[diffusion] Fix GLM-Image resolution alignment (#32999)

Co-authored-by: AuFlow <AuFlow@users.noreply.github.com>

python/sglang/multimodal_gen/configs/sample/glmimage.py

@@ -1,6 +1,11 @@
 from dataclasses import dataclass
 
 from sglang.multimodal_gen.configs.sample.sampling_params import SamplingParams
+from sglang.multimodal_gen.runtime.utils.logging_utils import init_logger
+
+logger = init_logger(__name__)
+
+GLM_IMAGE_RESOLUTION_ALIGNMENT = 32
 
 
 @dataclass
@@ -10,3 +15,39 @@ class GlmImageSamplingParams(SamplingParams):
     num_frames: int = 1
     guidance_scale: float = 1.5
     num_inference_steps: int = 30
+
+    def _adjust(self, server_args):
+        requested_width = self.width
+        requested_height = self.height
+        if self.width is not None and self.height is not None:
+            self.width, self.height = align_glm_image_resolution(
+                self.width, self.height
+            )
+            if (self.width, self.height) != (
+                requested_width,
+                requested_height,
+            ):
+                logger.warning(
+                    "GLM-Image requires dimensions divisible by %s; adjusted "
+                    "requested resolution from %sx%s to %sx%s",
+                    GLM_IMAGE_RESOLUTION_ALIGNMENT,
+                    requested_width,
+                    requested_height,
+                    self.width,
+                    self.height,
+                )
+        super()._adjust(server_args)
+
+
+def align_glm_image_dimension(value: int) -> int:
+    """Round a GLM-Image dimension up to a supported multiple."""
+    return max(
+        GLM_IMAGE_RESOLUTION_ALIGNMENT,
+        (value + GLM_IMAGE_RESOLUTION_ALIGNMENT - 1)
+        // GLM_IMAGE_RESOLUTION_ALIGNMENT
+        * GLM_IMAGE_RESOLUTION_ALIGNMENT,
+    )
+
+
+def align_glm_image_resolution(width: int, height: int) -> tuple[int, int]:
+    return align_glm_image_dimension(width), align_glm_image_dimension(height)

python/sglang/multimodal_gen/runtime/entrypoints/openai/image_api.py

@@ -19,8 +19,13 @@ from fastapi import (
     UploadFile,
 )
 from fastapi.responses import FileResponse
+from PIL import Image
 
-from sglang.multimodal_gen.configs.sample.sampling_params import generate_request_id
+from sglang.multimodal_gen.configs.sample.glmimage import GlmImageSamplingParams
+from sglang.multimodal_gen.configs.sample.sampling_params import (
+    SamplingParams,
+    generate_request_id,
+)
 from sglang.multimodal_gen.runtime.entrypoints.openai.protocol import (
     ImageGenerationsRequest,
     ImageResponse,
@@ -170,6 +175,7 @@ def _build_image_response_kwargs(
     fallback_url: str | None = None,
     fallback_urls: list[str] | None = None,
     is_persistent: bool = True,
+    resize: str | None = None,
 ) -> dict:
     """Build ImageResponse data list.
 
@@ -186,6 +192,7 @@ def _build_image_response_kwargs(
                 b64_json=b64,
                 revised_prompt=prompt,
                 file_path=os.path.abspath(path) if is_persistent else None,
+                resize=resize,
             )
             for b64, path in zip(b64_list, save_file_path_list)
         ]
@@ -210,6 +217,7 @@ def _build_image_response_kwargs(
                     url=url,
                     revised_prompt=prompt,
                     file_path=os.path.abspath(path) if is_persistent else None,
+                    resize=resize,
                 )
             )
 
