diff --git a/CHANGELOG.md b/CHANGELOG.md
index dc1e65506..f0e0c71e1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,12 @@
 
 ## [Unreleased]
 
-- Buildpack error messages are now more consistently formatted and use colour. ([#1639](https://github.com/heroku/heroku-buildpack-python/pull/1639))
+- Moved the SQLite3 install step prior to installing dependencies when using Pipenv. This now matches the behaviour when using pip and allows dependencies to actually use the headers. ([#1640](https://github.com/heroku/heroku-buildpack-python/pull/1640))
+- Stopped exposing the `SKIP_PIP_INSTALL` env var to `bin/post_compile` and other subprocesses when using Pipenv. ([#1640](https://github.com/heroku/heroku-buildpack-python/pull/1640))
+- Stopped creating `.heroku/python/requirements-{declared,installed}.txt` files when using pip. ([#1640](https://github.com/heroku/heroku-buildpack-python/pull/1640))
+- Stopped creating a placeholder `requirements.txt` file when an app only has a `setup.py` file and no other package manager files. Instead pip is now invoked directly using `--editable .`. ([#1640](https://github.com/heroku/heroku-buildpack-python/pull/1640))
+- Improved buildpack metrics for package manager detection and duration of install steps. ([#1640](https://github.com/heroku/heroku-buildpack-python/pull/1640))
+- Updated buildpack-generated error messages to use colour and be more consistently formatted. ([#1639](https://github.com/heroku/heroku-buildpack-python/pull/1639))
 
 ## [v256] - 2024-09-07
 
diff --git a/bin/compile b/bin/compile
index 9bd6482b7..d598039e9 100755
--- a/bin/compile
+++ b/bin/compile
@@ -16,6 +16,10 @@ BUILDPACK_DIR=$(cd "$(dirname "$(dirname "${BASH_SOURCE[0]}")")" && pwd)
 source "${BUILDPACK_DIR}/bin/utils"
 source "${BUILDPACK_DIR}/lib/metadata.sh"
 source "${BUILDPACK_DIR}/lib/output.sh"
+source "${BUILDPACK_DIR}/lib/package_manager.sh"
+source "${BUILDPACK_DIR}/lib/pip.sh"
+source "${BUILDPACK_DIR}/lib/pipenv.sh"
+source "${BUILDPACK_DIR}/lib/utils.sh"
 
 compile_start_time=$(nowms)
 
@@ -97,12 +101,10 @@ cd "$BUILD_DIR"
 # - The build is executed, modifying `~/.heroku/{known-paths}`.
 # - Once the build is complete, `~/.heroku/{known-paths}` is copied back into the cache.
 
-# Create the cache directory, if it doesn't exist.
 mkdir -p "$CACHE_DIR/.heroku"
 
 # Restore old artifacts from the cache.
 mkdir -p .heroku
-
 # The Python installation.
 cp -R "$CACHE_DIR/.heroku/python" .heroku/ &>/dev/null || true
 # A plain text file which contains the current stack being used (used for cache busting).
@@ -116,10 +118,7 @@ if [[ -d "$CACHE_DIR/.heroku/src" ]]; then
 	cp -R "$CACHE_DIR/.heroku/src" .heroku/ &>/dev/null || true
 fi
 
-# The pre_compile hook. Customers rely on this. Don't remove it.
-# This part of the code is used to allow users to customize their build experience
-# without forking the buildpack by providing a `bin/pre_compile` script, which gets
-# run inline with the buildpack automatically.
+# Runs a `bin/pre_compile` script if found in the app source, allowing build customisation.
 source "${BUILDPACK_DIR}/bin/steps/hooks/pre_compile"
 
 # Sticky runtimes. If there was a previous build, and it used a given version of Python,
@@ -128,43 +127,15 @@ if [[ -f "$CACHE_DIR/.heroku/python-version" ]]; then
 	CACHED_PYTHON_VERSION=$(cat "$CACHE_DIR/.heroku/python-version")
 fi
 
-# We didn't always record the stack version. This code is in place because of that.
+# We didn't always record the stack version.
 if [[ -f "$CACHE_DIR/.heroku/python-stack" ]]; then
 	CACHED_PYTHON_STACK=$(cat "$CACHE_DIR/.heroku/python-stack")
 else
 	CACHED_PYTHON_STACK=$STACK
 fi
 
