TrapsterDK · Nov 9, 2026 · Nov 9, 2026 · Nov 9, 2026 · Nov 9, 2026 · Nov 9, 2026
diff --git a/appimage/README.md b/appimage/README.md
@@ -101,6 +101,9 @@ Build for arm64 from any Linux host:
 bazel build //pkg:app --platforms=//appimage/platforms:linux_arm64
 ```
 
+Or set `platform = "//appimage/platforms:linux_arm64"` on the target. Unset uses the
+current target platform.
+
 The image is packaged from the arm64 target bytes. Running it needs an arm64
 Linux host.
 

diff --git a/appimage/defs.bzl b/appimage/defs.bzl
@@ -1,7 +1,8 @@
 """Linux AppImage packaging for target binaries."""
 
 load("//appimage:pins.bzl", "MKSQUASHFS_VERSION", "RUNTIME_VERSION", "TOOL_VERSION")
-load("//libs/starlark:packaging.bzl", "claim_dest", "data_path", "platform_arch")
+load("//libs/starlark:packaging.bzl", "claim_dest", "data_path")
+load("//libs/starlark:platform.bzl", "PLATFORM_ATTRS", "platform_identity", "platform_transition")
 load(":validate.bzl", "appimage_name_errors")
 
 AppImageInfo = provider(
@@ -25,11 +26,8 @@ def _add(ctx, args, inputs, seen, kind, dest, arg, file):
     inputs.append(file)
 
 def _appimage_impl(ctx):
-    cv = platform_common.ConstraintValueInfo
-    arch = platform_arch(ctx.target_platform_has_constraint, ctx.attr._linux[cv], [
-        ("aarch64", ctx.attr._arm64[cv]),
-        ("x86_64", ctx.attr._x86_64[cv]),
-    ])
+    identity = platform_identity(ctx)
+    arch = identity.cpu if identity.os == "linux" else ""
     if not arch:
         fail("appimage_package " + str(ctx.label) + ": target cell this platform is unsupported: only linux_x86_64 and linux_arm64 are pinned")
     name = ctx.attr.app_name or ctx.label.name
@@ -102,14 +100,12 @@ _appimage_package = rule(
         "libs": attr.label_list(doc = "Shared libraries placed under usr/lib.", allow_files = True),
         "notice": attr.label_list(doc = "License and NOTICE files placed under usr/share/licenses/<name>.", allow_files = True, mandatory = True, allow_empty = False),
         "version": attr.string(doc = "Application version.", mandatory = True),
-        "_arm64": attr.label(default = "@platforms//cpu:arm64"),
         "_build": attr.label(default = "//appimage/packer:appimage_packer", executable = True, cfg = "exec"),
-        "_linux": attr.label(default = "@platforms//os:linux"),
         "_runtime_aarch64": attr.label(default = "@dx_appimage_tools//:runtime_aarch64", allow_single_file = True),
         "_runtime_x86_64": attr.label(default = "@dx_appimage_tools//:runtime_x86_64", allow_single_file = True),
         "_tools": attr.label(doc = "The appimagetool closure.", cfg = "exec", default = "@dx_appimage_tools//:tools"),
-        "_x86_64": attr.label(default = "@platforms//cpu:x86_64"),
-    },
+    } | PLATFORM_ATTRS,
+    cfg = platform_transition,
 )
 
 def appimage_package(name, target_compatible_with = [], **kwargs):

diff --git a/docs/cli/commands/generate.md b/docs/cli/commands/generate.md
@@ -76,7 +76,7 @@ Set directives as `# gazelle:<name> <value>` comments in a `BUILD` file. They ap
 | `dx_external <ecosystem> <path\|off> [<repo>]` | Name the manifest or lockfile that third-party imports resolve through. |
 | `dx_rust_corpus true\|false` | Turn the Rust corpus targets on or off. |
 | `dx_rust_crates_hub <repo>` | Load `aliases` and `all_crate_deps` for Cargo packages from the crate_universe hub `@<repo>` instead of `@crates`. The package needs a `BUILD` file. |
-| `dx_cuda_platforms <spec> <spec>...` | Set `platforms` of a generated `cuda_library`. Required for `.cu` and `.cuh` files. |
+| `dx_cuda_archs <spec> <spec>...` | Set `cuda_archs` of a generated `cuda_library`. Required for `.cu` and `.cuh` files. |
 | `dx_fixture_testonly true\|false` | Mark generated libraries under a `tests/`, `fixtures/` or `testdata/` directory `testonly`. Off by default. Inherited by child packages. |
 | `lang <languages>` | Must list `dx_dispatch`, for example `go,dx_dispatch`. |
 

diff --git a/families/android/README.md b/families/android/README.md
@@ -123,7 +123,8 @@ rust_android_apk(
 The package links one `lib/<abi>/lib<name>_bin.so` per ABI from the
 static native deps and signs the APK with the debug key. Builds never
 use a release key. Build `:app_apk` for the installable `app_apk.apk`;
-it selects the platforms named in `platforms`, and an unknown ABI fails. The
+it builds for the platform labels in `platforms`, `//platforms:arm64-v8a` and
+`//platforms:x86_64` by default, and any other label fails. Do not set it with `select()`. The
 native deps need `alwayslink = True` so `ANativeActivity_onCreate` stays
 exported, and `-landroid -llog` as link options when they use the NDK
 APIs. The default manifest launches a `NativeActivity` loading that
@@ -226,15 +227,15 @@ load("@rules_dx_android//packaging:defs.bzl", "android_check")
 android_check(
     name = "aab_check",
     package = ":app_apk_aab_file",
-    platforms = ["arm64-v8a", "x86_64"],
+    platforms = ["@rules_dx_android//platforms:arm64-v8a", "@rules_dx_android//platforms:x86_64"],
     resources = ["string/app_name"],
 )
 ```
 