@@ -231,6 +239,28 @@ def _build_image_response_kwargs(
     return ret
 
 
+def _get_response_resize(
+    sampling_params: SamplingParams, output_path: str | None = None
+) -> str | None:
+    """Return a generated GLM-Image output's actual size as WIDTHxHEIGHT."""
+    if not isinstance(sampling_params, GlmImageSamplingParams):
+        return None
+
+    if output_path is not None:
+        try:
+            with Image.open(output_path) as output_image:
+                width, height = output_image.size
+            return f"{width}x{height}"
+        except (OSError, ValueError):
+            # Fall back to the aligned sampling canvas if the output cannot be
+            # inspected (for example, for a custom output transport).
+            pass
+
+    if sampling_params.width is None or sampling_params.height is None:
+        return None
+    return sampling_params.output_size_str()
+
+
 @router.post("/generations", response_model=ImageResponse)
 async def generations(
     request: ImageGenerationsRequest,
@@ -308,6 +338,7 @@ async def generations(
             async_scheduler_client, batch
         )
         save_file_path = save_file_path_list[0]
+        response_resize = _get_response_resize(sampling, save_file_path)
         resp_format = (request.response_format or "b64_json").lower()
         if (
             is_cosmos3
@@ -359,6 +390,7 @@ async def generations(
             cloud_urls=cloud_urls,
             fallback_urls=fallback_urls,
             is_persistent=is_persistent,
+            resize=response_resize,
         )
 
     return ImageResponse(**response_kwargs)
@@ -462,6 +494,7 @@ async def edits(
             async_scheduler_client, batch
         )
         save_file_path = save_file_path_list[0]
+        response_resize = _get_response_resize(sampling, save_file_path)
         resp_format = (response_format or "b64_json").lower()
 
         # read b64 before cloud upload may delete the local file
@@ -510,6 +543,7 @@ async def edits(
             cloud_urls=cloud_urls,
             fallback_urls=fallback_urls,
             is_persistent=is_persistent,
+            resize=response_resize,
         )
 
     return ImageResponse(**response_kwargs)

python/sglang/multimodal_gen/runtime/entrypoints/openai/protocol.py

@@ -13,6 +13,7 @@ class ImageResponseData(BaseModel):
     url: Optional[str] = None
     revised_prompt: Optional[str] = None
     file_path: Optional[str] = None
+    resize: Optional[str] = None
 
 
 class ImagePromptTokensDetails(BaseModel):

python/sglang/multimodal_gen/runtime/pipelines_core/stages/model_specific_stages/glm_image.py

@@ -11,6 +11,10 @@ import torch
 from diffusers.image_processor import VaeImageProcessor
 from diffusers.utils.torch_utils import randn_tensor
 
+from sglang.multimodal_gen.configs.sample.glmimage import (
+    GLM_IMAGE_RESOLUTION_ALIGNMENT,
+    align_glm_image_resolution,
+)
 from sglang.multimodal_gen.runtime.distributed import get_local_torch_device
 from sglang.multimodal_gen.runtime.managers.forward_context import set_forward_context
 from sglang.multimodal_gen.runtime.managers.memory_managers.component_manager import (
@@ -118,6 +122,26 @@ def image_path_to_list(image_path: Union[str, List[str]]) -> List[str]:
     return image_path if isinstance(image_path, list) else [image_path]
 
 
+def resize_glm_image_to_alignment(image: PIL.Image.Image) -> PIL.Image.Image:
+    """Resize an image up so both dimensions use GLM-Image's D32 grid."""
+    width, height = image.size
+    aligned_width, aligned_height = align_glm_image_resolution(width, height)
+    if (aligned_width, aligned_height) == (width, height):
+        return image
+    return image.resize((aligned_width, aligned_height), PIL.Image.Resampling.LANCZOS)
+
+
+def _validate_glm_image_resolution_alignment(width: int, height: int) -> None:
+    if (
+        height % GLM_IMAGE_RESOLUTION_ALIGNMENT != 0
+        or width % GLM_IMAGE_RESOLUTION_ALIGNMENT != 0
+    ):
+        raise ValueError(
+            "GLM-Image dimensions must be aligned before AR token generation, "
+            f"got {width}x{height}"
+        )
+
+
 def pooled_image_features_to_tensor(image_features) -> torch.Tensor:
     pooler_output = getattr(image_features, "pooler_output", None)
     if pooler_output is not None:
@@ -337,7 +361,6 @@ class GlmImageAR(PipelineStage):
         width: int,
         server_args: ServerArgs,
         image: Optional[List[PIL.Image.Image]] = None,
-        factor: int = 32,
         seed: Optional[int] = None,
     ) -> Tuple[torch.Tensor, Optional[List[torch.Tensor]], Optional[dict[str, int]]]:
         """
@@ -348,14 +371,11 @@ class GlmImageAR(PipelineStage):
             condition_images: Optional list of condition images for i2i
 
