Errors and Resource Limits

Script diagnostics fall into two categories: Static (Compile-Time) Errors detected when editing and saving the node, and Runtime Errors raised during workflow execution.

Static Errors (Compile-Time)

Static errors block saving in the Properties modal and report the exact line:column. If a saved workflow fails static checking when opened (e.g., an unsupported script version), the node fails at runtime with SCRIPT_COMPILE_ERROR.

Syntax Diagnostics

Diagnostic Code	Meaning & Resolution
`SCRIPT_SYNTAX_SOURCE_TOO_LARGE`	Script source exceeds 64 KiB. Factor repeated logic into functions or loops.
`SCRIPT_SYNTAX_TAB_INDENT`	Tab character used in indentation; indent with 4 spaces per level.
`SCRIPT_SYNTAX_INDENT_UNIT`	Indentation is not a multiple of 4 spaces.
`SCRIPT_SYNTAX_INDENT_TOO_DEEP`	Indentation increased by more than one 4-space level at once.
`SCRIPT_SYNTAX_UNEXPECTED_INDENT`	Indented line where no block was opened.
`SCRIPT_SYNTAX_EXPECTED_INDENT`	Missing indented block after a colon (`:`).
`SCRIPT_SYNTAX_BLOCK_SAME_LINE`	Block body written on the same line after `:`; place the body on the next line indented by 4 spaces.
`SCRIPT_SYNTAX_SEMICOLON`	Semicolon (`;`) used to join statements; write one statement per line.
`SCRIPT_SYNTAX_LINE_CONTINUATION`	Backslash (`\`) line continuation used; wrap multi-line expressions in parentheses instead.
`SCRIPT_SYNTAX_UNCLOSED_BRACKET`	Unclosed parenthesis `(` or bracket `[`.
`SCRIPT_SYNTAX_UNMATCHED_BRACKET`	Closing parenthesis or bracket with no matching opener.
`SCRIPT_SYNTAX_BRACE`	Curly braces `{ }` used outside an f-string (dicts and sets are not supported).
`SCRIPT_SYNTAX_UNKNOWN_CHAR`	Unrecognized character outside string literals and comments.
`SCRIPT_SYNTAX_RESERVED_NAME`	Identifier starts with a reserved double underscore (`__`).
`SCRIPT_SYNTAX_FLOAT`	Floating-point literal used; only integers are supported.
`SCRIPT_SYNTAX_INVALID_NUMBER`	Malformed integer literal.
`SCRIPT_SYNTAX_SINGLE_QUOTE`	Single-quoted string used; use double quotes (`"..."`).
`SCRIPT_SYNTAX_UNTERMINATED_STRING`	String or byte literal is missing its closing quote.
`SCRIPT_SYNTAX_BAD_ESCAPE`	Unsupported escape sequence (only `\\`, `\"`, `\n`, `\r`, `\t`, and `\uNNNN` are allowed).
`SCRIPT_SYNTAX_HEX_INVALID_CHAR`	`h"..."` literal contains non-hex characters (or a `0x` prefix).
`SCRIPT_SYNTAX_HEX_ODD_DIGITS`	`h"..."` literal has an odd number of hex digits.
`SCRIPT_SYNTAX_BIN_INVALID_CHAR`	`b"..."` literal contains characters other than `0`, `1`, and space (use `h"..."` for hex or `s"..."` for UTF-8 text).
`SCRIPT_SYNTAX_BIN_BIT_COUNT`	`b"..."` literal bit count is not a multiple of 8.
`SCRIPT_SYNTAX_LITERAL_PREFIX_SPACE`	Whitespace between literal prefix (`h`/`b`/`s`/`f`) and opening quote.
`SCRIPT_SYNTAX_LITERAL_MIXED_KIND`	Adjacent concatenation mixed different literal kinds; join them with `+` instead.
`SCRIPT_SYNTAX_LITERAL_CONCAT_OUTSIDE_PAREN`	Adjacent literal concatenation outside parentheses; wrap in `(...)` or use `+`.
`SCRIPT_SYNTAX_FSTRING_BRACE`	Unescaped single `}` in f-string; write `}}` for a literal brace.
`SCRIPT_SYNTAX_FSTRING_FIELD`	Malformed f-string interpolation field (quotes, braces, and backslashes cannot appear inside the expression).
`SCRIPT_SYNTAX_FSTRING_EMPTY`	Empty interpolation field `{}` in f-string.
`SCRIPT_SYNTAX_UNEXPECTED_TOKEN`	Unexpected token in statement or expression.
`SCRIPT_SYNTAX_UNSUPPORTED`	Unsupported Python construct (`import`, `class`, `while`, `lambda`, `try`, `print`, etc.).
`SCRIPT_SYNTAX_UNSUPPORTED_OPERATOR`	Unsupported operator (`**` or `/`); use `pow(base, exp, mod)` or `//`.
`SCRIPT_SYNTAX_ATTRIBUTE`	Attribute access or method call (`.`); call built-in functions directly.
`SCRIPT_SYNTAX_COMPREHENSION`	List comprehension used; use a `for` loop with `+= [item]`.
`SCRIPT_SYNTAX_CHAINED_COMPARISON`	Chained comparison (`a < b < c`); write `(a < b) and (b < c)`.
`SCRIPT_SYNTAX_CALL_TARGET`	Attempted to call a non-identifier expression.
`SCRIPT_SYNTAX_POSITIONAL_AFTER_KEYWORD`	Positional argument follows a keyword argument.
`SCRIPT_SYNTAX_EXPR_STATEMENT`	Non-call expression used as a standalone statement.
`SCRIPT_SYNTAX_DANGLING_ELSE`	`elif` or `else` without a matching `if`.
`SCRIPT_SYNTAX_NESTED_DEF`	Function defined inside another block; define all functions at the top level.
`SCRIPT_SYNTAX_ANNOTATION_NO_VALUE`	Type annotation without an initializer (write `x: int = 0`).
`SCRIPT_SYNTAX_UNPACK_RHS`	Right-hand side of tuple unpacking is neither a tuple nor a function call.
`SCRIPT_SYNTAX_TUPLE_CONTEXT`	Tuple used outside a `return` statement or unpacking assignment.
`SCRIPT_SYNTAX_TUPLE_ARITY`	`tuple[...]` return type annotation has fewer than 2 element types.
`SCRIPT_SYNTAX_PARAM_TYPE`	Function parameter is missing its type annotation.
`SCRIPT_SYNTAX_PARAM_DEFAULT`	Default parameter value specified on a user-defined function.
`SCRIPT_SYNTAX_UNKNOWN_TYPE`	Unknown type name in annotation (use `int`, `bool`, `bytes`, `string`, or `list[...]`).
`SCRIPT_SYNTAX_NESTED_LIST`	Nested list type annotation `list[list[...]]` is not supported.

