diff --git a/CHANGELOG.md b/CHANGELOG.md
index 126fdff584c8..480b9883166a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [7.0.14]
+
+[7.0.14]: https://github.com/microsoft/CCF/releases/tag/ccf-7.0.14
+
+### Changed
+
+- CCF and C++ applications built against it now require C++23. The supported minimum Clang version remains 18.1.2. (#8234)
+
 ## [7.0.13]
 
 [7.0.13]: https://github.com/microsoft/CCF/releases/tag/ccf-7.0.13
diff --git a/cmake/preproject.cmake b/cmake/preproject.cmake
index 289929b6bcbc..a8cb2db85488 100644
--- a/cmake/preproject.cmake
+++ b/cmake/preproject.cmake
@@ -83,4 +83,5 @@ function(add_warning_checks name)
   )
 endfunction()
 
-set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD 23)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
diff --git a/include/ccf/byte_vector.h b/include/ccf/byte_vector.h
index 8c4fc6043011..7cb14debf5ff 100644
--- a/include/ccf/byte_vector.h
+++ b/include/ccf/byte_vector.h
@@ -8,7 +8,10 @@
 #include <climits>
 #include <fmt/format.h>
 #include <fmt/ranges.h>
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
 #include <small_vector/SmallVector.h>
+#pragma clang diagnostic pop
 
 namespace ccf
 {
diff --git a/include/ccf/ds/enum_formatter.h b/include/ccf/ds/enum_formatter.h
index 2aa16f62a530..d96ca9d359e3 100644
--- a/include/ccf/ds/enum_formatter.h
+++ b/include/ccf/ds/enum_formatter.h
@@ -4,6 +4,7 @@
 
 #define FMT_HEADER_ONLY
 #include <fmt/format.h>
+#include <utility>
 
 /**
  * Generic formatter for scoped enums.
@@ -22,8 +23,7 @@ struct formatter<E, std::enable_if_t<std::is_enum_v<E>, char>>
   template <typename FormatContext>
   auto format(const E& value, FormatContext& ctx) const
   {
-    return fmt::format_to(
-      ctx.out(), "{}", static_cast<std::underlying_type_t<E>>(value));
+    return fmt::format_to(ctx.out(), "{}", std::to_underlying(value));
   }
 };
 FMT_END_NAMESPACE
diff --git a/include/ccf/ds/hash.h b/include/ccf/ds/hash.h
index 3f1b3227a2c2..28ab493cdb69 100644
--- a/include/ccf/ds/hash.h
+++ b/include/ccf/ds/hash.h
@@ -6,7 +6,10 @@
 
 #include <array>
 #include <cstdint>
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
 #include <small_vector/SmallVector.h>
+#pragma clang diagnostic pop
 #include <string_view>
 #include <vector>
 
diff --git a/include/ccf/ds/logger.h b/include/ccf/ds/logger.h
index dd7cb6513264..1747fa23342c 100644
--- a/include/ccf/ds/logger.h
+++ b/include/ccf/ds/logger.h
@@ -15,6 +15,7 @@
 #include <optional>
 #include <sstream>
 #include <type_traits>
+#include <utility>
 
 namespace ccf::logger
 {
@@ -25,7 +26,7 @@ namespace ccf::logger
 
   static constexpr const char* to_string(LoggerLevel l)
   {
-    return LevelNames[static_cast<int>(l)];
+    return LevelNames[std::to_underlying(l)];
   }
 
   static constexpr long int ns_per_s = 1'000'000'000;
diff --git a/include/ccf/endpoint.h b/include/ccf/endpoint.h
index eafcc4d34c39..9f75fd969da8 100644
--- a/include/ccf/endpoint.h
+++ b/include/ccf/endpoint.h
@@ -542,8 +542,7 @@ struct formatter<ccf::endpoints::ForwardingRequired>
       default:
       {
         throw std::logic_error(fmt::format(
-          "Unhandled value for ForwardingRequired: {}",
-          static_cast<uint8_t>(v)));
+          "Unhandled value for ForwardingRequired: {}", std::to_underlying(v)));
       }
     }
   }
diff --git a/include/ccf/js/kv_access_permissions.h b/include/ccf/js/kv_access_permissions.h
index 9ce17b0bc402..86641f56ff82 100644
--- a/include/ccf/js/kv_access_permissions.h
+++ b/include/ccf/js/kv_access_permissions.h
@@ -4,6 +4,8 @@
 
 #include "ccf/js/core/context.h"
 
+#include <utility>
+
 namespace ccf::js
 {
   enum class KVAccessPermissions : uint8_t
@@ -17,9 +19,7 @@ namespace ccf::js
   inline KVAccessPermissions intersect_access_permissions(
     KVAccessPermissions l, KVAccessPermissions r)
   {
-    /* This could use std::to_underlying from C++23 */
-    using T = std::underlying_type_t<KVAccessPermissions>;
-    const auto intersection = (T)l & (T)r;
-    return KVAccessPermissions(intersection);
+    const auto intersection = std::to_underlying(l) & std::to_underlying(r);
+    return static_cast<KVAccessPermissions>(intersection);
   }
 }
diff --git a/include/ccf/service/node_info_network.h b/include/ccf/service/node_info_network.h
index d5433ad60325..b6788e58d6a5 100644
--- a/include/ccf/service/node_info_network.h
+++ b/include/ccf/service/node_info_network.h
@@ -222,7 +222,7 @@ namespace ccf
     // rsplit_1 splits on the last ':'. When the address has no port it returns
     // ("", addr), which would wrongly put the host in the port slot; handle the
     // port-less case explicitly so the host stays in the first position.
-    if (addr.find(':') == std::string::npos)
+    if (!addr.contains(':'))
     {
       return std::make_pair(addr, std::string());
     }
@@ -238,7 +238,7 @@ namespace ccf
   inline static NodeInfoNetwork::NetAddress make_net_address(
     const std::string& host, const std::string& port)
   {
-    if (host.find(':') != std::string::npos && !host.starts_with('['))
+    if (host.contains(':') && !host.starts_with('['))
     {
       return fmt::format("[{}]:{}", host, port);
     }
diff --git a/include/ccf/service/tables/proposals.h b/include/ccf/service/tables/proposals.h
index 50813b7c2bf2..d71850d0b394 100644
--- a/include/ccf/service/tables/proposals.h
+++ b/include/ccf/service/tables/proposals.h
@@ -6,6 +6,7 @@
 #include "ccf/service/map.h"
 
 #include <unordered_map>
+#include <utility>
 #include <vector>
 
 namespace ccf
@@ -82,8 +83,8 @@ struct formatter<ccf::ProposalState>
       }
       default:
       {
-        throw std::logic_error(fmt::format(
-          "Unknown proposal state {}", static_cast<uint8_t>(state)));
+        throw std::logic_error(
+          fmt::format("Unknown proposal state {}", std::to_underlying(state)));
       }
     }
   }
diff --git a/include/ccf/tx_status.h b/include/ccf/tx_status.h
index 9802f43cafaf..0aabbbfcd1a2 100644
--- a/include/ccf/tx_status.h
+++ b/include/ccf/tx_status.h
@@ -5,6 +5,8 @@
 #include "ccf/ds/json.h"
 #include "ccf/tx_id.h"
 
+#include <utility>
+
 namespace ccf
 {
   /** Describes the status of a transaction, as seen by this node.
@@ -34,9 +36,8 @@ namespace ccf
   // Contains only the terminal values of TxStatus
   enum class FinalTxStatus : std::underlying_type_t<TxStatus>
   {
-    Committed =
-      static_cast<std::underlying_type_t<TxStatus>>(TxStatus::Committed),
-    Invalid = static_cast<std::underlying_type_t<TxStatus>>(TxStatus::Invalid),
+    Committed = std::to_underlying(TxStatus::Committed),
+    Invalid = std::to_underlying(TxStatus::Invalid),
   };
 
   constexpr char const* tx_status_to_str(TxStatus status)
diff --git a/python/pyproject.toml b/python/pyproject.toml
index 18462482f034..7529d0383b9b 100644
--- a/python/pyproject.toml
+++ b/python/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "ccf"
-version = "7.0.13"
+version = "7.0.14"
 authors = [
   { name="CCF Team", email="CCF-Sec@microsoft.com" },
 ]
diff --git a/src/common/cli_helper.h b/src/common/cli_helper.h
index dbaa3ff55e01..8b0578080ba3 100644
--- a/src/common/cli_helper.h
+++ b/src/common/cli_helper.h
@@ -68,9 +68,7 @@ namespace cli
       // Unbracketed IPv6 literals are ambiguous with the host:port separator.
       // Require bracketed "[host]:port" form for any address containing more
       // than one ':' (e.g. "::1").
-      if (
-        addr.find(':') != std::string::npos &&
-        addr.find(':') != addr.find_last_of(':'))
+      if (addr.contains(':') && addr.find(':') != addr.find_last_of(':'))
       {
         throw std::logic_error(fmt::format(
           "IPv6 address '{}' must be bracketed as '[host]:port'", addr));
diff --git a/src/consensus/aft/test/committable_suffix.cpp b/src/consensus/aft/test/committable_suffix.cpp
index 3571bedea2e5..206492e94b85 100644
--- a/src/consensus/aft/test/committable_suffix.cpp
+++ b/src/consensus/aft/test/committable_suffix.cpp
@@ -4,6 +4,7 @@
 #include "test_common.h"
 
 #define DOCTEST_CONFIG_NO_SHORT_MACRO_NAMES
+#include <algorithm>
 #include <doctest/doctest.h>
 
 void keep_messages_for_multiple(
@@ -16,7 +17,7 @@ void keep_messages_for_multiple(
   while (it != messages.end())
   {
     if (
-      std::find(targets.begin(), targets.end(), it->first) == targets.end() ||
+      !std::ranges::contains(targets, it->first) ||
       (max_to_keep.has_value() && kept[it->first] >= *max_to_keep))
     {
       it = messages.erase(it);
diff --git a/src/cose/test/cose_ffi_test.cpp b/src/cose/test/cose_ffi_test.cpp
index 60164c7ef06c..167ef1709862 100644
--- a/src/cose/test/cose_ffi_test.cpp
+++ b/src/cose/test/cose_ffi_test.cpp
@@ -147,9 +147,7 @@ TEST_CASE("cose_sign_ledger fails with invalid key")
     CoseKey::from_private(bad_key.data(), bad_key.size(), key_err);
   CHECK(!cose_key.is_set());
   CHECK(key_err.is_set());
-  CHECK(
-    key_err.to_string().find("d2i_AutoPrivateKey failed:") !=
-    std::string::npos);
+  CHECK(key_err.to_string().contains("d2i_AutoPrivateKey failed:"));
 }
 
