diff --git a/src/script_opt/FuncInfo.cc b/src/script_opt/FuncInfo.cc
index 6b89e4c3a6..efce28a613 100644
--- a/src/script_opt/FuncInfo.cc
+++ b/src/script_opt/FuncInfo.cc
@@ -27,13 +27,22 @@ namespace zeek::detail {
 // ATTR_NO_SCRIPT_SIDE_EFFECTS.
 #define ATTR_NO_ZEEK_SIDE_EFFECTS 0x2
 
-// Calls made with the same arguments yield the same results. Implies
-// ATTR_NO_ZEEK_SIDE_EFFECTS.
+// Calls made with the same arguments yield the same results, if made
+// after full Zeek initialization. Implies ATTR_NO_ZEEK_SIDE_EFFECTS.
 #define ATTR_IDEMPOTENT 0x4
 
+// Calls with constant arguments can always be folded, even prior to
+// full Zeek initialization. Such functions must not have the potential
+// to generate errors. Implies ATTR_IDEMPOTENT.
+#define ATTR_FOLDABLE 0x8
+
 // The event engine knows about this script function and may call it
 // during its processing.
-#define ATTR_SPECIAL_SCRIPT_FUNC 0x8
+#define ATTR_SPECIAL_SCRIPT_FUNC 0x10
+
+// ZAM knows about this script function and will replace it with specialized
+// instructions.
+#define ATTR_ZAM_REPLACEABLE_SCRIPT_FUNC 0x20
 
 static std::unordered_map<std::string, unsigned int> func_attrs = {
     // Script functions.
@@ -52,15 +61,17 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"discarder_check_udp", ATTR_SPECIAL_SCRIPT_FUNC},
     {"from_json_default_key_mapper", ATTR_SPECIAL_SCRIPT_FUNC},
 
+    {"id_string", ATTR_ZAM_REPLACEABLE_SCRIPT_FUNC},
+
     // BiFs.
     {"Analyzer::__disable_all_analyzers", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"Analyzer::__disable_analyzer", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"Analyzer::__enable_analyzer", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"Analyzer::__has_tag", ATTR_IDEMPOTENT},
-    {"Analyzer::__name", ATTR_IDEMPOTENT},
+    {"Analyzer::__has_tag", ATTR_FOLDABLE},
+    {"Analyzer::__name", ATTR_FOLDABLE},
     {"Analyzer::__register_for_port", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"Analyzer::__schedule_analyzer", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"Analyzer::__tag", ATTR_IDEMPOTENT},
+    {"Analyzer::__tag", ATTR_FOLDABLE},
     {"FileExtract::__set_limit", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"Files::__add_analyzer", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"Files::__analyzer_enabled", ATTR_NO_ZEEK_SIDE_EFFECTS},
@@ -92,7 +103,7 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"Log::__set_buf", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"Log::__set_max_delay_interval", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"Log::__set_max_delay_queue_size", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"Option::any_set_to_any_vec", ATTR_IDEMPOTENT},
+    {"Option::any_set_to_any_vec", ATTR_FOLDABLE},
     {"Option::set_change_handler", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"PacketAnalyzer::GTPV1::remove_gtpv1_connection", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"PacketAnalyzer::TEREDO::remove_teredo_connection", ATTR_NO_SCRIPT_SIDE_EFFECTS},
@@ -166,17 +177,18 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"Telemetry::__int_histogram_metric_get_or_add", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"Telemetry::__int_histogram_observe", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"Telemetry::__int_histogram_sum", ATTR_NO_SCRIPT_SIDE_EFFECTS},
+    {"WebSocket::__configure_analyzer", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"__init_primary_bifs", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"__init_secondary_bifs", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"active_file", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"addr_to_counts", ATTR_IDEMPOTENT},
