diff --git a/.github/workflows/build-test.yml b/.github/workflows/build-test.yml
index 09f3113..b383db9 100644
--- a/.github/workflows/build-test.yml
+++ b/.github/workflows/build-test.yml
@@ -1,46 +1,45 @@
-name: Tests (Asan)
-
-on:
-  push:
-    branches: [ main ]
-  pull_request:
-    branches: [ main ]
-
-jobs:
-  build-and-test:
-    runs-on: ubuntu-latest
-    
-    steps:
-    - uses: actions/checkout@v4
-
-    - name: Create Build Directory
-      run: mkdir build
-
-    - name: Configure CMake
-      working-directory: ./build
-      run: cmake -DDISABLE_AVX512=ON -DENABLE_ADDRESS_SANITIZER=ON -DPIXIE_BENCHMARKS=OFF ..
-
-    - name: Build Project
-      working-directory: ./build
-      run: make -j
-
-    - name: Run Unittests
-      working-directory: ./build
-      run: ./unittests
-    
-    - name: Run LOUDS Tree Tests
-      working-directory: ./build
-      run: ./louds_tree_tests
-
-    - name: Run Benchmark Tests
-      working-directory: ./build
-      run: ./benchmark_tests
-
-    #   TODO: fix RmM tests under Asan
-    # - name: Run RmM Tree Tests
-    #   working-directory: ./build
-    #   run: ./test_rmm
-  
+name: Tests (Asan)
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build-and-test:
+    runs-on: ubuntu-latest
+    
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Create Build Directory
+      run: mkdir build
+
+    - name: Configure CMake
+      working-directory: ./build
+      run: cmake -DDISABLE_AVX512=ON -DENABLE_ADDRESS_SANITIZER=ON -DPIXIE_BENCHMARKS=OFF ..
+
+    - name: Build Project
+      working-directory: ./build
+      run: make -j
+
+    - name: Run Unittests
+      working-directory: ./build
+      run: ./unittests
+    
+    - name: Run LOUDS Tree Tests
+      working-directory: ./build
+      run: ./louds_tree_tests
+
+    - name: Run Benchmark Tests
+      working-directory: ./build
+      run: ./benchmark_tests
+
+    - name: Run RmM Tree Tests
+      working-directory: ./build
+      run: ./test_rmm
+  
   build-and-test-with-SDE:
     runs-on: ubuntu-latest
     timeout-minutes: 60
@@ -92,4 +91,4 @@ jobs:
           exit 0
         fi
         exit $rc
-
+
diff --git a/include/pixie/rmm_tree.h b/include/pixie/rmm_tree.h
index 45caee0..fe8bbe7 100644
--- a/include/pixie/rmm_tree.h
+++ b/include/pixie/rmm_tree.h
@@ -270,26 +270,41 @@ class RmMTree {
     if (node_pattern10_count[node_index] < target_pattern_rank) {
       return npos;
     }
+    const size_t tree_size = segment_size_bits.size() - 1;
     size_t segment_base = 0;
     while (node_index < first_leaf_index) {
-      const size_t left_child = node_index << 1, right_child = left_child | 1;
+      const size_t left_child = node_index << 1;
+      const size_t left_segment_size =
+          (left_child <= tree_size) ? segment_size_bits[left_child] : 0;
+      if (left_segment_size == 0) {
+        return npos;
+      }
+
+      const size_t left_count = node_pattern10_count[left_child];
+      if (left_count >= target_pattern_rank) {
+        node_index = left_child;
+        continue;
+      }
+
+      size_t remaining_rank = target_pattern_rank - left_count;
+      const size_t right_child = left_child | 1;
+      const bool has_right =
+          (right_child <= tree_size) && (segment_size_bits[right_child] != 0);
+      if (!has_right) {
+        return npos;
+      }
+
       const size_t crossing_pattern =
           (node_last_bit[left_child] == 1 && node_first_bit[right_child] == 0)
               ? 1u
               : 0u;
-      if (node_pattern10_count[left_child] >= target_pattern_rank) {
-        node_index = left_child;
-        continue;
-      }
-      size_t remaining_rank =
-          target_pattern_rank - node_pattern10_count[left_child];
       if (crossing_pattern) {
         if (remaining_rank == 1) {
-          return segment_base + segment_size_bits[left_child] - 1;
+          return segment_base + left_segment_size - 1;
         }
         --remaining_rank;
       }
-      segment_base += segment_size_bits[left_child];
+      segment_base += left_segment_size;
