From f47ed4f1f15f0df954801b7f77ff947af3faa8cf Mon Sep 17 00:00:00 2001
From: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Date: Sun, 1 Jun 2025 06:54:48 +0000
Subject: [PATCH] Fix Flow persistence with nested Pydantic models (issue
 #2929)
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- Use CrewJSONEncoder in SQLiteFlowPersistence.save_state() to properly serialize nested Pydantic models
- Add comprehensive test for nested Pydantic model persistence
- Resolves RuntimeError: Object of type CustomPydanticModel is not JSON serializable

Co-Authored-By: João <joao@crewai.com>
---
 src/crewai/flow/persistence/sqlite.py |  3 +-
 tests/test_flow_persistence.py        | 44 +++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/src/crewai/flow/persistence/sqlite.py b/src/crewai/flow/persistence/sqlite.py
index 8b2a0f3f2..8f3d0b80f 100644
--- a/src/crewai/flow/persistence/sqlite.py
+++ b/src/crewai/flow/persistence/sqlite.py
@@ -11,6 +11,7 @@ from typing import Any, Dict, Optional, Union
 from pydantic import BaseModel
 
 from crewai.flow.persistence.base import FlowPersistence
+from crewai.utilities.crew_json_encoder import CrewJSONEncoder
 
 
 class SQLiteFlowPersistence(FlowPersistence):
@@ -103,7 +104,7 @@ class SQLiteFlowPersistence(FlowPersistence):
                     flow_uuid,
                     method_name,
                     datetime.now(timezone.utc).isoformat(),
-                    json.dumps(state_dict),
+                    json.dumps(state_dict, cls=CrewJSONEncoder),
                 ),
             )
 
diff --git a/tests/test_flow_persistence.py b/tests/test_flow_persistence.py
index cf3bb22f0..664c8b78b 100644
--- a/tests/test_flow_persistence.py
+++ b/tests/test_flow_persistence.py
@@ -208,3 +208,47 @@ def test_persist_decorator_verbose_logging(tmp_path, caplog):
     flow = VerboseFlow(persistence=persistence)
     flow.kickoff()
     assert "Saving flow state" in caplog.text
+
+
+def test_nested_pydantic_model_persistence(tmp_path):
+    """Test persistence with nested Pydantic models (issue #2929)."""
+    from pydantic import Field
+    
+    db_path = os.path.join(tmp_path, "test_flows.db")
+    persistence = SQLiteFlowPersistence(db_path)
+
+    class CustomObject(BaseModel):
+        field_x: float | None = Field(description="foo bar", default=None)
+
+    class CustomState(FlowState):
+        custom_field: CustomObject | None = None
+
+    class NestedPydanticFlow(Flow[CustomState]):
+        initial_state = CustomState
+
+        @start()
+        @persist(persistence, verbose=True)
+        def set_nested_object(self):
+            self.state.custom_field = CustomObject(field_x=42.0)
+
+    flow = NestedPydanticFlow(persistence=persistence)
+    flow.kickoff()
+
+    saved_state = persistence.load_state(flow.state.id)
+    assert saved_state is not None
+    assert saved_state["custom_field"] is not None
+    assert saved_state["custom_field"]["field_x"] == 42.0
+
+    class NullNestedFlow(Flow[CustomState]):
+        initial_state = CustomState
+
+        @start()
+        @persist(persistence)
+        def set_null_nested(self):
+            self.state.custom_field = None
+
+    flow2 = NullNestedFlow(persistence=persistence)
+    flow2.kickoff()
+    saved_state2 = persistence.load_state(flow2.state.id)
+    assert saved_state2 is not None
+    assert saved_state2["custom_field"] is None