diff --git a/tests/integration.c b/tests/integration.c
index 4c2ba65..3b99579 100644
--- a/tests/integration.c
+++ b/tests/integration.c
@@ -7,6 +7,41 @@
 #include <string.h>
 #include <stdarg.h>
 #include <fcntl.h>
+#include <jack/jack.h>
+#include <math.h>
+
+/* static variables for passthrough test */
+static jack_port_t *passthrough_output_port = NULL;
+static jack_port_t *passthrough_input_port = NULL;
+static float passthrough_phase = 0.0f;
+static float passthrough_freq = 440.0f;
+static int passthrough_sample_rate = 0;
+static long passthrough_total_samples = 0;
+static double passthrough_sum_sq = 0.0;
+static volatile int passthrough_done = 0;
+
+static int passthrough_process(jack_nframes_t nframes, void *arg) {
+    (void)arg;
+    jack_default_audio_sample_t *out =
+        (jack_default_audio_sample_t *)jack_port_get_buffer(passthrough_output_port, nframes);
+    jack_default_audio_sample_t *in =
+        (jack_default_audio_sample_t *)jack_port_get_buffer(passthrough_input_port, nframes);
+    if (!out || !in) return 0;
+    float *outf = out;
+    const float *inf = in;
+    for (jack_nframes_t i = 0; i < nframes; i++) {
+        float val = sinf(passthrough_phase);
+        outf[i] = val;
+        passthrough_phase += 2.0f * (float)M_PI * passthrough_freq / passthrough_sample_rate;
+        if (passthrough_phase > 2.0f * M_PI) passthrough_phase -= 2.0f * M_PI;
+        passthrough_sum_sq += (double)inf[i] * (double)inf[i];
+        passthrough_total_samples++;
+    }
+    if (passthrough_total_samples >= passthrough_sample_rate * 2) {
+        passthrough_done = 1;
+    }
+    return 0;
+}
 
 /*
  * Integration test for the JACK looper.
@@ -173,51 +208,69 @@ static void test_clock_continue(void) {
 
 static int test_audio_pass_through(void) {
     printf("Test: audio pass‑through (connectivity)\n");
-
-    /* check required tools */
-    if (system("which jack_lsp >/dev/null 2>&1") != 0) {
-        fprintf(stderr, "  SKIP: jack_lsp not installed\n");
+    jack_client_t *client;
+    jack_status_t status;
+    client = jack_client_open("test_passthrough", JackNoStartServer, &status);
+    if (client == NULL) {
+        fprintf(stderr, "  SKIP: cannot open JACK client (server not running?)\n");
         return 1;
     }
-    if (system("which jack_connect >/dev/null 2>&1") != 0) {
-        fprintf(stderr, "  SKIP: jack_connect not installed\n");
+    jack_port_t *output_port = jack_port_register(client, "output",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsOutput, 0);
+    jack_port_t *input_port = jack_port_register(client, "input",
+                           JACK_DEFAULT_AUDIO_TYPE,
+                           JackPortIsInput, 0);
+    if (!output_port || !input_port) {
+        fprintf(stderr, "  FAIL: could not register ports\n");
+        jack_client_close(client);
         return 1;
     }
-
-    pid_t pid = start_looper();
-    if (pid < 0) {
-        fprintf(stderr, "FAIL: could not start looper\n");
+    usleep(200000);
+    const char *looper_input = "looper:input";
+    const char *looper_output = "looper:output";
+    char my_output[64], my_input[64];
+    snprintf(my_output, sizeof(my_output), "test_passthrough:output");
+    snprintf(my_input, sizeof(my_input), "test_passthrough:input");
+    if (jack_connect(client, my_output, looper_input) != 0) {
+        fprintf(stderr, "  FAIL: cannot connect test_passthrough:output -> looper:input\n");
+        jack_client_close(client);
         return 1;
     }
-
-    /* connect looper input to a dummy JACK source? No sine needed.
-       Instead just verify ports appear. */
-    char buf[512];
-    snprintf(buf, sizeof(buf),
-             "jack_lsp -c looper 2>/dev/null | grep -q -E '^looper:'");
-    if (system(buf) != 0) {
-        fprintf(stderr, "FAIL: looper ports not visible\n");
-        kill(pid, SIGTERM);
-        waitpid(pid, NULL, 0);
+    if (jack_connect(client, looper_output, my_input) != 0) {
+        fprintf(stderr, "  FAIL: cannot connect looper:output -> test_passthrough:input\n");
+        jack_client_close(client);
         return 1;
     }
-
-    /* try connecting to itself (loopback) as a connectivity test */
-    if (system("jack_connect looper:output looper:input 2>/dev/null") != 0) {
-        fprintf(stderr, "FAIL: could not connect looper:output -> looper:input\n");
-        kill(pid, SIGTERM);
-        waitpid(pid, NULL, 0);
+    passthrough_output_port = output_port;
+    passthrough_input_port = input_port;
+    passthrough_phase = 0.0f;
+    passthrough_freq = 440.0f;
+    passthrough_sample_rate = jack_get_sample_rate(client);
+    passthrough_total_samples = 0;
+    passthrough_sum_sq = 0.0;
+    passthrough_done = 0;
+    jack_set_process_callback(client, passthrough_process, NULL);
+    if (jack_activate(client) != 0) {
+        fprintf(stderr, "  FAIL: cannot activate client\n");
+        jack_client_close(client);
         return 1;
     }
-
-    /* wait briefly then disconnect */
-    sleep(1);
-    system("jack_disconnect looper:output looper:input 2>/dev/null");
-
-    kill(pid, SIGTERM);
-    waitpid(pid, NULL, 0);
-
-    printf("  PASS (connectivity established)\n");
+    usleep(2200000); /* 2.2 seconds */
+    int saw_input = passthrough_done;
+    double rms = passthrough_total_samples > 0 ?
+                 sqrt(passthrough_sum_sq / passthrough_total_samples) : 0.0;
+    jack_deactivate(client);
+    jack_client_close(client);
+    if (!saw_input) {
+        fprintf(stderr, "  FAIL: looper did not produce output (no callback run?)\n");
+        return 1;
+    }
+    if (rms < 0.001) {
+        fprintf(stderr, "  FAIL: looper output RMS too small (%.6f)\n", rms);
+        return 1;
+    }
+    printf("  PASS (RMS %.6f)\n", rms);
     return 0;
 }