diff --git a/c-grates/per-syscall-grates/close-grate/build.conf b/c-grates/per-syscall-grates/close-grate/build.conf
new file mode 100644
index 0000000..4baaf6a
--- /dev/null
+++ b/c-grates/per-syscall-grates/close-grate/build.conf
@@ -0,0 +1 @@
+ENTRY=close-grate.c
diff --git a/c-grates/per-syscall-grates/close-grate/compile_grate.sh b/c-grates/per-syscall-grates/close-grate/compile_grate.sh
new file mode 100755
index 0000000..9899f0e
--- /dev/null
+++ b/c-grates/per-syscall-grates/close-grate/compile_grate.sh
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+cd "$(dirname "$0")"
+lind_compile -s --compile-grate --output-dir grates src/close-grate.c
diff --git a/c-grates/per-syscall-grates/close-grate/src/close-grate.c b/c-grates/per-syscall-grates/close-grate/src/close-grate.c
new file mode 100644
index 0000000..62abe43
--- /dev/null
+++ b/c-grates/per-syscall-grates/close-grate/src/close-grate.c
@@ -0,0 +1,71 @@
+#include <errno.h>
+#include <lind_syscall.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define CLOSE_SYSCALL 3
+
+int pass_fptr_to_wt(uint64_t fn_ptr_uint, uint64_t grateid, uint64_t arg1,
+                    uint64_t arg1cage, uint64_t arg2, uint64_t arg2cage,
+                    uint64_t arg3, uint64_t arg3cage, uint64_t arg4,
+                    uint64_t arg4cage, uint64_t arg5, uint64_t arg5cage,
+                    uint64_t arg6, uint64_t arg6cage) {
+  if (fn_ptr_uint == 0) {
+    return -1;
+  }
+
+  int (*fn)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+            uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+            uint64_t) =
+      (int (*)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+               uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+               uint64_t))(uintptr_t)fn_ptr_uint;
+
+  return fn(grateid, arg1, arg1cage, arg2, arg2cage, arg3, arg3cage, arg4,
+            arg4cage, arg5, arg5cage, arg6, arg6cage);
+}
+
+int close_grate(uint64_t cageid, uint64_t arg1, uint64_t arg1cage,
+                 uint64_t arg2, uint64_t arg2cage, uint64_t arg3,
+                 uint64_t arg3cage, uint64_t arg4, uint64_t arg4cage,
+                 uint64_t arg5, uint64_t arg5cage, uint64_t arg6,
+                 uint64_t arg6cage) {
+
+  return make_threei_call(CLOSE_SYSCALL, 0, cageid, arg1cage, arg1,
+                          arg1cage, arg2, arg2cage, arg3, arg3cage, arg4,
+                          arg4cage, arg5, arg5cage, arg6, arg6cage, 0);
+}
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <cage_file>\n", argv[0]);
+    exit(EXIT_FAILURE);
+  }
+  int grateid = getpid();
+
+  pid_t pid = fork();
+  if (pid < 0) {
+    perror("fork failed");
+    exit(EXIT_FAILURE);
+  } else if (pid == 0) {
+    int cageid = getpid();
+    
+    uint64_t fn_ptr_addr = (uint64_t)(uintptr_t)&close_grate;
+    int ret = register_handler(cageid, CLOSE_SYSCALL, grateid, fn_ptr_addr);
+
+    if (execv(argv[1], &argv[1]) == -1) {
+      perror("execv failed");
+      exit(EXIT_FAILURE);
+    }
+  }
+
+  int status;
+  while (wait(&status) > 0) {
+    printf("[Grate|close] terminated, status: %d\n", status);
+  }
+
+  return 0;
+}
diff --git a/c-grates/per-syscall-grates/close-grate/test/close-test.c b/c-grates/per-syscall-grates/close-grate/test/close-test.c
new file mode 100644
index 0000000..e502b9d
--- /dev/null
+++ b/c-grates/per-syscall-grates/close-grate/test/close-test.c
@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <assert.h>
+
+int main() {
+    int fd;
+    const char *filename = "testfile.txt";
+
+    // 1. Open a file to get a valid fd
+    fd = open(filename, O_CREAT | O_RDWR, 0644);
+    assert(fd >= 0);
+
+    // 2. Close should succeed
+    int ret = close(fd);
+    assert(ret == 0);
+
+    // 3. Closing again should fail (EBADF)
+    ret = close(fd);
+    assert(ret == -1);
+    assert(errno == EBADF);
+
+    // 4. Closing an invalid fd should fail
+    ret = close(-1);
+    assert(ret == -1);
+    assert(errno == EBADF);
+
+    // 5. Cleanup: remove the file
+    ret = unlink(filename);
+    assert(ret == 0);
+
+    printf("All close() tests passed.\n");
+    return 0;
+}
diff --git a/c-grates/per-syscall-grates/geteuid-grate/build.conf b/c-grates/per-syscall-grates/geteuid-grate/build.conf
new file mode 100644
index 0000000..7b82194
--- /dev/null
+++ b/c-grates/per-syscall-grates/geteuid-grate/build.conf
@@ -0,0 +1 @@
+ENTRY=geteuid-grate.c
diff --git a/c-grates/per-syscall-grates/geteuid-grate/compile_grate.sh b/c-grates/per-syscall-grates/geteuid-grate/compile_grate.sh
new file mode 100755
index 0000000..7a2b40d
--- /dev/null
+++ b/c-grates/per-syscall-grates/geteuid-grate/compile_grate.sh
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+cd "$(dirname "$0")"
+lind_compile -s --compile-grate --output-dir grates src/geteuid-grate.c
diff --git a/c-grates/per-syscall-grates/geteuid-grate/src/geteuid-grate.c b/c-grates/per-syscall-grates/geteuid-grate/src/geteuid-grate.c
new file mode 100644
index 0000000..54853c6
--- /dev/null
+++ b/c-grates/per-syscall-grates/geteuid-grate/src/geteuid-grate.c
@@ -0,0 +1,71 @@
+#include <errno.h>
+#include <lind_syscall.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define GETEUID_SYSCALL 107
+
+int pass_fptr_to_wt(uint64_t fn_ptr_uint, uint64_t grateid, uint64_t arg1,
+                    uint64_t arg1cage, uint64_t arg2, uint64_t arg2cage,
+                    uint64_t arg3, uint64_t arg3cage, uint64_t arg4,
+                    uint64_t arg4cage, uint64_t arg5, uint64_t arg5cage,
+                    uint64_t arg6, uint64_t arg6cage) {
+  if (fn_ptr_uint == 0) {
+    return -1;
+  }
+
+  int (*fn)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+            uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+            uint64_t) =
+      (int (*)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+               uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+               uint64_t))(uintptr_t)fn_ptr_uint;
+
+  return fn(grateid, arg1, arg1cage, arg2, arg2cage, arg3, arg3cage, arg4,
+            arg4cage, arg5, arg5cage, arg6, arg6cage);
+}
+
+int geteuid_grate(uint64_t cageid, uint64_t arg1, uint64_t arg1cage,
+                 uint64_t arg2, uint64_t arg2cage, uint64_t arg3,
+                 uint64_t arg3cage, uint64_t arg4, uint64_t arg4cage,
+                 uint64_t arg5, uint64_t arg5cage, uint64_t arg6,
+                 uint64_t arg6cage) {
+
+  return make_threei_call(GETEUID_SYSCALL, 0, cageid, arg1cage, arg1,
+                          arg1cage, arg2, arg2cage, arg3, arg3cage, arg4,
+                          arg4cage, arg5, arg5cage, arg6, arg6cage, 0);
+}
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <cage_file>\n", argv[0]);
+    exit(EXIT_FAILURE);
+  }
+  int grateid = getpid();
+
