diff --git a/src/logos_blockchain_module.cpp b/src/logos_blockchain_module.cpp
index 6f93f43..080df86 100644
--- a/src/logos_blockchain_module.cpp
+++ b/src/logos_blockchain_module.cpp
@@ -939,23 +939,15 @@ StdLogosResult LogosBlockchainModule::wallet_get_claimable_vouchers() const {
 // Blend
 
 StdLogosResult LogosBlockchainModule::blend_join_as_core_node(
-    const std::string& provider_id_hex,
-    const std::string& zk_id_hex,
-    const std::string& locked_note_id_hex,
-    const std::vector<std::string>& locators
+    const std::string& locator,
+    const std::string& locked_note_id_hex
 ) const {
     if (!node) {
         return result::err("The node is not running.");
     }
 
-    const std::vector<uint8_t> provider_id_bytes = parse_address_hex(provider_id_hex);
-    if (provider_id_bytes.empty() || static_cast<int>(provider_id_bytes.size()) != ADDRESS_BYTES) {
-        return result::err("Invalid provider_id_hex (64 hex characters required).");
-    }
-
-    const std::vector<uint8_t> zk_id_bytes = parse_address_hex(zk_id_hex);
-    if (zk_id_bytes.empty() || static_cast<int>(zk_id_bytes.size()) != ADDRESS_BYTES) {
-        return result::err("Invalid zk_id_hex (64 hex characters required).");
+    if (locator.empty()) {
+        return result::err("Invalid locator (must not be empty).");
     }
 
     const std::vector<uint8_t> locked_note_id_bytes = parse_address_hex(locked_note_id_hex);
@@ -963,20 +955,10 @@ StdLogosResult LogosBlockchainModule::blend_join_as_core_node(
         return result::err("Invalid locked_note_id_hex (64 hex characters required).");
     }
 
-    // locators_ptrs holds raw pointers into the std::strings (valid as long as `locators` lives).
-    std::vector<const char*> locators_ptrs;
-    locators_ptrs.reserve(locators.size());
-    for (const std::string& locator : locators) {
-        locators_ptrs.push_back(locator.c_str());
-    }
-
     auto [value, error] = ::blend_join_as_core_node(
         node,
-        provider_id_bytes.data(),
-        zk_id_bytes.data(),
-        locked_note_id_bytes.data(),
-        locators_ptrs.data(),
-        locators_ptrs.size()
+        locator.c_str(),
+        locked_note_id_bytes.data()
     );
     if (!is_ok(&error)) {
         return result::err(operation_status::take_message(error));
diff --git a/src/logos_blockchain_module.h b/src/logos_blockchain_module.h
index 22cf848..b3e9d6d 100644
--- a/src/logos_blockchain_module.h
+++ b/src/logos_blockchain_module.h
@@ -130,10 +130,8 @@ public:
 
     // Blend
     [[nodiscard]] StdLogosResult blend_join_as_core_node(
-        const std::string& provider_id_hex,
-        const std::string& zk_id_hex,
-        const std::string& locked_note_id_hex,
-        const std::vector<std::string>& locators
+        const std::string& locator,
+        const std::string& locked_note_id_hex
     ) const;
 
     // Explorer
diff --git a/tests/mocks/mock_logos_blockchain.cpp b/tests/mocks/mock_logos_blockchain.cpp
index c0d61e7..15829d7 100644
--- a/tests/mocks/mock_logos_blockchain.cpp
+++ b/tests/mocks/mock_logos_blockchain.cpp
@@ -272,11 +272,8 @@ FfiChannelDepositResult channel_deposit_with_notes(
 
 BlendHashResult blend_join_as_core_node(
     LogosBlockchainNode* node,
-    const uint8_t* provider_id,
-    const uint8_t* zk_id,
-    const uint8_t* locked_note_id,
-    const char** locators,
-    size_t locators_count)
+    const char* locator,
+    const uint8_t* locked_note_id)
 {
     LOGOS_CMOCK_RECORD("blend_join_as_core_node");
     BlendHashResult result;
diff --git a/tests/stubs/logos_blockchain.h b/tests/stubs/logos_blockchain.h
index 13477ca..b2cd8fa 100644
--- a/tests/stubs/logos_blockchain.h
+++ b/tests/stubs/logos_blockchain.h
@@ -221,11 +221,8 @@ OperationStatus free_claimable_vouchers(ClaimableVouchers vouchers);
 // Blend
 BlendHashResult blend_join_as_core_node(
     LogosBlockchainNode* node,
-    const uint8_t* provider_id,
-    const uint8_t* zk_id,
-    const uint8_t* locked_note_id,
-    const char** locators,
-    size_t locators_count);
+    const char* locator,
+    const uint8_t* locked_note_id);
 
