T81 Foundation

Deterministic Core Profile (DCP)

Status: Active Profile Line: v1.x Owner: Product/Governance

This document defines the product boundary for the T81 Deterministic Core Profile (DCP).

• T81 is the full platform (stable + experimental + research surfaces).
• DCP is the minimal stable, reproducible, versioned subset eligible for certification and release guarantees.

Normative references:

• spec/supplemental/deterministic-core-profile-v1.md
• docs/governance/DETERMINISM_SURFACE_REGISTRY.md
• docs/governance/FREEZE_ENFORCEMENT.md
• docs/governance/DETERMINISM_THREAT_MODEL.md
• docs/product/RELEASE_DISCIPLINE.md
• docs/status/STRUCTURAL_INTEGRITY_REPORT.md

A. Included in DCP (v1.x)

The following surfaces are included in DCP when they remain Verified in the Determinism Surface Registry.

Surface	Scope	Spec Reference	Verification Tests/Scripts	CI/Automation
Core Data Types	core/types/ and canonical numeric aliases in public API	spec/t81-data-types.md	tests/cpp/v1_canonical_numeric_contract_test.cpp, tests/cpp/tisc_binary_io_determinism_test.cpp	ci.yml
TISC ISA (Frozen)	opcode encoding/semantics (core/isa/)	spec/tisc-spec.md	tests/cpp/vm_determinism_property_test.cpp, tests/cpp/test_tritwise_backend_equivalence.cpp, scripts/ci/check_tisc_freeze_integrity.py	ci.yml
T81VM Interpreter (non-JIT)	reference interpreter path (core/vm/)	spec/t81vm-spec.md	tests/cpp/vm_trace_test.cpp, tests/cpp/vm_determinism_property_test.cpp	ci.yml
Soft-float / dmath	deterministic float and numeric behavior	spec/t81-data-types.md	tests/cpp/test_T81Float_arithmetic.cpp, tests/cpp/test_T81Float_rounding.cpp	ci.yml
Canonical serialization rules	canonical encodings and binary stability	spec/t81-data-types.md, spec/supplemental/cpp-mapping.md	tests/cpp/tisc_binary_io_determinism_test.cpp, tests/cpp/v1_canonical_numeric_contract_test.cpp	ci.yml
Determinism gate enforcement	reproducibility and determinism policy gates	docs/governance/DETERMINISM_SURFACE_REGISTRY.md	scripts/ci/t81lang_repro_gate.py, scripts/ci/run_determinism_slice.sh, scripts/ci/check_core_numeric_wrapper_thinness.py	repro-ledger.yml, ci.yml

DCP inclusion is controlled by the Determinism Surface Registry status. If a surface is downgraded from Verified, it is not eligible for DCP guarantees until restored.

B. Explicitly Excluded from DCP

The following are out of DCP scope unless explicitly upgraded via verified equivalence work and governance approval.

• Trace-JIT (runtime/jit/) unless equivalence is proven and registry status is upgraded.
• Experimental tiers (experimental/tiers/, including cognitive-tier surfaces) are non-DCP and non-verified unless promoted through governance and registry status upgrade.
• Hanoi VM and related experimental kernel surfaces (experimental/hanoi/).
• Distributed compute surfaces (experimental/distributed/).
• Research hardware/accelerator paths not covered by verified deterministic contracts.
• Any surface listed as Partial/Unverified/Planned in docs/governance/DETERMINISM_SURFACE_REGISTRY.md.

C. DCP Guarantees

For included DCP surfaces only:

• Bit-exact execution: identical input + configuration yields identical output/trace for supported platforms.
• Cross-architecture determinism: reproducibility across supported architectures as defined in project compatibility policy.
• Frozen semantics for DCP-covered ISA/data-type behaviors under v1.x.
• Forward compatibility discipline: DCP-compatible minors must preserve behavior of prior DCP guarantees.

Non-guarantees (outside DCP): wall-clock performance determinism, network timing determinism, and experimental/research behavior.

D. Versioning Discipline Under DCP

This section is interpreted in conjunction with docs/governance/FREEZE_ENFORCEMENT.md.

• MAJOR (x.0.0): any breaking change to DCP guarantees, frozen ISA semantics, deterministic behavior, or public API compatibility for DCP surfaces.
• MINOR (0.x.0): additive, backward-compatible DCP features that do not alter existing deterministic semantics.
• PATCH (0.0.x): bug fixes, implementation hardening, and performance work with no DCP behavioral changes.

DCP certification is broken by any unresolved regression on Verified determinism surfaces, any unapproved freeze-boundary break, or any release lacking required determinism/structural integrity evidence.

Release Readiness Requirements (DCP)

A release claiming DCP compliance must include:

• Determinism Surface Registry status snapshot.
• Determinism verification hash summary (repro gate outputs/artifacts).
• Structural integrity status from docs/status/STRUCTURAL_INTEGRITY_REPORT.md.
• Release discipline conformance from docs/product/RELEASE_DISCIPLINE.md.

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