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) {