-# TODO: Move this into a new package manager handling implementation when adding Poetry support.
-# We intentionally don't mention `setup.py` here since it's being removed soon.
-if [[ ! -f requirements.txt && ! -f Pipfile && ! -f setup.py ]]; then
-	display_error <<-EOF
-		Error: Couldn't find any supported Python package manager files.
-
-		A Python app on Heroku must have either a 'requirements.txt' or
-		'Pipfile' package manager file in the root directory of its
-		source code.
-
-		Currently the root directory of your app contains:
-
-		$(ls -1 --indicator-style=slash "${BUILD_DIR}")
-
-		If your app already has a package manager file, check that it:
-
-		1. Is in the top level directory (not a subdirectory).
-		2. Has the correct spelling (the filenames are case-sensitive).
-		3. Isn't listed in '.gitignore' or '.slugignore'.
-
-		Otherwise, add a package manager file to your app. If your app has
-		no dependencies, then create an empty 'requirements.txt' file.
-
-		For help with using Python on Heroku, see:
-		https://devcenter.heroku.com/articles/getting-started-with-python
-		https://devcenter.heroku.com/articles/python-support
-	EOF
-	meta_set "failure_reason" "package-manager-not-found"
-	exit 1
-fi
+PACKAGE_MANAGER=$(package_manager::determine_package_manager "${BUILD_DIR}")
+meta_set "package_manager" "${PACKAGE_MANAGER}"
 
 # Pipenv Python version support.
 # Detect the version of Python requested from a Pipfile (e.g. python_version or python_full_version).
@@ -189,9 +160,9 @@ else
 	echo "${DEFAULT_PYTHON_VERSION}" >runtime.txt
 fi
 
-# Create the directory for .profile.d, if it doesn't exist.
+# The directory for the .profile.d scripts.
 mkdir -p "$(dirname "$PROFILE_PATH")"
-# Create the directory for editable source code installation, if it doesn't exist.
+# The directory for editable VCS dependencies.
 mkdir -p /app/.heroku/src
 
 # On Heroku CI, builds happen in `/app`. Otherwise, on the Heroku platform,
@@ -207,46 +178,58 @@ if [[ "$(realpath "${BUILD_DIR}")" != "$(realpath /app)" ]]; then
 	# Note: .heroku/src is copied in later.
 fi
 
-# Download / Install Python, from pre-build binaries available on Amazon S3.
-# This step also bootstraps pip / setuptools.
+# Download and install Python using pre-built binaries from S3.
 install_python_start_time=$(nowms)
 source "${BUILDPACK_DIR}/bin/steps/python"
 meta_time "python_install_duration" "${install_python_start_time}"
 
-# Install Pipenv dependencies, if a Pipfile was provided.
-source "${BUILDPACK_DIR}/bin/steps/pipenv"
-
-# If no requirements.txt file given, assume `setup.py develop` is intended.
-# This allows for people to ship a setup.py application to Heroku
-
-if [[ ! -f requirements.txt ]] && [[ ! -f Pipfile ]]; then
-	meta_set "setup_py_only" "true"
-	echo "-e ." >requirements.txt
-else
-	meta_set "setup_py_only" "false"
-fi
+# Install the package manager and related tools.
+package_manager_install_start_time=$(nowms)
+bundled_pip_module_path="$(utils::bundled_pip_module_path "${BUILD_DIR}")"
+case "${PACKAGE_MANAGER}" in
+	pip)
+		pip::install_pip_setuptools_wheel "${bundled_pip_module_path}"
+		;;
+	pipenv)
+		# TODO: Stop installing pip when using Pipenv.
+		pip::install_pip_setuptools_wheel "${bundled_pip_module_path}"
+		pipenv::install_pipenv
+		;;
+	*)
+		abort_internal_error "Unhandled package manager"
+		;;
+esac
+meta_time "package_manager_install_duration" "${package_manager_install_start_time}"
 
 # SQLite3 support.
-# This sets up and installs sqlite3 dev headers and the sqlite3 binary but not the
-# libsqlite3-0 library since that exists on the stack image.
+# Installs the sqlite3 dev headers and sqlite3 binary but not the
+# libsqlite3-0 library since that exists in the base image.
 install_sqlite_start_time=$(nowms)
 source "${BUILDPACK_DIR}/bin/steps/sqlite3"
 buildpack_sqlite3_install
 meta_time "sqlite_install_duration" "${install_sqlite_start_time}"
 
-# pip install
-# -----------
-
-# Install dependencies with pip (where the magic happens).
-source "${BUILDPACK_DIR}/bin/steps/pip-install"
+# Install app dependencies.
+dependencies_install_start_time=$(nowms)
+case "${PACKAGE_MANAGER}" in
+	pip)
+		pip::install_dependencies
+		;;
+	pipenv)
+		pipenv::install_dependencies
+		;;
+	*)
+		abort_internal_error "Unhandled package manager"
+		;;
+esac
+meta_time "dependencies_install_duration" "${dependencies_install_start_time}"
 
 # Support for NLTK corpora.
 nltk_downloader_start_time=$(nowms)
 sub_env "${BUILDPACK_DIR}/bin/steps/nltk"
 meta_time "nltk_downloader_duration" "${nltk_downloader_start_time}"
 
-# Support for editable installations. Here, we are copying pip–created src directory,
-# and copying it into the proper place (the logical place to do this was early, but it must be done here).
+# Support for editable installations.
 # In CI, $BUILD_DIR is /app.
 # Realpath is used to support use-cases where one of the locations is a symlink to the other.
 if [[ "$(realpath "${BUILD_DIR}")" != "$(realpath /app)" ]]; then
@@ -256,9 +239,6 @@ fi
 
