POST Requests with Streaming Bodies Fail with 500 Error

[i-icc]

When sending POST requests with a request body (e.g., gRPC/Connect requests) through the Container class, the request fails with a 500 error. This occurs because the containerFetch method does not include the duplex: "half" option when forwarding requests with streaming bodies.

Steps to Reproduce

1. Set up a container running a gRPC/Connect server (or any server accepting POST with body)
2. Send a POST request with a JSON body through the Container class:

curl -X POST http://hoge.workers.dev/health \
  -H "Content-Type: application/json" \
  -d '{}'

ex

curl -v -X POST http://hoge.workers.dev/proto.hoge.v1.hogeService/HealthCheck \
  -H "Content-Type: application/json" \
  -d '{}'
Note: Unnecessary use of -X or --request, POST is already inferred.
* Host hoge.workers.dev:80 was resolved.
* IPv6: xxx,xxx
* IPv4: xxx.xxx.xxx.xxx, xxx.xxx.xxx.xxx
*   Trying [xxx]:80...
* Connected to hoge.workers.dev (xxx) port 80
> POST /proto.hoge.v1.hogeService/HealthCheck HTTP/1.1
> Host: hoge.workers.dev
> User-Agent: curl/8.7.1
> Accept: */*
> Content-Type: application/json
> Content-Length: 2
> 
* upload completely sent off: 2 bytes
< HTTP/1.1 500 Internal Server Error
< Date: Wed, 01 Oct 2025 14:13:39 GMT
< Content-Type: text/plain;charset=UTF-8
< Content-Length: 42
< Connection: keep-alive
< Vary: accept-encoding
< Report-To: {"group":"cf-nel","max_age":604800,"endpoints":[{"url":"hoge"}]}
< Nel: {"report_to":"cf-nel","success_fraction":0.0,"max_age":604800}
< Server: cloudflare
< CF-RAY: 987c8fd6bf0eafd3-NRT
< alt-svc: h3=":443"; ma=86400
< 
* Connection #0 to host hoge.workers.dev left intact
Container suddenly disconnected, try again%  

The container log is normal, but the worker is not receiving it correctly.

Suspicious code

In src/lib/container.ts at line 707:

const res = await tcpPort.fetch(containerUrl, request);

When a Request object with a body is passed to fetch(), the body property is a ReadableStream. According to the Fetch API specification, when the request body is a stream, the duplex property must be explicitly set to "half".

(English is not my first language so I apologize if I didn't capture the nuances.)

[th0m]

Hi @i-icc thanks a lot for the detailed report, we are investigating and will comment here when it is fixed.

[i-icc]

Hi @th0m thank you for response.
Please let me know if any code sample and request data is missing.

[th0m]

@i-icc the release with the fix is rolling out and should complete within a few hours

[i-icc]

Wow, That's a really quick fix. Thank you!

[th0m]

@i-icc can you please retry and confirm? Thank you

[i-icc]

I've confirmed it is fixed!
thank you!

[i-icc]

It was fixed, thank you!

[kozoy]

Hi, I'm experiencing a similar issue with PATCH requests containing streaming
bodies.

Environment

• @cloudflare/containers: v0.0.30 (latest)
• Wrangler: 4.49.1
• Date: 2025-11-21

Error

Error: internal error; reference = e5634i0hnfo8psp6kpb2vaqv
at async Object.fetch (index.js:929:22)

Reference ID: e5634i0hnfo8psp6kpb2vaqv

Use Case

Running a Zot OCI registry container. When pushing images via podman push:

• POST /v2/<name>/blobs/uploads/ (Content-Length: 0) → 202 success
• PATCH /v2/<name>/blobs/uploads/<uuid> with blob data (~4MB) → 500 Internal
  Server Error

Worker Code

Following the official example pattern:

export default {
  async fetch(request, env) {
    const container = getContainer(env.ZOT, "zot-registry-singleton");
    const response = await container.fetch(request);
    return response;
  },
};

Observations

• Container logs show the PATCH request never reaches the container - Zot returns 202
  when it does receive requests
• Error occurs in Worker SDK layer at container.fetch()
• The issue appears specific to requests with streaming body data (PATCH with
  application/octet-stream, Content-Length: 3930425)

Since this issue was marked as resolved in October 2025, could this be a regression or a
different code path for PATCH requests with large streaming bodies?