feat: add processor_kwargs YAML field forwarded to from_pretrained

src/axolotl/loaders/processor.py

@@ -23,6 +23,8 @@ def load_processor(cfg: DictDefault, tokenizer: PreTrainedTokenizerBase):
     processor_kwargs = {}
     if cfg.revision_of_model:
         processor_kwargs["revision"] = cfg.revision_of_model
+    if cfg.processor_kwargs:
+        processor_kwargs.update(cfg.processor_kwargs)
 
     if cfg.tokenizer_use_mistral_common:
 

src/axolotl/utils/schemas/model.py

@@ -64,6 +64,12 @@ class ModelInputConfig(BaseModel):
     processor_type: str | None = Field(
         default=None, json_schema_extra={"description": "transformers processor class"}
     )
+    processor_kwargs: dict[str, Any] | None = Field(
+        default=None,
+        json_schema_extra={
+            "description": "kwargs forwarded to the processor's from_pretrained(), overriding processor config (e.g. image_seq_length, min_pixels, etc.)."
+        },
+    )
     tokenizer_save_jinja_files: bool | None = Field(
         default=True,  # match the default behavior from transformers
         json_schema_extra={
@@ -107,6 +113,22 @@ def hint_trust_remote_code(cls, trust_remote_code):
             )
         return trust_remote_code
 
+    @field_validator("processor_kwargs")
+    @classmethod
+    def reject_reserved_processor_kwargs(cls, processor_kwargs):
+        if not processor_kwargs:
+            return processor_kwargs
+        reserved = {"revision", "trust_remote_code"}
+        conflicts = reserved.intersection(processor_kwargs)
+        if conflicts:
+            raise ValueError(
+                "Do not set reserved keys "
+                f"{sorted(conflicts)} inside `processor_kwargs`; "
+                "use the top-level `revision_of_model` / `trust_remote_code` "
+                "config keys instead."
+            )
+        return processor_kwargs
+
 
 class ModelOutputConfig(BaseModel):
     """model save configuration subset"""

src/axolotl/utils/schemas/validation.py

@@ -558,6 +558,11 @@ def check_mistral_common_incompatible_options(cls, data):
                 "Setting chat_template is not supported with mistral-common tokenizer"
             )
 
+        if data.get("processor_kwargs"):
+            raise ValueError(
+                "processor_kwargs is not supported with mistral-common tokenizer"
+            )
+
         return data
 
     @model_validator(mode="before")

tests/test_revision_parameter.py

@@ -133,3 +133,108 @@ def test_load_processor_omits_revision_when_unset(self, mock_auto_processor):
 
         call_kwargs = mock_auto_processor.from_pretrained.call_args
         assert "revision" not in call_kwargs.kwargs
+
+    @patch("axolotl.loaders.processor.AutoProcessor")
+    def test_load_processor_forwards_processor_kwargs(self, mock_auto_processor):
+        mock_processor = MagicMock()
+        mock_processor.size = {}
+        mock_auto_processor.from_pretrained.return_value = mock_processor
+
+        cfg = DictDefault(
+            {
+                "processor_config": "some-model",
+                "trust_remote_code": False,
+                "processor_kwargs": {
+                    "image_seq_length": 1120,
+                    "max_soft_tokens": 1120,
+                },
+            }
+        )
+        tokenizer = MagicMock(spec=PreTrainedTokenizerBase)
+
+        from axolotl.loaders.processor import load_processor
+
+        load_processor(cfg, tokenizer)
+
+        call_kwargs = mock_auto_processor.from_pretrained.call_args
+        assert call_kwargs.kwargs.get("image_seq_length") == 1120
+        assert call_kwargs.kwargs.get("max_soft_tokens") == 1120
+
+    @patch("axolotl.loaders.processor.AutoProcessor")
+    def test_load_processor_omits_processor_kwargs_when_unset(
+        self, mock_auto_processor
+    ):
+        mock_processor = MagicMock()
+        mock_processor.size = {}
+        mock_auto_processor.from_pretrained.return_value = mock_processor
+
+        cfg = DictDefault(
+            {
+                "processor_config": "some-model",
+                "trust_remote_code": False,
+            }
+        )
+        tokenizer = MagicMock(spec=PreTrainedTokenizerBase)
+
+        from axolotl.loaders.processor import load_processor
+
+        load_processor(cfg, tokenizer)
+
+        call_kwargs = mock_auto_processor.from_pretrained.call_args
+        assert "image_seq_length" not in call_kwargs.kwargs
+        assert "max_soft_tokens" not in call_kwargs.kwargs
+
+    def test_processor_kwargs_schema_rejects_revision(self):
+        import pytest
+
+        from axolotl.utils.schemas.model import ModelInputConfig
+
+        with pytest.raises(ValueError, match="revision"):
+            ModelInputConfig(
+                base_model="some-model",
+                processor_kwargs={"revision": "abc123"},
+            )
+
+    def test_processor_kwargs_schema_rejects_trust_remote_code(self):
+        import pytest
+
+        from axolotl.utils.schemas.model import ModelInputConfig
+
+        with pytest.raises(ValueError, match="trust_remote_code"):
+            ModelInputConfig(
+                base_model="some-model",
+                processor_kwargs={"trust_remote_code": True},
+            )
+
+    def test_processor_kwargs_schema_accepts_valid_keys(self):
+        from axolotl.utils.schemas.model import ModelInputConfig
+
+        cfg = ModelInputConfig(
+            base_model="some-model",
+            processor_kwargs={"image_seq_length": 1120, "max_soft_tokens": 1120},
+        )
+        assert cfg.processor_kwargs == {
+            "image_seq_length": 1120,
+            "max_soft_tokens": 1120,
+        }
+
+    def test_processor_kwargs_schema_accepts_none_and_empty(self):
+        from axolotl.utils.schemas.model import ModelInputConfig
+
+        assert ModelInputConfig(base_model="x").processor_kwargs is None
+        assert (
+            ModelInputConfig(base_model="x", processor_kwargs={}).processor_kwargs == {}
+        )
+
+    def test_processor_kwargs_incompatible_with_mistral_common(self, min_base_cfg):
+        import pytest
+
+        from axolotl.utils.config import validate_config
+        from axolotl.utils.dict import DictDefault
+
+        cfg = min_base_cfg | DictDefault(
+            tokenizer_use_mistral_common=True,
+            processor_kwargs={"image_seq_length": 1120},
+        )
+        with pytest.raises(ValueError, match="processor_kwargs"):
+            validate_config(cfg)