diff --git a/CHANGELOG.md b/CHANGELOG.md
index bbbf79ce..33857922 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,8 @@
 
 ### Added
 
+- **openkal-posix 0.1.0。** 写在 POSIX C 库之上的 openkal 实现，为没有自身实现的系统服务；提供十五个接口（net、datagram、
+  prof、debug 不提供，名字不定义）；声明 `requires = ["mcpp:c-abi"]`。新增成员 `tests/examples/openkal-posix`（Linux、macOS）。
 - **openkal-musl 0.29.0 与 openkal-llvm-runtime 0.20.0，一次变更。** musl 的 `execvp`、`execvpe`、`execlp` 与 `posix_spawnp`
   按 `kal_env_system` 所述系统的约定查找程序（Windows：PATH 以 `;` 分隔，无后缀的名字依次试 `PATHEXT` 各后缀）；`link`、`linkat`
   经 `kal_fs_hard_link` 实现；声明 `requires = ["mcpp:kernel-abi=openkal"]`；依赖改为 openkal 0.25 一族。llvm-runtime 依赖
diff --git a/mcpp.toml b/mcpp.toml
index fa0312e3..84489f03 100644
--- a/mcpp.toml
+++ b/mcpp.toml
@@ -261,6 +261,7 @@ members = [
     "tests/examples/mcr",
     "tests/examples/openkal",
     "tests/examples/openkal-kit",
+    "tests/examples/openkal-posix",
     "tests/examples/openkal-musl",
     "tests/examples/openkal-platform",
     "tests/examples/compiler-rt-builtins",
diff --git a/pkgs/o/openkal-posix.lua b/pkgs/o/openkal-posix.lua
new file mode 100644
index 00000000..6126dc51
--- /dev/null
+++ b/pkgs/o/openkal-posix.lua
@@ -0,0 +1,52 @@
+-- openkal-posix --- openkal written above a POSIX C library.
+--
+-- No descriptor-level `deps`: the source manifest names the openkal contract.
+-- The implementation calls the system's own C library and states
+-- `requires = ["mcpp:c-abi"]`, so it is placed above that C library and never
+-- beneath one written above openkal. It provides fifteen of openkal's
+-- interfaces; net, datagram, prof and debug are absent.
+--
+-- The package is listed for every platform because a descriptor's platform
+-- table describes availability rather than applicability. A project selects
+-- this implementation with a conditional dependency on the systems it serves,
+-- and a project that selects it where no POSIX C library exists fails at
+-- compile time, which is the correct place for that failure.
+package = {
+    spec        = "1",
+    namespace   = "mcpplibs",
+    name        = "openkal-posix",
+    description = "An implementation of openkal written above a POSIX C library, for the systems that have no implementation of their own",
+    licenses    = {"Apache-2.0"},
+    repo        = "https://github.com/mcpplibs/openkal-posix",
+    type        = "package",
+
+    xpm = {
+        linux = {
+            ["0.1.0"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpplibs/openkal-posix/archive/refs/tags/0.1.0.tar.gz",
+                    CN = "https://gitcode.com/mcpp-res/openkal-posix/releases/download/0.1.0/openkal-posix-0.1.0.tar.gz",
+                },
+                sha256 = "09878176d163b44675712f0bb285b87f9a8e0f9688b23c0aa4d0ab627f5ebeae",
+            },
+        },
+        macosx = {
+            ["0.1.0"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpplibs/openkal-posix/archive/refs/tags/0.1.0.tar.gz",
+                    CN = "https://gitcode.com/mcpp-res/openkal-posix/releases/download/0.1.0/openkal-posix-0.1.0.tar.gz",
+                },
+                sha256 = "09878176d163b44675712f0bb285b87f9a8e0f9688b23c0aa4d0ab627f5ebeae",
+            },
+        },
+        windows = {
+            ["0.1.0"] = {
+                url = {
+                    GLOBAL = "https://github.com/mcpplibs/openkal-posix/archive/refs/tags/0.1.0.tar.gz",
+                    CN = "https://gitcode.com/mcpp-res/openkal-posix/releases/download/0.1.0/openkal-posix-0.1.0.tar.gz",
+                },
+                sha256 = "09878176d163b44675712f0bb285b87f9a8e0f9688b23c0aa4d0ab627f5ebeae",
+            },
+        },
+    },
+}
diff --git a/tests/examples/openkal-posix/mcpp.toml b/tests/examples/openkal-posix/mcpp.toml
new file mode 100644
index 00000000..5c5a3836
--- /dev/null
+++ b/tests/examples/openkal-posix/mcpp.toml
@@ -0,0 +1,17 @@
+# openkal-posix test project: openkal above the system's own C library, on the
+# systems this index's runners have one (Linux, macOS). The observation is of
+# behaviour through the C surface (tests/kal.cpp): the interfaces it states, a
+# write to a stream, the environment and the system's name, a file written and
+# read back. On Windows nothing is named and the program observes nothing.