-    {"addr_to_ptr_name", ATTR_IDEMPOTENT},
-    {"addr_to_subnet", ATTR_IDEMPOTENT},
-    {"all_set", ATTR_IDEMPOTENT},
-    {"anonymize_addr", ATTR_IDEMPOTENT},
-    {"any_set", ATTR_IDEMPOTENT},
+    {"addr_to_counts", ATTR_FOLDABLE},
+    {"addr_to_ptr_name", ATTR_FOLDABLE},
+    {"addr_to_subnet", ATTR_FOLDABLE},
+    {"all_set", ATTR_FOLDABLE},
+    {"anonymize_addr", ATTR_FOLDABLE},
+    {"any_set", ATTR_FOLDABLE},
     {"backtrace", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"bare_mode", ATTR_IDEMPOTENT},
+    {"bare_mode", ATTR_FOLDABLE},
     {"bloomfilter_add", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"bloomfilter_basic_init", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"bloomfilter_basic_init2", ATTR_NO_SCRIPT_SIDE_EFFECTS},
@@ -187,76 +199,77 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"bloomfilter_intersect", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"bloomfilter_lookup", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"bloomfilter_merge", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"bytestring_to_count", ATTR_IDEMPOTENT},
-    {"bytestring_to_double", ATTR_IDEMPOTENT},
-    {"bytestring_to_float", ATTR_IDEMPOTENT},
-    {"bytestring_to_hexstr", ATTR_IDEMPOTENT},
+    {"bytestring_to_count", ATTR_IDEMPOTENT},  // can error
+    {"bytestring_to_double", ATTR_IDEMPOTENT}, // can error
+    {"bytestring_to_float", ATTR_IDEMPOTENT},  // can error
+    {"bytestring_to_hexstr", ATTR_FOLDABLE},
     {"calc_next_rotate", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"cat", ATTR_IDEMPOTENT},
-    {"cat_sep", ATTR_IDEMPOTENT},
-    {"ceil", ATTR_IDEMPOTENT},
-    {"check_subnet", ATTR_IDEMPOTENT},
-    {"clean", ATTR_IDEMPOTENT},
+    {"cat", ATTR_FOLDABLE},
+    {"cat_sep", ATTR_IDEMPOTENT}, // can error
+    {"ceil", ATTR_FOLDABLE},
+    {"check_subnet", ATTR_FOLDABLE},
+    {"clean", ATTR_FOLDABLE},
     {"close", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"community_id_v1", ATTR_IDEMPOTENT},
-    {"compress_path", ATTR_IDEMPOTENT},
+    {"community_id_v1", ATTR_FOLDABLE},
+    {"compress_path", ATTR_FOLDABLE},
     {"connection_exists", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"continue_processing", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"convert_for_pattern", ATTR_IDEMPOTENT},
-    {"count_substr", ATTR_IDEMPOTENT},
-    {"count_to_double", ATTR_IDEMPOTENT},
-    {"count_to_port", ATTR_IDEMPOTENT},
-    {"count_to_v4_addr", ATTR_IDEMPOTENT},
-    {"counts_to_addr", ATTR_IDEMPOTENT},
+    {"convert_for_pattern", ATTR_FOLDABLE},
+    {"count_substr", ATTR_FOLDABLE},
+    {"count_to_double", ATTR_FOLDABLE},
+    {"count_to_port", ATTR_FOLDABLE},
+    {"count_to_v4_addr", ATTR_IDEMPOTENT}, // can error
+    {"counts_to_addr", ATTR_IDEMPOTENT},   // can error
     {"current_analyzer", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"current_event_time", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"current_time", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"decode_base64", ATTR_IDEMPOTENT},
+    {"decode_base64", ATTR_IDEMPOTENT}, // can error
     {"decode_base64_conn", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"decode_netbios_name", ATTR_IDEMPOTENT},
-    {"decode_netbios_name_type", ATTR_IDEMPOTENT},
+    {"decode_netbios_name", ATTR_FOLDABLE},
+    {"decode_netbios_name_type", ATTR_FOLDABLE},
     {"disable_event_group", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"disable_module_events", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"do_profiling", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"double_to_count", ATTR_IDEMPOTENT},
