diff --git a/libcxx/utils/ci/buildkite-pipeline.yml b/libcxx/utils/ci/buildkite-pipeline.yml
--- a/libcxx/utils/ci/buildkite-pipeline.yml
+++ b/libcxx/utils/ci/buildkite-pipeline.yml
@@ -466,6 +466,19 @@
           limit: 2
     timeout_in_minutes: 120
 
+  - label: "Unstable ABI"
+    command: "libcxx/utils/ci/run-buildbot generic-abi-unstable"
+    artifact_paths:
+      - "**/test-results.xml"
+    agents:
+      queue: "libcxx-builders"
+      os: "linux"
+    retry:
+      automatic:
+        - exit_status: -1  # Agent was lost
+          limit: 2
+    timeout_in_minutes: 120
+
   # Other non-testing CI jobs
   - label: "Benchmarks"
     command: "libcxx/utils/ci/run-buildbot benchmarks"
diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -390,6 +390,13 @@
                    -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in"
     check-runtimes
 ;;
+generic-abi-unstable)
+    clean
+    generate-cmake -DLIBCXX_TEST_CONFIG="llvm-libc++-shared.cfg.in" \
+                   -DLIBUNWIND_TEST_CONFIG="llvm-libunwind-shared.cfg.in" \
+                   -DLIBCXX_ABI_UNSTABLE=ON
+    check-runtimes
+;;
 apple-system)
     clean