+[package]
+name    = "openkal-posix-tests"
+version = "0.1.0"
+
+[target.'cfg(any(os = "linux", os = "macos"))'.dependencies.mcpplibs]
+openkal       = "0.25.0"
+openkal-posix = "0.1.0"
+
+# This member names mcpplibs packages, which the workspace root's single
+# redirect does not carry, so it states its own.
+[indices]
+mcpplibs = { path = "../../.." }
diff --git a/tests/examples/openkal-posix/tests/kal.cpp b/tests/examples/openkal-posix/tests/kal.cpp
new file mode 100644
index 00000000..67d06267
--- /dev/null
+++ b/tests/examples/openkal-posix/tests/kal.cpp
@@ -0,0 +1,43 @@
+// openkal-posix through the index, observed through the C surface.
+#include <cstdio>
+#include <cstring>
+#if defined(__linux__) || defined(__APPLE__)
+#include <openkal.h>
+
+int main() {
+    int failures = 0;
+    auto check = [&](bool held, const char* what) {
+        if (!held) { std::printf("FAIL: %s\n", what); ++failures; }
+    };
+    const kal_u64 stated = kal_interfaces();
+    check((stated & KAL_IFACE_FS) && (stated & KAL_IFACE_PROCESS) && (stated & KAL_IFACE_TASK),
+          "the interfaces it provides are stated");
+    check(!(stated & KAL_IFACE_NET) && !(stated & KAL_IFACE_PROF), "and those it does not are not");
+    check(kal_stream_write(kal_stdout(), "openkal-posix\n", 14) == 14, "a stream is written");
+    char sys[32] = {};
+    const kal_intptr n = kal_env_system(sys, sizeof sys - 1);
+    check(n > 0, "the system is named");
+    kal_dir here{};
+    check(kal_fs_preopen_count() > 0 && kal_fs_preopen(0, &here, nullptr, 0, nullptr) == kal_ok,
+          "a directory is granted");
+    kal_file f{};
+    if (kal_fs_open(here, "okp-index.tmp", 13,
+                    KAL_OPEN_WRITE | KAL_OPEN_CREATE | KAL_OPEN_TRUNCATE, &f) == kal_ok) {
+        kal_stream_write(kal_fs_stream(f), "abc", 3);
+        kal_fs_close_file(f);
+        char b[4] = {};
+        kal_file g{};
+        check(kal_fs_open(here, "okp-index.tmp", 13, KAL_OPEN_READ, &g) == kal_ok
+                  && kal_stream_read(kal_fs_stream(g), b, 3) == 3 && std::memcmp(b, "abc", 3) == 0,
+              "a file is written and read back");
+        if (g.h) kal_fs_close_file(g);
+        kal_fs_remove(here, "okp-index.tmp", 13);
+    } else {
+        check(false, "a file is created");
+    }
+    if (failures == 0) std::printf("openkal-posix: the C surface answers\n");
+    return failures == 0 ? 0 : 1;
+}
+#else
+int main() { std::printf("openkal-posix: no POSIX C library is named on this system\n"); return 0; }
+#endif