         Returns:
-            Tuple of (prior_token_ids, pixel_height, pixel_width)
+            Tuple of the D16 prior token IDs, optional source-image token IDs,
-            - prior_token_ids: Upsampled to d16 format, shape [1, token_h*token_w*4]
+            and optional usage statistics returned by an external AR server.
-            - pixel_height: Image height in pixels
-            - pixel_width: Image width in pixels
         """
         device = get_local_torch_device()
-        height = (height // factor) * factor
+        _validate_glm_image_resolution_alignment(width, height)
-        width = (width // factor) * factor
 
         is_text_to_image = image is None or len(image) == 0
         # Build messages for processor
@@ -456,11 +476,9 @@ class GlmImageAR(PipelineStage):
         height: int,
         width: int,
         server_args: ServerArgs,
-        factor: int = 32,
     ) -> tuple[list[torch.Tensor], list[dict[str, int] | None]]:
         device = get_local_torch_device()
-        height = (height // factor) * factor
+        _validate_glm_image_resolution_alignment(width, height)
-        width = (width // factor) * factor
 
         input_ids = []
         image_data = []
@@ -650,7 +668,7 @@ class GlmImageAR(PipelineStage):
         width = batch.width
         if batch.image_path is not None:
             ar_condition_images = [
-                load_image(img_path)
+                resize_glm_image_to_alignment(load_image(img_path))
                 for img_path in image_path_to_list(batch.image_path)
             ]
         else:
@@ -662,6 +680,20 @@ class GlmImageAR(PipelineStage):
             height = height or ar_condition_images[0].height
             width = width or ar_condition_images[0].width
 
+        requested_width = width
+        requested_height = height
+        width, height = align_glm_image_resolution(width, height)
+        if (width, height) != (requested_width, requested_height):
+            logger.warning(
+                "GLM-Image requires dimensions divisible by %s; adjusted "
+                "runtime resolution from %sx%s to %sx%s",
+                GLM_IMAGE_RESOLUTION_ALIGNMENT,
+                requested_width,
+                requested_height,
+                width,
+                height,
+            )
+
         time_start = time.time()
         num_outputs = _num_outputs_per_prompt(batch)
         seed = getattr(batch, "seed", None)
@@ -1037,7 +1069,7 @@ class GlmImageBeforeDenoisingStage(PipelineStage):
         num_inference_steps = batch.num_inference_steps
         if batch.image_path is not None:
             ar_condition_images = [
-                load_image(img_path)
+                resize_glm_image_to_alignment(load_image(img_path))
                 for img_path in image_path_to_list(batch.image_path)
             ]
         else:
@@ -1108,9 +1140,9 @@ class GlmImageBeforeDenoisingStage(PipelineStage):
                     if isinstance(img, PIL.Image.Image)
                     else img.shape[:2]
                 )
-                multiple_of = self.vae_scale_factor * self.transformer.config.patch_size
+                image_width, image_height = align_glm_image_resolution(
-                image_height = (image_height // multiple_of) * multiple_of
+                    image_width, image_height
-                image_width = (image_width // multiple_of) * multiple_of
+                )
                 img = self.image_processor.preprocess(
                     img, height=image_height, width=image_width
                 )

python/sglang/multimodal_gen/test/unit/test_glm_image_ar.py

@@ -1,13 +1,15 @@
 import unittest
 from types import SimpleNamespace
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 import torch
+from PIL import Image
 
+from sglang.multimodal_gen.configs.sample.glmimage import GlmImageSamplingParams
 from sglang.multimodal_gen.runtime.entrypoints.openai.image_api import (
     _build_image_response_kwargs,
 )
-from sglang.multimodal_gen.runtime.pipelines_core.schedule_batch import OutputBatch
+from sglang.multimodal_gen.runtime.pipelines_core.schedule_batch import OutputBatch, Req
 from sglang.multimodal_gen.runtime.pipelines_core.stages.model_specific_stages.glm_image import (
     GlmImageAR,
 )
@@ -200,6 +202,120 @@ class TestGlmImageARSrtBackend(unittest.TestCase):
                 server_args=self._server_args(),
             )
 
