Claro/docs/RUNTIME_LIMITS.md

Current runtime guards

Claro runs trusted scripts with the user's permissions. These guards are not a sandbox, a wall-clock timeout, or proof that arbitrary scripts use bounded resources.

Always-on nesting/response guards

• Function/method calls: at most 256 active calls.
• Expressions and additional nested control blocks: at most 128 levels.
• Parsed JSON: at most 128 nested arrays/objects. A scalar inside 128 containers is allowed; a 129th container is rejected. Malformed syntax fails with a Claro diagnostic rather than looping without consuming input. JSON Unicode escapes and surrogate pairs are decoded; embedded zero characters are rejected because Claro text uses zero-terminated strings. This is not a general encoding validator.
• HTTP response bodies: the existing 1,048,576-byte cap remains.

Errors raised during expressions keep the executing source file and line, including imported functions and caught LASTERRORFILE/LASTERRORLINE metadata. REPEAT without UNTIL is rejected before accessing a missing terminator.

Optional guards — disabled by default

CLARO_STEP_LIMIT sets a non-negative interpreter-work budget. Zero/unset means unlimited. It counts source-line dispatches and block/range entries, including empty loop iterations; it is not an exact statement count or elapsed time. Once exhausted it reports a source-located error suggesting the loop be checked. The consumed budget is not reset by TRY/CATCH or by calling a function.

CLARO_READ_FILE_LIMIT sets the maximum bytes read by each READ FILE command. Zero/unset means unlimited. The exact boundary is accepted; larger input errors without storing a partial result. It does not cap source loading, package metadata, all file operations, aggregate memory or output. Invalid/overflowing limit values fail configuration; supported numeric range depends on the compiler's unsigned long.

For example, in a Windows command prompt before running a reviewed script:

set CLARO_STEP_LIMIT=10000
set CLARO_READ_FILE_LIMIT=1048576
claro98.exe practice.claro

On Linux/macOS shells the equivalent is an environment assignment before ./claro. These optional budgets do not interrupt a blocked ASK, a shell command, curl, or an individual long-running builtin. They are not untrusted-code protection.

Not provided

There is no general CPU/time budget, process isolation, total-allocation limit, global file/output limit or JSON byte-size control. The old beta names CLARO_MAX_FILE_BYTES and CLARO_MAX_JSON_BYTES are still not implemented. The newer READ FILE guard is deliberately narrower. The former unimplemented step-limit claim is preserved as history; the current step guard is the explicit implementation described above, not validation of those older promises.

Without the optional step budget ordinary intentional loops can run indefinitely. Run only trusted scripts. See reliability, errors and repairs, and the historical limits.