diff --git a/imagepipeline/core/pipeline.py b/imagepipeline/core/pipeline.py
index 8bcf516..f841671 100644
--- a/imagepipeline/core/pipeline.py
+++ b/imagepipeline/core/pipeline.py
@@ -4,14 +4,13 @@ from collections import defaultdict
 from pathlib import Path
 from typing import Any
 
+# Register all built-in modules (side effect of submodule imports).
+import imagepipeline.modules  # noqa: F401
 from imagepipeline.core.exceptions import ValidationError
 from imagepipeline.core.runner import PipelineRunner
 from imagepipeline.core.step import INPUT_SOURCE, StepDefinition, StepRef
 from imagepipeline.modules.registry import get_module
 
-# Import built-in modules so they register on package load.
-import imagepipeline.modules.imagemagick_grayscale  # noqa: F401
-
 
 class Pipeline:
     """Define and run an image processing pipeline."""
@@ -61,9 +60,7 @@ class Pipeline:
         input_refs = self._normalize_inputs(inputs)
         reserved = {"inputs", "input"}
         if reserved & set(params):
-            raise ValidationError(
-                "Do not pass 'inputs' or 'input' as module parameters"
-            )
+            raise ValidationError("Do not pass 'inputs' or 'input' as module parameters")
 
         definition = StepDefinition(
             step_id=step_id,
@@ -97,9 +94,7 @@ class Pipeline:
     def output_root(self) -> Path | None:
         return self._output_root
 
-    def _normalize_inputs(
-        self, inputs: StepRef | str | list[StepRef | str]
-    ) -> list[str]:
+    def _normalize_inputs(self, inputs: StepRef | str | list[StepRef | str]) -> list[str]:
         if isinstance(inputs, list):
             if not inputs:
                 raise ValidationError("inputs must not be an empty list")
@@ -110,9 +105,7 @@ class Pipeline:
         if not step_id:
             raise ValidationError("step_id must not be empty")
         if "/" in step_id or "\\" in step_id:
-            raise ValidationError(
-                f"step_id must not contain path separators: {step_id!r}"
-            )
+            raise ValidationError(f"step_id must not contain path separators: {step_id!r}")
         if any(step.step_id == step_id for step in self._steps):
             raise ValidationError(f"Duplicate step_id: {step_id!r}")
 
diff --git a/imagepipeline/modules/gmic_grayscale.py b/imagepipeline/modules/gmic_grayscale.py
index 3561afe..6a673f6 100644
--- a/imagepipeline/modules/gmic_grayscale.py
+++ b/imagepipeline/modules/gmic_grayscale.py
@@ -4,7 +4,7 @@ from imagepipeline.core.context import ModuleContext
 from imagepipeline.core.params import Param
 from imagepipeline.modules.base import SubprocessModule
 from imagepipeline.modules.registry import register
-from imagepipeline.utils.gmic import split_gmic_command
+from imagepipeline.utils.gmic import finalize_gmic_output, split_gmic_command
 from imagepipeline.utils.subprocess import run_command
 
 
@@ -35,3 +35,4 @@ class GmicGrayscale(SubprocessModule):
             dst = ctx.output_dir / src.name
             cmd = ["gmic", str(src), *split_gmic_command(gmic_command), "-output", str(dst)]
             run_command(cmd, timeout=self.default_timeout)
+            finalize_gmic_output(ctx.output_dir, dst)
diff --git a/imagepipeline/modules/imagemagick_grayscale.py b/imagepipeline/modules/imagemagick_grayscale.py
index aec0e75..ae741d9 100644
--- a/imagepipeline/modules/imagemagick_grayscale.py
+++ b/imagepipeline/modules/imagemagick_grayscale.py
@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-from pathlib import Path
-
 from imagepipeline.core.context import ModuleContext
 from imagepipeline.core.params import Param
 from imagepipeline.modules.base import SubprocessModule
@@ -34,8 +32,5 @@ class ImageMagickGrayscale(SubprocessModule):
         for index, src in enumerate(ctx.input_paths, start=1):
             self.log_image(ctx, index, total, src)
             dst = ctx.output_dir / src.name
-            if command == "magick":
-                cmd = [command, str(src), "-colorspace", colorspace, str(dst)]
-            else:
-                cmd = [command, str(src), "-colorspace", colorspace, str(dst)]
+            cmd = [command, str(src), "-colorspace", colorspace, str(dst)]
             run_command(cmd)