The plugin used to unconditionally monkey-patch
VLLMClient.init_communicator to a no-op AND silently no-op
sync_weights when vllm_lora_sync was off. Combined, this turned the
trainer into a functional no-op whenever (a) the user ran NeMo Gym
+ LoRA without remembering to set vllm_lora_sync=true or (b) the
user ran NeMo Gym + full fine-tune (which had no working sync path
under the old code).
Replace both patches with:
1. A probe of the configured vLLM server's /openapi.json at
pre_model_load. Three transports are recognized:
- NCCL (/init_communicator/ + /update_named_param/) — TRL serve
and axolotl vllm-serve both expose this
- LoRA filesystem (/v1/load_lora_adapter or /set_lora_adapter/)
- HTTP base64 full-weight (/http_update_weights/) — axolotl
vllm-serve only
2. A pure-logic ``select_weight_sync_transport`` that picks the
right one for (server caps × adapter type).
3. ``init_communicator`` is only patched out when the server has no
NCCL routes; against TRL/axolotl serve modules it stays live so
full-finetune NCCL sync works.
4. ``post_trainer_create`` uses the selection table to install LoRA
filesystem sync OR leave the standard NCCL flow alone OR raise
NotImplementedError (HTTP — pending) OR raise a precise diagnosis
when no transport is viable. No more silent no-op trainers.
69f165b39b