Restructure the spinlock code:

- Add function-based spinlock API
- Improve comments
- Reduce bouncing with contested locks

.cspell.config.yaml

@@ -255,6 +255,7 @@ words:
   - queuable
   - Raphson
   - rcflags
+  - reencrypted
   - replayer
   - repodata
   - repomd

.git-blame-ignore-revs

@@ -5,6 +5,18 @@
 # This file is sorted in reverse chronological order, with the most recent commits at the top.
 # The commits listed here are ignored by git blame, which is useful for formatting-only commits that would otherwise obscure the history of changes to a file.
 
+# chore: CamelCase for typedef/using in `clang-tidy` (#8177)
+97a1824537d20d82d25bf151a37a7a4532ebf085
+# chore: Rename CamelCase namespaces to snake_case (#7933)
+06488c1318d96f56d0536251bee08ac85fa7fdd3
+# style: Unify style for all Doxygen comments (#7776)
+73b6852a122854140336e6e6bc30a3a4b41aa5fd
+# style: More clang-tidy identifier renaming (#7290)
+a830ab10efed8d3e59ef2fc15d66efdf9c6bb0d8
+# refactor: Rename static constants (#7120)
+5b6e8b6f93b19c1e3f6a3467a25639031d9d9a53
+# chore: More fixes for bad renames (#7092)
+7afdd71a54d562b32a50b29a5aa00bb997dc9053
 # refactor: Enable clang-tidy `readability-identifier-naming` check (#6571)
 8995564ed6b9e453e144bb663303072a3c1ba305
 # refactor: Enable remaining clang-tidy `cppcoreguidelines` checks (#6538)

API-CHANGELOG.md

@@ -30,6 +30,11 @@ Version 3.5.0 is not yet released.
 
 - `subscribe`, `unsubscribe`: Added an optional `mpt_issuances` request field, an array of MPT issuance IDs (hex strings). Subscribers receive a message with `type` `mptTransaction` for each validated transaction whose metadata affects a subscribed issuance; the message has the same fields as the `transactions` stream. MPT issuance subscriptions count toward the per-connection subscription limit. An empty array, a non-array value, or an invalid ID returns `invalidParams`. ([#5671](https://github.com/XRPLF/rippled/pull/5671))
 
+### Bugfixes in 3.5.0
+
+- `channel_authorize`: The `channel_id` field now returns an `invalidParams` error if the value is not a string. [#7582](https://github.com/XRPLF/rippled/pull/7582)
+- `channel_verify`: The `channel_id` and `signature` fields now return an `invalidParams` error if the value is not a string. [#7582](https://github.com/XRPLF/rippled/pull/7582)
+
 ## XRP Ledger server version 3.4.0
 
 Version 3.4.0 is not yet released. These changes are available in the 3.4.0 beta releases.

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1781173989,
-        "narHash": "sha256-fnzKKPvS+oieI/pTzotA5tkoM47EB1NpaBcgk4R97hE=",
+        "lastModified": 1791130267,
+        "narHash": "sha256-1sjwcQMcgAbmiip/VivBSiK8p2bTkQGOvCuO7vnwfx4=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "8c91a71d13451abc40eb9dae8910f972f979852f",
+        "rev": "9013764fcc0ea99fa16cf7aa7decf8a5c3889dd2",
         "type": "github"
       },
       "original": {
@@ -47,11 +47,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1784611586,
-        "narHash": "sha256-OfqgY+0hp/zseZB7uyH0U8kIDPS4scZZCyAurEplvG0=",
+        "lastModified": 1791189933,
+        "narHash": "sha256-Y8eN7ki0Urx4Ojf4w1xSpWg8uk/3lJqK+E0Oth77rH0=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "14f58845249f3552a89b07772626b8d3c632fa86",
+        "rev": "e60029353d0c48d216bc4b065168ccd4079c166f",
         "type": "github"
       },
       "original": {

include/xrpl/basics/CountedObject.h

@@ -1,29 +1,31 @@
 #pragma once
 
-#include <xrpl/beast/type_name.h>
+#include <xrpl/beast/utility/instrumentation.h>
 
+#include <boost/core/type_name.hpp>
+
+#include <algorithm>
 #include <atomic>
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
 #include <string>
+#include <type_traits>
 #include <utility>
-#include <vector>
 
 namespace xrpl {
 
 /**
  * Manages all counted object types.
+ *
+ * Counters register themselves on a lock-free intrusive list maintained
+ * by this object when constructed. Because counters are never destroyed
+ * or removed, the ABA problem does not apply.
+ *
+ * The registry is iterable as a forward range.
  */
 class CountedObjects
 {
-public:
-    static CountedObjects&
-    getInstance() noexcept;
-
-    using Entry = std::pair<std::string, int>;
-    using List = std::vector<Entry>;
-
-    [[nodiscard]] List
-    getCounts(int minimumThreshold) const;
-
 public:
     /**
      * Implementation for @ref CountedObject.
@@ -33,68 +35,147 @@ public:
     class Counter
     {
     public:
-        Counter(std::string name) noexcept : name_(std::move(name)), count_(0)
-        {
-            // Insert ourselves at the front of the lock-free linked list
-            CountedObjects& instance = CountedObjects::getInstance();
-            Counter* head = nullptr;
+        Counter(std::string name) noexcept;
 
-            do
-            {
-                head = instance.head_.load();
-                next_ = head;
-            } while (instance.head_.exchange(this) != head);
+        // Counters are intrusive list nodes whose addresses are published
+        // in the registry; they must never be copied or moved. The atomic
+        // members already force this, but we make it explicit.
+        Counter(Counter const&) = delete;
+        Counter&
+        operator=(Counter const&) = delete;
+        Counter(Counter&&) = delete;
+        Counter&
+        operator=(Counter&&) = delete;
 
-            ++instance.count_;
-        }
-
-        ~Counter() noexcept = default;
-
-        int
+        std::uint32_t
         increment() noexcept
         {
-            return ++count_;
+            auto const newCount = count_.fetch_add(1, std::memory_order::relaxed) + 1;
+            XRPL_ASSERT(newCount != 0, "xrpl::CountedObjects::Counter::increment : no overflow");
+
+            auto maxCount = maxCount_.load(std::memory_order::relaxed);
+
+            while (newCount > maxCount &&
+                   !maxCount_.compare_exchange_weak(maxCount, newCount, std::memory_order::relaxed))
+            {
+            }
+
+            return newCount;
         }
 
-        int
+        std::uint32_t
         decrement() noexcept
         {
-            return --count_;
+            auto const prev = count_.fetch_sub(1, std::memory_order::relaxed);
+            XRPL_ASSERT(prev != 0, "xrpl::CountedObjects::Counter::decrement : no underflow");
+            return prev - 1;
         }
 
-        [[nodiscard]] int
-        getCount() const noexcept
+        [[nodiscard]] std::uint32_t
+        count() const noexcept
         {
-            return count_.load();
+            return count_.load(std::memory_order::relaxed);
         }
 
-        [[nodiscard]] Counter*
-        getNext() const noexcept
+        [[nodiscard]] std::uint32_t
+        max() const noexcept
         {
-            return next_;
+            return std::max(
+                count_.load(std::memory_order::relaxed),
+                maxCount_.load(std::memory_order::relaxed));
         }
 
         [[nodiscard]] std::string const&
-        getName() const noexcept
+        name() const noexcept
         {
             return name_;
         }
 
     private:
+        friend class CountedObjects;
+
+        Counter* next_ = nullptr;
+        std::atomic<std::uint32_t> count_ = 0;
+        std::atomic<std::uint32_t> maxCount_ = 0;
         std::string const name_;
-        std::atomic<int> count_;
-        Counter* next_;
     };
 
-private:
-    CountedObjects() noexcept;
-    ~CountedObjects() noexcept = default;
+    class Iterator
+    {
+    public:
+        using value_type = Counter const;
+        using reference = value_type&;
+        using pointer = value_type*;
+        using difference_type = std::ptrdiff_t;
+        using iterator_category = std::forward_iterator_tag;
+
+        explicit Iterator(Counter* c = nullptr) noexcept : current_(c)
+        {
+        }
+
+        reference
+        operator*() const noexcept
+        {
+            return *current_;
+        }
+
+        pointer
+        operator->() const noexcept
+        {
+            return current_;
+        }
+
+        Iterator&
+        operator++() noexcept
+        {
+            current_ = current_->next_;
+            return *this;
+        }
+
+        Iterator
+        operator++(int) noexcept
+        {
+            auto tmp = *this;
+            ++*this;
+            return tmp;
+        }
+
+        bool
+        operator==(Iterator const&) const noexcept = default;
+
+    private:
+        Counter* current_;
+    };
+
+    constexpr CountedObjects() noexcept = default;
+
+    [[nodiscard]] auto
+    begin() const noexcept
+    {
+        return Iterator{head_.load(std::memory_order::acquire)};
+    }
+
+    [[nodiscard]] auto
+    end() const noexcept
+    {
+        return Iterator{};
+    }
 
 private:
-    std::atomic<int> count_;
-    std::atomic<Counter*> head_;
+    std::atomic<Counter*> head_ = nullptr;
 };
 
+/** The global counted object registry. */
+inline constinit CountedObjects gCountedObjects;
+
+inline CountedObjects::Counter::Counter(std::string name) noexcept
+    : next_(gCountedObjects.head_.load(std::memory_order::relaxed)), name_(std::move(name))
+{
+    while (!gCountedObjects.head_.compare_exchange_weak(
+        next_, this, std::memory_order::release, std::memory_order::relaxed))
+        ;
+}
+
 //------------------------------------------------------------------------------
 
 /**
@@ -103,27 +184,37 @@ private:
  * Derived classes have their instances counted automatically. This is used
  * for reporting purposes.
  *
+ * The constructors are private and `Object` is befriended so that the
+ * CRTP parameter must be the deriving class itself: a copy-paste error
+ * like `class B : public CountedObject<A>` fails to compile instead of
+ * silently polluting A's count.
+ *
+ * @note This class has no move operations by design: a derived class's
+ *       move constructor falls back to the copy constructor for this
+ *       base, so the newly created instance is counted. This keeps the
+ *       invariant that count is the number of outstanding subobjects.
+ *
+ * @warning Counted objects constructed during dynamic initialization of
+ *          other translation units may have their increments discarded when
+ *          counter itself is dynamically initialized. Do not create counted
+ *          objects before main() begins.
+ *
  * @ingroup basics
  */
 template <class Object>
+    requires std::is_class_v<Object>
 class CountedObject
 {
-private:
-    static auto&
-    getCounter() noexcept
-    {
-        static CountedObjects::Counter kC{beast::typeName<Object>()};
-        return kC;
-    }
+    static inline CountedObjects::Counter counter{boost::core::type_name<Object>()};
 
     CountedObject() noexcept
     {
-        getCounter().increment();
+        counter.increment();
     }
 
     CountedObject(CountedObject const&) noexcept
     {
-        getCounter().increment();
+        counter.increment();
     }
 
     CountedObject&
@@ -132,7 +223,7 @@ private:
 public:
     ~CountedObject() noexcept
     {
-        getCounter().decrement();
+        counter.decrement();
     }
 
     friend Object;

include/xrpl/basics/Number.h

@@ -110,10 +110,10 @@ static_assert(
  *
  * However, it does not have sufficient precision to represent the full integer
  * range of int64_t values (-2^63 to 2^63-1), which are needed for XRP and MPT
- * values. The implementation of SingleAssetVault, and LendingProtocol need to
- * represent those integer values accurately and precisely, both for the
- * STNumber field type, and for internal calculations. That necessitated the
- * "large" scale.
+ * values. The implementation of SingleAssetVault, LendingProtocol, and
+ * MPTokensV2 need to represent those integer values accurately and precisely,
+ * both for the STNumber field type, and for internal calculations. That
+ * necessitated the "large" scale.
  *
  * The "Large" scales are intended to represent all values that can be represented
  * by an STAmount - IOUs, XRP, and MPTs. It has a min value of 10^18, and a max
@@ -134,8 +134,8 @@ struct MantissaRange final
     // NOLINTBEGIN(readability-enum-initial-value)
     // The values don't matter, except for Large
     enum class MantissaScale {
-        // Small can be removed when either featureSingleAssetVault or featureLendingProtocol are
-        // retired
+        // Small can be removed when any of featureSingleAssetVault, featureLendingProtocol, or
+        // featureMPTokensV2 are retired
         Small,
         // LargeLegacy can be removed when fixCleanup3_2_0 is retired
         LargeLegacy,
@@ -311,10 +311,10 @@ concept Integral64 = std::is_same_v<T, std::int64_t> || std::is_same_v<T, std::u
  *
  * The mantissa range may be changed at runtime via setMantissaScale(). The
  * default mantissa range is "large". The range is updated whenever transaction
- * processing begins, based on whether SingleAssetVault or LendingProtocol are
- * enabled. If either is enabled, the mantissa range is set to "large". If not,
- * it is set to "small", preserving backward compatibility and correct
- * "amendment-gating".
+ * processing begins, based on whether SingleAssetVault, LendingProtocol, or
+ * MPTokensV2 are enabled. If any is enabled, the mantissa range is set to
+ * "large". If not, it is set to "small", preserving backward compatibility and
+ * correct "amendment-gating".
  *
  * It is extremely unlikely that any more calls to setMantissaScale() will be
  * needed outside of unit tests.
@@ -344,8 +344,8 @@ concept Integral64 = std::is_same_v<T, std::int64_t> || std::is_same_v<T, std::u
  * set/getMantissaScale() functions may be most appropriate. However, if the
  * test has anything to do with transaction processing, it should enable or
  * disable the amendments that control the mantissa range choice
- * (SingleAssetVault and LendingProtocol), and/or check if either of those
- * amendments are enabled to determine which result to expect.
+ * (SingleAssetVault, LendingProtocol, and MPTokensV2), and/or check if any of
+ * those amendments are enabled to determine which result to expect.
  */
 class Number final
 {

include/xrpl/basics/SlabAllocator.h

@@ -3,11 +3,11 @@
 #pragma once
 
 #include <xrpl/basics/ByteUtilities.h>
-#include <xrpl/beast/type_name.h>
 #include <xrpl/beast/utility/instrumentation.h>
 
 #include <boost/align.hpp>
 #include <boost/container/static_vector.hpp>
+#include <boost/core/type_name.hpp>
 #include <boost/predef.h>
 
 #include <algorithm>
@@ -16,6 +16,7 @@
 #include <cstring>
 #include <mutex>
 #include <stdexcept>
+#include <typeinfo>
 #include <vector>
 
 #if BOOST_OS_LINUX
@@ -335,7 +336,7 @@ public:
                 }) != cfg.end())
         {
             throw std::runtime_error(
-                "SlabAllocatorSet<" + beast::typeName<Type>() + ">: duplicate slab size");
+                "SlabAllocatorSet<" + boost::core::type_name<Type>() + ">: duplicate slab size");
         }
 
         for (auto const& c : cfg)

include/xrpl/basics/contract.h

@@ -1,7 +1,8 @@
 #pragma once
 
 #include <xrpl/basics/sanitizers.h>
-#include <xrpl/beast/type_name.h>
+
+#include <boost/core/type_name.hpp>
 
 #include <exception>
 #include <string>
@@ -55,7 +56,7 @@ Throw(Args&&... args)
         std::is_convertible_v<E*, std::exception*>, "Exception must derive from std::exception.");
 
     E e(std::forward<Args>(args)...);
-    logThrow(std::string("Throwing exception of type " + beast::typeName<E>() + ": ") + e.what());
+    logThrow("Throwing exception of type " + boost::core::type_name<E>() + ": " + e.what());
     throw std::move(e);
 }
 

include/xrpl/basics/enum_bitops.h

@@ -0,0 +1,200 @@
+#pragma once
+
+#include <concepts>
+#include <type_traits>
+#include <utility>
+
+namespace xrpl {
+
+/**
+ * Opt-in bitwise operators for scoped enumerations.
+ *
+ * Provides `&`, `|`, `^`, `~` and the corresponding compound assignment forms
+ * for any scoped enumeration with an unsigned underlying type that opts in by
+ * specializing @ref OptIn:
+ *
+ * @code
+ * namespace xrpl {
+ *
+ * enum class MyFlags : std::uint32_t { a = 1, b = 2, c = 4 };
+ *
+ * template <>
+ * struct enum_bitops::OptIn<MyFlags> : std::true_type {};
+ *
+ * }  // namespace xrpl
+ * @endcode
+ *
+ * The operators are constexpr and noexcept, and return the enumeration type.
+ *
+ * @par Where the specialization may be declared
+ *   In namespace xrpl, or at global scope with full qualification, and after
+ *   the enumeration is defined but before the operators are first used. This
+ *   cannot be done in a nested namespace or at class scope; for enumerations
+ *   nested in a class this means after the class definition.
+ *
+ * @par Where the operators are found
+ *   The operators are declared in namespace xrpl, so argument-dependent lookup
+ *   will find them only for enumerations declared in xrpl or nested in a class
+ *   declared directly in xrpl. Enumerations in a nested namespace will only be
+ *   found from code inside xrpl, and only if no enclosing scope declares an
+ *   operator of the same name; elsewhere they require using-declarations.
+ */
+namespace enum_bitops {
+
+/**
+ * Types that may be opted in to the bitwise operators.
+ *
+ * Satisfied by a scoped enumeration whose underlying type is an unsigned
+ * integer type.
+ *
+ * @tparam T The type to test.
+ */
+template <typename T>
+concept Eligible = std::is_scoped_enum_v<T> && std::unsigned_integral<std::underlying_type_t<T>>;
+
+/**
+ * Opt-in switch for the bitwise operators.
+ *
+ * The primary template derives from std::false_type. Specialize it to derive
+ * from std::true_type to enable the operators for an @ref Eligible enumeration.
+ *
+ * @tparam T The scoped enumeration to opt in.
+ */
+template <Eligible T>
+struct OptIn : std::false_type
+{
+};
+
+/**
+ * Enumerations for which the bitwise operators are enabled.
+ *
+ * Satisfied when @p T satisfies @ref Eligible and @ref OptIn has been
+ * specialized for it to derive from std::true_type.
+ *
+ * @tparam T The type to test.
+ */
+template <typename T>
+concept Candidate = Eligible<T> && OptIn<T>::value;
+
+}  // namespace enum_bitops
+
+// These are declared in xrpl, not in enum_bitops, so that argument-dependent
+// lookup finds them for enumerations whose associated namespace is xrpl.
+
+/**
+ * @name Bitwise operators for opted-in scoped enumerations
+ *
+ * Each operator applies the corresponding built-in operator to the
+ * underlying values and converts the result back to the enumeration type.
+ * Both operands must have the same enumeration type; there is no implicit
+ * conversion to or from the underlying type.
+ */
+/** @{ */
+
+/**
+ * Bitwise AND.
+ *
+ * @param lhs The left operand.
+ * @param rhs The right operand.
+ * @return The bits set in both @p lhs and @p rhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T
+operator&(T lhs, T rhs) noexcept
+{
+    return static_cast<T>(std::to_underlying(lhs) & std::to_underlying(rhs));
+}
+
+/**
+ * Bitwise OR.
+ *
+ * @param lhs The left operand.
+ * @param rhs The right operand.
+ * @return The bits set in @p lhs, in @p rhs, or in both.
+ */
+template <enum_bitops::Candidate T>
+constexpr T
+operator|(T lhs, T rhs) noexcept
+{
+    return static_cast<T>(std::to_underlying(lhs) | std::to_underlying(rhs));
+}
+
+/**
+ * Bitwise exclusive OR.
+ *
+ * @param lhs The left operand.
+ * @param rhs The right operand.
+ * @return The bits set in exactly one of @p lhs and @p rhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T
+operator^(T lhs, T rhs) noexcept
+{
+    return static_cast<T>(std::to_underlying(lhs) ^ std::to_underlying(rhs));
+}
+
+/**
+ * Bitwise complement.
+ *
+ * The result has every bit of the underlying type that is clear in
+ * @p val, including bits that no enumerator names. It is intended for
+ * clearing flags, as in `flags & ~flag`.
+ *
+ * @param val The operand.
+ * @return The complement of @p val.
+ */
+template <enum_bitops::Candidate T>
+constexpr T
+operator~(T val) noexcept
+{
+    return static_cast<T>(~std::to_underlying(val));
+}
+
+/**
+ * Bitwise AND assignment.
+ *
+ * @param lhs The value to modify.
+ * @param rhs The right operand.
+ * @return A reference to @p lhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T&
+operator&=(T& lhs, T rhs) noexcept
+{
+    lhs = lhs & rhs;
+    return lhs;
+}
+
+/**
+ * Bitwise OR assignment.
+ *
+ * @param lhs The value to modify.
+ * @param rhs The right operand.
+ * @return A reference to @p lhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T&
+operator|=(T& lhs, T rhs) noexcept
+{
+    lhs = lhs | rhs;
+    return lhs;
+}
+
+/**
+ * Bitwise exclusive OR assignment.
+ *
+ * @param lhs The value to modify.
+ * @param rhs The right operand.
+ * @return A reference to @p lhs.
+ */
+template <enum_bitops::Candidate T>
+constexpr T&
+operator^=(T& lhs, T rhs) noexcept
+{
+    lhs = lhs ^ rhs;
+    return lhs;
+}
+
+/** @} */
+
+}  // namespace xrpl

include/xrpl/basics/safe_cast.h

@@ -2,107 +2,212 @@
 
 #include <xrpl/beast/utility/instrumentation.h>  // IWYU pragma: keep
 
+#include <concepts>
+#include <cstdint>
+#include <limits>
+#include <memory>
 #include <type_traits>
+#include <utility>
 
 namespace xrpl {
 
-// safe_cast adds compile-time checks to a static_cast to ensure that
-// the destination can hold all values of the source.  This is particularly
-// handy when the source or destination is an enumeration type.
+/** Every value of @p Src can be represented by @p Dest.
 
-template <class Src, class Dest>
-concept SafeToCast = (std::is_integral_v<Src> && std::is_integral_v<Dest>) &&
-    (std::is_signed_v<Src> || std::is_unsigned_v<Dest>) &&
-    (std::is_signed_v<Src> != std::is_signed_v<Dest> ? sizeof(Dest) > sizeof(Src)
-                                                     : sizeof(Dest) >= sizeof(Src));
+    Given two integral types, the cast is safe when the destination can
+    hold every possible value of the source.
 
-template <class Dest, class Src>
+    Comparing the bounds requires care: we use @c std::cmp_less_equal and
+    @c std::cmp_greater_equal; the plain relational operators would apply
+    arithmetic conversions, resulting in incorrect results when comparing
+    across signedness.
+
+    Because @c std::cmp_* requires standard signed or unsigned integer
+    arguments, which excludes character types and bool, we first widen
+    all type bounds to the maximum-width integer type while preserving
+    signedness.
+
+    @note Extended integer types, like __int128 on gcc, cannot be safely
+          widened to a standard integer type, so the concept will reject
+          them.
+*/
+template <typename Src, typename Dest>
+concept SafeToCast = std::is_integral_v<Src> && std::is_integral_v<Dest> && []() consteval {
+    using WideSrc = std::conditional_t<std::is_signed_v<Src>, std::intmax_t, std::uintmax_t>;
+    using WideDest = std::conditional_t<std::is_signed_v<Dest>, std::intmax_t, std::uintmax_t>;
+
+    // Note: this guard must be an evaluated branch, and not a
+    // static_assert. The lambda body is outside the immediate
+    // context, so a substitution-time failure here would be a
+    // hard error rather than leaving the concept unsatisfied.
+    if constexpr (sizeof(Src) > sizeof(WideSrc) || sizeof(Dest) > sizeof(WideDest))
+    {
+        return false;
+    }
+    else
+    {
+        return std::cmp_less_equal(
+                   static_cast<WideDest>(std::numeric_limits<Dest>::min()),
+                   static_cast<WideSrc>(std::numeric_limits<Src>::min())) &&
+            std::cmp_greater_equal(
+                   static_cast<WideDest>(std::numeric_limits<Dest>::max()),
+                   static_cast<WideSrc>(std::numeric_limits<Src>::max()));
+    }
+}();
+
+/** Compile-time-checked static_cast that rejects non-value preserving casts.
+
+    @note There is deliberately no enum-to-enum overload, and no overload
+          returning the underlying type of an enum. For the latter, use
+          @c std::to_underlying.
+*/
+/** @{ */
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 safeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 {
     static_assert(
-        std::is_signed_v<Dest> || std::is_unsigned_v<Src>, "Cannot cast signed to unsigned");
-    constexpr unsigned kNotSame = std::is_signed_v<Dest> != std::is_signed_v<Src>;
-    static_assert(
-        sizeof(Dest) >= sizeof(Src) + kNotSame,
-        "Destination is too small to hold all values of source");
+        SafeToCast<Src, Dest>, "This cast is not value-preserving. Please use unsafeCast instead.");
     return static_cast<Dest>(s);
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 safeCast(Src s) noexcept
-    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 {
     return static_cast<Dest>(safeCast<std::underlying_type_t<Dest>>(s));
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 constexpr Dest
 safeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 {
-    return safeCast<Dest>(static_cast<std::underlying_type_t<Src>>(s));
+    return safeCast<Dest>(std::to_underlying(s));
 }
+/** @} */
 
-// unsafe_cast explicitly flags a static_cast as not necessarily able to hold
-// all values of the source. It includes a compile-time check so that if
-// underlying types become safe, it can be converted to a safe_cast.
+/** Integral-to-integral cast that is known to be narrowing or sign-erasing.
 
-template <class Dest, class Src>
+    This explicitly flags a conversion that can lose information for some
+    values of the source type, where the call site accepts that loss (or
+    truncation is the intended behavior).
+
+    The compile-time check ensures the cast remains "unsafe": if the types
+    involved later change such that the conversion becomes inherently
+    value-preserving, the static assertion fires with instructions to
+    migrate the call site to @ref safeCast.
+
+    If the conversion's safety depends on a runtime precondition rather
+    than on the types, or varies across instantiations of generic code,
+    use @ref checkedCast instead.
+*/
+/** @{ */
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 unsafeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 {
     static_assert(
-        !SafeToCast<Src, Dest>,
-        "Only unsafe if casting signed to unsigned or "
-        "destination is too small");
+        !SafeToCast<Src, Dest>, "This cast is value-preserving. Please use safeCast instead.");
     return static_cast<Dest>(s);
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 unsafeCast(Src s) noexcept
-    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 {
     return static_cast<Dest>(unsafeCast<std::underlying_type_t<Dest>>(s));
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 constexpr Dest
 unsafeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 {
-    return unsafeCast<Dest>(static_cast<std::underlying_type_t<Src>>(s));
+    return unsafeCast<Dest>(std::to_underlying(s));
+}
+/** @} */
+
+/** Integral-to-integral cast when the caller has performed a bounds check.
+
+    This documents that a runtime precondition or external invariant, which
+    is not necessarily visible to the compiler, guarantees that the requested
+    conversion is value-preserving for the values that can actually occur.
+
+    This is primarily meant for generic code, where the same expression may
+    be value-preserving for one instantiation but not for another, making
+    both @ref safeCast and @ref unsafeCast unusable.
+
+    Unlike @ref safeCast and @ref unsafeCast, this imposes no static check
+    on the type relationship: the caller's claim is about runtime values,
+    not about types.
+*/
+/** @{ */
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
+constexpr Dest
+checkedCast(Src s) noexcept
+{
+    return static_cast<Dest>(s);
 }
 
+template <typename Dest, typename Src>
+    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
+constexpr Dest
+checkedCast(Src s) noexcept
+{
+    return static_cast<Dest>(checkedCast<std::underlying_type_t<Dest>>(s));
+}
+
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
+constexpr Dest
+checkedCast(Src s) noexcept
+{
+    return checkedCast<Dest>(std::to_underlying(s));
+}
+/** @} */
+
+/** Downcast within a class hierarchy, verified in debug builds.
+
+    Performs a static_cast down a hierarchy, but in debug builds verifies
+    via dynamic_cast that the object's dynamic type actually permits the
+    downcast. Both build modes execute the same conversion; debug builds
+    merely add the check.
+
+    The pointer form passes null through unchanged, as dynamic_cast does.
+
+    @note The check requires @p Src to be polymorphic; in release builds
+          an invalid downcast is undefined behavior on use, exactly as
+          with a bare static_cast.
+*/
+/** @{ */
 template <class Dest, class Src>
-    requires std::is_pointer_v<Dest>
+    requires(
+        std::is_pointer_v<Dest> && std::is_polymorphic_v<Src> &&
+        std::derived_from<std::remove_pointer_t<Dest>, Src> &&
+        (std::is_const_v<std::remove_pointer_t<Dest>> || !std::is_const_v<Src>) &&
+        (std::is_volatile_v<std::remove_pointer_t<Dest>> || !std::is_volatile_v<Src>))
 inline Dest
 safeDowncast(Src* s) noexcept
 {
-#ifdef NDEBUG
+    XRPL_ASSERT(
+        s == nullptr || dynamic_cast<Dest>(s) != nullptr, "xrpl::safeDowncast : valid downcast");
     return static_cast<Dest>(s);  // NOLINT(cppcoreguidelines-pro-type-static-cast-downcast)
-#else
-    auto* result = dynamic_cast<Dest>(s);
-    XRPL_ASSERT(result != nullptr, "xrpl::safeDowncast : pointer downcast is valid");
-    return result;
-#endif
 }
 
 template <class Dest, class Src>
-    requires std::is_lvalue_reference_v<Dest>
+    requires(
+        std::is_lvalue_reference_v<Dest> && std::is_polymorphic_v<Src> &&
+        std::derived_from<std::remove_reference_t<Dest>, Src>)
 inline Dest
 safeDowncast(Src& s) noexcept
 {
-#ifndef NDEBUG
-    XRPL_ASSERT(
-        dynamic_cast<std::add_pointer_t<std::remove_reference_t<Dest>>>(&s) != nullptr,
-        "xrpl::safeDowncast : reference downcast is valid");
-#endif
-    return static_cast<Dest>(s);  // NOLINT(cppcoreguidelines-pro-type-static-cast-downcast)
+    return *safeDowncast<std::add_pointer_t<std::remove_reference_t<Dest>>>(std::addressof(s));
 }
+/** @} */
 
 }  // namespace xrpl

include/xrpl/basics/spinlock.h

@@ -4,88 +4,215 @@
 
 #include <xrpl/beast/utility/instrumentation.h>
 
+#include <boost/predef/architecture.h>
+
 #include <atomic>
+#include <concepts>
 #include <limits>
 #include <type_traits>
 
-#ifndef __aarch64__
+#if BOOST_ARCH_X86
 #include <immintrin.h>
 #endif
 
 namespace xrpl {
 
+/** An unsigned integral type suitable for use as a spinlock.
+
+    The type must be always lock-free when wrapped in std::atomic, so
+    that lock operations cannot themselves take a (library-level) lock.
+ */
+template <typename T>
+concept SpinlockValueType = std::is_unsigned_v<T> && std::atomic<T>::is_always_lock_free;
+
+/** A spinlock value type that additionally supports the atomic bitwise
+    operations required to pack multiple locks into a single integer.
+ */
+template <typename T>
+concept PackedSpinlockValueType = SpinlockValueType<T> && requires(std::atomic<T>& a, T v) {
+    { a.fetch_or(v) } -> std::same_as<T>;
+    { a.fetch_and(v) } -> std::same_as<T>;
+};
+
 namespace detail {
-/**
- * Inform the processor that we are in a tight spin-wait loop.
- *
- * Spinlocks caught in tight loops can result in the processor's pipeline
- * filling up with comparison operations, resulting in a misprediction at
- * the time the lock is finally acquired, necessitating pipeline flushing
- * which is ridiculously expensive and results in very high latency.
- *
- * This function instructs the processor to "pause" for some architecture
- * specific amount of time, to prevent this.
+
+/** Inform the processor that we are in a tight spin-wait loop.
+
+    Spinlocks caught in tight loops can result in the processor's pipeline
+    filling up with comparison operations, resulting in a misprediction at
+    the time the lock is finally acquired, necessitating pipeline flushing
+    which is ridiculously expensive and results in very high latency.
+
+    This function instructs the processor to "pause" for some architecture
+    specific amount of time, to prevent this.
  */
 inline void
 spinPause() noexcept
 {
-#ifdef __aarch64__
-    asm volatile("yield");
-#else
+#if BOOST_ARCH_X86
     _mm_pause();
+#elif BOOST_ARCH_ARM
+    asm volatile("yield" ::: "memory");
+#else
+#error No implementation available for spinPause to use
 #endif
 }
 
 }  // namespace detail
 
-/** @{ */
-/**
- * Classes to handle arrays of spinlocks packed into a single atomic integer:
- *
- * Packed spinlocks allow for tremendously space-efficient lock-sharding
- * but they come at a cost.
- *
- * First, the implementation is necessarily low-level and uses advanced
- * features like memory ordering and highly platform-specific tricks to
- * maximize performance. This imposes a significant and ongoing cost to
- * developers.
- *
- * Second, and perhaps most important, is that the packing of multiple
- * locks into a single integer which, albeit space-efficient, also has
- * performance implications stemming from data dependencies, increased
- * cache-coherency traffic between processors and heavier loads on the
- * processor's load/store units.
- *
- * To be sure, these locks can have advantages but they are definitely
- * not general purpose locks and should not be thought of or used that
- * way. The use cases for them are likely few and far between; without
- * a compelling reason to use them, backed by profiling data, it might
- * be best to use one of the standard locking primitives instead. Note
- * that in most common platforms, `std::mutex` is so heavily optimized
- * that it can, usually, outperform spinlocks.
- *
- * @tparam T An unsigned integral type (e.g. std::uint16_t)
- */
+//------------------------------------------------------------------------------
 
