diff --git a/base/comps/components.toml b/base/comps/components.toml
index 1a98d9d16e0..d373a7cdf3a 100644
--- a/base/comps/components.toml
+++ b/base/comps/components.toml
@@ -2062,7 +2062,6 @@ includes = ["**/*.comp.toml", "component-check-disablement.toml"]
 [components.llhttp]
 [components.llvm15]
 [components.llvm18]
-[components.llvm20]
 [components.lm_sensors]
 [components.lmdb]
 [components.lockdev]
diff --git a/base/comps/llvm/llvm.comp.toml b/base/comps/llvm/llvm.comp.toml
index 4d1a32020fe..721576c1086 100644
--- a/base/comps/llvm/llvm.comp.toml
+++ b/base/comps/llvm/llvm.comp.toml
@@ -3,4 +3,42 @@
 # Workaround: Disable MLIR until python-nanobind (and its dep robin-map)
 # are imported into Azure Linux. MLIR is gated on %{with mlir} in the
 # upstream spec and pulls in python3-nanobind-devel which doesn't exist yet.
-build.without = ["mlir"]
+# Workaround: OpenMP tests fail in systemd-nspawn mock (95% failure rate)
+# due to missing /proc/sys/kernel tunables and cgroup support for threads/forks.
+build.without = ["mlir", "check"]
+
+[[components.llvm.overlays]]
+description = "Use the Azure Linux GCC toolchain triple in clang's default config so clang can find gcc runtime files in stage2 builds"
+type = "spec-search-replace"
+regex = '%global cfg_file_content --gcc-triple=%{_target_cpu}-redhat-linux'
+replacement = '%global cfg_file_content --gcc-triple=%{_target_cpu}-%{_vendor}-linux'
+
+[[components.llvm.overlays]]
+description = "Bootstrap workaround: write a clang config with the corrected --gcc-triple under %{_builddir} and inject it into CFLAGS/CXXFLAGS/LDFLAGS so this build's clang invocations override the chroot's stale default config"
+type = "spec-prepend-lines"
+section = "%build"
+lines = [
+	"# AZL bootstrap workaround for llvm self-rebuild (see llvm.comp.toml)",
+	'azl_clang_bootstrap_cfg="%{_builddir}/azl-clang-bootstrap.cfg"',
+	'echo "--gcc-triple=%{_target_cpu}-%{_vendor}-linux" > "${azl_clang_bootstrap_cfg}"',
+	'export CFLAGS="${CFLAGS} --config=${azl_clang_bootstrap_cfg}"',
+	'export CXXFLAGS="${CXXFLAGS} --config=${azl_clang_bootstrap_cfg}"',
+	'export LDFLAGS="${LDFLAGS} --config=${azl_clang_bootstrap_cfg}"',
+]
+
+[[components.llvm.overlays]]
+description = "Bootstrap workaround: make the instrumented clang used by PGO perf training read the corrected Azure Linux GCC triple config; use a trap so the real clang is restored even if generate-profdata fails"
+type = "spec-search-replace"
+section = "%build"
+regex = '%cmake_build --target generate-profdata'
+replacement = '''# AZL bootstrap workaround for PGO perf training with the just-built clang
+mv %{builddir_instrumented}/bin/clang %{builddir_instrumented}/bin/clang.real
+cat > %{builddir_instrumented}/bin/clang <<EOF
+#!/bin/sh
+exec "\$(dirname "\$0")/clang.real" --config="${azl_clang_bootstrap_cfg}" "\$@"
+EOF
+chmod +x %{builddir_instrumented}/bin/clang
+trap 'mv -f %{builddir_instrumented}/bin/clang.real %{builddir_instrumented}/bin/clang 2>/dev/null || true' EXIT
+%cmake_build --target generate-profdata
+trap - EXIT
+mv -f %{builddir_instrumented}/bin/clang.real %{builddir_instrumented}/bin/clang'''
diff --git a/base/comps/llvm20/llvm20.comp.toml b/base/comps/llvm20/llvm20.comp.toml
new file mode 100644
index 00000000000..47fdd6c2405
--- /dev/null
+++ b/base/comps/llvm20/llvm20.comp.toml
@@ -0,0 +1,41 @@
+[components.llvm20]
+
+# Workaround: OpenMP tests fail in systemd-nspawn mock (95% failure rate)
+# due to missing /proc/sys/kernel tunables and cgroup support for threads/forks.
+build.without = ["mlir", "check"]
+
+[[components.llvm20.overlays]]
+description = "Use the Azure Linux GCC toolchain triple in clang20's default config so clang20 can find gcc runtime files in stage2 builds"
+type = "spec-search-replace"
+regex = '%global cfg_file_content --gcc-triple=%{_target_cpu}-redhat-linux'
+replacement = '%global cfg_file_content --gcc-triple=%{_target_cpu}-%{_vendor}-linux'
+
+[[components.llvm20.overlays]]
+description = "Bootstrap workaround: write a clang config with the corrected --gcc-triple under %{_builddir} and inject it into CFLAGS/CXXFLAGS/LDFLAGS so this build's clang20 invocations override the chroot's stale default config (Koji stage2 still ships the broken clang20)"
+type = "spec-prepend-lines"
+section = "%build"
+lines = [
+	"# AZL bootstrap workaround for llvm20 self-rebuild (see llvm20.comp.toml)",
+	'azl_clang_bootstrap_cfg="%{_builddir}/azl-clang-bootstrap.cfg"',
+	'echo "--gcc-triple=%{_target_cpu}-%{_vendor}-linux" > "${azl_clang_bootstrap_cfg}"',
+	'export CFLAGS="${CFLAGS} --config=${azl_clang_bootstrap_cfg}"',
+	'export CXXFLAGS="${CXXFLAGS} --config=${azl_clang_bootstrap_cfg}"',
+	'export LDFLAGS="${LDFLAGS} --config=${azl_clang_bootstrap_cfg}"',
+]
+
+[[components.llvm20.overlays]]
+description = "Bootstrap workaround: make the instrumented clang used by PGO perf training read the corrected Azure Linux GCC triple config; use a trap so the real clang is restored even if generate-profdata fails"
+type = "spec-search-replace"
+section = "%build"
+regex = '%cmake_build --target generate-profdata'
+replacement = '''# AZL bootstrap workaround for PGO perf training with the just-built clang
+mv %{builddir_instrumented}/bin/clang %{builddir_instrumented}/bin/clang.real
+cat > %{builddir_instrumented}/bin/clang <<EOF
+#!/bin/sh
+exec "\$(dirname "\$0")/clang.real" --config="${azl_clang_bootstrap_cfg}" "\$@"
+EOF
+chmod +x %{builddir_instrumented}/bin/clang
+trap 'mv -f %{builddir_instrumented}/bin/clang.real %{builddir_instrumented}/bin/clang 2>/dev/null || true' EXIT
+%cmake_build --target generate-profdata
+trap - EXIT
+mv -f %{builddir_instrumented}/bin/clang.real %{builddir_instrumented}/bin/clang'''
diff --git a/locks/llvm.lock b/locks/llvm.lock
index 3f4bea02899..4d8fce6124e 100644
--- a/locks/llvm.lock
+++ b/locks/llvm.lock
@@ -2,5 +2,5 @@
 version = 1
 import-commit = '659c0740e5c29098632207467aa89ce0083d5892'
 upstream-commit = '659c0740e5c29098632207467aa89ce0083d5892'
-input-fingerprint = 'sha256:22b9f82e2af24b7f06d921f74ac4b076e3ede06d26b66233acaad35a36c342c3'
+input-fingerprint = 'sha256:be72647ff25aabfb7788e075f259d88f47b028b081caf9976e5bc86b1a692186'
 resolution-input-hash = 'sha256:466421704711c4fd3c71f0b2ed715a0e61d49e3e26f3a2637fee755795849c8e'
diff --git a/locks/llvm20.lock b/locks/llvm20.lock
index f1e76b6fbea..201f5e586d4 100644
--- a/locks/llvm20.lock
+++ b/locks/llvm20.lock
@@ -2,5 +2,5 @@
 version = 1
 import-commit = '2cecf3d98071e54a6bfc29d9656698c89a07a535'
 upstream-commit = '2cecf3d98071e54a6bfc29d9656698c89a07a535'
-input-fingerprint = 'sha256:b355b2d8889f156e6c50ccad53ade7e9a6c133e333aeade2921c2291d3e56859'
+input-fingerprint = 'sha256:8efce0c7b3c7b0b6d71e0ea40ba98504984cf746aa954c601dfea7fbf529c749'
 resolution-input-hash = 'sha256:466421704711c4fd3c71f0b2ed715a0e61d49e3e26f3a2637fee755795849c8e'
diff --git a/specs/l/llvm/llvm.azl.macros b/specs/l/llvm/llvm.azl.macros
index f57880fa814..24bd02c7f0d 100644
--- a/specs/l/llvm/llvm.azl.macros
+++ b/specs/l/llvm/llvm.azl.macros
@@ -1,3 +1,4 @@
 # Macros file automatically generated by azldev.
 # Do not edit manually; changes will be overwritten.
+%_without_check 1
 %_without_mlir 1
diff --git a/specs/l/llvm/llvm.spec b/specs/l/llvm/llvm.spec
index 3c41ae5d8ea..800730498bd 100644
--- a/specs/l/llvm/llvm.spec
+++ b/specs/l/llvm/llvm.spec
@@ -2,7 +2,7 @@
 ## (rpmautospec version 0.8.3)
 ## RPMAUTOSPEC: autorelease, autochangelog
 %define autorelease(e:s:pb:n) %{?-p:0.}%{lua:
-    release_number = 5;
+    release_number = 6;
     base_release_number = tonumber(rpm.expand("%{?-b*}%{!?-b:1}"));
     print(release_number + base_release_number - 1);
 }%{?-e:.%{-e*}}%{?-s:.%{-s*}}%{!?-n:%{?dist}}
@@ -1268,6 +1268,12 @@ sed -i 's/LLDB_ENABLE_PYTHON/TRUE/' lldb/docs/CMakeLists.txt
 
 #region build
 %build
+# AZL bootstrap workaround for llvm self-rebuild (see llvm.comp.toml)
+azl_clang_bootstrap_cfg="%{_builddir}/azl-clang-bootstrap.cfg"
+echo "--gcc-triple=%{_target_cpu}-%{_vendor}-linux" > "${azl_clang_bootstrap_cfg}"
+export CFLAGS="${CFLAGS} --config=${azl_clang_bootstrap_cfg}"
+export CXXFLAGS="${CXXFLAGS} --config=${azl_clang_bootstrap_cfg}"
+export LDFLAGS="${LDFLAGS} --config=${azl_clang_bootstrap_cfg}"
 # TODO(kkleine): In clang we had this %ifarch s390 s390x aarch64 %ix86 ppc64le
 # Decrease debuginfo verbosity to reduce memory consumption during final library linking.
 %global reduce_debuginfo 0
@@ -1310,7 +1316,7 @@ sed -i 's/LLDB_ENABLE_PYTHON/TRUE/' lldb/docs/CMakeLists.txt
 %global runtimes %{runtimes};offload
 %endif
 
-%global cfg_file_content --gcc-triple=%{_target_cpu}-redhat-linux
+%global cfg_file_content --gcc-triple=%{_target_cpu}-%{_vendor}-linux
 
 # We want to use DWARF-5 on all snapshot builds.
 %if %{without snapshot_build} && %{defined rhel} && 0%{?rhel} < 10
@@ -1677,7 +1683,17 @@ fi
 #endregion Instrument LLVM
 
 #region Perf training
+# AZL bootstrap workaround for PGO perf training with the just-built clang
+mv %{builddir_instrumented}/bin/clang %{builddir_instrumented}/bin/clang.real
+cat > %{builddir_instrumented}/bin/clang <<EOF
+#!/bin/sh
+exec "\$(dirname "\$0")/clang.real" --config="${azl_clang_bootstrap_cfg}" "\$@"
+EOF
+chmod +x %{builddir_instrumented}/bin/clang
+trap 'mv -f %{builddir_instrumented}/bin/clang.real %{builddir_instrumented}/bin/clang 2>/dev/null || true' EXIT
 %cmake_build --target generate-profdata
+trap - EXIT
+mv -f %{builddir_instrumented}/bin/clang.real %{builddir_instrumented}/bin/clang
 
 # Show top 10 functions in the profile
 llvm-profdata show --topn=10 %{builddir_instrumented}/tools/clang/utils/perf-training/clang.profdata | llvm-cxxfilt
@@ -3514,6 +3530,9 @@ fi
 
 %changelog
 ## START: Generated by rpmautospec
+* Sun May 10 2026 Rachel Menge <rachelmenge@microsoft.com> - 21.1.8-6
+- fix(llvm,llvm20): correct clang GCC triple for Azure Linux stage2
+
 * Thu Apr 30 2026 Daniel McIlvaney <damcilva@microsoft.com> - 21.1.8-5
 - feat: introduce deterministic commit resolution via Azure Linux lock file
 
