diff --git a/package.json b/package.json
index 388f99e2..723881ae 100644
--- a/package.json
+++ b/package.json
@@ -29,7 +29,7 @@
     "dev": "node scripts/dev-server.mjs",
     "postinstall": "node scripts/fix-node-pty-permissions.mjs",
     "start": "node dist/cli.js serve",
-    "test": "tsx src/config.test.ts && tsx src/onboarding.test.ts && tsx src/cli-workspace.test.ts && tsx src/request-meta.test.ts && tsx src/incoming-artifacts.test.ts && tsx src/artifact-download.test.ts && tsx src/ui/card-types.test.ts && tsx src/ui/patch-display.test.ts && tsx src/ui/tool-display.test.ts && tsx src/apply-patch.test.ts && tsx src/process-platform.test.ts && tsx src/process-sessions.test.ts && tsx src/mcp-sessions.test.ts && tsx src/server-shutdown.test.ts && tsx src/local-agent-config.test.ts && tsx src/local-agent-catalog.test.ts && tsx src/local-agent-presentation.test.ts && tsx src/local-agent-runtime.test.ts && tsx src/local-agent-daemon-lifecycle.test.ts && tsx src/local-agent-daemon-protocol.test.ts && tsx src/local-agent-daemon.test.ts && tsx src/local-agent-codex.test.ts && tsx src/local-agent-opencode.test.ts && tsx src/local-agent-acp.test.ts && tsx src/local-agent-grok.test.ts && tsx src/local-agent-pi-sandbox.test.ts && tsx src/local-agent-pi.test.ts && tsx src/local-agent-claude.test.ts && tsx src/local-agent-adapters.test.ts && tsx src/local-agent-availability.test.ts && tsx src/local-agent-profiles.test.ts && tsx src/local-agent-targets.test.ts && tsx src/local-agent-store.test.ts && tsx src/local-agent-manager.test.ts && tsx src/roots.test.ts && tsx src/skills.test.ts && tsx src/workspaces.test.ts && tsx src/workspace-conversation.test.ts && tsx src/review-checkpoints.test.ts && tsx src/server.test.ts && tsx src/oauth-store.test.ts && tsx src/cli.test.ts",
+    "test": "tsx src/user-config.test.ts && tsx src/config.test.ts && tsx src/onboarding.test.ts && tsx src/cli-workspace.test.ts && tsx src/request-meta.test.ts && tsx src/incoming-artifacts.test.ts && tsx src/artifact-download.test.ts && tsx src/ui/card-types.test.ts && tsx src/ui/patch-display.test.ts && tsx src/ui/tool-display.test.ts && tsx src/apply-patch.test.ts && tsx src/process-platform.test.ts && tsx src/process-sessions.test.ts && tsx src/mcp-sessions.test.ts && tsx src/server-shutdown.test.ts && tsx src/local-agent-config.test.ts && tsx src/local-agent-catalog.test.ts && tsx src/local-agent-presentation.test.ts && tsx src/local-agent-runtime.test.ts && tsx src/local-agent-daemon-lifecycle.test.ts && tsx src/local-agent-daemon-protocol.test.ts && tsx src/local-agent-daemon.test.ts && tsx src/local-agent-codex.test.ts && tsx src/local-agent-opencode.test.ts && tsx src/local-agent-acp.test.ts && tsx src/local-agent-grok.test.ts && tsx src/local-agent-pi-sandbox.test.ts && tsx src/local-agent-pi.test.ts && tsx src/local-agent-claude.test.ts && tsx src/local-agent-adapters.test.ts && tsx src/local-agent-availability.test.ts && tsx src/local-agent-profiles.test.ts && tsx src/local-agent-targets.test.ts && tsx src/local-agent-store.test.ts && tsx src/local-agent-manager.test.ts && tsx src/roots.test.ts && tsx src/skills.test.ts && tsx src/workspaces.test.ts && tsx src/workspace-conversation.test.ts && tsx src/review-checkpoints.test.ts && tsx src/server.test.ts && tsx src/oauth-store.test.ts && tsx src/cli.test.ts",
     "typecheck": "tsc -p tsconfig.json --noEmit"
   },
   "keywords": [],
diff --git a/src/local-agent-config.ts b/src/local-agent-config.ts
index 3f1de5aa..538355d9 100644
--- a/src/local-agent-config.ts
+++ b/src/local-agent-config.ts
@@ -11,7 +11,7 @@ const providerSchema = z.object({
   effort: z.string().trim().min(1).optional(),
 }).strict();
 
-const subagentsSchema = z.object({
+export const subagentsConfigSchema = z.object({
   enabled: z.boolean(),
   providers: z.array(providerSchema),
 }).strict().superRefine((value, context) => {
@@ -28,9 +28,14 @@ const subagentsSchema = z.object({
   }
 });
 