-/**
- * A class that grabs a single packed spinlock from an atomic integer.
- *
- * This class meets the requirements of Lockable:
- *     https://en.cppreference.com/w/cpp/named_req/Lockable
+/** Attempt to acquire a spinlock without blocking.
+
+    @note This interface is primarily intended for one-shot attempts to
+          acquire the lock. Avoid calling this function directly from a
+          loop and use @ref spinLock instead.
+
+    @tparam T An unsigned integral type.
+    @param lock The atomic variable used as the lock.
+    @return true if the lock was acquired, false if it was already held.
  */
-template <class T>
+template <SpinlockValueType T>
+[[nodiscard]] bool
+spinTryLock(std::atomic<T>& lock) noexcept
+{
+    // A compare-exchange is required here, not an unconditional exchange:
+    // a failed attempt must not modify the lock word, in case the atomic
+    // is shared with PackedSpinlock).
+    T expected = 0;
+
+    return lock.compare_exchange_strong(
+        expected,
+        std::numeric_limits<T>::max(),
+        std::memory_order::acquire,
+        std::memory_order::relaxed);
+    ;
+}
+
+/** Acquire a spinlock, blocking until available.
+
+    Uses a TTAS (test-and-test-and-set) pattern, so waiters share the cache
+    line read-only, helping to avoid unnecessary coherency traffic.
+
+    @tparam T An unsigned integral type.
+    @param lock The atomic variable used as the lock.
+ */
+template <SpinlockValueType T>
+void
+spinLock(std::atomic<T>& lock) noexcept
+{
+    do
+    {
+        // Relaxed ordering is sufficient for the spin: this load is only
+        // a filter. The acquire on the successful exchange in spinTryLock
+        // is what synchronizes the critical section.
+        while (lock.load(std::memory_order::relaxed) != 0)
+            detail::spinPause();
+    } while (!spinTryLock(lock));
+}
+
+/** Release a spinlock.
+
+    @tparam T An unsigned integral type.
+    @param lock The atomic variable used as the lock.
+ */
+template <SpinlockValueType T>
+void
+spinUnlock(std::atomic<T>& lock) noexcept
+{
+    lock.store(0, std::memory_order::release);
+}
+
+//------------------------------------------------------------------------------
+
+/** A Lockable interface to a spinlock implemented on top of an atomic.
+
+    @tparam T An unsigned integral type.
+
+    @note Using `PackedSpinlock` and `Spinlock` against the same underlying
+          atomic integer is possible but can result in `Spinlock` not being
+          able to acquire the lock during periods of high contention due to
+          the way the two locks operate: `Spinlock` spins and tries to grab
+          all the bits at once, whereas any given `PackedSpinlock` instance
+          only tries to grab one bit at a time. Caveat emptor.
+
+    This class meets the requirements of Lockable:
+        https://en.cppreference.com/w/cpp/named_req/Lockable
+ */
+template <SpinlockValueType T>
+class Spinlock
+{
+    std::atomic<T>& lock_;
+
+public:
+    Spinlock(Spinlock const&) = delete;
+    Spinlock&
+    operator=(Spinlock const&) = delete;
+
+    /** Construct a spinlock handle.
+
+        @param lock The atomic integer to spin against.
+
+        @note For performance reasons, you should strive to have `lock` be
+              on a cacheline by itself.
+     */
+    explicit Spinlock(std::atomic<T>& lock) noexcept : lock_(lock)
+    {
+    }
+
+    [[nodiscard]] bool
+    try_lock() noexcept  // NOLINT(readability-identifier-naming)
+    {
+        return spinTryLock(lock_);
+    }
+
+    void
+    lock() noexcept
+    {
+        spinLock(lock_);
+    }
+
+    void
+    unlock() noexcept
+    {
+        spinUnlock(lock_);
+    }
+};
+
+//------------------------------------------------------------------------------
+
+/** A Lockable interface to a packed spinlock implemented on top of an atomic.
+
+    Packed spinlocks offer tremendous space-efficient lock-sharding but
+    they come at a cost.
+
+    First, the implementation is necessarily low-level and uses advanced
+    features like memory ordering and highly platform-specific tricks to
+    maximize performance. This imposes a significant and ongoing cost to
+    developers.
+
+    Second, and perhaps most important, is that the packing of multiple
+    locks into a single integer which, albeit space-efficient, also has
+    performance implications stemming from data dependencies, increased
+    cache-coherency traffic between processors and heavier loads on the
+    processor's load/store units.
+
+    To be sure, these locks can have advantages but they are definitely
+    not general purpose locks and should not be thought of or used that
+    way. The use cases for them are likely few and far between; without
+    a compelling reason to use them, backed by profiling data, it might
+    be best to use one of the standard locking primitives instead. Note
+    that in most common platforms, `std::mutex` is so heavily optimized
+    that it can, usually, outperform spinlocks.
+
+    @tparam T An unsigned integral type (e.g. std::uint16_t)
+
+    This class meets the requirements of Lockable:
+        https://en.cppreference.com/w/cpp/named_req/Lockable
+ */
+template <PackedSpinlockValueType T>
 class PackedSpinlock
 {
-    // clang-format off
-    static_assert(std::is_unsigned_v<T>);
-    static_assert(std::atomic<T>::is_always_lock_free);
-    static_assert(
-        std::is_same_v<decltype(std::declval<std::atomic<T>&>().fetch_or(0)), T> &&
-        std::is_same_v<decltype(std::declval<std::atomic<T>&>().fetch_and(0)), T>,
-        "std::atomic<T>::fetch_and(T) and std::atomic<T>::fetch_and(T) are required by packed_spinlock");
-    // clang-format on
-
-private:
     std::atomic<T>& bits_;
     T const mask_;
 
@@ -94,120 +221,49 @@ public:
     PackedSpinlock&
     operator=(PackedSpinlock const&) = delete;
 
-    /**
-     * A single spinlock packed inside the specified atomic
-     *
-     * @param lock The atomic integer inside which the spinlock is packed.
-     * @param index The index of the spinlock this object acquires.
-     *
-     * @note For performance reasons, you should strive to have `lock` be
-     *       on a cacheline by itself.
+    /** Construct a packed spinlock handle for a single bit.
+
+        @param lock The atomic integer inside which the spinlock is packed.
+        @param index The index of the spinlock this object acquires.
+
+        @note For performance reasons, you should strive to have `lock` be
+              on a cacheline by itself.
      */
-    PackedSpinlock(std::atomic<T>& lock, int index) : bits_(lock), mask_(static_cast<T>(1) << index)
-    {
-        XRPL_ASSERT(
-            index >= 0 && (mask_ != 0),
-            "xrpl::PackedSpinlock::PackedSpinlock : valid index and mask");
-    }
-
-    [[nodiscard]] bool
-    try_lock()  // NOLINT(readability-identifier-naming)
-    {
-        return (bits_.fetch_or(mask_, std::memory_order_acquire) & mask_) == 0;
-    }
-
-    void
-    lock()
-    {
-        while (!try_lock())
-        {
-            // The use of relaxed memory ordering here is intentional and
-            // serves to help reduce cache coherency traffic during times
-            // of contention by avoiding writes that would definitely not
-            // result in the lock being acquired.
-            while ((bits_.load(std::memory_order_relaxed) & mask_) != 0)
-                detail::spinPause();
-        }
-    }
-
-    void
-    unlock()
-    {
-        bits_.fetch_and(~mask_, std::memory_order_release);
-    }
-};
-
-/**
- * A spinlock implemented on top of an atomic integer.
- *
- * @note Using `packed_spinlock` and `spinlock` against the same underlying
- *       atomic integer can result in `spinlock` not being able to actually
- *       acquire the lock during periods of high contention, because of how
- *       the two locks operate: `spinlock` will spin trying to grab all the
- *       bits at once, whereas any given `packed_spinlock` will only try to
- *       grab one bit at a time. Caveat emptor.
- *
- * This class meets the requirements of Lockable:
- *     https://en.cppreference.com/w/cpp/named_req/Lockable
- */
-template <class T>
-class Spinlock
-{
-    static_assert(std::is_unsigned_v<T>);
-    static_assert(std::atomic<T>::is_always_lock_free);
-
-private:
-    std::atomic<T>& lock_;
-
-public:
-    Spinlock(Spinlock const&) = delete;
-    Spinlock&
-    operator=(Spinlock const&) = delete;
-
-    /**
-     * Grabs the
-     *
-     * @param lock The atomic integer to spin against.
-     *
-     * @note For performance reasons, you should strive to have `lock` be
-     *       on a cacheline by itself.
-     */
-    Spinlock(std::atomic<T>& lock) : lock_(lock)
+    PackedSpinlock(std::atomic<T>& lock, int index) noexcept
+        : bits_(lock), mask_([index]() {
+            XRPL_ASSERT(
+                index >= 0 && index < std::numeric_limits<T>::digits,
+                "xrpl::PackedSpinlock::PackedSpinlock : valid index");
+            return static_cast<T>(T{1} << index);
+        }())
     {
     }
 
     [[nodiscard]] bool
-    try_lock()  // NOLINT(readability-identifier-naming)
+    try_lock() noexcept  // NOLINT(readability-identifier-naming)
     {
-        T expected = 0;
-
-        return lock_.compare_exchange_weak(
-            expected,
-            std::numeric_limits<T>::max(),
-            std::memory_order_acquire,
-            std::memory_order_relaxed);
+        return (bits_.fetch_or(mask_, std::memory_order::acquire) & mask_) == 0;
     }
 
     void
-    lock()
+    lock() noexcept
     {
-        while (!try_lock())
+        do
         {
             // The use of relaxed memory ordering here is intentional and
             // serves to help reduce cache coherency traffic during times
-            // of contention by avoiding writes that would definitely not
-            // result in the lock being acquired.
-            while (lock_.load(std::memory_order_relaxed) != 0)
+            // of contention by avoiding writes that are unlikely to grab
+            // the requested lock.
+            while ((bits_.load(std::memory_order::relaxed) & mask_) != 0)
                 detail::spinPause();
-        }
+        } while (!try_lock());
     }
 
     void
-    unlock()
+    unlock() noexcept
     {
-        lock_.store(0, std::memory_order_release);
+        bits_.fetch_and(~mask_, std::memory_order::release);
     }
 };
-/** @} */
 
 }  // namespace xrpl

include/xrpl/beast/type_name.h

@@ -1,47 +0,0 @@
-#pragma once
-
-#include <cstdlib>
-#include <string>
-#include <type_traits>
-#include <typeinfo>
-
-#ifndef _MSC_VER
-#include <cxxabi.h>
-#endif
-
-namespace beast {
-
-template <typename T>
-std::string
-typeName()
-{
-    using TR = std::remove_reference_t<T>;
-
-    std::string name = typeid(TR).name();
-
-#ifndef _MSC_VER
-    if (auto s = abi::__cxa_demangle(name.c_str(), nullptr, nullptr, nullptr))
-    {
-        name = s;
-        // NOLINTNEXTLINE(cppcoreguidelines-no-malloc)
-        std::free(s);
-    }
-#endif
-
-    if (std::is_const_v<TR>)
-        name += " const";
-    if (std::is_volatile_v<TR>)
-        name += " volatile";
-    if (std::is_lvalue_reference_v<T>)
-    {
-        name += "&";
-    }
-    else if (std::is_rvalue_reference_v<T>)
-    {
-        name += "&&";
-    }
-
-    return name;
-}
-
-}  // namespace beast

include/xrpl/beast/utility/Zero.h

@@ -2,26 +2,24 @@
 
 #pragma once
 
+#include <compare>
+#include <concepts>
+
 namespace beast {
 
 /**
  * Zero allows classes to offer efficient comparisons to zero.
  *
- * Zero is a struct to allow classes to efficiently compare with zero without
- * requiring an rvalue construction.
- *
  * It's often the case that we have classes which combine a number and a unit.
  * In such cases, comparisons like t > 0 or t != 0 make sense, but comparisons
- * like t > 1 or t != 1 do not.
+ * like t > 1 or t != 1 do not. Comparing against kZero expresses exactly that,
+ * without constructing a T.
  *
- * The class Zero allows such comparisons to be easily made.
- *
- * The comparing class T either needs to have a method called signum() which
- * returns a positive number, 0, or a negative; or there needs to be a signum
- * function which resolves in the namespace which takes an instance of T and
- * returns a positive, zero or negative number.
+ * A type T participates if either `t.signum()` or an unqualified `signum(t)`
+ * found by argument-dependent lookup returns an integer that is negative,
+ * zero, or positive according to the sign of t. Both `t == kZero` and
+ * `kZero == t` work, as do all six relational operators in either order.
  */
-
 struct Zero
 {
     explicit Zero() = default;
@@ -30,115 +28,44 @@ struct Zero
 inline constexpr Zero kZero{};
 
 /**
- * Default implementation of signum calls the method on the class.
+ * Default implementation of signum: call the member function.
  */
-template <typename T>
-auto
-signum(T const& t)
+template <class T>
+    requires requires(T const& t) {
+        { t.signum() } -> std::integral;
+    }
+[[nodiscard]] constexpr auto
+signum(T const& t) noexcept(noexcept(t.signum()))
 {
     return t.signum();
 }
 
-namespace detail::zero_helper {
+namespace detail {
 
-// For argument dependent lookup to function properly, calls to signum must
-// be made from a namespace that does not include overloads of the function..
+/**
+ * A type with a usable signum: either the member-based default above, or a
+ * `signum(t)` overload in T's own namespace, found by ADL. A user overload
+ * that is a better match than the template wins, as usual.
+ */
 template <class T>
-auto
-callSignum(T const& t)
+concept HasSignum = requires(T const& t) {
+    { signum(t) } -> std::integral;
+};
+
+}  // namespace detail
+
+template <detail::HasSignum T>
+[[nodiscard]] constexpr bool
+operator==(T const& t, Zero) noexcept(noexcept(signum(t)))
 {
-    return signum(t);
+    return signum(t) == 0;
 }
 
-}  // namespace detail::zero_helper
-
-// Handle operators where T is on the left side using signum.
-
-template <typename T>
-bool
-operator==(T const& t, Zero)
+template <detail::HasSignum T>
+[[nodiscard]] constexpr std::strong_ordering
+operator<=>(T const& t, Zero) noexcept(noexcept(signum(t)))
 {
-    return detail::zero_helper::callSignum(t) == 0;
-}
-
-template <typename T>
-bool
-operator!=(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) != 0;
-}
-
-template <typename T>
-bool
-operator<(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) < 0;
-}
-
-template <typename T>
-bool
-operator>(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) > 0;
-}
-
-template <typename T>
-bool
-operator>=(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) >= 0;
-}
-
-template <typename T>
-bool
-operator<=(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) <= 0;
-}
-
-// Handle operators where T is on the right side by
-// reversing the operation, so that T is on the left side.
-
-template <typename T>
-bool
-operator==(Zero, T const& t)
-{
-    return t == kZero;
-}
-
-template <typename T>
-bool
-operator!=(Zero, T const& t)
-{
-    return t != kZero;
-}
-
-template <typename T>
-bool
-operator<(Zero, T const& t)
-{
-    return t > kZero;
-}
-
-template <typename T>
-bool
-operator>(Zero, T const& t)
-{
-    return t < kZero;
-}
-
-template <typename T>
-bool
-operator>=(Zero, T const& t)
-{
-    return t <= kZero;
-}
-
-template <typename T>
-bool
-operator<=(Zero, T const& t)
-{
-    return t >= kZero;
+    return signum(t) <=> 0;
 }
 
 }  // namespace beast

include/xrpl/ledger/ApplyView.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <xrpl/basics/base_uint.h>
-#include <xrpl/basics/safe_cast.h>
+#include <xrpl/basics/enum_bitops.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/OwnerCounts.h>
 #include <xrpl/ledger/ReadView.h>
@@ -22,80 +22,39 @@
 
 namespace xrpl {
 
-// Bitwise flag enum with existing operator overloads
-// NOLINTNEXTLINE(cppcoreguidelines-use-enum-class)
-enum ApplyFlags : std::uint32_t {
-    TapNone = 0x00,
+enum class ApplyFlags : std::uint32_t {
+    None = 0x00,
 
     // This is a local transaction with the
     // fail_hard flag set.
-    TapFailHard = 0x10,
+    FailHard = 0x10,
 
     // This is not the transaction's last pass
     // Transaction can be retried, soft failures allowed
-    TapRetry = 0x20,
+    Retry = 0x20,
 
     // Transaction came from a privileged source
-    TapUnlimited = 0x400,
+    Unlimited = 0x400,
 
     // Transaction is executing as part of a batch
-    TapBatch = 0x800,
+    Batch = 0x800,
 
     // Transaction shouldn't be applied
     // Signatures shouldn't be checked
-    TapDryRun = 0x1000,
+    DryRun = 0x1000,
 
     // Transaction is being preflighted as the payload of a
     // TransactionProposalCreate. Its signatures are collected on-ledger
     // afterward, so signature-presence checks (e.g. Batch signer matching)
     // are skipped at proposal-creation time (On-Chain Cosigner spec
     // §5.3.1.2).
-    TapProposal = 0x2000
+    Proposal = 0x2000
 };
 
-constexpr ApplyFlags
-operator|(ApplyFlags const& lhs, ApplyFlags const& rhs)
+template <>
+struct enum_bitops::OptIn<ApplyFlags> : std::true_type
 {
-    return safeCast<ApplyFlags>(
-        safeCast<std::underlying_type_t<ApplyFlags>>(lhs) |
-        safeCast<std::underlying_type_t<ApplyFlags>>(rhs));
-}
-
-static_assert((TapFailHard | TapRetry) == safeCast<ApplyFlags>(0x30u), "ApplyFlags operator |");
-static_assert((TapRetry | TapFailHard) == safeCast<ApplyFlags>(0x30u), "ApplyFlags operator |");
-
-constexpr ApplyFlags
-operator&(ApplyFlags const& lhs, ApplyFlags const& rhs)
-{
-    return safeCast<ApplyFlags>(
-        safeCast<std::underlying_type_t<ApplyFlags>>(lhs) &
-        safeCast<std::underlying_type_t<ApplyFlags>>(rhs));
-}
-
-static_assert((TapFailHard & TapRetry) == TapNone, "ApplyFlags operator &");
-static_assert((TapRetry & TapFailHard) == TapNone, "ApplyFlags operator &");
-
-constexpr ApplyFlags
-operator~(ApplyFlags const& flags)
-{
-    return safeCast<ApplyFlags>(~safeCast<std::underlying_type_t<ApplyFlags>>(flags));
-}
-
-static_assert(~TapRetry == safeCast<ApplyFlags>(0xFFFFFFDFu), "ApplyFlags operator ~");
-
-inline ApplyFlags
-operator|=(ApplyFlags& lhs, ApplyFlags const& rhs)
-{
-    lhs = lhs | rhs;
-    return lhs;
-}
-
-inline ApplyFlags
-operator&=(ApplyFlags& lhs, ApplyFlags const& rhs)
-{
-    lhs = lhs & rhs;
-    return lhs;
-}
+};
 
 //------------------------------------------------------------------------------
 

include/xrpl/ledger/entries/LedgerHashesEntry.h

@@ -1,11 +1,17 @@
 #pragma once
 
+#include <xrpl/basics/base_uint.h>
 #include <xrpl/beast/utility/Journal.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
 #include <xrpl/ledger/entries/SLEBase.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/LedgerFormats.h>
+#include <xrpl/protocol/SField.h>
+#include <xrpl/protocol/STVector256.h>
+
+#include <cstddef>
+#include <optional>
 
 namespace xrpl {
 
@@ -25,6 +31,31 @@ public:
         : Base(keylet::skip(), view, j)
     {
     }
+
+    /**
+     * Looks up a hash `diff` slots back from the most recent entry in the
+     * sfHashes vector (diff == 0 is the most recent entry).
+     *
+     * Callers decide which skip list entry to read and how to translate a
+     * target ledger sequence into `diff`; this only does the bounds check
+     * and vector indexing shared by both the recent (stride 1) and distant
+     * (stride 256) skip lists.
+     *
+     * @param diff how many slots back from the most recent hash to look up;
+     * 0 is the most recent hash.
+     * @return the hash at that slot, or std::nullopt if the entry does not
+     * exist or `diff` is out of range.
+     */
+    [[nodiscard]] std::optional<UInt256>
+    hashAt(std::size_t diff) const
+    {
+        if (!this->exists())
+            return std::nullopt;
+        STVector256 const vec = (*this)->getFieldV256(sfHashes);
+        if (vec.size() > diff)
+            return vec[vec.size() - diff - 1];
+        return std::nullopt;
+    }
 };
 
 using LedgerHashesEntryR = LedgerHashesEntry<ReadView>;

include/xrpl/protocol/AccountID.h

@@ -101,22 +101,6 @@ operator<<(std::ostream& os, AccountID const& x)
     return os;
 }
 
-/**
- * Initialize the global cache used to map AccountID to base58 conversions.
- *
- * The cache is optional and need not be initialized. But because conversion
- * is expensive (it requires a SHA-256 operation) in most cases the overhead
- * of the cache is worth the benefit.
- *
- * @param count The number of entries the cache should accommodate. Zero will
- *              disable the cache, releasing any memory associated with it.
- *
- * @note The function will only initialize the cache the first time it is
- *       invoked. Subsequent invocations do nothing.
- */
-void
-initAccountIdCache(std::size_t count);
-
 }  // namespace xrpl
 
 //------------------------------------------------------------------------------

include/xrpl/protocol/KnownFormats.h

@@ -1,10 +1,10 @@
 #pragma once
 
 #include <xrpl/basics/contract.h>
-#include <xrpl/beast/type_name.h>
 #include <xrpl/protocol/SOTemplate.h>
 
 #include <boost/container/flat_map.hpp>
+#include <boost/core/type_name.hpp>
 
 #include <algorithm>
 #include <cstddef>
@@ -84,7 +84,7 @@ public:
      * Derived classes will load the object with all the known formats.
      */
 private:
-    KnownFormats() : name_(beast::typeName<Derived>())
+    KnownFormats() : name_(boost::core::type_name<Derived>())
     {
     }
 

include/xrpl/protocol/STPathSet.h

@@ -2,6 +2,7 @@
 
 #include <xrpl/basics/CountedObject.h>
 #include <xrpl/basics/UnorderedContainers.h>
+#include <xrpl/basics/enum_bitops.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/json/json_value.h>
 #include <xrpl/protocol/AccountID.h>
@@ -15,6 +16,7 @@
 #include <cstdint>
 #include <memory>
 #include <optional>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -22,18 +24,8 @@ namespace xrpl {
 
 class STPathElement final : public CountedObject<STPathElement>
 {
-    unsigned int type_;
-    AccountID accountID_;
-    PathAsset assetID_;
-    AccountID issuerID_;
-
-    bool isOffer_;
-    std::size_t hashValue_;
-
 public:
-    // Bitwise values (typeCurrency | typeMPT)
-    // NOLINTNEXTLINE(cppcoreguidelines-use-enum-class)
-    enum Type {
+    enum class Type : std::uint8_t {
         TypeNone = 0x00,
         TypeAccount = 0x01,   // Rippling through an account (vs taking an offer).
         TypeCurrency = 0x10,  // Currency follows.
@@ -45,6 +37,8 @@ public:
         // Combination of all types.
     };
 
+    using enum Type;
+
     STPathElement();
     STPathElement(STPathElement const&) = default;
     STPathElement&
@@ -62,42 +56,42 @@ public:
         bool forceAsset = false);
 
     STPathElement(
-        unsigned int uType,
+        Type type,
         AccountID const& account,
         PathAsset const& asset,
         AccountID const& issuer);
 
-    [[nodiscard]] std::uint32_t
-    getNodeType() const;
+    [[nodiscard]] Type
+    getNodeType() const noexcept;
 
     [[nodiscard]] bool
-    isOffer() const;
+    isOffer() const noexcept;
 
     [[nodiscard]] bool
-    isAccount() const;
+    isAccount() const noexcept;
 
     [[nodiscard]] bool
-    hasIssuer() const;
+    hasIssuer() const noexcept;
 
     [[nodiscard]] bool
-    hasCurrency() const;
+    hasCurrency() const noexcept;
 
     [[nodiscard]] bool
-    hasMPT() const;
+    hasMPT() const noexcept;
 
     [[nodiscard]] bool
-    hasAsset() const;
+    hasAsset() const noexcept;
 
     [[nodiscard]] bool
-    isNone() const;
+    isNone() const noexcept;
 
     // Nodes are either an account ID or a offer prefix. Offer prefixs denote a
     // class of offers.
     [[nodiscard]] AccountID const&
-    getAccountID() const;
+    getAccountID() const noexcept;
 
     [[nodiscard]] PathAsset const&
-    getPathAsset() const;
+    getPathAsset() const noexcept;
 
     [[nodiscard]] Currency const&
     getCurrency() const;
@@ -106,17 +100,35 @@ public:
     getMPTID() const;
 
     [[nodiscard]] AccountID const&
-    getIssuerID() const;
+    getIssuerID() const noexcept;
 
     [[nodiscard]] bool
-    isType(Type const& pe) const;
+    isType(Type pe) const noexcept;
 
-    bool
-    operator==(STPathElement const& t) const;
+    friend bool
+    operator==(STPathElement const& lhs, STPathElement const& rhs) noexcept
+    {
+        return lhs.isType(TypeAccount) == rhs.isType(TypeAccount) &&
+            lhs.hashValue_ == rhs.hashValue_ && lhs.accountID_ == rhs.accountID_ &&
+            lhs.assetID_ == rhs.assetID_ && lhs.issuerID_ == rhs.issuerID_;
+    }
 
 private:
     static std::size_t
     getHash(STPathElement const& element);
+
+    Type type_;
+    AccountID accountID_;
+    PathAsset assetID_;
+    AccountID issuerID_;
+
+    bool isOffer_;
+    std::size_t hashValue_;
+};
+
+template <>
+struct enum_bitops::OptIn<STPathElement::Type> : std::true_type
+{
 };
 
 template <class Hasher>
@@ -124,7 +136,7 @@ void
 hash_append(Hasher& h, STPathElement const& e) noexcept
 {
     using beast::hash_append;
-    hash_append(h, (e.getNodeType() & STPathElement::TypeAccount) != 0u);
+    hash_append(h, e.isType(STPathElement::TypeAccount));
     hash_append(h, e.getAccountID());
     hash_append(h, e.getPathAsset());
     hash_append(h, e.getIssuerID());
@@ -404,11 +416,11 @@ inline STPathElement::STPathElement(
 }
 
 inline STPathElement::STPathElement(
-    unsigned int uType,
+    Type type,
     AccountID const& account,
     PathAsset const& asset,
     AccountID const& issuer)
-    : type_(uType)
+    : type_(type)
     , accountID_(account)
     , assetID_(asset)
     , issuerID_(issuer)
@@ -423,56 +435,56 @@ inline STPathElement::STPathElement(
     hashValue_ = getHash(*this);
 }
 
-inline std::uint32_t
-STPathElement::getNodeType() const
+inline STPathElement::Type
+STPathElement::getNodeType() const noexcept
 {
     return type_;
 }
 
 inline bool
-STPathElement::isOffer() const
+STPathElement::isOffer() const noexcept
 {
     return isOffer_;
 }
 
 inline bool
-STPathElement::isAccount() const
+STPathElement::isAccount() const noexcept
 {
     return !isOffer();
 }
 
 inline bool
-STPathElement::isType(Type const& pe) const
+STPathElement::isType(Type pe) const noexcept
 {
-    return (type_ & pe) != 0u;
+    return (type_ & pe) != STPathElement::TypeNone;
 }
 
 inline bool
-STPathElement::hasIssuer() const
+STPathElement::hasIssuer() const noexcept
 {
     return isType(STPathElement::TypeIssuer);
 }
 
 inline bool
-STPathElement::hasCurrency() const
+STPathElement::hasCurrency() const noexcept
 {
     return isType(STPathElement::TypeCurrency);
 }
 
 inline bool
-STPathElement::hasMPT() const
+STPathElement::hasMPT() const noexcept
 {
     return isType(STPathElement::TypeMpt);
 }
 
 inline bool
-STPathElement::hasAsset() const
+STPathElement::hasAsset() const noexcept
 {
     return isType(STPathElement::TypeAsset);
 }
 
 inline bool
-STPathElement::isNone() const
+STPathElement::isNone() const noexcept
 {
     return getNodeType() == STPathElement::TypeNone;
 }
@@ -480,13 +492,13 @@ STPathElement::isNone() const
 // Nodes are either an account ID or a offer prefix. Offer prefixs denote a
 // class of offers.
 inline AccountID const&
-STPathElement::getAccountID() const
+STPathElement::getAccountID() const noexcept
 {
     return accountID_;
 }
 
 inline PathAsset const&
-STPathElement::getPathAsset() const
+STPathElement::getPathAsset() const noexcept
 {
     return assetID_;
 }
@@ -504,18 +516,11 @@ STPathElement::getMPTID() const
 }
 
 inline AccountID const&
-STPathElement::getIssuerID() const
+STPathElement::getIssuerID() const noexcept
 {
     return issuerID_;
 }
 
-inline bool
-STPathElement::operator==(STPathElement const& t) const
-{
-    return (type_ & TypeAccount) == (t.type_ & TypeAccount) && hashValue_ == t.hashValue_ &&
-        accountID_ == t.accountID_ && assetID_ == t.assetID_ && issuerID_ == t.issuerID_;
-}
-
 // ------------ STPath ------------
 
 inline STPath::STPath(std::vector<STPathElement> p) : path_(std::move(p))

include/xrpl/protocol/TxFlags.h

@@ -238,6 +238,12 @@ inline constexpr FlagValue tfUniversalMask = ~tfUniversal;
         TF_FLAG(tfSponsorshipEnd, 0x00010000)                                                                                                                  \
         TF_FLAG(tfSponsorshipCreate, 0x00020000)                                                                                                               \
         TF_FLAG(tfSponsorshipReassign, 0x00040000),                                                                                                            \
+        MASK_ADJ(0))                                                                                                                                          \
+                                                                                                                                                               \
+    TRANSACTION(ConfidentialMPTHolderKeyUpdate,                                                                                                                \
+        TF_FLAG(tfHolderKeyRotation, 0x00010000)                                                                                                               \
+        TF_FLAG(tfHolderKeyRecovery, 0x00020000)                                                                                                               \
+        TF_FLAG(tfCancelRecovery, 0x00040000),                                                                                                                 \
         MASK_ADJ(0))
 
 // clang-format on

include/xrpl/protocol/detail/ledger_entries.macro

@@ -439,6 +439,7 @@ LEDGER_ENTRY(ltMPTOKEN, 0x007f, MPToken, mptoken, ({
     {sfIssuerKeyMirrorEpoch,        SoeOptional},
     {sfAuditorKeyMirrorEpoch,       SoeOptional},
     {sfHolderEncryptionKey,         SoeOptional},
+    {sfRecoveryKey,                 SoeOptional},
 }))
 
 /** A ledger object which tracks Oracle

include/xrpl/protocol/detail/sfields.macro

@@ -330,6 +330,7 @@ TYPED_SFIELD(sfAuditorEncryptionKey,        VL,     44)
 TYPED_SFIELD(sfAmountCommitment,            VL,     45)
 TYPED_SFIELD(sfBalanceCommitment,           VL,     46)
 TYPED_SFIELD(sfBytecode,                    VL,     47)
+TYPED_SFIELD(sfRecoveryKey,                 VL,     48)
 
 // account (common)
 TYPED_SFIELD(sfAccount,                  ACCOUNT,    1)

include/xrpl/protocol/detail/transactions.macro

@@ -1147,12 +1147,27 @@ TRANSACTION(ttCONFIDENTIAL_MPT_MIRROR_UPDATE, 92, ConfidentialMPTMirrorUpdate,
     {sfZKProof, SoeRequired},
 }))
 
+/** This transaction rotates or recovers a confidential MPT holder's ElGamal encryption key,
+    or cancels a recovery. */
+#if TRANSACTION_INCLUDE
+#   include <xrpl/tx/transactors/token/ConfidentialMPTHolderKeyUpdate.h>
+#endif
+TRANSACTION(ttCONFIDENTIAL_MPT_HOLDER_KEY_UPDATE, 93, ConfidentialMPTHolderKeyUpdate,
+    ({.amendment = featureConfidentialMPTKeyRotation}),
+    ({
+    {sfMPTokenIssuanceID, SoeRequired},
+    {sfHolderEncryptionKey, SoeOptional},
+    {sfConfidentialBalanceSpending, SoeOptional},
+    {sfConfidentialBalanceInbox, SoeOptional},
+    {sfZKProof, SoeOptional},
+}))
+
 /** This transaction posts an unsigned transaction on-ledger as a
     TransactionProposal, pending multi-signature collection. */
 #if TRANSACTION_INCLUDE
 #   include <xrpl/tx/transactors/proposal/TransactionProposalCreate.h>
 #endif
-TRANSACTION(ttTRANSACTION_PROPOSAL_CREATE, 93, TransactionProposalCreate,
+TRANSACTION(ttTRANSACTION_PROPOSAL_CREATE, 95, TransactionProposalCreate,
     ({.amendment = featureCosign}),
     ({
     {sfProposedTransaction, SoeRequired},

include/xrpl/protocol/jss.h

@@ -392,6 +392,7 @@ JSS(max_ledger);                  // in/out: LedgerCleaner
 JSS(max_queue_size);              // out: TxQ
 JSS(max_spend_drops);             // out: AccountInfo
 JSS(max_spend_drops_total);       // out: AccountInfo
+JSS(maximum);
 JSS(mean);                        // out: get_aggregate_price
 JSS(median);                      // out: get_aggregate_price
 JSS(median_fee);                  // out: TxQ

include/xrpl/protocol_autogen/ledger_entries/MPToken.h

@@ -339,6 +339,30 @@ public:
     {
         return this->sle_->isFieldPresent(sfHolderEncryptionKey);
     }
+
+    /**
+     * @brief Get sfRecoveryKey (SoeOptional)
+     * @return The field value, or std::nullopt if not present.
+     */
+    [[nodiscard]]
+    protocol_autogen::Optional<SF_VL::type::value_type>
+    getRecoveryKey() const
+    {
+        if (hasRecoveryKey())
+            return this->sle_->at(sfRecoveryKey);
+        return std::nullopt;
+    }
+
+    /**
+     * @brief Check if sfRecoveryKey is present.
+     * @return True if the field is present, false otherwise.
+     */
+    [[nodiscard]]
+    bool
+    hasRecoveryKey() const
+    {
+        return this->sle_->isFieldPresent(sfRecoveryKey);
+    }
 };
 
 /**
@@ -552,6 +576,17 @@ public:
         return *this;
     }
 
+    /**
+     * @brief Set sfRecoveryKey (SoeOptional)
+     * @return Reference to this builder for method chaining.
+     */
+    MPTokenBuilder&
+    setRecoveryKey(std::decay_t<typename SF_VL::type::value_type> const& value)
+    {
+        object_[sfRecoveryKey] = value;
+        return *this;
+    }
+
     /**
      * @brief Build and return the completed MPToken wrapper.
      * @param index The ledger entry index.