+  pid_t pid = fork();
+  if (pid < 0) {
+    perror("fork failed");
+    exit(EXIT_FAILURE);
+  } else if (pid == 0) {
+    int cageid = getpid();
+    
+    uint64_t fn_ptr_addr = (uint64_t)(uintptr_t)&geteuid_grate;
+    int ret = register_handler(cageid, GETEUID_SYSCALL, grateid, fn_ptr_addr);
+
+    if (execv(argv[1], &argv[1]) == -1) {
+      perror("execv failed");
+      exit(EXIT_FAILURE);
+    }
+  }
+
+  int status;
+  while (wait(&status) > 0) {
+    printf("[Grate|geteuid] terminated, status: %d\n", status);
+  }
+
+  return 0;
+}
diff --git a/c-grates/per-syscall-grates/geteuid-grate/test/geteuid-test.c b/c-grates/per-syscall-grates/geteuid-grate/test/geteuid-test.c
new file mode 100644
index 0000000..e627830
--- /dev/null
+++ b/c-grates/per-syscall-grates/geteuid-grate/test/geteuid-test.c
@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <assert.h>
+
+int main() {
+    uid_t euid1, euid2;
+
+    // 1. Multiple calls should be consistent
+    euid1 = geteuid();
+    euid2 = geteuid();
+    assert(euid1 == euid2);
+
+    // 2. EUID should be non-negative
+    assert(euid1 >= 0);
+
+    // 3. Save original IDs
+    uid_t ruid = getuid();
+    uid_t orig_euid = euid1;
+
+    // 4. Try changing effective UID (may fail if not permitted)
+    if (seteuid(ruid) == 0) {
+        uid_t new_euid = geteuid();
+        assert(new_euid == ruid);
+
+        // Restore original effective UID
+        int ret = seteuid(orig_euid);
+        assert(ret == 0);
+
+        // Verify restoration
+        assert(geteuid() == orig_euid);
+    } else {
+        // If we can't change EUID, just note it
+        printf("Skipping seteuid() test (insufficient permissions)\n");
+    }
+
+    printf("geteuid() test passed (euid=%d)\n", orig_euid);
+    return 0;
+}
diff --git a/c-grates/per-syscall-grates/getpid-grate/build.conf b/c-grates/per-syscall-grates/getpid-grate/build.conf
new file mode 100644
index 0000000..1e06b5a
--- /dev/null
+++ b/c-grates/per-syscall-grates/getpid-grate/build.conf
@@ -0,0 +1 @@
+ENTRY=getpid-grate.c
diff --git a/c-grates/per-syscall-grates/getpid-grate/compile_grate.sh b/c-grates/per-syscall-grates/getpid-grate/compile_grate.sh
new file mode 100755
index 0000000..88d0fe8
--- /dev/null
+++ b/c-grates/per-syscall-grates/getpid-grate/compile_grate.sh
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+cd "$(dirname "$0")"
+lind_compile -s --compile-grate --output-dir grates src/getpid-grate.c
diff --git a/c-grates/per-syscall-grates/getpid-grate/src/getpid-grate.c b/c-grates/per-syscall-grates/getpid-grate/src/getpid-grate.c
new file mode 100644
index 0000000..a245139
--- /dev/null
+++ b/c-grates/per-syscall-grates/getpid-grate/src/getpid-grate.c
@@ -0,0 +1,71 @@
+#include <errno.h>
+#include <lind_syscall.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define GETPID_SYSCALL 39
+
+int pass_fptr_to_wt(uint64_t fn_ptr_uint, uint64_t grateid, uint64_t arg1,
+                    uint64_t arg1cage, uint64_t arg2, uint64_t arg2cage,
+                    uint64_t arg3, uint64_t arg3cage, uint64_t arg4,
+                    uint64_t arg4cage, uint64_t arg5, uint64_t arg5cage,
+                    uint64_t arg6, uint64_t arg6cage) {
+  if (fn_ptr_uint == 0) {
+    return -1;
+  }
+
+  int (*fn)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+            uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+            uint64_t) =