 | Attribute | Default | Meaning |
 | --- | --- | --- |
 | `package` | required | The `.apk` or `.aab` to check. |
-| `platforms` | `[]` | ABIs that must ship a `base/lib/<abi>/*.so`. App Bundles only. |
+| `platforms` | `[]` | Platform labels whose ABI must ship a `base/lib/<abi>/*.so`. App Bundles only. |
 | `resources` | `[]` | `type/name` resources the bundle must resolve. App Bundles only. |
 | `size`, `tags`, `visibility` | `"small"`, none, none | Passed to the test. |
 

diff --git a/families/android/packaging/BUILD.bazel b/families/android/packaging/BUILD.bazel
@@ -76,19 +76,19 @@ failure_test(
 rust_android_apk(
     name = "bad_abi",
     app_id = "com.example.app",
-    platforms = ["mips"],
+    platforms = ["//platforms:mips"],
     deps = [],
 )
 
 failure_test(
     name = "bad_abi_test",
-    expected_failure_substring = "abi 'mips' is unknown",
+    expected_failure_substring = "//platforms:mips' is unknown",
     target = ":bad_abi",
 )
 
 failure_test(
     name = "bad_abi_aab_file_test",
-    expected_failure_substring = "abi 'mips' is unknown",
+    expected_failure_substring = "//platforms:mips' is unknown",
     target = ":bad_abi_aab_file",
 )
 
@@ -129,8 +129,8 @@ rust_android_apk(
     name = "bad_dup_abis",
     app_id = "com.example.app",
     platforms = [
-        "x86_64",
-        "x86_64",
+        "//platforms:x86_64",
+        "//platforms:x86_64",
     ],
     deps = [],
 )
@@ -246,13 +246,13 @@ failure_test(
 android_check(
     name = "bad_abi_aab_check",
     package = "//tests/fixtures/rust_apk:dummy.apk",
-    platforms = ["mips"],
+    platforms = ["//platforms:mips"],
     tags = ["manual"],
 )
 
 failure_test(
     name = "bad_abi_aab_check_test",
-    expected_failure_substring = "abi 'mips' is unknown",
+    expected_failure_substring = "//platforms:mips' is unknown",
     target = ":bad_abi_aab_check_selection",
 )
 

diff --git a/families/android/packaging/defs.bzl b/families/android/packaging/defs.bzl
@@ -9,7 +9,7 @@ load("@rules_shell//shell:sh_binary.bzl", "sh_binary")
 load("@rules_shell//shell:sh_test.bzl", "sh_test")
 load("//platforms:defs.bzl", "api_floor")
 load("//sdk:repos.bzl", "BUILD_TOOLS", "SDK_PLATFORM")
-load(":repos.bzl", "abi_errors", "abi_platforms", "app_id_errors", "manifest_lib_name")
+load(":repos.bzl", "ABI_PLATFORMS", "abi_errors", "abi_platforms", "app_id_errors", "manifest_lib_name")
 load(":validate.bzl", "android_aab_check_errors", "android_apk_manifest_errors", "android_apk_set_errors", "android_release_sign_errors", "rust_android_apk_errors")
 