include/xrpl/protocol_autogen/transactions/ConfidentialMPTHolderKeyUpdate.h

@@ -0,0 +1,279 @@
+// This file is auto-generated. Do not edit.
+#pragma once
+
+#include <xrpl/protocol/STTx.h>
+#include <xrpl/protocol/STParsedJSON.h>
+#include <xrpl/protocol/jss.h>
+#include <xrpl/protocol_autogen/TransactionBase.h>
+#include <xrpl/protocol_autogen/TransactionBuilderBase.h>
+#include <xrpl/json/json_value.h>
+
+#include <stdexcept>
+#include <optional>
+
+namespace xrpl::transactions {
+
+class ConfidentialMPTHolderKeyUpdateBuilder;
+
+/**
+ * @brief Transaction: ConfidentialMPTHolderKeyUpdate
+ *
+ * Type: ttCONFIDENTIAL_MPT_HOLDER_KEY_UPDATE (93)
+ * Delegable: Delegation::NotDelegable
+ * Amendment: featureConfidentialMPTKeyRotation
+ * Privileges: Privilege::NoPriv
+ *
+ * Immutable wrapper around STTx providing type-safe field access.
+ * Use ConfidentialMPTHolderKeyUpdateBuilder to construct new transactions.
+ */
+class ConfidentialMPTHolderKeyUpdate : public TransactionBase
+{
+public:
+    static constexpr xrpl::TxType txType = ttCONFIDENTIAL_MPT_HOLDER_KEY_UPDATE;
+
+    /**
+     * @brief Construct a ConfidentialMPTHolderKeyUpdate transaction wrapper from an existing STTx object.
+     * @throws std::runtime_error if the transaction type doesn't match.
+     */
+    explicit ConfidentialMPTHolderKeyUpdate(std::shared_ptr<STTx const> tx)
+        : TransactionBase(std::move(tx))
+    {
+        // Verify transaction type
+        if (tx_->getTxnType() != txType)
+        {
+            throw std::runtime_error("Invalid transaction type for ConfidentialMPTHolderKeyUpdate");
+        }
+    }
+
+    // Transaction-specific field getters
+
+    /**
+     * @brief Get sfMPTokenIssuanceID (SoeRequired)
+     * @return The field value.
+     */
+    [[nodiscard]]
+    SF_UINT192::type::value_type
+    getMPTokenIssuanceID() const
+    {
+        return this->tx_->at(sfMPTokenIssuanceID);
+    }
+
+    /**
+     * @brief Get sfHolderEncryptionKey (SoeOptional)
+     * @return The field value, or std::nullopt if not present.
+     */
+    [[nodiscard]]
+    protocol_autogen::Optional<SF_VL::type::value_type>
+    getHolderEncryptionKey() const
+    {
+        if (hasHolderEncryptionKey())
+        {
+            return this->tx_->at(sfHolderEncryptionKey);
+        }
+        return std::nullopt;
+    }
+
+    /**
+     * @brief Check if sfHolderEncryptionKey is present.
+     * @return True if the field is present, false otherwise.
+     */
+    [[nodiscard]]
+    bool
+    hasHolderEncryptionKey() const
+    {
+        return this->tx_->isFieldPresent(sfHolderEncryptionKey);
+    }
+
+    /**
+     * @brief Get sfConfidentialBalanceSpending (SoeOptional)
+     * @return The field value, or std::nullopt if not present.
+     */
+    [[nodiscard]]
+    protocol_autogen::Optional<SF_VL::type::value_type>
+    getConfidentialBalanceSpending() const
+    {
+        if (hasConfidentialBalanceSpending())
+        {
+            return this->tx_->at(sfConfidentialBalanceSpending);
+        }
+        return std::nullopt;
+    }
+
+    /**
+     * @brief Check if sfConfidentialBalanceSpending is present.
+     * @return True if the field is present, false otherwise.
+     */
+    [[nodiscard]]
+    bool
+    hasConfidentialBalanceSpending() const
+    {
+        return this->tx_->isFieldPresent(sfConfidentialBalanceSpending);
+    }
+
+    /**
+     * @brief Get sfConfidentialBalanceInbox (SoeOptional)
+     * @return The field value, or std::nullopt if not present.
+     */
+    [[nodiscard]]
+    protocol_autogen::Optional<SF_VL::type::value_type>
+    getConfidentialBalanceInbox() const
+    {
+        if (hasConfidentialBalanceInbox())
+        {
+            return this->tx_->at(sfConfidentialBalanceInbox);
+        }
+        return std::nullopt;
+    }
+
+    /**
+     * @brief Check if sfConfidentialBalanceInbox is present.
+     * @return True if the field is present, false otherwise.
+     */
+    [[nodiscard]]
+    bool
+    hasConfidentialBalanceInbox() const
+    {
+        return this->tx_->isFieldPresent(sfConfidentialBalanceInbox);
+    }
+
+    /**
+     * @brief Get sfZKProof (SoeOptional)
+     * @return The field value, or std::nullopt if not present.
+     */
+    [[nodiscard]]
+    protocol_autogen::Optional<SF_VL::type::value_type>
+    getZKProof() const
+    {
+        if (hasZKProof())
+        {
+            return this->tx_->at(sfZKProof);
+        }
+        return std::nullopt;
+    }
+
+    /**
+     * @brief Check if sfZKProof is present.
+     * @return True if the field is present, false otherwise.
+     */
+    [[nodiscard]]
+    bool
+    hasZKProof() const
+    {
+        return this->tx_->isFieldPresent(sfZKProof);
+    }
+};
+
+/**
+ * @brief Builder for ConfidentialMPTHolderKeyUpdate transactions.
+ *
+ * Provides a fluent interface for constructing transactions with method chaining.
+ * Uses STObject internally for flexible transaction construction.
+ * Inherits common field setters from TransactionBuilderBase.
+ */
+class ConfidentialMPTHolderKeyUpdateBuilder : public TransactionBuilderBase<ConfidentialMPTHolderKeyUpdateBuilder>
+{
+public:
+    /**
+     * @brief Construct a new ConfidentialMPTHolderKeyUpdateBuilder with required fields.
+     * @param account The account initiating the transaction.
+     * @param mPTokenIssuanceID The sfMPTokenIssuanceID field value.
+     * @param sequence Optional sequence number for the transaction.
+     * @param fee Optional fee for the transaction.
+     */
+    ConfidentialMPTHolderKeyUpdateBuilder(SF_ACCOUNT::type::value_type account,
+                     std::decay_t<typename SF_UINT192::type::value_type> const& mPTokenIssuanceID,                    std::optional<SF_UINT32::type::value_type> sequence = std::nullopt,
+                    std::optional<SF_AMOUNT::type::value_type> fee = std::nullopt
+)
+        : TransactionBuilderBase<ConfidentialMPTHolderKeyUpdateBuilder>(ttCONFIDENTIAL_MPT_HOLDER_KEY_UPDATE, account, sequence, fee)
+    {
+        setMPTokenIssuanceID(mPTokenIssuanceID);
+    }
+
+    /**
+     * @brief Construct a ConfidentialMPTHolderKeyUpdateBuilder from an existing STTx object.
+     * @param tx The existing transaction to copy from.
+     * @throws std::runtime_error if the transaction type doesn't match.
+     */
+    ConfidentialMPTHolderKeyUpdateBuilder(std::shared_ptr<STTx const> tx)
+    {
+        if (tx->getTxnType() != ttCONFIDENTIAL_MPT_HOLDER_KEY_UPDATE)
+        {
+            throw std::runtime_error("Invalid transaction type for ConfidentialMPTHolderKeyUpdateBuilder");
+        }
+        object_ = *tx;
+    }
+
+    /**
+     * @brief Transaction-specific field setters
+     */
+
+    /**
+     * @brief Set sfMPTokenIssuanceID (SoeRequired)
+     * @return Reference to this builder for method chaining.
+     */
+    ConfidentialMPTHolderKeyUpdateBuilder&
+    setMPTokenIssuanceID(std::decay_t<typename SF_UINT192::type::value_type> const& value)
+    {
+        object_[sfMPTokenIssuanceID] = value;
+        return *this;
+    }
+
+    /**
+     * @brief Set sfHolderEncryptionKey (SoeOptional)
+     * @return Reference to this builder for method chaining.
+     */
+    ConfidentialMPTHolderKeyUpdateBuilder&
+    setHolderEncryptionKey(std::decay_t<typename SF_VL::type::value_type> const& value)
+    {
+        object_[sfHolderEncryptionKey] = value;
+        return *this;
+    }
+
+    /**
+     * @brief Set sfConfidentialBalanceSpending (SoeOptional)
+     * @return Reference to this builder for method chaining.
+     */
+    ConfidentialMPTHolderKeyUpdateBuilder&
+    setConfidentialBalanceSpending(std::decay_t<typename SF_VL::type::value_type> const& value)
+    {
+        object_[sfConfidentialBalanceSpending] = value;
+        return *this;
+    }
+
+    /**
+     * @brief Set sfConfidentialBalanceInbox (SoeOptional)
+     * @return Reference to this builder for method chaining.
+     */
+    ConfidentialMPTHolderKeyUpdateBuilder&
+    setConfidentialBalanceInbox(std::decay_t<typename SF_VL::type::value_type> const& value)
+    {
+        object_[sfConfidentialBalanceInbox] = value;
+        return *this;
+    }
+
+    /**
+     * @brief Set sfZKProof (SoeOptional)
+     * @return Reference to this builder for method chaining.
+     */
+    ConfidentialMPTHolderKeyUpdateBuilder&
+    setZKProof(std::decay_t<typename SF_VL::type::value_type> const& value)
+    {
+        object_[sfZKProof] = value;
+        return *this;
+    }
+
+    /**
+     * @brief Build and return the ConfidentialMPTHolderKeyUpdate wrapper.
+     * @param publicKey The public key for signing.
+     * @param secretKey The secret key for signing.
+     * @return The constructed transaction wrapper.
+     */
+    ConfidentialMPTHolderKeyUpdate
+    build(PublicKey const& publicKey, SecretKey const& secretKey)
+    {
+        sign(publicKey, secretKey);
+        return ConfidentialMPTHolderKeyUpdate{std::make_shared<STTx>(std::move(object_))};
+    }
+};
+
+}  // namespace xrpl::transactions

include/xrpl/protocol_autogen/transactions/TransactionProposalCreate.h

@@ -18,7 +18,7 @@ class TransactionProposalCreateBuilder;
 /**
  * @brief Transaction: TransactionProposalCreate
  *
- * Type: ttTRANSACTION_PROPOSAL_CREATE (93)
+ * Type: ttTRANSACTION_PROPOSAL_CREATE (95)
  * Delegable: Delegation::NotDelegable
  * Amendment: featureCosign
  * Privileges: Privilege::NoPriv

include/xrpl/tx/ApplyContext.h

@@ -51,7 +51,8 @@ public:
         beast::Journal journal = beast::Journal{beast::Journal::getNullSink()})
         : ApplyContext(registry, base, std::nullopt, tx, preclaimResult, baseFee, flags, journal)
     {
-        XRPL_ASSERT((flags & TapBatch) == 0, "Batch apply flag should not be set");
+        XRPL_ASSERT(
+            (flags & ApplyFlags::Batch) == ApplyFlags::None, "Batch apply flag should not be set");
     }
 
     std::reference_wrapper<ServiceRegistry> registry;

include/xrpl/tx/Transactor.h

@@ -59,10 +59,11 @@ public:
         , parentBatchId(parentBatchId)
         , j(j)
     {
-        XRPL_ASSERT((flags & TapBatch) == TapBatch, "Batch apply flag should be set");
+        XRPL_ASSERT(
+            (flags & ApplyFlags::Batch) == ApplyFlags::Batch, "Batch apply flag should be set");
         XRPL_ASSERT_IF(
-            (flags & TapProposal) != TapNone,
-            (flags & TapDryRun) != TapNone,
+            (flags & ApplyFlags::Proposal) != ApplyFlags::None,
+            (flags & ApplyFlags::DryRun) != ApplyFlags::None,
             "xrpl::PreflightContext : proposal preflight implies dry run");
     }
 
@@ -74,10 +75,11 @@ public:
         beast::Journal j = beast::Journal{beast::Journal::getNullSink()})
         : registry(registry), tx(tx), rules(std::move(rules)), flags(flags), j(j)
     {
-        XRPL_ASSERT((flags & TapBatch) == 0, "Batch apply flag should not be set");
+        XRPL_ASSERT(
+            (flags & ApplyFlags::Batch) == ApplyFlags::None, "Batch apply flag should not be set");
         XRPL_ASSERT_IF(
-            (flags & TapProposal) != TapNone,
-            (flags & TapDryRun) != TapNone,
+            (flags & ApplyFlags::Proposal) != ApplyFlags::None,
+            (flags & ApplyFlags::DryRun) != ApplyFlags::None,
             "xrpl::PreflightContext : proposal preflight implies dry run");
     }
 
@@ -116,7 +118,7 @@ public:
         , j(j)
     {
         XRPL_ASSERT(
-            parentBatchId.has_value() == ((flags & TapBatch) == TapBatch),
+            parentBatchId.has_value() == ((flags & ApplyFlags::Batch) == ApplyFlags::Batch),
             "Parent Batch ID should be set if batch apply flag is set");
     }
 
@@ -129,7 +131,8 @@ public:
         beast::Journal j = beast::Journal{beast::Journal::getNullSink()})
         : PreclaimContext(registry, view, preflightResult, tx, flags, std::nullopt, j)
     {
-        XRPL_ASSERT((flags & TapBatch) == 0, "Batch apply flag should not be set");
+        XRPL_ASSERT(
+            (flags & ApplyFlags::Batch) == ApplyFlags::None, "Batch apply flag should not be set");
     }
 
     PreclaimContext&

include/xrpl/tx/applySteps.h

@@ -41,7 +41,7 @@ struct ApplyResult
 inline bool
 isTecClaimHardFail(TER ter, ApplyFlags flags)
 {
-    return isTecClaim(ter) && ((flags & TapRetry) == 0u);
+    return isTecClaim(ter) && ((flags & ApplyFlags::Retry) == ApplyFlags::None);
 }
 
 /**

include/xrpl/tx/invariants/MPTInvariant.h

@@ -46,6 +46,9 @@ class ValidMPTIssuance
      * MPTokens and RippleStates deleted during apply. finalize() checks each
      * holder's AccountRoot to detect vault pseudo-account holdings deleted
      * outside VaultDelete. All these checks are gated on fixCleanup3_2_0.
+     *
+     * Under fixCleanup3_5_0, finalize() also rejects any MPToken erased with
+     * a non-zero sfMPTAmount.
      */
     std::vector<std::shared_ptr<SLE const>> deletedHoldings_;
 
@@ -138,8 +141,9 @@ public:
  * - Convert/ConvertBack symmetry:
  * Regular MPToken balance change (±X) == COA (Confidential Outstanding Amount) change (∓X)
  * - Cannot delete MPToken with non-zero confidential state:
- * Cannot delete if sfIssuerEncryptedBalance exists
- * Cannot delete if sfConfidentialBalanceInbox and sfConfidentialBalanceSpending exist
+ * Cannot delete if any of sfConfidentialBalanceSpending, sfConfidentialBalanceInbox,
+ * sfIssuerEncryptedBalance or sfAuditorEncryptedBalance is present, and the issuance's
+ * sfConfidentialOutstandingAmount is non-zero. Mirrors MPTokenAuthorize::preclaim.
  * - Privacy flag consistency:
  * MPToken confidential balance fields can only be created or changed if
  * lsfMPTCanHoldConfidentialBalance is set on the issuance.
@@ -162,6 +166,8 @@ class ValidConfidentialMPToken
         std::int64_t outstandingDelta = 0;
         SLE::const_pointer issuance;
         bool deletedWithEncrypted = false;
+        // True when an erased MPToken had a non-zero pre-tx public balance.
+        bool deletedWithBalanceBefore = false;
         bool badConsistency = false;
         bool badCOA = false;
         bool changesConfidentialFields = false;

include/xrpl/tx/transactors/token/ConfidentialMPTHolderKeyUpdate.h

@@ -0,0 +1,84 @@
+#pragma once
+
+#include <xrpl/beast/utility/Journal.h>
+#include <xrpl/core/ServiceRegistry.h>
+#include <xrpl/ledger/ReadView.h>
+#include <xrpl/protocol/STTx.h>
+#include <xrpl/protocol/TER.h>
+#include <xrpl/protocol/XRPAmount.h>
+#include <xrpl/tx/ApplyContext.h>
+#include <xrpl/tx/Transactor.h>
+
+#include <cstdint>
+
+namespace xrpl {
+
+/**
+ * @brief Allows a confidential MPT holder to rotate or recover their ElGamal
+ * encryption key, or to cancel a pending recovery.
+ *
+ * Submitted by the holder. Exactly one of three modes must be selected via
+ * the transaction flags:
+ *
+ * - Rotation (tfHolderKeyRotation): the holder still has their current
+ *   ElGamal private key. They provide a new public key along with their
+ *   current spending/inbox balances re-encrypted under that new key. The
+ *   holder's encryption key and confidential balances are updated
+ *   immediately.
+ *
+ * - Recovery (tfHolderKeyRecovery): the holder has lost their current
+ *   private key. They provide a new public key but cannot provide
+ *   re-encrypted balances. The new key is recorded as a pending
+ *   sfRecoveryKey; the confidential balances are left untouched. Completing
+ *   the recovery (rewriting the balances) is done separately by the issuer
+ *   via ConfidentialMPTRecoverBalance.
+ *
+ * - Cancel (tfCancelRecovery): the holder revokes a pending recovery
+ *   authorization created by a prior Recovery-mode transaction. No key,
+ *   balances, or proof are carried; authorization is via the holder's
+ *   ordinary XRPL signature. sfRecoveryKey is removed and everything else
+ *   is left untouched. Fails if no recovery is pending.
+ *
+ * @note Zero-knowledge proof verification for Rotation and Recovery is
+ * deferred to a follow-up once the mpt-crypto constructions are finalized.
+ */
+class ConfidentialMPTHolderKeyUpdate : public Transactor
+{
+public:
+    static constexpr auto kConsequencesFactory = ConsequencesFactoryType::Normal;
+
+    explicit ConfidentialMPTHolderKeyUpdate(ApplyContext& ctx) : Transactor(ctx)
+    {
+    }
+
+    static bool
+    checkExtraFeatures(PreflightContext const& ctx);
+
+    static std::uint32_t
+    getFlagsMask(PreflightContext const& ctx);
+
+    static NotTEC
+    preflight(PreflightContext const& ctx);
+
+    static XRPAmount
+    calculateBaseFee(ReadView const& view, STTx const& tx);
+
+    static TER
+    preclaim(PreclaimContext const& ctx);
+
+    TER
+    doApply() override;
+
+    void
+    visitInvariantEntry(bool isDelete, SLE::ConstRef before, SLE::ConstRef after) override;
+
+    [[nodiscard]] bool
+    finalizeInvariants(
+        STTx const& tx,
+        TER result,
+        XRPAmount fee,
+        ReadView const& view,
+        beast::Journal const& j) override;
+};
+
+}  // namespace xrpl

nix/check-tools/macos.txt

@@ -2,144 +2,144 @@ Detected OS: macos (Darwin arm64)
 
 Core build tools:
   ✅ cmake
-     cmake version 4.1.2
-     /nix/store/gvabsb4yqb5xsqzqph54rijnn4zpihnp-cmake-4.1.2/bin/cmake
+     cmake version 4.4.3
+     /nix/store/q85csxf4s4shx89zif097h1ql4ax1rrz-cmake-4.4.3/bin/cmake
   ✅ conan
-     Conan version 2.28.1
-     /nix/store/9jiyxmkpwmn6dcqs0765s83riw3l5ail-conan-2.28.1/bin/conan
+     Conan version 2.32.0
+     /nix/store/921jqsgbilixmr3xchj95si0jl8pi13z-conan-2.32.0/bin/conan
   ✅ git
-     git version 2.54.0
-     /nix/store/a14yxcqvv9x2l9mllgpirzhvz93pgprg-git-2.54.0/bin/git
+     git version 2.55.0
+     /nix/store/gw7c7m0dwca5lg4152x9lpmxpj171bzw-git-2.55.0/bin/git
   ✅ python3
-     Python 3.13.13
-     /nix/store/ygxqin6ydzjfawywqpp5pal8wv6sf5bh-python3-3.13.13/bin/python3.13
+     Python 3.14.7
+     /nix/store/0kcws5blwbdyxqxjd1w8hjipz61xny3k-python3-3.14.7/bin/python3.14
 
 Development tooling:
   ✅ ccache
      ccache version 4.13.6
-     /nix/store/57davyvs6p6dkrl3svzwg1ph18wsy4cz-ccache-4.13.6/bin/ccache
+     /nix/store/ydr5nlzxp1djb5256y0zzqa87vz55gsk-ccache-4.13.6/bin/ccache
   ✅ clang
-     clang version 22.1.7
-     /nix/store/192glrb2cldvziyf3378mzjqbzx3ih4g-clang-wrapper-22.1.7/bin/clang
+     clang version 22.1.8
+     /nix/store/dakcxgwz4ixkk6ps50b7vn3dvblyzsnf-clang-wrapper-22.1.8/bin/clang
   ✅ clang-22
-     clang version 22.1.7
-     /nix/store/rbap7zqq7mw00fyqa02p5rj7gqjp4w5i-clang-22/bin/clang-22
+     clang version 22.1.8
+     /nix/store/w826sqb98nnym6kzackg829664iqdlxj-clang-22/bin/clang-22
   ✅ clang++
-     clang version 22.1.7
-     /nix/store/192glrb2cldvziyf3378mzjqbzx3ih4g-clang-wrapper-22.1.7/bin/clang++
+     clang version 22.1.8
+     /nix/store/dakcxgwz4ixkk6ps50b7vn3dvblyzsnf-clang-wrapper-22.1.8/bin/clang++
   ✅ clang++-22
-     clang version 22.1.7
-     /nix/store/v9haf787f7bcz0mq1sad4bpyx21pj6li-clang++-22/bin/clang++-22
+     clang version 22.1.8
+     /nix/store/wnwyw3yfqrhpxij65bl3pa1x65q2zg3m-clang++-22/bin/clang++-22
   ✅ ClangBuildAnalyzer
      ClangBuildAnalyzer 1.6.0
-     /nix/store/4l50ds9fa2mkvh7wg8qzrlbmjs12sb8l-clangbuildanalyzer-1.6.0/bin/ClangBuildAnalyzer
+     /nix/store/c7jjnw29ra78jdlzjww2m374izhy05n8-clangbuildanalyzer-1.6.0/bin/ClangBuildAnalyzer
   ✅ curl
-     curl 8.20.0 (aarch64-apple-darwin25.3.0) libcurl/8.20.0 OpenSSL/3.6.2 zlib/1.3.2 libssh2/1.11.1 nghttp2/1.69.0 mit-krb5/1.22.1
-     /nix/store/kclq0czaxvsgh4ym9ld7b6iwy50l1snk-curl-8.20.0-bin/bin/curl
+     curl 8.22.0 (aarch64-apple-darwin25.6.0) libcurl/8.22.0 OpenSSL/3.5.8 zlib/1.3.2 libssh2/1.11.1 nghttp2/1.70.0 mit-krb5/1.22.2
+     /nix/store/pq1h17abqy6q5y6k5dn9qj0fwb89flba-curl-8.22.0-bin/bin/curl
   ✅ file
-     file-5.47
-     /nix/store/dax63li7wwcbqxxkkgzc4g2rx7d4w86x-file-5.47/bin/file
+     file-5.48
+     /nix/store/y44vpziwbzfm8020dzlqqbybyyy7lb6g-file-5.48/bin/file
   ✅ less
-     less 692 (PCRE2 regular expressions)
-     /nix/store/lvr16y75r1pdxpdv0aph5ak2yd0hkvqm-less-692/bin/less
+     less 710 (PCRE2 regular expressions)
+     /nix/store/3yn3dx5fwg5i0inqqzwnxq7f6lwhpjqa-less-710/bin/less
   ✅ make
      GNU Make 4.4.1
-     /nix/store/8wwiw8pwyhrkzyq28hqzxfl4z84lks81-gnumake-4.4.1/bin/make
+     /nix/store/8l4wgxmhdxfvc9g18y76bnxl1ghgcp7n-gnumake-4.4.1/bin/make
   ✅ netstat
      present
-     /nix/store/qsd1kzqb0ahrk433vmyl245gp623j19s-network_cmds-730.80.3/bin/netstat
+     /nix/store/57fqvgdav8lrmzndkwm7qrgksl01yj23-network_cmds-741.100.2/bin/netstat
   ✅ ninja
      1.13.2
-     /nix/store/bqykhrblarkj4fl0hz2mf8ngwfv6x6bz-ninja-1.13.2/bin/ninja
+     /nix/store/infm4vlx71q83bqz0k559w1gn4b0rq4i-ninja-1.13.2/bin/ninja
   ✅ perl
-     v5.42.0
-     /nix/store/js13ri9fvm0ajk1fpd3acigys2a9whdv-perl-5.42.0/bin/perl
+     v5.42.3
+     /nix/store/7rvr6qjfzk2ybzn1imjw6c6qq1n1a9cr-perl-5.42.3/bin/perl
   ✅ pkg-config
      0.29.2
-     /nix/store/lzrwr375jqhhbca116kja96xf1md83l8-pkg-config-wrapper-0.29.2/bin/pkg-config
+     /nix/store/nhgylvj98klqggy54h7gbc3b2ia4a00y-pkg-config-wrapper-0.29.2/bin/pkg-config
   ✅ vim
      VIM - Vi IMproved 9.2 (2026 Feb 14, compiled Jan 01 1980 00:00:00)
-     /nix/store/6vbkykg92w603c0sw3mkk7p7mfaawbns-vim-9.2.0389/bin/vim
+     /nix/store/akaa9kqm3b8rlkv61kvsqr2l2j70rvxb-vim-9.2.1001/bin/vim
   ✅ zip
      Zip 3.0
-     /nix/store/z6ph729vcakbvz3wh8ln1wk6mi06w487-zip-3.0/bin/zip
+     /nix/store/dvawr36npnad4xa6dxi2ss0fw44aa82r-zip-3.0/bin/zip
   ✅ clang-apply-replacements
-     clang-apply-replacements version 22.1.7
-     /nix/store/vzyyjf3cm1hbj9wcr2qcb66x6j98zpy7-clang-tools-22.1.7/bin/clang-apply-replacements
+     clang-apply-replacements version 22.1.8
+     /nix/store/5bij4zn161lagwyndmrr21vmxjg054nv-clang-tools-22.1.8/bin/clang-apply-replacements
   ✅ clang-apply-replacements-22
-     clang-apply-replacements version 22.1.7
-     /nix/store/m3ii69rca4077lf4wlk7m3jcag1fs577-clang-apply-replacements-22/bin/clang-apply-replacements-22
+     clang-apply-replacements version 22.1.8
+     /nix/store/w4bz034k4l0w719rrmbwnqcgyjbswy81-clang-apply-replacements-22/bin/clang-apply-replacements-22
   ✅ clang-format
-     clang-format version 22.1.7
-     /nix/store/vzyyjf3cm1hbj9wcr2qcb66x6j98zpy7-clang-tools-22.1.7/bin/clang-format
+     clang-format version 22.1.8
+     /nix/store/5bij4zn161lagwyndmrr21vmxjg054nv-clang-tools-22.1.8/bin/clang-format
   ✅ clang-format-22
-     clang-format version 22.1.7
-     /nix/store/4fawqy6ngqcsqd2ygyyzm93q0xy3f5gs-clang-format-22/bin/clang-format-22
+     clang-format version 22.1.8
+     /nix/store/w7z346l0r8y36b6lc5i7jzj3w0581l2y-clang-format-22/bin/clang-format-22
   ✅ clang-tidy
-     LLVM version 22.1.7
-     /nix/store/vzyyjf3cm1hbj9wcr2qcb66x6j98zpy7-clang-tools-22.1.7/bin/clang-tidy
+     LLVM version 22.1.8
+     /nix/store/5bij4zn161lagwyndmrr21vmxjg054nv-clang-tools-22.1.8/bin/clang-tidy
   ✅ clang-tidy-22
-     LLVM version 22.1.7
-     /nix/store/jqw4280saixaxxihwdba9ldm2fsm6dr3-clang-tidy-22/bin/clang-tidy-22
+     LLVM version 22.1.8
+     /nix/store/0lv25qd3ddgjm3ndn70q61jfr6krlkl7-clang-tidy-22/bin/clang-tidy-22
   ✅ dot
-     dot - graphviz version 12.2.1 (0)
-     /nix/store/ijb4fbnqa6wzlpqnhb6q9knqpf7qqn5z-graphviz-12.2.1/bin/dot
+     dot - graphviz version 15.1.1 (0)
+     /nix/store/mc99a6bpbk2waym2cnw6ifmxli4ndb4x-graphviz-15.1.1/bin/dot
   ✅ doxygen
-     1.16.1
-     /nix/store/kbryjdpq9jizjb0ws0nzbf2h2ymbdiwm-doxygen-1.16.1/bin/doxygen
+     1.17.0
+     /nix/store/kz43yaj0wg6fx6cbrcmi2442z1ramy0c-doxygen-1.17.0/bin/doxygen
   ✅ gcovr
      gcovr 8.4
-     /nix/store/wn8jiyh9p0bybs96s4163qp3k8vfmczx-python3.13-gcovr-8.4/bin/gcovr
+     /nix/store/czj1vxsizrbba280gg22cys40qxkqjgr-python3.14-gcovr-8.4/bin/gcovr
   ✅ gh
-     gh version 2.94.0 (nixpkgs)
-     /nix/store/fhnpw0hs0gjms1ha6ap02jq7rx13gkbp-gh-2.94.0/bin/gh
+     gh version 2.102.0 (2026-09-30)
+     /nix/store/s8bahl6zssvry93ihivfmk1l6c58byrr-gh-2.102.0/bin/gh
   ✅ git-cliff
-     git-cliff 2.13.1
-     /nix/store/cy0wwhgxa7yvrz97zydbq6sqmixc90fq-git-cliff-2.13.1/bin/git-cliff
+     git-cliff 2.14.2
+     /nix/store/k4m5yk0qb7hfslwsq1zjajz1d94j12bj-git-cliff-2.14.2/bin/git-cliff
   ✅ git-lfs
-     git-lfs/3.7.1 (3.7.1; darwin arm64; go 1.26.3)
-     /nix/store/k9r7zjfjplqa4d5s71cqvf2iv73jd9mc-git-lfs-3.7.1/bin/git-lfs
+     git-lfs/3.8.0 (3.8.0; darwin arm64; go 1.26.8)
+     /nix/store/wzixjr3yb40a13m2q654hm3bdjn6sal3-git-lfs-3.8.0/bin/git-lfs
   ✅ gpg
      gpg (GnuPG) 2.4.9
-     /nix/store/cgh6iwzz5jgx9z5whka4vgj210i6npc6-gnupg-2.4.9/bin/gpg
+     /nix/store/0ldfwnwx385i5kh7cyvxx4mkvgjhs5rh-gnupg-2.4.9/bin/gpg
   ✅ pre-commit
-     pre-commit 4.5.1
-     /nix/store/z3cca68620w0w10f090szgzdnmh1waf2-pre-commit-4.5.1/bin/pre-commit
+     pre-commit 4.6.2
+     /nix/store/ivh54xypg9qvd3ha9lis0i8p4nkf8n7a-pre-commit-4.6.2/bin/pre-commit
   ✅ run-clang-tidy
      usage: run-clang-tidy [-h] [-allow-enabling-alpha-checkers]
-     /nix/store/4x28x911z2f9y7adqlh3qspp4a16dig7-run-clang-tidy/bin/run-clang-tidy
+     /nix/store/3xss1mm3mh1hzcmg182na6ki1p5rnxf1-run-clang-tidy/bin/run-clang-tidy
   ✅ run-clang-tidy-22
      usage: run-clang-tidy [-h] [-allow-enabling-alpha-checkers]
-     /nix/store/x8iymrh76sk5q91ryg5pa7i32s6gfh34-run-clang-tidy-22/bin/run-clang-tidy-22
+     /nix/store/w68r9z07hcq4fwbfyq3yvc7qxm8aqfbl-run-clang-tidy-22/bin/run-clang-tidy-22
 
 Rust toolchain:
   ✅ cargo
      cargo 1.97.1 (c980f4866 2026-06-30)
-     /nix/store/bnfk1sl4s9angb0vj1cj9a5y5zvqinwy-rust-minimal-1.97.1/bin/cargo
+     /nix/store/gklji8yq8yrx1k039c10kwz60vqf2dxj-rust-minimal-1.97.1/bin/cargo
   ✅ cargo-audit
-     cargo-audit-audit 0.22.1
-     /nix/store/snwkga2f5gyf404h7mmp9wriwxb8v65f-cargo-audit-0.22.1/bin/cargo-audit
+     cargo-audit-audit 0.22.2
+     /nix/store/7jgrwj557l91940aj0ag4i924ima1cqn-cargo-audit-0.22.2/bin/cargo-audit
   ✅ cargo-llvm-cov
-     cargo-llvm-cov 0.8.5
-     /nix/store/fpiqdh91gwyxalqp409ynm0s0g086w7w-cargo-llvm-cov-0.8.5/bin/cargo-llvm-cov
+     cargo-llvm-cov 0.9.0
+     /nix/store/5q1h285z8zzkw2qxig9a0b1avcsk1cf0-cargo-llvm-cov-0.9.0/bin/cargo-llvm-cov
   ✅ cargo-nextest
-     cargo-nextest 0.9.137
-     /nix/store/ylz7m947mhkgsp6i7611id3s3gcd58nq-cargo-nextest-0.9.137/bin/cargo-nextest
+     cargo-nextest 0.9.146
+     /nix/store/69v3hx3k597hcxd2zy7yad7fg0aw5yxd-cargo-nextest-0.9.146/bin/cargo-nextest
   ✅ clippy-driver
      clippy 0.1.97 (8bab26f4f6 2026-07-14)
-     /nix/store/bnfk1sl4s9angb0vj1cj9a5y5zvqinwy-rust-minimal-1.97.1/bin/clippy-driver
+     /nix/store/gklji8yq8yrx1k039c10kwz60vqf2dxj-rust-minimal-1.97.1/bin/clippy-driver
   ✅ rust-analyzer
      rust-analyzer 1.97.1 (8bab26f4 2026-07-14)
-     /nix/store/j6apc5pmd0giy15da9p650r8zklslmvi-rust-analyzer-preview-1.97.1-aarch64-apple-darwin/bin/rust-analyzer
+     /nix/store/30rbyk8gx7v53fxqhs4pp0fvxfjycspr-rust-analyzer-preview-1.97.1-aarch64-apple-darwin/bin/rust-analyzer
   ✅ rust-nightly
-     rustc 1.99.0-nightly (87e5904f5 2026-07-20)
-     /nix/store/fqpjz4l0nsnji8b2pz57mnj0akbp6hcl-rust-nightly/bin/rust-nightly
+     rustc 1.101.0-nightly (282215592 2026-10-04)
+     /nix/store/a9552rf3pylcnkijc1z0hf1lcnv50djq-rust-nightly/bin/rust-nightly
   ✅ rustc
      rustc 1.97.1 (8bab26f4f 2026-07-14)
-     /nix/store/bnfk1sl4s9angb0vj1cj9a5y5zvqinwy-rust-minimal-1.97.1/bin/rustc
+     /nix/store/gklji8yq8yrx1k039c10kwz60vqf2dxj-rust-minimal-1.97.1/bin/rustc
   ✅ rustfmt
      rustfmt 1.9.0-stable (8bab26f4f6 2026-07-14)
-     /nix/store/5ymwgr9jqjz7zzbmj0j5vqbwcd3kp0vm-rustfmt-preview-1.97.1-aarch64-apple-darwin/bin/rustfmt
+     /nix/store/0jmdipyn8266j9kqx2xxm2qkxlrlrjfc-rustfmt-preview-1.97.1-aarch64-apple-darwin/bin/rustfmt
 
