diff --git a/relenv/_resources/xz/crc32_table.c b/relenv/_resources/xz/crc32_table.c
new file mode 100644
index 00000000..b11762ae
--- /dev/null
+++ b/relenv/_resources/xz/crc32_table.c
@@ -0,0 +1,22 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       crc32_table.c
+/// \brief      Precalculated CRC32 table with correct endianness
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "common.h"
+
+// Having the declaration here silences clang -Wmissing-variable-declarations.
+extern const uint32_t lzma_crc32_table[8][256];
+
+#ifdef WORDS_BIGENDIAN
+#	include "crc32_table_be.h"
+#else
+#	include "crc32_table_le.h"
+#endif
diff --git a/relenv/_resources/xz/crc64_table.c b/relenv/_resources/xz/crc64_table.c
new file mode 100644
index 00000000..688e527b
--- /dev/null
+++ b/relenv/_resources/xz/crc64_table.c
@@ -0,0 +1,33 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       crc64_table.c
+/// \brief      Precalculated CRC64 table with correct endianness
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "common.h"
+
+
+// FIXME: Compared to crc64_fast.c this has to check for __x86_64__ too
+// so that in 32-bit builds crc64_x86.S won't break due to a missing table.
+#if (defined(__x86_64__) && defined(__SSSE3__) \
+			&& defined(__SSE4_1__) && defined(__PCLMUL__)) \
+		|| (defined(__e2k__) && __iset__ >= 6)
+// No table needed. Use a typedef to avoid an empty translation unit.
+typedef void lzma_crc64_dummy;
+
+#else
+// Having the declaration here silences clang -Wmissing-variable-declarations.
+extern const uint64_t lzma_crc64_table[4][256];
+
+#	if defined(WORDS_BIGENDIAN)
+#		include "crc64_table_be.h"
+#	else
+#		include "crc64_table_le.h"
+#	endif
+#endif
diff --git a/relenv/_resources/xz/readme.md b/relenv/_resources/xz/readme.md
index 96e13414..eefdf4dc 100644
--- a/relenv/_resources/xz/readme.md
+++ b/relenv/_resources/xz/readme.md
@@ -1,4 +1,13 @@
-The config.h file was removed from XZ-Utils tarting with version 5.5.0.
-XZ-Utils seems to build just fine with the config.h file from 5.4.7, so we're
-including it here. This will be copied into the src/windows directory in the
-extracted source for XZ-Utils.
+The config.h file was removed from XZ-Utils starting with version 5.5.0.
+XZ-Utils switched to CMake and removed Visual Studio project files and
+pre-generated headers/sources.
+
+We include the following files from XZ 5.4.7 to maintain compatibility with
+Python's MSBuild-based build system on Windows (PCbuild/liblzma.vcxproj):
+
+- config.h (src/common/config.h)
+- crc32_table.c (src/liblzma/check/crc32_table.c)
+- crc64_table.c (src/liblzma/check/crc64_table.c)
+
+These files are copied into the extracted XZ source directory during the
+Windows build process if they are missing.
diff --git a/relenv/build/windows.py b/relenv/build/windows.py
index 6549d70b..eaa8a7ac 100644
--- a/relenv/build/windows.py
+++ b/relenv/build/windows.py
@@ -197,6 +197,14 @@ def update_xz(dirs: Dirs, env: EnvMapping) -> None:
     config_file_source = dirs.root / "_resources" / "xz" / "config.h"
     if not config_file.exists():
         shutil.copy(str(config_file_source), str(config_file))
+
+    # Also copy crc32_table.c and crc64_table.c which are missing in newer XZ tarballs
+    check_dir = target_dir / "src" / "liblzma" / "check"
+    for filename in ["crc32_table.c", "crc64_table.c"]:
+        target_file = check_dir / filename
+        source_file = dirs.root / "_resources" / "xz" / filename
+        if not target_file.exists():
+            shutil.copy(str(source_file), str(target_file))
     # Update externals.spdx.json with the correct version, url, and hash
     # This became a thing in 3.12
     if env["RELENV_PY_MAJOR_VERSION"] in ["3.12", "3.13", "3.14"]:
diff --git a/relenv/python-versions.json b/relenv/python-versions.json
index 61fadb99..5b092020 100644
--- a/relenv/python-versions.json
+++ b/relenv/python-versions.json
@@ -203,6 +203,14 @@
      "linux",
      "darwin"
     ]
+   },
+   "3.6.1": {
+    "url": "https://github.com/openssl/openssl/releases/download/openssl-{version}/openssl-{version}.tar.gz",
+    "sha256": "b1bfedcd5b289ff22aee87c9d600f515767ebf45f77168cb6d64f231f518a82e",
+    "platforms": [
+     "linux",
+     "darwin"
+    ]
    }
   },
   "sqlite": {
@@ -225,6 +233,16 @@
      "darwin",
      "win32"
     ]
+   },
+   "3.51.2.0": {
+    "url": "https://sqlite.org/2026/sqlite-autoconf-{version}.tar.gz",
+    "sha256": "fbd89f866b1403bb66a143065440089dd76100f2238314d92274a082d4f2b7bb",
+    "sqliteversion": "3510200",
+    "platforms": [
+     "linux",
+     "darwin",
+     "win32"
+    ]
    }
   },
   "xz": {
@@ -235,6 +253,15 @@
      "linux",
      "darwin"
     ]
+   },
+   "5.8.2": {
+    "url": "http://tukaani.org/xz/xz-{version}.tar.gz",
+    "sha256": "ce09c50a5962786b83e5da389c90dd2c15ecd0980a258dd01f70f9e7ce58a8f1",
+    "platforms": [
+     "linux",
+     "darwin",
+     "win32"
+    ]
    }
   },
   "libffi": {
@@ -262,6 +289,13 @@
     "platforms": [
      "linux"
     ]
+   },
+   "6.6": {
+    "url": "https://mirrors.ocf.berkeley.edu/gnu/ncurses/ncurses-{version}.tar.gz",
+    "sha256": "355b4cbbed880b0381a04c46617b7656e362585d52e9cf84a67e2009b749ff11",
+    "platforms": [
+     "linux"
+    ]
    }
   },
   "readline": {
@@ -344,6 +378,15 @@
      "darwin",
      "win32"
     ]
+   },
+   "2.7.4": {
+    "url": "https://github.com/libexpat/libexpat/releases/download/R_2_7_4/expat-{version}.tar.xz",
+    "sha256": "9e9cabb457c1e09de91db2706d8365645792638eb3be1f94dbb2149301086ac0",
+    "platforms": [
+     "linux",
+     "darwin",
+     "win32"
+    ]
    }
   }
  }
diff --git a/tests/test_build.py b/tests/test_build.py
index 19740038..1e273ac3 100644
--- a/tests/test_build.py
+++ b/tests/test_build.py
@@ -154,8 +154,8 @@ def test_get_dependency_version_sqlite_all_platforms() -> None:
 def test_get_dependency_version_xz_all_platforms() -> None:
     """Test getting XZ version for various platforms."""
     # XZ 5.5.0+ removed MSBuild support, so Windows uses a fallback version
-    # and XZ is not in JSON for win32
-    for platform in ["linux", "darwin"]:
+    # BUT we now have XZ 5.8.2 in python-versions.json for win32 too
+    for platform in ["linux", "darwin", "win32"]:
         result = get_dependency_version("xz", platform)
         assert result is not None, f"XZ should be available for {platform}"
         assert isinstance(result, dict)
@@ -166,10 +166,6 @@ def test_get_dependency_version_xz_all_platforms() -> None:
         assert "xz" in result["url"].lower()
         assert isinstance(result["sha256"], str)
 
-    # Windows should return None (uses hardcoded fallback in windows.py)
-    result = get_dependency_version("xz", "win32")
-    assert result is None, "XZ should not be in JSON for win32 (uses fallback)"
-
 
 def test_get_dependency_version_nonexistent() -> None:
     """Test that nonexistent dependency returns None."""