diff --git a/.gitignore b/.gitignore
index a1f912b77..d1b7becb9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -59,3 +59,47 @@ aclocal.m4
 .deps
 /*.exe
 *.dSYM/
+
+# --- Added for CMake, MSVC, vcpkg, and Python workflows ---
+
+# CMake & vcpkg
+/build-*/
+/out/
+/bin/
+CMakeCache.txt
+CMakeFiles/
+CMakeUserPresets.json
+vcpkg_installed/
+.vcpkg/
+vcpkg-manifest-install.log
+
+# Visual Studio & Windows artifacts
+.vs/
+*.sln
+*.suo
+*.user
+*.vcxproj
+*.vcxproj.filters
+*.vcxproj.user
+*.obj
+*.lib
+*.exp
+*.pdb
+*.ilk
+*.dll
+*.idb
+*.manifest
+
+# Python
+__pycache__/
+*.py[cod]
+*.class
+.pytest_cache/
+.venv/
+venv/
+
+# Scratch & Temporary
+test_*.c
+test_*.py
+child_*.txt
+*.i
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 000000000..024cf652c
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,190 @@
+cmake_minimum_required(VERSION 3.15)
+project(rsync C CXX)
+
+# Find dependencies
+find_package(ZLIB QUIET)
+if(NOT ZLIB_FOUND)
+    message(STATUS 'ZLIB not found in environment, fetching via FetchContent')
+    include(FetchContent)
+    FetchContent_Declare(
+        zlib
+        GIT_REPOSITORY https://github.com/madler/zlib.git
+        GIT_TAG v1.3.1
+    )
+    FetchContent_MakeAvailable(zlib)
+    if(NOT TARGET ZLIB::ZLIB)
+        add_library(ZLIB::ZLIB ALIAS zlibstatic)
+    endif()
+endif()
+find_package(zstd CONFIG REQUIRED)
+find_package(lz4 CONFIG REQUIRED)
+find_package(xxHash CONFIG REQUIRED)
+find_package(OpenSSL REQUIRED)
+
+find_path(POPT_INCLUDE_DIR NAMES popt.h)
+find_library(POPT_LIBRARY NAMES popt)
+
+# Source files
+set(RSYNC_SOURCES
+    flist.c rsync.c generator.c receiver.c cleanup.c sender.c exclude.c
+    util1.c util2.c main.c checksum.c match.c syscall.c log.c backup.c delete.c
+    options.c io.c compat.c hlink.c token.c uidlist.c socket.c hashtable.c
+    usage.c fileio.c batch.c clientname.c chmod.c acls.c xattrs.c
+    progress.c pipe.c
+    params.c loadparm.c clientserver.c access.c connection.c authenticate.c
+    lib/wildmatch.c lib/compat.c lib/snprintf.c lib/mdfour.c lib/md5.c
+    lib/permstring.c lib/pool_alloc.c lib/sysacls.c lib/sysxattrs.c
+)
+
+# Placeholder config.h to avoid compiler errors on Windows where configure wasn't run
+set(HAVE_CONFIG_H 1)
+set(RSYNC_VERSION "3.3.0")
+set(HAVE_ZLIB 1)
+set(HAVE_OPENSSL 1)
+set(HAVE_STRERROR 1)
+set(PACKAGE "rsync")
+set(POPT_SYSCONFDIR "/etc")
+
+set(SIZEOF_INT 4)
+set(SIZEOF_LONG 4)
+set(SIZEOF_SHORT 2)
+set(SIZEOF_INT32_T 4)
+set(SIZEOF_UINT32_T 4)
+set(SIZEOF_INT64_T 8)
+set(SIZEOF_UINT64_T 8)
+set(SIZEOF_OFF_T 4)
+set(SIZEOF_TIME_T 8)
+set(SIZEOF_CHARP 8)
+
+set(HAVE_SIZE_T 1)
+set(HAVE_OFF_T 1)
+set(HAVE_TIME_T 1)
+set(HAVE_PID_T 1)
+set(HAVE_DIRENT_H 1)
+set(HAVE_UTIME 1)
+set(HAVE_UTIMES 1)
+set(HAVE_STRPBRK 1)
+set(HAVE_GETCWD 1)
+
+set(HAVE_STRUCT_ADDRINFO 1)
+set(HAVE_STRUCT_SOCKADDR_STORAGE 1)
+set(HAVE_GETADDRINFO 1)
+set(HAVE_GETNAMEINFO 1)
+set(HAVE_SOCKADDR_IN6 1)
+set(HAVE_MEMMOVE 1)
+set(HAVE_GETTIMEOFDAY_TZ 1)
+set(HAVE_READLINK 1)
+
+set(SIGUSR1 10)
+set(SIGUSR2 12)
+set(SIGHUP 1)
+set(SIGALRM 14)
+set(WNOHANG 1)
+set(O_NOFOLLOW 0)
+set(O_DIRECTORY 0)
+set(AT_REMOVEDIR 0x200)
+
+set(RSYNC_RSH "ssh")
+set(NOBODY_USER "nobody")
+set(NOBODY_GROUP "nobody")
+set(RSYNCD_SYSCONF "/etc/rsyncd.conf")
+
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/config.h.in ${CMAKE_CURRENT_BINARY_DIR}/config.h)
+
+# Use the pre-generated headers that are committed to the repo
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/proto.h ${CMAKE_CURRENT_BINARY_DIR}/proto.h COPYONLY)
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/daemon-parm.h ${CMAKE_CURRENT_BINARY_DIR}/daemon-parm.h COPYONLY)
