diff --git a/src/adversary/agents/blue-team.ts b/src/adversary/agents/blue-team.ts
index fe92432..09c5d5a 100644
--- a/src/adversary/agents/blue-team.ts
+++ b/src/adversary/agents/blue-team.ts
@@ -32,7 +32,9 @@ export function BlueTeam() {
 		env as unknown as AdversarySandboxEnv,
 		input.sandboxId,
 	);
-	useSandbox(adversaryAgentSandbox(sandbox, BLUE_DIR), { cwd: BLUE_DIR });
+	useSandbox(adversaryAgentSandbox(sandbox, BLUE_DIR, input.skill.name), {
+		cwd: BLUE_DIR,
+	});
 
 	const writeResult = useDataWriter('result', { schema: blueTeamResultSchema });
 	useTool({
diff --git a/src/adversary/agents/purple-team.ts b/src/adversary/agents/purple-team.ts
index 67238c3..7e98285 100644
--- a/src/adversary/agents/purple-team.ts
+++ b/src/adversary/agents/purple-team.ts
@@ -34,7 +34,9 @@ export function PurpleTeam() {
 		env as unknown as AdversarySandboxEnv,
 		input.sandboxId,
 	);
-	useSandbox(adversaryAgentSandbox(sandbox, RED_DIR), { cwd: RED_DIR });
+	useSandbox(adversaryAgentSandbox(sandbox, RED_DIR, input.skill.name), {
+		cwd: RED_DIR,
+	});
 
 	const writeResult = useDataWriter('result', {
 		schema: purpleTeamResultSchema,
diff --git a/src/adversary/sandbox.ts b/src/adversary/sandbox.ts
index 3ea59d8..916358d 100644
--- a/src/adversary/sandbox.ts
+++ b/src/adversary/sandbox.ts
@@ -56,14 +56,24 @@ export function getAdversarySandbox(
 export function adversaryAgentSandbox(
 	sandbox: AdversarySandbox,
 	cwd: string,
+	mountedSkillName: string,
 ): SandboxFactory {
 	const base = cloudflareSandbox(sandbox, { cwd });
+	const workspaceSkillsDir = `${cwd}/.agents/skills`;
 	return {
 		...base,
 		async createSandbox(options) {
 			const environment = await base.createSandbox(options);
 			return {
 				...environment,
+				async readdir(path) {
+					const entries = await environment.readdir(path);
+					// The pinned snapshot is mounted with useSkill; hide its checkout
+					// copy from Flue's workspace discovery to avoid a name collision.
+					return path === workspaceSkillsDir
+						? entries.filter((entry) => entry !== mountedSkillName)
+						: entries;
+				},
 				exec(command, execOptions) {
 					const requested =
 						execOptions?.timeoutMs ?? COMMAND_TIMEOUT_SECONDS * 1_000;
diff --git a/tests/adversary-sandbox.test.ts b/tests/adversary-sandbox.test.ts
new file mode 100644
index 0000000..ca45313
--- /dev/null
+++ b/tests/adversary-sandbox.test.ts
@@ -0,0 +1,43 @@
+import { describe, expect, it, vi } from 'vitest';
+
+const mocks = vi.hoisted(() => ({
+	readdir: vi.fn<(path: string) => Promise<string[]>>(),
+}));
+
+vi.mock('@cloudflare/sandbox', () => ({ getSandbox: vi.fn() }));
+vi.mock('@flue/runtime/cloudflare', () => ({
+	cloudflareSandbox: vi.fn(() => ({
+		createSandbox: vi.fn(async () => ({
+			cwd: '/',
+			exec: vi.fn(),
+			readdir: mocks.readdir,
+		})),
+	})),
+}));
+
+import {
+	type AdversarySandbox,
+	adversaryAgentSandbox,
+	BLUE_DIR,
+	RED_DIR,
+} from '../src/adversary/sandbox.ts';
+
+describe('adversary agent sandbox', () => {
+	it.each([
+		[BLUE_DIR, 'astro-adversary-blue'],
+		[RED_DIR, 'astro-adversary-purple'],
+	])(
+		'hides the mounted skill in %s from workspace discovery',
+		async (cwd, skill) => {
+			const skillsDir = `${cwd}/.agents/skills`;
+			mocks.readdir.mockImplementation(async (path) =>
+				path === skillsDir ? [skill, 'other-skill'] : [skill],
+			);
+			const factory = adversaryAgentSandbox({} as AdversarySandbox, cwd, skill);
+			const environment = await factory.createSandbox({ id: 'test' });
+
+			expect(await environment.readdir(skillsDir)).toEqual(['other-skill']);
+			expect(await environment.readdir(`${cwd}/src`)).toEqual([skill]);
+		},
+	);
+});