 // Explorer
 StringResult get_block(LogosBlockchainNode* node, const HeaderId* header_id);
diff --git a/tests/test_blockchain.cpp b/tests/test_blockchain.cpp
index ad2512f..3493ceb 100644
--- a/tests/test_blockchain.cpp
+++ b/tests/test_blockchain.cpp
@@ -292,7 +292,7 @@ LOGOS_TEST(wallet_get_known_addresses_without_node_returns_error) {
 LOGOS_TEST(blend_join_as_core_node_without_node_returns_error) {
     auto t = LogosTestContext("blockchain_module");
     LogosBlockchainModule module;
-    StdLogosResult result = module.blend_join_as_core_node(VALID_HEX, VALID_HEX, VALID_HEX, {"locator1"});
+    StdLogosResult result = module.blend_join_as_core_node("locator1", VALID_HEX);
     LOGOS_ASSERT_FALSE(result.success);
     LOGOS_ASSERT_TRUE(contains(result.error, "not running"));
 }
@@ -475,27 +475,15 @@ LOGOS_TEST(wallet_transfer_funds_rejects_invalid_optional_tip) {
 
 // blend_join_as_core_node validation
 
-LOGOS_TEST(blend_join_rejects_invalid_provider_id) {
+LOGOS_TEST(blend_join_rejects_empty_locator) {
     auto t = LogosTestContext("blockchain_module");
     TempDir tmpDir;
     auto* module = createStartedModule(t, tmpDir);
     LOGOS_ASSERT_TRUE(module != nullptr);
 
-    StdLogosResult result = module->blend_join_as_core_node("short", VALID_HEX, VALID_HEX, {});
+    StdLogosResult result = module->blend_join_as_core_node("", VALID_HEX);
     LOGOS_ASSERT_FALSE(result.success);
-    LOGOS_ASSERT_TRUE(contains(result.error, "provider_id"));
-    delete module;
-}
-
-LOGOS_TEST(blend_join_rejects_invalid_zk_id) {
-    auto t = LogosTestContext("blockchain_module");
-    TempDir tmpDir;
-    auto* module = createStartedModule(t, tmpDir);
-    LOGOS_ASSERT_TRUE(module != nullptr);
-
-    StdLogosResult result = module->blend_join_as_core_node(VALID_HEX, "short", VALID_HEX, {});
-    LOGOS_ASSERT_FALSE(result.success);
-    LOGOS_ASSERT_TRUE(contains(result.error, "zk_id"));
+    LOGOS_ASSERT_TRUE(contains(result.error, "locator"));
     delete module;
 }
 
@@ -505,7 +493,7 @@ LOGOS_TEST(blend_join_rejects_invalid_locked_note_id) {
     auto* module = createStartedModule(t, tmpDir);
     LOGOS_ASSERT_TRUE(module != nullptr);
 
-    StdLogosResult result = module->blend_join_as_core_node(VALID_HEX, VALID_HEX, "short", {});
+    StdLogosResult result = module->blend_join_as_core_node("locator1", "short");
     LOGOS_ASSERT_FALSE(result.success);
     LOGOS_ASSERT_TRUE(contains(result.error, "locked_note_id"));
     delete module;
@@ -1035,8 +1023,7 @@ LOGOS_TEST(blend_join_as_core_node_returns_declaration_id) {
 
     t.mockCFunction("blend_join_as_core_node_error").returns(0);
 
-    std::vector<std::string> locators = {"locator1", "locator2"};
-    StdLogosResult result = module->blend_join_as_core_node(VALID_HEX, VALID_HEX, VALID_HEX, locators);
+    StdLogosResult result = module->blend_join_as_core_node("locator1", VALID_HEX);
     LOGOS_ASSERT_TRUE(result.success);
     // Mock fills hash with 0xCD -> hex "cdcd...cd" (64 chars)
     std::string declarationId = result.value.get<std::string>();
@@ -1054,7 +1041,7 @@ LOGOS_TEST(blend_join_as_core_node_returns_error_on_ffi_failure) {
 
     t.mockCFunction("blend_join_as_core_node_error").returns(1);
 
-    StdLogosResult result = module->blend_join_as_core_node(VALID_HEX, VALID_HEX, VALID_HEX, {});
+    StdLogosResult result = module->blend_join_as_core_node("locator1", VALID_HEX);
     LOGOS_ASSERT_FALSE(result.success);
     delete module;
 }