diff --git a/user/siginfotest.c b/user/siginfotest.c
new file mode 100644
index 0000000..f675680
--- /dev/null
+++ b/user/siginfotest.c
@@ -0,0 +1,151 @@
+#include "ulib.h"
+
+/*
+ * Boot-time driver for real SA_SIGINFO delivery (signalnum.h's
+ * sigFlagSigInfo/SigInfo, signal.c's sigConsumePending) -- proves the
+ * extra (SigInfo*, void*) arguments a sigFlagSigInfo handler receives
+ * carry genuinely accurate data, not just a valid-looking pointer, in BOTH
+ * directions this kernel ever populates SigInfo from:
+ *
+ *   1. si_pid on a user-sent signal (sysSigSend, syscall.c): spawns
+ *      siginfotarget.c and sends it a real sigUsr1 through userSigSend;
+ *      siginfotarget's own handler verifies the si_pid it received is
+ *      genuinely THIS process's pid (passed as an argv string so there is
+ *      no ambiguity about what "correct" means), not just some nonzero
+ *      value that happened to be lying around.
+ *
+ *   2. si_code/si_pid/si_status on a real, kernel-raised SIGCHLD
+ *      (threadExit, sched.c): installs its OWN sigFlagSigInfo handler for
+ *      sigChld before ever spawning siginfotarget (the same race sigchldtest.c
+ *      already had to close with a pre-spawn install), then -- once
+ *      siginfotarget's own round trip above completes and it exits with a
+ *      distinctive code (77) -- verifies the real SIGCHLD its own handler
+ *      received reports siCodeChldExited, the CHILD's real pid, and the
+ *      CHILD's real exit status, exactly matching what userWait's
+ *      synchronous reap independently confirms right after.
+ *
+ * Reuses siginfotarget.c's own ready-pipe rendezvous (sigtest.c's pattern)
+ * for the same reason sigtest.c needed it: sigUsr1's default disposition
+ * is Terminate, so sending it before siginfotarget has actually installed
+ * its handler would kill it instead of proving anything.
+ */
+
+static volatile int chldFired = 0;
+static volatile int chldCode = -1;
+static volatile int chldPid = -1;
+static volatile int chldStatus = -1;
+
+static void onChld(int signum, SigInfo* info, void* context)
+{
+    (void)signum;
+    (void)context;
+    chldCode = info->siCode;
+    chldPid = info->siPid;
+    chldStatus = info->siStatus;
+    chldFired = 1;
+    print("siginfotest: sigchld-info-handler-fired siCode=");
+    printDec(info->siCode);
+    print(" siPid=");
+    printDec(info->siPid);
+    print(" siStatus=");
+    printDec(info->siStatus);
+    print("\n");
+}
+
+int main(void)
+{
+    print("siginfotest: start, pid=");
+    printDec(userGetpid());
+    print("\n");
+
+    /* Installed BEFORE siginfotarget even exists, exactly like
+       sigchldtest.c's own onChld -- a real SIGCHLD can arrive the instant
+       siginfotarget dies, which this process has no other way to order
+       itself ahead of. */
+    if (userSigActionInfo(sigChld, onChld, 0, sigFlagSigInfo) == (long)sigSetFailed) {
+        print("siginfotest: FAIL install siginfo sigchld handler\n");
+        return 1;
+    }
+
+    long readyHandle = userPipeCreate();
+    if (readyHandle < 0) {
+        print("siginfotest: FAIL create ready pipe\n");
+        return 1;
+    }
+
+    /* Attach as reader before siginfotarget exists -- same detached-slot
+       race sigtest.c's own comment documents avoiding. */
+    long readyFd = userPipeAttach(readyHandle, 0);
+    if (readyFd < 0) {
+        print("siginfotest: FAIL attach ready pipe\n");
+        return 1;
+    }
+
+    char readyHandleStr[24];
+    decToString(readyHandle, readyHandleStr);
+    char ownPidStr[24];
+    decToString(userGetpid(), ownPidStr);
+
+    char* targetArgv[] = { "/bin/siginfotarget", readyHandleStr, ownPidStr, 0 };
+    long target = userSpawn("/bin/siginfotarget", targetArgv);
+    if (target < 0) {
+        print("siginfotest: FAIL spawn siginfotarget\n");
+        return 1;
+    }
+
+    char readyByte;
+    if (userRead((int)readyFd, &readyByte, 1) != 1) {
+        print("siginfotest: FAIL read ready byte\n");
+        return 1;
+    }
+    userClose((int)readyFd);
+
+    if (userSigSend(target, sigUsr1) != 0) {
+        print("siginfotest: FAIL send sigUsr1 to siginfotarget\n");
+        return 1;
+    }
+    print("siginfotest: sent sigUsr1 to siginfotarget\n");
+
+    /* Bounded poll for the real, kernel-raised SIGCHLD, same idiom
+       sigchldtest.c already uses for the same reason (no timing guess,
+       just enough sleep-wake cycles for the return-to-ring3 pending-signal
+       scan, isr.c, to notice it whenever it actually lands). */
+    for (int i = 0; i < 80 && !chldFired; i++)
+        userSleep(20);
+
+    if (!chldFired) {
+        print("siginfotest: FAIL sigchld siginfo handler never fired\n");
+        return 1;
+    }
+    if (chldCode != siCodeChldExited) {
+        print("siginfotest: FAIL expected siCodeChldExited\n");
+        return 1;
+    }
+    if (chldPid != (int)target) {
+        print("siginfotest: FAIL si_pid=");
+        printDec(chldPid);
+        print(" does not match real child pid=");
+        printDec(target);
+        print("\n");
+        return 1;
+    }
+    if (chldStatus != 77) {
+        print("siginfotest: FAIL si_status=");
+        printDec(chldStatus);
+        print(" does not match real child exit code 77\n");
+        return 1;
+    }
+    print("siginfotest: sigchld-siginfo-accurate-ok\n");
+
+    long status = userWait(target);
+    print("siginfotest: siginfotarget exit status=");
+    printDec(status);
+    print("\n");
+    if (status != 77) {
+        print("siginfotest: FAIL expected siginfotarget exit status 77\n");
+        return 1;
+    }
+    print("siginfotest: siginfo-roundtrip-ok\n");
+
+    return 0;
+}