-    {"double_to_int", ATTR_IDEMPOTENT},
-    {"double_to_interval", ATTR_IDEMPOTENT},
-    {"double_to_time", ATTR_IDEMPOTENT},
+    {"double_to_count", ATTR_IDEMPOTENT}, // can error
+    {"double_to_int", ATTR_FOLDABLE},
+    {"double_to_interval", ATTR_FOLDABLE},
+    {"double_to_time", ATTR_FOLDABLE},
     {"dump_current_packet", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"dump_packet", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"dump_rule_stats", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"edit", ATTR_IDEMPOTENT},
+    {"edit", ATTR_FOLDABLE},
     {"enable_event_group", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"enable_module_events", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"enable_raw_output", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"encode_base64", ATTR_IDEMPOTENT},
-    {"ends_with", ATTR_IDEMPOTENT},
+    {"encode_base64", ATTR_FOLDABLE},
+    {"ends_with", ATTR_FOLDABLE},
     {"entropy_test_add", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"entropy_test_finish", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"entropy_test_init", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"enum_names", ATTR_IDEMPOTENT},
-    {"enum_to_int", ATTR_IDEMPOTENT},
-    {"escape_string", ATTR_IDEMPOTENT},
+    {"enum_to_int", ATTR_IDEMPOTENT}, // can error
+    {"escape_string", ATTR_FOLDABLE},
     {"exit", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"exp", ATTR_IDEMPOTENT},
-    {"file_magic", ATTR_IDEMPOTENT},
+    {"exp", ATTR_FOLDABLE},
+    {"file_magic", ATTR_FOLDABLE},
     {"file_mode", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"file_size", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"filter_subnet_table", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"find_all", ATTR_IDEMPOTENT},
-    {"find_all_ordered", ATTR_IDEMPOTENT},
-    {"find_entropy", ATTR_IDEMPOTENT},
-    {"find_last", ATTR_IDEMPOTENT},
-    {"find_str", ATTR_IDEMPOTENT},
-    {"floor", ATTR_IDEMPOTENT},
+    {"find_all", ATTR_FOLDABLE},
+    {"find_all_ordered", ATTR_FOLDABLE},
+    {"find_entropy", ATTR_FOLDABLE},
+    {"find_in_zeekpath", ATTR_IDEMPOTENT}, // can error
+    {"find_last", ATTR_FOLDABLE},
+    {"find_str", ATTR_FOLDABLE},
+    {"floor", ATTR_FOLDABLE},
     {"flush_all", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"fmt", ATTR_IDEMPOTENT},
-    {"fmt_ftp_port", ATTR_IDEMPOTENT},
-    {"fnv1a32", ATTR_IDEMPOTENT},
+    {"fmt", ATTR_FOLDABLE},
+    {"fmt_ftp_port", ATTR_IDEMPOTENT}, // can error
+    {"fnv1a32", ATTR_FOLDABLE},
     {"generate_all_events", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"get_broker_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_conn_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"get_conn_transport_proto", ATTR_IDEMPOTENT},
+    {"get_conn_transport_proto", ATTR_FOLDABLE},
     {"get_contents_file", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_current_conn_bytes_threshold", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_current_conn_duration_threshold", ATTR_NO_ZEEK_SIDE_EFFECTS},
@@ -267,7 +280,7 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"get_event_handler_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_event_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_file_analysis_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"get_file_name", ATTR_IDEMPOTENT},
+    {"get_file_name", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_gap_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_identifier_comments", ATTR_IDEMPOTENT},
     {"get_identifier_declaring_script", ATTR_IDEMPOTENT},
@@ -275,8 +288,8 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"get_matcher_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_net_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_orig_seq", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"get_package_readme", ATTR_IDEMPOTENT},
-    {"get_port_transport_proto", ATTR_IDEMPOTENT},
+    {"get_package_readme", ATTR_FOLDABLE},
+    {"get_port_transport_proto", ATTR_FOLDABLE},
     {"get_proc_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_reassembler_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"get_record_field_comments", ATTR_IDEMPOTENT},
@@ -292,54 +305,54 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"global_container_footprints", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"global_ids", ATTR_IDEMPOTENT},
     {"global_options", ATTR_IDEMPOTENT},
-    {"gsub", ATTR_IDEMPOTENT},
+    {"gsub", ATTR_FOLDABLE},
     {"has_event_group", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"has_module_events", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"have_spicy", ATTR_IDEMPOTENT},
     {"have_spicy_analyzers", ATTR_IDEMPOTENT},
-    {"haversine_distance", ATTR_IDEMPOTENT},
-    {"hexdump", ATTR_IDEMPOTENT},
-    {"hexstr_to_bytestring", ATTR_IDEMPOTENT},
+    {"haversine_distance", ATTR_FOLDABLE},
+    {"hexdump", ATTR_FOLDABLE},
+    {"hexstr_to_bytestring", ATTR_IDEMPOTENT}, // can error
     {"hll_cardinality_add", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"hll_cardinality_copy", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"hll_cardinality_estimate", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"hll_cardinality_init", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"hll_cardinality_merge_into", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"hrw_weight", ATTR_IDEMPOTENT},
-    {"identify_data", ATTR_IDEMPOTENT},
+    {"hrw_weight", ATTR_FOLDABLE},
+    {"identify_data", ATTR_FOLDABLE},
     {"install_dst_addr_filter", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"install_dst_net_filter", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"install_src_addr_filter", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"install_src_net_filter", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"int_to_count", ATTR_IDEMPOTENT},
-    {"int_to_double", ATTR_IDEMPOTENT},
-    {"interval_to_double", ATTR_IDEMPOTENT},
-    {"is_alnum", ATTR_IDEMPOTENT},
-    {"is_alpha", ATTR_IDEMPOTENT},
-    {"is_ascii", ATTR_IDEMPOTENT},
+    {"int_to_count", ATTR_IDEMPOTENT}, // can error
+    {"int_to_double", ATTR_FOLDABLE},
+    {"interval_to_double", ATTR_FOLDABLE},
+    {"is_alnum", ATTR_FOLDABLE},
+    {"is_alpha", ATTR_FOLDABLE},
+    {"is_ascii", ATTR_FOLDABLE},
     {"is_file_analyzer", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"is_icmp_port", ATTR_IDEMPOTENT},
+    {"is_icmp_port", ATTR_FOLDABLE},
     {"is_local_interface", ATTR_IDEMPOTENT},
-    {"is_num", ATTR_IDEMPOTENT},
+    {"is_num", ATTR_FOLDABLE},
     {"is_packet_analyzer", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"is_processing_suspended", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"is_protocol_analyzer", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"is_remote_event", ATTR_IDEMPOTENT},
-    {"is_tcp_port", ATTR_IDEMPOTENT},
-    {"is_udp_port", ATTR_IDEMPOTENT},
-    {"is_v4_addr", ATTR_IDEMPOTENT},
-    {"is_v4_subnet", ATTR_IDEMPOTENT},
-    {"is_v6_addr", ATTR_IDEMPOTENT},
-    {"is_v6_subnet", ATTR_IDEMPOTENT},
-    {"is_valid_ip", ATTR_IDEMPOTENT},
