+					events.push(event);
+					if (event.type === "exit" || event.type === "error") break;
+				}
+
+				const output = events
+					.filter(
+						(event) =>
+							event.type === "output" && typeof event.data === "string",
+					)
+					.map((event) =>
+						Buffer.from(event.data as string, "base64").toString(),
+					)
+					.join("");
+
+				expect(output).toContain("phase4-pty");
+				expect(events.at(-1)).toMatchObject({ type: "exit" });
+				session.close();
+			});
+		},
+		testTimeoutMs,
+	);
+});
diff --git a/tests/pty.test.ts b/tests/pty.test.ts
new file mode 100644
index 0000000..cd029a0
--- /dev/null
+++ b/tests/pty.test.ts
@@ -0,0 +1,71 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { Capsule } from "../src/capsule.js";
+
+describe("PtyManager", () => {
+	it("starts a PTY, sends controls, and yields events", async () => {
+		const capsule = new Capsule("cap_1", {
+			baseUrl: "https://api.example.com",
+		});
+		const sent: unknown[] = [];
+		let onMessage: ((message: unknown) => void) | undefined;
+		vi.spyOn(capsule.client.capsules, "ptySession").mockImplementation(
+			async (_id, opts) => {
+				onMessage = opts.onMessage;
+				return {
+					close: vi.fn(),
+					get isClosed() {
+						return false;
+					},
+					send: (message: unknown) => sent.push(message),
+				} as never;
+			},
+		);
+
+		const session = await capsule.pty.start({
+			cmd: "/bin/sh",
+			cols: 100,
+			rows: 30,
+		});
+		expect(sent).toEqual([
+			{ cmd: "/bin/sh", cols: 100, rows: 30, type: "start" },
+		]);
+
+		session.input("ls\n");
+		session.resize(120, 40);
+		session.kill();
+		expect(sent.slice(1)).toEqual([
+			{ data: Buffer.from("ls\n").toString("base64"), type: "input" },
+			{ cols: 120, rows: 40, type: "resize" },
+			{ type: "kill" },
+		]);
+
+		const event = session.events.next();
+		onMessage?.({ data: Buffer.from("ok").toString("base64"), type: "output" });
+		await expect(event).resolves.toEqual({
+			done: false,
+			value: {
+				data: Buffer.from("ok").toString("base64"),
+				type: "output",
+			},
+		});
+	});
+
+	it("connects to an existing PTY tag", async () => {
+		const capsule = new Capsule("cap_1", {
+			baseUrl: "https://api.example.com",
+		});
+		const sent: unknown[] = [];
+		vi.spyOn(capsule.client.capsules, "ptySession").mockResolvedValue({
+			close: vi.fn(),
+			get isClosed() {
+				return false;
+			},
+			send: (message: unknown) => sent.push(message),
+		} as never);
+
+		await capsule.pty.connect("pty-tag");
+
+		expect(sent).toEqual([{ tag: "pty-tag", type: "connect" }]);
+	});
+});