May 2026

The Linux-only test failure

(electrum__blockchain_outpoint_subscribe__two_spenders__one_notification) demonstrates that this ordering is not observed on Ubuntu 24.04 with the Boost.Asio version used in the CI jobs, even though the same code path produces the expected ordering on Windows and macOS. This can only be explained as a platform-specific behavioral difference (or bug) in Boost.Asio's epoll-based reactor and thread-pool executor implementation on Linux.
The isolated cause of the test failures is therefore the reliance, in the two-spender notification path of complete_outpoint_subscribe, on an ordering guarantee that Boost.Asio's Linux implementation does not reliably provide in this configuration.

/// Reporting events.
enum events : uint8_t
{
    /// Candidate chain.
    header_archived,     // header checked, accepted
    header_organized,    // header pushed (previously archived)
    header_reorganized,  // header popped

    /// Blocks.
    block_archived,      // block checked
    block_buffered,      // block buffered for validation
    block_validated,     // block checked, accepted, connected
    block_confirmed,     // block checked, accepted, connected, confirmable
    block_unconfirmable, // block invalid (after headers-first archive)
    validate_bypassed,   // block checked, accepted [assumed]
    confirm_bypassed,    // block checked, accepted, connected [assumed]

    /// Transactions.
    tx_archived,         // unassociated tx checked, accepted, connected
    tx_validated,        // associated tx checked, accepted, connected
    tx_invalidated,      // associated tx invalid (after headers-first archive)

    /// Confirmed chain.
    block_organized,     // block pushed (previously confirmable)
    block_reorganized,   // block popped

    /// Mining.
    template_issued,      // block template issued for mining

    /// Timespans.
    snapshot_secs,        // snapshot timespan in seconds.
    prune_msecs,          // prune timespan in milliseconds.
    reload_msecs,         // store reload timespan in milliseconds.
    block_usecs,          // getblock timespan in microseconds.
    ancestry_msecs,       // getancestry timespan in milliseconds.
    filter_msecs,         // getfilter timespan in milliseconds.
    filterhashes_msecs,   // getfilterhashes timespan in milliseconds.
    filterchecks_msecs    // getcfcheckpt timespan in milliseconds.
};

method<"top_subscribe", uint8_t, uint8_t>{ "version", "media" },

method<"block_subscribe", uint8_t, uint8_t>{ "version", "media" },
method<"tx_subscribe", uint8_t, uint8_t>{ "version", "media" },
method<"input_subscribe", uint8_t, uint8_t, system::hash_cptr, uint32_t>{ "version", "media", "hash", "index" },
method<"output_subscribe", uint8_t, uint8_t, system::hash_cptr, uint32_t>{ "version", "media", "hash", "index" },
method<"address_subscribe", uint8_t, uint8_t, system::hash_cptr, uint32_t>{ "version", "media", "hash", "turbo" },

method<"log_subscribe", uint8_t, uint8_t>{ "version", "media" },
method<"event_subscribe", uint8_t, uint8_t>{ "version", "media" }

phillip@vali:~/code/libbitcoin/libbitcoin-build$ ~/test/cmake/prefix/bin/bs --version
Version Information...
libbitcoin-server:     4.0.2099
libbitcoin-node:       4.0.3592
libbitcoin-network:    4.0.6683
libbitcoin-database:   4.0.3839
libbitcoin-system:     4.0.9128

/v1/top/subscribe
/v1/block/subscribe
/v1/tx/subscribe

/v1/address/[scripthash]/subscribe
/v1/output/[txhash]/[index]/subscribe

/v1/top/subscribe?format=json&stop=false

#include <iostream>
#include <bitcoin/system.hpp>
using namespace std;

int main()
{
    cout << "Hello, world, from Microsoft C++!" << endl;
}

REM ============================================================================
set include=C:\Users\tanan\source\repos\libbitcoin-server\include;%include%
set lib=C:\Users\tanan\source\repos\libbitcoin-server\bin\x64\Debug\v143\static;%lib%

set include=C:\Users\tanan\source\repos\libbitcoin-node\include;%include%
set lib=C:\Users\tanan\source\repos\libbitcoin-node\bin\x64\Debug\v143\static;%lib%

set include=C:\Users\tanan\source\repos\libbitcoin-network\include;%include%
set lib=C:\Users\tanan\source\repos\libbitcoin-network\bin\x64\Debug\v143\static;%lib%

set include=C:\Users\tanan\source\repos\libbitcoin-database\include;%include%
set lib=C:\Users\tanan\source\repos\libbitcoin-database\bin\x64\Debug\v143\static;%lib%

set include=C:\Users\tanan\source\repos\libbitcoin-system\include;%include%
set lib=C:\Users\tanan\source\repos\libbitcoin-system\bin\x64\Debug\v143\static;%lib%
REM ============================================================================


