patch.diff

diff --git a/jolt-core/src/subprotocols/univariate_skip.rs b/jolt-core/src/subprotocols/univariate_skip.rs
index 1ab8322c..65ba6209 100644
--- a/jolt-core/src/subprotocols/univariate_skip.rs
+++ b/jolt-core/src/subprotocols/univariate_skip.rs
@@ -265,10 +265,21 @@ impl<F: JoltField, T: Transcript> UniSkipFirstRoundProof<F, T> {
             .uni_poly
             .check_sum_evals::<N, FIRST_ROUND_POLY_NUM_COEFFS>(input_claim);
         sumcheck_instance.cache_openings(opening_accumulator, &[r0]);
+
+        let expected_output = proof.uni_poly.evaluate(&r0);
+        let claimed_output = sumcheck_instance.expected_output_claim(opening_accumulator, &[r0]);
+
         opening_accumulator.flush_to_transcript(transcript);
 
         if !ok {
             Err(ProofVerifyError::UniSkipVerificationError)
+        } else if claimed_output != expected_output {
+            tracing::error!(
+                claimed_output = %claimed_output,
+                expected_output = %expected_output,
+                "Univariate-skip output claim mismatch"
+            );
+            Err(ProofVerifyError::UniSkipVerificationError)
         } else {
             Ok(r0)
         }
diff --git a/jolt-core/src/zkvm/spartan/outer.rs b/jolt-core/src/zkvm/spartan/outer.rs
index 62fba2ba..91b46762 100644
--- a/jolt-core/src/zkvm/spartan/outer.rs
+++ b/jolt-core/src/zkvm/spartan/outer.rs
@@ -331,10 +331,14 @@ impl<F: JoltField, T: Transcript, A: AbstractVerifierOpeningAccumulator<F>>
 
     fn expected_output_claim(
         &self,
-        _accumulator: &A,
+        accumulator: &A,
         _sumcheck_challenges: &[<F as JoltField>::Challenge],
     ) -> F {
-        unimplemented!("Unused for univariate skip")
+        let (_, claim) = accumulator.get_virtual_polynomial_opening(
+            VirtualPolynomial::UnivariateSkip,
+            SumcheckId::SpartanOuter,
+        );
+        claim
     }
 
     fn cache_openings(
diff --git a/jolt-core/src/zkvm/spartan/product.rs b/jolt-core/src/zkvm/spartan/product.rs
index 9504d09e..d38582ea 100644
--- a/jolt-core/src/zkvm/spartan/product.rs
+++ b/jolt-core/src/zkvm/spartan/product.rs
@@ -352,10 +352,14 @@ impl<F: JoltField, T: Transcript, A: AbstractVerifierOpeningAccumulator<F>>
 
     fn expected_output_claim(
         &self,
-        _accumulator: &A,
+        accumulator: &A,
         _sumcheck_challenges: &[<F as JoltField>::Challenge],
     ) -> F {
-        unimplemented!("Unused for univariate skip")
+        let (_, claim) = accumulator.get_virtual_polynomial_opening(
+            VirtualPolynomial::UnivariateSkip,
+            SumcheckId::SpartanProductVirtualization,
+        );
+        claim
     }
 
     fn cache_openings(