request.raw_post ( env['rack.input'] ) is nil on pitchfork( with rack3)

[os0x]

Describe the bug

gems:

• pitchfork 0.18.1
• rack 3.2.3
• rails 8.0.3

request.raw_post is always nil, and request.env["rack.input"].read is blank.

How to reproduce

Here is my sample app: https://github.com/os0x/rack3_pitchfork_sample

https://github.com/os0x/rack3_pitchfork_sample/blob/main/app/controllers/hello_controller.rb

def index
  puts "params: #{params.inspect}"
  puts "raw_post:", request.raw_post
  puts 'request.env["rack.input"]:', request.env["rack.input"].read
  render json: { message: "Hello, Pitchfork!" }
end

on puma

$ bundle exec rails s (using puma)
and
$ curl -X POST http://localhost:3000/hello -d '{"message": "hello" }'

Started POST "/hello" for ::1 at 2025-10-25 15:17:42 +0900
  ActiveRecord::SchemaMigration Load (0.4ms)  SELECT "schema_migrations"."version" FROM "schema_migrations" ORDER BY "schema_migrations"."version" ASC /*application='Rack3PitchforkSample'*/
Processing by HelloController#index as */*
  Parameters: {"{\"message\": \"hello\" }" => nil}
params: #<ActionController::Parameters {"{\"message\": \"hello\" }" => nil, "controller" => "hello", "action" => "index"} permitted: false>
raw_post:
{"message": "hello" }
request.env["rack.input"]:
{"message": "hello" }
Completed 200 OK in 20ms (Views: 0.1ms | ActiveRecord: 0.0ms (0 queries, 0 cached) | GC: 0.0ms)

raw_post is correct.

on pitchfork

$ WORKER_NUM=1 PORT=3000 bundle exec pitchfork -c pitchfork.conf.rb (use pitchfork)
I send the same request.

I, [2025-10-25T15:18:01.118451 #9156]  INFO -- [Pitchfork]: listening on addr=0.0.0.0:3000 fd=10
I, [2025-10-25T15:18:01.145019 #9156]  INFO -- [Pitchfork]: monitor pid=9156 ready
I, [2025-10-25T15:18:01.145074 #9156]  INFO -- [Pitchfork]: monitor process ready
I, [2025-10-25T15:18:01.145155 #9156]  INFO -- [Pitchfork]: worker=0 gen=0 spawning...
I, [2025-10-25T15:18:01.150503 #9251]  INFO -- [Pitchfork]: worker=0 gen=0 pid=9251 spawned
I, [2025-10-25T15:18:01.150876 #9156]  INFO -- [Pitchfork]: worker=0 gen=0 pid=9251 registered
I, [2025-10-25T15:18:01.150984 #9251]  INFO -- [Pitchfork]: worker=0 gen=0 pid=9251 ready
params: #<ActionController::Parameters {"{\"message\": \"hello\" }" => nil, "controller" => "hello", "action" => "index"} permitted: false>
raw_post:

request.env["rack.input"]:

raw_post is nil.

rack 2 & pitchfork

I, [2025-10-26T14:50:03.077087 #18412]  INFO -- [Pitchfork]: listening on addr=0.0.0.0:3000 fd=10
I, [2025-10-26T14:50:03.109811 #18412]  INFO -- [Pitchfork]: monitor pid=18412 ready
I, [2025-10-26T14:50:03.109865 #18412]  INFO -- [Pitchfork]: monitor process ready
I, [2025-10-26T14:50:03.109948 #18412]  INFO -- [Pitchfork]: worker=0 gen=0 spawning...
I, [2025-10-26T14:50:03.118079 #18628]  INFO -- [Pitchfork]: worker=0 gen=0 pid=18628 spawned
I, [2025-10-26T14:50:03.118425 #18628]  INFO -- [Pitchfork]: worker=0 gen=0 pid=18628 ready
I, [2025-10-26T14:50:03.118533 #18412]  INFO -- [Pitchfork]: worker=0 gen=0 pid=18628 registered
params: #<ActionController::Parameters {"{\"message\": \"hello\" }" => nil, "controller" => "hello", "action" => "index"} permitted: false>
raw_post:
{"message": "hello" }
request.env["rack.input"]:
{"message": "hello" }

raw_post is correct.

How do you advise I can do this? Thanks.