diff --git a/.circleci/config.yml b/.circleci/config.yml
index 3693ac0e..a325f692 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -7,6 +7,9 @@ orbs:
 commands:
   run-cibuildwheel:
     parameters:
+      cibw-config:  # environment variables
+        type: string
+        default: ""
       cibw-version:
         type: string
         default: 4.2.0  # latest as of August 2026
@@ -16,7 +19,7 @@ commands:
           shell: bash -eo pipefail
           command: |
             python -m pip install --user cibuildwheel==<< parameters.cibw-version >>
-            python -m cibuildwheel --output-dir dist
+            << parameters.cibw-config >> python -m cibuildwheel --output-dir dist
 
       - store_artifacts: &store-artifacts
           path: ./dist
@@ -122,7 +125,9 @@ jobs:
 
     steps:
       - checkout
-      - run-cibuildwheel
+      - run: choco install llvm -y
+      - run-cibuildwheel:
+          cibw-config: CIBW_ENVIRONMENT_PASS=CXX CXX=clang-cl
 
   python-sdist:
     docker:
@@ -407,7 +412,7 @@ workflows:
           name: cpp-gcc-<< matrix.gcc-version >>
           matrix:
             parameters:
-              gcc-version: ["12", "latest"]
+              gcc-version: ["14", "latest"]
       - cpp-macOS
       - serialization:
           requires:
diff --git a/dwave/optimization/include/dwave-optimization/common.hpp b/dwave/optimization/include/dwave-optimization/common.hpp
index bcbf7898..07344982 100644
--- a/dwave/optimization/include/dwave-optimization/common.hpp
+++ b/dwave/optimization/include/dwave-optimization/common.hpp
@@ -32,16 +32,3 @@ typedef std::int64_t ssize_t;
 #include <sys/types.h>  // for ssize_t
 
 #endif
-
-namespace dwave::optimization {
-
-// backport unreachable from c++23
-[[noreturn]] inline void unreachable() {
-#if defined(_MSC_VER) && !defined(__clang__)  // MSVC
-    __assume(false);
-#else  // GCC, Clang
-    __builtin_unreachable();
-#endif
-}
-
-}  // namespace dwave::optimization
diff --git a/dwave/optimization/include/dwave-optimization/iterators.hpp b/dwave/optimization/include/dwave-optimization/iterators.hpp
index f547459f..4ec2b545 100644
--- a/dwave/optimization/include/dwave-optimization/iterators.hpp
+++ b/dwave/optimization/include/dwave-optimization/iterators.hpp
@@ -19,6 +19,7 @@
 #include <concepts>
 #include <memory>
 #include <span>
+#include <utility>
 
 #include "dwave-optimization/common.hpp"  // for ssize_t
 #include "dwave-optimization/typing.hpp"
@@ -461,7 +462,7 @@ requires(
                 case FormatCharacter::signedlonglong_:
                     return *static_cast<const signed long long*>(ptr);
             }
-            unreachable();
+            std::unreachable();
         }
     }
 
diff --git a/dwave/optimization/include/dwave-optimization/nodes/testing.hpp b/dwave/optimization/include/dwave-optimization/nodes/testing.hpp
index 3954ff67..d079d00e 100644
--- a/dwave/optimization/include/dwave-optimization/nodes/testing.hpp
+++ b/dwave/optimization/include/dwave-optimization/nodes/testing.hpp
@@ -16,6 +16,7 @@
 
 #include <optional>
 #include <random>
+#include <utility>
 #include <vector>
 
 #include "dwave-optimization/array.hpp"
@@ -113,18 +114,18 @@ class DynamicArrayTestingNode : public ArrayOutputMixin<ArrayNode>, public Decis
         checkpoint_type& checkpoint
     ) const override {
         assert(false and "not implemented");
-        unreachable();
+        std::unreachable();
     }
     [[noreturn]] void assign_from_checkpoint(
         State& state,
         checkpoint_type&& checkpoint
     ) const override {
         assert(false and "not implemented");
-        unreachable();
+        std::unreachable();
     }
     [[noreturn]] virtual checkpoint_type checkpoint(State& state) const override {
         assert(false and "not implemented");
-        unreachable();
+        std::unreachable();
     }
 
