tirkarthi opened a new issue, #60165:
URL: https://github.com/apache/airflow/issues/60165
### Apache Airflow version
3.1.5
### If "Other Airflow 3 version" selected, which one?
_No response_
### What happened?
We have a service that takes requests of certain url paths of Airflow API
and then uses http client to hit Airflow API service and returns the response
with headers back to the load balancer nginx. After upgrade from Airflow 3.1.2
to 3.1.5 we noticed the service is able to hit the Airflow API but there is a
change in the header and the response type where in Airflow 3.1.2 it was not
chunked and in Airflow 3.1.5 it was chunked. The chunked header is returned
back to nginx which also tries to add it's own header which results in error
'upstream sent duplicate header line: "Transfer-Encoding: chunked"' . This
results in nginx sending 504 response.
Upon debugging it seems that JWTRefreshMiddleware was added in #55506 with
that the middleware order becomes JWTRefreshMiddleware -> GZipMiddleware. The
requests go through middleware from top to bottom and the responses go through
bottom to top. Looks like JWTRefreshMiddleware is added before GZipMiddleware
resulting in chunked vs non-chunked response behavior change.` Upon adjusting
the order in `airflow-core/src/airflow/api_fastapi/core_api/app.py` we were
able to restore the previous behavior. As per my understanding `GZipMiddleware`
should process response to compress it after `JWTRefreshMiddleware` in terms of
the response cycle. There was no change in frontend and other parts but we
thought to file an issue anyway.
```python
app.add_middleware(GZipMiddleware, minimum_size=100, compresslevel=5)
app.add_middleware(JWTRefreshMiddleware)
```
```python
import httpx
dict(httpx.get("http://localhost:8000/api/v2/monitor/health";).headers)
{'date': 'Tue, 06 Jan 2026 13:46:29 GMT', 'server': 'uvicorn',
'content-length': '170',
'content-type': 'application/json', 'content-encoding': 'gzip', 'vary':
'Accept-Encoding'}
```
Change order to have GZipMiddleware at last.
```python
app.add_middleware(JWTRefreshMiddleware)
app.add_middleware(GZipMiddleware, minimum_size=100, compresslevel=5)
```
```python
import httpx
dict(httpx.get("http://localhost:8000/api/v2/monitor/health";).headers)
{'date': 'Tue, 06 Jan 2026 14:31:51 GMT', 'server': 'uvicorn',
'content-type': 'application/json',
'content-encoding': 'gzip', 'vary': 'Accept-Encoding', 'transfer-encoding':
'chunked'}
```
### What you think should happen instead?
_No response_
### How to reproduce
Change order and compress size as above in
`airflow-core/src/airflow/api_fastapi/core_api/app.py` and use httpx to analyse
the change in headers.
### Operating System
Ubuntu 20.04
### Versions of Apache Airflow Providers
_No response_
### Deployment
Virtualenv installation
### Deployment details
_No response_
### Anything else?
_No response_
### 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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