diff --git a/compiler/code-gen/vertex-compiler.cpp b/compiler/code-gen/vertex-compiler.cpp
index a48574eeda..0ca596f4c0 100644
--- a/compiler/code-gen/vertex-compiler.cpp
+++ b/compiler/code-gen/vertex-compiler.cpp
@@ -917,7 +917,7 @@ void compile_func_call(VertexAdaptor<op_func_call> root, CodeGenerator &W, func_
     }
 
     if (is_function_call_should_be_tracked(func)) {
-      W << "SAVE_BUILTIN_CALL_STATS(\"" << func->name << "\", (";
+      W << "DUMP_BUILTIN_CALL_STATS(\"" << func->name << "\", (";
     }
 
     if (mode == func_call_mode::fork_call) {
diff --git a/runtime-light/stdlib/diagnostics/functions-call-stats.h b/runtime-light/stdlib/diagnostics/functions-call-stats.h
new file mode 100644
index 0000000000..c1914f1495
--- /dev/null
+++ b/runtime-light/stdlib/diagnostics/functions-call-stats.h
@@ -0,0 +1,9 @@
+// Compiler for PHP (aka KPHP)
+// Copyright (c) 2026 LLC «V Kontakte»
+// Distributed under the GPL v3 License, see LICENSE.notice.txt
+
+#pragma once
+
+#include "runtime-light/stdlib/diagnostics/logs.h"
+
+#define DUMP_BUILTIN_CALL_STATS(builtin_name, builtin_call) (kphp::log::debug("built-in called: " builtin_name), builtin_call)
diff --git a/runtime/runtime-builtin-stats.h b/runtime/runtime-builtin-stats.h
index 1964b4d1a0..e8a0306a38 100644
--- a/runtime/runtime-builtin-stats.h
+++ b/runtime/runtime-builtin-stats.h
@@ -49,6 +49,6 @@ inline void save_virtual_builtin_call_stats(const kphp::stl::string<kphp::memory
 }
 } // namespace runtime_builtins_stats
 
-#define SAVE_BUILTIN_CALL_STATS(builtin_name, builtin_call)                                                                                                    \
+#define DUMP_BUILTIN_CALL_STATS(builtin_name, builtin_call)                                                                                                    \
   (!runtime_builtins_stats::request_stats.has_value() ? 0 : (*runtime_builtins_stats::request_stats).builtin_stats[std::string_view(builtin_name)]++,          \
    builtin_call)
diff --git a/tests/kphp_tester.py b/tests/kphp_tester.py
index 810ce4d209..fe653525d7 100755
--- a/tests/kphp_tester.py
+++ b/tests/kphp_tester.py
@@ -75,6 +75,7 @@ def set_up_env_for_k2(self):
         self.env_vars["KPHP_ENABLE_GLOBAL_VARS_MEMORY_STATS"] = "0"
         self.env_vars["KPHP_PROFILER"] = "0"
         self.env_vars["KPHP_FORCE_LINK_RUNTIME"] = "1"
+        self.env_vars["KPHP_TRACKED_BUILTINS_LIST"] = KphpRunOnce.K2_KPHP_TRACKED_BUILTINS_LIST
 
