HeadObject returns ContentLength: null for objects on Cloudflare R2

[kralmichal]

Hit this in production today and tracked it down. Posting in case anyone else runs into it.

Setup: Cloudflare R2 bucket via the S3-compatible endpoint, accessed through async-aws/s3 (3.2.0) + league/flysystem-async-aws-s3 (3.31.0). PutObject works fine. HeadObject returns 200 with the
right ETag and Content-Type, but getContentLength() returns null, which makes flysystem throw UnableToRetrieveMetadata::fileSize.

It's not async-aws's fault — Cloudflare's edge proxy is the problem.

Reproduced by dumping the raw response headers async-aws receives:

HTTP/1.1 200 OK                                           
Date: Mon, 27 Apr 2026 21:19:33 GMT
Content-Type: image/svg+xml
Last-Modified: Mon, 27 Apr 2026 21:10:20 GMT                                                                                                                                                             
ETag: W/"32338883f6b6423933d02f75f6dd2cdc"
Content-Encoding: gzip                                                                                                                                                                                   
Server: cloudflare                                        
CF-RAY: 9f30ddbbea10d3b4-FRA                                                                                                                                                                             

Content-Encoding: gzip is set, no Content-Length. Cloudflare's proxy gzips compressible HEAD responses, and per HTTP semantics Content-Length then refers to the compressed body — but HEAD has no
body, so the header gets dropped entirely. Tools that send Accept-Encoding: identity (curl, mc) don't trigger this; tools that accept gzip (most HTTP clients including symfony/http-client by
default) do.

Workaround that fixes it for me — pass a custom HTTP client that asks for identity encoding:

app.async_aws.http_client:
    class: Symfony\Contracts\HttpClient\HttpClientInterface                                                                                                                                              
    factory: ['Symfony\Component\HttpClient\HttpClient', 'create']
    arguments:                                                                                                                                                                                           
      - headers:                                          
          Accept-Encoding: identity                                                                                                                                                                      
                                                          
AsyncAws\S3\S3Client:
    arguments:
      - endpoint: '%env(AWS_ENDPOINT)%'
        ...                                                                                                                                                                                              
      - null
      - '@app.async_aws.http_client'                                                                                                                                                                     

After this, getContentLength() returns the correct size.

Opening this mainly so it's findable for the next person who hits it. Happy to send a PR if you'd want Accept-Encoding: identity set by default on HEAD requests, but that may have side effects on
AWS proper, so I'll leave the call to the maintainers.

[stof]

Given that the S3 API relies on the Content-Length header to provide the info, I would consider this a bug in the R2 implementation claiming to be S3-compatible. They should probably disable the gzip compression of their edge proxy on those R2 endpoints to actually behave like S3.
I suggest reporting this to R2 (it probably affects similar usages done with official AWS SDKs as well, not just async-aws)

[kralmichal]

@stof I will report it. Thanks for reply.