diff --git a/resources/pi-agent-server.mjs b/resources/pi-agent-server.mjs
index ffbb142..361f2ff 100644
--- a/resources/pi-agent-server.mjs
+++ b/resources/pi-agent-server.mjs
@@ -177,11 +177,12 @@ async function createThreadRuntime(channel, rawOptions) {
   const appendSystemPrompts = optionValues(args, '--append-system-prompt');
   const sessionId = requiredString(optionValue(args, '--session-id'), 'Thread session id');
   const forkSessionId = optionValue(args, '--fork');
-  const extensionPaths = optionValues(args, '--extension').map((value) => path.resolve(value));
+  const [makeloreExtensionPath, ...additionalExtensionPaths] = optionValues(args, '--extension')
+    .map((value) => path.resolve(value));
   const skillPaths = optionValues(args, '--skill').map((value) => path.resolve(value));
-  if (extensionPaths.length !== 1) throw new Error('Thread requires exactly one Makelore extension');
+  if (!makeloreExtensionPath) throw new Error('Thread requires a Makelore extension');
   if (appendSystemPrompts.length !== 1) throw new Error('Thread requires exactly one Makelore language prompt');
-  const extensionModule = await import(pathToFileURL(extensionPaths[0]).href);
+  const extensionModule = await import(pathToFileURL(makeloreExtensionPath).href);
   if (typeof extensionModule.createMakeloreRuntime !== 'function') {
     throw new Error('Makelore runtime extension factory is unavailable');
   }
@@ -215,6 +216,7 @@ async function createThreadRuntime(channel, rawOptions) {
             cwd: runtimeCwd,
           })),
         }],
+        additionalExtensionPaths,
         additionalSkillPaths: skillPaths,
         noExtensions: true,
         noSkills: true,
diff --git a/tests/unit/pi-agent-server-process-real.test.ts b/tests/unit/pi-agent-server-process-real.test.ts
index 17a95f6..9ec4001 100644
--- a/tests/unit/pi-agent-server-process-real.test.ts
+++ b/tests/unit/pi-agent-server-process-real.test.ts
@@ -196,6 +196,22 @@ describe('Pi Agent Server real process', () => {
       writeFile(languagePromptPath, MAKELORE_DEFAULT_LANGUAGE_PROMPT),
     ]);
     const extensionPath = await materializeMakelorePiExtension(extensionDir);
+    const firstDeviceExtensionPath = path.join(extensionDir, 'first-device-extension.mjs');
+    const secondDeviceExtensionPath = path.join(extensionDir, 'second-device-extension.mjs');
+    await Promise.all([
+      writeFile(firstDeviceExtensionPath, [
+        'export default function (pi) {',
+        "  pi.registerCommand('first-device-ping', { description: 'First device ping', handler: async () => {} });",
+        '}',
+        '',
+      ].join('\n')),
+      writeFile(secondDeviceExtensionPath, [
+        'export default function (pi) {',
+        "  pi.registerCommand('second-device-ping', { description: 'Second device ping', handler: async () => {} });",
+        '}',
+        '',
+      ].join('\n')),
+    ]);
     const runtimeRoot = path.resolve('node_modules/@earendil-works/pi-coding-agent');
     const server = new PiAgentServerProcess({
       executablePath: process.execPath,
@@ -221,6 +237,8 @@ describe('Pi Agent Server real process', () => {
           '--system-prompt', promptPath,
           '--append-system-prompt', languagePromptPath,
           '--extension', extensionPath,
+          '--extension', firstDeviceExtensionPath,
+          '--extension', secondDeviceExtensionPath,
           '--session-id', `session-${conversationId}`,
         ],
         env: {
@@ -261,6 +279,15 @@ describe('Pi Agent Server real process', () => {
         .resolves.toMatchObject({
           data: { models: expect.arrayContaining([expect.objectContaining({ id: 'test-model' })]) },
         });
+      await expect(left.request<{ commands: Array<{ name: string; source: string }> }>({ type: 'get_commands' }))
+        .resolves.toMatchObject({
+          data: {
+            commands: expect.arrayContaining([
+              expect.objectContaining({ name: 'first-device-ping', source: 'extension' }),
+              expect.objectContaining({ name: 'second-device-ping', source: 'extension' }),
+            ]),
+          },
+        });
 
       const settled = (worker: typeof left) => new Promise<void>((resolve) => {
         const unsubscribe = worker.subscribe((event) => {