diff --git a/.github/workflows/R-CMD-check.yaml b/.github/workflows/R-CMD-check.yaml
index 4705d5a..2a55345 100644
--- a/.github/workflows/R-CMD-check.yaml
+++ b/.github/workflows/R-CMD-check.yaml
@@ -20,12 +20,19 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        # Ubuntu jobs pin to jammy (22.04): noble (24.04) ubuntu-latest
+        # source-builds the mirt -> ... -> stringfish chain, whose
+        # stringfish.so then fails to load with an Intel TBB ABI mismatch
+        # (undefined symbol tbb::...concurrent_vector_base_v3::internal_grow_by).
+        # P3M ships jammy binaries that avoid the source compile. Same pin as
+        # test-suite.yaml/test-fast.yaml and aFIPC's r.yml; revisit once P3M
+        # ships noble binaries. macOS/Windows are unaffected.
         config:
           - {os: macos-latest, r: 'release'}
           - {os: windows-latest, r: 'release'}
-          - {os: ubuntu-latest, r: 'devel', http-user-agent: 'release'}
-          - {os: ubuntu-latest, r: 'release'}
-          - {os: ubuntu-latest, r: 'oldrel-1'}
+          - {os: ubuntu-22.04, r: 'devel', http-user-agent: 'release'}
+          - {os: ubuntu-22.04, r: 'release'}
+          - {os: ubuntu-22.04, r: 'oldrel-1'}
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/test-fast.yaml b/.github/workflows/test-fast.yaml
index fa70edf..469fb2d 100644
--- a/.github/workflows/test-fast.yaml
+++ b/.github/workflows/test-fast.yaml
@@ -11,7 +11,12 @@ permissions:
 
 jobs:
   test-fast:
-    runs-on: ubuntu-latest
+    # Pin to jammy (22.04): noble (24.04) ubuntu-latest source-builds the
+    # mirt -> ... -> stringfish chain, whose stringfish.so then fails to load
+    # with an Intel TBB ABI mismatch, aborting `R CMD INSTALL .`. P3M ships
+    # jammy binaries that avoid the source compile. Same pin as test-suite.yaml
+    # and aFIPC's r.yml; revisit once P3M ships noble binaries.
+    runs-on: ubuntu-22.04
 
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
diff --git a/.github/workflows/test-suite.yaml b/.github/workflows/test-suite.yaml
index d447513..2427c23 100644
--- a/.github/workflows/test-suite.yaml
+++ b/.github/workflows/test-suite.yaml
@@ -21,7 +21,16 @@ permissions:
 
 jobs:
   test-suite:
-    runs-on: ubuntu-latest
+    # Pin to jammy (22.04): Posit P3M ships precompiled Linux binaries for the
+    # current R release on jammy, but not for noble (24.04, today's
+    # ubuntu-latest). On noble, setup-r-dependencies source-builds the
+    # mirt -> SimDesign -> qs -> stringfish chain, and the source-built
+    # stringfish.so fails to load with an Intel TBB ABI mismatch (undefined
+    # symbol tbb::internal::concurrent_vector_base_v3::internal_grow_by),
+    # aborting `R CMD INSTALL .` / `library(kaefa)` before the suite can run.
+    # Jammy binaries avoid the source compile entirely; same pin as aFIPC's
+    # r.yml. Revisit once P3M ships noble binaries for this chain.
+    runs-on: ubuntu-22.04
     timeout-minutes: 180
 
     env: