diff --git a/.github/workflows/R-CMD-check.yaml b/.github/workflows/R-CMD-check.yaml
index 4705d5a..ca02cfe 100644
--- a/.github/workflows/R-CMD-check.yaml
+++ b/.github/workflows/R-CMD-check.yaml
@@ -42,6 +42,16 @@ jobs:
           http-user-agent: ${{ matrix.config.http-user-agent }}
           use-public-rspm: true
 
+      # ponytail: source-build stringfish BEFORE dependency setup — packages built
+      # from source during install (e.g. SimDesign) load it at build time and die
+      # on the broken prebuilt binary (oneTBB ABI skew). Drop with the step below.
+      # repos= must be a real source repo: RSPM serves prebuilt Linux binaries via
+      # source-style URLs, so type="source" against RSPM does NOT recompile.
+      - name: Source-build stringfish (RcppParallel oneTBB ABI skew)
+        run: >-
+          Rscript -e 'install.packages(c("RcppParallel", "stringfish"), type = "source",
+          repos = "https://cloud.r-project.org")'
+
       - uses: r-lib/actions/setup-r-dependencies@6f6e5bc62fba3a704f74e7ad7ef7676c5c6a2590 # v2
         with:
           extra-packages: |
@@ -49,6 +59,16 @@ jobs:
             any::testthat
           needs: check
 
+      # ponytail: CRAN/RSPM binary skew — prebuilt binaries (stringfish, qs2, ...) lag
+      # RcppParallel's oneTBB update (undefined tbb::internal / tbb::task symbols).
+      # Rebuild everything LinkingTo RcppParallel from source so it links the installed
+      # copy. Drop once upstream binaries re-sync.
+      - name: Rebuild RcppParallel-linked packages from source (oneTBB ABI skew)
+        run: >-
+          Rscript -e 'r <- "https://cloud.r-project.org"; install.packages("RcppParallel", type = "source", repos = r);
+          bad <- tools::dependsOnPkgs("RcppParallel", dependencies = "LinkingTo");
+          if (length(bad)) install.packages(bad, type = "source", repos = r)'
+
       - name: Run Zh formula regression tests
         run: |
           Rscript -e 'install.packages(".", repos = NULL, type = "source")'
diff --git a/.github/workflows/test-fast.yaml b/.github/workflows/test-fast.yaml
index fa70edf..ee046af 100644
--- a/.github/workflows/test-fast.yaml
+++ b/.github/workflows/test-fast.yaml
@@ -20,11 +20,31 @@ jobs:
         with:
           use-public-rspm: true
 
+      # ponytail: source-build stringfish BEFORE dependency setup — packages built
+      # from source during install (e.g. SimDesign) load it at build time and die
+      # on the broken prebuilt binary (oneTBB ABI skew). Drop with the step below.
+      # repos= must be a real source repo: RSPM serves prebuilt Linux binaries via
+      # source-style URLs, so type="source" against RSPM does NOT recompile.
+      - name: Source-build stringfish (RcppParallel oneTBB ABI skew)
+        run: >-
+          Rscript -e 'install.packages(c("RcppParallel", "stringfish"), type = "source",
+          repos = "https://cloud.r-project.org")'
+
       - uses: r-lib/actions/setup-r-dependencies@6f6e5bc62fba3a704f74e7ad7ef7676c5c6a2590 # v2
         with:
           extra-packages: any::testthat
           needs: check
 
+      # ponytail: CRAN/RSPM binary skew — prebuilt binaries (stringfish, qs2, ...) lag
+      # RcppParallel's oneTBB update (undefined tbb::internal / tbb::task symbols).
+      # Rebuild everything LinkingTo RcppParallel from source so it links the installed
+      # copy. Drop once upstream binaries re-sync.
+      - name: Rebuild RcppParallel-linked packages from source (oneTBB ABI skew)
+        run: >-
+          Rscript -e 'r <- "https://cloud.r-project.org"; install.packages("RcppParallel", type = "source", repos = r);
+          bad <- tools::dependsOnPkgs("RcppParallel", dependencies = "LinkingTo");
+          if (length(bad)) install.packages(bad, type = "source", repos = r)'
+
       - name: Install kaefa package for fast tests
         run: R CMD INSTALL .
 
diff --git a/.github/workflows/test-suite.yaml b/.github/workflows/test-suite.yaml
index d447513..407a8fa 100644
--- a/.github/workflows/test-suite.yaml
+++ b/.github/workflows/test-suite.yaml
@@ -36,11 +36,31 @@ jobs:
         with:
           use-public-rspm: true
 
+      # ponytail: source-build stringfish BEFORE dependency setup — packages built
+      # from source during install (e.g. SimDesign) load it at build time and die
+      # on the broken prebuilt binary (oneTBB ABI skew). Drop with the step below.
+      # repos= must be a real source repo: RSPM serves prebuilt Linux binaries via
+      # source-style URLs, so type="source" against RSPM does NOT recompile.
+      - name: Source-build stringfish (RcppParallel oneTBB ABI skew)
+        run: >-
+          Rscript -e 'install.packages(c("RcppParallel", "stringfish"), type = "source",
+          repos = "https://cloud.r-project.org")'
+
       - uses: r-lib/actions/setup-r-dependencies@6f6e5bc62fba3a704f74e7ad7ef7676c5c6a2590 # v2
         with:
           extra-packages: any::testthat
           needs: check
 
+      # ponytail: CRAN/RSPM binary skew — prebuilt binaries (stringfish, qs2, ...) lag
+      # RcppParallel's oneTBB update (undefined tbb::internal / tbb::task symbols).
+      # Rebuild everything LinkingTo RcppParallel from source so it links the installed
+      # copy. Drop once upstream binaries re-sync.
+      - name: Rebuild RcppParallel-linked packages from source (oneTBB ABI skew)
+        run: >-
+          Rscript -e 'r <- "https://cloud.r-project.org"; install.packages("RcppParallel", type = "source", repos = r);
+          bad <- tools::dependsOnPkgs("RcppParallel", dependencies = "LinkingTo");
+          if (length(bad)) install.packages(bad, type = "source", repos = r)'
+
       - name: Install kaefa package
         run: R CMD INSTALL .