diff --git a/src/server/db/accountTokenSchemaCompatibility.ts b/src/server/db/accountTokenSchemaCompatibility.ts
new file mode 100644
index 0000000..bd2ec40
--- /dev/null
+++ b/src/server/db/accountTokenSchemaCompatibility.ts
@@ -0,0 +1,64 @@
+export type AccountTokenSchemaDialect = 'sqlite' | 'mysql' | 'postgres';
+
+export interface AccountTokenSchemaInspector {
+  dialect: AccountTokenSchemaDialect;
+  tableExists(table: string): Promise<boolean>;
+  columnExists(table: string, column: string): Promise<boolean>;
+  execute(sqlText: string): Promise<void>;
+}
+
+type AccountTokenColumnCompatibilitySpec = {
+  table: 'account_tokens';
+  column: string;
+  addSql: Record<AccountTokenSchemaDialect, string>;
+};
+
+const ACCOUNT_TOKEN_COLUMN_COMPATIBILITY_SPECS: AccountTokenColumnCompatibilitySpec[] = [
+  {
+    table: 'account_tokens',
+    column: 'token_group',
+    addSql: {
+      sqlite: 'ALTER TABLE account_tokens ADD COLUMN token_group text;',
+      mysql: 'ALTER TABLE `account_tokens` ADD COLUMN `token_group` TEXT NULL',
+      postgres: 'ALTER TABLE "account_tokens" ADD COLUMN "token_group" TEXT',
+    },
+  },
+];
+
+function normalizeSchemaErrorMessage(error: unknown): string {
+  if (typeof error === 'object' && error && 'message' in error) {
+    return String((error as { message?: unknown }).message || '');
+  }
+  return String(error || '');
+}
+
+function isDuplicateColumnError(error: unknown): boolean {
+  const lowered = normalizeSchemaErrorMessage(error).toLowerCase();
+  return lowered.includes('duplicate column')
+    || lowered.includes('already exists')
+    || lowered.includes('duplicate column name');
+}
+
+async function executeAddColumn(inspector: AccountTokenSchemaInspector, sqlText: string): Promise<void> {
+  try {
+    await inspector.execute(sqlText);
+  } catch (error) {
+    if (!isDuplicateColumnError(error)) {
+      throw error;
+    }
+  }
+}
+
+export async function ensureAccountTokenSchemaCompatibility(inspector: AccountTokenSchemaInspector): Promise<void> {
+  for (const spec of ACCOUNT_TOKEN_COLUMN_COMPATIBILITY_SPECS) {
+    const hasTable = await inspector.tableExists(spec.table);
+    if (!hasTable) {
+      continue;
+    }
+
+    const hasColumn = await inspector.columnExists(spec.table, spec.column);
+    if (!hasColumn) {
+      await executeAddColumn(inspector, spec.addSql[inspector.dialect]);
+    }
+  }
+}
diff --git a/src/server/db/runtimeSchemaBootstrap.ts b/src/server/db/runtimeSchemaBootstrap.ts
index 8ebe500..e76d71c 100644
--- a/src/server/db/runtimeSchemaBootstrap.ts
+++ b/src/server/db/runtimeSchemaBootstrap.ts
@@ -6,6 +6,7 @@ import { dirname, resolve } from 'node:path';
 import { ensureSiteSchemaCompatibility, type SiteSchemaInspector } from './siteSchemaCompatibility.js';
 import { ensureRouteGroupingSchemaCompatibility } from './routeGroupingSchemaCompatibility.js';
 import { ensureProxyFileSchemaCompatibility } from './proxyFileSchemaCompatibility.js';
+import { ensureAccountTokenSchemaCompatibility } from './accountTokenSchemaCompatibility.js';
 
 export type RuntimeSchemaDialect = 'sqlite' | 'mysql' | 'postgres';
 
@@ -241,6 +242,7 @@ export async function ensureRuntimeDatabaseSchema(client: RuntimeSchemaClient):
   await ensureSiteSchemaCompatibility(createSiteSchemaInspector(client));
   await ensureRouteGroupingSchemaCompatibility(createSiteSchemaInspector(client));
   await ensureProxyFileSchemaCompatibility(createSiteSchemaInspector(client));
+  await ensureAccountTokenSchemaCompatibility(createSiteSchemaInspector(client));
 }
 
 export async function bootstrapRuntimeDatabaseSchema(input: RuntimeSchemaConnectionInput): Promise<void> {