@@ -33,30 +33,30 @@ jobs:
         }
       shell: powershell
 
-    #- name: Set up Python 3.14
+    #- name: Set up Python 3.15
     #  uses: actions/setup-python@v5
     #  with:
-    #    python-version: 3.14-dev
+    #    python-version: 3.15-dev
 
     # We move faster than GitHub's Python runtimes, so use NuGet instead
     # One day we can use ourselves to download Python, but not yet...
     - name: Set up NuGet
       uses: nuget/setup-nuget@b26b823c478ee115be5c9403e62c90b0bf943843 # v3.1.0
 
-    - name: Set up Python 3.14.6
+    - name: Set up Python 3.15.0rc1
       run: |
-        nuget install python -Version 3.14.6 -x -o .
+        nuget install python -Version 3.15.0-rc1 -x -o .
         $py = Get-Item python\tools
         Write-Host "Adding $py to PATH"
         "$py" | Out-File $env:GITHUB_PATH -Encoding UTF8 -Append
       working-directory: ${{ runner.temp }}
 
-    - name: Check Python version is 3.14.6
+    - name: Check Python version is 3.15.0rc1
       run: >
         python -c "import sys;
         print(sys.version);
         print(sys.executable);
-        sys.exit(0 if sys.version_info[:5] == (3, 14, 6, 'final', 0) else 1)"
+        sys.exit(0 if sys.version_info[:5] == (3, 15, 0, 'candidate', 1) else 1)"
 
     - name: Install build dependencies
       run: python -m pip install "pymsbuild==1.2.2"
 
@@ -6,7 +6,11 @@
 
 DLL_NAME = "python{0.major}{0.minor}".format(sys.version_info)
 VER_NUM = "{0.major}.{0.minor}.{0.micro}".format(sys.version_info)
-EMBED_URL = f"https://www.python.org/ftp/python/{VER_NUM}/python-{VER_NUM}-embed-amd64.zip"
+if sys.version_info.releaselevel == "candidate":
+    VER_NUM_RC = f"rc{sys.version_info.serial}"
+else:
+    VER_NUM_RC = ""
+EMBED_URL = f"https://www.python.org/ftp/python/{VER_NUM}/python-{VER_NUM}{VER_NUM_RC}-embed-amd64.zip"
 
 def can_embed(tag):
     """Return False if tag doesn't match DLL_NAME and EMBED_URL.
 
@@ -95,19 +95,19 @@ stages:
       displayName: 'Install Nuget'
 
     - powershell: |
-        nuget install python -Version 3.14.6 -x -noninteractive -o host_python
+        nuget install python -Version 3.15.0-rc1 -x -noninteractive -o host_python
         $py = Get-Item host_python\python\tools
         Write-Host "Adding $py to PATH"
         Write-Host "##vso[task.prependpath]$py"
-      displayName: Set up Python 3.14.6
+      displayName: Set up Python 3.15.0rc1
       workingDirectory: $(Build.BinariesDirectory)
 
     - powershell: >
         python -c "import sys;
         print(sys.version);
         print(sys.executable);
-        sys.exit(0 if sys.version_info[:5] == (3, 14, 6, 'final', 0) else 1)"
-      displayName: Check Python version is 3.14.6
+        sys.exit(0 if sys.version_info[:5] == (3, 15, 0, 'candidate', 1) else 1)"
+      displayName: Check Python version is 3.15.0rc1
 
     - powershell: |
         python -m pip install "pymsbuild==1.2.2"
 
@@ -1,3 +1,18 @@
+################################################################################
+# HACK: Work around gh-148750 in 3.15
+# In short, encodings is now partially frozen, which means its submodules can
+# only be loaded if they are also frozen or if they are in their default
+# location relative to the executable. For embedded runtimes, this is not true,
+# so we need to patch the __path__ to point at our expected location.
+# This code is very fragile and should not be reused.
+import sys
+import encodings
+for p in sys.path:
+    if p.endswith(".zip"):
+        encodings.__path__[:] = [f"{p}\\encodings"]
+        break
+################################################################################
+
 from .exceptions import (
     ArgumentError,
     AutomaticInstallDisabledError,
 
@@ -472,10 +472,9 @@ def __init__(self, args, root=None):
 
         if not self.default_platform:
             from _native import get_processor_architecture
-            LOGGER.debug("Get CPU architecture, its prefix is %s", get_processor_architecture())
+            self.default_platform = get_processor_architecture()
+            LOGGER.debug("Default to current CPU architecture: %s", self.default_platform)
 
-            # Currently, we always default to -64.
-            self.default_platform = "-64"
 
         # If our command has any config, load them to override anything that
         # wasn't set on the command line.
 
@@ -413,9 +413,9 @@ def first_run(cmd):
             LOGGER.print("!Y!The global shortcuts directory is not "
                          "configured.!W!", level=logging.WARN)
             LOGGER.print("\nConfiguring this enables commands like "
-                         "!B!python3.14.exe!W! to run from your terminal, "
+                         "!B!python3.15.exe!W! to run from your terminal, "
                          "but is not needed for the !B!python!W! or !B!py!W! "
-                         "commands (for example, !B!py -V:3.14!W!).",
+                         "commands (for example, !B!py -V:3.15!W!).",
                          wrap=True)
             LOGGER.print("\nWe can add the directory (!B!%s!W!) to PATH now, "
                          "but you will need to restart your terminal to use "
 
@@ -20,6 +20,16 @@
 _native.coinitialize()
 
 
+################################################################################
+# HACK: Work around gh-148750 in 3.15
+import encodings
+_orig_encodings_path = encodings.__path__[:]
+import manage
+# Importing manage has changed this value because of our hack
+encodings.__path__[:] = _orig_encodings_path
+################################################################################
+
+
 # Importing in order carefully to ensure the variables we override are handled
 # correctly by submodules.
 import manage