       node_index = right_child;
       target_pattern_rank = remaining_rank;
     }
diff --git a/scripts/coverage_report.sh b/scripts/coverage_report.sh
index af51064..0820856 100755
--- a/scripts/coverage_report.sh
+++ b/scripts/coverage_report.sh
@@ -12,7 +12,7 @@ cmake --build --preset coverage
 "${BUILD_DIR}/test_rmm"
 
 cd "${BUILD_DIR}"
-find . -name "*.gcno" -o -name "*.gcda" > gcov_files.txt
+find . -name "*.gcda" > gcov_files.txt
 while read -r f; do
   case "${f}" in
     *"/third_party/"*|*"/src/benchmarks/"*)
diff --git a/src/tests/test_rmm.cpp b/src/tests/test_rmm.cpp
index 59cc667..569a6f7 100644
--- a/src/tests/test_rmm.cpp
+++ b/src/tests/test_rmm.cpp
@@ -511,6 +511,200 @@ TEST(RmMEdgeCases, EmptyInput) {
   EXPECT_EQ(rm.range_max_query_pos(0, 0), nv.range_max_query_pos(0, 0));
 }
 
+static void expect_rank_select_equal(const pixie::RmMTree& rm,
+                                     const NaiveRmM& nv,
+                                     size_t n) {
+  for (size_t x = 0; x <= n; ++x) {
+    EXPECT_EQ(rm.rank1(x), nv.rank1(x)) << "rank1 x=" << x;
+    EXPECT_EQ(rm.rank0(x), nv.rank0(x)) << "rank0 x=" << x;
+    EXPECT_EQ(rm.rank10(x), nv.rank10(x)) << "rank10 x=" << x;
+  }
+
+  const size_t ones = nv.rank1(n);
+  const size_t zeros = n - ones;
+  const size_t pairs10 = (n >= 2 ? nv.rank10(n) : 0);
+
+  for (size_t k = 1; k <= ones + 1; ++k) {
+    EXPECT_EQ(rm.select1(k), nv.select1(k)) << "select1 k=" << k;
+  }
+  for (size_t k = 1; k <= zeros + 1; ++k) {
+    EXPECT_EQ(rm.select0(k), nv.select0(k)) << "select0 k=" << k;
+  }
+  for (size_t k = 1; k <= pairs10 + 1; ++k) {
+    EXPECT_EQ(rm.select10(k), nv.select10(k)) << "select10 k=" << k;
+  }
+}
+
+static void expect_range_ops_equal(const pixie::RmMTree& rm,
+                                   const NaiveRmM& nv,
+                                   size_t n) {
+  if (n == 0) {
+    return;
+  }
+  std::mt19937_64 rng(42);
+  std::uniform_int_distribution<size_t> pos(0, n - 1);
+  std::uniform_int_distribution<size_t> k_dist;
+  for (int t = 0; t < 512; ++t) {
+    size_t i = pos(rng);
+    size_t j = pos(rng);
+    if (i > j) {
+      std::swap(i, j);
+    }
+
+    EXPECT_EQ(rm.range_min_query_pos(i, j), nv.range_min_query_pos(i, j));
+    EXPECT_EQ(rm.range_min_query_val(i, j), nv.range_min_query_val(i, j));
+    EXPECT_EQ(rm.range_max_query_pos(i, j), nv.range_max_query_pos(i, j));
+    EXPECT_EQ(rm.range_max_query_val(i, j), nv.range_max_query_val(i, j));
+
+    size_t cnt = nv.mincount(i, j);
+    EXPECT_EQ(rm.mincount(i, j), cnt);
+    k_dist.param(std::uniform_int_distribution<size_t>::param_type(1, cnt + 1));
+    size_t k = k_dist(rng);
+    EXPECT_EQ(rm.minselect(i, j, k), nv.minselect(i, j, k));
+  }
+}
+
+TEST(RmMEdgeCases, MultiwordPattern10AcrossWordBoundaries) {
+  const size_t n = 640;
+  std::string bits(n, '1');
+
+  for (size_t i = 0; i + 1 < n; i += 3) {
+    bits[i] = '1';
+    bits[i + 1] = '0';
+  }
+  for (size_t boundary = 63; boundary + 1 < n; boundary += 64) {
+    bits[boundary] = '1';
+    bits[boundary + 1] = '0';
+  }
+
+  pixie::RmMTree rm(bits, /*leaf_block_bits=*/256);
+  NaiveRmM nv(bits);
+
+  expect_rank_select_equal(rm, nv, n);
+  expect_range_ops_equal(rm, nv, n);
+}
+
+TEST(RmMEdgeCases, PartialLastLeafSelects) {
+  const size_t n = 600;
+
+  std::string mostly_zero(n, '0');
+  for (size_t i = 576; i < n; ++i) {
+    mostly_zero[i] = '1';
+  }
+  pixie::RmMTree rm_select1(mostly_zero, /*leaf_block_bits=*/256);
+  NaiveRmM nv_select1(mostly_zero);
+  expect_rank_select_equal(rm_select1, nv_select1, n);
+
+  std::string mostly_one(n, '1');
+  for (size_t i = 576; i < n; ++i) {
+    mostly_one[i] = '0';
+  }
+  pixie::RmMTree rm_select0(mostly_one, /*leaf_block_bits=*/256);
+  NaiveRmM nv_select0(mostly_one);
+  expect_rank_select_equal(rm_select0, nv_select0, n);
+}
+
+TEST(RmMEdgeCases, Select10OnIncompleteInternalNode) {
+  constexpr size_t leaf_block_bits = 256;
+  const size_t n = (leaf_block_bits * 2) + 32;  // exactly 3 leaves
+  std::string bits(n, '1');
+
+  // Put all "10" patterns into the last (partial) leaf.