-    {"join_string_set", ATTR_IDEMPOTENT},
-    {"join_string_vec", ATTR_IDEMPOTENT},
-    {"levenshtein_distance", ATTR_IDEMPOTENT},
-    {"ljust", ATTR_IDEMPOTENT},
-    {"ln", ATTR_IDEMPOTENT},
+    {"is_tcp_port", ATTR_FOLDABLE},
+    {"is_udp_port", ATTR_FOLDABLE},
+    {"is_v4_addr", ATTR_FOLDABLE},
+    {"is_v4_subnet", ATTR_FOLDABLE},
+    {"is_v6_addr", ATTR_FOLDABLE},
+    {"is_v6_subnet", ATTR_FOLDABLE},
+    {"is_valid_ip", ATTR_FOLDABLE},
+    {"join_string_set", ATTR_FOLDABLE},
+    {"join_string_vec", ATTR_FOLDABLE},
+    {"levenshtein_distance", ATTR_FOLDABLE},
+    {"ljust", ATTR_FOLDABLE},
+    {"ln", ATTR_FOLDABLE},
     {"load_CPP", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"log10", ATTR_IDEMPOTENT},
-    {"log2", ATTR_IDEMPOTENT},
+    {"log10", ATTR_FOLDABLE},
+    {"log2", ATTR_FOLDABLE},
     {"lookup_ID", ATTR_IDEMPOTENT},
     {"lookup_addr", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"lookup_autonomous_system", ATTR_NO_SCRIPT_SIDE_EFFECTS},
@@ -347,15 +360,15 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"lookup_hostname", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"lookup_hostname_txt", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"lookup_location", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"lstrip", ATTR_IDEMPOTENT},
-    {"mask_addr", ATTR_IDEMPOTENT},
+    {"lstrip", ATTR_FOLDABLE},
+    {"mask_addr", ATTR_FOLDABLE},
     {"match_signatures", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"matching_subnets", ATTR_IDEMPOTENT},
-    {"md5_hash", ATTR_IDEMPOTENT},
+    {"matching_subnets", ATTR_FOLDABLE},
+    {"md5_hash", ATTR_FOLDABLE},
     {"md5_hash_finish", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"md5_hash_init", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"md5_hash_update", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"md5_hmac", ATTR_IDEMPOTENT},
+    {"md5_hmac", ATTR_FOLDABLE},
     {"mkdir", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"mmdb_open_asn_db", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"mmdb_open_location_db", ATTR_NO_SCRIPT_SIDE_EFFECTS},
@@ -366,38 +379,38 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"paraglob_equals", ATTR_IDEMPOTENT},
     {"paraglob_init", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"paraglob_match", ATTR_IDEMPOTENT},
-    {"parse_distinguished_name", ATTR_IDEMPOTENT},
-    {"parse_eftp_port", ATTR_IDEMPOTENT},
-    {"parse_ftp_epsv", ATTR_IDEMPOTENT},
-    {"parse_ftp_pasv", ATTR_IDEMPOTENT},
-    {"parse_ftp_port", ATTR_IDEMPOTENT},
+    {"parse_distinguished_name", ATTR_FOLDABLE},
+    {"parse_eftp_port", ATTR_FOLDABLE},
+    {"parse_ftp_epsv", ATTR_FOLDABLE},
+    {"parse_ftp_pasv", ATTR_FOLDABLE},
+    {"parse_ftp_port", ATTR_FOLDABLE},
     {"piped_exec", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"port_to_count", ATTR_IDEMPOTENT},
-    {"pow", ATTR_IDEMPOTENT},
+    {"port_to_count", ATTR_FOLDABLE},
+    {"pow", ATTR_FOLDABLE},
     {"preserve_prefix", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"preserve_subnet", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"print_raw", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"ptr_name_to_addr", ATTR_IDEMPOTENT},
+    {"ptr_name_to_addr", ATTR_IDEMPOTENT}, // can error
     {"rand", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"raw_bytes_to_v4_addr", ATTR_IDEMPOTENT},
-    {"raw_bytes_to_v6_addr", ATTR_IDEMPOTENT},
+    {"raw_bytes_to_v4_addr", ATTR_IDEMPOTENT}, // can error
+    {"raw_bytes_to_v6_addr", ATTR_IDEMPOTENT}, // can error
     {"reading_live_traffic", ATTR_IDEMPOTENT},
     {"reading_traces", ATTR_IDEMPOTENT},
