diff --git a/.authors.yml b/.authors.yml
index 69eb66f0e2..1f569a8379 100644
--- a/.authors.yml
+++ b/.authors.yml
@@ -1226,7 +1226,7 @@
   first_commit: 2020-11-19 10:46:41
 - name: Jannis Leidel
   email: jannis@leidel.info
-  num_commits: 39
+  num_commits: 41
   github: jezdez
   first_commit: 2020-11-19 10:46:41
 - name: Christof Kaufmann
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index c7645edbee..23d30d6380 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -104,6 +104,40 @@ jobs:
       PYTEST_MARKER: ${{ matrix.test-type == 'serial' && 'serial' || 'not serial' }}
 
     steps:
+      - name: Free Disk Space
+        uses: endersonmenezes/free-disk-space@6c4664f43348c8c7011b53488d5ca65e9fc5cd1a  # v3.0.0
+        with:
+          remove_android: true
+          remove_dotnet: true
+          remove_haskell: true
+          remove_tool_cache: true
+          remove_swap: true
+          remove_packages: >-
+            azure-cli
+            google-cloud-cli
+            microsoft-edge-stable
+            google-chrome-stable
+            firefox
+            postgresql*
+            temurin-*
+            *llvm*
+            mysql*
+            dotnet-sdk-*
+          remove_packages_one_command: true
+          remove_folders: >-
+            /usr/share/swift
+            /usr/share/az*
+            /usr/local/lib/node_modules
+            /usr/local/share/chromium
+            /usr/local/share/powershell
+            /usr/local/julia
+            /usr/local/aws-cli
+            /usr/local/aws-sam-cli
+            /usr/share/gradle
+          rm_cmd: rmz
+          rmz_version: 3.1.1
+          testing: false
+
       - name: Checkout Source
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
         with:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c2e7fc51e0..b9f4874975 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,11 +1,27 @@
 [//]: # (current developments)
 
+## 25.11.1 (2025-12-04)
+
+### Bug fixes
+
+* Prevent empty channel lists from being passed to host environment creation. (#5857)
+
+### Deprecations
+
+* Remove fallback imports for `conda.core.index.Index`. (#5857)
+
+### Contributors
+
+* @jezdez
+
+
+
 ## 25.11.0 (2025-11-20)
 
 ### Enhancements
 
 * Allow the PyYAML loader to be specified when calling `conda_build.variants.parse_config_file`. (#5800)
-* Raise `menuinst` JSON validation errors, which used to be warnings. (#5807)
+* Raise `menuinst` JSON validation errors, which used to be warnings. (#5828)
 
 ### Bug fixes
 
diff --git a/conda_build/environ.py b/conda_build/environ.py
index af9e6ce6d1..0335cca521 100644
--- a/conda_build/environ.py
+++ b/conda_build/environ.py
@@ -25,7 +25,6 @@
 )
 from conda.base.context import context, reset_context
 from conda.common.io import env_vars
-from conda.core.index import LAST_CHANNEL_URLS
 from conda.core.link import PrefixSetup, UnlinkLinkTransaction
 from conda.core.package_cache_data import PackageCacheData, ProgressiveFetchExtract
 from conda.core.prefix_data import PrefixData
@@ -38,7 +37,7 @@
     UnsatisfiableError,
 )
 from conda.gateways.disk.create import TemporaryDirectory
-from conda.models.channel import Channel, prioritize_channels
+from conda.models.channel import Channel
 from conda.models.match_spec import MatchSpec
 from conda.models.records import PackageRecord
 
@@ -62,6 +61,8 @@
     from pathlib import Path
     from typing import Any, TypedDict
 
+    from conda.core.index import Index
+
     from .config import Config
     from .metadata import MetaData
 
