test(kysely-adapter): reproduce D1 migration race

e2e/smoke/test/fixtures/cloudflare/package.json

@@ -3,11 +3,13 @@
   "private": true,
   "dependencies": {
     "@better-auth/core": "workspace:*",
+    "@better-auth/kysely-adapter": "workspace:*",
     "@better-auth/sso": "workspace:*",
     "better-auth": "workspace:*",
     "hono": "^4.13.7"
   },
   "devDependencies": {
+    "kysely": "catalog:",
     "vitest": "catalog:vitest",
     "wrangler": "4.123.0"
   },

e2e/smoke/test/fixtures/cloudflare/src/index.ts

@@ -1,3 +1,4 @@
+import { env } from "cloudflare:workers";
 import type { AuthEndpointContext } from "@better-auth/core/context";
 import {
 	getCurrentAdapter,
@@ -9,8 +10,11 @@ import type {
 	DBAdapter,
 	DBTransactionAdapter,
 } from "@better-auth/core/db/adapter";
+import { createKyselyAdapter } from "@better-auth/kysely-adapter";
 import { getMigrations } from "better-auth/db/migration";
 import { Hono } from "hono";
+import type { Kysely } from "kysely";
+import { Migrator } from "kysely";
 import { auth } from "./auth";
 
 const app = new Hono();
@@ -30,6 +34,74 @@ app.post("/_test/migrate", async (c) => {
 	return c.body(null, 204);
 });
 
+app.get("/_test/d1-migration-lock", async (c) => {
+	const { kysely } = await createKyselyAdapter({ database: env.DB });
+	if (!kysely) throw new Error("D1 test database was not created");
+
+	const suffix = crypto.randomUUID().replaceAll("-", "");
+	const migrationTableName = `migration_state_${suffix}`;
+	const migrationLockTableName = `migration_lock_${suffix}`;
+	const targetTableName = `migration_target_${suffix}`;
+	const migrationOptions = {
+		db: kysely,
+		migrationTableName,
+		migrationLockTableName,
+	};
+
+	try {
+		const initialization = await new Migrator({
+			...migrationOptions,
+			provider: { getMigrations: async () => ({}) },
+		}).migrateToLatest();
+		if (initialization.error) throw initialization.error;
+
+		let migrationStarts = 0;
+		let releaseBarrier = () => {};
+		const barrier = new Promise<void>((resolve) => {
+			releaseBarrier = resolve;
+		});
+		const timeout = setTimeout(releaseBarrier, 1500);
+		try {
+			const migrator = new Migrator({
+				...migrationOptions,
+				provider: {
+					getMigrations: async () => ({
+						"001_create_table": {
+							async up(database: Kysely<unknown>) {
+								migrationStarts++;
+								if (migrationStarts === 2) releaseBarrier();
+								await barrier;
+								await database.schema
+									.createTable(targetTableName)
+									.addColumn("id", "integer")
+									.execute();
+							},
+						},
+					}),
+				},
+			});
+			const results = await Promise.all([
+				migrator.migrateToLatest(),
+				migrator.migrateToLatest(),
+			]);
+			const recorded = await env.DB.prepare(
+				`select count(*) as count from ${migrationTableName}`,
+			).first<{ count: number }>();
+			return c.json({
+				migrationStarts,
+				recorded: recorded?.count,
+				errors: results.map((result) =>
+					result.error ? String(result.error) : null,
+				),
+			});
+		} finally {
+			clearTimeout(timeout);
+		}
+	} finally {
+		await kysely.destroy();
+	}
+});
+
 app.get("/_test/async-context/concurrency", async (c) => {
 	const contexts = Array.from(
 		{ length: 32 },

e2e/smoke/test/fixtures/cloudflare/test/d1-migration-lock.test.ts

@@ -0,0 +1,34 @@
+import { afterAll, afterEach, beforeAll, expect, it } from "vitest";
+import { createTestHarness } from "wrangler";
+
+const server = createTestHarness({
+	workers: [{ configPath: "./wrangler.json" }],
+});
+
+beforeAll(async () => {
+	await server.listen();
+});
+
+afterEach(({ task }) => {
+	if (task.result?.state === "fail") server.debug();
+});
+
+afterAll(async () => {
+	await server.close();
+});
+
+/**
+ * @see https://kysely-org.github.io/kysely-apidoc/classes/SqliteAdapter.html#acquiremigrationlock
+ */
+it("runs a D1 migration only once when two Kysely migrators start together", async () => {
+	const response = await server.fetch(
+		"http://localhost:8787/_test/d1-migration-lock",
+	);
+	expect(response.status).toBe(200);
+	const result: unknown = await response.json();
+	expect(result).toEqual({
+		migrationStarts: 1,
+		recorded: 1,
+		errors: [null, null],
+	});
+}, 15_000);

pnpm-lock.yaml

@@ -887,6 +887,9 @@ importers:
       '@better-auth/core':
         specifier: workspace:*
         version: link:../../../../../packages/core
+      '@better-auth/kysely-adapter':
+        specifier: workspace:*
+        version: link:../../../../../packages/kysely-adapter
       '@better-auth/sso':
         specifier: workspace:*
         version: link:../../../../../packages/sso
@@ -897,6 +900,9 @@ importers:
         specifier: ^4.13.7
         version: 4.13.7
     devDependencies:
+      kysely:
+        specifier: 0.28.17
+        version: 0.28.17
       vitest:
         specifier: catalog:vitest
         version: 5.0.0(@opentelemetry/api@1.9.1)(@types/node@25.9.4)(@vitest/coverage-istanbul@5.0.0)(@vitest/ui@5.0.0)(happy-dom@20.8.9)(msw@2.14.6(@types/node@25.9.4)(typescript@6.0.3))(vite@8.2.0(@types/node@25.9.4)(esbuild@0.28.1)(jiti@2.7.0)(terser@5.46.1)(tsx@4.21.0)(yaml@2.9.0))