diff --git a/fluxer_api/src/api/rpc/tests/RpcSessionInitHarnessAccess.test.ts b/fluxer_api/src/api/rpc/tests/RpcSessionInitHarnessAccess.test.ts
new file mode 100644
index 000000000..261769180
--- /dev/null
+++ b/fluxer_api/src/api/rpc/tests/RpcSessionInitHarnessAccess.test.ts
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {APIErrorCodes} from '@fluxer/constants/src/ApiErrorCodes';
+import {afterEach, beforeEach, describe, expect, test} from 'vitest';
+import {createTestAccount} from '../../auth/tests/AuthTestUtils';
+import {Config} from '../../Config';
+import {type ApiTestHarness, createApiTestHarness} from '../../test/ApiTestHarness';
+import {HTTP_STATUS} from '../../test/TestConstants';
+import {createBuilder} from '../../test/TestRequestBuilder';
+
+const HARNESS_TOKEN = 'rpc-session-init-harness-token';
+const TEST_AUTH_HEADER = 'x-test-token';
+
+interface RpcSessionResponse {
+	type: string;
+	data: {
+		user: {
+			id: string;
+		};
+	};
+}
+
+describe('POST /test/rpc-session-init harness access', () => {
+	let harness: ApiTestHarness;
+	let previousTestHarnessToken: string | undefined;
+	beforeEach(async () => {
+		harness = await createApiTestHarness();
+		previousTestHarnessToken = Config.dev.testHarnessToken;
+	});
+	afterEach(async () => {
+		Config.dev.testHarnessToken = previousTestHarnessToken;
+		await harness?.shutdown();
+	});
+
+	test('rejects a session init that omits the harness token', async () => {
+		const account = await createTestAccount(harness);
+		Config.dev.testHarnessToken = HARNESS_TOKEN;
+		await createBuilder(harness, '')
+			.post('/test/rpc-session-init')
+			.body({type: 'session', token: account.token, version: 1, ip: '127.0.0.1'})
+			.expect(HTTP_STATUS.FORBIDDEN, APIErrorCodes.TEST_HARNESS_FORBIDDEN)
+			.execute();
+	});
+
+	test('rejects before the rpc request body is parsed or dispatched', async () => {
+		Config.dev.testHarnessToken = HARNESS_TOKEN;
+		await createBuilder(harness, '')
+			.post('/test/rpc-session-init')
+			.body({type: 'definitely_not_an_rpc_request'})
+			.expect(HTTP_STATUS.FORBIDDEN, APIErrorCodes.TEST_HARNESS_FORBIDDEN)
+			.execute();
+	});
+
+	test('rejects a session init carrying the wrong harness token', async () => {
+		const account = await createTestAccount(harness);
+		Config.dev.testHarnessToken = HARNESS_TOKEN;
+		await createBuilder(harness, '')
+			.post('/test/rpc-session-init')
+			.header(TEST_AUTH_HEADER, `${HARNESS_TOKEN}-wrong`)
+			.body({type: 'session', token: account.token, version: 1, ip: '127.0.0.1'})
+			.expect(HTTP_STATUS.FORBIDDEN, APIErrorCodes.TEST_HARNESS_FORBIDDEN)
+			.execute();
+	});
+
+	test('accepts a session init carrying the harness token', async () => {
+		const account = await createTestAccount(harness);
+		Config.dev.testHarnessToken = HARNESS_TOKEN;
+		const response = await createBuilder<RpcSessionResponse>(harness, '')
+			.post('/test/rpc-session-init')
+			.header(TEST_AUTH_HEADER, HARNESS_TOKEN)
+			.body({type: 'session', token: account.token, version: 1, ip: '127.0.0.1'})
+			.expect(HTTP_STATUS.OK)
+			.execute();
+		expect(response.type).toBe('session');
+		expect(response.data.user.id).toBe(account.userId);
+	});
+
+	test('accepts a session init when no harness token is configured', async () => {
+		const account = await createTestAccount(harness);
+		Config.dev.testHarnessToken = undefined;
+		const response = await createBuilder<RpcSessionResponse>(harness, '')
+			.post('/test/rpc-session-init')
+			.body({type: 'session', token: account.token, version: 1, ip: '127.0.0.1'})
+			.expect(HTTP_STATUS.OK)
+			.execute();
+		expect(response.data.user.id).toBe(account.userId);
+	});
+});
diff --git a/fluxer_api/src/api/test/TestHarnessController.ts b/fluxer_api/src/api/test/TestHarnessController.ts
index e88e5799a..3c97b8dbf 100644
--- a/fluxer_api/src/api/test/TestHarnessController.ts
+++ b/fluxer_api/src/api/test/TestHarnessController.ts
@@ -2796,6 +2796,7 @@ export function TestHarnessController(app: HonoApp) {
 		return ctx.json({cleared: true, deleted_count: totalDeleted});
 	});
 	app.post('/test/rpc-session-init', async (ctx) => {
+		ensureHarnessAccess(ctx);
 		const request = RpcRequest.parse(await ctx.req.json());
 		const response = await ctx.get('rpcService').handleRpcRequest({request, requestCache: ctx.get('requestCache')});
 		return ctx.json(response);