fix(pi): reduce startup skill-token overhead (#527)

packages/mosaic/src/commands/launch.ts

@@ -447,6 +447,32 @@ function discoverPiSkills(): string[] {
   return args;
 }
 
+type PiSkillMode = 'none' | 'all' | 'discover';
+
+function normalizePiSkillMode(env: NodeJS.ProcessEnv): PiSkillMode {
+  const value = env['MOSAIC_PI_SKILL_MODE']?.trim().toLowerCase();
+  if (value === 'all' || value === 'discover') return value;
+  return 'none';
+}
+
+export function buildPiSkillArgs(
+  _runtimeArgs: string[],
+  env: NodeJS.ProcessEnv = process.env,
+  discoveredSkillArgs: string[] = discoverPiSkills(),
+): string[] {
+  const mode = normalizePiSkillMode(env);
+
+  if (mode === 'discover') {
+    return [];
+  }
+
+  if (mode === 'all') {
+    return ['--no-skills', ...discoveredSkillArgs];
+  }
+
+  return ['--no-skills'];
+}
+
 function discoverPiExtension(): string[] {
   const ext = join(MOSAIC_HOME, 'runtime', 'pi', 'mosaic-extension.ts');
   return existsSync(ext) ? ['--extension', ext] : [];
@@ -523,7 +549,7 @@ function launchRuntime(runtime: RuntimeName, args: string[], yolo: boolean): nev
     case 'pi': {
       const prompt = buildRuntimePrompt('pi');
       const cliArgs = ['--append-system-prompt', prompt];
-      cliArgs.push(...discoverPiSkills());
+      cliArgs.push(...buildPiSkillArgs(args));
       cliArgs.push(...discoverPiExtension());
       if (hasMissionNoArgs) {
         cliArgs.push(missionPrompt);