Content type not set on request

[tomekowal]

Hi!

I've found an incosistency between 1.25.0 and 3.0.1 that is not covered in the migration guide.
I have the following code:

method = :post
url = "http://localhost:5080/post"
headers = []
body = String.duplicate("response long", 1000)
opts = [with_body: true, max_body: 100]

:hackney.request(method, url, headers, body, opts)

hitting httparrot

In 1.25.0 it fills default content-type to be "application/octet-stream"

:ok, 200,
 [
   {"content-length", "13223"},
   {"content-type", "application/json"},
   {"date", "Sun, 01 Feb 2026 15:03:37 GMT"},
   {"server", "Cowboy"}
 ],
 "{\"args\":{},\"headers\":{\"content-length\":\"13000\",\"content-type\":\"application/octet-stream\",\"host\":\"localhost:5080\",\"user-agent\":\"hackney/1.24.1\"},\"url\":\"http://localhost:5080/post\",\"origin\":\"\",\"form\":{},\"data\":\"response longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longresponse longrespon"}

In 3.0.1 I get:

{:ok, 415,
 [
   {"content-length", "0"},
   {"date", "Sun, 01 Feb 2026 15:11:42 GMT"},
   {"server", "Cowboy"}
 ], ""}

mainly because the default {"content-type", "application/octet-stream"}. Is that an intentional change that should be part of the migration guide or is it accidental and will be fixed in future versions?

[benoitc]

Thank you for reporting this! Fixed in v3.0.2 - hackney now adds default Content-Type: application/octet-stream when sending a body without explicit Content-Type header, restoring 1.x behavior.