From acc5581b6bbeae60ff5b8a665a67a0b14d66ee2b Mon Sep 17 00:00:00 2001
From: Alex Hancock <alexhancock@block.xyz>
Date: Mon, 10 Nov 2025 16:46:53 -0500
Subject: [PATCH] fix: disallow runaway subagent chains (#5659)

---
 crates/goose/src/agents/agent.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/crates/goose/src/agents/agent.rs b/crates/goose/src/agents/agent.rs
index 0d28297b06..bae2e8cc9d 100644
--- a/crates/goose/src/agents/agent.rs
+++ b/crates/goose/src/agents/agent.rs
@@ -394,6 +394,20 @@ impl Agent {
         cancellation_token: Option<CancellationToken>,
         session: &Session,
     ) -> (String, Result<ToolCallResult, ErrorData>) {
+        if session.session_type == crate::session::SessionType::SubAgent
+            && (tool_call.name == DYNAMIC_TASK_TOOL_NAME_PREFIX
+                || tool_call.name == SUBAGENT_EXECUTE_TASK_TOOL_NAME)
+        {
+            return (
+                request_id,
+                Err(ErrorData::new(
+                    ErrorCode::INVALID_REQUEST,
+                    "Subagents cannot create other subagents".to_string(),
+                    None,
+                )),
+            );
+        }
+
         if tool_call.name == PLATFORM_MANAGE_SCHEDULE_TOOL_NAME {
             let arguments = tool_call
                 .arguments