T81 Foundation

Guide: Runtime Contract Helpers

This guide covers new low-level helpers used to harden determinism and safety checks in runtime flows.

TISC Opcode Contract Helpers

Header: include/t81/isa/opcodes.hpp

Added helpers:

• t81::tisc::opcode_name(Opcode)
• t81::tisc::kAllOpcodes
• t81::tisc::is_valid_opcode(std::uint8_t)

Typical use cases:

• Building complete opcode matrix tests.
• Centralized decode validation.
• Stable opcode name rendering in logs and tooling.

core/isa/encoding.cpp now uses is_valid_opcode(...) so decode acceptance tracks the full enum range through MetaRefine.

VM Safety Counters

Header: include/t81/vm/state.hpp

Added state fields:

• call_depth
• contradiction_events

Runtime behavior in core/vm/vm.cpp:

• Call enforces a hard recursion ceiling and records a security event when exceeded.
• Ret decrements tracked depth and increments contradiction count when depth underflows.
• Axion call context now reports recursion depth from max(stack_frames.size(), call_depth).

Related reason keys in include/t81/axion/reasons.hpp:

• kRecursionCeiling
• kContradictionDetected

These checks provide deterministic guardrails while preserving existing VM control-flow semantics.

This site is open source. Improve this page.