@@ -1262,7 +1263,7 @@ def get_pinned_deps(m, section):
 #       checks for this name in the call stack explicitly.
 def install_actions(
     prefix: str | os.PathLike | Path,
-    index,
+    index: Index,
     specs: Iterable[str | MatchSpec],
     subdir: str | None = None,
 ) -> InstallActionsType:
@@ -1280,25 +1281,8 @@ def install_actions(
         },
         callback=reset_context,
     ):
-        # a hack since in conda-build we don't track channel_priority_map
-        channels: tuple[Channel, ...] | None
-        subdirs: tuple[str, ...] | None
-        if LAST_CHANNEL_URLS:
-            channel_priority_map = prioritize_channels(LAST_CHANNEL_URLS)
-            # tuple(dict.fromkeys(...)) removes duplicates while preserving input order.
-            channels = tuple(
-                dict.fromkeys(Channel(url) for url in channel_priority_map)
-            )
-            subdirs = (
-                tuple(
-                    dict.fromkeys(
-                        subdir for channel in channels if (subdir := channel.subdir)
-                    )
-                )
-                or context.subdirs
-            )
-        else:
-            channels = subdirs = None
+        channels: tuple[Channel, ...] | None = tuple(index.expanded_channels) or None
+        subdirs: tuple[str, ...] | None = tuple(index._subdirs) or None
 
         mspecs = tuple(MatchSpec(spec) for spec in specs)
 
diff --git a/conda_build/index.py b/conda_build/index.py
index be9e1721f9..940ab50a17 100644
--- a/conda_build/index.py
+++ b/conda_build/index.py
@@ -6,9 +6,9 @@
 import os
 from functools import partial
 from os.path import dirname
-from typing import TYPE_CHECKING
 
 from conda.base.context import context
+from conda.core.index import Index
 from conda.exceptions import CondaHTTPError
 from conda.utils import url_path
 
@@ -17,9 +17,6 @@
     get_logger,
 )
 
-if TYPE_CHECKING:
-    from conda.models.channels import Channel
-
 try:
     from conda_index.index import update_index as _update_index
 except ImportError:
@@ -28,16 +25,6 @@
     )
 
 
-try:
-    from conda.core.index import Index
-except ImportError:
-    # FUTURE: remove for `conda >=24.9`
-    from conda.core.index import get_index
-
-    def Index(channels: tuple[str | Channel, ...] = (), *args, **kwargs) -> dict:  # type: ignore[no-redef]
-        return get_index(channel_urls=channels, *args, **kwargs)
-
-
 log = get_logger(__name__)
 
 
diff --git a/conda_build/inspect_pkg.py b/conda_build/inspect_pkg.py
index fcc54c8db0..fb30c590f6 100644
--- a/conda_build/inspect_pkg.py
+++ b/conda_build/inspect_pkg.py
@@ -16,6 +16,7 @@
 from conda.api import Solver
 from conda.base.context import context
 from conda.cli.common import specs_from_args
+from conda.core.index import Index
 from conda.core.prefix_data import PrefixData
 from conda.models.records import PrefixRecord
 
@@ -37,12 +38,6 @@
     package_has_file,
 )
 
-try:
-    from conda.core.index import Index
-except ImportError:
-    # FUTURE: remove for `conda >=24.9`
-    from conda_build.index import Index
-
 if TYPE_CHECKING:
     from collections.abc import Iterable
     from typing import Literal
diff --git a/conda_build/skeletons/cpan.py b/conda_build/skeletons/cpan.py
index f5ddcd82a5..4727f4fcf5 100644
--- a/conda_build/skeletons/cpan.py
+++ b/conda_build/skeletons/cpan.py
@@ -21,6 +21,7 @@
 from os.path import basename, dirname, exists, join
 
 import requests
+from conda.core.index import Index
 from conda.exceptions import CondaError, CondaHTTPError
 from conda.gateways.connection.download import TmpDownload, download
 from conda.gateways.disk.create import TemporaryDirectory
@@ -33,12 +34,6 @@
 from ..variants import get_default_variant
 from ..version import _parse as parse_version
 
-try:
-    from conda.core.index import Index
-except ImportError:
-    # FUTURE: remove for `conda >=24.9`
-    from conda_build.index import Index
-
 CPAN_META = """\
 {{% set name = "{packagename}" %}}
 {{% set version = "{version}" %}}