 TEST_CASE("CoseKey error propagation")
@@ -169,8 +167,7 @@ TEST_CASE("CoseKey error propagation")
     auto k = CoseKey::from_private(truncated.data(), truncated.size(), err);
     CHECK(!k.is_set());
     CHECK(err.is_set());
-    CHECK(
-      err.to_string().find("d2i_AutoPrivateKey failed:") != std::string::npos);
+    CHECK(err.to_string().contains("d2i_AutoPrivateKey failed:"));
   }
 
   SUBCASE("valid key succeeds without error")
diff --git a/src/crypto/pem.cpp b/src/crypto/pem.cpp
index 16680715cef8..1b8980033f9f 100644
--- a/src/crypto/pem.cpp
+++ b/src/crypto/pem.cpp
@@ -6,7 +6,7 @@ namespace ccf::crypto
 {
   void Pem::check_pem_format()
   {
-    if (s.find("-----BEGIN") == std::string::npos)
+    if (!s.contains("-----BEGIN"))
     {
       throw std::runtime_error(
         fmt::format("PEM constructed with non-PEM data: {}", s));
diff --git a/src/crypto/test/crypto.cpp b/src/crypto/test/crypto.cpp
index 94dcb2bb8678..e29043e66dbe 100644
--- a/src/crypto/test/crypto.cpp
+++ b/src/crypto/test/crypto.cpp
@@ -628,8 +628,8 @@ void run_csr(bool corrupt_csr = false)
 
   std::string valid_from_, valid_to_;
   std::tie(valid_from_, valid_to_) = v.validity_period();
-  REQUIRE(valid_from_.find(valid_from) != std::string::npos);
-  REQUIRE(valid_to_.find(valid_to) != std::string::npos);
+  REQUIRE(valid_from_.contains(valid_from));
+  REQUIRE(valid_to_.contains(valid_to));
 }
 
 TEST_CASE("2-digit years")
diff --git a/src/ds/test/json_schema.cpp b/src/ds/test/json_schema.cpp
index b4da55354051..77147725eb9f 100644
--- a/src/ds/test/json_schema.cpp
+++ b/src/ds/test/json_schema.cpp
@@ -3,6 +3,7 @@
 #include "ccf/ds/json.h"
 
 #define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include <algorithm>
 #include <doctest/doctest.h>
 #include <nlohmann/json.hpp>
 #include <vector>
@@ -598,14 +599,14 @@ TEST_CASE("JSON with different field names")
   for (const auto s : required_json_fields)
   {
     REQUIRE(properties.find(s) != properties.end());
-    REQUIRE(std::find(required.begin(), required.end(), s) != required.end());
+    REQUIRE(std::ranges::contains(required, s));
   }
 
   std::vector<char const*> optional_json_fields{"A", "OTHER_NAME", "c"};
   for (const auto s : optional_json_fields)
   {
     REQUIRE(properties.find(s) != properties.end());
-    REQUIRE(std::find(required.begin(), required.end(), s) == required.end());
+    REQUIRE(!std::ranges::contains(required, s));
   }
 
   renamed::Foo foo;
diff --git a/src/ds/test/logger.cpp b/src/ds/test/logger.cpp
index ef33892cdde9..43e0ddc7667d 100644
--- a/src/ds/test/logger.cpp
+++ b/src/ds/test/logger.cpp
@@ -59,9 +59,9 @@ TEST_CASE("Framework logging macros")
     REQUIRE(logs.size() == 1);
 
     const auto& log = logs[0];
-    REQUIRE(log.find("info") != std::string::npos);
-    REQUIRE(log.find("logger.cpp") != std::string::npos);
-    REQUIRE(log.find("Hello A") != std::string::npos);
+    REQUIRE(log.contains("info"));
+    REQUIRE(log.contains("logger.cpp"));
+    REQUIRE(log.contains("Hello A"));
 
     logs.clear();
   }
@@ -72,9 +72,9 @@ TEST_CASE("Framework logging macros")
     REQUIRE(logs.size() == 1);
 
     const auto& log = logs[0];
-    REQUIRE(log.find("fail") != std::string::npos);
-    REQUIRE(log.find("logger.cpp") != std::string::npos);
-    REQUIRE(log.find("Hello B") != std::string::npos);
+    REQUIRE(log.contains("fail"));
+    REQUIRE(log.contains("logger.cpp"));
+    REQUIRE(log.contains("Hello B"));
 
     logs.clear();
   }
@@ -85,9 +85,9 @@ TEST_CASE("Framework logging macros")
     REQUIRE(logs.size() == 1);
 
     const auto& log = logs[0];
-    REQUIRE(log.find("fatal") != std::string::npos);
-    REQUIRE(log.find("logger.cpp") != std::string::npos);
-    REQUIRE(log.find("Hello C") != std::string::npos);
+    REQUIRE(log.contains("fatal"));
+    REQUIRE(log.contains("logger.cpp"));
+    REQUIRE(log.contains("Hello C"));
 
