Coder Workspace File Transfer

Move large files to (or from) a Coder Cloud Development Environment reliably. The naive path — rsync -e "coder ssh" — is broken on macOS. Use a coder config-ssh host alias with a protocol-clean, PTY-free SSH channel instead.

When to use

• Uploading a directory, dataset, build artifact, or binary to a Coder workspace.
• rsync -e "coder ssh" fails, desyncs mid-transfer, or hangs.
• A copy over coder ssh corrupts or never completes.
• You need a resumable transfer over a flaky dev tunnel.

The one-liner

coder config-ssh                                          # one-time per machine
rsync -avP -e "ssh -T" /local/dir <workspace>.coder:/remote/target/dir/

Instructions

1. Generate SSH host aliases (one-time per machine/workspace):

   coder config-ssh

   This adds host entries to ~/.ssh/config. Note the alias for your workspace from the output — typically <workspace>.coder (e.g. workspace Loom → host Loom.coder).
2. Confirm you have GNU rsync (macOS ships the incompatible openrsync):

   rsync --version

   If it says openrsync, install GNU rsync:

   brew install rsync

3. Ensure the remote target directory exists:

   coder ssh <workspace> -- mkdir -p /remote/target/dir

4. Transfer — preferred (resumable):

   rsync -avP -e "ssh -T" /local/dir <workspace>.coder:/remote/target/dir/

   • -a archive, -v verbose, -P = --partial --progress → resumable.
   • -e "ssh -T" disables PTY allocation — the essential fix.
5. Transfer — fallback (no resume):

   scp -r /local/dir <workspace>.coder:/remote/target/dir/

6. Download (reverse direction) — swap the arguments:

   rsync -avP -e "ssh -T" <workspace>.coder:/remote/dir ./local/target/

What NOT to do

• ❌ rsync -e "coder ssh" src host:dst — macOS openrsync desyncs against the remote GNU rsync; even with GNU rsync, coder ssh's PTY corrupts the byte stream.
• ❌ Omitting -e "ssh -T" — the default TTY allocation breaks rsync/tar pipelines.
• ❌ Trusting the macOS built-in rsync — always verify rsync --version reports GNU.

Why this works

coder config-ssh turns the Coder tunnel into a standard SSH host. Any TCP-clean SSH tool (rsync, scp, sftp) then works directly, instead of being wrapped by coder ssh, which forces a PTY. Removing the PTY (ssh -T) and using GNU rsync's protocol gives a clean binary channel that survives large, resumable transfers.

Reference

Full write-up with the failure matrix and a concrete Loom example: docs/coder-large-file-upload.md.