 # Django collectstatic support.
 # The buildpack automatically runs collectstatic for Django applications.
-# This is the cause for the majority of build failures on the Python platform.
-# These failures are intentional — if collectstatic (which can be tricky, at times) fails,
-# your build fails.
 collectstatic_start_time=$(nowms)
 sub_env "${BUILDPACK_DIR}/bin/steps/collectstatic"
 meta_time "django_collectstatic_duration" "${collectstatic_start_time}"
@@ -304,7 +284,7 @@ fi
 cp "${BUILDPACK_DIR}/vendor/WEB_CONCURRENCY.sh" "$WEB_CONCURRENCY_PROFILE_PATH"
 cp "${BUILDPACK_DIR}/vendor/python.gunicorn.sh" "$GUNICORN_PROFILE_PATH"
 
-# Experimental post_compile hook. Don't remove this.
+# Runs a `bin/post_compile` script if found in the app source, allowing build customisation.
 source "${BUILDPACK_DIR}/bin/steps/hooks/post_compile"
 
 # Store new artifacts in the cache.
diff --git a/bin/report b/bin/report
index 9210d7371..5697a7f57 100755
--- a/bin/report
+++ b/bin/report
@@ -67,6 +67,7 @@ STRING_FIELDS=(
 	failure_reason
 	nltk_downloader
 	package_manager
+	package_manager_multiple_found
 	pip_version
 	pipenv_version
 	python_version_major
@@ -81,6 +82,7 @@ ALL_OTHER_FIELDS=(
 	dependencies_install_duration
 	django_collectstatic_duration
 	nltk_downloader_duration
+	package_manager_install_duration
 	pipenv_has_lockfile
 	post_compile_hook
 	post_compile_hook_duration
diff --git a/bin/steps/pip-install b/bin/steps/pip-install
deleted file mode 100755
index 86ecfd0d3..000000000
--- a/bin/steps/pip-install
+++ /dev/null
@@ -1,44 +0,0 @@
-#!/usr/bin/env bash
-
-if [[ -z "$SKIP_PIP_INSTALL" ]]; then
-	pip_install_start_time=$(nowms)
-	meta_set "package_manager" "pip"
-
-	puts-step "Installing requirements with pip"
-
-	# Set Pip env vars
-	# This reads certain environment variables set on the Heroku app config
-	# and makes them accessible to the pip install process.
-	#
-	# PIP_EXTRA_INDEX_URL allows for an alternate pypi URL to be used.
-	if [[ -r "$ENV_DIR/PIP_EXTRA_INDEX_URL" ]]; then
-		PIP_EXTRA_INDEX_URL="$(cat "$ENV_DIR/PIP_EXTRA_INDEX_URL")"
-		export PIP_EXTRA_INDEX_URL
-	fi
-
-	set +e
-
-	/app/.heroku/python/bin/pip install -r requirements.txt --exists-action=w --src='/app/.heroku/src' --disable-pip-version-check --no-cache-dir --progress-bar off 2>&1 | tee "$WARNINGS_LOG" | cleanup | indent
-	PIP_STATUS="${PIPESTATUS[0]}"
-	set -e
-
-	show-warnings
-
-	if [[ ! $PIP_STATUS -eq 0 ]]; then
-		meta_set "failure_reason" "pip-install"
-		exit 1
-	fi
-
-	cp requirements.txt .heroku/python/requirements-declared.txt
-	/app/.heroku/python/bin/pip freeze --disable-pip-version-check >.heroku/python/requirements-installed.txt
-
-	# Install test dependencies, for CI.
-	if [[ -n "$INSTALL_TEST" ]]; then
-		if [[ -f requirements-test.txt ]]; then
-			puts-step "Installing test dependencies..."
-			/app/.heroku/python/bin/pip install -r requirements-test.txt --exists-action=w --src='/app/.heroku/src' --disable-pip-version-check --no-cache-dir 2>&1 | cleanup | indent
-		fi
-	fi
-
-	meta_time "dependencies_install_duration" "${pip_install_start_time}"
-fi
diff --git a/bin/steps/pipenv-python-version b/bin/steps/pipenv-python-version
index b6614cf99..6b4bd46e5 100755
--- a/bin/steps/pipenv-python-version
+++ b/bin/steps/pipenv-python-version
@@ -1,8 +1,10 @@
 #!/usr/bin/env bash
 
+# TODO: Move this to lib/ as part of the refactoring for .python-version support.
+
 # Detect Python-version with Pipenv.
 