-    {"record_fields", ATTR_IDEMPOTENT},
-    {"record_type_to_vector", ATTR_IDEMPOTENT},
-    {"remask_addr", ATTR_IDEMPOTENT},
-    {"remove_prefix", ATTR_IDEMPOTENT},
-    {"remove_suffix", ATTR_IDEMPOTENT},
+    {"record_fields", ATTR_FOLDABLE},
+    {"record_type_to_vector", ATTR_FOLDABLE},
+    {"remask_addr", ATTR_FOLDABLE},
+    {"remove_prefix", ATTR_FOLDABLE},
+    {"remove_suffix", ATTR_FOLDABLE},
     {"rename", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"reverse", ATTR_IDEMPOTENT},
-    {"rfind_str", ATTR_IDEMPOTENT},
-    {"rjust", ATTR_IDEMPOTENT},
+    {"reverse", ATTR_FOLDABLE},
+    {"rfind_str", ATTR_FOLDABLE},
+    {"rjust", ATTR_FOLDABLE},
     {"rmdir", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"rotate_file", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"rotate_file_by_name", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"routing0_data_to_addrs", ATTR_IDEMPOTENT},
-    {"rstrip", ATTR_IDEMPOTENT},
-    {"safe_shell_quote", ATTR_IDEMPOTENT},
+    {"routing0_data_to_addrs", ATTR_IDEMPOTENT}, // can error
+    {"rstrip", ATTR_FOLDABLE},
+    {"safe_shell_quote", ATTR_FOLDABLE},
     {"same_object", ATTR_IDEMPOTENT},
     {"sct_verify", ATTR_IDEMPOTENT},
     {"set_buf", ATTR_NO_SCRIPT_SIDE_EFFECTS},
@@ -414,73 +427,73 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"set_secret", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"set_ssl_established", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"setenv", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"sha1_hash", ATTR_IDEMPOTENT},
+    {"sha1_hash", ATTR_FOLDABLE},
     {"sha1_hash_finish", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"sha1_hash_init", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"sha1_hash_update", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"sha256_hash", ATTR_IDEMPOTENT},
+    {"sha256_hash", ATTR_FOLDABLE},
     {"sha256_hash_finish", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"sha256_hash_init", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"sha256_hash_update", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"skip_further_processing", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"skip_http_entity_data", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"skip_smtp_data", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"split_string", ATTR_IDEMPOTENT},
-    {"split_string1", ATTR_IDEMPOTENT},
-    {"split_string_all", ATTR_IDEMPOTENT},
-    {"split_string_n", ATTR_IDEMPOTENT},
-    {"sqrt", ATTR_IDEMPOTENT},
+    {"split_string", ATTR_FOLDABLE},
+    {"split_string1", ATTR_FOLDABLE},
+    {"split_string_all", ATTR_FOLDABLE},
+    {"split_string_n", ATTR_FOLDABLE},
+    {"sqrt", ATTR_IDEMPOTENT}, // can error
     {"srand", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"starts_with", ATTR_IDEMPOTENT},
-    {"str_smith_waterman", ATTR_IDEMPOTENT},
-    {"str_split_indices", ATTR_IDEMPOTENT},
-    {"strcmp", ATTR_IDEMPOTENT},
-    {"strftime", ATTR_IDEMPOTENT},
-    {"string_cat", ATTR_IDEMPOTENT},
-    {"string_fill", ATTR_IDEMPOTENT},
-    {"string_to_ascii_hex", ATTR_IDEMPOTENT},
-    {"string_to_pattern", ATTR_IDEMPOTENT},
-    {"strip", ATTR_IDEMPOTENT},
-    {"strptime", ATTR_IDEMPOTENT},
-    {"strstr", ATTR_IDEMPOTENT},
-    {"sub", ATTR_IDEMPOTENT},
-    {"sub_bytes", ATTR_IDEMPOTENT},
-    {"subnet_to_addr", ATTR_IDEMPOTENT},
-    {"subnet_width", ATTR_IDEMPOTENT},
-    {"subst_string", ATTR_IDEMPOTENT},
+    {"starts_with", ATTR_FOLDABLE},
+    {"str_smith_waterman", ATTR_FOLDABLE},
+    {"str_split_indices", ATTR_FOLDABLE},
+    {"strcmp", ATTR_FOLDABLE},