     // State mutation methods *************************************************
@@ -185,7 +186,7 @@ class DynamicArrayTestingNode : public ArrayOutputMixin<ArrayNode>, public Decis
             case 2:
                 return set(state, rng);
             default:
-                unreachable();
+                std::unreachable();
         }
     }
 
diff --git a/dwave/optimization/src/array.cpp b/dwave/optimization/src/array.cpp
index 3484d30c..5f897f4d 100644
--- a/dwave/optimization/src/array.cpp
+++ b/dwave/optimization/src/array.cpp
@@ -241,8 +241,6 @@ std::vector<ssize_t> broadcast_shapes(
     std::vector<ssize_t> shape(std::max(lhs.size(), rhs.size()));
 
     // Walk backwards through the shapes, checking for dimension compatibility.
-    // Technically span::rbegin() etc are c++23 features but it seems to work on
-    // all the compilers we care about. Whereas the c++20 ranges::rbegin() etc do not.
     auto lit = lhs.rbegin();
     const auto lend = lhs.rend();
     auto rit = rhs.rbegin();
diff --git a/dwave/optimization/src/nodes/binaryop.cpp b/dwave/optimization/src/nodes/binaryop.cpp
index 78ee6535..5f3279b3 100644
--- a/dwave/optimization/src/nodes/binaryop.cpp
+++ b/dwave/optimization/src/nodes/binaryop.cpp
@@ -19,6 +19,7 @@
 #include <ranges>
 #include <stdexcept>
 #include <type_traits>
+#include <utility>
 #include <vector>
 
 #include "_state.hpp"
@@ -151,7 +152,7 @@ std::pair<double, double> calculate_values_minmax(const Array* lhs_ptr, const Ar
     }
 
     assert(false && "not implemeted yet");
-    unreachable();
+    std::unreachable();
 }
 
 template <class BinaryOp>
@@ -182,7 +183,7 @@ bool calculate_integral(const Array* lhs_ptr, const Array* rhs_ptr) {
     }
 
     assert(false && "not implemeted yet");
-    unreachable();
+    std::unreachable();
 }
 
 template <class BinaryOp>
@@ -294,7 +295,7 @@ void BinaryOpNode<BinaryOp>::initialize_state(State& state) const {
     } else {
         // this case is complicated we need to "stretch" dimensions into each other
         assert(false && "not yet implemented");
-        unreachable();
+        std::unreachable();
     }
 
     this->template emplace_data_ptr_<ArrayNodeStateData>(state, std::move(values));
@@ -427,7 +428,7 @@ void BinaryOpNode<BinaryOp>::propagate(State& state) const {
     } else {
         // this case is complicated we need to "stretch" dimensions into eachother
         assert(false && "not yet implemented");
-        unreachable();
+        std::unreachable();
     }
 
     if (ptr->diff().size()) Node::propagate(state);
@@ -512,7 +513,7 @@ SizeInfo binaryop_calculate_sizeinfo(
 
     // not possible for us to be dynamic and none of our predecessors to be
     assert(false && "not implemeted");
-    unreachable();
+    std::unreachable();
 }
 
 template <class BinaryOp>
diff --git a/dwave/optimization/src/nodes/collections.cpp b/dwave/optimization/src/nodes/collections.cpp
index bee598ca..099553ff 100644
--- a/dwave/optimization/src/nodes/collections.cpp
+++ b/dwave/optimization/src/nodes/collections.cpp
@@ -532,7 +532,7 @@ struct DisjointBitSetsNodeData_ : CheckpointableState, NodeStateData {
         }
 
         assert(false and "disjoint set elements must be in exactly one bit-set once");
-        unreachable();
+        std::unreachable();
     }
 
     void commit() {
diff --git a/dwave/optimization/src/nodes/creation.cpp b/dwave/optimization/src/nodes/creation.cpp
index 492ece3a..9d7cf54e 100644
--- a/dwave/optimization/src/nodes/creation.cpp
+++ b/dwave/optimization/src/nodes/creation.cpp
@@ -14,6 +14,7 @@
 