-if [[ -f $BUILD_DIR/Pipfile ]]; then
+if [[ "${PACKAGE_MANAGER}" == "pipenv" ]]; then
 
 	if [[ ! -f $BUILD_DIR/runtime.txt ]]; then
 		if [[ ! -f $BUILD_DIR/Pipfile.lock ]]; then
diff --git a/bin/steps/python b/bin/steps/python
index 3c1e36e57..56af2778e 100755
--- a/bin/steps/python
+++ b/bin/steps/python
@@ -166,34 +166,3 @@ else
 
 	hash -r
 fi
-
-PIP_VERSION=$(get_requirement_version 'pip')
-SETUPTOOLS_VERSION=$(get_requirement_version 'setuptools')
-WHEEL_VERSION=$(get_requirement_version 'wheel')
-
-puts-step "Installing pip ${PIP_VERSION}, setuptools ${SETUPTOOLS_VERSION} and wheel ${WHEEL_VERSION}"
-
-meta_set "pip_version" "${PIP_VERSION}"
-meta_set "setuptools_version" "${SETUPTOOLS_VERSION}"
-meta_set "wheel_version" "${WHEEL_VERSION}"
-
-# Python bundles Pip within its standard library, which we can use to install our chosen
-# pip version from PyPI, saving us from having to download the usual pip bootstrap script.
-# We have to use a glob since the bundled wheel filename contains the pip version, which
-# differs between Python versions. We also have to handle the case where there are multiple
-# matching pip wheels, since in some versions of Python (eg 3.9.0) multiple versions of pip
-# were accidentally bundled upstream. Note: This implementation relies upon `nullglob` being
-# set, which is the case thanks to the `bin/utils` that was run earlier.
-BUNDLED_PIP_WHEEL_LIST=(.heroku/python/lib/python*/ensurepip/_bundled/pip-*.whl)
-BUNDLED_PIP_WHEEL="${BUNDLED_PIP_WHEEL_LIST[0]}"
-
-if [[ -z "${BUNDLED_PIP_WHEEL}" ]]; then
-	display_error "Error: Failed to locate the bundled pip wheel."
-	meta_set "failure_reason" "bundled-pip-not-found"
-	exit 1
-fi
-
-/app/.heroku/python/bin/python "${BUNDLED_PIP_WHEEL}/pip" install --quiet --disable-pip-version-check --no-cache-dir \
-	"pip==${PIP_VERSION}" "setuptools==${SETUPTOOLS_VERSION}" "wheel==${WHEEL_VERSION}"
-
-hash -r
diff --git a/buildpack.toml b/buildpack.toml
index 07f83d4cf..4ccd6f242 100644
--- a/buildpack.toml
+++ b/buildpack.toml
@@ -7,6 +7,7 @@ files = [
   "builds/",
   "etc/publish.sh",
   "spec/",
+  ".editorconfig",
   ".gitignore",
   ".rubocop.yml",
   ".shellcheckrc",
diff --git a/lib/kvstore.sh b/lib/kvstore.sh
index 17e2dd0d0..4bfdc85ac 100644
--- a/lib/kvstore.sh
+++ b/lib/kvstore.sh
@@ -1,5 +1,7 @@
 #!/usr/bin/env bash
 
+# TODO: Switch this file to using namespaced functions like `kvstore::<fn_name>`.
+
 # Taken from: https://github.com/heroku/heroku-buildpack-nodejs/blob/main/lib/kvstore.sh
 
 kv_create() {
diff --git a/lib/metadata.sh b/lib/metadata.sh
index 7d2a39b7a..3def5ded3 100644
--- a/lib/metadata.sh
+++ b/lib/metadata.sh
@@ -1,5 +1,7 @@
 #!/usr/bin/env bash
 
+# TODO: Switch this file to using namespaced functions like `metadata::<fn_name>`.
+
 # Based on: https://github.com/heroku/heroku-buildpack-nodejs/blob/main/lib/metadata.sh
 
 source "${BUILDPACK_DIR}/lib/kvstore.sh"
diff --git a/lib/output.sh b/lib/output.sh
index e063ddd88..246e689bf 100644
--- a/lib/output.sh
+++ b/lib/output.sh
@@ -1,5 +1,7 @@
 #!/usr/bin/env bash
 
+# TODO: Switch this file to using namespaced functions like `output::<fn_name>`.
+
 ANSI_RED='\033[1;31m'
 ANSI_RESET='\033[0m'
 
