fix(auth): carry Better Auth update hooks and defaults onto generated columns

packages/void/src/auth/drizzle.ts

@@ -180,21 +180,27 @@ function usesUnboundedMySqlText(
 }
 
 /**
- * The default of a required field when the database can store it as a literal.
+ * The default of a field when it can be written as a literal.
  * Function, date and JSON defaults have none.
  */
-function resolveFixedDefault(
-  field: DBFieldAttribute,
-): Pick<VoidAuthMigrationField, 'defaultValue'> {
-  if (field.required === false || field.type === 'date' || isJsonField(field)) {
-    return {};
+function resolveLiteralDefault(field: DBFieldAttribute): string | number | boolean | undefined {
+  if (field.type === 'date' || isJsonField(field)) {
+    return undefined;
   }
   const value = field.defaultValue;
   return typeof value === 'string' ||
     typeof value === 'boolean' ||
     (typeof value === 'number' && Number.isFinite(value))
-    ? { defaultValue: value }
-    : {};
+    ? value
+    : undefined;
+}
+
+/** The default of a required field when the database can store it as a literal. */
+function resolveFixedDefault(
+  field: DBFieldAttribute,
+): Pick<VoidAuthMigrationField, 'defaultValue'> {
+  const value = field.required === false ? undefined : resolveLiteralDefault(field);
+  return value === undefined ? {} : { defaultValue: value };
 }
 
 function resolveReferenceFieldName(
@@ -301,7 +307,23 @@ function createColumnBuilder(
   }
 }
 
+function hasBuiltInUpdateHook(options: BetterAuthOptions, model: string, field: string): boolean {
+  if (
+    field !== 'updatedAt' ||
+    (model !== 'user' && model !== 'session' && model !== 'account' && model !== 'verification')
+  ) {
+    return false;
+  }
+  // Only Better Auth's built-in hooks are known to mean the current time.
+  // A configured field replaces that definition, including its callback.
+  return (
+    options[model]?.additionalFields?.updatedAt === undefined &&
+    !options.plugins?.some((plugin) => plugin.schema?.[model]?.fields.updatedAt !== undefined)
+  );
+}
+
 function createColumnDefinition(
+  options: BetterAuthOptions,
   dialect: 'sqlite' | 'postgresql' | 'mysql',
   schema: BetterAuthDBSchema,
   idStrategy: AuthIdStrategy,
@@ -360,6 +382,19 @@ function createColumnDefinition(
   if (field.unique && actualFieldName !== 'id') {
     parts.push('.unique()');
   }
+  // Better Auth applies these on its own writes. Direct Drizzle writes need them on the column,
+  // and these runtime-only modifiers leave the DDL, and so existing migrations, unchanged.
+  const literalDefault = resolveLiteralDefault(field);
+  if (literalDefault !== undefined) {
+    parts.push(`.$defaultFn(() => ${JSON.stringify(literalDefault)})`);
+  }
+  if (
+    field.onUpdate &&
+    field.type === 'date' &&
+    hasBuiltInUpdateHook(options, defaultModelName, defaultFieldName)
+  ) {
+    parts.push('.$onUpdate(() => new Date())');
+  }
 
   return parts.join('');
 }
@@ -466,6 +501,7 @@ export function generateVoidAuthDrizzleSchema(
     const fieldEntries = Object.entries(table.fields);
     const renderedFields = [
       `  "id": ${createColumnDefinition(
+        options,
         runtime.dialect,
         schema,
         idStrategy,
@@ -477,6 +513,7 @@ export function generateVoidAuthDrizzleSchema(
       ...fieldEntries.map(([defaultFieldName, field]) => {
         const actualFieldName = resolveFieldName(defaultFieldName, field);
         return `  ${JSON.stringify(actualFieldName)}: ${createColumnDefinition(
+          options,
           runtime.dialect,
           schema,
           idStrategy,

packages/void/test/unit/auth-drizzle.test.ts

@@ -1,7 +1,8 @@
-import { describe, expect, it } from 'vite-plus/test';
+import { describe, expect, it, vi } from 'vite-plus/test';
 import {
   generateVoidAuthDatabaseModule,
   generateVoidAuthDrizzleSchema,
+  resolveVoidAuthMigrationSchema,
 } from '../../src/auth/drizzle.ts';
 
 describe('Better Auth Drizzle codegen', () => {
@@ -106,6 +107,159 @@ describe('Better Auth Drizzle codegen', () => {
     );
   });
 
