@@ -17,6 +17,7 @@ permissions:
 
 env:
   FORCE_COLOR: 1
+  OPENSSL_VER: 3.5.7
 
 jobs:
   build-san-reusable:
@@ -38,28 +39,55 @@ jobs:
       run: |
         sudo ./.github/workflows/posix-deps-apt.sh
         # On ubuntu-26.04 image, clang is clang-21 by default
-
-        if [ "${SANITIZER}" = "TSan" ]; then
-          # Reduce ASLR to avoid TSan crashing
-          sudo sysctl -w vm.mmap_rnd_bits=28
-        fi
-
-    - name: Sanitizer option setup
-      run: |
-        if [ "${SANITIZER}" = "TSan" ]; then
-          echo "TSAN_OPTIONS=${SAN_LOG_OPTION} suppressions=${GITHUB_WORKSPACE}/Tools/tsan/suppressions${{
-              fromJSON(inputs.free-threading)
-              && '_free_threading'
-              || ''
-            }}.txt handle_segv=0" >> "$GITHUB_ENV"
-        else
-          echo "UBSAN_OPTIONS=${SAN_LOG_OPTION} halt_on_error=1 suppressions=${GITHUB_WORKSPACE}/Tools/ubsan/suppressions.txt" >> "$GITHUB_ENV"
-        fi
         echo "CC=clang" >> "$GITHUB_ENV"
         echo "CXX=clang++" >> "$GITHUB_ENV"
+    - name: TSan option setup
+      if: inputs.sanitizer == 'TSan'
+      run: |
+        sudo sysctl -w vm.mmap_rnd_bits=28  # Reduce ASLR to avoid TSan crashing
+
+        echo "MULTISSL_DIR=${GITHUB_WORKSPACE}/multissl" >> "$GITHUB_ENV"
+        echo "OPENSSL_DIR=${GITHUB_WORKSPACE}/multissl/openssl/${OPENSSL_VER}" >> "$GITHUB_ENV"
+        echo "TSAN_OPTIONS=${SAN_LOG_OPTION} suppressions=${GITHUB_WORKSPACE}/Tools/tsan/suppressions${SUPPRESSIONS_SUFFIX}.txt handle_segv=0" >> "$GITHUB_ENV"
       env:
-        SANITIZER: ${{ inputs.sanitizer }}
         SAN_LOG_OPTION: log_path=${{ github.workspace }}/san_log
+        SUPPRESSIONS_SUFFIX: >-
+          ${{
+            fromJSON(inputs.free-threading)
+            && '_free_threading'
+            || ''
+          }}
+    - name: UBSan option setup
+      if: inputs.sanitizer != 'TSan'
+      run: >-
+        echo
+        "UBSAN_OPTIONS=${SAN_LOG_OPTION}
+        halt_on_error=1
+        suppressions=${GITHUB_WORKSPACE}/Tools/ubsan/suppressions.txt"
+        >> "$GITHUB_ENV"
+      env:
+        SAN_LOG_OPTION: log_path=${{ github.workspace }}/san_log
+    - name: Add ccache to PATH
+      run: |
+        echo "PATH=/usr/lib/ccache:$PATH" >> "$GITHUB_ENV"
+    - name: 'Restore OpenSSL build (TSan)'
+      id: cache-openssl
+      if: inputs.sanitizer == 'TSan'
+      uses: actions/cache@668228422ae6a00e4ad889ee87cd7109ec5666a7 # v5.0.4
+      with:
+        path: ./multissl/openssl/${{ env.OPENSSL_VER }}
+        key: ${{ env.IMAGE_OS_VERSION }}-multissl-openssl-tsan-${{ env.OPENSSL_VER }}
+    - name: Install OpenSSL (TSan)
+      if: >-
+        inputs.sanitizer == 'TSan'
+        && steps.cache-openssl.outputs.cache-hit != 'true'
+      run: >-
+        python3 Tools/ssl/multissltests.py
+        --steps=library
+        --base-directory="${MULTISSL_DIR}"
+        --openssl="${OPENSSL_VER}"
+        --system=Linux
+        --tsan
     - name: Configure CPython
       run: >-
         ./configure
@@ -70,6 +98,7 @@ jobs:
           || '--with-undefined-behavior-sanitizer --with-strict-overflow'
         }}
         --with-pydebug
+        ${{ inputs.sanitizer == 'TSan' && '--with-openssl="$OPENSSL_DIR" --with-openssl-rpath=auto' || '' }}
         ${{ fromJSON(inputs.free-threading) && '--disable-gil' || '' }}
     - name: Build CPython
       run: make -j4
 
@@ -163,6 +163,12 @@
     dest='keep_sources',
     help="Keep original sources for debugging."
 )
+parser.add_argument(
+    '--tsan',
+    action='store_true',
+    dest='tsan',
+    help="Build with thread sanitizer. (Disables fips in OpenSSL 3.x)."
+)
 
 
 class AbstractBuilder(object):
@@ -317,6 +323,8 @@ def _build_src(self, config_args=()):
         """Now build openssl"""
         log.info("Running build in {}".format(self.build_dir))
         cwd = self.build_dir
+        if self.args.tsan:
+            config_args += ("-fsanitize=thread",)
         cmd = [
             "./config", *config_args,
             "shared", "--debug",