add a CLIENT_CONFIG to the client, serve from BE with env vars

server/src/app.ts

@@ -52,6 +52,13 @@ export const createApp = ({
 
 	app.use(createStatusPageDocumentCsp(allowedOrigin));
 
+	// Client runtime config; registered before express.static so it shadows the
+	// fallback config.js in the client build output
+	const clientConfigScript = `window.__CHECKMATE_CONFIG__ = ${JSON.stringify(envSettings.clientConfig).replace(/</g, "\\u003c")};`;
+	app.get("/config.js", (req, res) => {
+		res.set("Cache-Control", "no-cache").type("application/javascript").send(clientConfigScript);
+	});
+
 	app.use(express.static(frontendPath));
 
 	app.use(express.json());

server/src/config/envValidation.ts

@@ -1,5 +1,5 @@
 import { z } from "zod";
-import { DbTypes, QueueModes } from "@/domain/app-settings/app-settings.type.js";
+import { DbTypes, LogLevels, QueueModes } from "@/domain/app-settings/app-settings.type.js";
 import { booleanCoercion } from "@/api/validation/shared.js";
 import { ILogger } from "@/utils/logger.js";
 
@@ -9,7 +9,7 @@ const envSchema = z.object({
 	// Port for worker health checks
 	HEALTH_PORT: z.string().default("52346"),
 	NODE_ENV: z.enum(["development", "production", "test"]).default("development"),
-	LOG_LEVEL: z.enum(["error", "warn", "info", "debug"]).default("debug"),
+	LOG_LEVEL: z.enum(LogLevels).default("debug"),
 
 	// Database
 	DB_CONNECTION_STRING: z.string().min(1, "Database connection string is required"),
@@ -25,6 +25,12 @@ const envSchema = z.object({
 	// Client Configuration
 	CLIENT_HOST: z.string().url("CLIENT_HOST must be a valid URL"),
 
+	// Client runtime config overrides, rendered into GET /config.js; unset keys are
+	// omitted and the client uses its same-origin defaults
+	CLIENT_CONFIG_API_BASE_URL: z.string().optional(),
+	CLIENT_CONFIG_CLIENT_HOST: z.string().url("CLIENT_CONFIG_CLIENT_HOST must be a valid URL").optional(),
+	CLIENT_CONFIG_LOG_LEVEL: z.enum(LogLevels).optional(),
+
 	// Optional
 	ORIGIN: z.string().optional(),
 

server/src/domain/app-settings/app-settings.service.ts

@@ -1,5 +1,5 @@
 import { ISettingsRepository } from "@/domain/app-settings/app-settings-repository.interface.js";
-import { Settings, SettingsUpdate, type DbType, type QueueMode } from "@/domain/app-settings/app-settings.type.js";
+import { Settings, SettingsUpdate, type ClientRuntimeConfig, type DbType, type QueueMode } from "@/domain/app-settings/app-settings.type.js";
 import { AppError } from "@/utils/AppError.js";
 import { ValidatedEnv } from "@/config/envValidation.js";
 import type { StringValue } from "ms";
@@ -16,6 +16,7 @@ export type EnvConfig = {
 	queueMode: QueueMode;
 	queuePrimaryProcesses: boolean;
 	statusPageThemesEnabled: boolean;
+	clientConfig: ClientRuntimeConfig;
 };
 
 export interface ISettingsService {
@@ -44,6 +45,11 @@ export class SettingsService implements ISettingsService {
 			queueMode: env.QUEUE_MODE,
 			queuePrimaryProcesses: env.QUEUE_PRIMARY_PROCESSES,
 			statusPageThemesEnabled: env.STATUS_PAGE_THEMES_ENABLED,
+			clientConfig: {
+				...(env.CLIENT_CONFIG_API_BASE_URL && { apiBaseUrl: env.CLIENT_CONFIG_API_BASE_URL }),
+				...(env.CLIENT_CONFIG_CLIENT_HOST && { clientHost: env.CLIENT_CONFIG_CLIENT_HOST }),
+				...(env.CLIENT_CONFIG_LOG_LEVEL && { logLevel: env.CLIENT_CONFIG_LOG_LEVEL }),
+			},
 		};
 	}
 

server/src/domain/app-settings/app-settings.type.ts

@@ -4,6 +4,17 @@ export type DbType = (typeof DbTypes)[number];
 export const QueueModes = ["primary", "worker"] as const;
 export type QueueMode = (typeof QueueModes)[number];
 
+export const LogLevels = ["error", "warn", "info", "debug"] as const;
+export type LogLevel = (typeof LogLevels)[number];
+
+// Rendered into GET /config.js as window.__CHECKMATE_CONFIG__; keys left unset
+// fall back to the client's same-origin defaults.
+export type ClientRuntimeConfig = {
+	apiBaseUrl?: string;
+	clientHost?: string;
+	logLevel?: LogLevel;
+};
+
 export interface SettingsThresholds {
 	cpu?: number;
 	memory?: number;