 #include "dwave-optimization/nodes/creation.hpp"
 
+#include <utility>
 #include <variant>
 
 #include "_state.hpp"
@@ -109,7 +110,7 @@ std::vector<double> arange(const ssize_t start, const ssize_t stop, const ssize_
         }
     } else {
         assert(false && "0 step not allowed");
-        unreachable();
+        std::unreachable();
     }
 
     return arange;
@@ -178,7 +179,7 @@ std::pair<double, double> calculate_values_minmax(
     }
 
     assert(false && "zero step not allowed");
-    unreachable();
+    std::unreachable();
 }
 
 const SizeInfo calculate_arange_sizeinfo(
@@ -226,7 +227,7 @@ const SizeInfo calculate_arange_sizeinfo(
         );
     } else {
         assert(false && "unreachable");
-        unreachable();
+        std::unreachable();
     }
 
     // Handles all cases EXCEPT the following: "Exactly one predecessor, it
@@ -423,7 +424,7 @@ void ARangeNode::propagate(State& state) const {
         }
     } else {
         assert(false && "zero step not allowed");
-        unreachable();
+        std::unreachable();
     }
 
     if (ptr->diff().size()) Node::propagate(state);
diff --git a/dwave/optimization/src/nodes/flow.cpp b/dwave/optimization/src/nodes/flow.cpp
index 52dc5847..0776410b 100644
--- a/dwave/optimization/src/nodes/flow.cpp
+++ b/dwave/optimization/src/nodes/flow.cpp
@@ -301,13 +301,8 @@ void WhereNode::initialize_state(State& state) const {
         std::vector<double> values;
         values.reserve(condition.size());
 
-        // zip would be very nice here...
-        for (
-            auto cit = condition.begin(), xit = x.begin(), yit = y.begin();
-            cit != std::default_sentinel;
-            ++cit, ++xit, ++yit
-        ) {
-            values.emplace_back((*cit) ? *xit : *yit);
+        for (const auto& [ci, xi, yi] : std::views::zip(condition, x, y)) {
+            values.emplace_back(ci ? xi : yi);
         }
 
         emplace_data_ptr_<WhereNodeData>(state, std::move(values));
diff --git a/dwave/optimization/src/nodes/indexing.cpp b/dwave/optimization/src/nodes/indexing.cpp
index 87988074..47542a91 100644
--- a/dwave/optimization/src/nodes/indexing.cpp
+++ b/dwave/optimization/src/nodes/indexing.cpp
@@ -17,6 +17,7 @@
 #include <algorithm>
 #include <ranges>
 #include <unordered_set>
+#include <utility>
 #include <variant>
 
 #include "_state.hpp"
@@ -781,7 +782,7 @@ void AdvancedIndexingNode::replace_predecessor_(ssize_t index, Node* node_ptr) {
     }
 
     assert(false and "should not be able to get here");
-    unreachable();
+    std::unreachable();
 }
 
 void AdvancedIndexingNode::revert(State& state) const {
@@ -1405,13 +1406,13 @@ SizeInfo basicindexing_calculate_sizeinfo(
         } else if (start < 0 && stop >= 0) {
             // -start:stop:step - imposes a nonlinear maximum size
             assert(false && "not linear, handled above");
-            unreachable();
+            std::unreachable();
         } else if (start < 0 && stop < 0) {
             // -start:-stop:step - imposes a maximum size
             sizeinfo.max = num_per_row * (std::max<ssize_t>(stop - start, 0) + step - 1) / step;
         } else {
             assert(false && "shouldn't be reachable");
-            unreachable();
+            std::unreachable();
         }
     }
 
diff --git a/dwave/optimization/src/nodes/lambda.cpp b/dwave/optimization/src/nodes/lambda.cpp
index b40ec9a5..75c87561 100644
--- a/dwave/optimization/src/nodes/lambda.cpp
+++ b/dwave/optimization/src/nodes/lambda.cpp
@@ -14,6 +14,8 @@
 