 _TARGET_SDK = SDK_PLATFORM.removeprefix("android-")
@@ -141,11 +141,19 @@ _apk_manifest = rule(
     outputs = {"manifest": "%{name}.xml"},
 )
 
+def abis_for_platforms(platforms):
+    """Returns the ABI name of each platform label; an unknown label stays as its text for abi_errors."""
+    if type(platforms) != "list":
+        return platforms
+    by_label = {label: abi for abi, label in ABI_PLATFORMS.items()}
+    labels = [str(native.package_relative_label(platform)) for platform in platforms]
+    return [by_label.get(label, label) for label in labels]
+
 def rust_android_apk(
         name,
         app_id,
         deps,
-        platforms = ["arm64-v8a", "x86_64"],
+        platforms = [Label("//platforms:arm64-v8a"), Label("//platforms:x86_64")],
         activity = "android.app.NativeActivity",
         api_level = 0,
         assets = [],
@@ -161,11 +169,12 @@ def rust_android_apk(
         **kwargs):
     """Packages one APK and one unsigned App Bundle from native CcInfo deps with a Rust entry point."""
     inner = ":" + name + "_bin"
+    abis = abis_for_platforms(platforms)
     package = custom_package if custom_package != "" else app_id
     effective_api = api_level if api_level != 0 else api_floor()
     _apk_validation(
         name = name + "_validation",
-        abis = platforms,
+        abis = abis,
         api_level = api_level,
         apk_name = name,
         app_id = app_id,
@@ -200,8 +209,8 @@ def rust_android_apk(
         tags = ["manual"],
         visibility = visibility,
     )
-    plain = not _has_select([platforms, app_id, api_level, version_code])
-    invalid = plain and len(rust_android_apk_errors(name, app_id, platforms, api_level, version_code)) > 0
+    plain = not _has_select([abis, app_id, api_level, version_code])
+    invalid = plain and len(rust_android_apk_errors(name, app_id, abis, api_level, version_code)) > 0
     android_application(
         name = name + "_bundle",
         base_module = inner,
@@ -212,7 +221,7 @@ def rust_android_apk(
     )
     _aab_file(
         name = name + "_aab_file",
-        abis = platforms,
+        abis = abis,
         src = None if invalid else ":" + name + "_bundle",
         validation = ":" + name + "_validation",
         tags = ["manual"],
@@ -233,7 +242,7 @@ def rust_android_apk(
     )
     _rust_android_apk(
         name = name,
-        abis = platforms,
+        abis = abis,
         binary = None if invalid else inner,
         testonly = testonly,
         validation = ":" + name + "_validation",
@@ -640,17 +649,18 @@ _check_selection = rule(
 
 def android_check(name, package, platforms = [], resources = [], size = "small", tags = None, target_compatible_with = None, visibility = None):
     """Declares a test that the package is an unsigned APK or a valid App Bundle."""
+    abis = abis_for_platforms(platforms)
     _check_selection(
         name = name + "_selection",
         package = package,
-        abis = platforms,
+        abis = abis,
         resources = resources,
         tags = ["manual"],
         target_compatible_with = target_compatible_with,
         visibility = ["//visibility:private"],
     )
     args = ["$(rootpath " + str(_BUNDLETOOL) + ")", "$(rootpath " + package + ")"]
-    for abi in platforms:
+    for abi in abis:
         args.extend(["--abi", abi])
     for resource in resources:
         args.extend(["--resource", resource])

diff --git a/families/android/tests/fixtures/consumer_android/BUILD.bazel b/families/android/tests/fixtures/consumer_android/BUILD.bazel
@@ -36,8 +36,8 @@ cc_library(
 rust_android_apk(
     name = "consumer_android_apk",
     platforms = [
-        "arm64-v8a",
-        "x86_64",
+        "@rules_dx_android//platforms:arm64-v8a",
+        "@rules_dx_android//platforms:x86_64",
     ],
     api_level = 31,
     app_id = "com.example.consumer_android",

diff --git a/families/android/tests/fixtures/rust_apk/BUILD.bazel b/families/android/tests/fixtures/rust_apk/BUILD.bazel
@@ -56,7 +56,7 @@ rust_android_apk(
     assets = glob(["assets/**"]),
     assets_dir = "assets",
     permissions = ["android.permission.INTERNET"],
-    platforms = ["arm64-v8a"],
+    platforms = ["//platforms:arm64-v8a"],
     resource_files = glob(["res/**"]),
     deps = [":app_jni"],
 )
@@ -96,7 +96,7 @@ genrule(
 android_check(
     name = "check_test_bundle_test",
     package = ":test_bundle.aab",
-    platforms = ["x86_64"],
+    platforms = ["//platforms:x86_64"],
 )
 
