`fly console` does not allocate a PTY — no prompt, buffered output

[ursm]

Describe the bug

fly console does not allocate a PTY. The session has no prompt, no input echo, and stdout is buffered — output only appears after pressing Enter multiple times. This happens with both the default console_command and explicitly passing -C /bin/bash.

fly ssh console (with implicit --pty) and fly machine run --shell on the same app both work correctly.

This is not specific to the current version; it has been present across multiple recent releases.

• Operating system: Linux (Gentoo, Wayland), TERM=xterm-256color
• fly version: flyctl v0.4.21

app             = 'logizo-backend-staging'
primary_region  = 'nrt'
console_command = 'bin/rails console'
swap_size_mb    = 256

[env]
HTTP_PORT = '8080'
RAILS_ENV = 'staging'
TZ        = 'Asia/Tokyo'

[processes]
web    = ''
worker = 'bin/jobs'

[http_service]
processes     = ['web']
internal_port = 8080
force_https   = true

[[http_service.checks]]
processes     = ['web']
grace_period = '20s'
interval     = '10s'
timeout      = '1s'
path         = '/up'

[[vm]]
processes = ['web']
cpu_kind  = 'shared'
cpus      = 1
memory    = '512mb'

[[vm]]
processes = ['worker']
cpu_kind  = 'shared'
cpus      = 1
memory    = '512mb'

Command output:

fly console with bash — no prompt, no echo, buffered output:

$ fly console --vm-memory 512 -c fly.staging.toml -C /bin/bash
Created an ephemeral machine d890155a000de8 to run the console.
Connecting to fdaa:x:xxxx:xxx:xxx:xxxx:xxxx:2... complete
ls
Gemfile
Gemfile.lock
Procfile.dev
README.md
Rakefile
app
bin
config
config.ru
db
docker-compose.yml
fonts
lib
log
public
schema
script
storage
tmp
vendor

Note: ls above was typed blindly with no prompt or echo. The output appeared only after pressing Enter several times.

fly ssh console on the same app — works as expected:

$ fly ssh console -c fly.staging.toml
Connecting to fdaa:x:xxxx:xxx:xxx:xxxx:xxxx:2... complete
root@d89954db5e1238:/rails# ls
Gemfile       Procfile.dev  Rakefile  bin     config.ru  docker-compose.yml  lib  public  schema   tmp
Gemfile.lock  README.md     app       config  db         fonts               log  script  storage  vendor

fly console --debug produces no additional output related to this issue.