Enabled caching and RateLimitMiddleware duplicate all `Ratelimt-*` headers in response

[mikhail-tokarev]

Description

with litestar.middleware.rate_limit.RateLimitMiddleware added to app middleware and cache=True enabled on route handler you can observe duplicates for all Ratelimit-* response headers like this:

URL to code causing the issue

No response

MCVE

from litestar import Litestar, MediaType, get
from litestar.middleware.rate_limit import RateLimitConfig

rate_limit_config = RateLimitConfig(rate_limit=("minute", 1), exclude=["/schema"])

@get("/", cache=True, media_type=MediaType.TEXT, sync_to_thread=False)
def handler() -> str:
    return "ok"

app = Litestar(route_handlers=[handler], middleware=[rate_limit_config.middleware])

Steps to reproduce

No response

Screenshots

No response

Logs

No response

Litestar Version

2.9.1

Platform

• [X] Linux
• [X] Mac
• [ ] Windows
• [ ] Other (Please specify in the description above)

---

[!NOTE]
While we are open for sponsoring on GitHub Sponsors and OpenCollective, we also utilize Polar.sh to engage in pledge-based sponsorship.

Check out all issues funded or available for funding on our Polar.sh dashboard

• If you would like to see an issue prioritized, make a pledge towards it!
• We receive the pledge once the issue is completed & verified
• This, along with engagement in the community, helps us know which features are a priority to our users.