+    {"strftime", ATTR_FOLDABLE},
+    {"string_cat", ATTR_FOLDABLE},
+    {"string_fill", ATTR_FOLDABLE},
+    {"string_to_ascii_hex", ATTR_FOLDABLE},
+    {"string_to_pattern", ATTR_FOLDABLE},
+    {"strip", ATTR_FOLDABLE},
+    {"strptime", ATTR_FOLDABLE},
+    {"strstr", ATTR_FOLDABLE},
+    {"sub", ATTR_FOLDABLE},
+    {"sub_bytes", ATTR_FOLDABLE},
+    {"subnet_to_addr", ATTR_FOLDABLE},
+    {"subnet_width", ATTR_FOLDABLE},
+    {"subst_string", ATTR_FOLDABLE},
     {"suspend_processing", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"swap_case", ATTR_IDEMPOTENT},
+    {"swap_case", ATTR_FOLDABLE},
     {"syslog", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"system", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"system_env", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"table_keys", ATTR_IDEMPOTENT},
-    {"table_pattern_matcher_stats", ATTR_IDEMPOTENT},
-    {"table_values", ATTR_IDEMPOTENT},
+    {"table_keys", ATTR_NO_ZEEK_SIDE_EFFECTS},
+    {"table_pattern_matcher_stats", ATTR_NO_ZEEK_SIDE_EFFECTS},
+    {"table_values", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"terminate", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"time_to_double", ATTR_IDEMPOTENT},
-    {"to_addr", ATTR_IDEMPOTENT},
-    {"to_count", ATTR_IDEMPOTENT},
-    {"to_double", ATTR_IDEMPOTENT},
-    {"to_int", ATTR_IDEMPOTENT},
-    {"to_json", ATTR_IDEMPOTENT},
-    {"to_lower", ATTR_IDEMPOTENT},
-    {"to_port", ATTR_IDEMPOTENT},
-    {"to_string_literal", ATTR_IDEMPOTENT},
-    {"to_subnet", ATTR_IDEMPOTENT},
-    {"to_title", ATTR_IDEMPOTENT},
-    {"to_upper", ATTR_IDEMPOTENT},
+    {"time_to_double", ATTR_FOLDABLE},
+    {"to_addr", ATTR_IDEMPOTENT},   // can error
+    {"to_count", ATTR_IDEMPOTENT},  // can error
+    {"to_double", ATTR_IDEMPOTENT}, // can error
+    {"to_int", ATTR_FOLDABLE},
+    {"to_json", ATTR_FOLDABLE},
+    {"to_lower", ATTR_FOLDABLE},
+    {"to_port", ATTR_IDEMPOTENT}, // can error
+    {"to_string_literal", ATTR_FOLDABLE},
+    {"to_subnet", ATTR_IDEMPOTENT}, // can error
+    {"to_title", ATTR_FOLDABLE},
+    {"to_upper", ATTR_FOLDABLE},
     {"topk_add", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"topk_count", ATTR_IDEMPOTENT},
-    {"topk_epsilon", ATTR_IDEMPOTENT},
+    {"topk_count", ATTR_NO_ZEEK_SIDE_EFFECTS},
+    {"topk_epsilon", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"topk_get_top", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"topk_init", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"topk_merge", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"topk_merge_prune", ATTR_NO_SCRIPT_SIDE_EFFECTS},
-    {"topk_size", ATTR_IDEMPOTENT},
-    {"topk_sum", ATTR_IDEMPOTENT},
-    {"type_aliases", ATTR_IDEMPOTENT},
-    {"type_name", ATTR_IDEMPOTENT},
-    {"unescape_URI", ATTR_IDEMPOTENT},
+    {"topk_size", ATTR_NO_ZEEK_SIDE_EFFECTS},
+    {"topk_sum", ATTR_NO_ZEEK_SIDE_EFFECTS},
+    {"type_aliases", ATTR_FOLDABLE},
+    {"type_name", ATTR_FOLDABLE},
+    {"unescape_URI", ATTR_FOLDABLE},
     {"uninstall_dst_addr_filter", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"uninstall_dst_net_filter", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"uninstall_src_addr_filter", ATTR_NO_SCRIPT_SIDE_EFFECTS},
@@ -488,7 +501,7 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"unique_id", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"unique_id_from", ATTR_NO_SCRIPT_SIDE_EFFECTS},
     {"unlink", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"uuid_to_string", ATTR_IDEMPOTENT},
+    {"uuid_to_string", ATTR_FOLDABLE},
     {"val_footprint", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"write_file", ATTR_NO_ZEEK_SIDE_EFFECTS},
