diff --git a/.github/workflows/builddoc.yml b/.github/workflows/builddoc.yml
index b5f82592360..7fa7b96f3f9 100644
--- a/.github/workflows/builddoc.yml
+++ b/.github/workflows/builddoc.yml
@@ -14,6 +14,7 @@ concurrency:
 
 env:
   FORCE_COLOR: "1"
+  UV_SYSTEM_PYTHON: "1"  # make uv do global installs
 
 jobs:
   build:
@@ -27,10 +28,14 @@ jobs:
         python-version: "3"
     - name: Install graphviz
       run: sudo apt-get install graphviz
+    - name: Install uv
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
+        | sh
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install .[docs]
+      run: uv pip install .[docs]
     - name: Render the documentation
       run: >
         sphinx-build
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index e09f17145b0..fd59f7ff119 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -14,6 +14,7 @@ concurrency:
 
 env:
   FORCE_COLOR: "1"
+  UV_SYSTEM_PYTHON: "1"  # make uv do global installs
 
 jobs:
   # If you update any of these commands, don't forget to update the equivalent
@@ -23,17 +24,13 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
-    - name: Set up Python
-      uses: actions/setup-python@v5
-      with:
-        python-version: "3"
-    - name: Install pip
-      run: python -m pip install --upgrade pip
-
     - name: Install Ruff
-      run: |
-          ruff_version=$(awk -F'[="]' '/\[project\.optional-dependencies\]/ {p=1} /ruff/ {if (p) print $4}' pyproject.toml)
-          python -m pip install "ruff==${ruff_version}"
+      run: >
+        RUFF_VERSION=$(awk -F'[="]' '/\[project\.optional-dependencies\]/ {p=1} /ruff/ {if (p) print $4}' pyproject.toml)
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/ruff/${RUFF_VERSION}/install.sh"
+        | sh
 
     - name: Lint with Ruff
       run: ruff check . --output-format github
@@ -50,10 +47,14 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: "3"
+    - name: Install uv
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
+        | sh
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install --upgrade "flake8>=6.0"
+      run: uv pip install --upgrade "flake8>=6.0"
     - name: Lint with flake8
       run: flake8 .
 
@@ -66,10 +67,14 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: "3"
+    - name: Install uv
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
+        | sh
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install ".[lint,test]"
+      run: uv pip install ".[lint,test]"
     - name: Type check with mypy
       run: mypy
 
@@ -82,10 +87,14 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: "3"
+    - name: Install uv
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
+        | sh
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install --upgrade sphinx-lint
+      run: uv pip install --upgrade sphinx-lint
     - name: Lint documentation with sphinx-lint
       run: make doclinter
 
