diff --git a/apps/tui/src/lib/worktree.test.ts b/apps/tui/src/lib/worktree.test.ts
new file mode 100644
index 0000000..2aca6a5
--- /dev/null
+++ b/apps/tui/src/lib/worktree.test.ts
@@ -0,0 +1,141 @@
+import { describe, expect, it } from "bun:test";
+import { resolve } from "node:path";
+import { Worktree } from "./worktree";
+
+type FakeResult = {
+	cwd(directory: string): FakeResult;
+	text(): Promise<string>;
+};
+
+type FakeShell = (
+	strings: TemplateStringsArray,
+	...values: unknown[]
+) => FakeResult;
+
+type CommandCall = {
+	command: string;
+	cwd?: string;
+};
+
+function createFakeShell(outputs: Record<string, string>): {
+	shell: FakeShell;
+	calls: CommandCall[];
+} {
+	const calls: CommandCall[] = [];
+
+	const shell: FakeShell = (strings, ...values) => {
+		const command = strings
+			.reduce((acc, part, idx) => {
+				const value = idx < values.length ? String(values[idx]) : "";
+				return `${acc}${part}${value}`;
+			}, "")
+			.trim();
+
+		const call: CommandCall = { command };
+		calls.push(call);
+
+		return {
+			cwd(directory: string) {
+				call.cwd = directory;
+				return this;
+			},
+			async text() {
+				return outputs[command] ?? "";
+			},
+		};
+	};
+
+	return { shell, calls };
+}
+
+describe("Worktree", () => {
+	it("creates a worktree with expected branch and path", async () => {
+		const repoRoot = "/tmp/project/repo";
+		const { shell, calls } = createFakeShell({
+			"git rev-parse --show-toplevel": `${repoRoot}\n`,
+		});
+		const worktree = new Worktree(shell);
+
+		const info = await worktree.create("worker-1");
+
+		expect(info).toEqual({
+			name: "worker-1",
+			path: resolve(repoRoot, "..", ".worktrees", "worker-1"),
+			branch: "worktree/worker-1",
+		});
+		expect(calls[1]).toEqual({
+			command: `git worktree add ${resolve(repoRoot, "..", ".worktrees", "worker-1")} -b worktree/worker-1`,
+			cwd: repoRoot,
+		});
+	});
+
+	it("rejects invalid names before running git commands", async () => {
+		const { shell, calls } = createFakeShell({
+			"git rev-parse --show-toplevel": "/tmp/project/repo\n",
+		});
+		const worktree = new Worktree(shell);
+
+		await expect(worktree.create("../escape")).rejects.toThrow("Invalid worktree name");
+		await expect(worktree.remove(" bad")).rejects.toThrow("Invalid worktree name");
+		await expect(worktree.merge("a/b")).rejects.toThrow("Invalid worktree name");
+		expect(calls).toHaveLength(0);
+	});
+
+	it("lists attached and detached worktrees", async () => {
+		const repoRoot = "/tmp/project/repo";
+		const { shell } = createFakeShell({
+			"git rev-parse --show-toplevel": `${repoRoot}\n`,
+			"git worktree list --porcelain": [
+				"worktree /tmp/project/repo",
+				"HEAD aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+				"branch refs/heads/main",
+				"",
+				"worktree /tmp/project/.worktrees/worker-2",
+				"HEAD bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
+				"detached",
+				"",
+			].join("\n"),
+		});
+		const worktree = new Worktree(shell);
+
+		await expect(worktree.list()).resolves.toEqual([
+			{ name: "repo", path: "/tmp/project/repo", branch: "main" },
+			{
+				name: "worker-2",
+				path: "/tmp/project/.worktrees/worker-2",
+				branch: "HEAD",
+			},
+		]);
+	});
+
+	it("fails fast on malformed worktree entries", async () => {
+		const repoRoot = "/tmp/project/repo";
+		const { shell } = createFakeShell({
+			"git rev-parse --show-toplevel": `${repoRoot}\n`,
+			"git worktree list --porcelain": ["HEAD deadbeef", "branch refs/heads/main", ""].join(
+				"\n",
+			),
+		});
+		const worktree = new Worktree(shell);
+
+		await expect(worktree.list()).rejects.toThrow("Unable to parse worktree entry");
+	});
+
+	it("merge runs merge then remove", async () => {
+		const repoRoot = "/tmp/project/repo";
+		const { shell, calls } = createFakeShell({
+			"git rev-parse --show-toplevel": `${repoRoot}\n`,