 #include "dwave-optimization/nodes/lambda.hpp"
 
+#include <utility>
+
 #include "_state.hpp"
 #include "dwave-optimization/array.hpp"
 #include "dwave-optimization/graph.hpp"
@@ -352,7 +354,7 @@ void AccumulateZipNode::propagate(State& state) const {
             data->emplace_back(val);
         } else {
             assert(false && "index is too large for current buffer");
-            unreachable();
+            std::unreachable();
         }
     }
 
diff --git a/dwave/optimization/src/nodes/lp.cpp b/dwave/optimization/src/nodes/lp.cpp
index b1f06f2c..1ab60b83 100644
--- a/dwave/optimization/src/nodes/lp.cpp
+++ b/dwave/optimization/src/nodes/lp.cpp
@@ -15,6 +15,7 @@
 #include "dwave-optimization/nodes/lp.hpp"
 
 #include <string>
+#include <utility>
 
 #include "../simplex.hpp"
 #include "_state.hpp"
@@ -433,7 +434,7 @@ void LinearProgramNode::replace_predecessor_(ssize_t index, Node* node_ptr) {
     if (check_and_replace(lb_ptr_)) return;
     if (check_and_replace(ub_ptr_)) return;
 
-    unreachable();
+    std::unreachable();
     assert(false and "should never get here");
 }
 
diff --git a/dwave/optimization/src/nodes/manipulation.cpp b/dwave/optimization/src/nodes/manipulation.cpp
index 1c45621f..b4b2f063 100644
--- a/dwave/optimization/src/nodes/manipulation.cpp
+++ b/dwave/optimization/src/nodes/manipulation.cpp
@@ -1193,14 +1193,7 @@ void ResizeNode::initialize_state(State& state) const {
     const ssize_t size = this->size();  // the desired size of our state
     assert(size >= 0);                  // we're never dynamic
 
-    std::vector<double> values;
-    values.reserve(size);
-
-    // Fill in from our predecessor, up to our size.
-    // In c++23 we could use append_range(...) which would be nicer.
-    for (const auto& v : array_ptr_->view(state) | std::views::take(size)) {
-        values.emplace_back(v);
-    }
+    auto values = std::ranges::to<std::vector>(array_ptr_->view(state) | std::views::take(size));
 
     // Now fill in everything else with our fill value
     assert(
diff --git a/dwave/optimization/src/nodes/naryop.cpp b/dwave/optimization/src/nodes/naryop.cpp
index 5dc47e48..150337f1 100644
--- a/dwave/optimization/src/nodes/naryop.cpp
+++ b/dwave/optimization/src/nodes/naryop.cpp
@@ -19,6 +19,7 @@
 #include <cmath>
 #include <stdexcept>
 #include <type_traits>
+#include <utility>
 
 #include "_state.hpp"
 
@@ -83,7 +84,7 @@ bool calculate_integral(const std::vector<Array*>& operands) {
     }
 
     assert(false && "not implemeted yet");
-    unreachable();
+    std::unreachable();
 }
 
 template <class BinaryOp>
@@ -142,7 +143,7 @@ ValuesInfo calculate_values_info(const std::vector<Array*>& operands) {
     }
 
     assert(false && "not implemeted yet");
-    unreachable();
+    std::unreachable();
 }
 