@@ -98,10 +107,14 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: "3"
+    - name: Install uv
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
+        | sh
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install --upgrade twine build
+      run: uv pip install --upgrade twine build
     - name: Lint with twine
       run: |
         python -m build .
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index b4804d01ad0..7d3f5608551 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -36,7 +36,6 @@ jobs:
         - "3.10"
         - "3.11"
         - "3.12"
-        - "3.13-dev"
         docutils:
         - "0.20"
         - "0.21"
@@ -49,12 +48,43 @@ jobs:
     - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python }}
       uses: actions/setup-python@v5
-      if: "!endsWith(matrix.python, '-dev')"
       with:
         python-version: ${{ matrix.python }}
+    - name: Check Python version
+      run: python --version --version
+    - name: Install graphviz
+      run: sudo apt-get install graphviz
+    - name: Install uv
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
+        | sh
+    - name: Install dependencies
+      run: uv pip install .[test]
+    - name: Install Docutils ${{ matrix.docutils }}
+      run: uv pip install --upgrade "docutils~=${{ matrix.docutils }}.0"
+    - name: Test with pytest
+      run: python -m pytest -vv --durations 25
+      env:
+        PYTHONWARNINGS: "error"  # treat all warnings as errors
+
+  deadsnakes:
+    runs-on: ubuntu-latest
+    name: Python ${{ matrix.python }} (Docutils ${{ matrix.docutils }})
+    strategy:
+      fail-fast: false
+      matrix:
+        python:
+        - "3.13-dev"
+        docutils:
+        - "0.20"
+        - "0.21"
+
+    steps:
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python }} (deadsnakes)
       uses: deadsnakes/action@v3.1.0
-      if: "endsWith(matrix.python, '-dev')"
       with:
         python-version: ${{ matrix.python }}
     - name: Check Python version
@@ -84,10 +114,14 @@ jobs:
         python-version: "3"
     - name: Check Python version
       run: python --version --version
+    - name: Install graphviz
+      run: choco install --no-progress graphviz
+    - name: Install uv
+      run: >
+        Invoke-WebRequest -Uri "https://astral.sh/uv/install.ps1"
+        | Invoke-Expression
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install .[test]
+      run: uv pip install .[test]
     - name: Test with pytest
       run: python -m pytest -vv --durations 25
       env:
@@ -100,9 +134,10 @@ jobs:
     steps:
     - name: Install epubcheck
       run: |
+        EPUBCHECK_VERSION="5.1.0"
         mkdir /tmp/epubcheck && cd /tmp/epubcheck
-        wget https://github.com/w3c/epubcheck/releases/download/v5.1.0/epubcheck-5.1.0.zip
-        unzip epubcheck-5.1.0.zip
+        wget --no-verbose https://github.com/w3c/epubcheck/releases/download/v${EPUBCHECK_VERSION}/epubcheck-${EPUBCHECK_VERSION}.zip
+        unzip epubcheck-${EPUBCHECK_VERSION}.zip
     - uses: actions/checkout@v4
     - name: Set up Python
       uses: actions/setup-python@v5
@@ -112,12 +147,16 @@ jobs:
       run: python --version --version
     - name: Install graphviz
       run: sudo apt-get install graphviz
+    - name: Install uv
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
+        | sh
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install .[test]
+      run: uv pip install .[test]
     - name: Install Docutils' HEAD
-      run: python -m pip install git+https://repo.or.cz/docutils.git\#subdirectory=docutils
+      run: uv pip install "docutils @ git+https://repo.or.cz/docutils.git#subdirectory=docutils"
     - name: Test with pytest
       run: python -m pytest -vv
       env:
@@ -140,13 +179,10 @@ jobs:
     - name: Install graphviz
       run: sudo apt-get install graphviz
     - name: Install uv
-      run: > 
-        curl 
-        --location 
-        --fail
-        --proto '=https' --tlsv1.2 
-        --silent --show-error 
-        https://astral.sh/uv/install.sh
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
         | sh
     - name: Install dependencies
       run: |
@@ -171,10 +207,14 @@ jobs:
         python-version: "3"
     - name: Check Python version
       run: python --version --version
+    - name: Install uv
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
+        | sh
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install .[test]
+      run: uv pip install .[test]
     - name: Test with pytest
       run: python -m pytest -vv --durations 25
       env:
@@ -196,10 +236,14 @@ jobs:
       run: python --version --version
     - name: Install graphviz
       run: sudo apt-get install graphviz
+    - name: Install uv
+      run: >
+        curl --no-progress-meter --location --fail
+        --proto '=https' --tlsv1.2
+        "https://astral.sh/uv/install.sh"
+        | sh
     - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        python -m pip install .[test] pytest-cov
+      run: uv pip install .[test] pytest-cov
     - name: Test with pytest
       run: python -m pytest -vv --cov . --cov-append --cov-config pyproject.toml
       env:
diff --git a/CHANGES.rst b/CHANGES.rst
index b7d1a0b6e09..08e2656826e 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -57,6 +57,11 @@ Bugs fixed
 * #12744: Classes injected by a custom interpreted text role now give rise to
   nested ``\DUrole``'s, rather than a single one with comma separated classes.
   Patch by Jean-François B.
+* #11970, #12551: singlehtml builder: make target URIs to be same-document
+  references in the sense of :rfc:`RFC 3986, §4.4 <3986#section-4.4>`,
+  e.g., ``index.html#foo`` becomes ``#foo``.
+  (note: continuation of a partial fix added in Sphinx 7.3.0)
+  Patch by James Addison (with reference to prior work by Eric Norige)
 
 Testing
 -------
diff --git a/sphinx/builders/_epub_base.py b/sphinx/builders/_epub_base.py
index 444e9812ddd..15c4bd80b52 100644
--- a/sphinx/builders/_epub_base.py
+++ b/sphinx/builders/_epub_base.py
@@ -15,7 +15,8 @@
 from docutils.utils import smartquotes
 
 from sphinx import addnodes
-from sphinx.builders.html import BuildInfo, StandaloneHTMLBuilder
+from sphinx.builders.html import StandaloneHTMLBuilder
+from sphinx.builders.html._build_info import BuildInfo
 from sphinx.locale import __
 from sphinx.util import logging
 from sphinx.util.display import status_iterator
diff --git a/sphinx/builders/html/__init__.py b/sphinx/builders/html/__init__.py
index 2fa5f360a95..e6453bea7c3 100644
--- a/sphinx/builders/html/__init__.py
+++ b/sphinx/builders/html/__init__.py
@@ -3,17 +3,16 @@
 from __future__ import annotations
 
