`stale-while-revalidate` not triggering background revalidation in either `bypass_request` or `strict` mode

[Seanw265]

I'm having trouble getting Souin to honor stale-while-revalidate as expected.

Setup

{
  cache {
    ttl 100s
    stale 3h
    default_cache_control public, s-maxage=100
    mode bypass_request
  }
}

:80 {
  cache
  reverse_proxy test-server:8080
}

Origin response:

Cache-Control: public, s-maxage=10, stale-while-revalidate=60

All test requests are made without any Cache-Control request headers.

Cache modes and expectations

My understanding is:

• strict follows HTTP caching RFCs literally.
• bypass_request ignores Cache-Control request headers but still honors Cache-Control response headers.

Since I am not sending any Cache-Control request headers, I expect both modes to behave the same.

Expected Behavior

• First request: MISS
• Second request (within s-maxage=10): HIT
• After s-maxage but within SWR: serve stale and revalidate in the background
• After SWR expires: revalidate or refetch before serving

Actual Behavior

bypass_request

• First request: MISS
• Second request: HIT
• After s-maxage: stale is served, but revalidation never occurs
• Result: stale content persists indefinitely

strict

• First request: MISS
• Second request: HIT
• After s-maxage but within SWR: MISS and synchronous revalidation
• Result: stale content is never served during SWR

Summary

• bypass_request serves stale but never revalidates.
• strict never serves stale once s-maxage expires.
• In both cases, stale-while-revalidate appears to have no effect.
• The difference between the modes is unexpected, because no Cache-Control request headers are being sent.

Please let me know if this is a configuration issue or if I am misunderstanding something. I'm new to Souin so it's certainly possible there's something I've missed.

[darkweak]

Hey @Seanw265 and @sveniu you can try the patch 5dfcbddedc3ae56c5422730ab6d1919435078718 please?

xcaddy build --with github.com/darkweak/souin/plugins/caddy@5dfcbddedc3ae56c5422730ab6d1919435078718 --with github.com/darkweak/souin@5dfcbddedc3ae56c5422730ab6d1919435078718