 
 def make_test_file(file_path, test_tmp_dir, test_tags):
diff --git a/tests/python/lib/k2_kphp_tracked_builtins_list.txt b/tests/python/lib/k2_kphp_tracked_builtins_list.txt
new file mode 100644
index 0000000000..137d468b5e
--- /dev/null
+++ b/tests/python/lib/k2_kphp_tracked_builtins_list.txt
@@ -0,0 +1,456 @@
+_exception_set_location
+_explode_tuple2
+_explode_tuple3
+_explode_tuple4
+_tmp_substr
+_tmp_trim
+abs
+acos
+addcslashes
+addslashes
+array_chunk
+array_column
+array_combine
+array_count_values
+array_diff
+array_diff_assoc
+array_diff_key
+array_fill
+array_fill_keys
+array_filter
+array_filter_by_key
+array_find
+array_first_key
+array_first_value
+array_flip
+array_intersect
+array_intersect_assoc
+array_intersect_key
+array_is_vector
+array_key_exists
+array_key_first
+array_key_last
+array_keys
+array_keys_as_ints
+array_keys_as_strings
+array_last_key
+array_last_value
+array_map
+array_merge
+array_merge_into
+array_merge_recursive
+array_merge_spread
+array_pad
+array_pop
+array_push
+array_rand
+array_reduce
+array_replace
+array_reserve
+array_reserve_from
+array_reserve_map_int_keys
+array_reserve_map_string_keys
+array_reserve_vector
+array_reverse
+array_search
+array_shift
+array_slice
+array_splice
+array_sum
+array_swap_int_keys
+array_unique
+array_unset
+array_unshift
+array_values
+arsort
+asort
+atan
+atan2
+base_convert
+base64_decode
+base64_encode
+basename
+bcadd
+bccomp
+bcdiv
+bcmod
+bcmul
+bcpow
+bcscale
+bcsqrt
+bcsub
+bin2hex
+bindec
+ceil
+checkdate
+chr
+CompileTimeLocation$$__construct
+CompileTimeLocation$$calculate
+confdata_get_value
+confdata_get_values_by_predefined_wildcard
+cos
+count
+count_chars
+crc32
+create_vector
+critical_error
+ctype_alnum
+ctype_digit
+ctype_xdigit
+curl_close
+curl_errno
+curl_error
+curl_exec
+curl_exec_concurrently
+curl_getinfo
+curl_init
+curl_multi_add_handle
+curl_multi_close
+curl_multi_errno
+curl_multi_exec
+curl_multi_getcontent
+curl_multi_info_read
+curl_multi_init
+curl_multi_remove_handle
+curl_multi_select
+curl_multi_setopt
+curl_multi_strerror
+curl_setopt
+curl_setopt_array
+date
+date_default_timezone_get
+date_default_timezone_set
+DateInterval$$__construct
+DateInterval$$createFromDateString
+DateInterval$$format
+DateTime$$__construct
+DateTime$$add
+DateTime$$createFromFormat
+DateTime$$diff
+DateTime$$format
+DateTime$$getTimestamp
+DateTime$$modify
+DateTime$$setDate
+DateTime$$setTime
+DateTime$$setTimestamp
+DateTimeImmutable$$__construct
+DateTimeImmutable$$add
+DateTimeImmutable$$createFromFormat
+DateTimeImmutable$$diff
+DateTimeImmutable$$format
+DateTimeImmutable$$getTimestamp
+DateTimeImmutable$$modify
+DateTimeImmutable$$setTime
+DateTimeImmutable$$setTimestamp
+DateTimeZone$$__construct
+debug_backtrace
+decbin
+dechex
+deflate_add
+deflate_init
+deg2rad
+die
+echo
+empty
+err
+error_get_last
+error_reporting
+Error$$getCode
+Error$$getFile
+Error$$getLine
+Error$$getMessage
+Error$$getTrace
+Error$$getTraceAsString
+estimate_memory_usage
+Exception$$__construct
+Exception$$getCode
+Exception$$getFile
+Exception$$getLine
+Exception$$getMessage
+Exception$$getTrace
+Exception$$getTraceAsString
+exit
+exp
+explode
+extract_kphp_rpc_response_extra_info
+fclose
+fetch_double
+fetch_int
+fetch_long
+fetch_string
+fflush
+file
+file_get_contents
+filesize
+floor
+fmod
+fopen
+fprintf
+fread
+function_exists
+fwrite
+get_class
+get_engine_version
+get_hash_of_class
+get_job_workers_number
+get_kphp_cluster_name
+get_running_fork_id
+getdate
+getKeyByPos
+gettype
+getValueByPos
+gmdate
+gmmktime
+gzcompress
+gzdecode
+gzencode
+gzinflate
+gzuncompress
+hash
+hash_equals
+hash_hmac
+header
+headers_list
+hex2bin
+hexdec
+hrtime
+html_entity_decode
+htmlentities
+htmlspecialchars
+htmlspecialchars_decode
+http_build_query
+iconv
+implode
