unslothai · danielhanchen · Jul 8, 2026 · Jul 8, 2026 · Jul 8, 2026 · Jul 8, 2026
@@ -339,12 +339,18 @@ jobs:
         env:
           UNSLOTH_IS_PRESENT: '1'
           UNSLOTH_COMPILE_DISABLE: '1'
+          # Disable dynamo/inductor at the process level, before conftest.py's early
+          # `import unsloth`, so the GRPO hot path never compiles on the GPU-less runner
+          # (defense in depth; the CPU fake-train also flips this at runtime).
+          TORCHDYNAMO_DISABLE: '1'
+          TORCH_COMPILE_DISABLE: '1'
           PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION: python
         run: |
           cd unsloth
           python -c "import trl; print('Resolved TRL', trl.__version__)"
           PYTHONPATH=. python -m pytest \
             tests/version_compat/test_trl_grpo_fake_run.py \
+            tests/version_compat/test_trl_fake_train_cpu.py \
             -v --tb=short
       # `main` is scheduled/dispatch-only so PR jobs stay fast and a bleeding-edge
       # TRL break does not red every PR. github.event_name is valid in a step if.
@@ -353,13 +359,16 @@ jobs:
         env:
           UNSLOTH_IS_PRESENT: '1'
           UNSLOTH_COMPILE_DISABLE: '1'
+          TORCHDYNAMO_DISABLE: '1'
+          TORCH_COMPILE_DISABLE: '1'
           PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION: python
         run: |
           pip install --upgrade "git+https://github.com/huggingface/trl"
           cd unsloth
           python -c "import trl; print('Resolved TRL', trl.__version__)"
           PYTHONPATH=. python -m pytest \
             tests/version_compat/test_trl_grpo_fake_run.py \
+            tests/version_compat/test_trl_fake_train_cpu.py \
             -v --tb=short
 
   # Daily-only: same suites but with --strict on importable upstream

@@ -0,0 +1,285 @@
+# SPDX-License-Identifier: AGPL-3.0-only
+# Copyright 2026-present the Unsloth AI Inc. team.
+"""Fake CPU training runs for the Unsloth-patched SFT / GRPO / DPO trainers.
+
+The patch-run canary (test_trl_grpo_fake_run.py) only compiles + inspects the
+generated trainer source. This goes one layer deeper: it actually runs
+`trainer.train()` for a couple of steps on a CPU-only runner, under the CUDA
+spoof, wrapping a plain (tiny, random-weight) HF model in the Unsloth-patched
+trainer. That exercises the real train() loop at runtime -- data collation,
+generation (GRPO), the injected `_get_per_token_logps_and_entropies`, loss,
+backward, optimizer -- so a TRL or transformers change that breaks the loop
+(not just the source structure) surfaces here. No GPU, no meaningful numerics.
+
+What it does NOT cover: Unsloth's Triton/GPU-optimized model kernels (the
+FastLanguageModel fast path) cannot run on CPU, so this validates the
+trainer-transform + orchestration layer with a standard forward, not the
+optimized kernels.
+"""
+
+from __future__ import annotations
+
+import os
+
+# CPU-only: no torch.compile / dynamo (it reaches into the CUDA accelerator), no
+# Unsloth kernel compile, no mixed precision. Must be set before torch/unsloth.
+os.environ.setdefault("UNSLOTH_COMPILE_DISABLE", "1")
+os.environ.setdefault("TORCHDYNAMO_DISABLE", "1")
+os.environ.setdefault("TORCH_COMPILE_DISABLE", "1")
+os.environ.setdefault("ACCELERATE_MIXED_PRECISION", "no")
+
+import importlib
+import importlib.util
+import sys
+from pathlib import Path
+
+import pytest
+
+
+# torch is needed for everything below (daily-fresh-fetch collects this dir with
+# only pytest installed); skip the whole module cleanly when it is absent.
+if importlib.util.find_spec("torch") is None:
+    pytest.skip(
+        "torch not installed; fake CPU train needs the real runtime", allow_module_level = True
+    )
+
+# Apply the CUDA spoof before any unsloth-touching import.
+_SPOOF_DIR = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(_SPOOF_DIR))
+import _zoo_aggressive_cuda_spoof as _spoof  # noqa: E402
+
+_spoof.apply()
+
+import torch  # noqa: E402
+
+
+# The generated GRPO trainer hard-decorates hot functions with @torch.compile,
+# which dynamo processes even under the disable env vars, reaching into
+# torch.accelerator (real CUDA) on a GPU-less box. Make torch.compile an eager
+# passthrough before unsloth generates/imports the trainer -- same logic, no
+# dynamo. (An eager CPU run is exactly what we want here.)