diff --git a/lib/package_manager.sh b/lib/package_manager.sh
new file mode 100644
index 000000000..d776c08a5
--- /dev/null
+++ b/lib/package_manager.sh
@@ -0,0 +1,77 @@
+#!/usr/bin/env bash
+
+function package_manager::determine_package_manager() {
+	local build_dir="${1}"
+	local package_managers_found=()
+
+	if [[ -f "${build_dir}/Pipfile.lock" ]]; then
+		package_managers_found+=(pipenv)
+		meta_set "pipenv_has_lockfile" "true"
+	elif [[ -f "${build_dir}/Pipfile" ]]; then
+		# TODO: Start requiring a Pipfile.lock and make this branch a "missing lockfile" error instead.
+		package_managers_found+=(pipenv)
+		meta_set "pipenv_has_lockfile" "false"
+	fi
+
+	if [[ -f "${build_dir}/requirements.txt" ]]; then
+		package_managers_found+=(pip)
+	fi
+
+	# TODO: Deprecate/sunset this fallback, since using setup.py declared dependencies is
+	# not a best practice, and we can only guess as to which package manager to use.
+	if ((${#package_managers_found[@]} == 0)) && [[ -f "${build_dir}/setup.py" ]]; then
+		package_managers_found+=(pip)
+		meta_set "setup_py_only" "true"
+	else
+		meta_set "setup_py_only" "false"
+	fi
+
+	case "${#package_managers_found[@]}" in
+		1)
+			echo "${package_managers_found[0]}"
+			return 0
+			;;
+		0)
+			display_error <<-EOF
+				Error: Couldn't find any supported Python package manager files.
+
+				A Python app on Heroku must have either a 'requirements.txt' or
+				'Pipfile' package manager file in the root directory of its
+				source code.
+
+				Currently the root directory of your app contains:
+
+				$(ls -1 --indicator-style=slash "${build_dir}" || true)
+
+				If your app already has a package manager file, check that it:
+
+				1. Is in the top level directory (not a subdirectory).
+				2. Has the correct spelling (the filenames are case-sensitive).
+				3. Isn't listed in '.gitignore' or '.slugignore'.
+
+				Otherwise, add a package manager file to your app. If your app has
+				no dependencies, then create an empty 'requirements.txt' file.
+
+				For help with using Python on Heroku, see:
+				https://devcenter.heroku.com/articles/getting-started-with-python
+				https://devcenter.heroku.com/articles/python-support
+			EOF
+			meta_set "failure_reason" "package-manager-not-found"
+			return 1
+			;;
+		*)
+			# If multiple package managers are found, use the first found above.
+			# TODO: Turn this case into an error since it results in support tickets from users
+			# who don't realise they have multiple package manager files and think their changes
+			# aren't taking effect. (We'll need to wait until after Poetry support has landed,
+			# and people have had a chance to migrate from the third-party Poetry buildpack,
+			# since using it results in both a requirements.txt and a poetry.lock.)
+			echo "${package_managers_found[0]}"
+			meta_set "package_manager_multiple_found" "$(
+				IFS=,
+				echo "${package_managers_found[*]}"
+			)"
+			return 0
+			;;
+	esac
+}
diff --git a/lib/pip.sh b/lib/pip.sh
new file mode 100644
index 000000000..4ba2a6812
--- /dev/null
+++ b/lib/pip.sh
@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+
+function pip::install_pip_setuptools_wheel() {
+	# We use the pip wheel bundled within Python's standard library to install our chosen
+	# pip version, since it's faster than `ensurepip` followed by an upgrade in place.
+	local bundled_pip_module_path="${1}"
+
+	# TODO: Either make these `local` or move elsewhere as part of the cache invalidation refactoring.
+	PIP_VERSION=$(get_requirement_version 'pip')
+	SETUPTOOLS_VERSION=$(get_requirement_version 'setuptools')
+	WHEEL_VERSION=$(get_requirement_version 'wheel')
+	meta_set "pip_version" "${PIP_VERSION}"
+	meta_set "setuptools_version" "${SETUPTOOLS_VERSION}"
+	meta_set "wheel_version" "${WHEEL_VERSION}"
+
+	puts-step "Installing pip ${PIP_VERSION}, setuptools ${SETUPTOOLS_VERSION} and wheel ${WHEEL_VERSION}"
+
+	/app/.heroku/python/bin/python "${bundled_pip_module_path}" install --quiet --disable-pip-version-check --no-cache-dir \
+		"pip==${PIP_VERSION}" "setuptools==${SETUPTOOLS_VERSION}" "wheel==${WHEEL_VERSION}"
+}
+
+function pip::install_dependencies() {
+	puts-step "Installing requirements with pip"
+
+	# Make select pip config vars set on the Heroku app available to pip.
+	# TODO: Expose all config vars (after suitable checks are added for unsafe env vars)
+	# to allow for the env var interpolation feature of requirements files to work.
+	#
+	# PIP_EXTRA_INDEX_URL allows for an alternate pypi URL to be used.
+	if [[ -r "${ENV_DIR}/PIP_EXTRA_INDEX_URL" ]]; then
+		PIP_EXTRA_INDEX_URL="$(cat "${ENV_DIR}/PIP_EXTRA_INDEX_URL")"
+		export PIP_EXTRA_INDEX_URL
+	fi
+
+	# TODO: Deprecate/sunset this missing requirements file fallback.
+	if [[ -f setup.py && ! -f requirements.txt ]]; then
+		args=(--editable .)
+	else
+		args=(-r requirements.txt)
+	fi
+
+	set +e
+	/app/.heroku/python/bin/pip install "${args[@]}" --exists-action=w --src='/app/.heroku/src' --disable-pip-version-check --no-cache-dir --progress-bar off 2>&1 | tee "$WARNINGS_LOG" | cleanup | indent
+	local PIP_STATUS="${PIPESTATUS[0]}"
+	set -e
+
+	show-warnings
+
+	if [[ ! ${PIP_STATUS} -eq 0 ]]; then
+		meta_set "failure_reason" "pip-install"
+		return 1
+	fi
+
+	# Install test dependencies, for Heroku CI.
+	if [[ -n "${INSTALL_TEST}" ]]; then
+		if [[ -f requirements-test.txt ]]; then
+			puts-step "Installing test dependencies..."
+			/app/.heroku/python/bin/pip install -r requirements-test.txt --exists-action=w --src='/app/.heroku/src' --disable-pip-version-check --no-cache-dir 2>&1 | cleanup | indent
+		fi
+	fi
+}
diff --git a/bin/steps/pipenv b/lib/pipenv.sh
old mode 100755
new mode 100644
similarity index 60%
rename from bin/steps/pipenv
rename to lib/pipenv.sh
index 6974ae2d5..56ee6b5c2
--- a/bin/steps/pipenv
+++ b/lib/pipenv.sh
@@ -3,54 +3,46 @@
 # export CLINT_FORCE_COLOR=1
 # export PIPENV_FORCE_COLOR=1
 