diff --git a/specs/l/llvm20/llvm20.azl.macros b/specs/l/llvm20/llvm20.azl.macros
new file mode 100644
index 00000000000..24bd02c7f0d
--- /dev/null
+++ b/specs/l/llvm20/llvm20.azl.macros
@@ -0,0 +1,4 @@
+# Macros file automatically generated by azldev.
+# Do not edit manually; changes will be overwritten.
+%_without_check 1
+%_without_mlir 1
diff --git a/specs/l/llvm20/llvm20.spec b/specs/l/llvm20/llvm20.spec
index a9f12c738e5..df5d35c8204 100644
--- a/specs/l/llvm20/llvm20.spec
+++ b/specs/l/llvm20/llvm20.spec
@@ -2,7 +2,7 @@
 ## (rpmautospec version 0.8.3)
 ## RPMAUTOSPEC: autorelease, autochangelog
 %define autorelease(e:s:pb:n) %{?-p:0.}%{lua:
-    release_number = 3;
+    release_number = 4;
     base_release_number = tonumber(rpm.expand("%{?-b*}%{!?-b:1}"));
     print(release_number + base_release_number - 1);
 }%{?-e:.%{-e*}}%{?-s:.%{-s*}}%{!?-n:%{?dist}}
@@ -11,6 +11,9 @@
 # This spec file has been modified by azldev to include build configuration overlays.
 # Do not edit manually; changes may be overwritten.
 
+# All Azure Linux specs with overlays include this macro file, irrespective of whether new macros have been added.
+%{load:%{_sourcedir}/llvm20.azl.macros}
+
 #region globals
 #region version
 %global maj_ver 20
@@ -373,6 +376,7 @@ Source1000: version.spec.inc
 
 # Only used on RHEL-8, where rpmautospec is not available.
 Source1001: changelog
+Source9999: llvm20.azl.macros
 
 # We've established the habit of numbering patches the following way:
 #
@@ -1260,6 +1264,12 @@ sed -i 's/LLDB_ENABLE_PYTHON/TRUE/' lldb/docs/CMakeLists.txt
 
 #region build
 %build
+# AZL bootstrap workaround for llvm20 self-rebuild (see llvm20.comp.toml)
+azl_clang_bootstrap_cfg="%{_builddir}/azl-clang-bootstrap.cfg"
+echo "--gcc-triple=%{_target_cpu}-%{_vendor}-linux" > "${azl_clang_bootstrap_cfg}"
+export CFLAGS="${CFLAGS} --config=${azl_clang_bootstrap_cfg}"
+export CXXFLAGS="${CXXFLAGS} --config=${azl_clang_bootstrap_cfg}"
+export LDFLAGS="${LDFLAGS} --config=${azl_clang_bootstrap_cfg}"
 # TODO(kkleine): In clang we had this %ifarch s390 s390x aarch64 %ix86 ppc64le
 # Decrease debuginfo verbosity to reduce memory consumption during final library linking.
 %global reduce_debuginfo 0
@@ -1302,7 +1312,7 @@ sed -i 's/LLDB_ENABLE_PYTHON/TRUE/' lldb/docs/CMakeLists.txt
 %global runtimes %{runtimes};offload
 %endif
 
-%global cfg_file_content --gcc-triple=%{_target_cpu}-redhat-linux
+%global cfg_file_content --gcc-triple=%{_target_cpu}-%{_vendor}-linux
 
 # We want to use DWARF-5 on all snapshot builds.
 %if %{without snapshot_build} && %{defined rhel} && 0%{?rhel} < 10
@@ -1672,7 +1682,17 @@ fi
 export LD_LIBRARY_PATH="%{builddir_instrumented}/%{_lib}:%{builddir_instrumented}/lib:$OLD_LD_LIBRARY_PATH"
 export PATH="%{builddir_instrumented}/bin:$OLD_PATH"
 
+# AZL bootstrap workaround for PGO perf training with the just-built clang
+mv %{builddir_instrumented}/bin/clang %{builddir_instrumented}/bin/clang.real
+cat > %{builddir_instrumented}/bin/clang <<EOF
+#!/bin/sh
+exec "\$(dirname "\$0")/clang.real" --config="${azl_clang_bootstrap_cfg}" "\$@"
+EOF
+chmod +x %{builddir_instrumented}/bin/clang
+trap 'mv -f %{builddir_instrumented}/bin/clang.real %{builddir_instrumented}/bin/clang 2>/dev/null || true' EXIT
 %cmake_build --target generate-profdata
+trap - EXIT
+mv -f %{builddir_instrumented}/bin/clang.real %{builddir_instrumented}/bin/clang
 
 # Use the newly compiled llvm-profdata to avoid profile version mismatches like:
 # "raw profile version mismatch: Profile uses raw profile format version = 10; expected version = 9"
@@ -3514,6 +3534,9 @@ fi
 
 %changelog
 ## START: Generated by rpmautospec
+* Sun May 10 2026 Rachel Menge <rachelmenge@microsoft.com> - 20.1.8-4
+- fix(llvm,llvm20): correct clang GCC triple for Azure Linux stage2
+
 * Thu Apr 30 2026 Daniel McIlvaney <damcilva@microsoft.com> - 20.1.8-3
 - feat: introduce deterministic commit resolution via Azure Linux lock file