 import contextlib
-import hashlib
 import html
 import os
 import posixpath
 import re
+import shutil
 import sys
-import types
 import warnings
 from os import path
 from pathlib import Path
-from typing import IO, TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any
 from urllib.parse import quote
 
 import docutils.readers.doctree
@@ -31,6 +30,7 @@
     _file_checksum,
     _JavaScript,
 )
+from sphinx.builders.html._build_info import BuildInfo
 from sphinx.config import ENUM, Config
 from sphinx.deprecation import _deprecation_warning
 from sphinx.domains import Domain, Index, IndexEntry
@@ -63,16 +63,14 @@
 from sphinx.writers.html5 import HTML5Translator
 
 if TYPE_CHECKING:
-    from collections.abc import Iterable, Iterator, Set
+    from collections.abc import Iterable, Iterator
     from typing import TypeAlias
 
     from docutils.nodes import Node
     from docutils.readers import Reader
 
     from sphinx.application import Sphinx
-    from sphinx.config import _ConfigRebuild
     from sphinx.environment import BuildEnvironment
-    from sphinx.util.tags import Tags
     from sphinx.util.typing import ExtensionMetadata
 
 #: the filename for the inventory of objects
@@ -93,23 +91,6 @@
 ]
 
 
-def _stable_hash(obj: Any) -> str:
-    """Return a stable hash for a Python data structure.
-
-    We can't just use the md5 of str(obj) as the order of collections
-    may be random.
-    """
-    if isinstance(obj, dict):
-        obj = sorted(map(_stable_hash, obj.items()))
-    if isinstance(obj, list | tuple | set | frozenset):
-        obj = sorted(map(_stable_hash, obj))
-    elif isinstance(obj, type | types.FunctionType):
-        # The default repr() of functions includes the ID, which is not ideal.
-        # We use the fully qualified name instead.
-        obj = f'{obj.__module__}.{obj.__qualname__}'
-    return hashlib.md5(str(obj).encode(), usedforsecurity=False).hexdigest()
-
-
 def convert_locale_to_language_tag(locale: str | None) -> str | None:
     """Convert a locale string to a language tag (ex. en_US -> en-US).
 
@@ -121,57 +102,6 @@ def convert_locale_to_language_tag(locale: str | None) -> str | None:
         return None
 
 
-class BuildInfo:
-    """buildinfo file manipulator.
-
-    HTMLBuilder and its family are storing their own envdata to ``.buildinfo``.
-    This class is a manipulator for the file.
-    """
-
-    @classmethod
-    def load(cls: type[BuildInfo], f: IO[str]) -> BuildInfo:
-        try:
-            lines = f.readlines()
-            assert lines[0].rstrip() == '# Sphinx build info version 1'
-            assert lines[2].startswith('config: ')
-            assert lines[3].startswith('tags: ')
-
-            build_info = BuildInfo()
-            build_info.config_hash = lines[2].split()[1].strip()
-            build_info.tags_hash = lines[3].split()[1].strip()
-            return build_info
-        except Exception as exc:
-            raise ValueError(__('build info file is broken: %r') % exc) from exc
-
-    def __init__(
-        self,
-        config: Config | None = None,
-        tags: Tags | None = None,
-        config_categories: Set[_ConfigRebuild] = frozenset(),
-    ) -> None:
-        self.config_hash = ''
-        self.tags_hash = ''
-
-        if config:
-            values = {c.name: c.value for c in config.filter(config_categories)}
-            self.config_hash = _stable_hash(values)
-
-        if tags:
-            self.tags_hash = _stable_hash(sorted(tags))
-
-    def __eq__(self, other: BuildInfo) -> bool:  # type: ignore[override]
-        return (self.config_hash == other.config_hash and
-                self.tags_hash == other.tags_hash)
-
-    def dump(self, f: IO[str]) -> None:
-        f.write('# Sphinx build info version 1\n'
-                '# This file hashes the configuration used when building these files.'
-                ' When it is not found, a full rebuild will be done.\n'
-                'config: %s\n'
-                'tags: %s\n' %
-                (self.config_hash, self.tags_hash))
-
-
 class StandaloneHTMLBuilder(Builder):
     """
     Builds standalone HTML docs.
@@ -396,18 +326,28 @@ def math_renderer_name(self) -> str | None:
     def get_outdated_docs(self) -> Iterator[str]:
         build_info_fname = self.outdir / '.buildinfo'
         try:
-            with open(build_info_fname, encoding="utf-8") as fp:
-                buildinfo = BuildInfo.load(fp)
-
-            if self.build_info != buildinfo:
-                logger.debug('[build target] did not match: build_info ')
-                yield from self.env.found_docs
-                return
+            build_info = BuildInfo.load(build_info_fname)
         except ValueError as exc:
             logger.warning(__('Failed to read build info file: %r'), exc)
         except OSError:
             # ignore errors on reading
             pass
+        else:
+            if self.build_info != build_info:
+                # log the mismatch and backup the old build info
+                build_info_backup = build_info_fname.with_name('.buildinfo.bak')
+                try:
+                    shutil.move(build_info_fname, build_info_backup)
+                    self.build_info.dump(build_info_fname)
+                except OSError:
+                    pass  # ignore errors
+                else:
+                    # only log on success
+                    msg = __('build_info mismatch, copying .buildinfo to .buildinfo.bak')
+                    logger.info(bold(__('building [html]: ')) + msg)
+
+                yield from self.env.found_docs
+                return
 