+function pipenv::install_pipenv() {
+	# TODO: Either make this `local` or move elsewhere as part of the cache invalidation refactoring.
+	PIPENV_VERSION=$(get_requirement_version 'pipenv')
+	meta_set "pipenv_version" "${PIPENV_VERSION}"
+
+	puts-step "Installing Pipenv ${PIPENV_VERSION}"
+
+	# TODO: Install Pipenv into a venv so it isn't leaked into the app environment.
+	# TODO: Explore viability of making Pipenv only be available during the build, to reduce slug size.
+	/app/.heroku/python/bin/pip install --quiet --disable-pip-version-check --no-cache-dir "pipenv==${PIPENV_VERSION}"
+}
+
 # Previous versions of the buildpack used to cache the checksum of the lockfile to allow
 # for skipping pipenv install if the lockfile was unchanged. However, this is not always safe
 # to do (the lockfile can refer to dependencies that can change independently of the lockfile,
 # for example, when using a local non-editable file dependency), so we no longer ever skip
 # install, and instead defer to pipenv to determine whether install is actually a no-op.
-rm -f .heroku/python/Pipfile.lock.sha256
-
-if [[ -f Pipfile ]]; then
-	pipenv_install_start_time=$(nowms)
-	meta_set "package_manager" "pipenv"
-
-	# Skip installing dependencies using pip later.
-	# TODO: Stop leaking this env var into subshells such as post_compile hooks.
-	export SKIP_PIP_INSTALL=1
-
-	# Set Pip env vars
-	# This reads certain environment variables set on the Heroku app config
-	# and makes them accessible to the pip install process.
+function pipenv::install_dependencies() {
+	# Make select pip config vars set on the Heroku app available to the pip used by Pipenv.
+	# TODO: Expose all config vars (after suitable checks are added for unsafe env vars).
 	#
 	# PIP_EXTRA_INDEX_URL allows for an alternate pypi URL to be used.
-	if [[ -r "$ENV_DIR/PIP_EXTRA_INDEX_URL" ]]; then
-		PIP_EXTRA_INDEX_URL="$(cat "$ENV_DIR/PIP_EXTRA_INDEX_URL")"
+	if [[ -r "${ENV_DIR}/PIP_EXTRA_INDEX_URL" ]]; then
+		PIP_EXTRA_INDEX_URL="$(cat "${ENV_DIR}/PIP_EXTRA_INDEX_URL")"
 		export PIP_EXTRA_INDEX_URL
 	fi
 
-	PIPENV_VERSION=$(get_requirement_version 'pipenv')
-	meta_set "pipenv_version" "${PIPENV_VERSION}"
-
-	/app/.heroku/python/bin/pip install --quiet --disable-pip-version-check --no-cache-dir "pipenv==${PIPENV_VERSION}"
-
 	# Install the test dependencies, for CI.
 	# TODO: This is currently inconsistent with the non-test path, since it assumes (but doesn't check for) a lockfile.
-	if [[ -n "$INSTALL_TEST" ]]; then
-		meta_set "pipenv_has_lockfile" "true"
-		puts-step "Installing test dependencies"
+	if [[ -n "${INSTALL_TEST}" ]]; then
+		puts-step "Installing test dependencies with Pipenv"
 		/app/.heroku/python/bin/pipenv install --dev --system --deploy --extra-pip-args='--src=/app/.heroku/src' 2>&1 | cleanup | indent
 
 	# Install the dependencies.
 	elif [[ ! -f Pipfile.lock ]]; then
-		meta_set "pipenv_has_lockfile" "false"
-		puts-step "Installing dependencies with Pipenv ${PIPENV_VERSION}"
+		puts-step "Installing dependencies with Pipenv"
 		/app/.heroku/python/bin/pipenv install --system --skip-lock --extra-pip-args='--src=/app/.heroku/src' 2>&1 | indent
 
