diff --git a/src/lib/components/chat/Chat.svelte b/src/lib/components/chat/Chat.svelte
index 9ccae09188..4883c4a219 100644
--- a/src/lib/components/chat/Chat.svelte
+++ b/src/lib/components/chat/Chat.svelte
@@ -1071,10 +1071,12 @@
 		lastTerminalSkillSelector = $selectedTerminalId;
 	}
 
-	let settingDefaults = false;
+	let settingDefaults: Promise<void> | null = null;
 	const setDefaults = async () => {
-		if (settingDefaults) return;
-		settingDefaults = true;
+		// Concurrent callers must wait, or the earlier run overwrites what they write afterwards
+		if (settingDefaults) return settingDefaults;
+		let resolveDefaults = () => {};
+		settingDefaults = new Promise<void>((resolve) => (resolveDefaults = resolve));
 
 		try {
 			if (!$tools) {
@@ -1217,7 +1219,8 @@
 				}
 			}
 		} finally {
-			settingDefaults = false;
+			settingDefaults = null;
+			resolveDefaults();
 		}
 	};