         if self.templates:
             template_mtime = int(self.templates.newest_template_mtime() * 10**6)
@@ -943,8 +883,7 @@ def copy_extra_files(self) -> None:
 
     def write_buildinfo(self) -> None:
         try:
-            with open(path.join(self.outdir, '.buildinfo'), 'w', encoding="utf-8") as fp:
-                self.build_info.dump(fp)
+            self.build_info.dump(self.outdir / '.buildinfo')
         except OSError as exc:
             logger.warning(__('Failed to write build info file: %r'), exc)
 
diff --git a/sphinx/builders/html/_build_info.py b/sphinx/builders/html/_build_info.py
new file mode 100644
index 00000000000..5b364c0d9fc
--- /dev/null
+++ b/sphinx/builders/html/_build_info.py
@@ -0,0 +1,94 @@
+"""Record metadata for the build process."""
+
+from __future__ import annotations
+
+import hashlib
+import types
+from typing import TYPE_CHECKING
+
+from sphinx.locale import __
+
+if TYPE_CHECKING:
+    from collections.abc import Set
+    from pathlib import Path
+    from typing import Any
+
+    from sphinx.config import Config, _ConfigRebuild
+    from sphinx.util.tags import Tags
+
+
+class BuildInfo:
+    """buildinfo file manipulator.
+
+    HTMLBuilder and its family are storing their own envdata to ``.buildinfo``.
+    This class is a manipulator for the file.
+    """
+
+    @classmethod
+    def load(cls: type[BuildInfo], filename: Path, /) -> BuildInfo:
+        content = filename.read_text(encoding="utf-8")
+        lines = content.splitlines()
+
+        version = lines[0].rstrip()
+        if version != '# Sphinx build info version 1':
+            msg = __('failed to read broken build info file (unknown version)')
+            raise ValueError(msg)
+
+        if not lines[2].startswith('config: '):
+            msg = __('failed to read broken build info file (missing config entry)')
+            raise ValueError(msg)
+        if not lines[3].startswith('tags: '):
+            msg = __('failed to read broken build info file (missing tags entry)')
+            raise ValueError(msg)
+
+        build_info = BuildInfo()
+        build_info.config_hash = lines[2].removeprefix('config: ').strip()
+        build_info.tags_hash = lines[3].removeprefix('tags: ').strip()
+        return build_info
+
+    def __init__(
+        self,
+        config: Config | None = None,
+        tags: Tags | None = None,
+        config_categories: Set[_ConfigRebuild] = frozenset(),
+    ) -> None:
+        self.config_hash = ''
+        self.tags_hash = ''
+
+        if config:
+            values = {c.name: c.value for c in config.filter(config_categories)}
+            self.config_hash = _stable_hash(values)
+
+        if tags:
+            self.tags_hash = _stable_hash(sorted(tags))
+
+    def __eq__(self, other: BuildInfo) -> bool:  # type: ignore[override]
+        return (self.config_hash == other.config_hash and
+                self.tags_hash == other.tags_hash)
+
+    def dump(self, filename: Path, /) -> None:
+        build_info = (
+            '# Sphinx build info version 1\n'
+            '# This file records the configuration used when building these files. '
+            'When it is not found, a full rebuild will be done.\n'
+            f'config: {self.config_hash}\n'
+            f'tags: {self.tags_hash}\n'
+        )
+        filename.write_text(build_info, encoding="utf-8")
+
+
+def _stable_hash(obj: Any) -> str:
+    """Return a stable hash for a Python data structure.
+
+    We can't just use the md5 of str(obj) as the order of collections
+    may be random.
+    """
+    if isinstance(obj, dict):
+        obj = sorted(map(_stable_hash, obj.items()))
+    if isinstance(obj, list | tuple | set | frozenset):
+        obj = sorted(map(_stable_hash, obj))
+    elif isinstance(obj, type | types.FunctionType):
+        # The default repr() of functions includes the ID, which is not ideal.
+        # We use the fully qualified name instead.
+        obj = f'{obj.__module__}.{obj.__qualname__}'
+    return hashlib.md5(str(obj).encode(), usedforsecurity=False).hexdigest()
diff --git a/sphinx/builders/singlehtml.py b/sphinx/builders/singlehtml.py
index d222184b52f..4d58d554cf6 100644
--- a/sphinx/builders/singlehtml.py
+++ b/sphinx/builders/singlehtml.py
@@ -52,7 +52,6 @@ def get_relative_uri(self, from_: str, to: str, typ: str | None = None) -> str:
 
