gudata opened a new issue, #54836:
URL: https://github.com/apache/airflow/issues/54836
### Apache Airflow version
3.0.5
### If "Other Airflow 2 version" selected, which one?
_No response_
### What happened?
I have upgraded airflow from 3.0.4 to 3.0.5 and the dags are gone with:
```
"Objects of type {type(obj)} are not supported"
Traceback (most recent call last):
File
"/home/airflow/.local/lib/python3.12/site-packages/airflow/sdk/execution_time/comms.py",
line 145, in as_bytes
self.req_encoder.encode_into(self, buffer, 4)
File
"/home/airflow/.local/lib/python3.12/site-packages/airflow/sdk/execution_time/comms.py",
line 122, in _msgpack_enc_hook
raise NotImplementedError(f"Objects of type {type(obj)} are not
supported")
NotImplementedError: Objects of type <class
'pydantic_core._pydantic_core.SerializationIterator'> are not supported
```
The airflow dag-processor said more:
```
{"timestamp":"2025-08-22T16:05:49.980648","level":"error","event":"Failed to
import:
/opt/airflow/dags/services/generate_dags_dag.py","logger":"airflow.models.dagbag.DagBag","error_detail":[{"exc_type":"NotImplementedError","exc_value":"Objects
of type <class 'pydantic_core._pydantic_core.SerializationIterator'> are not
supported","exc_notes":[],"syntax_error":null,"is_cause":false,"frames":[{"filename":"/home/airflow/.local/lib/python3.12/site-packages/airflow/models/dagbag.py","lineno":394,"name":"parse"},{"filename":"<frozen
importlib._bootstrap_external>","lineno":999,"name":"exec_module"},{"filename":"<frozen
importlib._bootstrap>","lineno":488,"name":"_call_with_frames_removed"},{"filename":"/opt/airflow/dags/services/generate_dags_dag.py","lineno":57,"name":"<module>"},{"filename":"/opt/airflow/dags/include/my_company/insights/dag_particles.py","lineno":287,"name":"generate_dags_task"},{"filename":"/opt/airflow/dags/include/my_company/insights/client_config/base.py","lineno
":446,"name":"generate_dags_environment_variables"},{"filename":"/opt/airflow/dags/include/my_company/insights/client_config/base.py","lineno":215,"name":"database_migration_snowflake_connection"},{"filename":"/home/airflow/.local/lib/python3.12/site-packages/airflow/sdk/definitions/connection.py","lineno":162,"name":"extra_dejson"},{"filename":"/home/airflow/.local/lib/python3.12/site-packages/airflow/sdk/execution_time/secrets_masker.py","lineno":130,"name":"mask_secret"},{"filename":"/home/airflow/.local/lib/python3.12/site-packages/airflow/sdk/execution_time/comms.py","lineno":187,"name":"send"},{"filename":"/home/airflow/.local/lib/python3.12/site-packages/airflow/sdk/execution_time/comms.py","lineno":145,"name":"as_bytes"},{"filename":"/home/airflow/.local/lib/python3.12/site-packages/airflow/sdk/execution_time/comms.py","lineno":122,"name":"_msgpack_enc_hook"}],"is_group":false,"exceptions":[]}]}
```
### What you think should happen instead?
Dags running on 3.0.4 should work on 3.0.5
### How to reproduce
Here is the problematic line
```
role=self.airflow_database_migration_snowflake_connection.extra_dejson[
"role" <<<<< line 216
]
```
### Operating System
PRETTY_NAME="Amazon Linux 2023.7.20250623"
### Versions of Apache Airflow Providers
the one which came withe airflow in docker
### Deployment
Docker-Compose
### Deployment details
_No response_
### Anything else?
Chat GPT explain the error
```
Why this error appeared after those fixes
Before, Airflow was passing around “simple” Python types when masking
secrets (strings, dicts).
After #54574 / #54612, Airflow started running Pydantic
validation/serialization when building masked connection objects.
That introduced SerializationIterator objects into the data path.
But the comms layer (msgpack encoding in comms.py) doesn’t know how to
serialize that object type → hence:
NotImplementedError: Objects of type <class
'pydantic_core._pydantic_core.SerializationIterator'> are not supported
So the regression is that secrets masking now returns Pydantic internals,
which comms can’t encode.
```
### Are you willing to submit PR?
- [ ] Yes I am willing to submit a PR!
### Code of Conduct
- [x] I agree to follow this project's [Code of
Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
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