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

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

src/cli/helpers/accumulator.ts

@@ -5,6 +5,7 @@
 // - Exposes `onChunk` to feed SDK events and `toLines` to render.
 
 import type { LettaStreamingResponse } from "@letta-ai/letta-client/resources/agents/messages";
+import { INTERRUPTED_BY_USER } from "../../constants";
 
 // One line per transcript row. Tool calls evolve in-place.
 // For tool call returns, merge into the tool call matching the toolCallId
@@ -172,7 +173,7 @@ export function markIncompleteToolsAsCancelled(b: Buffers) {
         ...line,
         phase: "finished" as const,
         resultOk: false,
-        resultText: "Interrupted by user",
+        resultText: INTERRUPTED_BY_USER,
       };
       b.byId.set(id, updatedLine);
     }

src/cli/helpers/subagentDisplay.ts

@@ -8,7 +8,7 @@
  * Format tool count and token statistics for display
  *
  * @param toolCount - Number of tool calls
- * @param totalTokens - Total tokens used
+ * @param totalTokens - Total tokens used (0 or undefined means no data available)
  * @param isRunning - If true, shows "—" for tokens (since usage is only available at end)
  */
 export function formatStats(
@@ -16,12 +16,19 @@ export function formatStats(
   totalTokens: number,
   isRunning = false,
 ): string {
-  const tokenStr = isRunning
-    ? "—"
-    : totalTokens >= 1000
+  const toolStr = `${toolCount} tool use${toolCount !== 1 ? "s" : ""}`;
+
+  // Only show token count if we have actual data (not running and totalTokens > 0)
+  const hasTokenData = !isRunning && totalTokens > 0;
+  if (!hasTokenData) {
+    return toolStr;
+  }
+
+  const tokenStr =
+    totalTokens >= 1000
       ? `${(totalTokens / 1000).toFixed(1)}k`
       : String(totalTokens);
-  return `${toolCount} tool use${toolCount !== 1 ? "s" : ""} · ${tokenStr} tokens`;
+  return `${toolStr} · ${tokenStr} tokens`;
 }
 
 /**

src/cli/helpers/subagentState.ts

@@ -180,7 +180,7 @@ export function addToolCall(
  */
 export function completeSubagent(
   id: string,
-  result: { success: boolean; error?: string },
+  result: { success: boolean; error?: string; totalTokens?: number },
 ): void {
   const agent = store.agents.get(id);
   if (!agent) return;
@@ -191,6 +191,7 @@ export function completeSubagent(
     status: result.success ? "completed" : "error",
     error: result.error,
     durationMs: Date.now() - agent.startTime,
+    totalTokens: result.totalTokens ?? agent.totalTokens,
   } as SubagentState;
   store.agents.set(id, updatedAgent);
   notifyListeners();