     def fix_refuris(self, tree: Node) -> None:
         # fix refuris with double anchor
-        fname = self.config.root_doc + self.out_suffix
         for refnode in tree.findall(nodes.reference):
             if 'refuri' not in refnode:
                 continue
@@ -62,7 +61,8 @@ def fix_refuris(self, tree: Node) -> None:
                 continue
             hashindex = refuri.find('#', hashindex + 1)
             if hashindex >= 0:
-                refnode['refuri'] = fname + refuri[hashindex:]
+                # all references are on the same page...
+                refnode['refuri'] = refuri[hashindex:]
 
     def _get_local_toctree(self, docname: str, collapse: bool = True, **kwargs: Any) -> str:
         if isinstance(includehidden := kwargs.get('includehidden'), str):
diff --git a/sphinx/environment/__init__.py b/sphinx/environment/__init__.py
index 637fe185f7f..67087e61829 100644
--- a/sphinx/environment/__init__.py
+++ b/sphinx/environment/__init__.py
@@ -248,7 +248,7 @@ def __init__(self, app: Sphinx) -> None:
         self.dlfiles: DownloadFiles = DownloadFiles()
 
         # the original URI for images
-        self.original_image_uri: dict[str, str] = {}
+        self.original_image_uri: dict[_StrPath, str] = {}
 
         # temporary data storage while reading a document
         self.temp_data: dict[str, Any] = {}
diff --git a/sphinx/environment/adapters/asset.py b/sphinx/environment/adapters/asset.py
index 57fdc91f14d..dc0cf766957 100644
--- a/sphinx/environment/adapters/asset.py
+++ b/sphinx/environment/adapters/asset.py
@@ -1,6 +1,7 @@
 """Assets adapter for sphinx.environment."""
 
 from sphinx.environment import BuildEnvironment
+from sphinx.util._pathlib import _StrPath
 
 
 class ImageAdapter:
@@ -9,7 +10,7 @@ def __init__(self, env: BuildEnvironment) -> None:
 
     def get_original_image_uri(self, name: str) -> str:
         """Get the original image URI."""
-        while name in self.env.original_image_uri:
-            name = self.env.original_image_uri[name]
+        while _StrPath(name) in self.env.original_image_uri:
+            name = self.env.original_image_uri[_StrPath(name)]
 
         return name
diff --git a/sphinx/transforms/post_transforms/images.py b/sphinx/transforms/post_transforms/images.py
index b679481e83d..05b07dd2232 100644
--- a/sphinx/transforms/post_transforms/images.py
+++ b/sphinx/transforms/post_transforms/images.py
@@ -6,6 +6,7 @@
 import re
 from hashlib import sha1
 from math import ceil
+from pathlib import Path
 from typing import TYPE_CHECKING, Any
 
 from docutils import nodes
@@ -13,6 +14,7 @@
 from sphinx.locale import __
 from sphinx.transforms import SphinxTransform
 from sphinx.util import logging, requests
+from sphinx.util._pathlib import _StrPath
 from sphinx.util.http_date import epoch_to_rfc1123, rfc1123_to_epoch
 from sphinx.util.images import get_image_extension, guess_mimetype, parse_data_uri
 from sphinx.util.osutil import ensuredir
@@ -65,50 +67,58 @@ def handle(self, node: nodes.image) -> None:
             basename = CRITICAL_PATH_CHAR_RE.sub("_", basename)
 
