diff --git a/main/eis.c b/main/eis.c
index 4ba43cd..833e67a 100644
--- a/main/eis.c
+++ b/main/eis.c
@@ -25,6 +25,7 @@ static struct {
 
 /* cell constant K (cm⁻¹), cached from NVS */
 static float cell_k_cached;
+static float cl_factor_cached;
 
 /* open-circuit calibration data */
 static struct {
@@ -593,7 +594,8 @@ int eis_has_open_cal(void)
     return ocal.valid;
 }
 
-#define NVS_CELLK_KEY "cell_k"
+#define NVS_CELLK_KEY    "cell_k"
+#define NVS_CLFACTOR_KEY "cl_factor"
 
 void eis_set_cell_k(float k)
 {
@@ -619,3 +621,28 @@ void eis_load_cell_k(void)
         cell_k_cached = 0.0f;
     nvs_close(h);
 }
+
+void eis_set_cl_factor(float f)
+{
+    cl_factor_cached = f;
+    nvs_handle_t h;
+    if (nvs_open(NVS_OCAL_NS, NVS_READWRITE, &h) != ESP_OK) return;
+    nvs_set_blob(h, NVS_CLFACTOR_KEY, &f, sizeof(f));
+    nvs_commit(h);
+    nvs_close(h);
+}
+
+float eis_get_cl_factor(void)
+{
+    return cl_factor_cached;
+}
+
+void eis_load_cl_factor(void)
+{
+    nvs_handle_t h;
+    if (nvs_open(NVS_OCAL_NS, NVS_READONLY, &h) != ESP_OK) return;
+    size_t len = sizeof(cl_factor_cached);
+    if (nvs_get_blob(h, NVS_CLFACTOR_KEY, &cl_factor_cached, &len) != ESP_OK || len != sizeof(cl_factor_cached))
+        cl_factor_cached = 0.0f;
+    nvs_close(h);
+}
diff --git a/main/eis.h b/main/eis.h
index c4cd28c..8fbb4d3 100644
--- a/main/eis.h
+++ b/main/eis.h
@@ -67,4 +67,8 @@ void  eis_set_cell_k(float k);
 float eis_get_cell_k(void);
 void  eis_load_cell_k(void);
 
+void  eis_set_cl_factor(float f);
+float eis_get_cl_factor(void);
+void  eis_load_cl_factor(void);
+
 #endif
diff --git a/main/eis4.c b/main/eis4.c
index 5385e6d..dace30e 100644
--- a/main/eis4.c
+++ b/main/eis4.c
@@ -56,6 +56,7 @@ void app_main(void)
     eis_default_config(&cfg);
     eis_load_open_cal();
     eis_load_cell_k();
+    eis_load_cl_factor();
     temp_init();
 
     esp_netif_init();
@@ -214,6 +215,16 @@ void app_main(void)
             send_cell_k(eis_get_cell_k());
             break;
 
+        case CMD_SET_CL_FACTOR:
+            eis_set_cl_factor(cmd.cl_factor);
+            send_cl_factor(cmd.cl_factor);
+            printf("Cl factor set: %.6f\n", cmd.cl_factor);
+            break;
+
+        case CMD_GET_CL_FACTOR:
+            send_cl_factor(eis_get_cl_factor());
+            break;
+
         case CMD_START_CL: {
             ClConfig cl_cfg;
             cl_cfg.v_cond    = cmd.cl.v_cond;
diff --git a/main/protocol.c b/main/protocol.c
index 08a9c47..504a6ed 100644
--- a/main/protocol.c
+++ b/main/protocol.c
@@ -341,6 +341,18 @@ int send_cell_k(float k)
     return send_sysex(sx, p);
 }
 
+/* ---- outbound: chlorine factor ---- */
+
+int send_cl_factor(float f)
+{
+    uint8_t sx[12];
+    uint16_t p = 0;
+    sx[p++] = 0xF0; sx[p++] = 0x7D; sx[p++] = RSP_CL_FACTOR;
+    encode_float(f, &sx[p]); p += 5;
+    sx[p++] = 0xF7;
+    return send_sysex(sx, p);
+}
+
 /* ---- outbound: reference collection ---- */
 
 int send_ref_frame(uint8_t mode, uint8_t rtia_idx)
diff --git a/main/protocol.h b/main/protocol.h
index 54b756b..8ab5709 100644
--- a/main/protocol.h
+++ b/main/protocol.h
@@ -26,6 +26,8 @@
 #define CMD_START_REFS    0x30
 #define CMD_GET_REFS      0x31
 #define CMD_CLEAR_REFS    0x32
+#define CMD_SET_CL_FACTOR 0x33
+#define CMD_GET_CL_FACTOR 0x34
 
 /* Session sync commands (0x4x) */
 #define CMD_SESSION_CREATE  0x40
@@ -56,6 +58,7 @@
 #define RSP_REF_LP_RANGE 0x21
 #define RSP_REFS_DONE   0x22
 #define RSP_REF_STATUS  0x23
+#define RSP_CL_FACTOR   0x24
 
 /* Session sync responses (0x4x) */
 #define RSP_SESSION_CREATED  0x40
@@ -81,6 +84,7 @@ typedef struct {
         struct { float stabilize_s; } ph;
         struct { float v_mv; float duration_s; } clean;
         float cell_k;
+        float cl_factor;
         struct { uint8_t name_len; char name[MAX_SESSION_NAME]; } session_create;
         struct { uint8_t id; } session_switch;
         struct { uint8_t id; uint8_t name_len; char name[MAX_SESSION_NAME]; } session_rename;
@@ -132,6 +136,9 @@ int send_temp(float temp_c);
 /* outbound: cell constant */
 int send_cell_k(float k);
 
+/* outbound: chlorine factor */
+int send_cl_factor(float f);
+
 /* outbound: reference collection */
 int send_ref_frame(uint8_t mode, uint8_t rtia_idx);
 int send_ref_lp_range(uint8_t mode, uint8_t low_idx, uint8_t high_idx);
diff --git a/main/wifi_transport.c b/main/wifi_transport.c
index df02497..1d05ba4 100644
--- a/main/wifi_transport.c
+++ b/main/wifi_transport.c
@@ -166,6 +166,10 @@ static void parse_udp_sysex(const uint8_t *data, uint16_t len)
         if (len < 8) return;
         cmd.cell_k = decode_float(&data[3]);
         break;
+    case CMD_SET_CL_FACTOR:
+        if (len < 8) return;
+        cmd.cl_factor = decode_float(&data[3]);
+        break;
     case CMD_SESSION_CREATE:
         if (len < 5) return;
         cmd.session_create.name_len = data[3] & 0x7F;
@@ -192,6 +196,7 @@ static void parse_udp_sysex(const uint8_t *data, uint16_t len)
     case CMD_STOP_AMP:
     case CMD_GET_TEMP:
     case CMD_GET_CELL_K:
+    case CMD_GET_CL_FACTOR:
     case CMD_START_REFS:
     case CMD_GET_REFS:
     case CMD_CLEAR_REFS: