diff --git a/CHANGELOG.md b/CHANGELOG.md
index cc59e387ee..85a6be5f8a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -129,6 +129,9 @@ END_UNRELEASED_TEMPLATE
   * {obj}`//python:features.bzl%features.headers_abi3` can be used to
     feature-detect the presense of the above.
 * (toolchains) Local toolchains can use a label for the interpreter to use.
+* (pypi) Support for environment marker and `experimental_index_url` handling for
+  Windows ARM64
+  ([#2276](https://github.com/bazel-contrib/rules_python/issues/2276)).
 
 {#v1-6-3}
 ## [1.6.3] - 2025-09-21
diff --git a/MODULE.bazel b/MODULE.bazel
index 481e13e39f..20d40dadac 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -163,6 +163,7 @@ pip = use_extension("//python/extensions:pip.bzl", "pip")
         whl_platform_tags = whl_platform_tags,
     )
     for cpu, whl_platform_tags in {
+        "aarch64": ["win_arm64"],
         "x86_64": ["win_amd64"],
     }.items()
     for freethreaded in [
diff --git a/examples/bzlmod/MODULE.bazel b/examples/bzlmod/MODULE.bazel
index 95e1090f53..1c01a5048a 100644
--- a/examples/bzlmod/MODULE.bazel
+++ b/examples/bzlmod/MODULE.bazel
@@ -172,7 +172,7 @@ pip.default(
     os_name = "windows",
     platform = "windows_aarch64",
     whl_abi_tags = [],  # default to all ABIs
-    whl_platform_tags = ["win_amd64"],
+    whl_platform_tags = ["win_arm64"],
 )
 
 # To fetch pip dependencies, use pip.parse. We can pass in various options,
diff --git a/python/private/pypi/pip_repository.bzl b/python/private/pypi/pip_repository.bzl
index e9a4c44da3..01d0178d0c 100644
--- a/python/private/pypi/pip_repository.bzl
+++ b/python/private/pypi/pip_repository.bzl
@@ -92,16 +92,6 @@ def _pip_repository_impl(rctx):
             requirements_osx = rctx.attr.requirements_darwin,
             requirements_windows = rctx.attr.requirements_windows,
             extra_pip_args = rctx.attr.extra_pip_args,
-            platforms = [
-                "linux_aarch64",
-                "linux_arm",
-                "linux_ppc",
-                "linux_s390x",
-                "linux_x86_64",
-                "osx_aarch64",
-                "osx_x86_64",
-                "windows_x86_64",
-            ],
         ),
         extra_pip_args = rctx.attr.extra_pip_args,
         evaluate_markers = lambda rctx, requirements: evaluate_markers_py(
diff --git a/python/private/pypi/requirements_files_by_platform.bzl b/python/private/pypi/requirements_files_by_platform.bzl
index 356bd4416e..7cfdf8cdd8 100644
--- a/python/private/pypi/requirements_files_by_platform.bzl
+++ b/python/private/pypi/requirements_files_by_platform.bzl
@@ -96,7 +96,17 @@ def requirements_files_by_platform(
         requirements_linux = None,
         requirements_lock = None,
         requirements_windows = None,
-        platforms,
+        platforms = [],
+        default_platforms = [
+            "linux_aarch64",
+            "linux_arm",
+            "linux_ppc",
+            "linux_s390x",
+            "linux_x86_64",
+            "osx_aarch64",
+            "osx_x86_64",
+            "windows_x86_64",
+        ],
         extra_pip_args = None,
         python_version = None,
         logger = None,
@@ -117,6 +127,8 @@ def requirements_files_by_platform(
             specified. It should be of the form "3.x.x",
         platforms: {type}`list[str]` the list of human-friendly platform labels that should
             be used for the evaluation.
+        default_platforms: {type}`list[str]` the list of human-friendly platform labels
+            that will be used for wildcard evaluation.
         logger: repo_utils.logger or None, a simple struct to log diagnostic messages.
         fail_fn (Callable[[str], None]): A failure function used in testing failure cases.
 