             uri_hash = sha1(node['uri'].encode(), usedforsecurity=False).hexdigest()
-            ensuredir(os.path.join(self.imagedir, uri_hash))
-            path = os.path.join(self.imagedir, uri_hash, basename)
-
-            headers = {}
-            if os.path.exists(path):
-                timestamp: float = ceil(os.stat(path).st_mtime)
-                headers['If-Modified-Since'] = epoch_to_rfc1123(timestamp)
-
-            config = self.app.config
-            r = requests.get(
-                node['uri'], headers=headers,
-                _user_agent=config.user_agent,
-                _tls_info=(config.tls_verify, config.tls_cacerts),
-            )
-            if r.status_code >= 400:
-                logger.warning(__('Could not fetch remote image: %s [%d]'),
-                               node['uri'], r.status_code)
-            else:
-                self.app.env.original_image_uri[path] = node['uri']
-
-                if r.status_code == 200:
-                    with open(path, 'wb') as f:
-                        f.write(r.content)
-
-                last_modified = r.headers.get('last-modified')
-                if last_modified:
-                    timestamp = rfc1123_to_epoch(last_modified)
-                    os.utime(path, (timestamp, timestamp))
-
-                mimetype = guess_mimetype(path, default='*')
-                if mimetype != '*' and os.path.splitext(basename)[1] == '':
-                    # append a suffix if URI does not contain suffix
-                    ext = get_image_extension(mimetype)
-                    newpath = os.path.join(self.imagedir, uri_hash, basename + ext)
-                    os.replace(path, newpath)
-                    self.app.env.original_image_uri.pop(path)
-                    self.app.env.original_image_uri[newpath] = node['uri']
-                    path = newpath
-                node['candidates'].pop('?')
-                node['candidates'][mimetype] = path
-                node['uri'] = path
-                self.app.env.images.add_file(self.env.docname, path)
+            path = Path(self.imagedir, uri_hash, basename)
+            path.parent.mkdir(parents=True, exist_ok=True)
+            self._download_image(node, path)
+
         except Exception as exc:
-            logger.warning(__('Could not fetch remote image: %s [%s]'), node['uri'], exc)
+            msg = __('Could not fetch remote image: %s [%s]')
+            logger.warning(msg, node['uri'], exc)
+
+    def _download_image(self, node: nodes.image, path: Path) -> None:
+        headers = {}
+        if path.exists():
+            timestamp: float = ceil(path.stat().st_mtime)
+            headers['If-Modified-Since'] = epoch_to_rfc1123(timestamp)
+
+        config = self.app.config
+        r = requests.get(
+            node['uri'], headers=headers,
+            _user_agent=config.user_agent,
+            _tls_info=(config.tls_verify, config.tls_cacerts),
+        )
+        if r.status_code >= 400:
+            msg = __('Could not fetch remote image: %s [%d]')
+            logger.warning(msg, node['uri'], r.status_code)
+        else:
+            self.app.env.original_image_uri[_StrPath(path)] = node['uri']
+
+            if r.status_code == 200:
+                path.write_bytes(r.content)
+            if last_modified := r.headers.get('Last-Modified'):
+                timestamp = rfc1123_to_epoch(last_modified)
+                os.utime(path, (timestamp, timestamp))
+
+            self._process_image(node, path)
+
+    def _process_image(self, node: nodes.image, path: Path) -> None:
+        str_path = _StrPath(path)
+        self.app.env.original_image_uri[str_path] = node['uri']
+
+        mimetype = guess_mimetype(path, default='*')
+        if mimetype != '*' and path.suffix == '':
+            # append a suffix if URI does not contain suffix
+            ext = get_image_extension(mimetype) or ''
+            with_ext = path.with_name(path.name + ext)
+            os.replace(path, with_ext)
+            self.app.env.original_image_uri.pop(str_path)
+            self.app.env.original_image_uri[_StrPath(with_ext)] = node['uri']
+            path = with_ext
+        path_str = str(path)
+        node['candidates'].pop('?')
+        node['candidates'][mimetype] = path_str
+        node['uri'] = path_str
+        self.app.env.images.add_file(self.env.docname, path_str)
 
 
 class DataURIExtractor(BaseImageConverter):
@@ -130,16 +140,17 @@ def handle(self, node: nodes.image) -> None:
 
         ensuredir(os.path.join(self.imagedir, 'embeded'))
         digest = sha1(image.data, usedforsecurity=False).hexdigest()
-        path = os.path.join(self.imagedir, 'embeded', digest + ext)
+        path = _StrPath(self.imagedir, 'embeded', digest + ext)
         self.app.env.original_image_uri[path] = node['uri']
 
         with open(path, 'wb') as f:
             f.write(image.data)
 