 Skipping git-over-HTTPS check (CHECK_TOOLS_SKIP_CLONE is set).
 

nix/ci-env.nix

@@ -21,7 +21,8 @@ let
     )
   );
 
-  toolchain = if pkgs.stdenv.isLinux then linux.toolchain else (darwin.toolchain ++ [ darwinEnv ]);
+  toolchain =
+    if pkgs.stdenv.hostPlatform.isLinux then linux.toolchain else (darwin.toolchain ++ [ darwinEnv ]);
 in
 {
   default = pkgs.buildEnv {

nix/devshell.nix

@@ -20,15 +20,16 @@ let
 
   # Custom-glibc stdenvs, matching the CI environment. darwin has no custom
   # glibc, so there they fall back to the plain nixpkgs stdenvs.
-  customGccStdenv = if pkgs.stdenv.isLinux then linux.gccStdenv else plainGccStdenv;
-  customClangStdenv = if pkgs.stdenv.isLinux then linux.clangStdenv else plainClangStdenv;
+  customGccStdenv = if pkgs.stdenv.hostPlatform.isLinux then linux.gccStdenv else plainGccStdenv;
+  customClangStdenv =
+    if pkgs.stdenv.hostPlatform.isLinux then linux.clangStdenv else plainClangStdenv;
 
   # gcov matching each gcc shell, so `-Dcoverage=ON` builds work in the shell.
   plainGcov = mkGcov {
     name = "plain";
     cc = gccPackage.cc;
   };
-  customGccGcov = if pkgs.stdenv.isLinux then linux.gcov else plainGcov;
+  customGccGcov = if pkgs.stdenv.hostPlatform.isLinux then linux.gcov else plainGcov;
 
   # Whole directory: init.sh locates the profiles relative to itself.
   conanDir = ../conan;
@@ -51,7 +52,7 @@ let
 
   # Not sdkEnv: a shell's stdenv already sets that up. Prepended so the stub
   # beats the nixpkgs libresolv this shell's tooling drags in.
-  darwinLibresolvHook = pkgs.lib.optionalString pkgs.stdenv.isDarwin (
+  darwinLibresolvHook = pkgs.lib.optionalString pkgs.stdenv.hostPlatform.isDarwin (
     pkgs.lib.concatLines (
       pkgs.lib.mapAttrsToList (
         name: value: ''export ${name}="${value} ''${${name}:-}"''
@@ -126,7 +127,7 @@ let
 in
 rec {
   # macOS: Nix Clang. Linux: Nix GCC.
-  default = if pkgs.stdenv.isDarwin then clang else gcc;
+  default = if pkgs.stdenv.hostPlatform.isDarwin then clang else gcc;
 
   # gcc/clang use the custom-glibc toolchain, matching CI. On darwin there is no
   # custom glibc, so they fall back to the plain nixpkgs toolchain.
@@ -171,7 +172,7 @@ rec {
 # The *-plain shells (stock nixpkgs toolchain) exist only on Linux: on darwin
 # gcc/clang are already plain, so these would be redundant and are omitted, which
 # makes `nix develop .#gcc-plain` fail there rather than silently aliasing gcc.
-// pkgs.lib.optionalAttrs pkgs.stdenv.isLinux {
+// pkgs.lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
   gcc-plain = makeShell {
     shellName = "gcc-plain";
     stdenv = plainGccStdenv;

src/libxrpl/basics/CountedObject.cpp

@@ -1,39 +0,0 @@
-#include <xrpl/basics/CountedObject.h>
-
-#include <algorithm>
-
-namespace xrpl {
-
-CountedObjects&
-CountedObjects::getInstance() noexcept
-{
-    static CountedObjects kInstance;
-
-    return kInstance;
-}
-
-CountedObjects::CountedObjects() noexcept : count_(0), head_(nullptr)
-{
-}
-
-CountedObjects::List
-CountedObjects::getCounts(int minimumThreshold) const
-{
-    List counts;
-
-    // When other operations are concurrent, the count
-    // might be temporarily less than the actual count.
-    counts.reserve(count_.load());
-
-    for (auto* ctr = head_.load(); ctr != nullptr; ctr = ctr->getNext())
-    {
-        if (ctr->getCount() >= minimumThreshold)
-            counts.emplace_back(ctr->getName(), ctr->getCount());
-    }
-
-    std::ranges::sort(counts);
-
-    return counts;
-}
-
-}  // namespace xrpl

src/libxrpl/basics/FileUtilities.cpp

@@ -5,6 +5,7 @@
 #include <cerrno>
 #include <cstddef>
 #include <filesystem>
+#include <format>
 #include <fstream>
 #include <iomanip>
 #include <ios>
@@ -99,12 +100,13 @@ uniqueRandomPath(
         if (ec)
         {
             Throw<std::runtime_error>(
-                "Unable to check path '" + candidate.string() + "': " + ec.message());
+                std::format("Unable to check path '{}': {}", candidate.string(), ec.message()));
         }
         if (!exists)
             return candidate;
     }
-    Throw<std::runtime_error>("Unable to generate a unique path under '" + base.string() + "'");
+    Throw<std::runtime_error>(
+        std::format("Unable to generate a unique path under '{}'", base.string()));
 }
 
 TempDir::TempDir() : path_(uniqueRandomPath(std::filesystem::temp_directory_path()))

src/libxrpl/ledger/Ledger.cpp

@@ -11,6 +11,7 @@
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/LedgerTiming.h>
 #include <xrpl/ledger/ReadView.h>
+#include <xrpl/ledger/entries/FeeSettingsEntry.h>
 #include <xrpl/nodestore/NodeObject.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/Fees.h>
@@ -560,7 +561,7 @@ Ledger::setup()
 
     try
     {
-        if (auto const sle = read(keylet::feeSettings()))
+        if (auto const sle = FeeSettingsEntryR(*this))
         {
             bool oldFees = false;
             bool newFees = false;

src/libxrpl/ledger/OpenView.cpp

@@ -16,6 +16,7 @@
 #include <boost/container/pmr/monotonic_buffer_resource.hpp>
 
 #include <cstddef>
+#include <format>
 #include <memory>
 #include <optional>
 #include <stdexcept>
@@ -264,7 +265,7 @@ OpenView::rawTxInsert(
     auto const result = txs_.emplace(
         std::piecewise_construct, std::forward_as_tuple(key), std::forward_as_tuple(txn, metaData));
     if (!result.second)
-        Throw<std::logic_error>("rawTxInsert: duplicate TX id: " + to_string(key));
+        Throw<std::logic_error>(std::format("rawTxInsert: duplicate TX id: {}", to_string(key)));
 }
 
 }  // namespace xrpl

src/libxrpl/ledger/View.cpp

@@ -9,6 +9,7 @@
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
+#include <xrpl/ledger/entries/LedgerHashesEntry.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/CredentialHelpers.h>
 #include <xrpl/ledger/helpers/DirectoryHelpers.h>
@@ -361,17 +362,16 @@ hashOfSeq(ReadView const& ledger, LedgerIndex seq, beast::Journal journal)
     if (int const diff = ledger.seq() - seq; diff <= 256)
     {
         // Within 256...
-        auto const hashIndex = ledger.read(keylet::skip());
+        LedgerHashesEntryR const hashIndex(ledger, journal);
         if (hashIndex)
         {
             XRPL_ASSERT(
                 hashIndex->getFieldU32(sfLastLedgerSequence) == (ledger.seq() - 1),
                 "xrpl::hashOfSeq : matching ledger sequence");
-            STVector256 vec = hashIndex->getFieldV256(sfHashes);
-            if (vec.size() >= diff)
-                return vec[vec.size() - diff];
+            if (auto const hash = hashIndex.hashAt(diff - 1))
+                return hash;
             JLOG(journal.warn()) << "Ledger " << ledger.seq() << " missing hash for " << seq << " ("
-                                 << vec.size() << "," << diff << ")";
+                                 << hashIndex->getFieldV256(sfHashes).size() << "," << diff << ")";
         }
         else
         {
@@ -387,16 +387,14 @@ hashOfSeq(ReadView const& ledger, LedgerIndex seq, beast::Journal journal)
     }
 
     // in skiplist
-    auto const hashIndex = ledger.read(keylet::skip(seq));
+    LedgerHashesEntryR const hashIndex(keylet::skip(seq), ledger, journal);
     if (hashIndex)
     {
         auto const lastSeq = hashIndex->getFieldU32(sfLastLedgerSequence);
         XRPL_ASSERT(lastSeq >= seq, "xrpl::hashOfSeq : minimum last ledger");
         XRPL_ASSERT((lastSeq & 0xff) == 0, "xrpl::hashOfSeq : valid last ledger");
-        auto const diff = (lastSeq - seq) >> 8;
-        STVector256 vec = hashIndex->getFieldV256(sfHashes);
-        if (vec.size() > diff)
-            return vec[vec.size() - diff - 1];
+        if (auto const hash = hashIndex.hashAt((lastSeq - seq) >> 8))
+            return hash;
     }
     JLOG(journal.warn()) << "Can't get seq " << seq << " from " << ledger.seq() << " error";
     return std::nullopt;

src/libxrpl/ledger/helpers/NFTokenHelpers.cpp

@@ -33,6 +33,7 @@
 #include <algorithm>
 #include <cstddef>
 #include <cstdint>
+#include <format>
 #include <functional>
 #include <iterator>
 #include <memory>
@@ -394,9 +395,11 @@ removeToken(ApplyView& view, AccountID const& owner, UInt256 const& nftokenID, S
 
             if (!page2)
             {
-                Throw<std::runtime_error>(
-                    "page " + to_string(page1->key()) + " has a broken " + field.getName() +
-                    " field pointing to " + to_string(*id));
+                Throw<std::runtime_error>(std::format(
+                    "page {} has a broken {} field pointing to {}",
+                    to_string(page1->key()),
+                    field.getName(),
+                    to_string(*id)));
             }
         }
 
@@ -597,7 +600,7 @@ removeTokenOffersWithLimit(ApplyView& view, Keylet const& directory, std::size_t
                 else
                 {
                     Throw<std::runtime_error>(
-                        "Offer " + to_string(offerIndexes[i]) + " cannot be deleted!");
+                        std::format("Offer {} cannot be deleted!", to_string(offerIndexes[i])));
                 }
             }
 
@@ -734,9 +737,9 @@ repairNFTokenDirectoryLinks(ApplyView& view, AccountID const& owner)
             if (!newPrev)
             {
                 // LCOV_EXCL_START
-                Throw<std::runtime_error>(
-                    "NFTokenPage directory for " + to_string(owner) +
-                    " cannot be repaired. Unexpected link problem.");
+                Throw<std::runtime_error>(std::format(
+                    "NFTokenPage directory for {} cannot be repaired. Unexpected link problem.",
+                    to_string(owner)));
                 // LCOV_EXCL_STOP
             }
             newPrev->at(sfNextPageMin) = nextPage->key();

src/libxrpl/nodestore/backend/RocksDBFactory.cpp

@@ -35,6 +35,7 @@
 #include <atomic>
 #include <cstddef>
 #include <filesystem>
+#include <format>
 #include <functional>
 #include <memory>
 #include <stdexcept>
@@ -193,7 +194,7 @@ public:
             if (!s.ok())
             {
                 Throw<std::runtime_error>(
-                    std::string("Unable to set RocksDB bbt_options: ") + s.ToString());
+                    std::format("Unable to set RocksDB bbt_options: {}", s.ToString()));
             }
         }
 
@@ -206,7 +207,7 @@ public:
             if (!s.ok())
             {
                 Throw<std::runtime_error>(
-                    std::string("Unable to set RocksDB options: ") + s.ToString());
+                    std::format("Unable to set RocksDB options: {}", s.ToString()));
             }
         }
 
@@ -241,7 +242,7 @@ public:
         if (!status.ok() || (localDb == nullptr))
         {
             Throw<std::runtime_error>(
-                std::string("Unable to open/create RocksDB: ") + status.ToString());
+                std::format("Unable to open/create RocksDB: {}", status.ToString()));
         }
         db.reset(localDb);
     }
@@ -316,8 +317,8 @@ public:
             }
             else
             {
-                status = static_cast<Status>(
-                    static_cast<int>(Status::CustomCode) + unsafeCast<int>(getStatus.code()));
+                status = checkedCast<Status>(
+                    safeCast<int>(Status::CustomCode) + safeCast<int>(getStatus.code()));
 
                 JLOG(journal.error()) << getStatus.ToString();
             }
@@ -356,7 +357,7 @@ public:
         auto ret = db->Write(options, &wb);
 
         if (!ret.ok())
-            Throw<std::runtime_error>("storeBatch failed: " + ret.ToString());
+            Throw<std::runtime_error>(std::format("storeBatch failed: {}", ret.ToString()));
     }
 
     void

src/libxrpl/protocol/AccountID.cpp

@@ -8,6 +8,8 @@
 #include <xrpl/protocol/digest.h>
 #include <xrpl/protocol/tokens.h>
 
+#include <algorithm>
+#include <array>
 #include <atomic>
 #include <cstdint>
 #include <cstring>
@@ -19,85 +21,136 @@
 
 namespace xrpl {
 
-namespace detail {
+namespace {
 
-/**
- * Caches the base58 representations of AccountIDs
+/** If true, we implement a cache for account ID lookups.
+
+    This is generally a good idea and can improve performance, especially
+    when serving client requests.
+
+    The cache may generate warnings under some sanitizers; if you want to
+    disable caching, set this variable to false.
  */
-class AccountIdCache
+constexpr bool cacheAccountIDs = true;
+
+/** Represents a cached entry for the given AccountID.
+
+    We keep the size and alignment of the structure at 64 bytes to
+    make sure it fits within a cache line and avoid false sharing.
+ */
+struct alignas(64) CachedAccountID
 {
-private:
-    struct CachedAccountID
-    {
-        AccountID id;
-        char encoding[40] = {0};
-    };
+    /** The sequence lock for the entry.
 
-    // The actual cache
-    std::vector<CachedAccountID> cache_;
+        An even value means that the data is stable, whereas an odd
+        value indicates the data is being actively modified.
 
-    // We use a hash function designed to resist algorithmic complexity attacks
-    HardenedHash<> hasher_;
+        We use a 32-bit value to ensure that the counter will never
+        return to an observed value during a read window.
+     */
+    std::atomic<std::uint32_t> seq{0};
 
-    // 64 spinlocks, packed into a single 64-bit value
-    std::atomic<std::uint64_t> locks_ = 0;
+    /** The account id. */
+    AccountID id{};
 
-public:
-    AccountIdCache(std::size_t count) : cache_(count)
-    {
-        // This is non-binding, but we try to avoid wasting memory that
-        // is caused by overallocation.
-        cache_.shrink_to_fit();
-    }
+    /** The length of the cached encoding.
 
-    std::string
-    toBase58(AccountID const& id)
-    {
-        auto const index = hasher_(id) % cache_.size();
+        This field disambiguates collisions between ACCOUNT_ZERO and
+        never-written-to slots, since they would otherwise share the
+        same encoded bits.
+     */
+    std::uint8_t len = 0;
 
-        PackedSpinlock sl(locks_, index % 64);
-
-        {
-            std::scoped_lock const lock(sl);
-
-            // The check against the first character of the encoding ensures
-            // that we don't mishandle the case of the all-zero account:
-            if (cache_[index].encoding[0] != 0 && cache_[index].id == id)
-                return cache_[index].encoding;
-        }
-
-        auto ret = encodeBase58Token(TokenType::AccountID, id.data(), id.size());
-
-        XRPL_ASSERT(ret.size() <= 38, "xrpl::detail::AccountIdCache : maximum result size");
-
-        {
-            std::scoped_lock const lock(sl);
-            cache_[index].id = id;
-            std::strcpy(cache_[index].encoding, ret.c_str());
-        }
-
-        return ret;
-    }
+    /** The actual string encoding. */
+    char encoding[39] = {0};
 };
 
-}  // namespace detail
+static_assert(sizeof(CachedAccountID) == 64 && alignof(CachedAccountID) == 64);
 
-static std::unique_ptr<detail::AccountIdCache> gAccountIdCache;
+// The actual cache to use: a simple, direct-mapped, best-effort construct.
+//
+// We do not use a hardened hash for this because an AccountID is already
+// just cryptographically generated (i.e. uniformly distributed) bits and
+// there is no amplification, since collisions do not carry an additional
+// cost.
+//
+// The size is a "nice" power of 2 because it makes the calculation of an
+// index easier.
+constinit std::array<CachedAccountID, 65536> gAccountIdCache{};
 
-void
-initAccountIdCache(std::size_t count)
-{
-    if (!gAccountIdCache && count != 0)
-        gAccountIdCache = std::make_unique<detail::AccountIdCache>(count);
-}
+}  // namespace
 
 std::string
 toBase58(AccountID const& v)
 {
-    if (gAccountIdCache)
-        return gAccountIdCache->toBase58(v);
+    // Since the input bits are generated by a cryptographically secure
+    // hash construct, we can just pick any subset of them, no muss, no
+    // fuss.
+    auto const index = [&v]() -> std::uint16_t {
+        auto const data = v.data();
 
-    return encodeBase58Token(TokenType::AccountID, v.data(), v.size());
+        return static_cast<std::uint16_t>(data[0]) | (static_cast<std::uint16_t>(data[1]) << 8);
+    }();
+
+    if constexpr (cacheAccountIDs)
+    {
+        auto& slot = gAccountIdCache[index];
+
+        // This is the optimistic, store-free read path: a collision with a
+        // concurrent writer will be detected because the seq recheck fails
+        // and we fall through to the slow path.
+        //
+        // These unsynchronized reads of the slot fields are, formally, data
+        // races and, technically speaking, result in undefined behavior and
+        // a tool like TSAN might flag them. These should not have an impact
+        // on the correctness of the returned data: the sequence lock checks
+        // ensure we discard any data that was in flux.
+        if (auto const s0 = slot.seq.load(std::memory_order::acquire);
+            (s0 & 1) == 0 && slot.len != 0 && slot.id == v)
+        {
+            char buf[38];
+            auto const len = std::min<std::size_t>(slot.len, sizeof(buf));
+            std::memcpy(buf, slot.encoding, len);
+
+            // Prevents the loads above from sinking below the recheck; the
+            // acquire on s0 constrains later operations, not earlier ones.
+            std::atomic_thread_fence(std::memory_order::acquire);
+
+            // Everything read from the slot — the gates above and the bytes in
+            // buf — precedes this recheck and is validated by it. No slot access
+            // may follow it.
+            if (slot.seq.load(std::memory_order::relaxed) == s0)
+                return std::string(buf, len);
+        }
+    }
+
+    auto ret = encodeBase58Token(TokenType::AccountID, v.data(), v.size());
+
+    XRPL_ASSERT(!ret.empty() && ret.size() <= 38, "xrpl::toBase58 : maximum result size");
+
+    if constexpr (cacheAccountIDs)
+    {
+        auto& slot = gAccountIdCache[index];
+
+        // The CAS to an odd value excludes other writers; if it fails, another
+        // thread wrote or is writing into this slot. That is not a problem: we
+        // just don't store our result into the cache this time.
+        if (auto s0 = slot.seq.load(std::memory_order::relaxed); (s0 & 1) == 0 &&
+            slot.seq.compare_exchange_strong(s0, s0 + 1, std::memory_order::acquire))
+        {
+            slot.id = v;
+            slot.len = static_cast<std::uint8_t>(ret.size());
+            std::copy_n(ret.data(), ret.size(), slot.encoding);
+
+            // The acquire on the CAS above keeps the writes from becoming visible
+            // before the seqlock transitions to an odd value, which means readers
+            // can detect an in-progress write. This release publishes them before
+            // the seqlock transitions to an even value.
+            slot.seq.store(s0 + 2, std::memory_order::release);
+        }
+    }
+
+    return ret;
 }
 
 template <>

src/libxrpl/protocol/Permissions.cpp

@@ -14,6 +14,7 @@
 
 #include <algorithm>
 #include <cstdint>
+#include <format>
 #include <functional>
 #include <limits>
 #include <optional>
@@ -105,8 +106,8 @@ Permission::Permission()
         if (type <= UINT16_MAX)
         {
             // LCOV_EXCL_START
-            Throw<std::logic_error>(
-                "Granular permission value must exceed the maximum uint16_t value: " + name);
+            Throw<std::logic_error>(std::format(
+                "Granular permission value must exceed the maximum uint16_t value: {}", name));
             // LCOV_EXCL_STOP
         }
     }

src/libxrpl/protocol/Rules.cpp

@@ -43,8 +43,9 @@ setCurrentTransactionRules(std::optional<Rules> r)
     auto const range = [&r]() {
         // If any new conditions with new amendments are added to "enableLargeNumbers", those
         // amendments must also be added to useRulesGuards.
-        bool const enableLargeNumbers =
-            !r || (r->enabled(featureSingleAssetVault) || r->enabled(featureLendingProtocol));
+        bool const enableLargeNumbers = !r ||
+            (r->enabled(featureSingleAssetVault) || r->enabled(featureLendingProtocol) ||
+             r->enabled(featureMPTokensV2));
         // If enableLargeNumbers is true, then useRulesGuards must also return true.
         // However, the reverse is not true. Other amendments can cause the rules guard to be used,
         // even though large numbers are _not_ used.
@@ -84,7 +85,8 @@ useRulesGuards(Rules const& rules)
     // with createGuards, and any other callers, and the first set of guards can be created directly
     // at the call site, without using optional.
     return rules.enabled(featureSingleAssetVault) || rules.enabled(featureLendingProtocol) ||
-        rules.enabled(fixCleanup3_2_0) || rules.enabled(fixCleanup3_3_0);
+        rules.enabled(fixCleanup3_2_0) || rules.enabled(fixCleanup3_3_0) ||
+        rules.enabled(featureMPTokensV2);
 }
 
 void

src/libxrpl/protocol/STAmount.cpp

@@ -37,6 +37,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <exception>
+#include <format>
 #include <iterator>
 #include <limits>
 #include <memory>
@@ -1193,8 +1194,7 @@ muldiv(std::uint64_t multiplier, std::uint64_t multiplicand, std::uint64_t divis
     if (ret > std::numeric_limits<std::uint64_t>::max())
     {
         Throw<std::overflow_error>(
-            "overflow: (" + std::to_string(multiplier) + " * " + std::to_string(multiplicand) +
-            ") / " + std::to_string(divisor));
+            std::format("overflow: ({} * {}) / {}", multiplier, multiplicand, divisor));
     }
 
     return static_cast<uint64_t>(ret);
@@ -1215,9 +1215,8 @@ muldivRound(
 
     if (ret > std::numeric_limits<std::uint64_t>::max())
     {
-        Throw<std::overflow_error>(
-            "overflow: ((" + std::to_string(multiplier) + " * " + std::to_string(multiplicand) +
-            ") + " + std::to_string(rounding) + ") / " + std::to_string(divisor));
+        Throw<std::overflow_error>(std::format(
+            "overflow: (({} * {}) + {}) / {}", multiplier, multiplicand, rounding, divisor));
     }
 
     return static_cast<uint64_t>(ret);

src/libxrpl/protocol/STLedgerEntry.cpp

@@ -35,9 +35,8 @@ STLedgerEntry::STLedgerEntry(Keylet const& k) : STObject(sfLedgerEntry), key_(k.
 
     if (format == nullptr)
     {
-        Throw<std::runtime_error>(
-            "Attempt to create a SLE of unknown type " +
-            std::to_string(safeCast<std::uint16_t>(k.type)));
+        Throw<std::runtime_error>(std::format(
+            "Attempt to create a SLE of unknown type {}", safeCast<std::uint16_t>(k.type)));
     }
 
     set(format->getSOTemplate());

src/libxrpl/protocol/STNumber.cpp

@@ -19,6 +19,7 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <format>
 #include <limits>
 #include <ostream>
 #include <stdexcept>
@@ -170,7 +171,7 @@ partsFromString(std::string const& number)
     boost::smatch match;
 
     if (!boost::regex_match(number, match, kReNumber))
-        Throw<std::runtime_error>("'" + number + "' is not a number");
+        Throw<std::runtime_error>(std::format("'{}' is not a number", number));
 
     // Match fields:
     //   0 = whole input

src/libxrpl/protocol/STPathSet.cpp

@@ -5,6 +5,7 @@
 #include <xrpl/basics/UnorderedContainers.h>
 #include <xrpl/basics/base_uint.h>
 #include <xrpl/basics/contract.h>
+#include <xrpl/basics/safe_cast.h>
 #include <xrpl/beast/hash/uhash.h>
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/json/json_value.h>
@@ -17,9 +18,13 @@
 #include <xrpl/protocol/jss.h>
 
 #include <algorithm>
+#include <concepts>
 #include <cstddef>
+#include <cstdint>
 #include <memory>
+#include <optional>
 #include <stdexcept>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -36,10 +41,10 @@ STPathElement::getHash(STPathElement const& element)
     //            important. We don't even really need to fully hash the whole
     //            base_uint here, as a few bytes would do for our use.
     //
-    // The note above is only true because the result of this function reaches
-    // nothing but STPathElement::operator==, where it is a fast-reject
-    // prefilter ahead of the field comparisons that decide the answer.  Do not
-    // use it to key a container.
+    // The note above is only true because the result of this function is only
+    // used by the STPathElement equality operator as a fast-reject prefilter,
+    // ahead of the field comparisons that then decide the answer. Do not use
+    // it to key a container.
 
     for (auto const x : element.getAccountID())
         hashAccount += (hashAccount * 257) ^ x;
@@ -106,12 +111,38 @@ STPathSet::operator=(STPathSet const& other)
 
 STPathSet::STPathSet(SerialIter& sit, SField const& name) : STBase(name)
 {
-    std::vector<STPathElement> path;
-    for (;;)
-    {
-        int const iType = sit.get8();
+    using enum STPathElement::Type;
 
-        if (iType == STPathElement::TypeNone || iType == STPathElement::TypeBoundary)
+    auto parsePathElementType = [](std::underlying_type_t<STPathElement::Type> byte) noexcept
+        -> std::optional<STPathElement::Type> {
+        if (byte == std::to_underlying(TypeBoundary))
+            return TypeBoundary;
+
+        constexpr auto knownBits = static_cast<std::underlying_type_t<STPathElement::Type>>(
+            std::to_underlying(TypeAccount) | std::to_underlying(TypeCurrency) |
+            std::to_underlying(TypeIssuer) | std::to_underlying(TypeMpt));
+
+        if ((byte & ~knownBits) != 0)
+            return std::nullopt;
+
+        return static_cast<STPathElement::Type>(byte);
+    };
+
+    std::vector<STPathElement> path;
+
+    std::optional<STPathElement::Type> type;
+
+    do
+    {
+        type = parsePathElementType(sit.get8());
+
+        if (!type)
+        {
+            JLOG(debugLog().error()) << "Bad path element in pathset";
+            Throw<std::runtime_error>("bad path element");
+        }
+
+        if (type == TypeNone || type == TypeBoundary)
         {
             if (path.empty())
             {
@@ -122,28 +153,11 @@ STPathSet::STPathSet(SerialIter& sit, SField const& name) : STBase(name)
             // Move rather than converting the vector to an STPath by copy.
             value_.emplace_back(std::move(path));
             path.clear();
-
-            if (iType == STPathElement::TypeNone)
-                return;
-        }
-        else if ((iType & ~STPathElement::TypeAll) != 0)
-        {
-            JLOG(debugLog().error()) << "Bad path element " << iType << " in pathset";
-            Throw<std::runtime_error>("bad path element");
         }
         else
         {
-            auto const hasAccount = (iType & STPathElement::TypeAccount) != 0u;
-            auto const hasCurrency = (iType & STPathElement::TypeCurrency) != 0u;
-            auto const hasIssuer = (iType & STPathElement::TypeIssuer) != 0u;
-            auto const hasMPT = (iType & STPathElement::TypeMpt) != 0u;
-
-            AccountID account;
-            PathAsset asset;
-            AccountID issuer;
-
-            if (hasAccount)
-                account = sit.get160();
+            bool const hasCurrency = ((*type & TypeCurrency) == TypeCurrency);
+            bool const hasMPT = ((*type & TypeMpt) == TypeMpt);
 
             if (hasCurrency && hasMPT)
             {
@@ -151,18 +165,26 @@ STPathSet::STPathSet(SerialIter& sit, SField const& name) : STBase(name)
                 Throw<std::runtime_error>("bad path element: MPT and Currency");
             }
 
+            AccountID account;
+            AccountID issuer;
+
+            if ((*type & TypeAccount) == TypeAccount)
+                account = sit.get160();
+
+            PathAsset asset;
+
             if (hasCurrency)
                 asset = Currency::fromRaw(sit.get160());
 
             if (hasMPT)
                 asset = sit.get192();
 
-            if (hasIssuer)
+            if ((*type & TypeIssuer) == TypeIssuer)
                 issuer = sit.get160();
 
             path.emplace_back(account, asset, issuer, hasCurrency || hasMPT);
         }
-    }
+    } while (type != TypeNone);
 }
 
 STBase*
@@ -216,24 +238,22 @@ STPath::getJson(JsonOptions) const
     for (auto const& it : path_)
     {
         json::Value elem(json::ValueType::Object);
-        auto const iType = it.getNodeType();
 
-        elem[jss::type] = iType;
+        elem[jss::type] = safeCast<std::uint32_t>(it.getNodeType());
 
-        if ((iType & STPathElement::TypeAccount) != 0u)
+        if (it.isType(STPathElement::TypeAccount))
             elem[jss::account] = to_string(it.getAccountID());
 
         XRPL_ASSERT(
-            ((iType & STPathElement::TypeCurrency) == 0u) ||
-                ((iType & STPathElement::TypeMpt) == 0u),
+            !(it.hasCurrency() && it.hasMPT()),
             "xrpl::STPath::getJson : not type Currency and MPT");
-        if ((iType & STPathElement::TypeCurrency) != 0u)
+        if (it.hasCurrency())
             elem[jss::currency] = to_string(it.getCurrency());
 
-        if ((iType & STPathElement::TypeMpt) != 0u)
+        if (it.hasMPT())
             elem[jss::mpt_issuance_id] = to_string(it.getMPTID());
 
-        if ((iType & STPathElement::TypeIssuer) != 0u)
+        if (it.hasIssuer())
             elem[jss::issuer] = to_string(it.getIssuerID());
 
         ret.append(elem);
@@ -265,34 +285,42 @@ STPathSet::add(Serializer& s) const
     XRPL_ASSERT(getFName().fieldType == STI_PATHSET, "xrpl::STPathSet::add : valid field type");
     bool first = true;
 
+    // Workaround, since `Serializer` does not accept strongly-typed enums
+    // yet. When support is added, the static_assert will trigger, and the
+    // lambda can be removed entirely.
+    auto const toByte = [](std::same_as<STPathElement::Type> auto t) noexcept {
+        static_assert(
+            !requires(Serializer& ser) { ser.add8(t); },
+            "Serializer::add8 now accepts STPathElement::Type directly; remove toByte.");
+        return std::to_underlying(t);
+    };
+
     for (auto const& spPath : value_)
     {
         if (!first)
-            s.add8(STPathElement::TypeBoundary);
+            s.add8(toByte(STPathElement::TypeBoundary));
 
         for (auto const& speElement : spPath)
         {
-            int const iType = speElement.getNodeType();
+            s.add8(toByte(speElement.getNodeType()));
 
-            s.add8(iType);
-
-            if ((iType & STPathElement::TypeAccount) != 0u)
+            if (speElement.isType(STPathElement::TypeAccount))
                 s.addBitString(speElement.getAccountID());
 
-            if ((iType & STPathElement::TypeMpt) != 0u)
+            if (speElement.hasMPT())
                 s.addBitString(speElement.getMPTID());
 
-            if ((iType & STPathElement::TypeCurrency) != 0u)
+            if (speElement.hasCurrency())
                 s.addBitString(speElement.getCurrency());
 
-            if ((iType & STPathElement::TypeIssuer) != 0u)
+            if (speElement.hasIssuer())
                 s.addBitString(speElement.getIssuerID());
         }
 
         first = false;
     }
 
-    s.add8(STPathElement::TypeNone);
+    s.add8(toByte(STPathElement::TypeNone));
 }
 
 }  // namespace xrpl

src/libxrpl/protocol/STTx.cpp

@@ -59,9 +59,8 @@ getTxFormat(TxType type)
 
     if (format == nullptr)
     {
-        Throw<std::runtime_error>(
-            "Invalid transaction type " +
-            std::to_string(safeCast<std::underlying_type_t<TxType>>(type)));
+        Throw<std::runtime_error>(std::format(
+            "Invalid transaction type {}", safeCast<std::underlying_type_t<TxType>>(type)));
     }
 
     return format;

src/libxrpl/protocol/STVector256.cpp

@@ -9,8 +9,8 @@
 #include <xrpl/protocol/Serializer.h>
 
 #include <cstddef>
+#include <format>
 #include <stdexcept>
-#include <string>
 #include <utility>
 
 namespace xrpl {
@@ -22,7 +22,7 @@ STVector256::STVector256(SerialIter& sit, SField const& name) : STBase(name)
     if (slice.size() % UInt256::size() != 0)
     {
         Throw<std::runtime_error>(
-            "Bad serialization for STVector256: " + std::to_string(slice.size()));
+            std::format("Bad serialization for STVector256: {}", slice.size()));
     }
 
     auto const cnt = slice.size() / UInt256::size();

src/libxrpl/protocol/STXChainBridge.cpp

@@ -70,7 +70,8 @@ STXChainBridge::STXChainBridge(SField const& name, json::Value const& v) : STBas
             std::string const name = it.memberName();
             if (!kBridgeJson.isMember(name))
             {
-                Throw<std::runtime_error>("STXChainBridge extra field detected: " + name);
+                Throw<std::runtime_error>(
+                    std::format("STXChainBridge extra field detected: {}", name));
             }
         }
         return true;

src/libxrpl/protocol/Serializer.cpp

@@ -15,8 +15,8 @@
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
+#include <format>
 #include <stdexcept>
-#include <string>
 #include <type_traits>
 
 namespace xrpl {
@@ -456,7 +456,7 @@ SerialIter::getFieldID(int& type, int& name)
         // uncommon type
         type = get8();
         if (type < 16)
-            Throw<std::runtime_error>("gFID: uncommon type out of range " + std::to_string(type));
+            Throw<std::runtime_error>(std::format("gFID: uncommon type out of range {}", type));
     }
 
     if (name == 0)
@@ -464,7 +464,7 @@ SerialIter::getFieldID(int& type, int& name)
         // uncommon name
         name = get8();
         if (name < 16)
-            Throw<std::runtime_error>("gFID: uncommon name out of range " + std::to_string(name));
+            Throw<std::runtime_error>(std::format("gFID: uncommon name out of range {}", name));
     }
 }
 

src/libxrpl/rdb/SociDB.cpp

@@ -27,6 +27,7 @@
 
 #include <soci/sqlite3/soci-sqlite3.h>  // IWYU pragma: keep
 
+#include <format>
 #include <memory>
 
 namespace xrpl {
@@ -40,8 +41,8 @@ getSociSqliteInit(std::string const& name, std::string const& dir, std::string c
 {
     if (name.empty())
     {
-        Throw<std::runtime_error>(
-            "Sqlite databases must specify a dir and a name. Name: " + name + " Dir: " + dir);
+        Throw<std::runtime_error>(std::format(
+            "Sqlite databases must specify a dir and a name. Name: {} Dir: {}", name, dir));
     }
     std::filesystem::path file(dir);
     if (std::filesystem::is_directory(file))
@@ -56,7 +57,7 @@ getSociInit(BasicConfig const& config, std::string const& dbName)
     auto const backendName = get(section, Keys::kBackend, "sqlite");
 
     if (backendName != "sqlite")
-        Throw<std::runtime_error>("Unsupported soci backend: " + backendName);
+        Throw<std::runtime_error>(std::format("Unsupported soci backend: {}", backendName));
 
     auto const path = config.legacy(Sections::kDatabasePath);
     auto const ext = dbName == "validators" || dbName == "peerfinder" ? ".sqlite" : ".db";
@@ -101,7 +102,7 @@ open(soci::session& s, std::string const& beName, std::string const& connectionS
     }
     else
     {
-        Throw<std::runtime_error>("Unsupported soci backend: " + beName);
+        Throw<std::runtime_error>(std::format("Unsupported soci backend: {}", beName));
     }
 }
 

src/libxrpl/server/Manifest.cpp

@@ -26,6 +26,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <exception>
+#include <format>
 #include <functional>
 #include <limits>
 #include <mutex>
@@ -48,7 +49,7 @@ to_string(Manifest const& m)
         return "Revocation Manifest " + mk;
 
     if (!m.signingKey)
-        Throw<std::runtime_error>("No SigningKey in manifest " + mk);
+        Throw<std::runtime_error>(std::format("No SigningKey in manifest {}", mk));
 
     return "Manifest " + mk + " (" + std::to_string(m.sequence) + ": " +
         toBase58(TokenType::NodePublic, *m.signingKey) + ")";

src/libxrpl/shamap/SHAMapNodeID.cpp

@@ -8,6 +8,7 @@
 
 #include <algorithm>
 #include <cstddef>
+#include <format>
 #include <optional>
 #include <stdexcept>
 #include <string>
@@ -107,10 +108,10 @@ SHAMapNodeID::getChildNodeID(unsigned int branch) const
         depth_ <= SHAMap::kLeafDepth, "xrpl::SHAMapNodeID::getChildNodeID : maximum leaf depth");
 
     if (depth_ >= SHAMap::kLeafDepth)
-        Throw<std::logic_error>("Request for child node ID of " + to_string(*this));
+        Throw<std::logic_error>(std::format("Request for child node ID of {}", to_string(*this)));
 
     if (!isPrefixOf(id_))
-        Throw<std::logic_error>("Incorrect mask for " + to_string(*this));
+        Throw<std::logic_error>(std::format("Incorrect mask for {}", to_string(*this)));
 
     SHAMapNodeID node{depth_ + 1, id_};
     node.id_.begin()[depth_ / 2] |= ((depth_ & 1) != 0u) ? branch : (branch << 4);

src/libxrpl/shamap/SHAMapTreeNode.cpp

@@ -18,6 +18,7 @@
 #include <xrpl/shamap/SHAMapTxPlusMetaLeafNode.h>
 
 #include <cstdint>
+#include <format>
 #include <stdexcept>
 #include <string>
 #include <type_traits>
@@ -30,9 +31,8 @@ SHAMapTreeNode::makeTransaction(Slice data, SHAMapHash const& hash, bool hashVal
 {
     if (data.size() < kMinShaMapItemBytes)
     {
-        Throw<std::runtime_error>(
-            "Short TXN node: " + std::to_string(data.size()) + " bytes (minimum " +
-            std::to_string(kMinShaMapItemBytes) + " required)");
+        Throw<std::runtime_error>(std::format(
+            "Short TXN node: {} bytes (minimum {} required)", data.size(), kMinShaMapItemBytes));
     }
 
     auto item = makeShamapitem(sha512Half(HashPrefix::TransactionId, data), data);
@@ -52,27 +52,25 @@ SHAMapTreeNode::makeTransactionWithMeta(Slice data, SHAMapHash const& hash, bool
 
     if (s.size() < tag.kBytes)
     {
-        Throw<std::runtime_error>(
-            "Short TXN+MD node: " + std::to_string(s.size()) + " bytes (minimum " +
-            std::to_string(tag.kBytes) + " required for tag)");
+        Throw<std::runtime_error>(std::format(
+            "Short TXN+MD node: {} bytes (minimum {} required for tag)", s.size(), tag.kBytes));
     }
 
     // FIXME: improve this interface so that the above check isn't needed
     if (!s.getBitString(tag, s.size() - tag.kBytes))
     {
-        Throw<std::out_of_range>(
-            "Short TXN+MD node: failed to read tag at offset " +
-            std::to_string(s.size() - tag.kBytes));
+        Throw<std::out_of_range>(std::format(
+            "Short TXN+MD node: failed to read tag at offset {}", s.size() - tag.kBytes));
     }
 
     s.chop(tag.kBytes);
 
     if (s.size() < kMinShaMapItemBytes)
     {
-        Throw<std::runtime_error>(
-            "Short TXN+MD node: " + std::to_string(s.size()) +
-            " bytes after tag removal (minimum " + std::to_string(kMinShaMapItemBytes) +
-            " required)");
+        Throw<std::runtime_error>(std::format(
+            "Short TXN+MD node: {} bytes after tag removal (minimum {} required)",
+            s.size(),
+            kMinShaMapItemBytes));
     }
 
     auto item = makeShamapitem(tag, s.slice());
@@ -92,16 +90,15 @@ SHAMapTreeNode::makeAccountState(Slice data, SHAMapHash const& hash, bool hashVa
 
     if (s.size() < tag.kBytes)
     {
-        Throw<std::runtime_error>(
-            "Short AS node: " + std::to_string(s.size()) + " bytes (minimum " +
-            std::to_string(tag.kBytes) + " required for tag)");
+        Throw<std::runtime_error>(std::format(
+            "Short AS node: {} bytes (minimum {} required for tag)", s.size(), tag.kBytes));
     }
 
     // FIXME: improve this interface so that the above check isn't needed
     if (!s.getBitString(tag, s.size() - tag.kBytes))
     {
         Throw<std::out_of_range>(
-            "Short AS node: failed to read tag at offset " + std::to_string(s.size() - tag.kBytes));
+            std::format("Short AS node: failed to read tag at offset {}", s.size() - tag.kBytes));
     }
 
     s.chop(tag.kBytes);
@@ -111,9 +108,10 @@ SHAMapTreeNode::makeAccountState(Slice data, SHAMapHash const& hash, bool hashVa
 
     if (s.size() < kMinShaMapItemBytes)
     {
-        Throw<std::runtime_error>(
-            "Short AS node: " + std::to_string(s.size()) + " bytes after tag removal (minimum " +
-            std::to_string(kMinShaMapItemBytes) + " required)");
+        Throw<std::runtime_error>(std::format(
+            "Short AS node: {} bytes after tag removal (minimum {} required)",
+            s.size(),
+            kMinShaMapItemBytes));
     }
 
     auto item = makeShamapitem(tag, s.slice());
@@ -152,7 +150,7 @@ SHAMapTreeNode::makeFromWire(Slice rawNode)
     if (type == kWireTypeTransactionWithMeta)
         return makeTransactionWithMeta(rawNode, hash, hashValid);
 
-    Throw<std::runtime_error>("wire: Unknown type (" + std::to_string(type) + ")");
+    Throw<std::runtime_error>(std::format("wire: Unknown type ({})", type));
 }
 
 SHAMapTreeNodePtr
@@ -183,9 +181,8 @@ SHAMapTreeNode::makeFromPrefix(Slice rawNode, SHAMapHash const& hash)
     if (type == HashPrefix::TxNode)
         return makeTransactionWithMeta(rawNode, hash, hashValid);
 
-    Throw<std::runtime_error>(
-        "prefix: unknown type (" +
-        std::to_string(safeCast<std::underlying_type_t<HashPrefix>>(type)) + ")");
+    Throw<std::runtime_error>(std::format(
+        "prefix: unknown type ({})", safeCast<std::underlying_type_t<HashPrefix>>(type)));
 }
 
 std::string

src/libxrpl/tx/ApplyContext.cpp

@@ -38,7 +38,7 @@ ApplyContext::ApplyContext(
     , parentBatchId_(parentBatchId)
 {
     XRPL_ASSERT(
-        parentBatchId.has_value() == ((flags_ & TapBatch) == TapBatch),
+        parentBatchId.has_value() == ((flags_ & ApplyFlags::Batch) == ApplyFlags::Batch),
         "Parent Batch ID should be set if batch apply flag is set");
     view_.emplace(&base_, flags_);
 }
@@ -53,13 +53,14 @@ std::optional<TxMeta>
 ApplyContext::apply(TER ter)
 {
     // NOLINTNEXTLINE(bugprone-unchecked-optional-access) view_ emplaced in constructor
-    return view_->apply(base_, tx, ter, parentBatchId_, (flags_ & TapDryRun) != 0u, journal);
+    return view_->apply(
+        base_, tx, ter, parentBatchId_, (flags_ & ApplyFlags::DryRun) != ApplyFlags::None, journal);
 }
 
 void
 ApplyContext::addOrderBook(Book const& book)
 {
-    if ((flags_ & TapDryRun) == TapNone)
+    if ((flags_ & ApplyFlags::DryRun) == ApplyFlags::None)
         registry.get().getOrderBookDB().addOrderBook(book);
 }
 

src/libxrpl/tx/Transactor.cpp

@@ -134,7 +134,7 @@ preflightCheckSigningKey(STObject const& sigObject, beast::Journal j)
 std::optional<NotTEC>
 preflightCheckSimulateKeys(ApplyFlags flags, STObject const& sigObject, beast::Journal j)
 {
-    if ((flags & TapDryRun) != 0u)  // simulation
+    if ((flags & ApplyFlags::DryRun) != ApplyFlags::None)  // simulation
     {
         std::optional<Slice> const signature = sigObject[~sfTxnSignature];
         if (signature && !signature->empty())
@@ -510,7 +510,8 @@ Transactor::minimumFee(
     Fees const& fees,
     ApplyFlags flags)
 {
-    return scaleFeeLoad(baseFee, registry.getFeeTrack(), fees, (flags & TapUnlimited) != 0u);
+    return scaleFeeLoad(
+        baseFee, registry.getFeeTrack(), fees, (flags & ApplyFlags::Unlimited) != ApplyFlags::None);
 }
 
 TER
@@ -521,7 +522,7 @@ Transactor::checkFee(PreclaimContext const& ctx, XRPAmount baseFee)
 
     auto const feePaid = ctx.tx[sfFee].xrp();
 
-    if ((ctx.flags & TapBatch) != 0u)
+    if ((ctx.flags & ApplyFlags::Batch) != ApplyFlags::None)
     {
         if (feePaid == beast::kZero)
             return tesSUCCESS;
@@ -951,7 +952,8 @@ Transactor::checkSign(
         return tesSUCCESS;
     }
 
-    if (((flags & TapDryRun) != 0u) && pkSigner.empty() && !sigObject.isFieldPresent(sfSigners))
+    if (((flags & ApplyFlags::DryRun) != ApplyFlags::None) && pkSigner.empty() &&
+        !sigObject.isFieldPresent(sfSigners))
     {
         // simulate: skip signature validation when neither SigningPubKey nor
         // Signers are provided
@@ -1122,7 +1124,7 @@ Transactor::checkMultiSign(
         }
 
         XRPL_ASSERT(
-            (flags & TapDryRun) || !spk.empty(),
+            (flags & ApplyFlags::DryRun) != ApplyFlags::None || !spk.empty(),
             "xrpl::Transactor::checkMultiSign : non-empty signer or "
             "simulation");
         AccountID const signingAcctIDFromPubKey =
@@ -1604,7 +1606,7 @@ Transactor::operator()()
         if (ctx_.size() > kOversizeMetaDataCap)
             result = tecOVERSIZE;
 
-        if (isTecClaim(result) && ((view().flags() & TapFailHard) != 0u))
+        if (isTecClaim(result) && ((view().flags() & ApplyFlags::FailHard) != ApplyFlags::None))
         {
             // If the TapFailHard flag is set, a tec result
             // must not do anything
@@ -1684,7 +1686,7 @@ Transactor::operator()()
     // Once we call apply, we will no longer be able to look at view()
     metadata = ctx_.apply(result);
 
-    if ((ctx_.flags() & TapDryRun) != 0u)
+    if ((ctx_.flags() & ApplyFlags::DryRun) != ApplyFlags::None)
         return logger(result, false, std::move(metadata));
 
     return logger(result, canApply, std::move(metadata));

src/libxrpl/tx/apply.cpp

@@ -215,7 +215,7 @@ applyBatchTransactions(
     auto applyOneTransaction = [&registry, &j, &parentBatchId, &batchView](STTx const& tx) {
         OpenView perTxBatchView(kBatchView, batchView);
 
-        auto const ret = apply(registry, perTxBatchView, parentBatchId, tx, TapBatch, j);
+        auto const ret = apply(registry, perTxBatchView, parentBatchId, tx, ApplyFlags::Batch, j);
         XRPL_ASSERT(
             ret.applied == (isTesSuccess(ret.ter) || isTecClaim(ret.ter)),
             "Inner transaction should not be applied");
@@ -274,7 +274,7 @@ applyTransaction(
 {
     // Returns false if the transaction has need not be retried.
     if (retryAssured)
-        flags = flags | TapRetry;
+        flags = flags | ApplyFlags::Retry;
 
     JLOG(j.debug()) << "TXN " << txn.getTransactionID() << (retryAssured ? "/retry" : "/final");
 

src/libxrpl/tx/applySteps.cpp

@@ -346,7 +346,8 @@ preflight(
     // builds; re-check the same invariant here so a release build can't
     // silently skip a proposed transaction's signature-presence checks
     // outside of a dry run.
-    if ((flags & TapProposal) != TapNone && (flags & TapDryRun) == TapNone)
+    if ((flags & ApplyFlags::Proposal) != ApplyFlags::None &&
+        (flags & ApplyFlags::DryRun) == ApplyFlags::None)
     {
         // LCOV_EXCL_START
         JLOG(j.fatal()) << "apply (preflight): TapProposal set without TapDryRun.";
@@ -377,7 +378,8 @@ preflight(
     PreflightContext const pfCtx(registry, tx, parentBatchId, rules, flags, j);
 
     // See the comment in the other preflight() overload above.
-    if ((flags & TapProposal) != TapNone && (flags & TapDryRun) == TapNone)
+    if ((flags & ApplyFlags::Proposal) != ApplyFlags::None &&
+        (flags & ApplyFlags::DryRun) == ApplyFlags::None)
     {
         // LCOV_EXCL_START
         JLOG(j.fatal()) << "apply (preflight): TapProposal set without TapDryRun.";

src/libxrpl/tx/invariants/MPTInvariant.cpp

@@ -41,6 +41,7 @@ constexpr auto kConfidentialMptTxTypes = std::to_array<TxType>({
     ttCONFIDENTIAL_MPT_MERGE_INBOX,
     ttCONFIDENTIAL_MPT_CLAWBACK,
     ttCONFIDENTIAL_MPT_MIRROR_UPDATE,
+    ttCONFIDENTIAL_MPT_HOLDER_KEY_UPDATE,
 });
 
 // Clamp to the cap (== INT64_MAX) before the signed conversion. Invariant
@@ -73,7 +74,7 @@ ValidMPTIssuance::visitEntry(bool isDelete, SLE::ConstRef before, SLE::ConstRef
     // only meaningful post-fixCleanup3_2_0 (the field is never set
     // pre-amendment, and the holding-deletion rule does not apply).
     // Skip both blocks when the amendment is off so we avoid wasted work
-    // on the hot path.
+    // on the hot path, except where noted for fixCleanup3_5_0 below.
     bool const fix320Enabled = isFeatureEnabled(fixCleanup3_2_0);
 
     if (after && after->getType() == ltMPTOKEN_ISSUANCE)
@@ -108,7 +109,10 @@ ValidMPTIssuance::visitEntry(bool isDelete, SLE::ConstRef before, SLE::ConstRef
         if (isDelete)
         {
             mptokensDeleted_++;
-            if (fix320Enabled)
+            // deletedHoldings_ also feeds finalize()'s erase-time public
+            // balance check, gated on fixCleanup3_5_0 independently of
+            // fixCleanup3_2_0.
+            if (fix320Enabled || isFeatureEnabled(fixCleanup3_5_0))
                 deletedHoldings_.push_back(after);
         }
         else if (!before)
@@ -195,6 +199,19 @@ ValidMPTIssuance::finalize(
             return false;
     }
 
+    // Deleting an MPToken with a non-zero MPTAmount is rejected.
+    if (rules.enabled(fixCleanup3_5_0))
+    {
+        for (auto const& sleHolding : deletedHoldings_)
+        {
+            if (sleHolding->getType() == ltMPTOKEN && sleHolding->getFieldU64(sfMPTAmount) > 0)
+            {
+                JLOG(j.fatal()) << "Invariant failed: MPToken deleted with non-zero balance";
+                return false;
+            }
+        }
+    }
+
     if (isTesSuccess(result) || (mptV2Enabled && result == tecINCOMPLETE))
     {
         [[maybe_unused]]
@@ -579,16 +596,27 @@ ValidConfidentialMPToken::visitEntry(
         change.mptAmountDelta =
             subtractMPTAmountDelta(change.mptAmountDelta, before->getFieldU64(sfMPTAmount));
 
-        // Cannot delete MPToken with non-zero confidential state or non-zero public amount
+        // Cannot delete MPToken with non-zero confidential state.
         if (isDelete)
         {
-            bool const hasPublicBalance = before->getFieldU64(sfMPTAmount) > 0;
-            bool const hasEncryptedFields = before->isFieldPresent(sfConfidentialBalanceSpending) ||
+            // changes_ is keyed by issuance, so sibling holders erased by the
+            // same transaction share this entry. Only ever set these flags,
+            // never clear them, or an empty sibling visited later would mask
+            // a funded MPToken.
+
+            // Retired by fixCleanup3_5_0, which moved the public balance
+            // check to ValidMPTIssuance::finalize. Kept pre-amendment for
+            // consensus safety: a non-zero public balance used to feed the
+            // confidential gate below, rejecting the erase whenever the
+            // issuance's COA was non-zero, and already-validated ledgers
+            // depend on that.
+            if (!isFeatureEnabled(fixCleanup3_5_0) && before->getFieldU64(sfMPTAmount) > 0)
+                changes_[id].deletedWithBalanceBefore = true;
+
+            if (before->isFieldPresent(sfConfidentialBalanceSpending) ||
                 before->isFieldPresent(sfConfidentialBalanceInbox) ||
                 before->isFieldPresent(sfIssuerEncryptedBalance) ||
-                before->isFieldPresent(sfAuditorEncryptedBalance);
-
-            if (hasPublicBalance || hasEncryptedFields)
+                before->isFieldPresent(sfAuditorEncryptedBalance))
                 changes_[id].deletedWithEncrypted = true;
         }
     }
@@ -694,6 +722,8 @@ ValidConfidentialMPToken::finalize(
     if (result != tesSUCCESS)
         return true;
 
+    bool const fix350Enabled = view.rules().enabled(fixCleanup3_5_0);
+
     for (auto const& [id, checks] : changes_)
     {
         // Find the MPTokenIssuance
@@ -708,8 +738,20 @@ ValidConfidentialMPToken::finalize(
         if (!issuance)
             continue;
 
-        // Cannot delete MPToken with non-zero confidential state
-        if (checks.deletedWithEncrypted)
+        // Cannot delete MPToken with non-zero confidential state.
+        //
+        // Before fixCleanup3_5_0 this gate also absorbed the pre-transaction
+        // public balance, so any drain-then-erase of an MPToken -- an
+        // AMMWithdraw of the whole pool, a LoanBrokerDelete returning cover --
+        // was rejected whenever some unrelated holder of the same issuance
+        // held a confidential balance. The COA gate itself is correct for
+        // ciphertext and mirrors MPTokenAuthorize::preclaim; only the public
+        // balance leg was misplaced.
+        bool const deletedWithEncrypted = fix350Enabled
+            ? checks.deletedWithEncrypted
+            : (checks.deletedWithEncrypted || checks.deletedWithBalanceBefore);
+
+        if (deletedWithEncrypted)
         {
             if ((*issuance)[~sfConfidentialOutstandingAmount].value_or(0) > 0)
             {
@@ -784,10 +826,10 @@ ValidConfidentialMPToken::finalize(
                 return false;
             }
 
-            // Among confidential MPT transactions, only ConfidentialMPTSend and
-            // ConfidentialMPTMergeInbox leave coaDelta unmodified. Therefore, if a confidential MPT
-            // transaction reaches here, it must be one of these two types, neither of which will
-            // modify sfOutstandingAmount
+            // Reaching here means this confidential MPT transaction left coaDelta
+            // unmodified (e.g. ConfidentialMPTSend, ConfidentialMPTMergeInbox, or
+            // ConfidentialMPTHolderKeyUpdate/ConfidentialMPTMirrorUpdate, none of which touch
+            // sfConfidentialOutstandingAmount), so it must not modify sfOutstandingAmount either.
             if (checks.outstandingDelta != 0)
             {
                 JLOG(j.fatal()) << "Invariant failed: OutstandingAmount changed "

src/libxrpl/tx/paths/BookStep.cpp

@@ -985,7 +985,7 @@ std::optional<std::variant<Quality, AMMOffer<TIn, TOut>>>
 BookStep<TIn, TOut, TDerived>::tip(ReadView const& view) const
 {
     // This can be simplified (and sped up) if directories are never empty.
-    Sandbox sb(&view, TapNone);
+    Sandbox sb(&view, ApplyFlags::None);
     BookTip bt(sb, book_);
     auto const lobQuality = bt.step(j_) ? std::optional<Quality>(bt.quality()) : std::nullopt;
     // Multi-path offer generates an offer with the quality

src/libxrpl/tx/paths/PaySteps.cpp

@@ -57,10 +57,8 @@ checkNear(IOUAmount const& expected, IOUAmount const& actual)
 static bool
 isXRPAccount(STPathElement const& pe)
 {
-    if (pe.getNodeType() != STPathElement::TypeAccount)
-        return false;
-    return isXRP(pe.getAccountID());
-};
+    return pe.getNodeType() == STPathElement::TypeAccount && isXRP(pe.getAccountID());
+}
 
 static std::pair<TER, std::unique_ptr<Step>>
 toStep(
@@ -71,11 +69,8 @@ toStep(
 {
     auto& j = ctx.j;
 
-    if (ctx.isFirst && e1->isAccount() &&
-        ((e1->getNodeType() & STPathElement::TypeCurrency) != 0u) && e1->getPathAsset().isXRP())
-    {
+    if (ctx.isFirst && e1->isAccount() && e1->hasCurrency() && e1->getPathAsset().isXRP())
         return makeXrpEndpointStep(ctx, e1->getAccountID());
-    }
 
     if (ctx.isLast && isXRPAccount(*e1) && e2->isAccount())
         return makeXrpEndpointStep(ctx, e2->getAccountID());
@@ -117,15 +112,9 @@ toStep(
         // LCOV_EXCL_STOP
     }
 
-    XRPL_ASSERT(
-        (e2->getNodeType() & STPathElement::TypeAsset) ||
-            (e2->getNodeType() & STPathElement::TypeIssuer),
-        "xrpl::toStep : currency or issuer");
-    PathAsset const outAsset =
-        ((e2->getNodeType() & STPathElement::TypeAsset) != 0u) ? e2->getPathAsset() : curAsset;
-    auto const outIssuer = ((e2->getNodeType() & STPathElement::TypeIssuer) != 0u)
-        ? e2->getIssuerID()
-        : curAsset.getIssuer();
+    XRPL_ASSERT(e2->hasAsset() || e2->hasIssuer(), "xrpl::toStep : currency or issuer");
+    PathAsset const outAsset = e2->hasAsset() ? e2->getPathAsset() : curAsset;
+    auto const outIssuer = e2->hasIssuer() ? e2->getIssuerID() : curAsset.getIssuer();
 
     if (isXRP(curAsset) && outAsset.isXRP())
     {
@@ -197,16 +186,15 @@ toStrand(
     for (std::size_t i = 0; i < path.size(); ++i)
     {
         auto const& pe = path[i];
-        auto const t = pe.getNodeType();
 
-        if (((t & ~STPathElement::TypeAll) != 0u) || (t == 0u))
+        if ((pe.getNodeType() & ~STPathElement::TypeAll) != STPathElement::TypeNone || pe.isNone())
             return {temBAD_PATH, Strand{}};
 
-        bool const hasAccount = (t & STPathElement::TypeAccount) != 0u;
-        bool const hasIssuer = (t & STPathElement::TypeIssuer) != 0u;
-        bool const hasCurrency = (t & STPathElement::TypeCurrency) != 0u;
-        bool const hasMPT = (t & STPathElement::TypeMpt) != 0u;
-        bool const hasAsset = (t & STPathElement::TypeAsset) != 0u;
+        bool const hasAccount = pe.isType(STPathElement::TypeAccount);
+        bool const hasIssuer = pe.hasIssuer();
+        bool const hasCurrency = pe.hasCurrency();
+        bool const hasMPT = pe.hasMPT();
+        bool const hasAsset = pe.hasAsset();
 
         if (hasAccount && (hasIssuer || hasCurrency))
             return {temBAD_PATH, Strand{}};
@@ -250,9 +238,7 @@ toStrand(
     }();
 
     // Currency or MPT
-    auto hasAsset = [](STPathElement const pe) {
-        return pe.getNodeType() & STPathElement::TypeAsset;
-    };
+    auto hasAsset = [](STPathElement const& pe) { return pe.hasAsset(); };
 
     std::vector<STPathElement> normPath;
     // reserve enough for the path, the implied source, destination,

src/libxrpl/tx/transactors/account/AccountSet.cpp

@@ -187,7 +187,8 @@ AccountSet::preclaim(PreclaimContext const& ctx)
         if (!dirIsEmpty(ctx.view, keylet::ownerDir(id)))
         {
             JLOG(ctx.j.trace()) << "Retry: Owner directory not empty.";
-            return ((ctx.flags & TapRetry) != 0u) ? TER{terOWNERS} : TER{tecOWNERS};
+            return ((ctx.flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terOWNERS}
+                                                                         : TER{tecOWNERS};
         }
     }
 

src/libxrpl/tx/transactors/dex/OfferCreate.cpp

@@ -295,7 +295,8 @@ OfferCreate::checkAcceptAsset(
         JLOG(j.debug()) << "delay: can't receive IOUs from non-existent issuer: "
                         << to_string(asset.getIssuer());
 
-        return ((flags & TapRetry) != 0u) ? TER{terNO_ACCOUNT} : TER{tecNO_ISSUER};
+        return ((flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terNO_ACCOUNT}
+                                                                 : TER{tecNO_ISSUER};
     }
 
     // An account cannot create a trustline to itself, so no line can exist
@@ -318,7 +319,8 @@ OfferCreate::checkAcceptAsset(
                 {
                     JLOG(j.debug()) << "delay: can't receive IOUs from issuer with "
                                        "DisallowIncomingTrustline set";
-                    return ((flags & TapRetry) != 0u) ? TER{terNO_LINE} : TER{tecNO_LINE};
+                    return ((flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terNO_LINE}
+                                                                             : TER{tecNO_LINE};
                 }
             }
 
@@ -326,7 +328,8 @@ OfferCreate::checkAcceptAsset(
             {
                 if (!trustLine)
                 {
-                    return ((flags & TapRetry) != 0u) ? TER{terNO_LINE} : TER{tecNO_LINE};
+                    return ((flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terNO_LINE}
+                                                                             : TER{tecNO_LINE};
                 }
 
                 // Entries have a canonical representation, determined by a
@@ -342,7 +345,8 @@ OfferCreate::checkAcceptAsset(
                     JLOG(j.debug()) << "delay: can't receive IOUs from "
                                        "issuer without auth.";
 
-                    return ((flags & TapRetry) != 0u) ? TER{terNO_AUTH} : TER{tecNO_AUTH};
+                    return ((flags & ApplyFlags::Retry) != ApplyFlags::None) ? TER{terNO_AUTH}
+                                                                             : TER{tecNO_AUTH};
                 }
             }
 

src/libxrpl/tx/transactors/escrow/EscrowCancel.cpp

@@ -3,6 +3,7 @@
 #include <xrpl/basics/Log.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/View.h>
+#include <xrpl/ledger/entries/EscrowEntry.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/EscrowHelpers.h>
 #include <xrpl/ledger/helpers/MPTokenHelpers.h>
@@ -94,13 +95,12 @@ EscrowCancel::preclaim(PreclaimContext const& ctx)
     if (ctx.view.rules().enabled(featureTokenEscrow))
     {
         auto const seqProxy = SeqProxy::rawSequence(ctx.tx[sfOfferSequence]);
-        auto const k = keylet::escrow(ctx.tx[sfOwner], seqProxy);
-        auto const slep = ctx.view.read(k);
-        if (!slep)
+        EscrowEntryR const escrow(ctx.tx[sfOwner], seqProxy, ctx.view);
+        if (!escrow)
             return tecNO_TARGET;
 
-        AccountID const account = (*slep)[sfAccount];
-        STAmount const amount = (*slep)[sfAmount];
+        AccountID const account = (*escrow)[sfAccount];
+        STAmount const amount = (*escrow)[sfAmount];
 
         if (!isXRP(amount))
         {
@@ -120,9 +120,8 @@ TER
 EscrowCancel::doApply()
 {
     auto const seqProxy = SeqProxy::rawSequence(ctx_.tx[sfOfferSequence]);
-    auto const k = keylet::escrow(ctx_.tx[sfOwner], seqProxy);
-    auto const slep = ctx_.view().peek(k);
-    if (!slep)
+    EscrowEntryW escrow(ctx_.tx[sfOwner], seqProxy, ctx_.view(), j_);
+    if (!escrow)
     {
         if (ctx_.view().rules().enabled(featureTokenEscrow))
             return tecINTERNAL;  // LCOV_EXCL_LINE
@@ -133,19 +132,19 @@ EscrowCancel::doApply()
     auto const now = ctx_.view().header().parentCloseTime;
 
     // No cancel time specified: can't execute at all.
-    if (!(*slep)[~sfCancelAfter])
+    if (!(*escrow)[~sfCancelAfter])
         return tecNO_PERMISSION;
 
     // Too soon: can't execute before the cancel time.
-    if (!after(now, (*slep)[sfCancelAfter]))
+    if (!after(now, (*escrow)[sfCancelAfter]))
         return tecNO_PERMISSION;
 
-    AccountID const account = (*slep)[sfAccount];
+    AccountID const account = (*escrow)[sfAccount];
 
     // Remove escrow from owner directory
     {
-        auto const page = (*slep)[sfOwnerNode];
-        if (!ctx_.view().dirRemove(keylet::ownerDir(account), page, k.key, true))
+        auto const page = (*escrow)[sfOwnerNode];
+        if (!ctx_.view().dirRemove(keylet::ownerDir(account), page, escrow.key(), true))
         {
             // LCOV_EXCL_START
             JLOG(j_.fatal()) << "Unable to delete Escrow from owner.";
@@ -155,9 +154,10 @@ EscrowCancel::doApply()
     }
 
     // Remove escrow from recipient's owner directory, if present.
-    if (auto const optPage = (*slep)[~sfDestinationNode]; optPage)
+    if (auto const optPage = (*escrow)[~sfDestinationNode]; optPage)
     {
-        if (!ctx_.view().dirRemove(keylet::ownerDir((*slep)[sfDestination]), *optPage, k.key, true))
+        if (!ctx_.view().dirRemove(
+                keylet::ownerDir((*escrow)[sfDestination]), *optPage, escrow.key(), true))
         {
             // LCOV_EXCL_START
             JLOG(j_.fatal()) << "Unable to delete Escrow from recipient.";
@@ -167,13 +167,13 @@ EscrowCancel::doApply()
     }
 
     auto const sle = ctx_.view().peek(keylet::account(account));
-    STAmount const amount = slep->getFieldAmount(sfAmount);
+    STAmount const amount = escrow->getFieldAmount(sfAmount);
 
