[Bug]: MalformedChunkCodingException since Update to 1.21.4/2.0.3

Module

Core

Testcontainers version

1.21.4, 2.0.3

Using the latest Testcontainers version?

Yes

Host OS

Windows

Host Arch

X64

Docker version

Client:                                                                      
 Version:           29.0.2-rd                                                
 API version:       1.51 (downgraded from 1.52)                              
 Go version:        go1.25.4                                                 
 Git commit:        5a2d7eb                                                  
 Built:             Tue Nov 18 23:34:16 2025                                 
 OS/Arch:           windows/amd64                                            
 Context:           default                                                  
                                                                             
Server:                                                                      
 Engine:                                                                     
  Version:          28.3.3                                                   
  API version:      1.51 (minimum version 1.24)                              
  Go version:       go1.24.8                                                 
  Git commit:       bea959c7b793b32a893820b97c4eadc7c87fabb0                 
  Built:            Sun Oct 12 08:01:14 2025                                 
  OS/Arch:          linux/amd64                                              
  Experimental:     false                                                    
 containerd:                                                                 
  Version:          v2.1.5                                                   
  GitCommit:        fcd43222d6b07379a4be9786bda52438f0dd16a1                 
 runc:                                                                       
  Version:          1.3.3                                                    
  GitCommit:        d842d7719497cc3b774fd71620278ac9e17710e0                 
 docker-init:                                                                
  Version:          0.19.0                                                   
  GitCommit:

What happened?

Hi,

I described the problem in a comment in #11254 but given the nature of it, I think it warrants its own issue ticket.

Since updating to Testcontainers 1.21.4/2.0.3 we are occasionally encountering an exception:

NpipeSocketClientProviderStrategy: failed with exception RuntimeException (com.github.dockerjava.zerodep.shaded.org.apache.hc.core5.http.MalformedChunkCodingException: Bad chunk header: ). Root cause MalformedChunkCodingException (Bad chunk header: )

I can reproduce it with something simple as the following code. For some reason it becomes more probable when running in debug mode.

try ( final PostgreSQLContainer<?> container = new PostgreSQLContainer<>( "postgres:14" ) ) {
  container.start( );
}

I use a custom policy to make sure that the image is always pulled.

public final class PullAlwaysPolicy implements ImagePullPolicy {

	@Override
	public boolean shouldPull( final DockerImageName imageName ) {
		return true;
	}

} 

Thank you and best regards

Nils

Relevant log output

Feb. 02, 2026 10:17:54 AM org.testcontainers.images.PullPolicy defaultPolicy
INFORMATION: Found configured Image Pull Policy: class com.example.demo.PullAlwaysPolicy
Feb. 02, 2026 10:17:54 AM org.testcontainers.images.PullPolicy defaultPolicy
INFORMATION: Image pull policy will be performed by: com.example.demo.PullAlwaysPolicy@5d76b067
Feb. 02, 2026 10:17:54 AM org.testcontainers.utility.ImageNameSubstitutor instance
INFORMATION: Image name substitution will be performed by: DefaultImageNameSubstitutor (composite of 'ConfigurationFileImageNameSubstitutor' and 'PrefixingImageNameSubstitutor')
Feb. 02, 2026 10:17:54 AM org.testcontainers.DockerClientFactory getOrInitializeStrategy
INFORMATION: Testcontainers version: 2.0.3
Feb. 02, 2026 10:17:54 AM org.testcontainers.dockerclient.DockerClientProviderStrategy lambda$loadConfiguredStrategy$9
INFORMATION: Loaded org.testcontainers.dockerclient.NpipeSocketClientProviderStrategy from ~/.testcontainers.properties, will try it first
Feb. 02, 2026 10:17:55 AM org.testcontainers.dockerclient.DockerMachineClientProviderStrategy isApplicable
INFORMATION: docker-machine executable was not found on PATH ([REDACTED])
Feb. 02, 2026 10:17:55 AM org.testcontainers.dockerclient.DockerClientProviderStrategy lambda$getFirstValidStrategy$7
SCHWERWIEGEND: Could not find a valid Docker environment. Please check configuration. Attempted configurations were:
	NpipeSocketClientProviderStrategy: failed with exception RuntimeException (com.github.dockerjava.zerodep.shaded.org.apache.hc.core5.http.MalformedChunkCodingException: Bad chunk header: ). Root cause MalformedChunkCodingException (Bad chunk header: )As no valid configuration was found, execution cannot continue.
See https://java.testcontainers.org/on_failure.html for more details.
Exception in thread "main" java.lang.IllegalStateException: Could not find a valid Docker environment. Please see logs and check configuration
	at org.testcontainers.dockerclient.DockerClientProviderStrategy.lambda$getFirstValidStrategy$7(DockerClientProviderStrategy.java:274)
	at java.base/java.util.Optional.orElseThrow(Optional.java:403)
	at org.testcontainers.dockerclient.DockerClientProviderStrategy.getFirstValidStrategy(DockerClientProviderStrategy.java:265)
	at org.testcontainers.DockerClientFactory.getOrInitializeStrategy(DockerClientFactory.java:154)
	at org.testcontainers.DockerClientFactory.client(DockerClientFactory.java:196)
	at org.testcontainers.DockerClientFactory$1.getDockerClient(DockerClientFactory.java:108)
	at com.github.dockerjava.api.DockerClientDelegate.authConfig(DockerClientDelegate.java:109)
	at org.testcontainers.containers.GenericContainer.start(GenericContainer.java:316)
	at com.example.demo.Main.main(Main.java:9)

Additional Information

No response

Start by reproducing the failure with PostgreSQLContainer, the PullAlwaysPolicy, and the reported Windows Docker setup. Read DockerClientProviderStrategy and NpipeSocketClientProviderStrategy around the failing environment check and inspect the MalformedChunkCodingException path. Done means the reported setup can start the container without the malformed chunk error.