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fix(bb): clamp BatchMergeProver degree-check loop to fix nightly debug SIGABRT #23077

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Merged
federicobarbacovi merged 3 commits into from
May 8, 2026
Merged

fix(bb): clamp BatchMergeProver degree-check loop to fix nightly debug SIGABRT #23077

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ace676e
fix(bb): clamp BatchMergeProver degree-check loop to fix nightly debu…
AztecBot May 8, 2026
fcb061b
Fix test
federicobarbacovi May 8, 2026
34ea69e
Merge branch 'merge-train/barretenberg' into claudebox/fix-bb-debug-b…
federicobarbacovi May 8, 2026
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17 changes: 11 additions & 6 deletions barretenberg/cpp/src/barretenberg/goblin/batch_merge.test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,8 @@ enum class FaultMode : uint8_t {
PADDING_NOT_INFINITY, // padded slot sends non-zero shift size and non-zero commitment/eval
SHIFT_SIZE_MINUS_ONE, // send k-1 as shift size for a subtable polynomial of size k
ZK_TABLE_DEGREE_TOO_HIGH, // zk table has degree above verifier hard-coded ZK shift
ZERO_SUBTABLES_CLAIM // send 0 as number of subtables
ZERO_SUBTABLES_CLAIM, // send 0 as number of subtables,
TOO_MANY_SUBTABLES, // send a number of subtables above the max that the verifier is configured for
};

void populate_subtable(const std::shared_ptr<ECCOpQueue>& op_queue, size_t num_ops)
Expand Down Expand Up @@ -238,17 +239,20 @@ class TweakableBatchMergeProver : public BatchMergeProver {
}

// Step 6: degree-check poly
bool is_too_many_subtables = flattened_cols.size() > num_degree_check_challenges;
if (is_too_many_subtables) {
if (fault_mode == FaultMode::TOO_MANY_SUBTABLES) {
// This is the case in which we test that if the prover sends more columns than the max number of tables
// then the verifier rejects
degree_check_challenges.push_back(degree_check_challenges.back() * degree_check_challenge);
size_t diff = flattened_cols.size() - num_degree_check_challenges;
for (size_t idx = 0; idx < diff * NUM_WIRES; ++idx) {
// Add challenges for the extra columns sent by the prover
degree_check_challenges.push_back(degree_check_challenges.back() * degree_check_challenge);
}
}

Polynomial degree_check_poly =
compute_degree_check_polynomial(flattened_cols, degree_check_challenges, max_shift_size);

if (is_too_many_subtables) {
if (fault_mode == FaultMode::TOO_MANY_SUBTABLES) {
// Remove the extra challenge added above to keep the degree check poly consistent with the rest of the
// proof
degree_check_challenges.pop_back();
Expand All @@ -257,6 +261,7 @@ class TweakableBatchMergeProver : public BatchMergeProver {
if (fault_mode == FaultMode::BAD_DEGREE_CHECK_POLY && !degree_check_poly.is_empty()) {
degree_check_poly.at(0) += FF(1);
}

transcript->send_to_verifier("DEGREE_CHECK_POLY", pcs_commitment_key.commit(degree_check_poly));

// Step 7
Expand Down Expand Up @@ -487,7 +492,7 @@ TYPED_TEST(BatchMergeTests, TooManySubtablesFails)
} else {
BB_DISABLE_ASSERTS();
auto op_queue = make_op_queue_with_n_subtables(TestFixture::NumSubtables + 1);
auto res = TestFixture::prove_and_verify(op_queue);
auto res = TestFixture::prove_and_verify(op_queue, FaultMode::TOO_MANY_SUBTABLES);
EXPECT_FALSE(res.reduction_ok); // Caught by product check
EXPECT_FALSE(res.pairing_ok); // Verifier uses fewer commitments than the one sent
if constexpr (TestFixture::IsRecursive) {
Expand Down
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