+in_array
+inet_pton
+ini_get
+instance_cache_delete
+instance_cache_fetch
+instance_cache_store
+instance_cache_update_ttl
+instance_cast
+instance_deserialize
+instance_deserialize_safe
+instance_serialize
+instance_to_array
+ip2long
+ip2ulong
+is_array
+is_bool
+is_confdata_loaded
+is_double
+is_file
+is_finite
+is_float
+is_infinite
+is_int
+is_integer
+is_kphp_job_workers_enabled
+is_nan
+is_null
+is_numeric
+is_object
+is_scalar
+is_string
+json_decode
+json_encode
+JsonEncoder$$from_json_impl
+JsonEncoder$$getLastError
+JsonEncoder$$to_json_impl
+kml_get_custom_property
+kml_xgboost_predict_matrix
+kphp_get_runtime_config
+kphp_set_context_on_error
+KphpJobWorkerResponseError$$getError
+KphpJobWorkerResponseError$$getErrorCode
+KphpRpcRequestsExtraInfo$$get
+krsort
+ksort
+lcfirst
+lcg_value
+levenshtein
+likely
+log
+long2ip
+ltrim
+make_clone
+max
+mb_check_encoding
+mb_stripos
+mb_strlen
+mb_strpos
+mb_strtolower
+mb_strtoupper
+mb_substr
+md5
+memory_get_detailed_stats
+memory_get_peak_usage
+memory_get_total_usage
+memory_get_usage
+microtime
+min
+mktime
+msgpack_deserialize
+msgpack_serialize
+mt_getrandmax
+mt_rand
+mt_srand
+natsort
+nl2br
+numa_get_bound_node
+number_format
+ob_clean
+ob_end_clean
+ob_end_flush
+ob_get_clean
+ob_get_contents
+ob_get_length
+ob_get_level
+ob_start
+openssl_cipher_iv_length
+openssl_decrypt
+openssl_encrypt
+openssl_get_cipher_methods
+openssl_pkey_get_private
+openssl_pkey_get_public
+openssl_private_decrypt
+openssl_public_encrypt
+openssl_random_pseudo_bytes
+openssl_sign
+openssl_verify
+openssl_x509_parse
+ord
+pack
+parse_str
+parse_url
+php_sapi_name
+php_uname
+posix_getpid
+posix_getpwuid
+posix_getuid
+preg_match
+preg_match_all
+preg_quote
+preg_replace
+preg_replace_callback
+print
+print_r
+printf
+rand
+range
+rawurldecode
+rawurlencode
+realpath
+register_kphp_on_oom_callback
+register_kphp_on_warning_callback
+register_shutdown_function
+round
+rpc_clean
+rpc_parse
+rpc_queue_create
+rpc_queue_empty
+rpc_queue_next
+rpc_server_fetch_request
+rpc_server_store_response
+rpc_tl_pending_queries_count
+rpc_tl_query
+rpc_tl_query_result
+rpc_tl_query_result_synchronously
+rsort
+rtrim
+sched_yield
+sched_yield_sleep
+serialize
+set_detect_incorrect_encoding_names_warning
+set_fail_rpc_on_int32_overflow
+set_json_log_on_timeout_mode
+set_migration_php8_warning
+setlocale
+sha1
+shuffle
+similar_text
+sin
+sizeof
+sleep
+sort
+sprintf
+sqrt
+store_error
+store_int
+store_long
+store_string
+str_ends_with
+str_ireplace
+str_pad
+str_repeat
+str_replace
+str_split
+str_starts_with
+strcasecmp
+strcmp
+stream_socket_client
+strip_tags
+stripos
+stripslashes
+stristr
+strlen
+strnatcmp
+strncmp
+strpos
+strrev
+strripos
+strrpos
+strstr
+strtolower
+strtotime
+strtoupper
+strtr
+substr
+substr_compare
+substr_count
+substr_replace
+tan
+time
+to_array_debug
+trim
+typed_rpc_tl_query
+typed_rpc_tl_query_result
+typed_rpc_tl_query_result_synchronously
+uasort
+UberH3$$geoToH3
+UberH3$$h3ToParent
+ucfirst
+ucwords
+uksort
+uniqid
+unlink
+unpack
+unserialize
+urldecode
+urlencode
+usleep
+usort
+var_dump
+var_export
+vk_json_encode
+vk_json_encode_safe
+vk_sp_deunicode
+vk_sp_simplify
+vk_sp_to_lower
+vk_sp_to_upper
+vk_stats_hll_count
+vk_stats_hll_merge
+vk_utf8_to_win
+vk_win_to_utf8
+vsprintf
+wait
+wait_concurrently
+wait_multi
+wait_queue_create
+wait_queue_empty
+wait_queue_next
+wait_queue_push
+warning
+wordwrap
+zstd_compress
+zstd_uncompress
diff --git a/tests/python/lib/kphp_run_once.py b/tests/python/lib/kphp_run_once.py
index 1f8596717e..49db1d4885 100644
--- a/tests/python/lib/kphp_run_once.py
+++ b/tests/python/lib/kphp_run_once.py
@@ -1,4 +1,7 @@
+import collections
 import os
+import pathlib
+import re
 import shutil
 import subprocess
 import sys
@@ -8,6 +11,10 @@
 