     logs.clear();
   }
@@ -108,10 +108,10 @@ TEST_CASE("Application logging macros")
     REQUIRE(logs.size() == 1);
 
     const auto& log = logs[0];
-    REQUIRE(log.find("info") != std::string::npos);
-    REQUIRE(log.find("[app]") != std::string::npos);
-    REQUIRE(log.find("logger.cpp") != std::string::npos);
-    REQUIRE(log.find("Hello A") != std::string::npos);
+    REQUIRE(log.contains("info"));
+    REQUIRE(log.contains("[app]"));
+    REQUIRE(log.contains("logger.cpp"));
+    REQUIRE(log.contains("Hello A"));
 
     logs.clear();
   }
@@ -122,10 +122,10 @@ TEST_CASE("Application logging macros")
     REQUIRE(logs.size() == 1);
 
     const auto& log = logs[0];
-    REQUIRE(log.find("fail") != std::string::npos);
-    REQUIRE(log.find("[app]") != std::string::npos);
-    REQUIRE(log.find("logger.cpp") != std::string::npos);
-    REQUIRE(log.find("Hello B") != std::string::npos);
+    REQUIRE(log.contains("fail"));
+    REQUIRE(log.contains("[app]"));
+    REQUIRE(log.contains("logger.cpp"));
+    REQUIRE(log.contains("Hello B"));
 
     logs.clear();
   }
@@ -136,10 +136,10 @@ TEST_CASE("Application logging macros")
     REQUIRE(logs.size() == 1);
 
     const auto& log = logs[0];
-    REQUIRE(log.find("fatal") != std::string::npos);
-    REQUIRE(log.find("[app]") != std::string::npos);
-    REQUIRE(log.find("logger.cpp") != std::string::npos);
-    REQUIRE(log.find("Hello C") != std::string::npos);
+    REQUIRE(log.contains("fatal"));
+    REQUIRE(log.contains("[app]"));
+    REQUIRE(log.contains("logger.cpp"));
+    REQUIRE(log.contains("Hello C"));
 
     logs.clear();
   }
@@ -167,10 +167,10 @@ TEST_CASE("Custom logging macros")
     REQUIRE(logs.size() == 1);
 
     const auto& log = logs[0];
-    REQUIRE(log.find("info") != std::string::npos);
-    REQUIRE(log.find(custom_tag) != std::string::npos);
-    REQUIRE(log.find("logger.cpp") != std::string::npos);
-    REQUIRE(log.find("Some message") != std::string::npos);
+    REQUIRE(log.contains("info"));
+    REQUIRE(log.contains(custom_tag));
+    REQUIRE(log.contains("logger.cpp"));
+    REQUIRE(log.contains("Some message"));
 
     logs.clear();
   }
@@ -181,21 +181,20 @@ TEST_CASE("Custom logging macros")
     REQUIRE(logs.size() == 1);
 
     const auto& log = logs[0];
-    REQUIRE(log.find("info") != std::string::npos);
+    REQUIRE(log.contains("info"));
     // Search for smaller prefixes of the long tag, expect that one is
     // eventually present
     std::string truncated_tag = custom_long_tag;
     while (truncated_tag.size() > 0)
     {
-      const auto search = log.find(truncated_tag);
-      if (search != std::string::npos)
+      if (log.contains(truncated_tag))
       {
         break;
       }
       truncated_tag.resize(truncated_tag.size() - 1);
     }
     REQUIRE(truncated_tag.size() > 0);
-    REQUIRE(log.find("Some other message") != std::string::npos);
+    REQUIRE(log.contains("Some other message"));
 
     logs.clear();
   }
diff --git a/src/ds/test/messaging.cpp b/src/ds/test/messaging.cpp
index 102fa0254224..df3ce15f315d 100644
--- a/src/ds/test/messaging.cpp
+++ b/src/ds/test/messaging.cpp
@@ -35,12 +35,12 @@ void require_throws_with(
 
     for (const auto& s : includes)
     {
-      REQUIRE(what.find(s) != std::string::npos);
+      REQUIRE(what.contains(s));
     }
 
     for (const auto& s : excludes)
     {
-      REQUIRE(what.find(s) == std::string::npos);
+      REQUIRE(!what.contains(s));
     }
   }
   REQUIRE(threw);
diff --git a/src/host/test/ledger.cpp b/src/host/test/ledger.cpp
index 608d37b6677f..53a6aa0b338b 100644
--- a/src/host/test/ledger.cpp
+++ b/src/host/test/ledger.cpp
@@ -113,7 +113,7 @@ size_t number_of_committed_files_in_ledger_dir(bool allow_recovery = false)
     auto file_name = f.path().string();
     if (
       (allow_recovery && is_ledger_file_name_recovery(file_name) &&
-       file_name.find(ledger_committed_suffix) != std::string::npos) ||
+       file_name.contains(ledger_committed_suffix)) ||
       is_ledger_file_name_committed(file_name))
     {
       committed_file_count++;
diff --git a/src/http/http2_parser.h b/src/http/http2_parser.h
index 8c10d68c582a..11eb03bfa84f 100644
--- a/src/http/http2_parser.h
+++ b/src/http/http2_parser.h
@@ -10,6 +10,8 @@
 #include "http_proc.h"
 #include "http_rpc_context.h"
 
+#include <utility>
+
 namespace http2
 {
   using DataHandlerCB = std::function<void(std::span<const uint8_t>)>;
@@ -273,8 +275,7 @@ namespace http2
     {
       std::vector<nghttp2_nv> hdrs = {};
 
-      auto status_str = fmt::format(
-        "{}", static_cast<std::underlying_type_t<ccf::http_status>>(status));
+      auto status_str = fmt::format("{}", std::to_underlying(status));
       hdrs.emplace_back(
         make_nv(ccf::http2::headers::STATUS, status_str.data()));
 
diff --git a/src/http/test/http_test.cpp b/src/http/test/http_test.cpp
index 6fe95680f500..eb8feec6a3d7 100644
--- a/src/http/test/http_test.cpp
+++ b/src/http/test/http_test.cpp
@@ -10,6 +10,7 @@
 
 #define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
 #define DOCTEST_CONFIG_NO_SHORT_MACRO_NAMES
+#include <algorithm>
 #include <doctest/doctest.h>
 #include <queue>
 #include <string>
@@ -466,9 +467,9 @@ DOCTEST_TEST_CASE("URL parsing")
   std::string path_, query_, fragment_;
   std::tie(path_, query_, fragment_) = http::split_url_path(m.url);
   DOCTEST_CHECK(path_ == path);
-  DOCTEST_CHECK(query_.find("balance=42") != std::string::npos);
-  DOCTEST_CHECK(query_.find("id=100") != std::string::npos);
-  DOCTEST_CHECK(query_.find("&") != std::string::npos);
+  DOCTEST_CHECK(query_.contains("balance=42"));
+  DOCTEST_CHECK(query_.contains("id=100"));
+  DOCTEST_CHECK(query_.contains("&"));
 }
 
 DOCTEST_TEST_CASE("Pessimal transport")
@@ -837,8 +838,7 @@ DOCTEST_TEST_CASE("Query parser")
   for (auto it = parsed.begin(); it != parsed.end(); ++it)
   {
     const auto k = it->first;
-    const auto found = std::find(checked_keys.begin(), checked_keys.end(), k);
-    DOCTEST_REQUIRE(found != checked_keys.end());
+    DOCTEST_REQUIRE(std::ranges::contains(checked_keys, k));
   }
 }
 
diff --git a/src/js/extensions/ccf/kv_helpers.h b/src/js/extensions/ccf/kv_helpers.h
index 0423134d3427..ade67e1c4192 100644
--- a/src/js/extensions/ccf/kv_helpers.h
+++ b/src/js/extensions/ccf/kv_helpers.h
@@ -362,7 +362,6 @@ namespace ccf::js::extensions::kvhelpers
   HANDLE_GETTER) \
   do \
   { \
-    /* This could use std::to_underlying from C++23 */ \
     const auto permitted = \
       ccf::js::intersect_access_permissions( \
         access_permission, PERMISSION_FLAGS) != KVAccessPermissions::ILLEGAL; \
diff --git a/src/js/test/js.cpp b/src/js/test/js.cpp
index e56fa96c618b..9366a3bb3f4d 100644
--- a/src/js/test/js.cpp
+++ b/src/js/test/js.cpp
@@ -176,7 +176,7 @@ TEST_CASE("Check KV Map access")
 
 bool str_contains(const std::string& s, std::string_view sv)
 {
-  const auto b = s.find(sv) != std::string::npos;
+  const auto b = s.contains(sv);
   if (!b)
   {
     fmt::print("Didn't find\n {}\nin\n {}\n", sv, s);
diff --git a/src/kv/raw_serialise.h b/src/kv/raw_serialise.h
index 8b1f061750ae..d0d3f5240284 100644
--- a/src/kv/raw_serialise.h
+++ b/src/kv/raw_serialise.h
@@ -8,7 +8,10 @@
 #include <array>
 #include <cstring>
 #include <limits>
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
 #include <small_vector/SmallVector.h>
+#pragma clang diagnostic pop
 #include <span>
 #include <tuple>
 #include <type_traits>
diff --git a/src/kv/test/kv_test.cpp b/src/kv/test/kv_test.cpp
index a356b968e6d1..0bec4c7f4666 100644
--- a/src/kv/test/kv_test.cpp
+++ b/src/kv/test/kv_test.cpp
@@ -1536,7 +1536,7 @@ TEST_CASE("foreach_key")
     auto tx = kv_store.create_tx();
     auto handle = tx.rw(map);
     REQUIRE_NOTHROW(handle->foreach_key([](const std::string& k) {
-      REQUIRE(k.find('k') != std::string::npos);
+      REQUIRE(k.contains('k'));
       return true;
     }));
 
@@ -1573,7 +1573,7 @@ TEST_CASE("foreach_value")
     auto tx = kv_store.create_tx();
     auto handle = tx.rw(map);
     REQUIRE_NOTHROW(handle->foreach_value([](const std::string& v) {
-      REQUIRE(v.find('v') != std::string::npos);
+      REQUIRE(v.contains('v'));
       return true;
     }));
 
diff --git a/src/kv/untyped_map.h b/src/kv/untyped_map.h
index cc04eb637a8c..0ed674ea2119 100644
--- a/src/kv/untyped_map.h
+++ b/src/kv/untyped_map.h
@@ -631,13 +631,6 @@ namespace ccf::kv::untyped
       return ok;
     }
 
-#ifndef __cpp_impl_three_way_comparison
-    bool operator!=(const Map& that) const
-    {
-      return !(*this == that);
-    }
-#endif
-
     std::unique_ptr<AbstractMap::Snapshot> snapshot(Version v) override
     {
       // This takes a snapshot of the state of the map at the last entry
diff --git a/src/node/node_inbound_message.h b/src/node/node_inbound_message.h
index 273501d9c105..83e390516070 100644
--- a/src/node/node_inbound_message.h
+++ b/src/node/node_inbound_message.h
@@ -9,6 +9,7 @@
 #include "node/node_types.h"
 
 #include <set>
+#include <utility>
 
 namespace ccf
 {
@@ -80,7 +81,7 @@ namespace ccf
       default:
       {
         throw std::logic_error(fmt::format(
-          "Unknown node message type: {}", static_cast<uint32_t>(msg_type)));
+          "Unknown node message type: {}", std::to_underlying(msg_type)));
       }
     }
   }
diff --git a/src/node/node_state.h b/src/node/node_state.h
index eb4f64e7a911..8e27555ceb4c 100644
--- a/src/node/node_state.h
+++ b/src/node/node_state.h
@@ -2886,7 +2886,7 @@ namespace ccf
   private:
     bool is_ip(const std::string_view& hostname)
     {
-      if (hostname.find(':') != std::string_view::npos)
+      if (hostname.contains(':'))
       {
         in6_addr addr{};
         if (inet_pton(AF_INET6, std::string(hostname).c_str(), &addr) == 1)
diff --git a/src/node/rpc/file_serving_handlers.h b/src/node/rpc/file_serving_handlers.h
index cc74de27eca1..29170a2c6b17 100644
--- a/src/node/rpc/file_serving_handlers.h
+++ b/src/node/rpc/file_serving_handlers.h
@@ -222,7 +222,7 @@ namespace ccf::node
           return;
         }
 
-        if (ranges.find(',') != std::string::npos)
+        if (ranges.contains(','))
         {
           ctx.rpc_ctx->set_error(
             HTTP_STATUS_BAD_REQUEST,
diff --git a/src/node/rpc/node_frontend_utils.h b/src/node/rpc/node_frontend_utils.h
index 58b632de1146..f5adaf9b91fb 100644
--- a/src/node/rpc/node_frontend_utils.h
+++ b/src/node/rpc/node_frontend_utils.h
@@ -6,6 +6,7 @@
 #include "ccf/node/quote.h"
 
 #include <stdexcept>
+#include <utility>
 
 namespace ccf
 {
@@ -46,8 +47,7 @@ namespace ccf
           HTTP_STATUS_UNAUTHORIZED, "Quote TCB version is too low");
       default:
         throw std::logic_error(fmt::format(
-          "Unknown QuoteVerificationResult: {}",
-          static_cast<uint32_t>(result)));
+          "Unknown QuoteVerificationResult: {}", std::to_underlying(result)));
     }
   }
 }
\ No newline at end of file
diff --git a/src/node/rpc/test/frontend_test.cpp b/src/node/rpc/test/frontend_test.cpp
index e1fe0365593e..f4035d791fdc 100644
--- a/src/node/rpc/test/frontend_test.cpp
+++ b/src/node/rpc/test/frontend_test.cpp
@@ -740,9 +740,7 @@ TEST_CASE("process with caller")
       auto response = parse_response(serialized_response);
       REQUIRE(response.status == HTTP_STATUS_UNAUTHORIZED);
       const std::string error_msg(response.body.begin(), response.body.end());
-      CHECK(
-        error_msg.find("Could not find matching user certificate") !=
-        std::string::npos);
+      CHECK(error_msg.contains("Could not find matching user certificate"));
     }
 
     INFO("Anonymous caller");
@@ -752,7 +750,7 @@ TEST_CASE("process with caller")
       auto response = parse_response(serialized_response);
       REQUIRE(response.status == HTTP_STATUS_UNAUTHORIZED);
       const std::string error_msg(response.body.begin(), response.body.end());
-      CHECK(error_msg.find("No caller user certificate") != std::string::npos);
+      CHECK(error_msg.contains("No caller user certificate"));
     }
   }
 }
@@ -952,7 +950,7 @@ TEST_CASE("Restricted verbs")
         const auto it = response.headers.find(ccf::http::headers::ALLOW);
         REQUIRE(it != response.headers.end());
         const auto v = it->second;
-        CHECK(v.find(llhttp_method_name(HTTP_GET)) != std::string::npos);
+        CHECK(v.contains(llhttp_method_name(HTTP_GET)));
       }
     }
 
@@ -973,7 +971,7 @@ TEST_CASE("Restricted verbs")
         const auto it = response.headers.find(ccf::http::headers::ALLOW);
         REQUIRE(it != response.headers.end());
         const auto v = it->second;
-        CHECK(v.find(llhttp_method_name(HTTP_POST)) != std::string::npos);
+        CHECK(v.contains(llhttp_method_name(HTTP_POST)));
       }
     }
 
@@ -995,11 +993,11 @@ TEST_CASE("Restricted verbs")
         const auto it = response.headers.find(ccf::http::headers::ALLOW);
         REQUIRE(it != response.headers.end());
         const auto v = it->second;
-        CHECK(v.find(llhttp_method_name(HTTP_PUT)) != std::string::npos);
-        CHECK(v.find(llhttp_method_name(HTTP_DELETE)) != std::string::npos);
+        CHECK(v.contains(llhttp_method_name(HTTP_PUT)));
+        CHECK(v.contains(llhttp_method_name(HTTP_DELETE)));
         if (verb != HTTP_OPTIONS)
         {
-          CHECK(v.find(llhttp_method_name(verb)) == std::string::npos);
+          CHECK(!v.contains(llhttp_method_name(verb)));
         }
       }
     }
diff --git a/src/node/rpc/test/frontend_test_infra.h b/src/node/rpc/test/frontend_test_infra.h
index ebc3bf68c2e0..f30c7c8b8725 100644
--- a/src/node/rpc/test/frontend_test_infra.h
+++ b/src/node/rpc/test/frontend_test_infra.h
@@ -73,7 +73,7 @@ void check_error(const TResponse& r, ccf::http_status expected)
 void check_error_message(const TResponse& r, const std::string& msg)
 {
   const std::string body_s(r.body.begin(), r.body.end());
-  CHECK(body_s.find(msg) != std::string::npos);
+  CHECK(body_s.contains(msg));
 }
 
 std::vector<uint8_t> create_request(
diff --git a/src/node/test/historical_queries.cpp b/src/node/test/historical_queries.cpp
index 47a8561da949..e1464dd309d8 100644
--- a/src/node/test/historical_queries.cpp
+++ b/src/node/test/historical_queries.cpp
@@ -851,10 +851,7 @@ TEST_CASE("StateCache range queries")
 
         // Don't validate anything about signature transactions, just the
         // business transactions between them
-        if (
-          std::find(
-            signature_versions.begin(), signature_versions.end(), seqno) ==
-          signature_versions.end())
+        if (!std::ranges::contains(signature_versions, seqno))
         {
           validate_business_transaction(store, seqno);
         }
@@ -1193,10 +1190,7 @@ TEST_CASE("StateCache sparse queries")
 
         // Don't validate anything about signature transactions, just the
         // business transactions between them
-        if (
-          std::find(
-            signature_versions.begin(), signature_versions.end(), seqno) ==
-          signature_versions.end())
+        if (!std::ranges::contains(signature_versions, seqno))
         {
           validate_business_transaction(store, seqno);
         }
@@ -1382,10 +1376,7 @@ TEST_CASE("StateCache concurrent access")
       {
         REQUIRE(store != nullptr);
         const auto seqno = store->current_txid().seqno;
-        if (
-          std::find(
-            signature_versions.begin(), signature_versions.end(), seqno) ==
-          signature_versions.end())
+        if (!std::ranges::contains(signature_versions, seqno))
         {
           validate_business_transaction(store, seqno);
         }
@@ -1398,10 +1389,7 @@ TEST_CASE("StateCache concurrent access")
       {
         REQUIRE(state != nullptr);
         const auto seqno = state->store->current_txid().seqno;
-        if (
-          std::find(
-            signature_versions.begin(), signature_versions.end(), seqno) ==
-          signature_versions.end())
+        if (!std::ranges::contains(signature_versions, seqno))
         {
           validate_business_transaction(state, seqno);
         }
diff --git a/src/node/test/js_policy.cpp b/src/node/test/js_policy.cpp
index 05f087357341..09e3ca192aea 100644
--- a/src/node/test/js_policy.cpp
+++ b/src/node/test/js_policy.cpp
@@ -77,8 +77,7 @@ TEST_CASE("Policy error handling")
     )";
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Unexpected return value") != std::string::npos);
+    REQUIRE(result.value().contains("Unexpected return value"));
   }
 
   SUBCASE("Returns undefined gives unexpected return value")
@@ -90,8 +89,7 @@ TEST_CASE("Policy error handling")
     )";
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Unexpected return value") != std::string::npos);
+    REQUIRE(result.value().contains("Unexpected return value"));
   }
 
   SUBCASE("Returns null gives unexpected return value")
@@ -103,8 +101,7 @@ TEST_CASE("Policy error handling")
     )";
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Unexpected return value") != std::string::npos);
+    REQUIRE(result.value().contains("Unexpected return value"));
   }
 
   SUBCASE("Returns number gives unexpected return value")
@@ -116,8 +113,7 @@ TEST_CASE("Policy error handling")
     )";
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Unexpected return value") != std::string::npos);
+    REQUIRE(result.value().contains("Unexpected return value"));
   }
 
   SUBCASE("Throws is reported as error")
@@ -129,9 +125,8 @@ TEST_CASE("Policy error handling")
     )";
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Code update policy threw") != std::string::npos);
-    REQUIRE(result.value().find("intentional failure") != std::string::npos);
+    REQUIRE(result.value().contains("Code update policy threw"));
+    REQUIRE(result.value().contains("intentional failure"));
   }
 