@@ -142,7 +154,10 @@ def requirements_files_by_platform(
     if logger:
         logger.debug(lambda: "Platforms from pip args: {}".format(platforms_from_args))
 
-    default_platforms = platforms
+    default_platforms = [_platform(p, python_version) for p in default_platforms]
+    platforms = platforms or default_platforms
+    platforms = [_platform(p, python_version) for p in platforms]
+    default_platforms = [p for p in default_platforms if p in platforms]
 
     if platforms_from_args:
         lock_files = [
diff --git a/tests/pypi/hub_builder/hub_builder_tests.bzl b/tests/pypi/hub_builder/hub_builder_tests.bzl
index ee6200a70a..a59e73e042 100644
--- a/tests/pypi/hub_builder/hub_builder_tests.bzl
+++ b/tests/pypi/hub_builder/hub_builder_tests.bzl
@@ -332,7 +332,9 @@ torch==2.4.1 ; platform_machine != 'x86_64' \
         _parse(
             hub_name = "pypi",
             python_version = "3.15",
-            requirements_lock = "universal.txt",
+            requirements_by_platform = {
+                "universal.txt": "linux_aarch64,osx_aarch64,windows_aarch64,linux_x86_64,linux_x86_64_freethreaded",
+            },
         ),
     )
     pypi = builder.build()
@@ -723,7 +725,9 @@ git_dep @ git+https://git.server/repo/project@deadbeefdeadbeef
         _parse(
             hub_name = "pypi",
             python_version = "3.15",
-            requirements_lock = "requirements.txt",
+            requirements_by_platform = {
+                "requirements.txt": "linux_aarch64,linux_x86_64,linux_x86_64_freethreaded,osx_aarch64,windows_aarch64",
+            },
             experimental_index_url = "pypi.org",
             extra_pip_args = [
                 "--extra-args-for-sdist-building",
@@ -938,18 +942,16 @@ optimum[onnxruntime-gpu]==1.17.1 ; sys_platform == 'linux'
     )
     pypi = builder.build()
 
-    # FIXME @aignas 2025-09-07: we should expose the `optimum` package
-    pypi.exposed_packages().contains_exactly([])
+    pypi.exposed_packages().contains_exactly(["optimum"])
     pypi.group_map().contains_exactly({})
     pypi.whl_map().contains_exactly({
         "optimum": {
-            "pypi_315_optimum_linux_aarch64_linux_x86_64_linux_x86_64_freethreaded": [
+            "pypi_315_optimum_linux_aarch64_linux_x86_64": [
                 whl_config_setting(
                     version = "3.15",
                     target_platforms = [
                         "cp315_linux_aarch64",
                         "cp315_linux_x86_64",
-                        "cp315_linux_x86_64_freethreaded",
                     ],
                 ),
             ],
@@ -964,7 +966,7 @@ optimum[onnxruntime-gpu]==1.17.1 ; sys_platform == 'linux'
         },
     })
     pypi.whl_libraries().contains_exactly({
-        "pypi_315_optimum_linux_aarch64_linux_x86_64_linux_x86_64_freethreaded": {
+        "pypi_315_optimum_linux_aarch64_linux_x86_64": {
             "config_load": "@pypi//:config.bzl",
             "dep_template": "@pypi//{name}:{target}",
             "python_interpreter_target": "unit_test_interpreter_target",
@@ -1019,7 +1021,9 @@ optimum[onnxruntime-gpu]==1.17.1 ; sys_platform == 'linux'
         _parse(
             hub_name = "pypi",
             python_version = "3.15",
-            requirements_lock = "universal.txt",
+            requirements_by_platform = {
+                "universal.txt": "mylinuxx86_64,myosxaarch64",
+            },
         ),
     )
     pypi = builder.build()
diff --git a/tests/pypi/requirements_files_by_platform/requirements_files_by_platform_tests.bzl b/tests/pypi/requirements_files_by_platform/requirements_files_by_platform_tests.bzl
index 6688d72ffe..bff2eca983 100644
--- a/tests/pypi/requirements_files_by_platform/requirements_files_by_platform_tests.bzl
+++ b/tests/pypi/requirements_files_by_platform/requirements_files_by_platform_tests.bzl
@@ -103,6 +103,33 @@ def _test_simple(env):
 
 _tests.append(_test_simple)
 
+def _test_simple_default_platforms(env):
+    default_platforms = [
+        "linux_aarch64",
+        "linux_x86_64",
+        "osx_aarch64",
+        "windows_x86_64",
+    ]
+    for got in [
+        requirements_files_by_platform(
+            requirements_lock = "requirements_lock",
+            default_platforms = default_platforms,
+            platforms = [],
+        ),
+        requirements_files_by_platform(
+            requirements_by_platform = {
+                "requirements_lock": "*",
+            },
+            default_platforms = default_platforms,
+            platforms = [],
+        ),
+    ]:
+        env.expect.that_dict(got).contains_exactly({
+            "requirements_lock": default_platforms,
+        })
+
+_tests.append(_test_simple_default_platforms)
+
 def _test_simple_limited(env):
     for got in [
         requirements_files_by_platform(