+    @patch(
+        "sglang.multimodal_gen.runtime.pipelines_core.stages."
+        "model_specific_stages.glm_image.get_local_torch_device",
+        return_value=torch.device("cpu"),
+    )
+    def test_forward_aligns_runtime_dimensions_before_ar_generation(self, _mock_device):
+        stage = GlmImageAR(processor=_FakeProcessor(), vision_language_encoder=None)
+        stage.generate_prior_tokens = MagicMock(
+            return_value=(torch.zeros((1, 1), dtype=torch.long), None, None)
+        )
+        cases = [
+            ((500, 500), (512, 512)),
+            ((550, 1009), (576, 1024)),
+            ((1280, 720), (1280, 736)),
+        ]
+
+        for requested, expected in cases:
+            with self.subTest(requested=requested):
+                stage.generate_prior_tokens.reset_mock()
+                sampling = GlmImageSamplingParams(
+                    prompt="A simple product sketch",
+                    width=requested[0],
+                    height=requested[1],
+                )
+                sampling.seed = None
+                batch = Req(sampling_params=sampling)
+
+                stage.forward(batch, self._server_args())
+
+                self.assertEqual((batch.width, batch.height), expected)
+                stage.generate_prior_tokens.assert_called_once_with(
+                    prompt="A simple product sketch",
+                    image=None,
+                    height=expected[1],
+                    width=expected[0],
+                    server_args=self._server_args(),
+                )
+
+    @patch(
+        "sglang.multimodal_gen.runtime.pipelines_core.stages."
+        "model_specific_stages.glm_image.get_local_torch_device",
+        return_value=torch.device("cpu"),
+    )
+    @patch(
+        "sglang.multimodal_gen.runtime.pipelines_core.stages."
+        "model_specific_stages.glm_image.load_image",
+        return_value=Image.new("RGB", (1280, 720)),
+    )
+    def test_forward_resizes_edit_image_up_to_d32_grid(
+        self, _mock_load_image, _mock_device
+    ):
+        stage = GlmImageAR(processor=_FakeProcessor(), vision_language_encoder=None)
+        stage.generate_prior_tokens = MagicMock(
+            return_value=(torch.zeros((1, 1), dtype=torch.long), None, None)
+        )
+        sampling = GlmImageSamplingParams(
+            prompt="Edit this image",
+            width=1280,
+            height=720,
+            image_path="input.png",
+        )
+        sampling.seed = None
+        batch = Req(sampling_params=sampling)
+
+        stage.forward(batch, self._server_args())
+
+        call_kwargs = stage.generate_prior_tokens.call_args.kwargs
+        self.assertEqual((batch.width, batch.height), (1280, 736))
+        self.assertEqual(call_kwargs["image"][0].size, (1280, 736))
+        self.assertEqual((call_kwargs["width"], call_kwargs["height"]), (1280, 736))
+
+    @patch(
+        "sglang.multimodal_gen.runtime.pipelines_core.stages."
+        "model_specific_stages.glm_image.get_local_torch_device",
+        return_value=torch.device("cpu"),
+    )
+    def test_generate_prior_tokens_rejects_unaligned_internal_dimensions(
+        self, _mock_device
+    ):
+        stage = GlmImageAR(processor=_FakeProcessor(), vision_language_encoder=None)
+
+        with self.assertRaisesRegex(
+            ValueError,
+            "GLM-Image dimensions must be aligned before AR token generation",
+        ):
+            stage.generate_prior_tokens(
+                prompt="A simple product sketch",
+                height=1024,
+                width=550,
+                server_args=self._server_args(),
+            )
+
+    @patch(
+        "sglang.multimodal_gen.runtime.pipelines_core.stages."
+        "model_specific_stages.glm_image.get_local_torch_device",
+        return_value=torch.device("cpu"),
+    )
+    def test_generate_prior_tokens_batch_rejects_unaligned_internal_dimensions(
+        self, _mock_device
+    ):
+        stage = GlmImageAR(processor=_FakeProcessor(), vision_language_encoder=None)
+
+        with self.assertRaisesRegex(
+            ValueError,
+            "GLM-Image dimensions must be aligned before AR token generation",
+        ):
+            stage.generate_prior_tokens_batch(
+                prompts=["A simple product sketch"],
+                seeds=[42],
+                height=1024,
+                width=550,
+                server_args=self._server_args(),
+            )
+
     def test_image_response_adds_image_count_to_usage(self):
         set_global_server_args(SimpleNamespace(enable_cache_report=False))
         response = _build_image_response_kwargs(