     {"x509_check_cert_hostname", ATTR_IDEMPOTENT},
@@ -503,10 +516,10 @@ static std::unordered_map<std::string, unsigned int> func_attrs = {
     {"x509_spki_hash", ATTR_IDEMPOTENT},
     {"x509_subject_name_hash", ATTR_IDEMPOTENT},
     {"x509_verify", ATTR_IDEMPOTENT},
-    {"zeek_args", ATTR_IDEMPOTENT},
+    {"zeek_args", ATTR_FOLDABLE},
     {"zeek_is_terminating", ATTR_NO_ZEEK_SIDE_EFFECTS},
-    {"zeek_version", ATTR_IDEMPOTENT},
-    {"zfill", ATTR_IDEMPOTENT},
+    {"zeek_version", ATTR_FOLDABLE},
+    {"zfill", ATTR_FOLDABLE},
 };
 
 // Ones not listed:
@@ -555,9 +568,19 @@ bool is_special_script_func(const std::string& func_name) {
     return f_attr != func_attrs.end() && (f_attr->second & ATTR_SPECIAL_SCRIPT_FUNC) != 0;
 }
 
+bool is_ZAM_replaceable_script_func(const std::string& func_name) {
+    auto f_attr = func_attrs.find(func_name);
+    return f_attr != func_attrs.end() && (f_attr->second & ATTR_ZAM_REPLACEABLE_SCRIPT_FUNC) != 0;
+}
+
 bool is_idempotent(const std::string& func_name) {
     auto f_attr = func_attrs.find(func_name);
-    return f_attr != func_attrs.end() && (f_attr->second & ATTR_IDEMPOTENT) != 0;
+    return f_attr != func_attrs.end() && (f_attr->second & (ATTR_IDEMPOTENT | ATTR_FOLDABLE)) != 0;
+}
+
+bool is_foldable(const std::string& func_name) {
+    auto f_attr = func_attrs.find(func_name);
+    return f_attr != func_attrs.end() && (f_attr->second & ATTR_FOLDABLE) != 0;
 }
 
 bool has_script_side_effects(const std::string& func_name) {
@@ -566,7 +589,8 @@ bool has_script_side_effects(const std::string& func_name) {
         // We don't know about it, so be conservative.
         return true;
 
-    return (f_attr->second & (ATTR_NO_SCRIPT_SIDE_EFFECTS | ATTR_NO_ZEEK_SIDE_EFFECTS | ATTR_IDEMPOTENT)) == 0;
+    return (f_attr->second &
+            (ATTR_NO_SCRIPT_SIDE_EFFECTS | ATTR_NO_ZEEK_SIDE_EFFECTS | ATTR_IDEMPOTENT | ATTR_FOLDABLE)) == 0;
 }
 
 } // namespace zeek::detail
diff --git a/src/script_opt/FuncInfo.h b/src/script_opt/FuncInfo.h
index 53095d227d..f36601c8b2 100644
--- a/src/script_opt/FuncInfo.h
+++ b/src/script_opt/FuncInfo.h
@@ -12,11 +12,18 @@ namespace zeek::detail {
 // knows about.
 extern bool is_special_script_func(const std::string& func_name);
 
+// Whether ZAM can replace the given script with specialized instructions.
+extern bool is_ZAM_replaceable_script_func(const std::string& func_name);
+
 // An idempotent function returns the same value when called with the
 // same arguments (and has no meaningful side effects in terms of script-level
 // or Zeek-internal state).
 extern bool is_idempotent(const std::string& func_name);
 
+// A foldable function can be folded at compile time if all of its arguments
+// are constants. Such functions cannot generate error messages.
+extern bool is_foldable(const std::string& func_name);
+
 // Whether the given function (currently, just BiFs) has Zeek-script-level
 // side effects.
 extern bool has_script_side_effects(const std::string& func_name);
diff --git a/src/script_opt/Inline.cc b/src/script_opt/Inline.cc
index f6ef4d1fb5..8cf2479bd5 100644
--- a/src/script_opt/Inline.cc
+++ b/src/script_opt/Inline.cc
@@ -34,6 +34,11 @@ void Inliner::Analyze() {
         if ( is_special_script_func(f.Func()->Name()) )
             continue;
 
+        // If ZAM can replace the script, don't inline it, so its usage
+        // remains visible during the AST reduction process.
+        if ( is_ZAM_replaceable_script_func(f.Func()->Name()) )
+            continue;
+
         std::unordered_set<const Func*> cs;
 
         // Aspirational ....