+def _eager_compile(
+    model = None,
+    *args,
+    **kwargs,
+):
+    if callable(model):
+        return model
+    return lambda fn: fn
+
+
+torch.compile = _eager_compile
+
+# Belt-and-suspenders: if any @torch.compile still routes through dynamo, let it
+# fall back to eager instead of crashing, and stop its stream-capture probe from
+# reaching torch.accelerator -> real CUDA on a GPU-less box.
+try:
+    import torch._dynamo  # noqa: E402
+    torch._dynamo.config.suppress_errors = True
+except Exception:
+    pass
+if hasattr(torch, "accelerator"):
+    torch.accelerator.is_available = lambda *a, **k: False
+
+
+# Redirect any `device="cuda"` tensor allocation / `.to("cuda")` / `.cuda()` to
+# CPU. The aggressive spoof deliberately keeps real allocators, but a fake CPU
+# train needs cuda-targeted ops (e.g. inductor's init_gpu_context does
+# `torch.empty(1, device="cuda")`) to land on CPU instead of erroring.
+def _is_cuda_dev(d):
+    try:
+        return d is not None and torch.device(d).type == "cuda"
+    except Exception:
+        return False
+
+
+for _name in (
+    "empty",
+    "zeros",
+    "ones",
+    "full",
+    "tensor",
+    "arange",
+    "randn",
+    "rand",
+    "randint",
+    "empty_like",
+    "zeros_like",
+    "ones_like",
+):
+    _orig = getattr(torch, _name, None)
+    if _orig is None:
+        continue
+
+    def _redir(
+        *args,
+        _orig = _orig,
+        **kwargs,
+    ):
+        if _is_cuda_dev(kwargs.get("device")):
+            kwargs["device"] = "cpu"
+        return _orig(*args, **kwargs)
+
+    setattr(torch, _name, _redir)
+
+_orig_to = torch.Tensor.to
+
+
+def _to_cpu(self, *args, **kwargs):
+    args = tuple("cpu" if _is_cuda_dev(a) else a for a in args)
+    if _is_cuda_dev(kwargs.get("device")):
+        kwargs["device"] = "cpu"
+    return _orig_to(self, *args, **kwargs)
+
+
+torch.Tensor.to = _to_cpu
+torch.Tensor.cuda = lambda self, *a, **k: self
+
+# Extra CUDA stubs the aggressive spoof lacks, needed to walk a real train():
+# Adam's _cuda_graph_capture_health_check() probes stream capture.
+torch.cuda.is_current_stream_capturing = lambda *a, **k: False
+try:
+    import torch.cuda.graphs as _cg  # noqa: E402
+    _cg._cuda_isCurrentStreamCapturing = lambda *a, **k: False
+except Exception:
+    pass
+
+# A broken libmlx.so in the shared site-packages crashes transformers' Mac-only
+# is_mlx_array probe on Linux; disable it.
+try:
+    import transformers.utils.generic as _g  # noqa: E402
+    _g._is_mlx_available = False
+except Exception:
+    pass
+
+
+# Dense (non-MoE) tiny model on purpose: MoE models route through Unsloth's
+# grouped_gemm Triton kernel, which is CUDA-only and cannot run on a CPU runner.
+_MODEL = "hf-internal-testing/tiny-random-LlamaForCausalLM"
+
+
+def _load_plain():
+    """Tiny plain HF model + tokenizer on CPU. Skips (not fails) if the model
+    cannot be fetched -- that is a network/hub issue, not an unsloth regression."""
+    from transformers import AutoModelForCausalLM, AutoTokenizer
+
+    try:
+        tok = AutoTokenizer.from_pretrained(_MODEL)
+        model = AutoModelForCausalLM.from_pretrained(_MODEL, dtype = torch.float32)
+    except OSError as e:  # hub unreachable / model missing
+        pytest.skip(f"could not fetch {_MODEL} (network/hub): {str(e)[:150]}")
+    if tok.pad_token is None:
+        tok.pad_token = tok.eos_token
+    # Unsloth's GRPO path calls model.for_training()/for_inference() (added by
+    # FastLanguageModel). A plain HF model lacks them; supply minimal train/eval
+    # equivalents so the loop proceeds without the optimized wrapper.
