This guide covers the breaking changes introduced in TRL v1 and how to update your code. Most structural changes (trainers moved to experimental, removed model classes, etc.) already shipped in v0.29 — if you're already on v0.29, this migration is minimal.
| Config | Parameter | v0 default | v1 default | Action needed |
|---|---|---|---|---|
GRPOConfig |
vllm_mode |
"server" |
"colocate" |
If you use use_vllm=True without specifying vllm_mode, vLLM will now run in the same process instead of connecting to a separate server. Set vllm_mode="server" explicitly if you rely on server mode. |
RLOOConfig |
vllm_mode |
"server" |
"colocate" |
Same as above. |
| Config | Parameter | v0 value | v1 value | Action needed |
|---|---|---|---|---|
SFTConfig |
packing |
"bfd-requeue" |
"bfd_split" |
Replace packing="bfd-requeue" with packing="bfd_split". The old value will still be accepted for a few versions but will be removed in a future release. |
Depending on which version you're migrating from, refer to the release notes for v0.29 and earlier for version-specific changes.