Irreducible core (must survive any refactor)

Non-negotiable invariants: 1) Contract alignment (INV-010): artifact and request execution_contract must match; enforced in planning and replay. 2) Determinism declaration (INV-020): ND execution requires explicit randomness + budget; deterministic path forbids ANN. 3) Provenance requirement (INV-040): replay only legal with stored execution result and matching contract/ABI. 4) Plan immutability: ExecutionPlan fingerprint ties algorithm+contract+k+randomness; mutation invalidates execution. 5) Ledger integrity: artifacts/results persisted with signatures; deletion/compaction must preserve chain hashes.

Minimum modules to enforce:

• core/runtime/execution_plan.py (plan fingerprint, randomness labels)
• core/runtime/execution_session.py (state machine, contract alignment)
• core/contracts/execution_contract.py + core/contracts/determinism.py
• domain/execution_requests/plan.py (capability + contract checks)
• domain/provenance/replay.py (provenance gate)
• core/invariants.py + core/contracts/invariants.py (guardrails)

Everything else is supportive. If removed, these must remain intact for vex to stay itself.