Question: Do APT support streaming download for metadata/deb?

Hi,

I have been designing an HTTP APT repository server. My `Release` and `Packages` files are automatically generated when an HTTP GET request is received and are sent via streaming without a `Content-Length` header. Currently, cURL can fetch the files successfully, but APT cannot.

To investigate, I deployed a simple HTTP server that forwards requests to/from <https://deb.debian.org>, while removing the `Content-Length` header. In this case, both cURL and Wget can fetch the content successfully, but APT still fails. It seems that APT may not support streaming downloads.

cURL's output:

```shell
$ curl http://127.0.0.1:8080/dists/frankenstein/Release
Origin: <Origin>
Label: <Label>
Suite: unstable
Codename: frankenstein
Changelogs: https://example.com
Date: Sat, 20 Sep 2025 14:58:08 UTC
Valid-Until: Sat, 27 Sep 2025 14:58:08 UTC
Acquire-By-Hash: no
No-Support-for-Architecture-all: Packages
Architectures: amd64 amd64
Components: core extra
Description: <Desc>
```

APT's output:

```
root@Linux:/# apt update
Ign:1 http://127.0.0.1:8080 frankenstein InRelease
Get:2 http://127.0.0.1:8080 frankenstein Release [340 B]
Ign:3 http://127.0.0.1:8080 frankenstein Release.gpg
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Get:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Get:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Get:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Get:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Err:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
  404  Not Found [IP: 127.0.0.1 8080]
  Undetermined Error [IP: 127.0.0.1 8080]
Fetched 340 B in 8s (42 B/s)
All packages are up to date.
Warning: No Hash entry in Release file /var/lib/apt/lists/partial/127.0.0.1:8080_dists_frankenstein_Release
Warning: Failed to fetch http://127.0.0.1:8080/dists/frankenstein/core/binary-amd64/Packages  Undetermined Error [IP: 127.0.0.1 8080]
Warning: Some index files failed to download. They have been ignored, or old ones used instead.
Notice: Some sources can be modernized. Run 'apt modernize-sources' to do so.
```

Regarding the line `Get:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages`, it seems APT received the data but did not process it correctly.

For comparison, I saved the auto-generated files on a static HTTP server for testing. This time, APT updated successfully:

```
Ign:1 http://127.0.0.1:8080 frankenstein InRelease
Get:2 http://127.0.0.1:8080 frankenstein Release [319 B]
Ign:3 http://127.0.0.1:8080 frankenstein Release.gpg
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Ign:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Get:4 http://127.0.0.1:8080 frankenstein/core amd64 Packages [111 kB]
Ign:5 http://127.0.0.1:8080 frankenstein/core Translation-en
Fetched 111 kB in 0s (3242 kB/s)
14 packages can be upgraded. Run 'apt list --upgradable' to see them.
Warning: No Hash entry in Release file /var/lib/apt/lists/partial/127.0.0.1:8080_dists_frankenstein_Release
Notice: Some sources can be modernized. Run 'apt modernize-sources' to do so.
```

So, does APT not support streaming downloads?

If not, is adding streaming downloads support a good idea?

Best regards,