     // The return can re-create a holding the owner deleted while the escrow
     // was pending; the removed escrow must not be counted against its reserve.
     bool const recycleReserve = ctx_.view().rules().enabled(fixCleanup3_4_0);
     if (recycleReserve)
-        decreaseOwnerCountForObject(ctx_.view(), sle, slep, 1, ctx_.journal);
+        decreaseOwnerCountForObject(ctx_.view(), sle, escrow.mutableRawSle(), 1, ctx_.journal);
 
     // Transfer amount back to the owner
     if (isXRP(amount))
@@ -192,7 +192,7 @@ EscrowCancel::doApply()
                     return escrowUnlockApplyHelper<T>(
                         ctx_.getApplyViewContext(),
                         kParityRate,
-                        ctx_.view().rules().enabled(fixCleanup3_2_0) ? sle : slep,
+                        ctx_.view().rules().enabled(fixCleanup3_2_0) ? sle : escrow.mutableRawSle(),
                         preFeeBalance_,
                         amount,
                         issuer,
@@ -206,9 +206,9 @@ EscrowCancel::doApply()
             return ret;  // LCOV_EXCL_LINE
 
         // Remove escrow from issuers owner directory, if present.
-        if (auto const optPage = (*slep)[~sfIssuerNode]; optPage)
+        if (auto const optPage = (*escrow)[~sfIssuerNode]; optPage)
         {
-            if (!ctx_.view().dirRemove(keylet::ownerDir(issuer), *optPage, k.key, true))
+            if (!ctx_.view().dirRemove(keylet::ownerDir(issuer), *optPage, escrow.key(), true))
             {
                 // LCOV_EXCL_START
                 JLOG(j_.fatal()) << "Unable to delete Escrow from recipient.";
@@ -219,10 +219,10 @@ EscrowCancel::doApply()
     }
 
     if (!recycleReserve)
-        decreaseOwnerCountForObject(ctx_.view(), sle, slep, 1, ctx_.journal);
+        decreaseOwnerCountForObject(ctx_.view(), sle, escrow.mutableRawSle(), 1, ctx_.journal);
 
     // Remove escrow from ledger
-    ctx_.view().erase(slep);
+    escrow.erase();
 
     return tesSUCCESS;
 }

src/libxrpl/tx/transactors/escrow/EscrowCreate.cpp

@@ -7,6 +7,7 @@
 #include <xrpl/core/ServiceRegistry.h>
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/View.h>
+#include <xrpl/ledger/entries/EscrowEntry.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/DirectoryHelpers.h>
 #include <xrpl/ledger/helpers/MPTokenHelpers.h>
@@ -481,30 +482,31 @@ EscrowCreate::doApply()
 
     // Create escrow in ledger.  Note that we use the value from the
     // sequence or ticket.  For more explanation see comments in SeqProxy.h.
-    Keylet const escrowKeylet = keylet::escrow(accountID_, ctx_.tx.getSeqProxy());
-    auto const slep = std::make_shared<SLE>(escrowKeylet);
-    (*slep)[sfAmount] = amount;
-    (*slep)[sfAccount] = accountID_;
-    (*slep)[~sfCondition] = ctx_.tx[~sfCondition];
-    (*slep)[~sfSourceTag] = ctx_.tx[~sfSourceTag];
-    (*slep)[sfDestination] = ctx_.tx[sfDestination];
-    (*slep)[~sfCancelAfter] = ctx_.tx[~sfCancelAfter];
-    (*slep)[~sfFinishAfter] = ctx_.tx[~sfFinishAfter];
-    (*slep)[~sfDestinationTag] = ctx_.tx[~sfDestinationTag];
+    EscrowEntryW escrow(accountID_, ctx_.tx.getSeqProxy(), ctx_.view(), j_);
+    Keylet const escrowKeylet = escrow.keylet();
+    escrow.newSLE();
+    (*escrow)[sfAmount] = amount;
+    (*escrow)[sfAccount] = accountID_;
+    (*escrow)[~sfCondition] = ctx_.tx[~sfCondition];
+    (*escrow)[~sfSourceTag] = ctx_.tx[~sfSourceTag];
+    (*escrow)[sfDestination] = ctx_.tx[sfDestination];
+    (*escrow)[~sfCancelAfter] = ctx_.tx[~sfCancelAfter];
+    (*escrow)[~sfFinishAfter] = ctx_.tx[~sfFinishAfter];
+    (*escrow)[~sfDestinationTag] = ctx_.tx[~sfDestinationTag];
 
     if (ctx_.view().rules().enabled(fixIncludeKeyletFields))
     {
-        (*slep)[sfSequence] = ctx_.tx.getSeqProxy().value();
+        (*escrow)[sfSequence] = ctx_.tx.getSeqProxy().value();
     }
 
     if (ctx_.view().rules().enabled(featureTokenEscrow) && !isXRP(amount))
     {
         auto const xferRate = transferRate(ctx_.view(), amount);
         if (xferRate != kParityRate)
-            (*slep)[sfTransferRate] = xferRate.value;
+            (*escrow)[sfTransferRate] = xferRate.value;
     }
 
-    ctx_.view().insert(slep);
+    escrow.insert();
 
     // Add escrow to sender's owner directory
     {
@@ -512,7 +514,7 @@ EscrowCreate::doApply()
             keylet::ownerDir(accountID_), escrowKeylet, describeOwnerDir(accountID_));
         if (!page)
             return tecDIR_FULL;  // LCOV_EXCL_LINE
-        (*slep)[sfOwnerNode] = *page;
+        (*escrow)[sfOwnerNode] = *page;
     }
 
     // If it's not a self-send, add escrow to recipient's owner directory.
@@ -523,7 +525,7 @@ EscrowCreate::doApply()
             ctx_.view().dirInsert(keylet::ownerDir(dest), escrowKeylet, describeOwnerDir(dest));
         if (!page)
             return tecDIR_FULL;  // LCOV_EXCL_LINE
-        (*slep)[sfDestinationNode] = *page;
+        (*escrow)[sfDestinationNode] = *page;
     }
 
     // IOU escrow objects are added to the issuer's owner directory to help
@@ -536,7 +538,7 @@ EscrowCreate::doApply()
             ctx_.view().dirInsert(keylet::ownerDir(issuer), escrowKeylet, describeOwnerDir(issuer));
         if (!page)
             return tecDIR_FULL;  // LCOV_EXCL_LINE
-        (*slep)[sfIssuerNode] = *page;
+        (*escrow)[sfIssuerNode] = *page;
     }
 
     // Deduct owner's balance
@@ -559,7 +561,7 @@ EscrowCreate::doApply()
 
     // increment owner count
     increaseOwnerCount(ctx_.getApplyViewContext(), sle, 1, ctx_.journal);
-    addSponsorToLedgerEntry(ctx_.getApplyViewContext(), slep);
+    addSponsorToLedgerEntry(ctx_.getApplyViewContext(), escrow.mutableRawSle());
     ctx_.view().update(sle);
     return tesSUCCESS;
 }

src/libxrpl/tx/transactors/escrow/EscrowFinish.cpp

@@ -9,6 +9,7 @@
 #include <xrpl/ledger/ApplyView.h>
 #include <xrpl/ledger/ReadView.h>
 #include <xrpl/ledger/View.h>
+#include <xrpl/ledger/entries/EscrowEntry.h>
 #include <xrpl/ledger/helpers/AccountRootHelpers.h>
 #include <xrpl/ledger/helpers/CredentialHelpers.h>
 #include <xrpl/ledger/helpers/EscrowHelpers.h>
@@ -211,13 +212,12 @@ EscrowFinish::preclaim(PreclaimContext const& ctx)
     if (ctx.view.rules().enabled(featureTokenEscrow))
     {
         auto const seqProxy = SeqProxy::rawSequence(ctx.tx[sfOfferSequence]);
-        auto const k = keylet::escrow(ctx.tx[sfOwner], seqProxy);
-        auto const slep = ctx.view.read(k);
-        if (!slep)
+        EscrowEntryR const escrow(ctx.tx[sfOwner], seqProxy, ctx.view);
+        if (!escrow)
             return tecNO_TARGET;
 
-        AccountID const dest = (*slep)[sfDestination];
-        STAmount const amount = (*slep)[sfAmount];
+        AccountID const dest = (*escrow)[sfDestination];
+        STAmount const amount = (*escrow)[sfAmount];
 
         if (!isXRP(amount))
         {
@@ -237,9 +237,8 @@ TER
 EscrowFinish::doApply()
 {
     auto const seqProxy = SeqProxy::rawSequence(ctx_.tx[sfOfferSequence]);
-    auto const k = keylet::escrow(ctx_.tx[sfOwner], seqProxy);
-    auto const slep = ctx_.view().peek(k);
-    if (!slep)
+    EscrowEntryW escrow(ctx_.tx[sfOwner], seqProxy, ctx_.view(), j_);
+    if (!escrow)
     {
         if (ctx_.view().rules().enabled(featureTokenEscrow))
             return tecINTERNAL;  // LCOV_EXCL_LINE
@@ -252,11 +251,11 @@ EscrowFinish::doApply()
     auto const now = ctx_.view().header().parentCloseTime;
 
     // Too soon: can't execute before the finish time
-    if ((*slep)[~sfFinishAfter] && !after(now, (*slep)[sfFinishAfter]))
+    if ((*escrow)[~sfFinishAfter] && !after(now, (*escrow)[sfFinishAfter]))
         return tecNO_PERMISSION;
 
     // Too late: can't execute after the cancel time
-    if ((*slep)[~sfCancelAfter] && after(now, (*slep)[sfCancelAfter]))
+    if ((*escrow)[~sfCancelAfter] && after(now, (*escrow)[sfCancelAfter]))
         return tecNO_PERMISSION;
 
     // Check cryptocondition fulfillment
@@ -296,7 +295,7 @@ EscrowFinish::doApply()
             return tecCRYPTOCONDITION_ERROR;
 
         // Check against condition in the ledger entry:
-        auto const cond = (*slep)[~sfCondition];
+        auto const cond = (*escrow)[~sfCondition];
 
         // If a condition wasn't specified during creation,
         // one shouldn't be included now.
@@ -313,7 +312,7 @@ EscrowFinish::doApply()
     }
 
     // NOTE: Escrow payments cannot be used to fund accounts.
-    AccountID const destID = (*slep)[sfDestination];
+    AccountID const destID = (*escrow)[sfDestination];
     auto const sled = ctx_.view().peek(keylet::account(destID));
     if (!sled)
         return tecNO_DST;
@@ -323,12 +322,12 @@ EscrowFinish::doApply()
         !isTesSuccess(err))
         return err;
 
-    AccountID const account = (*slep)[sfAccount];
+    AccountID const account = (*escrow)[sfAccount];
 
     // Remove escrow from owner directory
     {
-        auto const page = (*slep)[sfOwnerNode];
-        if (!ctx_.view().dirRemove(keylet::ownerDir(account), page, k.key, true))
+        auto const page = (*escrow)[sfOwnerNode];
+        if (!ctx_.view().dirRemove(keylet::ownerDir(account), page, escrow.key(), true))
         {
             // LCOV_EXCL_START
             JLOG(j_.fatal()) << "Unable to delete Escrow from owner.";
@@ -338,9 +337,9 @@ EscrowFinish::doApply()
     }
 
     // Remove escrow from recipient's owner directory, if present.
-    if (auto const optPage = (*slep)[~sfDestinationNode])
+    if (auto const optPage = (*escrow)[~sfDestinationNode])
     {
-        if (!ctx_.view().dirRemove(keylet::ownerDir(destID), *optPage, k.key, true))
+        if (!ctx_.view().dirRemove(keylet::ownerDir(destID), *optPage, escrow.key(), true))
         {
             // LCOV_EXCL_START
             JLOG(j_.fatal()) << "Unable to delete Escrow from recipient.";
@@ -355,9 +354,9 @@ EscrowFinish::doApply()
     bool const recycleReserve =
         ctx_.view().rules().enabled(featureSponsor) || ctx_.view().rules().enabled(fixCleanup3_4_0);
     if (recycleReserve)
-        decreaseOwnerCountForObject(ctx_.view(), account, slep, 1, ctx_.journal);
+        decreaseOwnerCountForObject(ctx_.view(), account, escrow.mutableRawSle(), 1, ctx_.journal);
 
-    STAmount const amount = slep->getFieldAmount(sfAmount);
+    STAmount const amount = escrow->getFieldAmount(sfAmount);
     // Transfer amount to destination
     if (isXRP(amount))
     {
@@ -368,8 +367,8 @@ EscrowFinish::doApply()
         if (!ctx_.view().rules().enabled(featureTokenEscrow))
             return temDISABLED;  // LCOV_EXCL_LINE
 
-        Rate lockedRate = slep->isFieldPresent(sfTransferRate)
-            ? xrpl::Rate(slep->getFieldU32(sfTransferRate))
+        Rate lockedRate = escrow->isFieldPresent(sfTransferRate)
+            ? xrpl::Rate(escrow->getFieldU32(sfTransferRate))
             : kParityRate;
         auto const issuer = amount.getIssuer();
         bool const createAsset = destID == accountID_;
@@ -392,9 +391,9 @@ EscrowFinish::doApply()
             return ret;
 
         // Remove escrow from issuers owner directory, if present.
-        if (auto const optPage = (*slep)[~sfIssuerNode]; optPage)
+        if (auto const optPage = (*escrow)[~sfIssuerNode]; optPage)
         {
-            if (!ctx_.view().dirRemove(keylet::ownerDir(issuer), *optPage, k.key, true))
+            if (!ctx_.view().dirRemove(keylet::ownerDir(issuer), *optPage, escrow.key(), true))
             {
                 // LCOV_EXCL_START
                 JLOG(j_.fatal()) << "Unable to delete Escrow from recipient.";
@@ -407,10 +406,10 @@ EscrowFinish::doApply()
     ctx_.view().update(sled);
 
     if (!recycleReserve)
-        decreaseOwnerCountForObject(ctx_.view(), account, slep, 1, ctx_.journal);
+        decreaseOwnerCountForObject(ctx_.view(), account, escrow.mutableRawSle(), 1, ctx_.journal);
 
     // Remove escrow from ledger
-    ctx_.view().erase(slep);
+    escrow.erase();
     return tesSUCCESS;
 }
 

src/libxrpl/tx/transactors/lending/LoanSet.cpp

@@ -91,7 +91,8 @@ LoanSet::preflight(PreflightContext const& ctx)
     // A proposed LoanSet is stored unsigned; its CounterpartySignature is
     // collected on-ledger afterward, so its absence here is expected, not an
     // error (On-Chain Cosigner spec §5.3.1.2).
-    if (!tx.isFlag(tfInnerBatchTxn) && !counterPartySig && (ctx.flags & TapProposal) == 0)
+    if (!tx.isFlag(tfInnerBatchTxn) && !counterPartySig &&
+        (ctx.flags & ApplyFlags::Proposal) == ApplyFlags::None)
     {
         JLOG(ctx.j.warn()) << "LoanSet transaction must have a CounterpartySignature.";
         return temBAD_SIGNER;

src/libxrpl/tx/transactors/proposal/TransactionProposalCreate.cpp

@@ -54,8 +54,8 @@ TransactionProposalCreate::preflight(PreflightContext const& ctx)
     try
     {
         STTx const stx{STObject{proposedTx}};
-        auto const inner =
-            xrpl::preflight(ctx.registry, ctx.rules, stx, TapDryRun | TapProposal, ctx.j);
+        auto const inner = xrpl::preflight(
+            ctx.registry, ctx.rules, stx, ApplyFlags::DryRun | ApplyFlags::Proposal, ctx.j);
         if (!isTesSuccess(inner.ter))
         {
             JLOG(ctx.j.debug()) << "TransactionProposalCreate: proposed txn "

src/libxrpl/tx/transactors/sponsor/SponsorshipTransfer.cpp

@@ -205,7 +205,7 @@ SponsorshipTransfer::preflight(PreflightContext const& ctx)
     // is collected on-ledger afterward, so its absence here is expected, not
     // an error (On-Chain Cosigner spec §5.3.1.2).
     if (isAccountReserveSponsorship && !ctx.tx.isFieldPresent(sfSponsorSignature) &&
-        (ctx.flags & TapProposal) == 0)
+        (ctx.flags & ApplyFlags::Proposal) == ApplyFlags::None)
     {
         JLOG(ctx.j.debug()) << "preflight: account sponsorship requires sfSponsorSignature";
         return temMALFORMED;

src/libxrpl/tx/transactors/system/Batch.cpp

@@ -359,7 +359,8 @@ Batch::preflight(PreflightContext const& ctx)
         // TapBatch — PreflightContext with a parentBatchId requires it.
         // LoanSet already short-circuits on tfInnerBatchTxn; it is also in
         // kDisabledTxTypes, so it never reaches this call.
-        ApplyFlags const innerFlags = TapBatch | (ctx.flags & (TapProposal | TapDryRun));
+        ApplyFlags const innerFlags =
+            ApplyFlags::Batch | (ctx.flags & (ApplyFlags::Proposal | ApplyFlags::DryRun));
         if (auto const preflightResult =
                 xrpl::preflight(ctx.registry, ctx.rules, parentBatchId, stx, innerFlags, ctx.j);
             !isTesSuccess(preflightResult.ter))
@@ -431,7 +432,7 @@ Batch::preflightSigValidated(PreflightContext const& ctx)
     // A proposed Batch is stored unsigned; its BatchSigners are collected
     // on-ledger afterward, so the signer-presence match belongs to submission
     // time, not proposal creation (On-Chain Cosigner spec §5.3.1.2).
-    if ((ctx.flags & TapProposal) != 0)
+    if ((ctx.flags & ApplyFlags::Proposal) != ApplyFlags::None)
         return tesSUCCESS;
 
     auto const parentBatchId = ctx.tx.getTransactionID();

src/libxrpl/tx/transactors/system/Change.cpp

@@ -8,6 +8,7 @@
 #include <xrpl/beast/utility/instrumentation.h>
 #include <xrpl/core/ServiceRegistry.h>
 #include <xrpl/ledger/AmendmentTable.h>
+#include <xrpl/ledger/entries/FeeSettingsEntry.h>
 #include <xrpl/protocol/Feature.h>
 #include <xrpl/protocol/Indexes.h>
 #include <xrpl/protocol/Protocol.h>
@@ -260,16 +261,14 @@ Change::applyAmendment()
 TER
 Change::applyFee()
 {
-    auto const k = keylet::feeSettings();
-
-    SLE::pointer feeObject = view().peek(k);
+    FeeSettingsEntryW feeObject(view());
 
     if (!feeObject)
     {
-        feeObject = std::make_shared<SLE>(k);
-        view().insert(feeObject);
+        feeObject.newSLE();
+        feeObject.insert();
     }
-    auto set = [](SLE::pointer& feeObject, STTx const& tx, auto const& field) {
+    auto set = [](FeeSettingsEntryW& feeObject, STTx const& tx, auto const& field) {
         feeObject->at(field) = tx[field];
     };
     if (view().rules().enabled(featureXRPFees))
@@ -291,7 +290,7 @@ Change::applyFee()
         set(feeObject, ctx_.tx, sfReserveIncrement);
     }
 
-    view().update(feeObject);
+    feeObject.update();
 
     JLOG(j_.warn()) << "Fees have been changed";
     return tesSUCCESS;

src/libxrpl/tx/transactors/token/ConfidentialMPTHolderKeyUpdate.cpp

@@ -0,0 +1,220 @@
+#include <xrpl/tx/transactors/token/ConfidentialMPTHolderKeyUpdate.h>
+
+#include <xrpl/basics/Slice.h>
+#include <xrpl/beast/utility/Journal.h>
+#include <xrpl/beast/utility/instrumentation.h>
+#include <xrpl/core/ServiceRegistry.h>
+#include <xrpl/ledger/ReadView.h>
+#include <xrpl/protocol/ConfidentialTransfer.h>
+#include <xrpl/protocol/Feature.h>
+#include <xrpl/protocol/Indexes.h>
+#include <xrpl/protocol/LedgerFormats.h>
+#include <xrpl/protocol/MPTIssue.h>
+#include <xrpl/protocol/Protocol.h>
+#include <xrpl/protocol/SField.h>
+#include <xrpl/protocol/TER.h>
+#include <xrpl/protocol/TxFlags.h>
+#include <xrpl/protocol/XRPAmount.h>
+#include <xrpl/tx/Transactor.h>
+
+#include <bit>
+#include <cstdint>
+
+namespace xrpl {
+
+bool
+ConfidentialMPTHolderKeyUpdate::checkExtraFeatures(PreflightContext const& ctx)
+{
+    // Holder key update is only meaningful when confidential transfers are enabled.
+    return ctx.rules.enabled(featureConfidentialTransfer);
+}
+
+std::uint32_t
+ConfidentialMPTHolderKeyUpdate::getFlagsMask(PreflightContext const& ctx)
+{
+    return tfConfidentialMPTHolderKeyUpdateMask;
+}
+
+NotTEC
+ConfidentialMPTHolderKeyUpdate::preflight(PreflightContext const& ctx)
+{
+    bool const rotation = ctx.tx.isFlag(tfHolderKeyRotation);
+    bool const recovery = ctx.tx.isFlag(tfHolderKeyRecovery);
+    bool const cancel = ctx.tx.isFlag(tfCancelRecovery);
+
+    // Exactly one of the three mode flags must be set.
+    static constexpr auto modeFlags = tfHolderKeyRotation | tfHolderKeyRecovery | tfCancelRecovery;
+    if (std::popcount(ctx.tx.getFlags() & modeFlags) != 1)
+        return temINVALID_FLAG;
+
+    // The issuer cannot hold confidential balances.
+    if (ctx.tx[sfAccount] == MPTIssue(ctx.tx[sfMPTokenIssuanceID]).getIssuer())
+        return temMALFORMED;
+
+    bool const hasHolderKey = ctx.tx.isFieldPresent(sfHolderEncryptionKey);
+    bool const hasSpending = ctx.tx.isFieldPresent(sfConfidentialBalanceSpending);
+    bool const hasInbox = ctx.tx.isFieldPresent(sfConfidentialBalanceInbox);
+    bool const hasProof = ctx.tx.isFieldPresent(sfZKProof);
+
+    if (cancel)
+    {
+        // Cancel mode only revokes a pending recovery authorization; it
+        // carries no key material, balances, or proof.
+        if (hasHolderKey || hasSpending || hasInbox || hasProof)
+            return temMALFORMED;
+
+        return tesSUCCESS;
+    }
+
+    // Rotation and Recovery both require a holder key and a proof.
+    if (!hasHolderKey || !hasProof)
+        return temMALFORMED;
+
+    // Rotation mode requires re-encrypted balances; Recovery mode must not
+    // provide them since the holder cannot decrypt the current ones.
+    if (rotation && (!hasSpending || !hasInbox))
+        return temMALFORMED;
+
+    if (recovery && (hasSpending || hasInbox))
+        return temMALFORMED;
+
+    if (hasSpending &&
+        ctx.tx[sfConfidentialBalanceSpending].length() != kEcGamalEncryptedTotalLength)
+        return temBAD_CIPHERTEXT;
+
+    if (hasInbox && ctx.tx[sfConfidentialBalanceInbox].length() != kEcGamalEncryptedTotalLength)
+        return temBAD_CIPHERTEXT;
+
+    if (!isValidCompressedECPoint(ctx.tx[sfHolderEncryptionKey]))
+        return temMALFORMED;
+
+    if (hasSpending && !isValidCiphertext(ctx.tx[sfConfidentialBalanceSpending]))
+        return temBAD_CIPHERTEXT;
+
+    if (hasInbox && !isValidCiphertext(ctx.tx[sfConfidentialBalanceInbox]))
+        return temBAD_CIPHERTEXT;
+
+    return tesSUCCESS;
+}
+
+XRPAmount
+ConfidentialMPTHolderKeyUpdate::calculateBaseFee(ReadView const& view, STTx const& tx)
+{
+    return Transactor::calculateBaseFee(view, tx, kConfidentialFeeMultiplier);
+}
+
+TER
+ConfidentialMPTHolderKeyUpdate::preclaim(PreclaimContext const& ctx)
+{
+    auto const account = ctx.tx[sfAccount];
+    auto const mptIssuanceID = ctx.tx[sfMPTokenIssuanceID];
+
+    auto const sleIssuance = ctx.view.read(keylet::mptokenIssuance(mptIssuanceID));
+    if (!sleIssuance)
+        return tecOBJECT_NOT_FOUND;
+
+    if (!sleIssuance->isFlag(lsfMPTCanHoldConfidentialBalance))
+        return tecNO_PERMISSION;
+
+    auto const sleMptoken = ctx.view.read(keylet::mptoken(mptIssuanceID, account));
+    if (!sleMptoken)
+        return tecOBJECT_NOT_FOUND;
+
+    if (!sleMptoken->isFieldPresent(sfHolderEncryptionKey) ||
+        !sleMptoken->isFieldPresent(sfConfidentialBalanceSpending) ||
+        !sleMptoken->isFieldPresent(sfConfidentialBalanceInbox))
+    {
+        return tecNO_PERMISSION;
+    }
+
+    if (ctx.tx.isFlag(tfCancelRecovery))
+    {
+        // Nothing to cancel if no recovery is pending.
+        if (!sleMptoken->isFieldPresent(sfRecoveryKey))
+            return tecNO_PERMISSION;
+
+        return tesSUCCESS;
+    }
+
+    if (ctx.tx[sfHolderEncryptionKey] == (*sleMptoken)[sfHolderEncryptionKey])
+        return tecDUPLICATE;
+
+    // Recovery mode: reject if a recovery is already pending
+    if (ctx.tx.isFlag(tfHolderKeyRecovery) && sleMptoken->isFieldPresent(sfRecoveryKey))
+        return tecNO_PERMISSION;
+
+    return tesSUCCESS;
+}
+
+TER
+ConfidentialMPTHolderKeyUpdate::doApply()
+{
+    auto const mptIssuanceID = ctx_.tx[sfMPTokenIssuanceID];
+    auto sleMptoken = view().peek(keylet::mptoken(mptIssuanceID, accountID_));
+    if (!sleMptoken)
+    {
+        // LCOV_EXCL_START
+        UNREACHABLE(
+            "xrpl::ConfidentialMPTHolderKeyUpdate::doApply : preclaim already validated the "
+            "MPToken exists");
+        return tecINTERNAL;
+        // LCOV_EXCL_STOP
+    }
+
+    if (ctx_.tx.isFlag(tfCancelRecovery))
+    {
+        // The holder revokes their pending recovery authorization; the
+        // current key and balances are left untouched.
+        sleMptoken->makeFieldAbsent(sfRecoveryKey);
+        view().update(sleMptoken);
+        return tesSUCCESS;
+    }
+
+    auto const newPubKey = ctx_.tx[sfHolderEncryptionKey];
+
+    if (ctx_.tx.isFlag(tfHolderKeyRotation))
+    {
+        // Replace the key and balances in rotation mode. Rotation proves the
+        // holder still has the old key, so any pending recovery is cancelled.
+        (*sleMptoken)[sfHolderEncryptionKey] = newPubKey;
+        (*sleMptoken)[sfConfidentialBalanceSpending] = ctx_.tx[sfConfidentialBalanceSpending];
+        (*sleMptoken)[sfConfidentialBalanceInbox] = ctx_.tx[sfConfidentialBalanceInbox];
+        sleMptoken->makeFieldAbsent(sfRecoveryKey);
+        incrementConfidentialVersion(*sleMptoken);
+    }
+    else if (ctx_.tx.isFlag(tfHolderKeyRecovery))
+    {
+        // Recovery mode: the holder cannot decrypt their current balances,
+        // so only the pending recovery key is recorded. The balances are
+        // rewritten separately by the issuer via ConfidentialMPTRecoverBalance.
+        (*sleMptoken)[sfRecoveryKey] = newPubKey;
+    }
+    else
+    {
+        // LCOV_EXCL_START
+        UNREACHABLE("xrpl::ConfidentialMPTHolderKeyUpdate::doApply : invalid mode");
+        return tecINTERNAL;
+        // LCOV_EXCL_STOP
+    }
+
+    view().update(sleMptoken);
+    return tesSUCCESS;
+}
+
+void
+ConfidentialMPTHolderKeyUpdate::visitInvariantEntry(bool, SLE::ConstRef, SLE::ConstRef)
+{
+}
+
+bool
+ConfidentialMPTHolderKeyUpdate::finalizeInvariants(
+    STTx const&,
+    TER,
+    XRPAmount,
+    ReadView const&,
+    beast::Journal const&)
+{
+    return true;
+}
+
+}  // namespace xrpl

src/test/app/AMMClawbackMPT_test.cpp

@@ -31,6 +31,15 @@
 namespace xrpl::test {
 class AMMClawbackMPT_test : public beast::unit_test::Suite
 {
+    // SingleAssetVault, LendingProtocol and MPTokensV2 enable the large
+    // Number mantissa.
+    static bool
+    largeMantissa(FeatureBitset const& features)
+    {
+        return features[featureSingleAssetVault] || features[featureLendingProtocol] ||
+            features[featureMPTokensV2];
+    }
+
     void
     testInvalidRequest(FeatureBitset features)
     {
@@ -1724,7 +1733,7 @@ class AMMClawbackMPT_test : public beast::unit_test::Suite
                     .asString();
             auto const lpTokenBalance =
                 amm.ammRpcInfo()[jss::amm][jss::lp_token][jss::value].asString();
-            if (features[featureSingleAssetVault] || features[featureLendingProtocol])
+            if (largeMantissa(features))
             {
                 BEAST_EXPECT(lpToken == "1.414213562374011" && lpTokenBalance == "1.4142135623741");
             }
@@ -1741,16 +1750,14 @@ class AMMClawbackMPT_test : public beast::unit_test::Suite
                 env(amm::ammClawback(gw, alice, usd, eur, std::nullopt));
                 BEAST_EXPECT(!amm.ammExists());
             }
-            else if (
-                features[fixAMMv1_3] &&
-                (features[featureSingleAssetVault] || features[featureLendingProtocol]))
+            else if (features[fixAMMv1_3] && largeMantissa(features))
             {
                 env(amm::ammClawback(gw, alice, usd, eur, std::nullopt));
                 // Without the Rounding feature and with new Number a dust pool
                 // amount remains
                 BEAST_EXPECT(amm.ammExists());
             }
-            else if (!features[featureSingleAssetVault] && !features[featureLendingProtocol])
+            else if (!largeMantissa(features))
             {
                 env(amm::ammClawback(gw, alice, usd, eur, std::nullopt), Ter(tecINTERNAL));
                 BEAST_EXPECT(amm.ammExists());
@@ -1794,7 +1801,7 @@ class AMMClawbackMPT_test : public beast::unit_test::Suite
                     .asString();
             auto const lpTokenBalance =
                 amm.ammRpcInfo()[jss::amm][jss::lp_token][jss::value].asString();
-            if (!features[featureSingleAssetVault] && !features[featureLendingProtocol])
+            if (!largeMantissa(features))
             {
                 BEAST_EXPECT(lpToken == "1.414213562374011" && lpTokenBalance == "1.414213562374");
             }
@@ -1811,16 +1818,14 @@ class AMMClawbackMPT_test : public beast::unit_test::Suite
                 env(amm::ammClawback(gw, alice, usd, eur, std::nullopt));
                 BEAST_EXPECT(!amm.ammExists());
             }
-            else if (
-                features[fixAMMv1_3] &&
-                (features[featureSingleAssetVault] || features[featureLendingProtocol]))
+            else if (features[fixAMMv1_3] && largeMantissa(features))
             {
                 // Without the Rounding feature and with new Number a dust pool
                 // amount remains
                 env(amm::ammClawback(gw, alice, usd, eur, std::nullopt));
                 BEAST_EXPECT(amm.ammExists());
             }
-            else if (!features[featureSingleAssetVault] && !features[featureLendingProtocol])
+            else if (!largeMantissa(features))
             {
                 env(amm::ammClawback(gw, alice, usd, eur, std::nullopt), Ter(tecINTERNAL));
                 BEAST_EXPECT(amm.ammExists());

src/test/app/AMMClawback_test.cpp

@@ -2857,8 +2857,8 @@ class AMMClawback_test : public beast::unit_test::Suite
     {
         // For now, just disable SAV entirely, which locks in the small Number
         // mantissas
-        FeatureBitset const all =
-            jtx::testableAmendments() - featureSingleAssetVault - featureLendingProtocol;
+        FeatureBitset const all = jtx::testableAmendments() - featureSingleAssetVault -
+            featureLendingProtocol - featureMPTokensV2;
 
         testInvalidRequest(all);
         testInvalidRequest(all - featureMPTokensV2);

src/test/app/AMMExtendedMPT_test.cpp

@@ -116,7 +116,7 @@ private:
             Txflags(tfPartialPayment));
 
         BEAST_EXPECT(ammCarol.expectBalances(
-            btc(1'001'000'000'374'816), eth(100'000'000'000'000'000), ammCarol.tokens()));
+            btc(1'001'000'000'374'814), eth(100'000'000'000'000'000), ammCarol.tokens()));
 
         env.require(Balance(bob_, eth(200'100'000'000'000'000)));
         BEAST_EXPECT(isOffer(env, carol_, btc(49'000'000'000'000), XRP(49)));
@@ -1890,7 +1890,7 @@ private:
             auto const flowResult = [&] {
                 STAmount const deliver(eth(51'000'000));
                 STAmount smax(btc(61'000'000));
-                PaymentSandbox sb(env.current().get(), TapNone);
+                PaymentSandbox sb(env.current().get(), ApplyFlags::None);
                 STPathSet paths;
                 auto ipe = [](MPTTester const& iss) {
                     return STPathElement(
@@ -1928,7 +1928,7 @@ private:
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
                 if (flowResult.removableOffers.empty())
                     return false;
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 for (auto const& o : flowResult.removableOffers)
                 {
                     if (auto ok = sb.peek(keylet::offer(o)))

src/test/app/AMMExtended_test.cpp

@@ -73,7 +73,8 @@ class AMMExtended_test : public jtx::AMMTest
     // For now, just disable SAV entirely, which locks in the small Number
     // mantissas
     FeatureBitset const all_{
-        testableAmendments() - featureSingleAssetVault - featureLendingProtocol};
+        testableAmendments() - featureSingleAssetVault - featureLendingProtocol -
+        featureMPTokensV2};
 
 private:
     void
@@ -267,39 +268,20 @@ private:
             {features});
 