REM ============================================================================
set include=C:\Users\tanan\source\repos\.nuget\packages\secp256k1_vc143.0.6.1\build\native\include;%include%
set lib=C:\Users\tanan\source\repos\.nuget\packages\secp256k1_vc143.0.6.1\build\native\bin;%lib%

set include=C:\Users\tanan\source\repos\.nuget\packages\boost.1.86.0\lib\native\include;%include%
set lib=C:\Users\tanan\source\repos\.nuget\packages\boost_iostreams-vc143.1.86.0\lib\native;%lib%
set lib=C:\Users\tanan\source\repos\.nuget\packages\boost_locale-vc143.1.86.0\lib\native;%lib%
set lib=C:\Users\tanan\source\repos\.nuget\packages\boost_program_options-vc143.1.86.0\lib\native;%lib%
set lib=C:\Users\tanan\source\repos\.nuget\packages\boost_thread-vc143.1.86.0\lib\native;%lib%
set lib=C:\Users\tanan\source\repos\.nuget\packages\boost_unit_test_framework-vc143.1.86.0\lib\native;%lib%
set lib=C:\Users\tanan\source\repos\.nuget\packages\boost_url-vc143.1.86.0\lib\native;%lib%
REM ============================================================================

C:\Users\tanan\code\libbitcoin-example>cl /EHsc hello.cpp

Compilateur d'optimisation Microsoft (R) C/C++ version 19.44.35227 pour x64
Copyright (C) Microsoft Corporation. Tous droits réservés.

hello.cpp
C:\Users\tanan\source\repos\libbitcoin-system\include\bitcoin/system/preprocessor.hpp(185): error C2338: static_assert failed: 'C++20 minimum required.'
Please define _WIN32_WINNT or _WIN32_WINDOWS appropriately. For example:
- add -D_WIN32_WINNT=0x0601 to the compiler command line; or
- add _WIN32_WINNT=0x0601 to your project's Preprocessor Definitions.
Assuming _WIN32_WINNT=0x0601 (i.e. Windows 7 target).
C:\Program Files\Microsoft Visual Studio\18\Community\VC\Tools\MSVC\14.44.35207\include\bit(11): warning STL4038: The contents of <bit> are available only with C++20 or later.
C:\Program Files\Microsoft Visual Studio\18\Community\VC\Tools\MSVC\14.44.35207\include\variant(12): warning STL4038: The contents of <variant> are available only with C++17 or later.
C:\Users\tanan\source\repos\libbitcoin-system\include\bitcoin/system/types.hpp(189): error C3646: 'data_t' : spécificateur de substitution inconnu
C:\Users\tanan\source\repos\libbitcoin-system\include\bitcoin/system/types.hpp(189): note: le contexte d'instanciation du modèle (le plus ancien) est
C:\Users\tanan\source\repos\libbitcoin-system\include\bitcoin/system/types.hpp(186): note: lors de la compilation du modèle de classe 'libbitcoin::data_t'
C:\Users\tanan\source\repos\libbitcoin-system\include\bitcoin/system/types.hpp(189): error C2059: erreur de syntaxe : '('
C:\Users\tanan\source\repos\libbitcoin-system\include\bitcoin/system/types.hpp(190): error C2334: jetons inattendus avant ':' ; corps apparent de la fonction ignoré
C:\Users\tanan\source\repos\libbitcoin-system\include\bitcoin/system/types.hpp(27): fatal error C1075: '{' : jeton correspondant introuvable

C:\Users\tanan\code\libbitcoin-example>cl /EHsc /std:c++20 hello.cpp
Compilateur d'optimisation Microsoft (R) C/C++ version 19.44.35227 pour x64
Copyright (C) Microsoft Corporation. Tous droits réservés.

hello.cpp
C:\Users\tanan\source\repos\libbitcoin-system\include\bitcoin/system/preprocessor.hpp(185): error C2338: static_assert failed: 'C++20 minimum required.'
Please define _WIN32_WINNT or _WIN32_WINDOWS appropriately. For example:
- add -D_WIN32_WINNT=0x0601 to the compiler command line; or
- add _WIN32_WINNT=0x0601 to your project's Preprocessor Definitions.
Assuming _WIN32_WINNT=0x0601 (i.e. Windows 7 target).

#if __cplusplus >= 202002L
    #define HAVE_CPP20
#endif

#if !defined(HAVE_CPP20)
    static_assert(false, "C++20 minimum required.");
#endif

/// Serves only the last 288 (2 day) blocks.
node_network_limited = system::bit_right<uint64_t>(10),