diff --git a/build.ts b/build.ts
index 20cab98..437f6d6 100644
--- a/build.ts
+++ b/build.ts
@@ -3,13 +3,14 @@ import { readFileSync, writeFileSync } from 'fs';
 const pkg = JSON.parse(readFileSync('package.json', 'utf-8'));
 const VERSION = process.env.VERSION ?? pkg.version;
 const OUT = 'dist/mmx.mjs';
+const DEV_BUILD = process.argv.includes('--dev');
 
 await Bun.build({
   entrypoints: ['src/main.ts'],
   outdir: 'dist',
   naming: 'mmx.mjs',
   target: 'node',
-  minify: true,
+  minify: !DEV_BUILD,
   define: { 'process.env.CLI_VERSION': JSON.stringify(VERSION) },
 });
 
diff --git a/package.json b/package.json
index ba9efc7..b51688b 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,7 @@
   "scripts": {
     "dev": "bun run src/main.ts",
     "build": "bun run build.ts",
-    "build:dev": "bun build src/main.ts --outfile dist/mmx.mjs --target node --minify --define \"process.env.CLI_VERSION='1.0.4'\" && printf '#!/usr/bin/env node\\n' | cat - dist/mmx.mjs > dist/tmp && mv dist/tmp dist/mmx.mjs && chmod +x dist/mmx.mjs",
+    "build:dev": "bun run build.ts --dev",
     "prepublishOnly": "bun run build",
     "lint": "eslint src/ test/",
     "typecheck": "tsc --noEmit",
diff --git a/src/client/http.ts b/src/client/http.ts
index 8382b55..7e327d6 100644
--- a/src/client/http.ts
+++ b/src/client/http.ts
@@ -5,6 +5,7 @@ import { ExitCode } from '../errors/codes';
 import { resolveCredential } from '../auth/resolver';
 import { mapApiError } from '../errors/api';
 import { maybeShowStatusBar } from '../output/status-bar';
+import { CLI_VERSION } from '../version';
 
 export interface RequestOpts {
   url: string;
@@ -20,9 +21,8 @@ export interface RequestOpts {
 export async function request(config: Config, opts: RequestOpts): Promise<Response> {
   const isFormData = typeof FormData !== 'undefined' && opts.body instanceof FormData;
 
-  const version = process.env.CLI_VERSION ?? '1.0.4';
   const headers: Record<string, string> = {
-    'User-Agent': `mmx-cli/${version}`,
+    'User-Agent': `mmx-cli/${CLI_VERSION}`,
     ...opts.headers,
   };
 
diff --git a/src/commands/update.ts b/src/commands/update.ts
index ca43689..d4b3c9a 100644
--- a/src/commands/update.ts
+++ b/src/commands/update.ts
@@ -1,6 +1,5 @@
 import { defineCommand } from '../command';
-
-const CLI_VERSION = process.env.CLI_VERSION ?? '0.0.0';
+import { CLI_VERSION } from '../version';
 
 export default defineCommand({
   name: 'update',
diff --git a/src/main.ts b/src/main.ts
index cd7f630..67bd2c3 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -8,8 +8,7 @@ import { REGIONS, type Region } from './config/schema';
 import { checkForUpdate, getPendingUpdateNotification } from './update/checker';
 import { loadCredentials } from './auth/credentials';
 import { ensureApiKey } from './auth/setup';
-
-const CLI_VERSION = process.env.CLI_VERSION ?? '1.0.4';
+import { CLI_VERSION } from './version';
 
 // Handle Ctrl+C gracefully
 process.on('SIGINT', () => {
diff --git a/src/version.ts b/src/version.ts
new file mode 100644
index 0000000..d20aab9
--- /dev/null
+++ b/src/version.ts
@@ -0,0 +1,3 @@
+import pkg from '../package.json' with { type: 'json' };
+
+export const CLI_VERSION = process.env.CLI_VERSION ?? pkg.version;
diff --git a/test/client/http.test.ts b/test/client/http.test.ts
index f59f882..07c0aeb 100644
--- a/test/client/http.test.ts
+++ b/test/client/http.test.ts
@@ -1,5 +1,6 @@
 import { describe, it, expect, afterEach } from 'bun:test';
 import { requestJson } from '../../src/client/http';
+import { CLI_VERSION } from '../../src/version';
 import { createMockServer, jsonResponse, type MockServer } from '../helpers/mock-server';
 import type { Config } from '../../src/config/schema';
 
@@ -28,9 +29,13 @@ describe('HTTP client', () => {
   });
 
   it('makes authenticated GET request', async () => {
+    let userAgent: string | null = null;
     server = createMockServer({
       routes: {
-        '/v1/test': () => jsonResponse({ result: 'ok' }),
+        '/v1/test': (req) => {
+          userAgent = req.headers.get('user-agent');
+          return jsonResponse({ result: 'ok' });
+        },
       },
     });
 
@@ -40,6 +45,7 @@ describe('HTTP client', () => {
     });
 
     expect(result.result).toBe('ok');
+    expect(userAgent ?? '').toBe(`mmx-cli/${CLI_VERSION}`);
   });
 
   it('makes POST request with body', async () => {
diff --git a/test/version.test.ts b/test/version.test.ts
new file mode 100644
index 0000000..b3f18de
--- /dev/null
+++ b/test/version.test.ts
@@ -0,0 +1,22 @@
+import { describe, it, expect } from 'bun:test';
+import { readFileSync } from 'fs';
+import { spawnSync } from 'child_process';
+import { CLI_VERSION } from '../src/version';
+
+const packageVersion = (JSON.parse(readFileSync('package.json', 'utf-8')) as { version: string }).version;
+
+describe('CLI version', () => {
+  it('uses package.json as the source version when no build override is present', () => {
+    expect(CLI_VERSION).toBe(packageVersion);
+  });
+
+  it('prints the package version in dev mode', () => {
+    const result = spawnSync(process.execPath, ['src/main.ts', '--version'], {
+      cwd: process.cwd(),
+      encoding: 'utf-8',
+    });
+
+    expect(result.status).toBe(0);
+    expect(result.stdout.trim()).toBe(`mmx ${packageVersion}`);
+  });
+});