         // tfPassive -- place the offer without crossing it.
-        if (features[featureMPTokensV2])
-        {
-            Env env{*this, features};
-            fund(env, gw_, {alice_, carol_}, XRP(30'000'000), {USD(30'000'000)});
-
-            AMM const ammAlice(env, alice_, XRP(10'100'000), USD(10'000'000));
-
-            // Scale the exact-quality fixture up so the visual relationship
-            // stays clear: the passive CLOB offer has the same 1:1 quality as
-            // the generated AMM offer, so it should not cross.
-            env(offer(carol_, XRP(100'000), USD(100'000), tfPassive));
-            env.close();
-            BEAST_EXPECT(
-                ammAlice.expectBalances(XRP(10'100'000), USD(10'000'000), ammAlice.tokens()));
-            BEAST_EXPECT(expectOffers(env, carol_, 1, {{{XRP(100'000), USD(100'000)}}}));
-        }
-        else
-        {
-            testAMM(
-                [&](AMM& ammAlice, Env& env) {
-                    // Carol creates a passive offer that could cross AMM.
-                    // Carol's offer should stay in the ledger.
-                    env(offer(carol_, XRP(100), USD(100), tfPassive));
-                    env.close();
-                    BEAST_EXPECT(ammAlice.expectBalances(
-                        XRP(10'100), STAmount{USD, 10'000}, ammAlice.tokens()));
-                    BEAST_EXPECT(expectOffers(env, carol_, 1, {{{XRP(100), STAmount{USD, 100}}}}));
-                },
-                {{XRP(10'100), USD(10'000)}},
-                0,
-                std::nullopt,
-                {features});
-        }
+        testAMM(
+            [&](AMM& ammAlice, Env& env) {
+                // Carol creates a passive offer that could cross AMM.
+                // Carol's offer should stay in the ledger.
+                env(offer(carol_, XRP(100), USD(100), tfPassive));
+                env.close();
+                BEAST_EXPECT(
+                    ammAlice.expectBalances(XRP(10'100), STAmount{USD, 10'000}, ammAlice.tokens()));
+                BEAST_EXPECT(expectOffers(env, carol_, 1, {{{XRP(100), STAmount{USD, 100}}}}));
+            },
+            {{XRP(10'100), USD(10'000)}},
+            0,
+            std::nullopt,
+            {features});
 
         // tfPassive -- cross only offers of better quality.
         testAMM(
@@ -1450,7 +1432,6 @@ private:
         testRmFundedOffer(all_ - fixAMMv1_1 - fixAMMv1_3);
         testEnforceNoRipple(all_);
         testFillModes(all_);
-        testFillModes(all_ - featureMPTokensV2);
         testOfferCrossWithXRP(all_);
         testOfferCrossWithLimitOverride(all_);
         testCurrencyConversionEntire(all_);
@@ -2068,7 +2049,7 @@ private:
             auto const flowResult = [&] {
                 STAmount const deliver(USD(51));
                 STAmount smax(BTC(61));
-                PaymentSandbox sb(env.current().get(), TapNone);
+                PaymentSandbox sb(env.current().get(), ApplyFlags::None);
                 STPathSet paths;
                 auto ipe = [](Issue const& iss) {
                     return STPathElement(
@@ -2106,7 +2087,7 @@ private:
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
                 if (flowResult.removableOffers.empty())
                     return false;
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 for (auto const& o : flowResult.removableOffers)
                 {
                     if (auto ok = sb.peek(keylet::offer(o)))

src/test/app/AMMMPT_test.cpp

@@ -1451,12 +1451,14 @@ private:
                 auto carolXRP = env.balance(carol_, XRP);
                 auto carolMPT = env.balance(carol_, MPT(ammAlice[1]));
 
+                // The exact deposit is 201; rounding in the pool's favor at
+                // the large mantissa takes one more unit.
                 ammAlice.deposit(carol_, 100'000, MPT(ammAlice[1])(205));
                 BEAST_EXPECT(ammAlice.expectBalances(
-                    XRP(10'000), MPT(ammAlice[1])(10'201), IOUAmount{10'100'000, 0}));
+                    XRP(10'000), MPT(ammAlice[1])(10'202), IOUAmount{10'100'000, 0}));
 
                 env.require(Balance(carol_, carolXRP - drops(baseFee)));
-                env.require(Balance(carol_, carolMPT - MPT(ammAlice[1])(201)));
+                env.require(Balance(carol_, carolMPT - MPT(ammAlice[1])(202)));
             },
             {{XRP(10'000), gAmmmpt(10'000)}});
 
@@ -1467,11 +1469,13 @@ private:
                 auto carolXRP = env.balance(carol_, XRP);
                 auto carolMPT = env.balance(carol_, MPT(ammAlice[1]));
 
+                // The exact deposit is 201 XRP; rounding in the pool's favor
+                // at the large mantissa takes one more drop.
                 ammAlice.deposit(carol_, 100'000, XRP(205));
                 BEAST_EXPECT(ammAlice.expectBalances(
-                    XRP(10'201), MPT(ammAlice[1])(10'000), IOUAmount{10'100'000, 0}));
+                    XRPAmount{10'201'000'001}, MPT(ammAlice[1])(10'000), IOUAmount{10'100'000, 0}));
 
-                env.require(Balance(carol_, carolXRP - XRP(201) - drops(baseFee)));
+                env.require(Balance(carol_, carolXRP - XRPAmount{201'000'001} - drops(baseFee)));
                 env.require(Balance(carol_, carolMPT));
             },
             {{XRP(10'000), gAmmmpt(10'000)}});
@@ -1551,10 +1555,10 @@ private:
                     STAmount{ammAlice.lptIssue(), 2004, -6});
 
                 BEAST_EXPECT(ammAlice.expectBalances(
-                    XRP(10'000), MPT(ammAlice[1])(10'081), IOUAmount{10'039'920'31840891, -8}));
+                    XRP(10'000), MPT(ammAlice[1])(10'080), IOUAmount{10'039'920'3184089, -7}));
 
                 env.require(Balance(carol_, carolXRP - drops(baseFee)));
-                env.require(Balance(carol_, carolMPT - MPT(ammAlice[1])(81)));
+                env.require(Balance(carol_, carolMPT - MPT(ammAlice[1])(80)));
             },
             {{XRP(10'000), gAmmmpt(10'000)}});
 
@@ -1573,10 +1577,10 @@ private:
                     STAmount{ammAlice.lptIssue(), 2004, -6});
 
                 BEAST_EXPECT(ammAlice.expectBalances(
-                    XRP(10'000), MPT(ammAlice[1])(10'081), IOUAmount{10'039'920'31840891, -8}));
+                    XRP(10'000), MPT(ammAlice[1])(10'080), IOUAmount{10'039'920'3184089, -7}));
 
                 env.require(Balance(carol_, carolXRP - drops(baseFee)));
-                env.require(Balance(carol_, carolMPT - MPT(ammAlice[1])(81)));
+                env.require(Balance(carol_, carolMPT - MPT(ammAlice[1])(80)));
             },
             {{XRP(10'000), gAmmmpt(10'000)}});
 
@@ -1797,9 +1801,9 @@ private:
 
                 ammAlice.deposit(gw_, MPT(ammAlice[0])(1000));
                 BEAST_EXPECT(ammAlice.expectBalances(
-                    MPT(ammAlice[0])(1'010'999),
+                    MPT(ammAlice[0])(1'011'000),
                     MPT(ammAlice[1])(1'010'000),
-                    IOUAmount{1'010'499'376546071, -9}));
+                    IOUAmount{1'010'499'876298854, -9}));
             },
             {{gAmmmpt(10'000), gAmmmpt(10'000)}});
 
@@ -2212,7 +2216,7 @@ private:
                 if (env.enabled(fixAMMv1_3))
                 {
                     BEAST_EXPECT(ammAlice.expectBalances(
-                        MPT(ammAlice[0])(1), STAmount{USD, 1, -11}, IOUAmount{1, -8}));
+                        MPT(ammAlice[0])(1), STAmount{USD, 1, -12}, IOUAmount{1, -9}));
                 }
             },
             {{gAmmmpt(10'000'000'000), USD(10'000)}},
@@ -2541,11 +2545,12 @@ private:
                 // XRP amount to withdraw is 0
                 ammAlice.withdraw(
                     alice_, IOUAmount{1, -5}, std::nullopt, std::nullopt, Ter(tecAMM_FAILED));
-                // Calculated tokens to withdraw are 0
+                // Calculated tokens to withdraw are 0: 1e-16 of 10,000 USD is
+                // below the large Number mantissa's precision
                 ammAlice.withdraw(
                     alice_,
                     std::nullopt,
-                    STAmount{USD, 1, -11},
+                    STAmount{USD, 1, -16},
                     std::nullopt,
                     Ter(tecAMM_INVALID_TOKENS));
                 ammAlice.deposit(carol_, STAmount{USD, 1, -10});
@@ -2707,7 +2712,7 @@ private:
                 BEAST_EXPECT(ammAlice.expectBalances(
                     XRPAmount(9000'000001),
                     MPT(ammAlice[1])(10'000),
-                    IOUAmount{9'486'832'98050514, -8}));
+                    IOUAmount{9'486'832'980505138, -9}));
             },
             {{XRP(10'000), gAmmmpt(10'000)}});
         testAMM(
@@ -2715,7 +2720,7 @@ private:
                 // single withdraw MPT from XRP/MPT
                 ammAlice.withdraw(alice_, MPT(ammAlice[1])(1'000));
                 BEAST_EXPECT(ammAlice.expectBalances(
-                    XRP(10000), MPT(ammAlice[1])(9001), IOUAmount{9'486'832'98050514, -8}));
+                    XRP(10000), MPT(ammAlice[1])(9001), IOUAmount{9'486'832'980505138, -9}));
             },
             {{XRP(10'000), gAmmmpt(10'000)}});
         testAMM(
@@ -2723,9 +2728,7 @@ private:
                 // single withdraw IOU from IOU/MPT
                 ammAlice.withdraw(alice_, USD(1'000));
                 BEAST_EXPECT(ammAlice.expectBalances(
-                    STAmount{USD, UINT64_C(9000'000000000004), -12},
-                    MPT(ammAlice[1])(10'000),
-                    IOUAmount{9486'83298050514, -11}));
+                    USD(9'000), MPT(ammAlice[1])(10'000), IOUAmount{9486'832980505138, -12}));
             },
             {{USD(10'000), gAmmmpt(10'000)}});
         testAMM(
@@ -2733,7 +2736,7 @@ private:
                 // single withdraw MPT from IOU/MPT
                 ammAlice.withdraw(alice_, MPT(ammAlice[1])(1'000));
                 BEAST_EXPECT(ammAlice.expectBalances(
-                    USD(10'000), MPT(ammAlice[1])(9001), IOUAmount{9486'83298050514, -11}));
+                    USD(10'000), MPT(ammAlice[1])(9001), IOUAmount{9486'832980505138, -12}));
             },
             {{USD(10'000), gAmmmpt(10'000)}});
         testAMM(
@@ -2743,7 +2746,7 @@ private:
                 BEAST_EXPECT(ammAlice.expectBalances(
                     MPT(ammAlice[0])(9001),
                     MPT(ammAlice[1])(10'000),
-                    IOUAmount{9486'83298050514, -11}));
+                    IOUAmount{9486'832980505138, -12}));
             },
             {{gAmmmpt(10'000), gAmmmpt(10'000)}});
 
@@ -3024,7 +3027,7 @@ private:
                 ammAlice.deposit(carol_, 1'000);
                 ammAlice.withdrawAll(carol_, USD(0));
                 BEAST_EXPECT(ammAlice.expectBalances(
-                    STAmount{USD, UINT64_C(9'090'909090909092), -12},
+                    STAmount{USD, UINT64_C(9'090'909090909091), -12},
                     MPT(ammAlice[1])(11'000),
                     IOUAmount{10'000}));
             },
@@ -3249,7 +3252,7 @@ private:
                 BEAST_EXPECT(ammAlice.expectBalances(
                     MPT(ammAlice[0])(10'000'000'000),
                     STAmount{USD, 1, -11},
-                    IOUAmount{316227765, -9}));
+                    IOUAmount{316227766, -9}));
             },
             {{gAmmmpt(10'000'000'000), USD(10'000)}});
         // XRP
@@ -4155,7 +4158,7 @@ private:
                 auto jtx = env.jt(tx, Seq(1), Fee(10));
                 env.app().config().features.erase(featureMPTokensV2);
                 PreflightContext const ctx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = AMMBid::checkExtraFeatures(ctx);
                 BEAST_EXPECT(pf == false);
                 env.app().config().features.insert(featureMPTokensV2);
@@ -4167,7 +4170,7 @@ private:
                 jtx.jv["Asset2"].removeMember("mpt_issuance_id");
                 jtx.stx = env.ust(jtx);
                 PreflightContext const ctx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = AMMBid::preflight(ctx);
                 BEAST_EXPECT(pf == temBAD_AMM_TOKENS);
             }
@@ -5960,7 +5963,7 @@ private:
                 if (!features[fixAMMv1_3])
                 {
                     BEAST_EXPECT(tokensFee == IOUAmount(98'019'80198019, -8));
-                    BEAST_EXPECT(tokensNoFee == IOUAmount(98'495'13933556, -8));
+                    BEAST_EXPECT(tokensNoFee == IOUAmount(98'495'13933557, -8));
                 }
                 else
                 {

src/test/app/AMM_test.cpp

@@ -84,7 +84,8 @@ private:
     {
         // For now, just disable SAV entirely, which locks in the small Number
         // mantissas
-        return jtx::testableAmendments() - featureSingleAssetVault - featureLendingProtocol;
+        return jtx::testableAmendments() - featureSingleAssetVault - featureLendingProtocol -
+            featureMPTokensV2;
     }
 
     // Seed from the local testableAmendments() which strips SAV and Lending.
@@ -3262,7 +3263,7 @@ private:
                 auto jtx = env.jt(tx, Seq(1), Fee(baseFee));
                 env.app().config().features.erase(featureAMM);
                 PreflightContext const pfCtx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = Transactor::invokePreflight<AMMBid>(pfCtx);
                 BEAST_EXPECT(pf == temDISABLED);
                 env.app().config().features.insert(featureAMM);
@@ -3273,7 +3274,7 @@ private:
                 jtx.jv["TxnSignature"] = "deadbeef";
                 jtx.stx = env.ust(jtx);
                 PreflightContext const pfCtx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = Transactor::invokePreflight<AMMBid>(pfCtx);
                 BEAST_EXPECT(!isTesSuccess(pf));
             }
@@ -3284,7 +3285,7 @@ private:
                 jtx.jv["Asset2"].removeMember("issuer");
                 jtx.stx = env.ust(jtx);
                 PreflightContext const pfCtx(
-                    env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                    env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
                 auto pf = Transactor::invokePreflight<AMMBid>(pfCtx);
                 BEAST_EXPECT(pf == temBAD_AMM_TOKENS);
             }
@@ -3810,7 +3811,7 @@ private:
                     BEAST_EXPECT(amm.expectBalances(XRP(1'000), USD(500), amm.tokens()));
                     BEAST_EXPECT(expectOffers(env, carol_, 1, {{Amounts{XRP(100), USD(55)}}}));
                 }
-                else if (!features[featureMPTokensV2])
+                else
                 {
                     BEAST_EXPECT(amm.expectBalances(
                         XRPAmount(909'090'909),
@@ -3825,30 +3826,6 @@ private:
                         env.balance(carol_, USD) ==
                         STAmount(USD, UINT64_C(29'949'94999999494), -11));
                 }
-                else
-                {
-                    // Post-amendment the transfer fee is taken into account
-                    // when calculating the limit out based on limitQuality.
-                    // This increases the limitQuality and decreases
-                    // the limit out. Consequently, AMM offer size is decreased,
-                    // and the quality is increased, matching the overall
-                    // quality.
-                    // AMM offer ~50USD/91XRP
-                    BEAST_EXPECT(amm.expectBalances(
-                        XRPAmount(909'090'910),
-                        STAmount{USD, UINT64_C(549'99999945), -8},
-                        amm.tokens()));
-                    // Offer ~91XRP/50USD
-                    BEAST_EXPECT(expectOffers(
-                        env,
-                        carol_,
-                        1,
-                        {{Amounts{XRPAmount{9'090'910}, STAmount{USD, 5'0000005, -7}}}}));
-                    // Carol pays 0.1% fee on ~50USD =~ 0.05USD
-                    BEAST_EXPECT(
-                        env.balance(carol_, USD) ==
-                        STAmount(USD, UINT64_C(29'949'95000060055), -11));
-                }
             },
             {{XRP(1'000), USD(500)}},
             0,
@@ -6498,7 +6475,7 @@ private:
                 BEAST_EXPECT(expectOffers(env, bob_, 1, {{Amounts{USD(1), XRPAmount(500)}}}));
                 BEAST_EXPECT(expectOffers(env, carol_, 1, {{Amounts{XRP(100), USD(55)}}}));
             }
-            else if (!features[featureMPTokensV2])
+            else
             {
                 BEAST_EXPECT(amm.expectBalances(
                     XRPAmount(909'090'909),
@@ -6511,19 +6488,6 @@ private:
                     {{Amounts{XRPAmount{9'090'909}, STAmount{USD, 4'99999995, -8}}}}));
                 BEAST_EXPECT(expectOffers(env, bob_, 1, {{Amounts{USD(1), XRPAmount(500)}}}));
             }
-            else
-            {
-                BEAST_EXPECT(amm.expectBalances(
-                    XRPAmount(909'090'910),
-                    STAmount{USD, UINT64_C(549'99999945), -8},
-                    amm.tokens()));
-                BEAST_EXPECT(expectOffers(
-                    env,
-                    carol_,
-                    1,
-                    {{Amounts{XRPAmount{9'090'910}, STAmount{USD, 5'0000005, -7}}}}));
-                BEAST_EXPECT(expectOffers(env, bob_, 1, {{Amounts{USD(1), XRPAmount(500)}}}));
-            }
         }
 
         // There is no blocking offer, the same AMM liquidity is consumed
@@ -6535,30 +6499,10 @@ private:
             AMM const amm(env, alice_, XRP(1'000), USD(500));
             env(offer(carol_, XRP(100), USD(55)));
             env.close();
-            if (!features[featureMPTokensV2])
-            {
-                BEAST_EXPECT(amm.expectBalances(
-                    XRPAmount(909'090'909),
-                    STAmount{USD, UINT64_C(550'000000055), -9},
-                    amm.tokens()));
-                BEAST_EXPECT(expectOffers(
-                    env,
-                    carol_,
-                    1,
-                    {{Amounts{XRPAmount{9'090'909}, STAmount{USD, 4'99999995, -8}}}}));
-            }
-            else
-            {
-                BEAST_EXPECT(amm.expectBalances(
-                    XRPAmount(909'090'910),
-                    STAmount{USD, UINT64_C(549'99999945), -8},
-                    amm.tokens()));
-                BEAST_EXPECT(expectOffers(
-                    env,
-                    carol_,
-                    1,
-                    {{Amounts{XRPAmount{9'090'910}, STAmount{USD, 5'0000005, -7}}}}));
-            }
+            BEAST_EXPECT(amm.expectBalances(
+                XRPAmount(909'090'909), STAmount{USD, UINT64_C(550'000000055), -9}, amm.tokens()));
+            BEAST_EXPECT(expectOffers(
+                env, carol_, 1, {{Amounts{XRPAmount{9'090'909}, STAmount{USD, 4'99999995, -8}}}}));
         }
     }
 
@@ -7448,8 +7392,6 @@ private:
                     .err = Ter(tecAMM_BALANCE)});
         };
 
-        // Bound holds regardless of the deposit-side fix amendment.
-        test(all - featureMPTokensV2);
         test(all);
     }
 
@@ -7481,7 +7423,6 @@ private:
         testFlags();
         testRippling();
         testAMMAndCLOB(all);
-        testAMMAndCLOB(all - featureMPTokensV2);
         testAMMAndCLOB(all - fixAMMv1_1 - fixAMMv1_3);
         testTradingFee(all);
         testTradingFee(all - fixAMMv1_3);
@@ -7501,10 +7442,8 @@ private:
         testOverflowOffer(all - fixAMMv1_1 - fixAMMv1_3);
         testSwapRounding();
         testFixChangeSpotPriceQuality(all);
-        testFixChangeSpotPriceQuality(all - featureMPTokensV2);
         testFixChangeSpotPriceQuality(all - fixAMMv1_1 - fixAMMv1_3);
         testFixAMMOfferBlockedByLOB(all);
-        testFixAMMOfferBlockedByLOB(all - featureMPTokensV2);
         testFixAMMOfferBlockedByLOB(all - fixAMMv1_1 - fixAMMv1_3);
         testLPTokenBalance(all);
         testLPTokenBalance(all - fixAMMv1_3);

src/test/app/AccountSet_test.cpp

@@ -594,7 +594,7 @@ public:
         stx->at(sfSigningPubKey) = makeSlice(std::string("badkey"));
 
         env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-            auto const result = xrpl::apply(env.app(), view, *stx, TapNone, j);
+            auto const result = xrpl::apply(env.app(), view, *stx, ApplyFlags::None, j);
             BEAST_EXPECT(result.ter == temBAD_SIGNATURE);
             BEAST_EXPECT(!result.applied);
             return result.applied;

src/test/app/Batch_test.cpp

@@ -436,7 +436,7 @@ class Batch_test : public beast::unit_test::Suite
         {
             auto jtx = env.jt(pay(alice, bob, XRP(1)), Txflags(tfInnerBatchTxn));
             PreflightContext const pfCtx(
-                env.app(), *jtx.stx, env.current()->rules(), TapNone, env.journal);
+                env.app(), *jtx.stx, env.current()->rules(), ApplyFlags::None, env.journal);
             auto const pf = Transactor::invokePreflight<Payment>(pfCtx);
             BEAST_EXPECT(pf == temINVALID_INNER_BATCH);
         }
@@ -451,7 +451,7 @@ class Batch_test : public beast::unit_test::Suite
                 disabledEnv.app(),
                 *jtx.stx,
                 disabledEnv.current()->rules(),
-                TapNone,
+                ApplyFlags::None,
                 disabledEnv.journal);
             auto const pf = Transactor::invokePreflight<Payment>(pfCtx);
             BEAST_EXPECT(pf == temINVALID_FLAG);
@@ -462,7 +462,12 @@ class Batch_test : public beast::unit_test::Suite
         {
             auto jtx = env.jt(pay(alice, bob, XRP(1)));
             PreflightContext const pfCtx(
-                env.app(), *jtx.stx, UInt256{1}, env.current()->rules(), TapBatch, env.journal);
+                env.app(),
+                *jtx.stx,
+                UInt256{1},
+                env.current()->rules(),
+                ApplyFlags::Batch,
+                env.journal);
             auto const pf = Transactor::invokePreflight<Payment>(pfCtx);
             BEAST_EXPECT(pf == temINVALID_INNER_BATCH);
         }
@@ -1590,7 +1595,7 @@ class Batch_test : public beast::unit_test::Suite
                 batch::Sig(std::vector<Reg>(kMaxBatchSigners + 1, bob)));
 
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-                auto const result = xrpl::apply(env.app(), view, *jt.stx, TapNone, j);
+                auto const result = xrpl::apply(env.app(), view, *jt.stx, ApplyFlags::None, j);
                 BEAST_EXPECT(!result.applied && result.ter == temARRAY_TOO_LARGE);
                 return result.applied;
             });
@@ -4391,7 +4396,7 @@ class Batch_test : public beast::unit_test::Suite
         BEAST_EXPECT(!passesLocalChecks(stx, reason));
         BEAST_EXPECT(reason == "Cannot submit pseudo transactions.");
         env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-            auto const result = xrpl::apply(env.app(), view, stx, TapNone, j);
+            auto const result = xrpl::apply(env.app(), view, stx, ApplyFlags::None, j);
             BEAST_EXPECT(!result.applied && result.ter == temINVALID_FLAG);
             return result.applied;
         });
@@ -5637,7 +5642,7 @@ class Batch_test : public beast::unit_test::Suite
                     obj.setFieldU32(sfFlags, tfInnerBatchTxn);
                 });
 
-                auto const result = xrpl::apply(env.app(), view, stx, TapNone, j);
+                auto const result = xrpl::apply(env.app(), view, stx, ApplyFlags::None, j);
                 // Must NOT be applied — signature was never checked
                 BEAST_EXPECT(!result.applied);
                 return false;

src/test/app/ConfidentialMPTKeyRotation_test.cpp

@@ -1,6 +1,7 @@
 #include <test/jtx/Account.h>
 #include <test/jtx/ConfidentialTransfer.h>
 #include <test/jtx/Env.h>
+#include <test/jtx/amount.h>
 #include <test/jtx/mpt.h>
 
 #include <xrpl/basics/Buffer.h>
@@ -20,6 +21,7 @@
 #include <cstdint>
 #include <memory>
 #include <optional>
+#include <utility>
 #include <vector>
 
 namespace xrpl {
@@ -2454,6 +2456,703 @@ class ConfidentialMPTKeyRotation_test : public ConfidentialTransferTestBase
         });
     }
 
