diff --git a/.github/workflows/jit.yml b/.github/workflows/jit.yml
index e63fe9e1284a01..2f024ad52f3091 100644
--- a/.github/workflows/jit.yml
+++ b/.github/workflows/jit.yml
@@ -35,6 +35,9 @@ jobs:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:
           persist-credentials: false
+      - name: Install dependencies
+        run: |
+          sudo ./.github/workflows/posix-deps-apt.sh
       - name: Build tier two interpreter
         run: |
           ./configure --enable-experimental-jit=interpreter --with-pydebug
@@ -152,6 +155,9 @@ jobs:
       - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
         with:
           python-version: '3.11'
+      - name: Install dependencies
+        run: |
+          sudo ./.github/workflows/posix-deps-apt.sh
       - name: Build
         run: |
           sudo bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)" ./llvm.sh ${{ env.LLVM_VERSION }}
@@ -188,6 +194,9 @@ jobs:
       - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
         with:
           python-version: '3.11'
+      - name: Install dependencies
+        run: |
+          sudo ./.github/workflows/posix-deps-apt.sh
       - name: Build
         run: |
           sudo bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)" ./llvm.sh ${{ env.LLVM_VERSION }}
diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
index 3cf69718e63b28..1a5e5fe2fc0be6 100644
--- a/Doc/whatsnew/3.15.rst
+++ b/Doc/whatsnew/3.15.rst
@@ -81,6 +81,7 @@ Summary -- Release highlights
   <whatsnew315-unpacking-in-comprehensions>`
 * :pep:`686`: :ref:`Python now uses UTF-8 as the default encoding
   <whatsnew315-utf8-default>`
+* :pep:`829`: :ref:`Package startup configuration files <whatsnew315-startup-files>`
 * :pep:`728`: :ref:`TypedDict with typed extra items <whatsnew315-typeddict>`
 * :pep:`747`: :ref:`Annotating type forms with TypeForm
   <whatsnew315-typeform>`
@@ -94,7 +95,6 @@ Summary -- Release highlights
 * :ref:`Improved error messages <whatsnew315-improved-error-messages>`
 * :ref:`The official Windows 64-bit binaries now use the tail-calling interpreter
   <whatsnew315-windows-tail-calling-interpreter>`
-* :pep:`829`: Package Startup Configuration Files
 
 New features
 ============
@@ -452,6 +452,31 @@ agen() for x in a)``.
 
 (Contributed by Adam Hartz in :gh:`143055`.)
 
+.. _whatsnew315-startup-files:
+
+:pep:`829`: Package startup configuration files
+-----------------------------------------------
+
+Loaded by the :mod:`site` module when ``-S`` is not given, :ref:`.pth files <site-pth-files>`
+can contain lines that both extend :data:`sys.path` and execute arbitrary code
+when the line starts with ``import`` (followed by a space or tab).  The latter
+functionality can be problematic, since it is difficult to know exactly what
+gets executed when Python starts up.
+
+As a step towards improving the ability to audit pre-start executable code,
+Python 3.15 introduces :ref:`.start files <site-start-files>` which contain entry point
+specifications of the form ``pkg.mod:callable`` where ``pkg.mod`` is the
+import path to the given callable.  When Python starts up, the callable is
+located and called with no arguments.
+
+``import`` lines in :file:`.pth` files are silently deprecated.  When a
+matching :file:`.start` file is found, ``import`` lines in :file:`.pth` files
+are ignored.  There is no change to :data:`sys.path` extension lines in
+:file:`.pth` files.
+
+(Contributed by Barry Warsaw in :gh:`148641`.)
+
+
 .. _whatsnew315-abi3t:
 
 :pep:`803` -- Stable ABI for Free-Threaded Builds
diff --git a/Lib/test/test_gdb/test_jit.py b/Lib/test/test_gdb/test_jit.py
index ea88d7b0a1fe75..7cb604f8aee8c3 100644
--- a/Lib/test/test_gdb/test_jit.py
+++ b/Lib/test/test_gdb/test_jit.py
@@ -4,9 +4,18 @@
 import sys
 import unittest
 
+from test.support import import_helper
+
 from .util import setup_module, DebuggerTests
 
 
+_testinternalcapi = import_helper.import_module("_testinternalcapi")
+NATIVE_JIT_ENABLED = (
+    hasattr(sys, "_jit")
+    and sys._jit.is_enabled()
+    and _testinternalcapi.get_jit_backend() == "jit"
+)
+
 JIT_SAMPLE_SCRIPT = os.path.join(os.path.dirname(__file__), "gdb_jit_sample.py")
 # In batch GDB, break in builtin_id() while it is running under JIT,
 # then repeatedly "finish" until the selected frame is the JIT executor.
@@ -62,14 +71,14 @@ def setUpModule():
 # Python/jit_unwind.c, and the synthetic EH-frame is only implemented for
 # x86_64 and AArch64 (a #error fires otherwise). Skip cleanly on other
 # platforms or architectures instead of producing timeouts / empty backtraces.
-# is_enabled() implies is_available() and also implies that the runtime has
-# JIT execution active; interpreter-only tier 2 builds don't hit this path.
+# sys._jit.is_enabled() is true for --enable-experimental-jit=interpreter,
+# but these tests need native JIT code and a py::jit:executor frame.
 @unittest.skipUnless(sys.platform == "linux",
                      "GDB JIT interface is only implemented for Linux + ELF")
 @unittest.skipUnless(platform.machine() in ("x86_64", "aarch64"),
                      "GDB JIT CFI emitter only supports x86_64 and AArch64")
-@unittest.skipUnless(hasattr(sys, "_jit") and sys._jit.is_enabled(),
-                     "requires a JIT-enabled build with JIT execution active")
+@unittest.skipUnless(NATIVE_JIT_ENABLED,
+                     "requires native JIT execution active")
 class JitBacktraceTests(DebuggerTests):
     def get_stack_trace(self, **kwargs):
         # These tests validate the JIT-relevant part of the backtrace via