+export const storedSubagentsConfigSchema = z.union([
+  z.boolean(),
+  subagentsConfigSchema,
+]);
+
 export type SubagentProviderConfig = z.infer<typeof providerSchema>;
-export type SubagentsConfig = z.infer<typeof subagentsSchema>;
-export type StoredSubagentsConfig = boolean | SubagentsConfig;
+export type SubagentsConfig = z.infer<typeof subagentsConfigSchema>;
+export type StoredSubagentsConfig = z.infer<typeof storedSubagentsConfigSchema>;
 
 export function resolveSubagentsConfig(
   value: unknown,
@@ -40,7 +45,7 @@ export function resolveSubagentsConfig(
     ? { enabled: false, providers: [] }
     : typeof value === "boolean"
       ? legacySubagentsConfig(value)
-      : subagentsSchema.parse(value);
+      : subagentsConfigSchema.parse(value);
   return {
     ...stored,
     enabled: env.DEVSPACE_SUBAGENTS === undefined
diff --git a/src/user-config.test.ts b/src/user-config.test.ts
new file mode 100644
index 00000000..f13ca46f
--- /dev/null
+++ b/src/user-config.test.ts
@@ -0,0 +1,41 @@
+import assert from "node:assert/strict";
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { loadDevspaceFiles } from "./user-config.js";
+
+const configDir = mkdtempSync(join(tmpdir(), "devspace-user-config-test-"));
+const env = { DEVSPACE_CONFIG_DIR: configDir };
+
+try {
+  writeFileSync(join(configDir, "config.json"), JSON.stringify({
+    port: 8787,
+    subagents: {
+      enabled: true,
+      providers: [{ id: "codex", enabled: true }],
+    },
+  }));
+  writeFileSync(join(configDir, "auth.json"), JSON.stringify({
+    ownerToken: "test-owner-token",
+  }));
+
+  assert.deepEqual(loadDevspaceFiles(env).config, {
+    port: 8787,
+    subagents: {
+      enabled: true,
+      providers: [{ id: "codex", enabled: true }],
+    },
+  });
+  assert.equal(loadDevspaceFiles(env).auth.ownerToken, "test-owner-token");
+
+  writeFileSync(join(configDir, "config.json"), JSON.stringify({ port: "8787" }));
+  assert.throws(() => loadDevspaceFiles(env), /expected number/i);
+
+  writeFileSync(join(configDir, "config.json"), JSON.stringify({ unknownSetting: true }));
+  assert.equal(loadDevspaceFiles(env).config.unknownSetting, true);
+
+  writeFileSync(join(configDir, "config.json"), "{");
+  assert.throws(() => loadDevspaceFiles(env), /Unable to read .*config\.json/);
+} finally {
+  rmSync(configDir, { recursive: true, force: true });
+}
diff --git a/src/user-config.ts b/src/user-config.ts
index 98d05ac6..506b468c 100644
--- a/src/user-config.ts
+++ b/src/user-config.ts
@@ -7,26 +7,30 @@ import {
 } from "node:fs";
 import { homedir } from "node:os";
 import { join, resolve } from "node:path";
+import * as z from "zod/v4";
 import { expandHomePath } from "./roots.js";
-import type { StoredSubagentsConfig } from "./local-agent-config.js";
-
-export interface DevspaceUserConfig {
-  host?: string;
-  port?: number;
-  allowedRoots?: string[];
-  publicBaseUrl?: string | null;
-  allowedHosts?: string[];
-  stateDir?: string;
-  worktreeRoot?: string;
-  artifactsEnabled?: boolean;
-  artifactMaxFileBytes?: number;
-  agentDir?: string;
-  subagents?: StoredSubagentsConfig;
-}
+import { storedSubagentsConfigSchema } from "./local-agent-config.js";
 
-export interface DevspaceAuthConfig {
-  ownerToken?: string;
-}
+const devspaceUserConfigSchema = z.object({
+  host: z.string().optional(),
+  port: z.number().optional(),
+  allowedRoots: z.array(z.string()).optional(),
+  publicBaseUrl: z.string().nullable().optional(),
+  allowedHosts: z.array(z.string()).optional(),
+  stateDir: z.string().optional(),
+  worktreeRoot: z.string().optional(),
+  artifactsEnabled: z.boolean().optional(),
+  artifactMaxFileBytes: z.number().optional(),
+  agentDir: z.string().optional(),
+  subagents: storedSubagentsConfigSchema.optional(),
+}).passthrough();
+
+const devspaceAuthConfigSchema = z.object({
+  ownerToken: z.string().optional(),
+}).passthrough();
+
+export type DevspaceUserConfig = z.infer<typeof devspaceUserConfigSchema>;
+export type DevspaceAuthConfig = z.infer<typeof devspaceAuthConfigSchema>;
 
 export interface DevspaceFiles {
   dir: string;
@@ -71,8 +75,8 @@ export function loadDevspaceFiles(env: NodeJS.ProcessEnv = process.env): Devspac
     authPath,
     configExists,
     authExists,
-    config: configExists ? readJsonFile<DevspaceUserConfig>(configPath) : {},
-    auth: authExists ? readJsonFile<DevspaceAuthConfig>(authPath) : {},
+    config: configExists ? readJsonFile(configPath, devspaceUserConfigSchema) : {},
+    auth: authExists ? readJsonFile(authPath, devspaceAuthConfigSchema) : {},
   };
 }
 
@@ -100,9 +104,9 @@ export function generateOwnerToken(): string {
   return randomBytes(32).toString("base64url");
 }
 
-function readJsonFile<T>(filePath: string): T {
+function readJsonFile<T>(filePath: string, schema: z.ZodType<T>): T {
   try {
-    return JSON.parse(readFileSync(filePath, "utf8")) as T;
+    return schema.parse(JSON.parse(readFileSync(filePath, "utf8")) as unknown);
   } catch (error) {
     const reason = error instanceof Error ? error.message : String(error);
     throw new Error(`Unable to read ${filePath}: ${reason}`);