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/help-rsync.h ${CMAKE_CURRENT_BINARY_DIR}/help-rsync.h COPYONLY)
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/help-rsyncd.h ${CMAKE_CURRENT_BINARY_DIR}/help-rsyncd.h COPYONLY)
+
+file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/default-cvsignore.h "#define DEFAULT_CVSIGNORE \".svn .git .hg .bzr .cvs\"\n")
+file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/default-dont-compress.h "#define DEFAULT_DONT_COMPRESS \"*.gz *.zip *.z *.rpm *.deb *.iso *.bz2 *.tgz *.tbz *.rar *.jar *.pdf *.7z *.xz *.lzma\"\n")
+
+add_executable(rsync ${RSYNC_SOURCES})
+
+# Target include directories
+get_filename_component(AUTO_WIN_MSVC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../auto-win-msvc" ABSOLUTE)
+file(GLOB POSIX_INCLUDES "${AUTO_WIN_MSVC_DIR}/posix-*/include")
+file(GLOB LINUX_INCLUDES "${AUTO_WIN_MSVC_DIR}/linux-*/include")
+file(GLOB POSIX_SOURCES "${AUTO_WIN_MSVC_DIR}/posix-*/src/*.c")
+target_include_directories(rsync PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/lib ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+add_library(posix_shims STATIC ${POSIX_SOURCES})
+target_include_directories(posix_shims PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+# Link libraries
+target_link_libraries(rsync PRIVATE
+    posix_shims
+    ws2_32
+    netapi32
+    ZLIB::ZLIB
+    zstd::libzstd
+    lz4::lz4
+    xxHash::xxhash
+    OpenSSL::Crypto
+    OpenSSL::SSL
+)
+
+if(POPT_INCLUDE_DIR AND POPT_LIBRARY)
+    target_link_libraries(rsync PRIVATE ${POPT_LIBRARY})
+    target_include_directories(rsync PRIVATE ${POPT_INCLUDE_DIR})
+else()
+    # Build included popt as fallback
+    add_library(popt STATIC 
+        popt/popt.c popt/poptconfig.c popt/popthelp.c popt/poptparse.c popt/poptint.c
+    )
+    # Exclude CMAKE_CURRENT_SOURCE_DIR to avoid io.h clash
+    target_include_directories(popt PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/popt ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+    target_link_libraries(rsync PRIVATE popt)
+    target_include_directories(rsync PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/popt)
+endif()
+
+# Test Helpers
+add_executable(tls tls.c syscall.c util2.c t_stub.c lib/compat.c lib/snprintf.c lib/permstring.c lib/sysxattrs.c)
+target_link_libraries(tls PRIVATE posix_shims ws2_32 netapi32 popt)
+target_include_directories(tls PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/lib ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+add_executable(trimslash trimslash.c syscall.c util2.c t_stub.c lib/compat.c lib/snprintf.c)
+target_link_libraries(trimslash PRIVATE posix_shims ws2_32 netapi32)
+target_include_directories(trimslash PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/lib ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+add_executable(t_unsafe t_unsafe.c syscall.c util1.c util2.c t_stub.c lib/compat.c lib/snprintf.c lib/wildmatch.c)
+target_link_libraries(t_unsafe PRIVATE posix_shims ws2_32 netapi32)
+target_include_directories(t_unsafe PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/lib ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+add_executable(t_chmod_secure t_chmod_secure.c syscall.c util1.c util2.c t_stub.c lib/compat.c lib/snprintf.c lib/wildmatch.c lib/permstring.c)
+target_link_libraries(t_chmod_secure PRIVATE posix_shims ws2_32 netapi32)
+target_include_directories(t_chmod_secure PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/lib ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+add_executable(t_secure_relpath t_secure_relpath.c syscall.c util1.c util2.c t_stub.c lib/compat.c lib/snprintf.c lib/wildmatch.c lib/permstring.c)
+target_link_libraries(t_secure_relpath PRIVATE posix_shims ws2_32 netapi32)
+target_include_directories(t_secure_relpath PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/lib ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+add_executable(wildtest wildtest.c t_stub.c lib/compat.c lib/snprintf.c)
+target_link_libraries(wildtest PRIVATE posix_shims ws2_32 netapi32 popt)
+target_include_directories(wildtest PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/lib ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+add_executable(getgroups getgroups.c)
+target_link_libraries(getgroups PRIVATE posix_shims ws2_32 netapi32)
+target_include_directories(getgroups PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/lib ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+add_executable(getfsdev getfsdev.c)
+target_link_libraries(getfsdev PRIVATE posix_shims ws2_32 netapi32)
+target_include_directories(getfsdev PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/lib ${CMAKE_CURRENT_SOURCE_DIR}/popt ${AUTO_WIN_MSVC_DIR} ${POSIX_INCLUDES} ${LINUX_INCLUDES})
+
+# Tests
+enable_testing()
+find_program(PYTHON_EXECUTABLE python)
+if(PYTHON_EXECUTABLE)
+    file(GLOB TEST_SCRIPTS "${CMAKE_CURRENT_SOURCE_DIR}/testsuite/*_test.py")
+    foreach(TEST_SCRIPT IN LISTS TEST_SCRIPTS)
+        get_filename_component(TEST_NAME ${TEST_SCRIPT} NAME)
+        add_test(
+            NAME ${TEST_NAME}
+            COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/runtests.py --rsync-bin $<TARGET_FILE:rsync> ${TEST_SCRIPT}
+            WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+        )
+        # Ensure test uses the helpers built here
+        set_tests_properties(${TEST_NAME} PROPERTIES ENVIRONMENT "TOOLDIR=$<TARGET_FILE_DIR:tls>")
+    endforeach()
+endif()
diff --git a/config.h.in b/config.h.in
new file mode 100644
index 000000000..49c67462e
--- /dev/null
+++ b/config.h.in
@@ -0,0 +1,115 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#ifdef _MSC_VER
+#include <stdint.h>
+typedef int32_t int32;
+typedef uint32_t uint32;
+typedef int64_t int64;
+typedef uint64_t uint64;
+typedef int16_t int16;
+typedef uint16_t uint16;
+
+#include "../auto-win-msvc/namespace_win_shim.h"
+
+// Interpolated config variables from CMake
+#cmakedefine HAVE_CONFIG_H 1
+#define RSYNC_VERSION "@RSYNC_VERSION@"
+#cmakedefine HAVE_ZLIB 1
+#cmakedefine HAVE_OPENSSL 1
+#cmakedefine HAVE_STRERROR 1
+#define PACKAGE "@PACKAGE@"
+#define POPT_SYSCONFDIR "@POPT_SYSCONFDIR@"
+
+#ifndef __builtin_expect
+#define __builtin_expect(exp, c) (exp)
+#endif
+
+// Some extra missing types/macros for rsync
+#define PATH_MAX MAX_PATH
+
+#define SIZEOF_INT @SIZEOF_INT@
+#define SIZEOF_LONG @SIZEOF_LONG@
+#define SIZEOF_SHORT @SIZEOF_SHORT@
+#define SIZEOF_INT32_T @SIZEOF_INT32_T@
+#define SIZEOF_UINT32_T @SIZEOF_UINT32_T@
+#define SIZEOF_INT64_T @SIZEOF_INT64_T@
+#define SIZEOF_UINT64_T @SIZEOF_UINT64_T@
+#define SIZEOF_OFF_T @SIZEOF_OFF_T@
+#define SIZEOF_TIME_T @SIZEOF_TIME_T@
+#define SIZEOF_CHARP @SIZEOF_CHARP@
+
+#cmakedefine HAVE_SIZE_T 1
+#cmakedefine HAVE_OFF_T 1
+#cmakedefine HAVE_TIME_T 1
+#cmakedefine HAVE_PID_T 1
+#cmakedefine HAVE_DIRENT_H 1
+#cmakedefine HAVE_UTIME 1
+#cmakedefine HAVE_UTIMES 1
+#cmakedefine HAVE_STRPBRK 1
+#cmakedefine HAVE_GETCWD 1
+#cmakedefine HAVE_STRUCT_ADDRINFO 1
+#cmakedefine HAVE_STRUCT_SOCKADDR_STORAGE 1
+#cmakedefine HAVE_GETADDRINFO 1
+#cmakedefine HAVE_GETNAMEINFO 1
+#cmakedefine HAVE_SOCKADDR_IN6 1
+#cmakedefine HAVE_MEMMOVE 1
+#cmakedefine HAVE_GETTIMEOFDAY_TZ 1
+#cmakedefine HAVE_READLINK 1
+
+#define direct dirent
+
+#ifndef S_ISUID
+#define S_ISUID 04000
+#endif
+#ifndef S_ISGID
+#define S_ISGID 02000
+#endif
+#ifndef S_ISVTX
+#define S_ISVTX 01000
+#endif
+
+#cmakedefine SIGUSR1 @SIGUSR1@
+#cmakedefine SIGUSR2 @SIGUSR2@
+#cmakedefine SIGHUP @SIGHUP@
+#cmakedefine SIGALRM @SIGALRM@
+#cmakedefine WNOHANG @WNOHANG@
+#cmakedefine O_NOFOLLOW @O_NOFOLLOW@
+#cmakedefine O_DIRECTORY @O_DIRECTORY@
+#cmakedefine AT_REMOVEDIR @AT_REMOVEDIR@
+
+#define RSYNC_RSH "@RSYNC_RSH@"
+#define NOBODY_USER "@NOBODY_USER@"
+#define NOBODY_GROUP "@NOBODY_GROUP@"
+#define RSYNCD_SYSCONF "@RSYNCD_SYSCONF@"
+
+#define index strchr
+#define rindex strrchr
+
+#ifndef major
+#define major(dev) 0
+#define minor(dev) 0
+#define makedev(maj, min) 0
+#endif
+
+static inline int do_chmod_at(int a, const char* b, int c) { return 0; }
+static inline int fchdir(int a) { return 0; }
+#define WIFSIGNALED(x) 0
+#define SIGACTMASK(a,b) 0
+static inline int unlinkat(int a, const char* b, int c) { return 0; }
+static inline int renameat(int a, const char* b, int c, const char* d) { return 0; }
+static inline int mkdirat(int a, const char* b, int c) { return 0; }
+static inline int chroot(const char* a) { return 0; }
+static inline char* getpass(const char* a) { return ""; }
+static inline char* getwd(char* a) { return ""; }
+static inline int wait3(int* a, int b, void* c) { return 0; }
+static inline struct tm *gmtime_r(const time_t *timep, struct tm *result) { return gmtime_s(result, timep) == 0 ? result : NULL; }
+
+#include <corecrt_io.h>
+
+#define socketpair posix_socketpair
+extern int posix_socketpair(int domain, int type, int protocol, int socket_vector[2]);
+
+#endif
+
+#endif // CONFIG_H
diff --git a/runtests.py b/runtests.py
index 2259aee15..1b04850ce 100755
--- a/runtests.py
+++ b/runtests.py
@@ -346,6 +346,8 @@ def main():
     required_helpers = ['tls', 'trimslash', 't_unsafe', 't_chmod_secure',
                         't_secure_relpath',
                         'wildtest', 'getgroups', 'getfsdev']
+    if sys.platform == 'win32':
+        required_helpers = [h + '.exe' for h in required_helpers]
     missing = [h for h in required_helpers
                if not os.path.isfile(os.path.join(tooldir, h))]
     if missing:
diff --git a/testsuite/rsyncfns.py b/testsuite/rsyncfns.py
index 3a3b37b19..c4ba5b94f 100644
--- a/testsuite/rsyncfns.py
+++ b/testsuite/rsyncfns.py
@@ -18,7 +18,11 @@
 from __future__ import annotations
 
 import atexit
-import fcntl
+try:
+    import fcntl
+except ImportError:
+    fcntl = None
+    import msvcrt
 import filecmp
 import os
 import platform
@@ -196,9 +200,17 @@ def claim_ports(*ports: int) -> 'None':
     if _port_lock_fd is None:
         _port_lock_fd = _open_lock_file()
     for port in sorted(ports):
-        # F_SETLKW via fcntl.lockf(LOCK_EX, length, start): exclusive
-        # byte-range lock on byte `port`, blocking until acquired.
-        fcntl.lockf(_port_lock_fd, fcntl.LOCK_EX, 1, port)
+        # exclusive byte-range lock on byte `port`, blocking until acquired.
+        if fcntl:
+            fcntl.lockf(_port_lock_fd, fcntl.LOCK_EX, 1, port)
+        else:
+            os.lseek(_port_lock_fd, port, os.SEEK_SET)
+            while True:
+                try:
+                    msvcrt.locking(_port_lock_fd, msvcrt.LK_LOCK, 1)
+                    break
+                except OSError:
+                    time.sleep(0.1)
 
 
 # --- standalone rsyncd helpers ---------------------------------------------
diff --git a/vcpkg.json b/vcpkg.json
new file mode 100644
index 000000000..d99c35304
--- /dev/null
+++ b/vcpkg.json
@@ -0,0 +1,12 @@
+{
+  "name": "rsync",
+  "version": "3.3.0",
+  "dependencies": [
+    "zlib",
+    "zstd",
+    "lz4",
+    "xxhash",
+    "openssl"
+  ],
+  "builtin-baseline": "aa40adda5352e87655b8583cfb2451d5e9e276fd"
+}