+    if not hasattr(model, "for_training"):
+        model.for_training = lambda *a, **k: model.train()
+    if not hasattr(model, "for_inference"):
+        model.for_inference = lambda *a, **k: model.eval()
+    return model.to("cpu"), tok
+
+
+@pytest.fixture(autouse = True)
+def _require_stack():
+    global torch  # the `import torch._dynamo` below would otherwise shadow it as local
+    if importlib.util.find_spec("unsloth") is None or importlib.util.find_spec("trl") is None:
+        pytest.skip("unsloth or trl not installed")
+    # A real import failure is a regression we want to surface, so do not guard it.
+    import unsloth  # noqa: F401  -- patches TRL trainers to the Unsloth variants
+
+    # `import unsloth` reinstalls the real torch.compile (overwriting the eager
+    # passthrough set at module load), so the GRPO hot path (chunked_selective_
+    # log_softmax) would really compile -- and inductor picks the spoofed CUDA
+    # device, crashing on device props (`gcnArchName`). Re-apply the eager
+    # passthrough and flip dynamo's call-time kill switch so every @torch.compile
+    # runs eager regardless of when it was decorated. CPU eager is what we want.
+    torch.compile = _eager_compile
+    try:
+        import torch._dynamo  # noqa: E402
+        torch._dynamo.config.disable = True
+    except Exception:
+        pass
+
+
+def test_sft_trains_on_cpu(tmp_path):
+    from datasets import Dataset
+    from trl import SFTConfig, SFTTrainer
+
+    assert SFTTrainer.__name__ == "UnslothSFTTrainer", "SFT patch did not apply"
+    model, tok = _load_plain()
+    ds = Dataset.from_list([{"text": "The quick brown fox jumps over the lazy dog."}] * 8)
+    cfg = SFTConfig(
+        output_dir = str(tmp_path / "ci_sft"),
+        per_device_train_batch_size = 2,
+        max_steps = 2,
+        logging_steps = 1,
+        report_to = "none",
+        save_strategy = "no",
+        use_cpu = True,
+        max_length = None,
+        padding_free = False,
+        dataset_text_field = "text",
+        fp16 = False,
+        bf16 = False,
+        optim = "adamw_torch",
+    )
+    SFTTrainer(model = model, processing_class = tok, args = cfg, train_dataset = ds).train()
+
+
+def test_grpo_trains_on_cpu(tmp_path):
+    from datasets import Dataset
+    from trl import GRPOConfig, GRPOTrainer
+
+    assert GRPOTrainer.__name__ == "UnslothGRPOTrainer", "GRPO patch did not apply"
+    model, tok = _load_plain()
+    ds = Dataset.from_list([{"prompt": "hi there"}] * 4)
+    cfg = GRPOConfig(
+        output_dir = str(tmp_path / "ci_grpo"),
+        per_device_train_batch_size = 2,
+        num_generations = 2,
+        max_steps = 2,
+        max_completion_length = 8,
+        logging_steps = 1,
+        report_to = "none",
+        temperature = 1.0,
+        beta = 0.0,
+        save_strategy = "no",
+        use_cpu = True,
+        use_vllm = False,
+        fp16 = False,
+        bf16 = False,
+        optim = "adamw_torch",
+    )
+    GRPOTrainer(
+        model = model,
+        processing_class = tok,
+        reward_funcs = [lambda completions, **k: [float(len(c)) for c in completions]],
+        args = cfg,
+        train_dataset = ds,
+    ).train()
+
+
+def test_dpo_trains_on_cpu(tmp_path):
+    from datasets import Dataset
+    from trl import DPOConfig, DPOTrainer
+
+    assert DPOTrainer.__name__ == "UnslothDPOTrainer", "DPO patch did not apply"
+    model, tok = _load_plain()
+    ds = Dataset.from_list(
+        [{"prompt": "Hi", "chosen": " hello friend", "rejected": " go away"}] * 8
+    )
+    cfg = DPOConfig(
+        output_dir = str(tmp_path / "ci_dpo"),
+        per_device_train_batch_size = 2,
+        max_steps = 2,
+        logging_steps = 1,
+        report_to = "none",
+        save_strategy = "no",
+        use_cpu = True,
+        beta = 0.1,
+        fp16 = False,
+        bf16 = False,
+        optim = "adamw_torch",
+    )
+    DPOTrainer(model = model, processing_class = tok, args = cfg, train_dataset = ds).train()