python/sglang/multimodal_gen/test/unit/test_openai_image_api.py

@@ -1,10 +1,14 @@
 import os
 
 from fastapi import HTTPException
+from PIL import Image
 
+from sglang.multimodal_gen.configs.sample.glmimage import GlmImageSamplingParams
+from sglang.multimodal_gen.configs.sample.sampling_params import SamplingParams
 from sglang.multimodal_gen.runtime.entrypoints.openai.image_api import (
     _build_image_response_kwargs,
     _fallback_image_urls,
+    _get_response_resize,
     _raise_if_image_variant_not_found,
     _select_image_variant_cloud_url,
     _select_image_variant_path,
@@ -36,6 +40,46 @@ def test_url_response_returns_one_item_per_output_path():
     ]
 
 
+def test_image_response_includes_resize_for_every_output():
+    response = _build_image_response_kwargs(
+        ["first.png", "second.png"],
+        "b64_json",
+        "a lantern",
+        "req-123",
+        OutputBatch(),
+        b64_list=["first", "second"],
+        resize="1280x736",
+    )
+
+    assert [item.resize for item in response["data"]] == [
+        "1280x736",
+        "1280x736",
+    ]
+
+
+def test_response_resize_is_only_populated_for_glm_image():
+    glm_sampling = GlmImageSamplingParams(width=1280, height=736)
+
+    assert _get_response_resize(glm_sampling) == "1280x736"
+    assert _get_response_resize(SamplingParams(width=1280, height=736)) is None
+
+
+def test_response_resize_uses_actual_generated_image_size(tmp_path):
+    output_path = tmp_path / "output.png"
+    Image.new("RGB", (1280, 736)).save(output_path)
+    glm_sampling = GlmImageSamplingParams(image_path="input.png")
+
+    assert _get_response_resize(glm_sampling, str(output_path)) == "1280x736"
+
+
+def test_response_resize_prefers_final_output_over_sampling_canvas(tmp_path):
+    output_path = tmp_path / "upscaled.png"
+    Image.new("RGB", (2560, 1472)).save(output_path)
+    glm_sampling = GlmImageSamplingParams(width=1280, height=736)
+
+    assert _get_response_resize(glm_sampling, str(output_path)) == "2560x1472"
+
+
 def test_url_response_uses_variant_fallback_urls_for_multiple_persistent_outputs():
     paths = ["first.png", "second.png"]
 

python/sglang/multimodal_gen/test/unit/test_openai_utils.py

@@ -2,13 +2,17 @@
 
 import asyncio
 import io
+from types import SimpleNamespace
 
 from starlette.datastructures import UploadFile as StarletteUploadFile
 
+from sglang.multimodal_gen.configs.sample.sampling_params import SamplingParams
+from sglang.multimodal_gen.runtime.entrypoints.openai import utils as openai_utils
 from sglang.multimodal_gen.runtime.entrypoints.openai.utils import (
     _parse_size_or_raise,
     _save_upload_to_path,
     _validate_positive_int,
+    build_sampling_params,
 )
 