+        path_str = str(path)
         node['candidates'].pop('?')
-        node['candidates'][image.mimetype] = path
-        node['uri'] = path
-        self.app.env.images.add_file(self.env.docname, path)
+        node['candidates'][image.mimetype] = path_str
+        node['uri'] = path_str
+        self.app.env.images.add_file(self.env.docname, path_str)
 
 
 def get_filename_for(filename: str, mimetype: str) -> str:
@@ -258,7 +269,7 @@ def handle(self, node: nodes.image) -> None:
                 node['candidates'][_to] = destpath
             node['uri'] = destpath
 
-            self.env.original_image_uri[destpath] = srcpath
+            self.env.original_image_uri[_StrPath(destpath)] = srcpath
             self.env.images.add_file(self.env.docname, destpath)
 
     def convert(self, _from: str, _to: str) -> bool:
diff --git a/tests/conftest.py b/tests/conftest.py
index 6e3b83b1397..a9ef8e7c92c 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -4,6 +4,7 @@
 import os
 import sys
 from pathlib import Path
+from types import SimpleNamespace
 from typing import TYPE_CHECKING
 
 import docutils
@@ -60,3 +61,20 @@ def _cleanup_docutils() -> Iterator[None]:
     sys.path[:] = saved_path
 
     _clean_up_global_state()
+
+
+@pytest.fixture
+def _http_teapot(monkeypatch: pytest.MonkeyPatch) -> Iterator[None]:
+    """Short-circuit HTTP requests.
+
+    Windows takes too long to fail on connections, hence this fixture.
+    """
+    # https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/418
+    response = SimpleNamespace(status_code=418)
+
+    def _request(*args, **kwargs):
+        return response
+
+    with monkeypatch.context() as m:
+        m.setattr('sphinx.util.requests._Session.request', _request)
+        yield
diff --git a/tests/test_builders/test_build.py b/tests/test_builders/test_build.py
index 5ccef02c943..6a5ed0b6d26 100644
--- a/tests/test_builders/test_build.py
+++ b/tests/test_builders/test_build.py
@@ -100,6 +100,7 @@ def test_numbered_circular_toctree(app):
     ) in warnings
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx('dummy', testroot='images')
 def test_image_glob(app):
     app.build(force_all=True)
diff --git a/tests/test_builders/test_build_epub.py b/tests/test_builders/test_build_epub.py
index 263fefe8090..178b46ff0a2 100644
--- a/tests/test_builders/test_build_epub.py
+++ b/tests/test_builders/test_build_epub.py
@@ -473,6 +473,7 @@ def test_xml_name_pattern_check():
     assert not _XML_NAME_PATTERN.match('1bfda21')
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx('epub', testroot='images')
 def test_copy_images(app):
     app.build()
diff --git a/tests/test_builders/test_build_html.py b/tests/test_builders/test_build_html.py
index 93e770cca9c..ecaab1651a1 100644
--- a/tests/test_builders/test_build_html.py
+++ b/tests/test_builders/test_build_html.py
@@ -266,6 +266,7 @@ def test_html_inventory(app):
     )
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx(
     'html',
     testroot='images',
diff --git a/tests/test_builders/test_build_html_image.py b/tests/test_builders/test_build_html_image.py
index 93777c76329..15b0be7aaea 100644
--- a/tests/test_builders/test_build_html_image.py
+++ b/tests/test_builders/test_build_html_image.py
@@ -5,6 +5,7 @@
 import pytest
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx('html', testroot='images')
 def test_html_remote_images(app):
     app.build(force_all=True)
@@ -77,6 +78,7 @@ def test_html_scaled_image_link(app):
     )
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx('html', testroot='images')
 def test_copy_images(app):
     app.build()
diff --git a/tests/test_builders/test_build_html_tocdepth.py b/tests/test_builders/test_build_html_tocdepth.py
index dda049c47ff..7d6afc4c1c3 100644
--- a/tests/test_builders/test_build_html_tocdepth.py
+++ b/tests/test_builders/test_build_html_tocdepth.py
@@ -2,6 +2,7 @@
 
 import pytest
 
+from tests.test_builders.xpath_html_util import _intradocument_hyperlink_check
 from tests.test_builders.xpath_util import check_xpath
 