 	else
-		meta_set "pipenv_has_lockfile" "true"
-		puts-step "Installing dependencies with Pipenv ${PIPENV_VERSION}"
+		puts-step "Installing dependencies with Pipenv"
 		/app/.heroku/python/bin/pipenv install --system --deploy --extra-pip-args='--src=/app/.heroku/src' 2>&1 | indent
 	fi
-
-	meta_time "dependencies_install_duration" "${pipenv_install_start_time}"
-fi
+}
diff --git a/lib/utils.sh b/lib/utils.sh
new file mode 100644
index 000000000..fb7da23a6
--- /dev/null
+++ b/lib/utils.sh
@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+# Python bundles Pip within its standard library, which we can use to install our chosen
+# pip version from PyPI, saving us from having to download the usual pip bootstrap script.
+function utils::bundled_pip_module_path() {
+	local build_dir="${1}"
+
+	# We have to use a glob since the bundled wheel filename contains the pip version, which
+	# differs between Python versions. We also have to handle the case where there are multiple
+	# matching pip wheels, since in some versions of Python (eg 3.9.0) multiple versions of pip
+	# were accidentally bundled upstream. Note: This implementation relies upon `nullglob` being
+	# set, which is the case thanks to the `bin/utils` that was run earlier.
+	local bundled_pip_wheel_list=("${build_dir}"/.heroku/python/lib/python*/ensurepip/_bundled/pip-*.whl)
+	local bundled_pip_wheel="${bundled_pip_wheel_list[0]}"
+
+	if [[ -z "${bundled_pip_wheel}" ]]; then
+		display_error "Error: Failed to locate the bundled pip wheel."
+		meta_set "failure_reason" "bundled-pip-not-found"
+		return 1
+	fi
+
+	echo "${bundled_pip_wheel}/pip"
+}
+
+function utils::abort_internal_error() {
+	local message="${1}"
+	display_error "Internal error: ${message} (line $(caller || true))."
+	exit 1
+}
diff --git a/spec/hatchet/ci_spec.rb b/spec/hatchet/ci_spec.rb
index ad8053abf..f6403c1ac 100644
--- a/spec/hatchet/ci_spec.rb
+++ b/spec/hatchet/ci_spec.rb
@@ -96,10 +96,11 @@
                  To use a different version, see: https://devcenter.heroku.com/articles/python-runtimes
           -----> Installing python-#{DEFAULT_PYTHON_VERSION}
           -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          -----> Installing test dependencies
+          -----> Installing Pipenv #{PIPENV_VERSION}
+          -----> Installing SQLite3
+          -----> Installing test dependencies with Pipenv
                  Installing dependencies from Pipfile.lock \\(.+\\)...
                  Installing dependencies from Pipfile.lock \\(.+\\)...
-          -----> Installing SQLite3
           -----> Skipping Django collectstatic since the env var DISABLE_COLLECTSTATIC is set.
           -----> Running post-compile hook
           CI=true
@@ -115,7 +116,6 @@
           PIP_NO_PYTHON_VERSION_WARNING=1
           PKG_CONFIG_PATH=/app/.heroku/vendor/lib/pkg-config:/app/.heroku/python/lib/pkg-config:
           PYTHONUNBUFFERED=1
-          SKIP_PIP_INSTALL=1
           -----> Inline app detected
           LANG=en_US.UTF-8
           LD_LIBRARY_PATH=/app/.heroku/vendor/lib:/app/.heroku/python/lib:
@@ -152,10 +152,11 @@
                  To use a different version, see: https://devcenter.heroku.com/articles/python-runtimes
           -----> Using cached install of python-#{DEFAULT_PYTHON_VERSION}
           -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          -----> Installing test dependencies
+          -----> Installing Pipenv #{PIPENV_VERSION}
+          -----> Installing SQLite3
+          -----> Installing test dependencies with Pipenv
                  Installing dependencies from Pipfile.lock \\(.+\\)...
                  Installing dependencies from Pipfile.lock \\(.+\\)...
-          -----> Installing SQLite3
           -----> Skipping Django collectstatic since the env var DISABLE_COLLECTSTATIC is set.
           -----> Running post-compile hook
         REGEX
diff --git a/spec/hatchet/pip_spec.rb b/spec/hatchet/pip_spec.rb
index 5351975e0..b57910e60 100644
--- a/spec/hatchet/pip_spec.rb
+++ b/spec/hatchet/pip_spec.rb
@@ -220,7 +220,7 @@
           remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
           remote: -----> Installing SQLite3
           remote: -----> Installing requirements with pip
-          remote:        Obtaining file:///tmp/build_.* \\(from -r requirements.txt \\(line 1\\)\\)
+          remote:        Obtaining file:///tmp/build_.*
           remote:          Preparing metadata \\(setup.py\\): started
           remote:          Preparing metadata \\(setup.py\\): finished with status 'done'
           remote:        .+
diff --git a/spec/hatchet/pipenv_spec.rb b/spec/hatchet/pipenv_spec.rb
index ccd5dee93..f8b810b3f 100644
--- a/spec/hatchet/pipenv_spec.rb
+++ b/spec/hatchet/pipenv_spec.rb
@@ -10,9 +10,10 @@
         remote: -----> Using Python version specified in Pipfile.lock
         remote: -----> Installing python-#{python_version}
         remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-        remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
-        remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
+        remote: -----> Installing Pipenv #{PIPENV_VERSION}
         remote: -----> Installing SQLite3
+        remote: -----> Installing dependencies with Pipenv
+        remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
       REGEX
     end
   end
@@ -49,7 +50,9 @@
           remote:        To use a different version, see: https://devcenter.heroku.com/articles/python-runtimes
           remote: -----> Installing python-#{DEFAULT_PYTHON_VERSION}
           remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
+          remote: -----> Installing Pipenv #{PIPENV_VERSION}
