fix(agent): ignore late tool progress updates

closes #5573

packages/agent/src/agent-loop.ts

@@ -631,6 +631,7 @@ async function executePreparedToolCall(
 	emit: AgentEventSink,
 ): Promise<ExecutedToolCallOutcome> {
 	const updateEvents: Promise<void>[] = [];
+	let acceptingUpdates = true;
 
 	try {
 		const result = await prepared.tool.execute(
@@ -638,6 +639,7 @@ async function executePreparedToolCall(
 			prepared.args as never,
 			signal,
 			(partialResult) => {
+				if (!acceptingUpdates) return;
 				updateEvents.push(
 					Promise.resolve(
 						emit({
@@ -651,14 +653,18 @@ async function executePreparedToolCall(
 				);
 			},
 		);
+		acceptingUpdates = false;
 		await Promise.all(updateEvents);
 		return { result, isError: false };
 	} catch (error) {
+		acceptingUpdates = false;
 		await Promise.all(updateEvents);
 		return {
 			result: createErrorToolResult(error instanceof Error ? error.message : String(error)),
 			isError: true,
 		};
+	} finally {
+		acceptingUpdates = false;
 	}
 }
 

packages/agent/src/types.ts

@@ -354,7 +354,12 @@ export interface AgentToolResult<T> {
 	terminate?: boolean;
 }
 
-/** Callback used by tools to stream partial execution updates. */
+/**
+ * Callback used by tools to stream partial execution updates.
+ *
+ * The callback is scoped to the current `execute()` invocation. Calls made after
+ * the tool promise settles are ignored.
+ */
 export type AgentToolUpdateCallback<T = any> = (partialResult: AgentToolResult<T>) => void;
 
 /** Tool definition used by the agent runtime. */