+  it('carries Better Auth update hooks and literal defaults onto the Drizzle columns', () => {
+    const code = generateVoidAuthDrizzleSchema({
+      dialect: 'sqlite',
+      providers: null,
+      userConfig: ({ defaults }) => ({
+        ...defaults,
+        user: {
+          additionalFields: {
+            banned: { type: 'boolean', required: false, defaultValue: false },
+            plan: { type: 'string', required: false, defaultValue: 'free' },
+            credits: { type: 'number', required: false, defaultValue: 10 },
+            trialEndsAt: { type: 'date', required: false, defaultValue: () => new Date() },
+            tags: { type: 'string[]', required: false, defaultValue: '[]' },
+          },
+        },
+      }),
+    });
+
+    expect(code).toContain(
+      '"emailVerified": integer("emailVerified", { mode: "boolean" }).notNull().$defaultFn(() => false)',
+    );
+    expect(code).toContain(
+      '"updatedAt": integer("updatedAt", { mode: "timestamp_ms" }).notNull().$onUpdate(() => new Date())',
+    );
+    expect(code).toContain(
+      '"banned": integer("banned", { mode: "boolean" }).$defaultFn(() => false)',
+    );
+    expect(code).toContain('"plan": text("plan").$defaultFn(() => "free")');
+    expect(code).toContain('"credits": integer("credits").$defaultFn(() => 10)');
+    expect(code).toContain('"trialEndsAt": integer("trialEndsAt", { mode: "timestamp_ms" }),');
+    expect(code).toContain('"tags": text("tags", { mode: "json" }),');
+    expect(code).toContain(
+      '"createdAt": integer("createdAt", { mode: "timestamp_ms" }).notNull(),',
+    );
+  });
+
+  it('emits update hooks in every dialect', () => {
+    expect(generateVoidAuthDrizzleSchema({ dialect: 'postgresql', providers: null })).toContain(
+      '"updatedAt": timestamp("updatedAt", { mode: "date", withTimezone: true }).notNull().$onUpdate(() => new Date())',
+    );
+    expect(generateVoidAuthDrizzleSchema({ dialect: 'mysql', providers: null })).toContain(
+      '"updatedAt": timestamp("updatedAt", { mode: "date", fsp: 3 }).notNull().$onUpdate(() => new Date())',
+    );
+  });
+
+  it.each(['sqlite', 'postgresql', 'mysql'] as const)(
+    'leaves custom date update hooks out of the generated %s schema',
+    (dialect) => {
+      const onUpdate = vi.fn(() => new Date('2035-01-01T00:00:00.000Z'));
+      const code = generateVoidAuthDrizzleSchema({
+        dialect,
+        providers: null,
+        userConfig: ({ defaults }) => ({
+          ...defaults,
+          user: {
+            additionalFields: {
+              expiresAt: { type: 'date', required: false, onUpdate },
+            },
+          },
+          plugins: [
+            {
+              id: 'custom-dates',
+              schema: {
+                audit: {
+                  fields: { updatedAt: { type: 'date', onUpdate } },
+                },
+              },
+            },
+          ],
+        }),
+      });
+
+      expect(code.split('\n').find((line) => line.includes('"expiresAt":'))).not.toContain(
+        '.$onUpdate',
+      );
+      const audit = code.slice(code.indexOf('export const auditTable'));
+      expect(audit.split('\n').find((line) => line.includes('"updatedAt":'))).not.toContain(
+        '.$onUpdate',
+      );
+      expect(code.match(/\.\$onUpdate\(/g)).toHaveLength(4);
+      expect(onUpdate).not.toHaveBeenCalled();
+    },
+  );
+
+  it.each(['user', 'session', 'account', 'verification'] as const)(
+    'does not replace a configured %s.updatedAt hook',
+    (model) => {
+      const onUpdate = vi.fn(() => new Date('2035-01-01T00:00:00.000Z'));
+      for (const source of ['additionalFields', 'plugin'] as const) {
+        const field = { type: 'date' as const, onUpdate };
+        const code = generateVoidAuthDrizzleSchema({
+          dialect: 'sqlite',
+          providers: null,
+          userConfig: ({ defaults }) => ({
+            ...defaults,
+            ...(source === 'additionalFields'
+              ? { [model]: { additionalFields: { updatedAt: field } } }
+              : {
+                  plugins: [
+                    {
+                      id: 'custom-updated-at',
+                      schema: { [model]: { fields: { updatedAt: field } } },
+                    },
+                  ],
+                }),
+          }),
+        });
+
+        const table = code.slice(code.indexOf(`export const ${model}Table`));
+        expect(table.split('\n').find((line) => line.includes('"updatedAt":'))).not.toContain(
+          '.$onUpdate',
+        );
+        expect(code.match(/\.\$onUpdate\(/g)).toHaveLength(3);
+      }
+      expect(onUpdate).not.toHaveBeenCalled();
+    },
+  );
+
+  it('keeps the built-in update hook when its table and column are renamed', () => {
+    const code = generateVoidAuthDrizzleSchema({
+      dialect: 'sqlite',
+      providers: null,
+      userConfig: ({ defaults }) => ({
+        ...defaults,
+        user: { modelName: 'members', fields: { updatedAt: 'modifiedAt' } },
+      }),
+    });
+
+    expect(code).toContain(
+      '"modifiedAt": integer("modifiedAt", { mode: "timestamp_ms" }).notNull().$onUpdate(() => new Date())',
+    );
+    expect(code.match(/\.\$onUpdate\(/g)).toHaveLength(4);
+  });
+
+  it('keeps optional defaults out of the migration metadata', () => {
+    const schema = resolveVoidAuthMigrationSchema({
+      dialect: 'sqlite',
+      providers: null,
+      userConfig: ({ defaults }) => ({
+        ...defaults,
+        user: {
+          additionalFields: {
+            banned: { type: 'boolean', required: false, defaultValue: false },
+          },
+        },
+      }),
+    });
+    const user = schema.tables.find((table) => table.name === 'user');
+
+    expect(user?.fields.banned).not.toHaveProperty('defaultValue');
+    expect(user?.fields.emailVerified).toHaveProperty('defaultValue', false);
+  });
+
   it('does not add MySQL storage metadata to PostgreSQL or SQLite schemas', () => {
     for (const dialect of ['postgresql', 'sqlite'] as const) {
       const code = generateVoidAuthDrizzleSchema({ dialect, providers: ['google'] });