feat: Stateless subagents (#127)

src/tools/impl/Task.ts

@@ -0,0 +1,75 @@
+/**
+ * Task tool implementation
+ *
+ * Spawns specialized subagents to handle complex, multi-step tasks autonomously.
+ * Supports both built-in subagent types and custom subagents defined in .letta/agents/.
+ */
+
+import { getAllSubagentConfigs } from "../../agent/subagents";
+import { spawnSubagent } from "../../agent/subagents/manager";
+import { validateRequiredParams } from "./validation";
+
+interface TaskArgs {
+  subagent_type: string;
+  prompt: string;
+  description: string;
+  model?: string;
+}
+
+/**
+ * Format args for display (truncate prompt)
+ */
+function formatTaskArgs(args: TaskArgs): string {
+  const parts: string[] = [];
+  parts.push(`subagent_type="${args.subagent_type}"`);
+  parts.push(`description="${args.description}"`);
+  // Truncate prompt for display
+  const promptPreview =
+    args.prompt.length > 20 ? `${args.prompt.slice(0, 17)}...` : args.prompt;
+  parts.push(`prompt="${promptPreview}"`);
+  if (args.model) parts.push(`model="${args.model}"`);
+  return parts.join(", ");
+}
+
+/**
+ * Task tool - Launch a specialized subagent to handle complex tasks
+ */
+export async function task(args: TaskArgs): Promise<string> {
+  // Validate required parameters
+  validateRequiredParams(
+    args,
+    ["subagent_type", "prompt", "description"],
+    "Task",
+  );
+
+  const { subagent_type, prompt, description, model } = args;
+
+  // Print Task header FIRST so subagent output appears below it
+  console.log(`\n● Task(${formatTaskArgs(args)})\n`);
+
+  // Get all available subagent configs (built-in + custom)
+  const allConfigs = await getAllSubagentConfigs();
+
+  // Validate subagent type
+  if (!(subagent_type in allConfigs)) {
+    const available = Object.keys(allConfigs).join(", ");
+    return `Error: Invalid subagent type "${subagent_type}". Available types: ${available}`;
+  }
+
+  try {
+    const result = await spawnSubagent(
+      subagent_type,
+      prompt,
+      description,
+      model,
+    );
+
+    if (!result.success) {
+      return `Error: ${result.error || "Subagent execution failed"}`;
+    }
+
+    return result.report;
+  } catch (error) {
+    return `Error: ${error instanceof Error ? error.message : String(error)}`;
+  }
+}