 
 class KphpRunOnce(KphpBuilder):
+    K2_KPHP_TRACKED_BUILTINS_LIST_PATH = pathlib.Path(__file__).parent / "k2_kphp_tracked_builtins_list.txt"
+    K2_KPHP_TRACKED_BUILTINS_LIST = K2_KPHP_TRACKED_BUILTINS_LIST_PATH.read_text()
+    K2_BUILTIN_CALLED_MSG_RE = re.compile(b"built-in called: ([\w$]+)")
+
     def __init__(self, php_script_path, artifacts_dir, working_dir, php_bin,
                  extra_include_dirs=None, vkext_dir=None, use_nocc=False, cxx_name="g++", k2_bin=None):
         super(KphpRunOnce, self).__init__(
@@ -27,6 +34,7 @@ def __init__(self, php_script_path, artifacts_dir, working_dir, php_bin,
         self._vkext_dir = vkext_dir
         self._php_bin = php_bin
         self.k2_bin = k2_bin
+        self.builtin_calls = collections.defaultdict(int)
 
     def _get_extensions(self):
         if sys.platform == "darwin":
@@ -141,7 +149,7 @@ def run_with_kphp_and_k2(self, runs_cnt=1, args=[]):
 
         env = os.environ.copy()
         if "RUST_LOG" not in env:
-            env["RUST_LOG"] = "Warn"
+            env["RUST_LOG"] = "Warn,component-log=Debug"
 
         k2_runtime_proc = subprocess.Popen(cmd,
                                            cwd=self._kphp_runtime_tmp_dir,
@@ -152,7 +160,7 @@ def run_with_kphp_and_k2(self, runs_cnt=1, args=[]):
         self._kphp_server_stdout, _kphp_server_stderr = self._wait_proc(k2_runtime_proc)
 
         ignore_stderr = error_can_be_ignored(
-            ignore_patterns=[],
+            ignore_patterns=[".*DEBUG.*", ".*INFO.*"],
             binary_error_text=_kphp_server_stderr)
 
         if not ignore_stderr:
@@ -160,6 +168,10 @@ def run_with_kphp_and_k2(self, runs_cnt=1, args=[]):
                 "k2_runtime_stderr",
                 k2_runtime_proc.returncode,
                 content=_kphp_server_stderr)
+            
+        for match in self.K2_BUILTIN_CALLED_MSG_RE.finditer(_kphp_server_stderr):
+            self.builtin_calls[match[1]] += 1
+
         return k2_runtime_proc.returncode == 0
 
     def compare_php_and_kphp_stdout(self):
diff --git a/tests/python/lib/testcase.py b/tests/python/lib/testcase.py
index bf7940e49f..fda3e6939f 100644
--- a/tests/python/lib/testcase.py
+++ b/tests/python/lib/testcase.py
@@ -298,7 +298,8 @@ def should_use_k2(cls):
     @classmethod
     def kphp_env_for_k2_server_component(cls):
         env = {"KPHP_MODE": "k2-server", "KPHP_ENABLE_FULL_PERFORMANCE_ANALYZE": "0",
-               "KPHP_PROFILER": "0", "KPHP_USER_BINARY_PATH": "component.so", "KPHP_FORCE_LINK_RUNTIME": "1"}
+               "KPHP_PROFILER": "0", "KPHP_USER_BINARY_PATH": "component.so", "KPHP_FORCE_LINK_RUNTIME": "1",
+               "KPHP_TRACKED_BUILTINS_LIST": KphpRunOnce.K2_KPHP_TRACKED_BUILTINS_LIST}
         return env
 
     def assertKphpNoTerminatedRequests(self):