Name, Type, and Flow Diagnostics

Diagnostic Code	Meaning & Resolution
`SCRIPT_TYPE_MISMATCH`	Type mismatch in assignment, condition, operator operand, or function argument.
`SCRIPT_OUTPUT_TYPE_MISMATCH`	Value assigned to an output port variable does not match the port's declared data type.
`SCRIPT_OUTPUT_UNASSIGNED`	An output port variable is not definitely assigned along all execution paths (see Definite Assignment Analysis).
`SCRIPT_UNASSIGNED`	Variable read before it is guaranteed to be assigned on all paths.
`SCRIPT_INPUT_READONLY`	Attempted to reassign or mutate a read-only input port variable.
`SCRIPT_NAME_UNDEFINED`	Referenced an undefined variable or function name.
`SCRIPT_NAME_RESERVED`	Used a built-in function name as a variable or user function name.
`SCRIPT_NAME_CONFLICT`	Identifier collides with an existing function, variable, constant, parameter, or port.
`SCRIPT_CONST_NOT_TOP`	All-uppercase constant defined inside a block rather than at the top level.
`SCRIPT_CONST_REASSIGN`	Attempted to reassign or mutate an immutable constant.
`SCRIPT_CONST_INVALID`	Constant initializer references non-constant variables or input ports.
`SCRIPT_FUNC_SCOPE`	Function body references a top-level variable, input port, or output port directly.
`SCRIPT_FUNC_ORDER`	Called a user function before its definition (or attempted recursion).
`SCRIPT_CALL_ARGS`	Invalid argument count or keyword argument name in function call.
`SCRIPT_RETURN_OUTSIDE`	`return` statement used outside a function.
`SCRIPT_RETURN_TYPE`	Returned value does not match the function's declared return type.
`SCRIPT_RETURN_MISSING`	Value-returning function has an execution path that does not end with `return`.
`SCRIPT_TUPLE_MISMATCH`	Tuple unpacking target count does not match, or repeats the same target variable.
`SCRIPT_TUPLE_MISMATCH` / `SCRIPT_TUPLE_CONTEXT`	Tuple value used outside unpacking or return.
`SCRIPT_RANGE_CONTEXT`	`range(...)` used outside the header of a `for` loop.
`SCRIPT_LOOP_CONTROL_OUTSIDE`	`break` or `continue` used outside a `for` loop.
`SCRIPT_EMPTY_LIST`	Empty list `[]` used without an explicit type annotation (write `xs: list[bytes] = []`).
`SCRIPT_NESTED_LIST`	Attempted to construct a nested list.
`SCRIPT_INT_LITERAL_TOO_LARGE`	Integer literal exceeds 1,048,576 bits.
`SCRIPT_FORMAT_INVALID`	Invalid f-string format specifier for the expression's type or width limit (> 4,096).

