feat(pi): add persistent Mosaic /goal controller (#1152)

packages/mosaic/src/commands/launch.spec.ts

@@ -5,6 +5,7 @@ import { tmpdir } from 'node:os';
 import { join } from 'node:path';
 import {
   buildPiSkillArgs,
+  discoverPiExtensionArgs,
   enumerateSkillDirs,
   piForceSkillNames,
   registerRuntimeLaunchers,
@@ -178,6 +179,52 @@ describe('buildPiSkillArgs', () => {
   });
 });
 
+describe('discoverPiExtensionArgs', () => {
+  it('loads the core and goal extensions in deterministic order from Mosaic home', () => {
+    const root = mkdtempSync(join(tmpdir(), 'mosaic-pi-extensions-'));
+    const runtimeDir = join(root, 'runtime', 'pi');
+    mkdirSync(runtimeDir, { recursive: true });
+    writeFileSync(join(runtimeDir, 'goal-extension.ts'), '// goal\n');
+    writeFileSync(join(runtimeDir, 'mosaic-extension.ts'), '// core\n');
+
+    try {
+      expect(discoverPiExtensionArgs(root)).toEqual([
+        '--extension',
+        join(runtimeDir, 'mosaic-extension.ts'),
+        '--extension',
+        join(runtimeDir, 'goal-extension.ts'),
+      ]);
+    } finally {
+      rmSync(root, { recursive: true, force: true });
+    }
+  });
+
+  it('remains backward-compatible when the optional goal extension is absent', () => {
+    const root = mkdtempSync(join(tmpdir(), 'mosaic-pi-extensions-'));
+    const runtimeDir = join(root, 'runtime', 'pi');
+    mkdirSync(runtimeDir, { recursive: true });
+    writeFileSync(join(runtimeDir, 'mosaic-extension.ts'), '// core\n');
+
+    try {
+      expect(discoverPiExtensionArgs(root)).toEqual([
+        '--extension',
+        join(runtimeDir, 'mosaic-extension.ts'),
+      ]);
+    } finally {
+      rmSync(root, { recursive: true, force: true });
+    }
+  });
+
+  it('emits no extension arguments when Mosaic runtime assets are absent', () => {
+    const root = mkdtempSync(join(tmpdir(), 'mosaic-pi-extensions-'));
+    try {
+      expect(discoverPiExtensionArgs(root)).toEqual([]);
+    } finally {
+      rmSync(root, { recursive: true, force: true });
+    }
+  });
+});
+
 describe('enumerateSkillDirs (real FS)', () => {
   let root: string;
 

packages/mosaic/src/commands/launch.ts

@@ -715,9 +715,15 @@ export function buildPiSkillArgs(
   return ['--no-skills', ...forcedSkillArgs];
 }
 
-function discoverPiExtension(): string[] {
-  const ext = join(MOSAIC_HOME, 'runtime', 'pi', 'mosaic-extension.ts');
-  return existsSync(ext) ? ['--extension', ext] : [];
+const PI_EXTENSION_FILES = ['mosaic-extension.ts', 'goal-extension.ts'] as const;
+
+export function discoverPiExtensionArgs(mosaicHome: string = MOSAIC_HOME): string[] {
+  const args: string[] = [];
+  for (const fileName of PI_EXTENSION_FILES) {
+    const extensionPath = join(mosaicHome, 'runtime', 'pi', fileName);
+    if (existsSync(extensionPath)) args.push('--extension', extensionPath);
+  }
+  return args;
 }
 
 // ─── Launch functions ────────────────────────────────────────────────────────
@@ -792,7 +798,7 @@ function launchRuntime(runtime: RuntimeName, args: string[], yolo: boolean): nev
       const prompt = buildRuntimePrompt('pi');
       const cliArgs = ['--append-system-prompt', prompt];
       cliArgs.push(...buildPiSkillArgs(args));
-      cliArgs.push(...discoverPiExtension());
+      cliArgs.push(...discoverPiExtensionArgs());
       if (hasMissionNoArgs) {
         cliArgs.push(missionPrompt);
       } else {