   SUBCASE("Syntax error")
@@ -143,9 +138,7 @@ TEST_CASE("Policy error handling")
     )";
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Invalid code update policy module") !=
-      std::string::npos);
+    REQUIRE(result.value().contains("Invalid code update policy module"));
   }
 
   SUBCASE("Missing apply export")
@@ -157,9 +150,7 @@ TEST_CASE("Policy error handling")
     )";
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Invalid code update policy module") !=
-      std::string::npos);
+    REQUIRE(result.value().contains("Invalid code update policy module"));
   }
 
   SUBCASE("Empty policy string")
@@ -167,9 +158,7 @@ TEST_CASE("Policy error handling")
     const std::string policy;
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Invalid code update policy module") !=
-      std::string::npos);
+    REQUIRE(result.value().contains("Invalid code update policy module"));
   }
 
   SUBCASE("Runtime error in JS")
@@ -181,8 +170,7 @@ TEST_CASE("Policy error handling")
     )";
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Code update policy threw") != std::string::npos);
+    REQUIRE(result.value().contains("Code update policy threw"));
   }
 
   SUBCASE("Infinite loop is handled")
@@ -195,8 +183,7 @@ TEST_CASE("Policy error handling")
     )";
     auto result = apply_node_join_policy(policy, inputs);
     REQUIRE(result.has_value());
-    REQUIRE(
-      result.value().find("Code update policy threw") != std::string::npos);
+    REQUIRE(result.value().contains("Code update policy threw"));
   }
 
   SUBCASE("Empty inputs")
diff --git a/src/tasks/fan_in_tasks.h b/src/tasks/fan_in_tasks.h
index 6b12cd8a427c..cc1a816002a5 100644
--- a/src/tasks/fan_in_tasks.h
+++ b/src/tasks/fan_in_tasks.h
@@ -14,7 +14,7 @@ namespace ccf::tasks
   {
   protected:
     struct PImpl;
-    std::unique_ptr<PImpl> pimpl = nullptr;
+    std::unique_ptr<PImpl> pimpl;
 
     void enqueue_on_board();
     void do_task_implementation() override;
diff --git a/src/tasks/job_board.h b/src/tasks/job_board.h
index 13705b9b7231..b57d332595f6 100644
--- a/src/tasks/job_board.h
+++ b/src/tasks/job_board.h
@@ -13,7 +13,7 @@ namespace ccf::tasks
   class JobBoard
   {
     struct PImpl;
-    std::unique_ptr<PImpl> pimpl = nullptr;
+    std::unique_ptr<PImpl> pimpl;
 
     void add_timed_task(
       Task task,
diff --git a/src/tasks/ordered_tasks.h b/src/tasks/ordered_tasks.h
index c22a6f0b9208..fd0e0c5ac130 100644
--- a/src/tasks/ordered_tasks.h
+++ b/src/tasks/ordered_tasks.h
@@ -57,7 +57,7 @@ namespace ccf::tasks
   {
   protected:
     struct PImpl;
-    std::unique_ptr<PImpl> pimpl = nullptr;
+    std::unique_ptr<PImpl> pimpl;
 
     struct ResumeOrderedTasks;
 
diff --git a/src/tasks/test/basic_tasks.cpp b/src/tasks/test/basic_tasks.cpp
index 8a8ea35667d6..c19a20090e94 100644
--- a/src/tasks/test/basic_tasks.cpp
+++ b/src/tasks/test/basic_tasks.cpp
@@ -326,7 +326,7 @@ TEST_CASE("Exception handling" * doctest::test_suite("basic_tasks"))
       ccf::pal::MutexGuard lock(mutex);
       for (const auto& m : messages)
       {
-        if (m.find(substring) != std::string::npos)
+        if (m.contains(substring))
         {
           return true;
         }
diff --git a/src/tasks/worker.cpp b/src/tasks/worker.cpp
index cbf11a6f36d0..3a9c25af10ea 100644
--- a/src/tasks/worker.cpp
+++ b/src/tasks/worker.cpp
@@ -11,6 +11,7 @@
 #include <limits>
 #include <memory>
 #include <sstream>
+#include <utility>
 
 namespace ccf::tasks
 {
@@ -285,6 +286,6 @@ extern "C"
     // Both real_cxa_throw and std::abort() are [[noreturn]], but the compiler
     // may not recognize that for function pointers. This satisfies the compiler
     // that we never return from this function.
-    __builtin_unreachable();
+    std::unreachable();
   }
 }
diff --git a/tests/test_install_build.sh b/tests/test_install_build.sh
index 546c0f31803e..e94ac8f3a2f6 100755
--- a/tests/test_install_build.sh
+++ b/tests/test_install_build.sh
@@ -10,8 +10,8 @@ CC=$(which clang || true)
 CXX=$(which clang++ || true)
 
 if [ "$CC" = "" ] || [ "$CXX" = "" ]; then
-    CC=$(command -v clang-15 || true)
-    CXX=$(command -v clang++-15 || true)
+    CC=$(command -v clang-18 || true)
+    CXX=$(command -v clang++-18 || true)
 fi
 
 CC=$CC CXX=$CXX cmake -GNinja "$@" ../samples/apps/logging/