+		});
+		const worktree = new Worktree(shell);
+
+		await worktree.merge("worker-3");
+
+		expect(calls.map((call) => call.command)).toEqual([
+			"git rev-parse --show-toplevel",
+			"git merge worktree/worker-3",
+			`git worktree remove ${resolve(repoRoot, "..", ".worktrees", "worker-3")} --force`,
+		]);
+		expect(calls[1]?.cwd).toBe(repoRoot);
+		expect(calls[2]?.cwd).toBe(repoRoot);
+	});
+});
diff --git a/apps/tui/src/lib/worktree.ts b/apps/tui/src/lib/worktree.ts
new file mode 100644
index 0000000..d0d1e22
--- /dev/null
+++ b/apps/tui/src/lib/worktree.ts
@@ -0,0 +1,115 @@
+import { $ } from "bun";
+import { basename, isAbsolute, relative, resolve } from "node:path";
+
+export interface WorktreeInfo {
+	name: string;
+	path: string;
+	branch: string;
+}
+
+type ShellTag = (
+	strings: TemplateStringsArray,
+	...values: unknown[]
+) => {
+	cwd(directory: string): { text(): Promise<string> };
+	text(): Promise<string>;
+};
+
+export class Worktree {
+	constructor(private readonly shell: ShellTag = $) {}
+
+	async create(name: string): Promise<WorktreeInfo> {
+		this.assertValidName(name);
+		const root = await this.repoRoot();
+		const path = this.worktreePath(root, name);
+		const branch = this.branchName(name);
+
+		await this.shell`git worktree add ${path} -b ${branch}`.cwd(root).text();
+
+		return { name, path, branch };
+	}
+
+	async remove(name: string): Promise<void> {
+		this.assertValidName(name);
+		const root = await this.repoRoot();
+		await this.removeAt(root, name);
+	}
+
+	async merge(name: string): Promise<void> {
+		this.assertValidName(name);
+		const root = await this.repoRoot();
+		const branch = this.branchName(name);
+		await this.shell`git merge ${branch}`.cwd(root).text();
+		await this.removeAt(root, name);
+	}
+
+	async list(): Promise<WorktreeInfo[]> {
+		const root = await this.repoRoot();
+		const output = await this.shell`git worktree list --porcelain`.cwd(root).text();
+
+		if (!output.trim()) {
+			return [];
+		}
+
+		return output
+			.trim()
+			.split("\n\n")
+			.filter(Boolean)
+			.map((entry) => {
+				const lines = entry.split("\n");
+				const worktreeLine = lines.find((line) => line.startsWith("worktree "));
+				const branchLine = lines.find((line) => line.startsWith("branch "));
+				const detached = lines.includes("detached");
+
+				if (!worktreeLine) {
+					throw new Error(`Unable to parse worktree entry: ${entry}`);
+				}
+
+				if (!branchLine && !detached) {
+					throw new Error(`Unable to parse worktree branch: ${entry}`);
+				}
+
+				const path = worktreeLine.replace("worktree ", "").trim();
+				const branchRef = branchLine?.replace("branch ", "").trim();
+				const branch = branchRef ? branchRef.replace("refs/heads/", "") : "HEAD";
+				const name = basename(path);
+
+				return { name, path, branch };
+			});
+	}
+
+	private async removeAt(root: string, name: string): Promise<void> {
+		const path = this.worktreePath(root, name);
+		await this.shell`git worktree remove ${path} --force`.cwd(root).text();
+	}
+
+	private branchName(name: string): string {
+		return `worktree/${name}`;
+	}
+
+	private worktreePath(root: string, name: string): string {
+		const base = resolve(root, "..", ".worktrees");
+		const path = resolve(base, name);
+		const rel = relative(base, path);
+
+		if (isAbsolute(rel) || rel.startsWith("..")) {
+			throw new Error(`Worktree path escapes base directory: ${name}`);
+		}
+
+		return path;
+	}
+
+	private assertValidName(name: string): void {
+		if (name.length === 0 || name.trim() !== name) {
+			throw new Error(`Invalid worktree name: "${name}"`);
+		}
+
+		if (!/^[A-Za-z0-9][A-Za-z0-9._-]*$/.test(name)) {
+			throw new Error(`Invalid worktree name: "${name}"`);
+		}
+	}
+
+	private async repoRoot(): Promise<string> {
+		return (await this.shell`git rev-parse --show-toplevel`.text()).trim();
+	}
+}