diff --git a/.github/workflows/r.yml b/.github/workflows/r.yml
index cf2e656..54eef61 100644
--- a/.github/workflows/r.yml
+++ b/.github/workflows/r.yml
@@ -35,12 +35,33 @@ jobs:
           r-version: release
           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.
+      # repos= is explicit because R_PROFILE_USER=/dev/null blanks setup-r's repos.
+      - name: Source-build stringfish (RcppParallel oneTBB ABI skew)
+        run: >-
+          Rscript -e 'install.packages(c("RcppParallel", "stringfish"), type = "source",
+          repos = "https://cloud.r-project.org")'
+
       - name: Set up R package dependencies
         uses: r-lib/actions/setup-r-dependencies@d3c5be51b12e724e68f33216ca3c148b66d5f0b6
         with:
           extra-packages: any::rcmdcheck
           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 R CMD check
         uses: r-lib/actions/check-r-package@6f6e5bc62fba3a704f74e7ad7ef7676c5c6a2590
         with: