diff --git a/.github/workflows/verify-pipeline.yml b/.github/workflows/verify-pipeline.yml
index 3e647e43..87a3728c 100644
--- a/.github/workflows/verify-pipeline.yml
+++ b/.github/workflows/verify-pipeline.yml
@@ -58,6 +58,20 @@ jobs:
           print('Reference signal metadata validated.')
           "
 
+      - name: Quantization sweep (diagnostic — cross-microarch precision)
+        working-directory: archive/v1
+        env:
+          OMP_NUM_THREADS: "1"
+          OPENBLAS_NUM_THREADS: "1"
+          MKL_NUM_THREADS: "1"
+          VECLIB_MAXIMUM_THREADS: "1"
+          NUMEXPR_NUM_THREADS: "1"
+        run: |
+          for d in 6 5 4 3 2; do
+            h=$(PROOF_HASH_DECIMALS=$d python data/proof/verify.py --generate-hash 2>/dev/null | grep -i 'Computed:' | sed 's/.*Computed:[[:space:]]*//')
+            echo "SWEEP d=$d $h"
+          done
+
       - name: Run pipeline verification
         working-directory: archive/v1
         env:
diff --git a/archive/v1/data/proof/verify.py b/archive/v1/data/proof/verify.py
index f771f285..4f63f7a8 100644
--- a/archive/v1/data/proof/verify.py
+++ b/archive/v1/data/proof/verify.py
@@ -185,7 +185,14 @@ def frame_to_csi_data(frame, signal_meta):
 # observed pipeline-amplified ULP drift and is still far below any meaningful
 # signal change (CSI phase precision is ~1e-3 rad; PSD bins differ by orders
 # of magnitude). Round to this precision, then hash.
-HASH_QUANTIZATION_DECIMALS = 6
+#
+# NOTE: 6 decimals collapses the divergence *across Linux microarchitectures*
+# but NOT Windows-vs-Linux, where the pocketfft/BLAS difference exceeds 1e-6 on
+# a few elements that then straddle the 6th-decimal rounding boundary. The
+# precision is overridable via PROOF_HASH_DECIMALS so it can be coarsened to a
+# value that is boundary-stable across *all* platforms (Windows + Linux + macOS)
+# while staying far below any signal-meaningful change.
+HASH_QUANTIZATION_DECIMALS = int(os.environ.get("PROOF_HASH_DECIMALS", "6"))
 
 
 def features_to_bytes(features):