diff --git a/t/meson.build b/t/meson.build
index a5531df415..551c3036c0 100644
--- a/t/meson.build
+++ b/t/meson.build
@@ -131,6 +131,7 @@ integration_tests = [
   't0210-trace2-normal.sh',
   't0211-trace2-perf.sh',
   't0212-trace2-event.sh',
+  't0213-trace2-ancestry.sh',
   't0300-credentials.sh',
   't0301-credential-cache.sh',
   't0302-credential-store.sh',
diff --git a/t/t0210-trace2-normal.sh b/t/t0210-trace2-normal.sh
index 96c68f65df..7e1e7af862 100755
--- a/t/t0210-trace2-normal.sh
+++ b/t/t0210-trace2-normal.sh
@@ -74,8 +74,9 @@ scrub_normal () {
 	#      This line is only emitted when RUNTIME_PREFIX is defined,
 	#      so just omit it for testing purposes.
 	#
-	#   4. 'cmd_ancestry' is not implemented everywhere, so for portability's
-	#      sake, skip it when parsing normal.
+	#   4. 'cmd_ancestry' output depends on how the test is run and
+	#      is not relevant to the features we are testing here.
+	#      Ancestry tests are covered in t0213-trace2-ancestry.sh instead.
 	sed \
 		-e 's/elapsed:[0-9]*\.[0-9][0-9]*\([eE][-+]\{0,1\}[0-9][0-9]*\)\{0,1\}/elapsed:_TIME_/g' \
 		-e "s/^start '[^']*' \(.*\)/start _EXE_ \1/" \
diff --git a/t/t0213-trace2-ancestry.sh b/t/t0213-trace2-ancestry.sh
new file mode 100755
index 0000000000..a2b9536da8
--- /dev/null
+++ b/t/t0213-trace2-ancestry.sh
@@ -0,0 +1,180 @@
+#!/bin/sh
+
+test_description='test trace2 cmd_ancestry event'
+
+. ./test-lib.sh
+
+# Turn off any inherited trace2 settings for this test.
+sane_unset GIT_TRACE2 GIT_TRACE2_PERF GIT_TRACE2_EVENT
+sane_unset GIT_TRACE2_BRIEF
+sane_unset GIT_TRACE2_CONFIG_PARAMS
+
+# Add t/helper directory to PATH so that we can use a relative
+# path to run nested instances of test-tool.exe (see 004child).
+# This helps with HEREDOC comparisons later.
+TTDIR="$GIT_BUILD_DIR/t/helper/" && export TTDIR
+PATH="$TTDIR:$PATH" && export PATH
+
+# The 400ancestry helper spawns a child process so that the child
+# sees "test-tool" in its process ancestry.  We capture only the
+# child's trace2 output to a file.
+#
+# The tests use git commands that spawn child git processes (e.g.,
+# alias resolution) to create a controlled multi-level process tree.
+# Because cmd_ancestry walks the real process tree, processes will
+# also report ancestors above "test-tool" that depend on the test
+# runner environment (e.g., bash, make, tmux).  The filter functions
+# below truncate the ancestry at "test-tool", discarding anything
+# above it, so only the controlled portion is verified.
+#
+# On platforms without a real procinfo implementation (the stub),
+# no cmd_ancestry event is emitted.  We detect this at runtime and
+# skip the format-specific tests accordingly.
+
+# Determine if cmd_ancestry is supported on this platform.
+test_expect_success 'detect cmd_ancestry support' '
+	test_when_finished "rm -f trace.detect" &&
+	GIT_TRACE2_BRIEF=1 GIT_TRACE2="$(pwd)/trace.detect" \
+		test-tool trace2 001return 0 &&
+	if grep -q "^cmd_ancestry" trace.detect
+	then
+		test_set_prereq TRACE2_ANCESTRY
+	fi
+'
+
+# Filter functions for each trace2 target format.
+#
+# Each extracts cmd_ancestry events, strips format-specific syntax,
+# and truncates the ancestor list at the outermost "test-tool"
+# (or "test-tool.exe" on Windows), discarding any higher-level
+# (uncontrolled) ancestors.
+#
+# Output is a space-separated list of ancestor names, one line per
+# cmd_ancestry event, with the immediate parent listed first:
+#
+#   test-tool                          (or: test-tool.exe)
+#   git test-tool                      (or: git.exe test-tool.exe)
+#   git test-tool test-tool            (or: git.exe test-tool.exe test-tool.exe)
+
+if test_have_prereq MINGW
+then
+	TT=test-tool$X
+else
+	TT=test-tool
+fi
+
+filter_ancestry_normal () {
+	sed -n '/^cmd_ancestry/{
+		s/^cmd_ancestry //
+		s/ <- / /g
+		s/\(.*'"$TT"'\) .*/\1/
+		p
+	}'
+}
+
+filter_ancestry_perf () {
+	sed -n '/cmd_ancestry/{
+		s/.*ancestry:\[//
+		s/\]//
+		s/\(.*'"$TT"'\) .*/\1/
+		p
+	}'
+}
+
+filter_ancestry_event () {
+	sed -n '/"cmd_ancestry"/{
+		s/.*"ancestry":\[//
+		s/\].*//
+		s/"//g
+		s/,/ /g
+		s/\(.*'"$TT"'\) .*/\1/
+		p
+	}'
+}
+
+# On Windows (MINGW) when running with the bin-wrappers, we also see "sh.exe" in
+# the ancestry. We must therefore account for this expected ancestry element in
+# the expected output of the tests.
+if test_have_prereq MINGW && test -z "$no_bin_wrappers"; then
+	SH_TT="sh$X $TT"
+else
+	SH_TT="$TT"
+fi
+
+# Git alias resolution spawns the target command as a child process.
+# Using "git -c alias.xyz=version xyz" creates a two-level chain:
+#
+#   test-tool (400ancestry)
+#     -> git (resolves alias xyz -> version)
+#          -> git (version)
+#
+# Both git processes are instrumented and emit cmd_ancestry.  After
+# filtering out ancestors above test-tool, we get:
+#
+#   test-tool                 (from git alias resolver)
+#   git test-tool             (from git version)
+
+test_expect_success TRACE2_ANCESTRY 'normal: git alias chain, 2 levels' '
+	test_when_finished "rm -f trace.normal actual expect" &&
+	test-tool trace2 400ancestry normal "$(pwd)/trace.normal" \
+		git -c alias.xyz=version xyz &&
+	filter_ancestry_normal <trace.normal >actual &&
+	cat >expect <<-EOF &&
+	$SH_TT
+	git$X $SH_TT
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success TRACE2_ANCESTRY 'perf: git alias chain, 2 levels' '
+	test_when_finished "rm -f trace.perf actual expect" &&
+	test-tool trace2 400ancestry perf "$(pwd)/trace.perf" \
+		git -c alias.xyz=version xyz &&
+	filter_ancestry_perf <trace.perf >actual &&
+	cat >expect <<-EOF &&
+	$SH_TT
+	git$X $SH_TT
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success TRACE2_ANCESTRY 'event: git alias chain, 2 levels' '
+	test_when_finished "rm -f trace.event actual expect" &&
+	test-tool trace2 400ancestry event "$(pwd)/trace.event" \
+		git -c alias.xyz=version xyz &&
+	filter_ancestry_event <trace.event >actual &&
+	cat >expect <<-EOF &&
+	$SH_TT
+	git$X $SH_TT
+	EOF
+	test_cmp expect actual
+'
+
+# Use 004child to add a test-tool layer, creating a three-level chain:
+#
+#   test-tool (400ancestry)
+#     -> test-tool (004child)
+#          -> git (resolves alias xyz -> version)
+#               -> git (version)
+#
+# Three instrumented processes emit cmd_ancestry.  After filtering:
+#
+#   test-tool                  (from test-tool 004child)
+#   test-tool test-tool        (from git alias resolver)
+#   git test-tool test-tool    (from git version)
+
+test_expect_success TRACE2_ANCESTRY 'normal: deeper chain, 3 levels' '
+	test_when_finished "rm -f trace.normal actual expect" &&
+	test-tool trace2 400ancestry normal "$(pwd)/trace.normal" \
+		test-tool trace2 004child \
+			git -c alias.xyz=version xyz &&
+	filter_ancestry_normal <trace.normal >actual &&
+	cat >expect <<-EOF &&
+	$TT
+	$SH_TT $TT
+	git$X $SH_TT $TT
+	EOF
+	test_cmp expect actual
+'
+
+test_done