Bugfix/docker bake linux amd64 macos

README.md

@@ -254,6 +254,17 @@ aswfdocker --verbose build --ci-image-type IMAGE --group vfx1 --version 2026 --t
 aswfdocker build --ci-image-type aswftesting/ci-openexr:2026
 ```
 
+### Building on macOS
+
+Native macOS support is our goal, but due to limited resources, active development is intermittent. In the meantime, our existing build workflows only build Linux artifacts on macOS: `aswfdocker` drives Linux containers (for example `linux/amd64` images and Conan packages for Linux), not native macOS toolchains.
+
+Configure Docker with a minimum of:
+
+- 8 CPU cores allocated to Docker
+- 16 GB of memory allocated to Docker
+
+Due to conflicts with Rosetta, [buildx](https://docs.docker.com/buildx/working-with-buildx/) should be run on the Docker VMM.
+
 ### Windows Considerations
 
 Native Windows support is our goal, but due to limited resources, active development is intermittent. In the meantime, our existing build workflows work under WSL.
@@ -272,7 +283,6 @@ Native Windows support is our goal, but due to limited resources, active develop
 
     [Here](https://docs.astral.sh/uv/) are the `uv` docs. 
 
-
 ## Use Cases
 
 ### GitHub Actions

python/aswfdocker/builder.py

@@ -3,10 +3,12 @@
 """
 CI Image and Package Builder
 """
+
 import logging
 import subprocess
 import json
 import os
+import sys
 import tempfile
 import typing
 
@@ -114,6 +116,9 @@ def make_bake_dict(
                     "id=conan_password,env=CONAN_PASSWORD",
                 ],
             }
+            # Docker Desktop on Apple Silicon defaults to linux/arm64; pin amd64 to match CI.
+            if sys.platform == "darwin":
+                target_dict["platforms"] = ["linux/amd64"]
             root["target"][f"{image}-{major_version}"] = target_dict
 
         root["group"] = {"default": {"targets": list(root["target"].keys())}}

python/aswfdocker/tests/test_builder.py

@@ -8,6 +8,7 @@
 import unittest
 import logging
 import tempfile
+from unittest.mock import patch
 
 from click.testing import CliRunner
 
@@ -22,6 +23,43 @@ def setUp(self):
             repo_uri="notauri", source_branch="testing", aswf_version="2024.123"
         )
 
+    @patch.object(builder.sys, "platform", "darwin")
+    def test_bake_dict_sets_linux_amd64_platform_on_macos(self):
+        """Match CI arch on Docker Desktop (Apple Silicon defaults to linux/arm64)."""
+        b = builder.Builder(
+            self.build_info,
+            groupinfo.GroupInfo(
+                names=["base"],
+                versions=["2019"],
+                type_=constants.ImageType.IMAGE,
+                targets=[],
+            ),
+        )
+        baked = b.make_bake_dict(False, False)
+        self.assertEqual(
+            baked["target"]["ci-base-2019"]["platforms"],
+            ["linux/amd64"],
+        )
+
+    def test_bake_dict_omits_platforms_when_not_darwin(self):
+        b = builder.Builder(
+            self.build_info,
+            groupinfo.GroupInfo(
+                names=["base"],
+                versions=["2019"],
+                type_=constants.ImageType.IMAGE,
+                targets=[],
+            ),
+        )
+        for plat in ("linux", "win32"):
+            with patch.object(builder.sys, "platform", plat):
+                baked = b.make_bake_dict(False, False)
+            self.assertNotIn(
+                "platforms",
+                baked["target"]["ci-base-2019"],
+                msg=f"host sys.platform={plat!r}",
+            )
+
     def test_package_opentimelineio_2019_dict(self):
         b = builder.Builder(
             self.build_info,
@@ -82,6 +120,7 @@ def test_image_base_2019_dict(self):
             baked["target"]["ci-base-2019"]["args"]["ASWF_VERSION"], base_version
         )
 
+    @patch.object(builder.sys, "platform", "linux")
     def test_image_base_2019clang_dict(self):
         b = builder.Builder(
             self.build_info,
@@ -174,6 +213,7 @@ def test_image_base_2019clang_dict(self):
             },
         )
 
+    @patch.object(builder.sys, "platform", "linux")
     def test_image_base_2019_2020_dict(self):
         b = builder.Builder(
             self.build_info,