fix: improve subagent UI display and interruption handling (#330)

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

src/tools/impl/Bash.ts

@@ -1,6 +1,7 @@
 import type { ExecOptions } from "node:child_process";
 import { exec, spawn } from "node:child_process";
 import { promisify } from "node:util";
+import { INTERRUPTED_BY_USER } from "../../constants";
 import { backgroundProcesses, getNextBashId } from "./process_manager.js";
 import { getShellEnv } from "./shellEnv.js";
 import { LIMITS, truncateByChars } from "./truncation.js";
@@ -156,7 +157,7 @@ export async function bash(args: BashArgs): Promise<BashResult> {
 
     let errorMessage = "";
     if (isAbort) {
-      errorMessage = "User interrupted tool execution";
+      errorMessage = INTERRUPTED_BY_USER;
     } else {
       if (err.killed && err.signal === "SIGTERM")
         errorMessage = `Command timed out after ${effectiveTimeout}ms\n`;

src/tools/impl/Task.ts

@@ -20,6 +20,7 @@ interface TaskArgs {
   description: string;
   model?: string;
   toolCallId?: string; // Injected by executeTool for linking subagent to parent tool call
+  signal?: AbortSignal; // Injected by executeTool for interruption handling
 }
 
 /**
@@ -33,7 +34,8 @@ export async function task(args: TaskArgs): Promise<string> {
     "Task",
   );
 
-  const { subagent_type, prompt, description, model, toolCallId } = args;
+  const { subagent_type, prompt, description, model, toolCallId, signal } =
+    args;
 
   // Get all available subagent configs (built-in + custom)
   const allConfigs = await getAllSubagentConfigs();
@@ -54,12 +56,14 @@ export async function task(args: TaskArgs): Promise<string> {
       prompt,
       model,
       subagentId,
+      signal,
     );
 
     // Mark subagent as completed in state store
     completeSubagent(subagentId, {
       success: result.success,
       error: result.error,
+      totalTokens: result.totalTokens,
     });
 
     if (!result.success) {

src/tools/manager.ts

@@ -6,6 +6,7 @@ import {
 } from "@letta-ai/letta-client";
 import { getModelInfo } from "../agent/model";
 import { getAllSubagentConfigs } from "../agent/subagents";
+import { INTERRUPTED_BY_USER } from "../constants";
 import { telemetry } from "../telemetry";
 import { TOOL_DEFINITIONS, type ToolName } from "./toolDefinitions";
 
@@ -911,9 +912,14 @@ export async function executeTool(
       enhancedArgs = { ...enhancedArgs, signal: options.signal };
     }
 
-    // Inject toolCallId for Task tool (for linking subagents to their parent tool call)
-    if (internalName === "Task" && options?.toolCallId) {
-      enhancedArgs = { ...enhancedArgs, toolCallId: options.toolCallId };
+    // Inject toolCallId and abort signal for Task tool
+    if (internalName === "Task") {
+      if (options?.toolCallId) {
+        enhancedArgs = { ...enhancedArgs, toolCallId: options.toolCallId };
+      }
+      if (options?.signal) {
+        enhancedArgs = { ...enhancedArgs, signal: options.signal };
+      }
     }
 
     const result = await tool.fn(enhancedArgs);
@@ -925,23 +931,27 @@ export async function executeTool(
     const stderrValue = recordResult?.stderr;
     const stdout = isStringArray(stdoutValue) ? stdoutValue : undefined;
     const stderr = isStringArray(stderrValue) ? stderrValue : undefined;
+
+    // Check if tool returned a status (e.g., Bash returns status: "error" on abort)
+    const toolStatus = recordResult?.status === "error" ? "error" : "success";
+
     // Flatten the response to plain text
     const flattenedResponse = flattenToolResponse(result);
 
-    // Track tool usage (success path - we're in the try block)
+    // Track tool usage
     telemetry.trackToolUsage(
       internalName,
-      true, // Hardcoded to true since tool execution succeeded
+      toolStatus === "success",
       duration,
       flattenedResponse.length,
-      undefined, // no error_type on success
+      toolStatus === "error" ? "tool_error" : undefined,
       stderr ? stderr.join("\n") : undefined,
     );
 
     // Return the full response (truncation happens in UI layer only)
     return {
       toolReturn: flattenedResponse,
-      status: "success",
+      status: toolStatus,
       ...(stdout && { stdout }),
       ...(stderr && { stderr }),
     };
@@ -959,7 +969,7 @@ export async function executeTool(
         ? error.name
         : "unknown";
     const errorMessage = isAbort
-      ? "User interrupted tool execution"
+      ? INTERRUPTED_BY_USER
       : error instanceof Error
         ? error.message
         : String(error);