+          remote: -----> Installing SQLite3
+          remote: -----> Installing dependencies with Pipenv
           remote:        The flag --skip-lock has been reintroduced \\(but is not recommended\\).  Without 
           remote:        the lock resolver it is difficult to manage multiple package indexes, and hash 
           remote:        checking is not provided.  However it can help manage installs with current 
@@ -57,7 +60,6 @@
           remote:        Pipfile.lock not found, creating...
           .+
           remote:        Installing dependencies from Pipfile...
-          remote: -----> Installing SQLite3
         REGEX
       end
     end
@@ -78,9 +80,10 @@
           remote:        To use a different version, see: https://devcenter.heroku.com/articles/python-runtimes
           remote: -----> Installing python-#{DEFAULT_PYTHON_VERSION}
           remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
-          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
+          remote: -----> Installing Pipenv #{PIPENV_VERSION}
           remote: -----> Installing SQLite3
+          remote: -----> Installing dependencies with Pipenv
+          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
           remote: -----> Inline app detected
           remote: LANG=en_US.UTF-8
           remote: LD_LIBRARY_PATH=/app/.heroku/vendor/lib:/app/.heroku/python/lib:
@@ -195,9 +198,10 @@
             remote:  !     
             remote: -----> Installing python-#{LATEST_PYTHON_3_8}
             remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-            remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
-            remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
+            remote: -----> Installing Pipenv #{PIPENV_VERSION}
             remote: -----> Installing SQLite3
+            remote: -----> Installing dependencies with Pipenv
+            remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
           REGEX
         end
       end
@@ -260,9 +264,10 @@
           remote:  !     
           remote: -----> Installing python-3.12.2
           remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
-          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
+          remote: -----> Installing Pipenv #{PIPENV_VERSION}
           remote: -----> Installing SQLite3
+          remote: -----> Installing dependencies with Pipenv
+          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
         REGEX
       end
     end
@@ -319,9 +324,10 @@
           remote: -----> Using Python version specified in runtime.txt
           remote: -----> Installing python-#{LATEST_PYTHON_3_12}
           remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
-          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
+          remote: -----> Installing Pipenv #{PIPENV_VERSION}
           remote: -----> Installing SQLite3
+          remote: -----> Installing dependencies with Pipenv
+          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
         REGEX
       end
     end
@@ -340,9 +346,10 @@
           remote:        To use a different version, see: https://devcenter.heroku.com/articles/python-runtimes
           remote: -----> Using cached install of python-#{DEFAULT_PYTHON_VERSION}
           remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
-          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
+          remote: -----> Installing Pipenv #{PIPENV_VERSION}
           remote: -----> Installing SQLite3
+          remote: -----> Installing dependencies with Pipenv
+          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
           remote: -----> Discovering process types
         REGEX
       end
@@ -366,9 +373,10 @@
           remote:        To use a different version, see: https://devcenter.heroku.com/articles/python-runtimes
           remote: -----> Using cached install of python-#{DEFAULT_PYTHON_VERSION}
           remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
-          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
+          remote: -----> Installing Pipenv #{PIPENV_VERSION}
           remote: -----> Installing SQLite3
+          remote: -----> Installing dependencies with Pipenv
+          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
           remote: -----> Discovering process types
         REGEX
       end
@@ -385,9 +393,10 @@
           remote: -----> Using Python version specified in Pipfile.lock
           remote: -----> Installing python-#{LATEST_PYTHON_3_12}
           remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
-          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
+          remote: -----> Installing Pipenv #{PIPENV_VERSION}
           remote: -----> Installing SQLite3
+          remote: -----> Installing dependencies with Pipenv
+          remote:        Installing dependencies from Pipfile.lock \\(.+\\)...
         REGEX
       end
     end
@@ -404,7 +413,9 @@
           remote:        To use a different version, see: https://devcenter.heroku.com/articles/python-runtimes
           remote: -----> Installing python-#{DEFAULT_PYTHON_VERSION}
           remote: -----> Installing pip #{PIP_VERSION}, setuptools #{SETUPTOOLS_VERSION} and wheel #{WHEEL_VERSION}
-          remote: -----> Installing dependencies with Pipenv #{PIPENV_VERSION}
+          remote: -----> Installing Pipenv #{PIPENV_VERSION}
+          remote: -----> Installing SQLite3
+          remote: -----> Installing dependencies with Pipenv
           remote:        Your Pipfile.lock \\(.+\\) is out of date.  Expected: \\(.+\\).
           remote:        .+
           remote:        ERROR:: Aborting deploy