 template <class BinaryOp>
diff --git a/dwave/optimization/src/nodes/numbers.cpp b/dwave/optimization/src/nodes/numbers.cpp
index bed90025..a12d667c 100644
--- a/dwave/optimization/src/nodes/numbers.cpp
+++ b/dwave/optimization/src/nodes/numbers.cpp
@@ -502,7 +502,7 @@ bool satisfies_sum_constraint(
                     break;
                 default:
                     assert(false && "Unexpected operator type.");
-                    unreachable();
+                    std::unreachable();
             }
         }
     }
@@ -593,7 +593,7 @@ double sum_constraint_delta(
             return (lhs < bound) ? (bound - lhs) : 0.0;
         default:
             assert(false && "Unexpected operator type.");
-            unreachable();
+            std::unreachable();
     }
 }
 
@@ -717,7 +717,7 @@ void NumberNode::initialize_state(State& state) const {
         initialize_state(state, std::move(values));
     } else {
         assert(false && "Multiple sum constraints not yet supported.");
-        unreachable();
+        std::unreachable();
     }
 }
 
@@ -1608,7 +1608,7 @@ void BinaryNode::initialize_state(State& state) const {
         initialize_state(state, std::move(values));
     } else {
         assert(false && "Multiple sum constraints not yet supported.");
-        unreachable();
+        std::unreachable();
     }
 }
 
diff --git a/dwave/optimization/src/nodes/unaryop.cpp b/dwave/optimization/src/nodes/unaryop.cpp
index 73902761..d871be91 100644
--- a/dwave/optimization/src/nodes/unaryop.cpp
+++ b/dwave/optimization/src/nodes/unaryop.cpp
@@ -14,6 +14,8 @@
 
 #include "dwave-optimization/nodes/unaryop.hpp"
 
+#include <utility>
+
 #include "_state.hpp"
 
 namespace dwave::optimization {
@@ -58,7 +60,7 @@ std::pair<double, double> calculate_values_minmax(const Array* array_ptr) {
             return std::make_pair(low, high);
         } else if (low >= 0) {
             assert(false && "min > max");
-            unreachable();
+            std::unreachable();
         } else if (high >= 0) {
             return std::pair<double, double>(0.0, std::max<double>(-low, high));
         } else {
@@ -99,7 +101,7 @@ std::pair<double, double> calculate_values_minmax(const Array* array_ptr) {
     }
 
     assert(false && "not implemeted yet");
-    unreachable();
+    std::unreachable();
 }
 
 template <class UnaryOp>
diff --git a/meson.build b/meson.build
index b8882ec8..1e64bf33 100644
--- a/meson.build
+++ b/meson.build
@@ -2,7 +2,7 @@ project(
     'dwave-optimization',
     'c', 'cpp', 'cython',
     default_options: [
-        'cpp_std=c++20',
+        'cpp_std=c++23',
         'buildtype=release',
         'b_ndebug=if-release',  # add -DNDEBUG when building for "release", which we do by default
         'optimization=3',
@@ -19,12 +19,14 @@ project(
     ).stdout(),
 )
 
-# We want some debugging symbols
-add_project_arguments(['-g1'], language: ['cpp'])
-
 cpp = meson.get_compiler('cpp')
 py = import('python').find_installation(pure: false)
 
+# We want some debugging symbols
+if cpp.has_argument('-g1')
+  add_project_arguments('-g1', language: 'cpp')
+endif
+
 dwave_optimization_include = include_directories('dwave/optimization/include/')
 dwave_optimization_src = [
     'dwave/optimization/src/nodes/_checkpoints.cpp',
diff --git a/releasenotes/notes/c++23-60fb26a150a004e8.yaml b/releasenotes/notes/c++23-60fb26a150a004e8.yaml
new file mode 100644
index 00000000..01b4b7bd
--- /dev/null
+++ b/releasenotes/notes/c++23-60fb26a150a004e8.yaml
@@ -0,0 +1,7 @@
+---
+features:
+  - Compile C++ library with C++23.
+upgrade:
+  - Drop support for GCC<14.
+other:
+  - Build Windows wheels with LLVM rather than MSVC.