 
@@ -78,6 +79,7 @@ def test_tocdepth(app, cached_etree_parse, fname, path, check, be_found):
         (".//li[@class='toctree-l3']/a", '1.2.1. Foo B1', True),
         (".//li[@class='toctree-l3']/a", '2.1.1. Bar A1', False),
         (".//li[@class='toctree-l3']/a", '2.2.1. Bar B1', False),
+        (".//ul/li[@class='toctree-l1']/..//a", _intradocument_hyperlink_check),
         # index.rst
         ('.//h1', 'test-tocdepth', True),
         # foo.rst
diff --git a/tests/test_toctree.py b/tests/test_builders/test_build_html_toctree.py
similarity index 74%
rename from tests/test_toctree.py
rename to tests/test_builders/test_build_html_toctree.py
index 39aac47a679..4195ac2e41b 100644
--- a/tests/test_toctree.py
+++ b/tests/test_builders/test_build_html_toctree.py
@@ -4,6 +4,9 @@
 
 import pytest
 
+from tests.test_builders.xpath_html_util import _intradocument_hyperlink_check
+from tests.test_builders.xpath_util import check_xpath
+
 
 @pytest.mark.sphinx(testroot='toctree-glob')
 def test_relations(app):
@@ -45,3 +48,17 @@ def test_numbered_toctree(app):
     index = re.sub(':numbered:.*', ':numbered: 1', index)
     (app.srcdir / 'index.rst').write_text(index, encoding='utf8')
     app.build(force_all=True)
+
+
+@pytest.mark.parametrize(
+    'expect',
+    [
+        # internal references should be same-document; external should not
+        (".//a[@class='reference internal']", _intradocument_hyperlink_check),
+        (".//a[@class='reference external']", r'https?://'),
+    ],
+)
+@pytest.mark.sphinx('singlehtml', testroot='toctree')
+def test_singlehtml_hyperlinks(app, cached_etree_parse, expect):
+    app.build()
+    check_xpath(cached_etree_parse(app.outdir / 'index.html'), 'index.html', *expect)
diff --git a/tests/test_builders/test_build_latex.py b/tests/test_builders/test_build_latex.py
index b1eb2dfa4ea..a558abf5e1e 100644
--- a/tests/test_builders/test_build_latex.py
+++ b/tests/test_builders/test_build_latex.py
@@ -2157,6 +2157,7 @@ def test_latex_code_role(app):
     ) in content
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx('latex', testroot='images')
 def test_copy_images(app):
     app.build()
diff --git a/tests/test_builders/test_build_texinfo.py b/tests/test_builders/test_build_texinfo.py
index 07934ad1825..7f229db83dd 100644
--- a/tests/test_builders/test_build_texinfo.py
+++ b/tests/test_builders/test_build_texinfo.py
@@ -131,6 +131,7 @@ def test_texinfo_samp_with_variable(app):
     assert '@code{Show @var{variable} in the middle}' in output
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx('texinfo', testroot='images')
 def test_copy_images(app):
     app.build()
diff --git a/tests/test_builders/xpath_html_util.py b/tests/test_builders/xpath_html_util.py
new file mode 100644
index 00000000000..b0949c80429
--- /dev/null
+++ b/tests/test_builders/xpath_html_util.py
@@ -0,0 +1,19 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from collections.abc import Sequence
+    from xml.etree.ElementTree import Element
+
+
+def _intradocument_hyperlink_check(nodes: Sequence[Element]) -> None:
+    """Confirm that a series of nodes are all HTML hyperlinks to the current page"""
+    assert nodes, 'Expected at least one node to check'
+    for node in nodes:
+        assert node.tag == 'a', 'Attempted to check hyperlink on a non-anchor element'
+        href = node.attrib.get('href')
+        # Allow Sphinx index and table hyperlinks to be non-same-document, as exceptions.
+        if href in {'genindex.html', 'py-modindex.html', 'search.html'}:
+            continue
+        assert not href or href.startswith('#'), 'Hyperlink failed same-document check'
diff --git a/tests/test_extensions/test_ext_math.py b/tests/test_extensions/test_ext_math.py
index a18a410c42c..5a866520afb 100644
--- a/tests/test_extensions/test_ext_math.py
+++ b/tests/test_extensions/test_ext_math.py
@@ -288,6 +288,7 @@ def test_mathjax_numsep_html(app):
     assert html in content
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx(
     'html',
     testroot='ext-math',
diff --git a/tests/test_intl/test_intl.py b/tests/test_intl/test_intl.py
index e664d479999..74e9cf57e60 100644
--- a/tests/test_intl/test_intl.py
+++ b/tests/test_intl/test_intl.py
@@ -1705,6 +1705,7 @@ def test_text_prolog_epilog_substitution(app):
     )
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx(
     'dummy',
     testroot='images',
@@ -1782,6 +1783,7 @@ def test_image_glob_intl(app):
     )
 
 
+@pytest.mark.usefixtures('_http_teapot')
 @pytest.mark.sphinx(
     'dummy',
     testroot='images',