 android_apk_set(
@@ -149,7 +149,7 @@ rust_android_apk(
         "android.permission.ACCESS_NETWORK_STATE",
         "android.permission.VIBRATE",
     ],
-    platforms = ["x86_64"],
+    platforms = ["//platforms:x86_64"],
     resource_files = glob(["res/**"]),
     version_code = 7,
     version_name = "2.3",
@@ -248,8 +248,8 @@ android_check(
     name = "check_app_aab_test",
     package = ":app_apk_aab_file",
     platforms = [
-        "arm64-v8a",
-        "x86_64",
+        "//platforms:arm64-v8a",
+        "//platforms:x86_64",
     ],
     resources = ["string/app_name"],
     target_compatible_with = [
@@ -270,8 +270,8 @@ android_check(
     name = "check_app_aab_starlark_flag_test",
     package = ":app_apk_aab_file_x86_64_flag",
     platforms = [
-        "arm64-v8a",
-        "x86_64",
+        "//platforms:arm64-v8a",
+        "//platforms:x86_64",
     ],
     target_compatible_with = [
         "@platforms//os:linux",

diff --git a/families/apple/BUILD.bazel b/families/apple/BUILD.bazel
@@ -15,6 +15,7 @@ filegroup(
         "//bundle:module_srcs",
         "//ios:module_srcs",
         "//macos:module_srcs",
+        "//platforms:module_srcs",
         "//provisioning:module_srcs",
         "//signing:module_srcs",
     ],
@@ -41,12 +42,13 @@ sh_test(
         "//bundle:corpus_starlark",
         "//ios:corpus_starlark",
         "//macos:corpus_starlark",
+        "//platforms:corpus_starlark",
         "//provisioning:corpus_starlark",
         "//signing:corpus_starlark",
         "//tests:corpus_starlark",
         "@rules_dx//tools/ci:starlark_docs_family_test",
     ],
-    env = {"STARLARK_DOCS_PACKAGES": "bundle,ios,macos,provisioning,signing,tests"},
+    env = {"STARLARK_DOCS_PACKAGES": "bundle,ios,macos,platforms,provisioning,signing,tests"},
 )
 
 # dx:begin exports

diff --git a/families/apple/README.md b/families/apple/README.md
@@ -540,7 +540,7 @@ rust_static_library(
 apple_macos_app(
     name = "ledger",
     srcs = ["main.m"],
-    platforms = ["arm64"],
+    platform = "@rules_dx_apple//platforms:macos_arm64",
     bundle_id = "com.example.ledger",
     version = "1.0",
     deployment = "14.0",
@@ -550,6 +550,12 @@ apple_macos_app(
 )
 ```
 
+`platform` is optional and defaults to the current target platform. It names the
+platform the selection and check rules read the arch from; only `macos_arm64` is
+accepted. It does not change the platform the bundle is built for: build with
+`--platforms` or `--macos_cpus`. An x86_64 macOS target platform fails with
+"arch 'x86_64' is outside macos", where the app used to default to arm64.
+
 `srcs` holds the native entry point. `library` is any target with
 `CcInfo` that links one static archive, such as `rust_static_library`.
 The app needs `srcs`, `library`, or both. `frameworks` takes frameworks
@@ -612,7 +618,7 @@ Building signs ad hoc only, whatever `--macos_signing_cert_name` says.
 
 Failures read:
 
-- `apple_macos_app: platforms takes one of arm64`
+- `apple_macos_app: arch 'x86_64' is outside macos: want arm64`
 - `apple_macos_app: deployment '13.0' is below 14.0`
 - `apple_macos_app: plugin '//app:empty' places nothing under PlugIns`
 - `apple_macos_app: deployment '16.0' is above the Xcode 16 'macosx' ceiling 15.0`

diff --git a/families/apple/macos/BUILD.bazel b/families/apple/macos/BUILD.bazel
@@ -117,14 +117,14 @@ apple_macos_app(
     srcs = ["main.m"],
     bundle_id = "com.example.ledger",
     deployment = "14.0",
-    platforms = ["x86_64"],
+    platform = "//platforms:macos_x86_64",
     tags = ["manual"],
     version = "1.0",
 )
 
 failure_test(
     name = "x86_app_test",
-    expected_failure_substring = "apple_macos_app: platforms takes one of arm64",
+    expected_failure_substring = "apple_macos_app: arch 'x86_64' is outside macos: want arm64",
     target = ":x86_app_selection",
 )