diff --git a/packages/pi-coding-agent/src/core/agent-session.ts b/packages/pi-coding-agent/src/core/agent-session.ts
index 6e0910971..203517525 100644
--- a/packages/pi-coding-agent/src/core/agent-session.ts
+++ b/packages/pi-coding-agent/src/core/agent-session.ts
@@ -1214,17 +1214,16 @@ export class AgentSession {
 			]);
 		}
 
-		// If streaming, queue via steer() or followUp() based on option
+		// If streaming, queue via steer() or followUp() based on option.
+		// Default to followUp when no streamingBehavior is given — this covers
+		// user prompts that arrive while a system-triggered turn (e.g. autonomous
+		// dispatch at startup) is already running. The user's message queues as
+		// a clean new turn after the current one finishes, not steered into it.
 		if (this.isStreaming) {
-			if (!options?.streamingBehavior) {
-				throw new Error(
-					"Agent is already processing. Please wait for it to finish before sending another message.",
-				);
-			}
-			if (options.streamingBehavior === "followUp") {
-				await this._queueFollowUp(expandedText, currentImages);
-			} else {
+			if (options?.streamingBehavior === "steer") {
 				await this._queueSteer(expandedText, currentImages);
+			} else {
+				await this._queueFollowUp(expandedText, currentImages);
 			}
 			return;
 		}