+      (int (*)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+               uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+               uint64_t))(uintptr_t)fn_ptr_uint;
+
+  return fn(grateid, arg1, arg1cage, arg2, arg2cage, arg3, arg3cage, arg4,
+            arg4cage, arg5, arg5cage, arg6, arg6cage);
+}
+
+int getpid_grate(uint64_t cageid, uint64_t arg1, uint64_t arg1cage,
+                 uint64_t arg2, uint64_t arg2cage, uint64_t arg3,
+                 uint64_t arg3cage, uint64_t arg4, uint64_t arg4cage,
+                 uint64_t arg5, uint64_t arg5cage, uint64_t arg6,
+                 uint64_t arg6cage) {
+
+  return make_threei_call(GETPID_SYSCALL, 0, cageid, arg1cage, arg1,
+                          arg1cage, arg2, arg2cage, arg3, arg3cage, arg4,
+                          arg4cage, arg5, arg5cage, arg6, arg6cage, 0);
+}
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <cage_file>\n", argv[0]);
+    exit(EXIT_FAILURE);
+  }
+  int grateid = getpid();
+
+  pid_t pid = fork();
+  if (pid < 0) {
+    perror("fork failed");
+    exit(EXIT_FAILURE);
+  } else if (pid == 0) {
+    int cageid = getpid();
+    
+    uint64_t fn_ptr_addr = (uint64_t)(uintptr_t)&getpid_grate;
+    int ret = register_handler(cageid, GETPID_SYSCALL, grateid, fn_ptr_addr);
+
+    if (execv(argv[1], &argv[1]) == -1) {
+      perror("execv failed");
+      exit(EXIT_FAILURE);
+    }
+  }
+
+  int status;
+  while (wait(&status) > 0) {
+    printf("[Grate|getpid] terminated, status: %d\n", status);
+  }
+
+  return 0;
+}
diff --git a/c-grates/per-syscall-grates/getpid-grate/test/getpid-test.c b/c-grates/per-syscall-grates/getpid-grate/test/getpid-test.c
new file mode 100644
index 0000000..e4f3a64
--- /dev/null
+++ b/c-grates/per-syscall-grates/getpid-grate/test/getpid-test.c
@@ -0,0 +1,40 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <assert.h>
+
+int main() {
+    pid_t pid1, pid2;
+
+    // 1. Multiple calls should return the same PID
+    pid1 = getpid();
+    pid2 = getpid();
+    assert(pid1 == pid2);
+
+    // 2. PID should be positive
+    assert(pid1 > 0);
+
+    // 3. Fork and verify child has a different PID
+    pid_t child = fork();
+    assert(child >= 0);
+
+    if (child == 0) {
+        // Child process
+        pid_t child_pid = getpid();
+        pid_t parent_pid = getppid();
+
+        assert(child_pid != pid1);   // child PID differs from parent
+        assert(parent_pid == pid1);  // parent PID matches original
+
+        _exit(0);
+    } else {
+        // Parent process
+        int status;
+        waitpid(child, &status, 0);
+        assert(WIFEXITED(status));
+    }
+
+    printf("getpid() test passed (pid=%d)\n", pid1);
+    return 0;
+}
diff --git a/c-grates/per-syscall-grates/getuid-grate/build.conf b/c-grates/per-syscall-grates/getuid-grate/build.conf
new file mode 100644
index 0000000..fe09698
--- /dev/null
+++ b/c-grates/per-syscall-grates/getuid-grate/build.conf
@@ -0,0 +1 @@
+ENTRY=getuid-grate.c
diff --git a/c-grates/per-syscall-grates/getuid-grate/compile_grate.sh b/c-grates/per-syscall-grates/getuid-grate/compile_grate.sh
new file mode 100755
index 0000000..d433605
--- /dev/null
+++ b/c-grates/per-syscall-grates/getuid-grate/compile_grate.sh
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+cd "$(dirname "$0")"
+lind_compile -s --compile-grate --output-dir grates src/getuid-grate.c