+    void
+    testConfidentialMPTHolderKeyUpdatePreflight(FeatureBitset features)
+    {
+        testcase("ConfidentialMPTHolderKeyUpdate preflight");
+        using namespace test::jtx;
+
+        Env env{*this, features};
+        Account const alice("alice");
+        Account const bob("bob");
+
+        // Both amendments are required: ConfidentialMPTKeyRotation and ConfidentialTransfer.
+        if (!features[featureConfidentialMPTKeyRotation] || !features[featureConfidentialTransfer])
+        {
+            MPTTester mptAlice(env, alice, {.holders = {bob}});
+            mptAlice.create({.ownerCount = 1, .flags = tfMPTCanTransfer});
+            mptAlice.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = gMakeZeroBuffer(kEcPubKeyLength),
+                .flags = tfHolderKeyRecovery,
+                .err = temDISABLED,
+            });
+            return;
+        }
+
+        ConfidentialEnv ct{env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+
+        Account const bobNewKey("bobNewKey");
+        ct.mpt.generateKeyPair(bobNewKey);
+
+        // The flag contains a value outside the recognized mode bits. This is
+        // rejected by the flags-mask check
+        for (auto const flags : {0x00080000u, 0x00080000u | tfHolderKeyRecovery, 0x00100000u})
+        {
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+                .proof = gMakeZeroBuffer(1),
+                .flags = flags,
+                .err = temINVALID_FLAG,
+            });
+        }
+
+        // Exactly one of Rotation, Recovery, and Cancel must be set.
+        for (auto const flags :
+             {0u,
+              tfHolderKeyRotation | tfHolderKeyRecovery,
+              tfHolderKeyRotation | tfCancelRecovery,
+              tfHolderKeyRecovery | tfCancelRecovery,
+              tfHolderKeyRotation | tfHolderKeyRecovery | tfCancelRecovery})
+        {
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+                .proof = gMakeZeroBuffer(1),
+                .flags = flags,
+                .err = temINVALID_FLAG,
+            });
+        }
+
+        // The issuer cannot rotate or recover a confidential balance it cannot hold.
+        Account const aliceNewKey("aliceNewKey");
+        ct.mpt.generateKeyPair(aliceNewKey);
+        ct.mpt.holderKeyUpdate({
+            .account = alice,
+            .holderPubKey = ct.mpt.getPubKey(aliceNewKey),
+            .proof = gMakeZeroBuffer(1),
+            .flags = tfHolderKeyRecovery,
+            .err = temMALFORMED,
+        });
+
+        // HolderEncryptionKey one byte short of the required length.
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .holderPubKey = gMakeZeroBuffer(kEcPubKeyLength - 1),
+            .proof = gMakeZeroBuffer(1),
+            .flags = tfHolderKeyRecovery,
+            .err = temMALFORMED,
+        });
+
+        // HolderEncryptionKey the correct length, but not a well-formed
+        // compressed secp256k1 point.
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .holderPubKey = gMakeZeroBuffer(kEcPubKeyLength),
+            .proof = gMakeZeroBuffer(1),
+            .flags = tfHolderKeyRecovery,
+            .err = temMALFORMED,
+        });
+
+        // HolderEncryptionKey is entirely absent (as opposed to present with
+        // the wrong length or format).
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .proof = gMakeZeroBuffer(1),
+            .flags = tfHolderKeyRecovery,
+            .err = temMALFORMED,
+        });
+
+        std::optional<Buffer> const cipher = getTrivialCiphertext();
+        std::optional<Buffer> const none;
+
+        // Rotation mode requires both the spending and inbox ciphertexts;
+        for (auto const& [spending, inbox] :
+             {std::pair{none, none}, std::pair{cipher, none}, std::pair{none, cipher}})
+        {
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+                .spendingCiphertext = spending,
+                .inboxCiphertext = inbox,
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRotation,
+                .err = temMALFORMED,
+            });
+        }
+
+        // Recovery and Cancel modes must not include either.
+        for (auto const& [spending, inbox] :
+             {std::pair{cipher, none}, std::pair{none, cipher}, std::pair{cipher, cipher}})
+        {
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+                .spendingCiphertext = spending,
+                .inboxCiphertext = inbox,
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+                .err = temMALFORMED,
+            });
+        }
+
+        for (auto const& [spending, inbox] :
+             {std::pair{cipher, none}, std::pair{none, cipher}, std::pair{cipher, cipher}})
+        {
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .spendingCiphertext = spending,
+                .inboxCiphertext = inbox,
+                .flags = tfCancelRecovery,
+                .err = temMALFORMED,
+            });
+        }
+
+        // Spending ciphertext has the wrong length.
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+            .spendingCiphertext = gMakeZeroBuffer(kEcGamalEncryptedTotalLength - 1),
+            .inboxCiphertext = getTrivialCiphertext(),
+            .proof = gMakeZeroBuffer(1),
+            .flags = tfHolderKeyRotation,
+            .err = temBAD_CIPHERTEXT,
+        });
+
+        // Inbox ciphertext has the wrong length.
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+            .spendingCiphertext = getTrivialCiphertext(),
+            .inboxCiphertext = gMakeZeroBuffer(kEcGamalEncryptedTotalLength - 1),
+            .proof = gMakeZeroBuffer(1),
+            .flags = tfHolderKeyRotation,
+            .err = temBAD_CIPHERTEXT,
+        });
+
+        // Spending ciphertext has the correct length, but is not a
+        // well-formed EC ElGamal ciphertext.
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+            .spendingCiphertext = getBadCiphertext(),
+            .inboxCiphertext = getTrivialCiphertext(),
+            .proof = gMakeZeroBuffer(1),
+            .flags = tfHolderKeyRotation,
+            .err = temBAD_CIPHERTEXT,
+        });
+
+        // Inbox ciphertext has the correct length, but is not a well-formed
+        // EC ElGamal ciphertext.
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+            .spendingCiphertext = getTrivialCiphertext(),
+            .inboxCiphertext = getBadCiphertext(),
+            .proof = gMakeZeroBuffer(1),
+            .flags = tfHolderKeyRotation,
+            .err = temBAD_CIPHERTEXT,
+        });
+
+        // Rotation/Recovery mode requires a ZKProof.
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+            .flags = tfHolderKeyRecovery,
+            .err = temMALFORMED,
+        });
+
+        // Cancel mode must not include HolderEncryptionKey.
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+            .flags = tfCancelRecovery,
+            .err = temMALFORMED,
+        });
+
+        // Cancel mode must not include a ZKProof.
+        ct.mpt.holderKeyUpdate({
+            .account = bob,
+            .proof = gMakeZeroBuffer(1),
+            .flags = tfCancelRecovery,
+            .err = temMALFORMED,
+        });
+    }
+
+    void
+    testConfidentialMPTHolderKeyUpdatePreclaim(FeatureBitset features)
+    {
+        testcase("ConfidentialMPTHolderKeyUpdate preclaim");
+        using namespace test::jtx;
+
+        // The issuance does not exist.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            MPTTester mptAlice(env, alice, {.holders = {bob}});
+
+            mptAlice.create({
+                .ownerCount = 1,
+                .flags = tfMPTCanTransfer | tfMPTCanHoldConfidentialBalance,
+            });
+            // Destroy the issuance to test issuance not found.
+            mptAlice.destroy();
+
+            mptAlice.holderKeyUpdate({
+                .account = bob,
+                .flags = tfCancelRecovery,
+                .err = tecOBJECT_NOT_FOUND,
+            });
+        }
+
+        // The issuance has not enabled confidential balances. The holder is
+        // authorized so this reaches the confidential-balance-flag check
+        // rather than failing earlier on a missing MPToken.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            MPTTester mptAlice(env, alice, {.holders = {bob}});
+            mptAlice.create({.ownerCount = 1, .flags = tfMPTCanTransfer});
+            mptAlice.authorize({.account = bob});
+
+            mptAlice.holderKeyUpdate({
+                .account = bob,
+                .flags = tfCancelRecovery,
+                .err = tecNO_PERMISSION,
+            });
+        }
+
+        // carol exists as an account but was never authorized to hold this
+        // issuance, so she has no MPToken for it at all.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const carol("carol");
+            MPTTester mptAlice(env, alice);
+            mptAlice.create({
+                .ownerCount = 1,
+                .flags = tfMPTCanTransfer | tfMPTCanHoldConfidentialBalance,
+            });
+            env.fund(XRP(1000), carol);
+            env.close();
+
+            Account const carolNewKey("carolNewKey");
+            mptAlice.generateKeyPair(carolNewKey);
+
+            mptAlice.holderKeyUpdate({
+                .account = carol,
+                .holderPubKey = mptAlice.getPubKey(carolNewKey),
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+                .err = tecOBJECT_NOT_FOUND,
+            });
+        }
+
+        // The holder has an MPToken but no confidential state yet - never
+        // registered a key or converted anything.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            MPTTester mptAlice(env, alice, {.holders = {bob}});
+            mptAlice.create({
+                .ownerCount = 1,
+                .flags = tfMPTCanTransfer | tfMPTCanHoldConfidentialBalance,
+            });
+            mptAlice.authorize({.account = bob});
+            mptAlice.pay(alice, bob, 100);
+
+            Account const bobNewKey("bobNewKey");
+            mptAlice.generateKeyPair(bobNewKey);
+
+            mptAlice.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = mptAlice.getPubKey(bobNewKey),
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+                .err = tecNO_PERMISSION,
+            });
+        }
+
+        // Submitting the holder's own current key as the "new" key is a no-op.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bob),
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+                .err = tecDUPLICATE,
+            });
+        }
+
+        // A second Recovery-mode transaction must not silently overwrite an
+        // already-pending RecoveryKey.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+
+            Account const bobRecoveryKey("bobRecoveryKey");
+            ct.mpt.generateKeyPair(bobRecoveryKey);
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobRecoveryKey),
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+            });
+
+            Account const bobRecoveryKey2("bobRecoveryKey2");
+            ct.mpt.generateKeyPair(bobRecoveryKey2);
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobRecoveryKey2),
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+                .err = tecNO_PERMISSION,
+            });
+        }
+
+        // bob never submitted a Recovery-mode transaction, so there is no
+        // sfRecoveryKey to cancel.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .flags = tfCancelRecovery,
+                .err = tecNO_PERMISSION,
+            });
+        }
+
+        // Runs rotation, recovery, and cancel in sequence and expects each to
+        // succeed.
+        auto const allModesSucceed = [&](ConfidentialEnv& ct, Account const& bob) {
+            Account const bobNewKey("bobNewKey");
+            ct.mpt.generateKeyPair(bobNewKey);
+
+            auto const reEnc = reencryptHolderBalances(ct.mpt, bob, bob, bobNewKey);
+            BEAST_EXPECT(reEnc.has_value());
+            if (!reEnc)
+                return;
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+                .spendingCiphertext = reEnc->first,
+                .inboxCiphertext = reEnc->second,
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRotation,
+            });
+
+            Account const bobRecoveryKey("bobRecoveryKey");
+            ct.mpt.generateKeyPair(bobRecoveryKey);
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobRecoveryKey),
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+            });
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .flags = tfCancelRecovery,
+            });
+        };
+
+        // Individual (per-holder) lock.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+            ct.mpt.set({.account = alice, .holder = bob, .flags = tfMPTLock});
+
+            allModesSucceed(ct, bob);
+        }
+
+        // Global (issuance-wide) lock.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+            ct.mpt.set({.account = alice, .flags = tfMPTLock});
+
+            allModesSucceed(ct, bob);
+        }
+
+        // A stale mirror epoch does not block rotation, recovery, or cancel:
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+
+            // Rotate the issuer's key without refreshing bob's mirror,
+            // leaving bob's mirror epoch stale relative to the issuance.
+            Account const aliceNewIssuerKey("aliceNewIssuerKey");
+            ct.mpt.generateKeyPair(aliceNewIssuerKey);
+            ct.mpt.set({.account = alice, .issuerPubKey = ct.mpt.getPubKey(aliceNewIssuerKey)});
+            BEAST_EXPECT(ct.mpt.checkKeyEpochs(1u, std::nullopt));
+            BEAST_EXPECT(ct.mpt.checkMirrorEpochs(bob, std::nullopt, std::nullopt));
+
+            allModesSucceed(ct, bob);
+        }
+    }
+
+    void
+    testConfidentialMPTHolderKeyUpdateDoApply(FeatureBitset features)
+    {
+        testcase("ConfidentialMPTHolderKeyUpdate doApply");
+        using namespace test::jtx;
+
+        // Rotation mode updates the key and re-encrypted balances, bumps the
+        // version, and clears any pending recovery.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+
+            auto const prevVersion = ct.mpt.getMPTokenVersion(bob);
+
+            Account const bobNewKey("bobNewKey");
+            ct.mpt.generateKeyPair(bobNewKey);
+
+            auto const reEnc = reencryptHolderBalances(ct.mpt, bob, bob, bobNewKey);
+            BEAST_EXPECT(reEnc.has_value());
+            if (!reEnc)
+                return;
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+                .spendingCiphertext = reEnc->first,
+                .inboxCiphertext = reEnc->second,
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRotation,
+            });
+
+            auto const sleMptoken = env.le(keylet::mptoken(ct.mpt.issuanceID(), bob.id()));
+            if (!BEAST_EXPECT(sleMptoken))
+                return;
+
+            auto const newPubKey = ct.mpt.getPubKey(bobNewKey);
+            BEAST_EXPECT(
+                newPubKey && strHex((*sleMptoken)[sfHolderEncryptionKey]) == strHex(*newPubKey));
+            BEAST_EXPECT(!sleMptoken->isFieldPresent(sfRecoveryKey));
+            BEAST_EXPECT(ct.mpt.getMPTokenVersion(bob) == prevVersion + 1);
+
+            // The rotated balances must still decrypt to the same amounts,
+            // but now only under the NEW private key.
+            auto const spendingCt =
+                ct.mpt.getEncryptedBalance(bob, MPTTester::holderEncryptedSpending);
+            auto const inboxCt = ct.mpt.getEncryptedBalance(bob, MPTTester::holderEncryptedInbox);
+            BEAST_EXPECT(spendingCt.has_value());
+            BEAST_EXPECT(inboxCt.has_value());
+            if (!spendingCt || !inboxCt)
+                return;
+
+            auto const spendingAmt = ct.mpt.decryptAmount(bobNewKey, *spendingCt);
+            auto const inboxAmt = ct.mpt.decryptAmount(bobNewKey, *inboxCt);
+            BEAST_EXPECT(spendingAmt && *spendingAmt == 40);
+            BEAST_EXPECT(inboxAmt && *inboxAmt == 0);
+        }
+
+        // Rotation mode re-encrypts both balances correctly when spending and
+        // inbox are both non-zero and differ from each other.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            Account const carol("carol");
+            ConfidentialEnv ct{
+                env,
+                alice,
+                {{.account = bob, .payAmount = 100, .convertAmount = 40},
+                 {.account = carol, .payAmount = 100, .convertAmount = 50}}};
+
+            // carol sends 15 into bob's inbox, which is not merged into
+            // spending, leaving bob with spending=40, inbox=15.
+            ct.mpt.send({.account = carol, .dest = bob, .amt = 15});
+
+            Account const bobNewKey("bobNewKey");
+            ct.mpt.generateKeyPair(bobNewKey);
+
+            auto const reEnc = reencryptHolderBalances(ct.mpt, bob, bob, bobNewKey);
+            BEAST_EXPECT(reEnc.has_value());
+            if (!reEnc)
+                return;
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+                .spendingCiphertext = reEnc->first,
+                .inboxCiphertext = reEnc->second,
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRotation,
+            });
+
+            auto const spendingCt =
+                ct.mpt.getEncryptedBalance(bob, MPTTester::holderEncryptedSpending);
+            auto const inboxCt = ct.mpt.getEncryptedBalance(bob, MPTTester::holderEncryptedInbox);
+            BEAST_EXPECT(spendingCt.has_value());
+            BEAST_EXPECT(inboxCt.has_value());
+            if (!spendingCt || !inboxCt)
+                return;
+
+            auto const spendingAmt = ct.mpt.decryptAmount(bobNewKey, *spendingCt);
+            auto const inboxAmt = ct.mpt.decryptAmount(bobNewKey, *inboxCt);
+            BEAST_EXPECT(spendingAmt && *spendingAmt == 40);
+            BEAST_EXPECT(inboxAmt && *inboxAmt == 15);
+        }
+
+        // Recovery mode only records the pending recovery key; the current
+        // key, balances, and version are untouched.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+
+            auto const prevVersion = ct.mpt.getMPTokenVersion(bob);
+            auto const prevSpending =
+                ct.mpt.getDecryptedBalance(bob, MPTTester::holderEncryptedSpending);
+            auto const prevInbox = ct.mpt.getDecryptedBalance(bob, MPTTester::holderEncryptedInbox);
+            auto const prevKey = ct.mpt.getPubKey(bob);
+
+            Account const bobRecoveryKey("bobRecoveryKey");
+            ct.mpt.generateKeyPair(bobRecoveryKey);
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobRecoveryKey),
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+            });
+
+            auto const sleMptoken = env.le(keylet::mptoken(ct.mpt.issuanceID(), bob.id()));
+            if (!BEAST_EXPECT(sleMptoken))
+                return;
+
+            auto const recoveryKey = ct.mpt.getPubKey(bobRecoveryKey);
+            BEAST_EXPECT(
+                sleMptoken->isFieldPresent(sfRecoveryKey) && recoveryKey &&
+                strHex((*sleMptoken)[sfRecoveryKey]) == strHex(*recoveryKey));
+
+            BEAST_EXPECT(
+                prevKey && strHex((*sleMptoken)[sfHolderEncryptionKey]) == strHex(*prevKey));
+            BEAST_EXPECT(ct.mpt.getMPTokenVersion(bob) == prevVersion);
+            BEAST_EXPECT(
+                ct.mpt.getDecryptedBalance(bob, MPTTester::holderEncryptedSpending) ==
+                prevSpending);
+            BEAST_EXPECT(
+                ct.mpt.getDecryptedBalance(bob, MPTTester::holderEncryptedInbox) == prevInbox);
+        }
+
+        // Cancel mode clears the pending recovery key only; the current key,
+        // balances, and version are untouched.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+
+            Account const bobRecoveryKey("bobRecoveryKey");
+            ct.mpt.generateKeyPair(bobRecoveryKey);
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobRecoveryKey),
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+            });
+
+            auto const prevVersion = ct.mpt.getMPTokenVersion(bob);
+            auto const prevSpending =
+                ct.mpt.getDecryptedBalance(bob, MPTTester::holderEncryptedSpending);
+            auto const prevInbox = ct.mpt.getDecryptedBalance(bob, MPTTester::holderEncryptedInbox);
+            auto const prevKey = ct.mpt.getPubKey(bob);
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .flags = tfCancelRecovery,
+            });
+
+            auto const sleMptoken = env.le(keylet::mptoken(ct.mpt.issuanceID(), bob.id()));
+            if (!BEAST_EXPECT(sleMptoken))
+                return;
+
+            BEAST_EXPECT(!sleMptoken->isFieldPresent(sfRecoveryKey));
+            BEAST_EXPECT(
+                prevKey && strHex((*sleMptoken)[sfHolderEncryptionKey]) == strHex(*prevKey));
+            BEAST_EXPECT(ct.mpt.getMPTokenVersion(bob) == prevVersion);
+            BEAST_EXPECT(
+                ct.mpt.getDecryptedBalance(bob, MPTTester::holderEncryptedSpending) ==
+                prevSpending);
+            BEAST_EXPECT(
+                ct.mpt.getDecryptedBalance(bob, MPTTester::holderEncryptedInbox) == prevInbox);
+        }
+
+        // Rotation mode clears a pending recovery key.
+        {
+            Env env{*this, features};
+            Account const alice("alice");
+            Account const bob("bob");
+            ConfidentialEnv ct{
+                env, alice, {{.account = bob, .payAmount = 100, .convertAmount = 40}}};
+
+            Account const bobRecoveryKey("bobRecoveryKey");
+            ct.mpt.generateKeyPair(bobRecoveryKey);
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobRecoveryKey),
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRecovery,
+            });
+
+            {
+                auto const sleMptoken = env.le(keylet::mptoken(ct.mpt.issuanceID(), bob.id()));
+                if (!BEAST_EXPECT(sleMptoken))
+                    return;
+                BEAST_EXPECT(sleMptoken->isFieldPresent(sfRecoveryKey));
+            }
+
+            Account const bobNewKey("bobNewKey");
+            ct.mpt.generateKeyPair(bobNewKey);
+
+            auto const reEnc = reencryptHolderBalances(ct.mpt, bob, bob, bobNewKey);
+            BEAST_EXPECT(reEnc.has_value());
+            if (!reEnc)
+                return;
+
+            ct.mpt.holderKeyUpdate({
+                .account = bob,
+                .holderPubKey = ct.mpt.getPubKey(bobNewKey),
+                .spendingCiphertext = reEnc->first,
+                .inboxCiphertext = reEnc->second,
+                .proof = gMakeZeroBuffer(1),
+                .flags = tfHolderKeyRotation,
+            });
+
+            auto const sleMptoken = env.le(keylet::mptoken(ct.mpt.issuanceID(), bob.id()));
+            if (!BEAST_EXPECT(sleMptoken))
+                return;
+            BEAST_EXPECT(!sleMptoken->isFieldPresent(sfRecoveryKey));
+        }
+    }
+
 public:
     void
     testMPTokenIssuanceSetWithFeats(FeatureBitset features)
@@ -2490,6 +3189,12 @@ public:
         testConfidentialMPTMirrorUpdateDoApply(all);
         testConfidentialMPTMirrorUpdateMultipleRotationsIssuerMode(all);
         testConfidentialMPTMirrorUpdateMultipleRotationsHolderMode(all);
+
+        testConfidentialMPTHolderKeyUpdatePreflight(all);
+        testConfidentialMPTHolderKeyUpdatePreflight(all - featureConfidentialMPTKeyRotation);
+        testConfidentialMPTHolderKeyUpdatePreflight(all - featureConfidentialTransfer);
+        testConfidentialMPTHolderKeyUpdatePreclaim(all);
+        testConfidentialMPTHolderKeyUpdateDoApply(all);
     }
 };
 

src/test/app/ConfidentialTransferExtended_test.cpp

@@ -30,6 +30,7 @@
 
 #include <chrono>
 #include <cstdint>
+#include <optional>
 #include <string>
 #include <vector>
 
@@ -637,6 +638,104 @@ class ConfidentialTransferExtended_test : public ConfidentialTransferTestBase
         }
     }
 
+    // A full AMMWithdraw must succeed even when an unrelated third party
+    // holds a confidential balance. Pre-fixCleanup3_5_0 the erase of the
+    // AMM pseudo-account's MPToken was rejected in this case, permanently
+    // stranding the last LP's position.
+    void
+    testAMMWithdrawAllBlockedByUnrelatedCOA(FeatureBitset features)
+    {
+        testcase("Full AMMWithdraw with an unrelated holder's COA");
+        using namespace test::jtx;
+
+        Account const alice("alice");
+        Account const bob("bob");
+        Account const carol("carol");
+
+        for (bool const withFix : {true, false})
+        {
+            for (bool const carolConverts : {false, true})
+            {
+                Env env{*this, withFix ? features | fixCleanup3_5_0 : features - fixCleanup3_5_0};
+
+                MPTTester mptAlice(env, alice, {.holders = {bob, carol}});
+                mptAlice.create({.flags = kMptDexFlags | tfMPTCanHoldConfidentialBalance});
+                mptAlice.authorize({.account = bob});
+                mptAlice.authorize({.account = carol});
+                mptAlice.pay(alice, bob, 1'000);
+                mptAlice.pay(alice, carol, 100);
+
+                mptAlice.generateKeyPair(alice);
+                mptAlice.set({.account = alice, .issuerPubKey = mptAlice.getPubKey(alice)});
+
+                // bob is the sole LP, so withdrawing all of his LPTokens zeroes
+                // LPTokenBalance and deletes the AMM in that same transaction.
+                AMM amm(env, bob, XRP(100), mptAlice(100));
+                Account const ammHolder("amm", amm.ammAccount());
+                BEAST_EXPECT(amm.ammExists());
+                BEAST_EXPECT(mptAlice.getBalance(ammHolder) == 100);
+
+                // The AMM pseudo-account cannot initialize confidential state:
+                // confidential transactions must be signed by sfAccount and it
+                // has no signing key.
+                BEAST_EXPECT(
+                    !mptAlice.getEncryptedBalance(ammHolder, MPTTester::holderEncryptedInbox));
+                BEAST_EXPECT(
+                    !mptAlice.getEncryptedBalance(ammHolder, MPTTester::holderEncryptedSpending));
+                BEAST_EXPECT(
+                    !mptAlice.getEncryptedBalance(ammHolder, MPTTester::issuerEncryptedBalance));
+                BEAST_EXPECT(
+                    !mptAlice.getEncryptedBalance(ammHolder, MPTTester::auditorEncryptedBalance));
+
+                if (carolConverts)
+                {
+                    mptAlice.generateKeyPair(carol);
+                    mptAlice.convert(
+                        {.account = carol, .amt = 1, .holderPubKey = mptAlice.getPubKey(carol)});
+                }
+
+                BEAST_EXPECT(mptAlice.getIssuanceConfidentialBalance() == (carolConverts ? 1 : 0));
+
+                if (carolConverts && !withFix)
+                {
+                    amm.withdrawAll(bob, std::nullopt, Ter(tecINVARIANT_FAILED));
+                    env.close();
+
+                    // bob cannot close his position: the pool, his LPTokens and
+                    // the AMM object all survive the failed withdrawal.
+                    BEAST_EXPECT(amm.ammExists());
+                    BEAST_EXPECT(mptAlice.getBalance(ammHolder) == 100);
+
+                    // A partial withdrawal still succeeds, because it never
+                    // erases the MPToken -- bob can drain the pool down to a
+                    // residual amount but can never close his position. Withdraw
+                    // half of his actual LPToken balance; a fixed token count
+                    // would round the MPT side of the pool to zero and be
+                    // rejected as a one-sided withdrawal.
+                    auto const bobLPTokens = amm.getLPTokensBalance(bob.id());
+                    amm.withdraw(
+                        bob, IOUAmount{bobLPTokens.mantissa() / 2, bobLPTokens.exponent()});
+                    env.close();
+                    BEAST_EXPECT(amm.ammExists());
+                    BEAST_EXPECT(mptAlice.getBalance(ammHolder) > 0);
+                }
+                else
+                {
+                    // With the fix, carol's confidential balance is irrelevant to
+                    // an AMM she has no stake in: bob closes his position and the
+                    // AMM and its MPToken are erased.
+                    amm.withdrawAll(bob);
+                    env.close();
+
+                    BEAST_EXPECT(!amm.ammExists());
+                    BEAST_EXPECT(
+                        env.le(keylet::mptoken(mptAlice.issuanceID(), amm.ammAccount())) ==
+                        nullptr);
+                }
+            }
+        }
+    }
+
     // Exercises every Confidential Transfer transaction type (MPTokenIssuanceSet,
     // Convert, MergeInbox, Send, ConvertBack) using tickets instead of regular account
     // sequence numbers.
@@ -2561,6 +2660,7 @@ class ConfidentialTransferExtended_test : public ConfidentialTransferTestBase
 
         // AMM/pseudo-account interaction.
         testAMMHolderCannotHaveConfidentialStateClawback(features);
+        testAMMWithdrawAllBlockedByUnrelatedCOA(features);
 
         // Ticket interactions.
         testWithTickets(features);

src/test/app/ConfidentialTransfer_test.cpp

@@ -1745,7 +1745,8 @@ class ConfidentialTransfer_test : public ConfidentialTransferTestBase
                 (*sle)[sfConfidentialBalanceVersion] = wrappedFrom;
                 view.rawReplace(sle);
 
-                auto const result = xrpl::apply(env.app(), view, *jt.stx, TapNone, env.journal);
+                auto const result =
+                    xrpl::apply(env.app(), view, *jt.stx, ApplyFlags::None, env.journal);
                 BEAST_EXPECT(result.ter == tesSUCCESS);
                 return result.applied;
             }));

src/test/app/Credentials_test.cpp

@@ -901,8 +901,7 @@ struct Credentials_test : public beast::unit_test::Suite
 
             {
                 testcase("deleteSLE fail, bad SLE.");
-                auto view =
-                    std::make_shared<ApplyViewImpl>(env.current().get(), ApplyFlags::TapNone);
+                auto view = std::make_shared<ApplyViewImpl>(env.current().get(), ApplyFlags::None);
                 auto ter = xrpl::credentials::deleteSLE(*view, {}, env.journal);
                 BEAST_EXPECT(ter == tecNO_ENTRY);
             }
@@ -1125,7 +1124,7 @@ struct Credentials_test : public beast::unit_test::Suite
         // Create an ApplyViewImpl on top of the current closed ledger
         // and corrupt it by erasing the issuer's account SLE
         auto const open = env.current();
-        ApplyViewImpl av(&*open, TapNone);
+        ApplyViewImpl av(&*open, ApplyFlags::None);
 
         // Erase the issuer's account to simulate ledger corruption
         auto sleIssuer = av.peek(keylet::account(issuer.id()));

src/test/app/EscrowToken_test.cpp

@@ -573,8 +573,8 @@ struct EscrowToken_test : public beast::unit_test::Suite
             env(pay(gw, bob, usd(1)));
             env.close();
 
-            bool const largeMantissa =
-                features[featureSingleAssetVault] || features[featureLendingProtocol];
+            bool const largeMantissa = features[featureSingleAssetVault] ||
+                features[featureLendingProtocol] || features[featureMPTokensV2];
 
             // alice cannot create escrow for 1/10 iou - precision loss
             env(escrow::create(alice, bob, usd(1)),
@@ -2294,8 +2294,8 @@ struct EscrowToken_test : public beast::unit_test::Suite
             env(pay(gw, bob, usd(1)));
             env.close();
 
-            bool const largeMantissa =
-                features[featureSingleAssetVault] || features[featureLendingProtocol];
+            bool const largeMantissa = features[featureSingleAssetVault] ||
+                features[featureLendingProtocol] || features[featureMPTokensV2];
 
             // alice cannot create escrow for 1/10 iou - precision loss
             env(escrow::create(alice, bob, usd(1)),
@@ -2795,7 +2795,7 @@ struct EscrowToken_test : public beast::unit_test::Suite
 
             auto const seq1 = env.seq(alice);
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 auto sleNew =
                     std::make_shared<SLE>(keylet::escrow(alice, SeqProxy::rawSequence(seq1)));
                 MPTIssue const mpt{MPTIssue{makeMptID(1, AccountID(0x4985601))}};
@@ -3023,7 +3023,7 @@ struct EscrowToken_test : public beast::unit_test::Suite
 
             auto const seq1 = env.seq(alice);
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 auto sleNew =
                     std::make_shared<SLE>(keylet::escrow(alice, SeqProxy::rawSequence(seq1)));
                 MPTIssue const mpt{MPTIssue{makeMptID(1, AccountID(0x4985601))}};
@@ -4334,7 +4334,7 @@ public:
         using namespace test::jtx;
         FeatureBitset const all{testableAmendments()};
         for (FeatureBitset const& feats :
-             {all - featureSingleAssetVault - featureLendingProtocol, all})
+             {all - featureSingleAssetVault - featureLendingProtocol - featureMPTokensV2, all})
         {
             testIOUWithFeats(feats);
             testIOUWithFeats(feats - fixCleanup3_2_0);

src/test/app/Escrow_test.cpp

@@ -1302,8 +1302,8 @@ struct Escrow_test : public beast::unit_test::Suite
                 escrow::kFinishTime(env.now() + 1s),
                 Seq(1),
                 Fee(baseFee));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jtx.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jtx.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(baseFee));
@@ -1312,8 +1312,8 @@ struct Escrow_test : public beast::unit_test::Suite
 
         {
             auto const jtx = env.jt(escrow::cancel("bob", "alice", 3), Seq(1), Fee(baseFee));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jtx.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jtx.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(baseFee));
@@ -1322,8 +1322,8 @@ struct Escrow_test : public beast::unit_test::Suite
 
         {
             auto const jtx = env.jt(escrow::finish("bob", "alice", 3), Seq(1), Fee(baseFee));
-            auto const pf =
-                preflight(env.app(), env.current()->rules(), *jtx.stx, TapNone, env.journal);
+            auto const pf = preflight(
+                env.app(), env.current()->rules(), *jtx.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(pf.ter));
             BEAST_EXPECT(!pf.consequences.isBlocker());
             BEAST_EXPECT(pf.consequences.fee() == drops(baseFee));

src/test/app/FeeVote_test.cpp

@@ -134,7 +134,7 @@ createInvalidFeeTx(
 bool
 applyFeeAndTestResult(jtx::Env& env, OpenView& view, STTx const& tx)
 {
-    auto const res = apply(env.app(), view, tx, ApplyFlags::TapNone, env.journal);
+    auto const res = apply(env.app(), view, tx, ApplyFlags::None, env.journal);
     return isTesSuccess(res.ter);
 }
 

src/test/app/FlowMPT_test.cpp

@@ -333,7 +333,7 @@ struct FlowMPT_test : public beast::unit_test::Suite
                 auto const flowResult = [&] {
                     STAmount const deliver(usd(5'100));
                     STAmount smax(btc(61));
-                    PaymentSandbox sb(env.current().get(), TapNone);
+                    PaymentSandbox sb(env.current().get(), ApplyFlags::None);
                     STPathSet paths;
                     auto ipe = [](Asset const& asset) {
                         return STPathElement(
@@ -371,7 +371,7 @@ struct FlowMPT_test : public beast::unit_test::Suite
                 env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
                     if (flowResult.removableOffers.empty())
                         return false;
-                    Sandbox sb(&view, TapNone);
+                    Sandbox sb(&view, ApplyFlags::None);
                     for (auto const& o : flowResult.removableOffers)
                     {
                         if (auto ok = sb.peek(keylet::offer(o)))

src/test/app/Flow_test.cpp

@@ -476,7 +476,7 @@ struct Flow_test : public beast::unit_test::Suite
             auto const flowResult = [&] {
                 STAmount const deliver(usd(51));
                 STAmount smax(btc(61));
-                PaymentSandbox sb(env.current().get(), TapNone);
+                PaymentSandbox sb(env.current().get(), ApplyFlags::None);
                 STPathSet paths;
                 auto ipe = [](Issue const& iss) {
                     return STPathElement(
@@ -514,7 +514,7 @@ struct Flow_test : public beast::unit_test::Suite
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
                 if (flowResult.removableOffers.empty())
                     return false;
-                Sandbox sb(&view, TapNone);
+                Sandbox sb(&view, ApplyFlags::None);
                 for (auto const& o : flowResult.removableOffers)
                 {
                     if (auto ok = sb.peek(keylet::offer(o)))

src/test/app/LedgerHistory_test.cpp

@@ -59,7 +59,7 @@ public:
         if (stx)
         {
             OpenView accum(&*res);
-            applyTransaction(env.app(), accum, *stx, false, TapNone, env.journal);
+            applyTransaction(env.app(), accum, *stx, false, ApplyFlags::None, env.journal);
             accum.apply(*res);
         }
         res->updateSkipList();

src/test/app/LedgerReplay_test.cpp

@@ -90,7 +90,7 @@ struct LedgerReplay_test : public beast::unit_test::Suite
         auto const lastClosedParent = ledgerMaster.getLedgerByHash(lastClosed->header().parentHash);
 
         auto const replayed = buildLedger(
-            LedgerReplay(lastClosedParent, lastClosed), TapNone, env.app(), env.journal);
+            LedgerReplay(lastClosedParent, lastClosed), ApplyFlags::None, env.app(), env.journal);
 
         BEAST_EXPECT(replayed->header().hash == lastClosed->header().hash);
     }
@@ -122,7 +122,7 @@ struct LedgerReplay_test : public beast::unit_test::Suite
         auto const lastClosedParent = ledgerMaster.getLedgerByHash(lastClosed->header().parentHash);
 
         auto const replayed = buildLedger(
-            LedgerReplay(lastClosedParent, lastClosed), TapNone, env.app(), env.journal);
+            LedgerReplay(lastClosedParent, lastClosed), ApplyFlags::None, env.app(), env.journal);
 
         BEAST_EXPECT(replayed->header().hash == lastClosed->header().hash);
     }

src/test/app/MPToken_test.cpp

@@ -4059,7 +4059,7 @@ class MPToken_test : public beast::unit_test::Suite
                                  TER expectedTer,
                                  std::optional<std::uint64_t> expectedOutstanding,
                                  std::string const& label) {
-            ApplyViewImpl av(&*env.current(), TapNone);
+            ApplyViewImpl av(&*env.current(), ApplyFlags::None);
             auto const ter =
                 accountSendMulti(av, issuer.id(), asset, receivers, env.app().getJournal("View"));
             BEAST_EXPECTS(ter == expectedTer, label);

src/test/app/NFTokenBurn_test.cpp

@@ -776,7 +776,13 @@ class NFTokenBurn_test : public beast::unit_test::Suite
                 test::StreamSink sink{beast::Severity::Warning};
                 beast::Journal const jlog{sink};
                 ApplyContext ac{
-                    env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                    env.app(),
+                    ov,
+                    tx,
+                    tesSUCCESS,
+                    env.current()->fees().base,
+                    ApplyFlags::None,
+                    jlog};
 
                 // Verify that the last page is present and contains one NFT.
                 auto lastNFTokenPage = ac.view().peek(keylet::nftokenPageMax(alice));
@@ -808,7 +814,13 @@ class NFTokenBurn_test : public beast::unit_test::Suite
                 test::StreamSink sink{beast::Severity::Warning};
                 beast::Journal const jlog{sink};
                 ApplyContext ac{
-                    env.app(), ov, tx, tesSUCCESS, env.current()->fees().base, TapNone, jlog};
+                    env.app(),
+                    ov,
+                    tx,
+                    tesSUCCESS,
+                    env.current()->fees().base,
+                    ApplyFlags::None,
+                    jlog};
 
                 // Verify that the middle  page is present.
                 auto lastNFTokenPage = ac.view().peek(keylet::nftokenPageMax(alice));

src/test/app/PayChan_test.cpp

@@ -1404,6 +1404,30 @@ struct PayChan_test : public beast::unit_test::Suite
                 rv = env.rpc("channel_authorize", "alice", chan1StrBad, "1000");
                 BEAST_EXPECT(rv[jss::error] == "channelMalformed");
             }
+            {
+                // channel_id is not a string.
+                json::Value args{json::ValueType::Object};
+                args[jss::amount] = "2000";
+                args[jss::channel_id] = 2000;
+                args[jss::key_type] = "secp256k1";
+                args[jss::passphrase] = "passphrase_can_be_anything";
+
+                auto const ra =
+                    env.rpc("json", "channel_authorize", args.toStyledString())[jss::result];
+                BEAST_EXPECT(ra[jss::error] == "invalidParams");
+            }
+            {
+                // channel_id is not a string.
+                json::Value args{json::ValueType::Object};
+                args[jss::public_key] = chan1PkStr;
+                args[jss::channel_id] = 2000;
+                args[jss::amount] = "1000";
+                args[jss::signature] = sig;
+
+                auto const rv =
+                    env.rpc("json", "channel_verify", args.toStyledString())[jss::result];
+                BEAST_EXPECT(rv[jss::error] == "invalidParams");
+            }
             {
                 // give an ill formed base 58 public key
                 auto illFormedPk = chan1PkStr.substr(0, chan1PkStr.size() - 1);

src/test/app/PayStrandMPT_test.cpp

@@ -572,7 +572,7 @@ struct PayStrandMPT_test : public beast::unit_test::Suite
         inputs.defaultPathsAllowed = true;
         try
         {
-            PaymentSandbox sb{env.current().get(), TapNone};
+            PaymentSandbox sb{env.current().get(), ApplyFlags::None};
             {
                 auto const r = ::xrpl::path::RippleCalc::rippleCalculate(
                     sb,

src/test/app/PayStrand_test.cpp

@@ -768,7 +768,8 @@ struct PayStrand_test : public beast::unit_test::Suite
                 env,
                 usd,
                 std::nullopt,
-                STPath({STPathElement(0, xrpAccount(), xrpCurrency(), xrpAccount())}),
+                STPath({STPathElement(
+                    STPathElement::Type::TypeNone, xrpAccount(), xrpCurrency(), xrpAccount())}),
                 temBAD_PATH);
 
             // The same account can't appear more than once on a path
@@ -1076,7 +1077,7 @@ struct PayStrand_test : public beast::unit_test::Suite
         inputs.defaultPathsAllowed = true;
         try
         {
-            PaymentSandbox sb{env.current().get(), TapNone};
+            PaymentSandbox sb{env.current().get(), ApplyFlags::None};
             {
                 auto const r = ::xrpl::path::RippleCalc::rippleCalculate(
                     sb,

src/test/app/PseudoTx_test.cpp

@@ -82,7 +82,7 @@ struct PseudoTx_test : public beast::unit_test::Suite
             BEAST_EXPECT(!passesLocalChecks(stx, reason));
             BEAST_EXPECT(reason == "Cannot submit pseudo transactions.");
             env.app().getOpenLedger().modify([&](OpenView& view, beast::Journal j) {
-                auto const result = xrpl::apply(env.app(), view, stx, TapNone, j);
+                auto const result = xrpl::apply(env.app(), view, stx, ApplyFlags::None, j);
                 BEAST_EXPECT(!result.applied && result.ter == temINVALID);
                 return result.applied;
             });

src/test/app/Regression_test.cpp

@@ -103,7 +103,8 @@ struct Regression_test : public beast::unit_test::Suite
             auto const jt = env.jt(pay(env.master, "alice", aliceAmount));
             OpenView accum(&*next);
 
-            auto const result = xrpl::apply(env.app(), accum, *jt.stx, TapNone, env.journal);
+            auto const result =
+                xrpl::apply(env.app(), accum, *jt.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(isTesSuccess(result.ter));
             BEAST_EXPECT(result.applied);
 
@@ -126,7 +127,8 @@ struct Regression_test : public beast::unit_test::Suite
 
             OpenView accum(&*next);
 
-            auto const result = xrpl::apply(env.app(), accum, *jt.stx, TapNone, env.journal);
+            auto const result =
+                xrpl::apply(env.app(), accum, *jt.stx, ApplyFlags::None, env.journal);
             BEAST_EXPECT(result.ter == tecINSUFF_FEE);
             BEAST_EXPECT(result.applied);
 
@@ -303,12 +305,11 @@ struct Regression_test : public beast::unit_test::Suite
                 return digest.asUInt256();
             }();
 
-            auto const mapCounts = [&](CountedObjects::List const& list) {
-                std::map<std::string, int> result;
-                for (auto const& e : list)
-                {
-                    result[e.first] = e.second;
-                }
+            auto const mapCounts = [] {
+                std::map<std::string, std::uint32_t> result;
+
+                for (auto const& c : gCountedObjects)
+                    result.emplace(c.name(), c.count());
 
                 return result;
             };
@@ -317,11 +318,11 @@ struct Regression_test : public beast::unit_test::Suite
             {
                 auto& cache = env.app().getCachedSLEs();
                 cache.del(*digest, false);  // NOLINT(bugprone-unchecked-optional-access)
-                auto const beforeCounts = mapCounts(CountedObjects::getInstance().getCounts(0));
+                auto const beforeCounts = mapCounts();
 
                 env(check::cash(alice, bobIndex, check::DeliverMin(XRP(100))), Ter(tecNO_ENTRY));
 
-                auto const afterCounts = mapCounts(CountedObjects::getInstance().getCounts(0));
+                auto const afterCounts = mapCounts();
 
                 using namespace std::string_literals;
                 BEAST_EXPECT(