Port Schema Diagnostics

Diagnostic Code	Meaning & Resolution
`SCRIPT_PORT_INVALID_ID`	Port name violates identifier syntax (`[A-Za-z_][A-Za-z0-9_]*`) or starts with `__`.
`SCRIPT_PORT_RESERVED_ID`	Port name collides with a reserved keyword or built-in function name.
`SCRIPT_PORT_DUPLICATE_ID`	Two ports on the Script node share the same name/ID.
`SCRIPT_PORT_INVALID_TYPE`	Port data type is not one of `bytes`, `int`, `bool`, or `string`.

Runtime Errors

Error Code	Meaning	Example
`SCRIPT_COMPILE_ERROR`	Saved script failed static verification or uses an unsupported script version.	—
`SCRIPT_DIVISION_BY_ZERO`	Divisor of `//` or `%` is `0`.	`1 // 0`
`SCRIPT_INDEX_OUT_OF_RANGE`	List index or slice range is out of bounds.	`[1, 2][5]`
`SCRIPT_INVALID_ARGUMENT`	Negative bit-shift count, zero `range` step, or invalid `pow` arguments.	`1 << -1`
`SCRIPT_INVALID_ERROR_CODE`	Custom code passed to `fail(code, message)` starts with reserved `SCRIPT_` or `BYTES_`.	—
`SCRIPT_SIZE_LIMIT`	Integer bit length, list length, or loop iteration count exceeded 1,048,576.	`1 << 2000000`
`SCRIPT_STEP_LIMIT`	Execution exceeded the 10,000,000 evaluation step limit.	—
`SCRIPT_TIMEOUT`	Execution exceeded the wall-clock timeout (3 seconds in Web, 10 seconds in API Container).	—
`SCRIPT_INTERNAL_ERROR`	Unexpected internal interpreter error.	—

Byte Operation Errors

Error Code	Meaning	Example
`BYTES_OUT_OF_RANGE`	Byte index or slice range is outside the buffer bounds.	`h"01 02"[2]`
`BYTES_LENGTH_MISMATCH`	Operands to a bytewise operator or slice assignment have different lengths.	`h"01" ^ h"01 02"`
`BYTES_INT_OVERFLOW`	Integer cannot fit in the requested byte length and signedness.	`to_bytes(256, 1)`
`BYTES_INVALID_HEX`	Invalid hexadecimal string passed to `from_hex`.	`from_hex("zz")`
`BYTES_INVALID_UTF8`	Invalid UTF-8 byte sequence passed to `to_utf8`.	`to_utf8(h"c3 28")`
`BYTES_INVALID_ARGUMENT`	Negative length/count, out-of-range byte value, or invalid endianness string.	`to_int(h"01", "middle")`
`BYTES_SIZE_LIMIT`	Resulting byte array exceeds the 16 MiB buffer limit.	`zeros(20000000)`

Resource Limits

Resource	Limit	Error Code When Exceeded
Evaluation steps	10,000,000	SCRIPT_STEP_LIMIT
Single `bytes` buffer size	16 MiB	BYTES_SIZE_LIMIT
Single `list` length / `for` loop iterations	1,048,576	SCRIPT_SIZE_LIMIT
Single `int` bit length	1,048,576 bits	SCRIPT_SIZE_LIMIT (or SCRIPT_INT_LITERAL_TOO_LARGE)
Script source size	64 KiB	SCRIPT_SYNTAX_SOURCE_TOO_LARGE
f-string field width	4,096	SCRIPT_FORMAT_INVALID
Wall-clock execution time	3 s (Web) / 10 s (API Container)	SCRIPT_TIMEOUT

o = 0
for i in range(1000000):
    for j in range(100):
        o += 1

o = 0
for i in range(2000000):
    o += 1