Fail closed for public tenant DB startup

Co-Authored-By: Paperclip <noreply@paperclip.ing>

server/src/__tests__/server-startup-feedback-export.test.ts

@@ -216,6 +216,35 @@ describe("startServer feedback export wiring", () => {
       serverPort: 3210,
     });
   });
+
+  it("refuses authenticated public startup without an external database URL", async () => {
+    loadConfigMock.mockReturnValue(buildTestConfig({
+      deploymentExposure: "public",
+      authBaseUrlMode: "explicit",
+      authPublicBaseUrl: "https://tenant.example.com",
+      databaseMode: "embedded-postgres",
+      databaseUrl: undefined,
+    }));
+
+    await expect(startServer()).rejects.toThrow(
+      "authenticated public deployments require DATABASE_URL or config.database.connectionString",
+    );
+    expect(createDbMock).not.toHaveBeenCalled();
+  });
+
+  it("refuses authenticated public startup when DATABASE_URL is not a postgres URL", async () => {
+    loadConfigMock.mockReturnValue(buildTestConfig({
+      deploymentExposure: "public",
+      authBaseUrlMode: "explicit",
+      authPublicBaseUrl: "https://tenant.example.com",
+      databaseUrl: "secret://paperclip-cloud/stacks/alpha/database/runtime-url",
+    }));
+
+    await expect(startServer()).rejects.toThrow(
+      "authenticated public deployments require DATABASE_URL to be a postgres/postgresql connection string",
+    );
+    expect(createDbMock).not.toHaveBeenCalled();
+  });
 });
 
 describe("startServer authenticated auth origin setup", () => {

server/src/index.ts

@@ -187,6 +187,31 @@ export async function startServer(): Promise<StartedServer> {
     return normalized === "127.0.0.1" || normalized === "localhost" || normalized === "::1";
   }
 
+  function isPostgresConnectionString(connectionString: string): boolean {
+    try {
+      const parsed = new URL(connectionString);
+      return parsed.protocol === "postgres:" || parsed.protocol === "postgresql:";
+    } catch {
+      return false;
+    }
+  }
+
+  function assertCloudDatabaseContract(): void {
+    if (config.deploymentMode !== "authenticated" || config.deploymentExposure !== "public") {
+      return;
+    }
+    if (!config.databaseUrl) {
+      throw new Error(
+        "authenticated public deployments require DATABASE_URL or config.database.connectionString; refusing embedded PostgreSQL fallback",
+      );
+    }
+    if (!isPostgresConnectionString(config.databaseUrl)) {
+      throw new Error(
+        "authenticated public deployments require DATABASE_URL to be a postgres/postgresql connection string",
+      );
+    }
+  }
+
   function rewriteLocalUrlPort(rawUrl: string | undefined, port: number): string | undefined {
     if (!rawUrl) return undefined;
     try {
@@ -270,6 +295,7 @@ export async function startServer(): Promise<StartedServer> {
   let startupDbInfo:
     | { mode: "external-postgres"; connectionString: string }
     | { mode: "embedded-postgres"; dataDir: string; port: number };
+  assertCloudDatabaseContract();
   if (config.databaseUrl) {
     const migrationUrl = config.databaseMigrationUrl ?? config.databaseUrl;
     migrationSummary = await ensureMigrations(migrationUrl, "PostgreSQL");