+  for (size_t i = leaf_block_bits * 2; i + 1 < n; i += 4) {
+    bits[i] = '1';
+    bits[i + 1] = '0';
+  }
+
+  pixie::RmMTree rm(bits, leaf_block_bits);
+  NaiveRmM nv(bits);
+
+  const size_t pairs10 = nv.rank10(n);
+  ASSERT_GT(pairs10, 0u);
+  for (size_t k = 1; k <= pairs10 + 1; ++k) {
+    EXPECT_EQ(rm.select10(k), nv.select10(k)) << "select10 k=" << k;
+  }
+}
+
+/**
+ * Invalid arguments should fail fast and return npos/0 as specified.
+ * Covers bad ranks, bad ranges and out-of-bounds BP navigation calls.
+ */
+TEST(RmMEdgeCases, InvalidArgumentsGuards) {
+  const size_t n = 600;
+  std::string bits(n, '1');
+  for (size_t i = 0; i < n; i += 5) {
+    bits[i] = '0';
+  }
+
+  pixie::RmMTree rm(bits, /*leaf_block_bits=*/256);
+
+  EXPECT_EQ(rm.select1(0), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.select0(0), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.select10(0), pixie::RmMTree::npos);
+
+  EXPECT_EQ(rm.fwdsearch(n, 0), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.bwdsearch(0, 0), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.bwdsearch(n + 1, 0), pixie::RmMTree::npos);
+
+  EXPECT_EQ(rm.range_min_query_pos(10, 9), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.range_min_query_pos(0, n), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.range_max_query_pos(10, 9), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.range_max_query_pos(0, n), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.range_min_query_val(10, 9), 0);
+  EXPECT_EQ(rm.range_max_query_val(10, 9), 0);
+  EXPECT_EQ(rm.mincount(10, 9), 0);
+  EXPECT_EQ(rm.minselect(10, 9, 1), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.minselect(0, n - 1, 0), pixie::RmMTree::npos);
+
+  EXPECT_EQ(rm.close(n), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.open(0), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.open(n + 1), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.enclose(0), pixie::RmMTree::npos);
+  EXPECT_EQ(rm.enclose(n + 1), pixie::RmMTree::npos);
+}
+
+/**
+ * bit_count is larger than the provided words buffer.
+ * Verifies that words beyond the provided buffer are treated as zeros after
+ * resize.
+ */
+TEST(RmMEdgeCases, WordsConstructorResizesInputStorage) {
+  std::vector<std::uint64_t> words = {0xAAAAAAAAAAAAAAAAull};
+  const size_t bit_count = 300;
+
+  pixie::RmMTree rm(words, bit_count);
+  NaiveRmM nv(words, bit_count);
+
+  expect_rank_select_equal(rm, nv, bit_count);
+  expect_range_ops_equal(rm, nv, bit_count);
+}
+
+/**
+ * Same bitvector built through different configuration paths (auto vs explicit
+ * leaf size, different overhead caps, and words-based constructor). Query
+ * results must be identical.
+ */
+TEST(RmMEdgeCases, ExplicitBuildParametersAndOverheadCap) {
+  std::mt19937_64 rng(42);
+  const size_t n = 128;
+  const std::string bits = random_bits(rng, n);
+  NaiveRmM nv(bits);
+
+  pixie::RmMTree rm_auto(bits, /*leaf_block_bits=*/0, /*max_overhead=*/1.f);
+  pixie::RmMTree rm_explicit(bits, /*leaf_block_bits=*/512,
+                             /*max_overhead=*/2.f);
+  auto words = pack_words_lsb_first(bits);
+  pixie::RmMTree rm_words(words, n, /*leaf_block_bits=*/256,
+                          /*max_overhead=*/1.f);
+
+  expect_rank_select_equal(rm_auto, nv, n);
+  expect_range_ops_equal(rm_auto, nv, n);
+  expect_rank_select_equal(rm_explicit, nv, n);
+  expect_range_ops_equal(rm_explicit, nv, n);
+  expect_rank_select_equal(rm_words, nv, n);
+  expect_range_ops_equal(rm_words, nv, n);
+}
+
 TEST(RmMTreeStress, LongRandom) {
   Limits L;
   L.OPS_PER_CASE = 2000;