diff --git a/extensions/copilot/src/extension/chat/vscode-node/chatHookService.ts b/extensions/copilot/src/extension/chat/vscode-node/chatHookService.ts
index a35158b37d2..b6b9501a871 100644
--- a/extensions/copilot/src/extension/chat/vscode-node/chatHookService.ts
+++ b/extensions/copilot/src/extension/chat/vscode-node/chatHookService.ts
@@ -501,6 +501,16 @@ export class ChatHookService implements IChatHookService {
 			token
 		);
 
+		// Running the hook can take a long time because it spawns external, user-configured
+		// commands. If the request was cancelled while the hook ran, the response stream is
+		// already closed and writing hook progress to it throws "Response stream has been
+		// closed". The caller only checks cancellation before invoking the hook, so re-check
+		// here after the await and skip result processing - a cancelled turn never consumes
+		// the result anyway.
+		if (token?.isCancellationRequested) {
+			return undefined;
+		}
+
 		if (results.length === 0) {
 			return undefined;
 		}