 
@@ -57,3 +61,49 @@ def test_validate_positive_int_rejects_non_positive_sampling_fields():
         assert "num_frames must be positive" in exc.detail
     else:
         raise AssertionError("expected bad request")
+
+
+def test_build_sampling_params_resolves_size_and_explicit_dimensions(monkeypatch):
+    server_args = SimpleNamespace(model_path="zai-org/GLM-Image")
+    monkeypatch.setattr(openai_utils, "get_global_server_args", lambda: server_args)
+    captured = {}
+
+    def fake_from_user_sampling_params_args(**kwargs):
+        captured.update(kwargs)
+        return SimpleNamespace()
+
+    monkeypatch.setattr(
+        SamplingParams,
+        "from_user_sampling_params_args",
+        fake_from_user_sampling_params_args,
+    )
+
+    cases = [
+        (
+            {"size": "500x500", "width": None, "height": None},
+            (500, 500),
+        ),
+        (
+            {"size": "1024x1024", "width": None, "height": 600},
+            (1024, 600),
+        ),
+        (
+            {"size": "500x500", "width": None, "height": 600},
+            (500, 600),
+        ),
+        (
+            {"size": "500x500", "width": 600, "height": None},
+            (600, 500),
+        ),
+        (
+            {"size": "500x500", "width": 600, "height": 700},
+            (600, 700),
+        ),
+    ]
+
+    for request_fields, expected in cases:
+        captured.clear()
+
+        build_sampling_params("request-id", **request_fields)
+
+        assert (captured["width"], captured["height"]) == expected

python/sglang/multimodal_gen/test/unit/test_sampling_params.py

@@ -4,6 +4,9 @@ import unittest
 from types import SimpleNamespace
 from unittest.mock import MagicMock, patch
 
+from sglang.multimodal_gen.configs.pipeline_configs.glm_image import (
+    GlmImagePipelineConfig,
+)
 from sglang.multimodal_gen.configs.pipeline_configs.ltx_2 import (
     LTX2PipelineConfig,
     is_ltx23_native_variant,
@@ -17,6 +20,10 @@ from sglang.multimodal_gen.configs.sample.flux import (
     Flux2SamplingParams,
     FluxSamplingParams,
 )
+from sglang.multimodal_gen.configs.sample.glmimage import (
+    GlmImageSamplingParams,
+    align_glm_image_dimension,
+)
 from sglang.multimodal_gen.configs.sample.qwenimage import QwenImageSamplingParams
 from sglang.multimodal_gen.configs.sample.sampling_params import (
     SamplingParams,
@@ -100,6 +107,65 @@ class TestSamplingParamsValidate(unittest.TestCase):
 
 
 class TestSamplingParamsSubclass(unittest.TestCase):
+    def test_glm_image_rounds_resolution_up_to_multiple_of_32(self):
+        server_args = SimpleNamespace(
+            pipeline_config=GlmImagePipelineConfig(),
+            output_path=None,
+            comfyui_mode=True,
+        )
+        cases = [
+            ((500, 500), (512, 512)),
+            ((1024, 600), (1024, 608)),
+            ((500, 600), (512, 608)),
+            ((550, 1009), (576, 1024)),
+            ((1280, 720), (1280, 736)),
+        ]
+
+        for requested, expected in cases:
+            with self.subTest(requested=requested):
+                params = GlmImageSamplingParams(
+                    width=requested[0],
+                    height=requested[1],
+                )
+
+                with patch(
+                    "sglang.multimodal_gen.configs.sample.glmimage.logger.warning"
+                ) as mock_warning:
+                    params._adjust(server_args)
+
+                self.assertEqual((params.width, params.height), expected)
+                mock_warning.assert_called_once_with(
+                    "GLM-Image requires dimensions divisible by %s; adjusted "
+                    "requested resolution from %sx%s to %sx%s",
+                    32,
+                    requested[0],
+                    requested[1],
+                    expected[0],
+                    expected[1],
+                )
+
+    def test_glm_image_resolution_rounds_up(self):
+        self.assertEqual(align_glm_image_dimension(560), 576)
+
+    def test_glm_image_resolution_keeps_minimum_alignment(self):
+        self.assertEqual(align_glm_image_dimension(0), 32)
+        self.assertEqual(align_glm_image_dimension(-1), 32)
+
+    def test_glm_image_does_not_warn_for_aligned_resolution(self):
+        server_args = SimpleNamespace(
+            pipeline_config=GlmImagePipelineConfig(),
+            output_path=None,
+            comfyui_mode=True,
+        )
+        params = GlmImageSamplingParams(width=1024, height=1024)
+
+        with patch(
+            "sglang.multimodal_gen.configs.sample.glmimage.logger.warning"
+        ) as mock_warning:
+            params._adjust(server_args)
+
+        mock_warning.assert_not_called()
+
     def test_flux_defaults_resolution_when_not_provided(self):
         params = FluxSamplingParams()