feat: add truncation to Task tool output and auto-cleanup overflow files (#588)

Co-authored-by: Letta <noreply@letta.com>

src/tools/impl/Task.ts

@@ -16,6 +16,7 @@ import {
   generateSubagentId,
   registerSubagent,
 } from "../../cli/helpers/subagentState.js";
+import { LIMITS, truncateByChars } from "./truncation.js";
 import { validateRequiredParams } from "./validation";
 
 interface TaskArgs {
@@ -114,7 +115,18 @@ export async function task(args: TaskArgs): Promise<string> {
       .filter(Boolean)
       .join(" ");
 
-    return `${header}\n\n${result.report}`;
+    const fullOutput = `${header}\n\n${result.report}`;
+    const userCwd = process.env.USER_CWD || process.cwd();
+
+    // Apply truncation to prevent excessive token usage (same pattern as Bash tool)
+    const { content: truncatedOutput } = truncateByChars(
+      fullOutput,
+      LIMITS.TASK_OUTPUT_CHARS,
+      "Task",
+      { workingDirectory: userCwd, toolName: "Task" },
+    );
+
+    return truncatedOutput;
   } catch (error) {
     const errorMessage = error instanceof Error ? error.message : String(error);
     completeSubagent(subagentId, { success: false, error: errorMessage });

src/tools/impl/overflow.ts

@@ -113,17 +113,33 @@ export function cleanupOldOverflowFiles(
     return 0;
   }
 
-  const files = fs.readdirSync(overflowDir);
+  let files: string[];
+  try {
+    files = fs.readdirSync(overflowDir);
+  } catch {
+    // Directory may have been deleted or become inaccessible
+    return 0;
+  }
+
   const now = Date.now();
   let deletedCount = 0;
 
   for (const file of files) {
     const filePath = path.join(overflowDir, file);
-    const stats = fs.statSync(filePath);
+    try {
+      const stats = fs.statSync(filePath);
 
-    if (now - stats.mtimeMs > maxAgeMs) {
-      fs.unlinkSync(filePath);
-      deletedCount++;
+      // Skip directories (shouldn't exist, but be safe)
+      if (stats.isDirectory()) {
+        continue;
+      }
+
+      if (now - stats.mtimeMs > maxAgeMs) {
+        fs.unlinkSync(filePath);
+        deletedCount++;
+      }
+    } catch {
+      // File may have been deleted, or permission error - skip it
     }
   }
 

src/tools/impl/truncation.ts

@@ -10,6 +10,7 @@ import { OVERFLOW_CONFIG, writeOverflowFile } from "./overflow.js";
 export const LIMITS = {
   // Command output limits
   BASH_OUTPUT_CHARS: 30_000, // 30K characters for bash/shell output
+  TASK_OUTPUT_CHARS: 30_000, // 30K characters for subagent task output
 
   // File reading limits
   READ_MAX_LINES: 2_000, // Max lines per file read