diff --git a/c-grates/per-syscall-grates/getuid-grate/src/getuid-grate.c b/c-grates/per-syscall-grates/getuid-grate/src/getuid-grate.c
new file mode 100644
index 0000000..df40cd3
--- /dev/null
+++ b/c-grates/per-syscall-grates/getuid-grate/src/getuid-grate.c
@@ -0,0 +1,71 @@
+#include <errno.h>
+#include <lind_syscall.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define GETUID_SYSCALL 102
+
+int pass_fptr_to_wt(uint64_t fn_ptr_uint, uint64_t grateid, uint64_t arg1,
+                    uint64_t arg1cage, uint64_t arg2, uint64_t arg2cage,
+                    uint64_t arg3, uint64_t arg3cage, uint64_t arg4,
+                    uint64_t arg4cage, uint64_t arg5, uint64_t arg5cage,
+                    uint64_t arg6, uint64_t arg6cage) {
+  if (fn_ptr_uint == 0) {
+    return -1;
+  }
+
+  int (*fn)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+            uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+            uint64_t) =
+      (int (*)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+               uint64_t, uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
+               uint64_t))(uintptr_t)fn_ptr_uint;
+
+  return fn(grateid, arg1, arg1cage, arg2, arg2cage, arg3, arg3cage, arg4,
+            arg4cage, arg5, arg5cage, arg6, arg6cage);
+}
+
+int getuid_grate(uint64_t cageid, uint64_t arg1, uint64_t arg1cage,
+                 uint64_t arg2, uint64_t arg2cage, uint64_t arg3,
+                 uint64_t arg3cage, uint64_t arg4, uint64_t arg4cage,
+                 uint64_t arg5, uint64_t arg5cage, uint64_t arg6,
+                 uint64_t arg6cage) {
+
+  return make_threei_call(GETUID_SYSCALL, 0, cageid, arg1cage, arg1,
+                          arg1cage, arg2, arg2cage, arg3, arg3cage, arg4,
+                          arg4cage, arg5, arg5cage, arg6, arg6cage, 0);
+}
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <cage_file>\n", argv[0]);
+    exit(EXIT_FAILURE);
+  }
+  int grateid = getpid();
+
+  pid_t pid = fork();
+  if (pid < 0) {
+    perror("fork failed");
+    exit(EXIT_FAILURE);
+  } else if (pid == 0) {
+    int cageid = getpid();
+    
+    uint64_t fn_ptr_addr = (uint64_t)(uintptr_t)&getuid_grate;
+    int ret = register_handler(cageid, GETUID_SYSCALL, grateid, fn_ptr_addr);
+
+    if (execv(argv[1], &argv[1]) == -1) {
+      perror("execv failed");
+      exit(EXIT_FAILURE);
+    }
+  }
+
+  int status;
+  while (wait(&status) > 0) {
+    printf("[Grate|getuid] terminated, status: %d\n", status);
+  }
+
+  return 0;
+}
diff --git a/c-grates/per-syscall-grates/getuid-grate/test/getuid-test.c b/c-grates/per-syscall-grates/getuid-grate/test/getuid-test.c
new file mode 100644
index 0000000..bd8e774
--- /dev/null
+++ b/c-grates/per-syscall-grates/getuid-grate/test/getuid-test.c
@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <assert.h>
+
+int main() {
+    uid_t uid1, uid2;
+
+    // 1. Call getuid() twice — should be consistent
+    uid1 = getuid();
+    uid2 = getuid();
+    assert(uid1 == uid2);
+
+    // 2. UID should be non-negative
+    assert(uid1 >= 0);
+
+    // 3. Compare with geteuid() in normal (non-setuid) case
+    uid_t euid = geteuid();
+    if (uid1 != euid) {
+        printf("Note: real UID (%d) != effective UID (%d) (setuid context?)\n",
+               uid1, euid);
+    }
+
+    printf("getuid() test passed (uid=%d)\n", uid1);
+    return 0;
+}