From 2b8ccd4a0015fe83dd35d3040d286680d3d8ce57 Mon Sep 17 00:00:00 2001
From: Bastien Jacot-Guillarmod <bjacotg@google.com>
Date: Wed, 4 Mar 2026 00:43:18 -0800
Subject: [PATCH] chore: Exclude `BaseAgent.parent_agent` from serialization

Otherwise, serialization fails due to circular references.

PiperOrigin-RevId: 878339838
---
 src/google/adk/agents/base_agent.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/google/adk/agents/base_agent.py b/src/google/adk/agents/base_agent.py
index 3d0a14d4..dec85690 100644
--- a/src/google/adk/agents/base_agent.py
+++ b/src/google/adk/agents/base_agent.py
@@ -122,7 +122,9 @@ class BaseAgent(BaseModel):
   One-line description is enough and preferred.
   """
 
-  parent_agent: Optional[BaseAgent] = Field(default=None, init=False)
+  parent_agent: Optional[BaseAgent] = Field(
+      default=None, init=False, exclude=True
+  )
   """The parent agent of this agent.
 
   Note that an agent can ONLY be added as sub-agent once.