Unhardcoded Engine Contribute

Contributing to unhardcoded-engine (Σ_pol)

This repo is the sealed core: pure Lua, no I/O, no globals, no credentials. Its value is that every host in every language computes the same decision from the same inputs, and that a policy's fingerprint is a stable identity. Every change is judged against that. Read docs/SIGMA-POL.md (the normative contract) and docs/POLICY_DESIGN.md (the rationale) before extending anything.

The architecture, by module

The pipeline for a policy-as-data (IR) term:

sig.lua       closed, versioned signature: op → { out = <sort>, ins = {<sorts>} }.  S.VERSION = "sigma-pol/v2".
term.lua      admission (check: sorts/arity/bounds/fields), normal form, deterministic encoding, fingerprint.
interp.lua    the default algebra: each op → a carrier function (the semantics).
fields.lua    the observation vocabulary + schema; hosts extend via config.fields.
elaborate.lua declarative profiles / DSL sugar → IR terms (lowering).

The closure DSL (filter.lua, rank.lua, mutate.lua, sequence.lua, policy.lua) is the local-only escape hatch — kept working, but the IR is the shipped, hashable, admitted form. sequence.lua also owns the ACTIONS vocabulary; the orchestration loop and handle_response live in llm_policy.lua.

Carrier shapes (what your interp.lua entry returns):

• Pred → fn(cand, ctx) -> bool, reason? (reason string when it rejects).
• Scorer → population-relative fn(pop, ctx) -> scores[], breakdowns[]? (score the whole candidate set at once; this is what makes normalize meaningful).
• Selector → orders the population using the seed.
• Xform → fn(request, cand, ctx) -> request' (must not mutate in place).
• FailPlan → classifies error_kind → an Action.

Adding an operator — the path

auto* = scalar params (Num/Count/Rel/…) are validated by the generic arity/sort check; you only touch term.lua when an operator needs custom admission (e.g. a field reference that must exist in the schema, or a structured param).

A new field is config-time, not a signature change. Declaring config.fields.foo = { sort="Num", default=0, get=fn(cand,ctx) } is enough; the signature never grows per-field (that's the whole point — an open field vocabulary over a closed op set). Core fields cannot be overridden.

Invariants you must not break

1. Two-runtime determinism. Same (policy, catalog, ctx, seed) ⇒ identical selection under mlua, lupa, luerl, bit-for-bit. Use only correctly-rounded IEEE ops — no transcendentals, no libm-dependent math, no os/io/globals, no wall-clock. A carrier that reads anything outside its explicit ctx breaks parity.
2. The signature is append-only within a major version. sigma-pol/v2 is a locked tag. Adding a new op is fine. Changing the semantics, arity, or encoding of an existing op rotates every policy fingerprint and breaks every stored identity/commitment — that requires a major version bump, never a silent edit. When in doubt, add a new op rather than mutate one.
3. Normal form stays canonical. AC ops flatten and sort by encoding, units drop, absorbing elements collapse, not(not p)=p, seq flattens, FailPlan collapses and sorts. Two terms that decide identically must encode identically — if your op has algebraic identities, put them in term.lua normalization or the fingerprint will over-count distinct-but-equal policies.
4. Golden vectors replay bit-for-bit. tests/golden/sigma_pol_v2.json is the language-neutral conformance set. A changed fingerprint or encoding there without a version bump is a red flag — it means you changed observable semantics. Regenerate deliberately, review the diff.
5. Purity. Verbs are pure functions of ctx; the impure orchestrator snapshots runtime state into ctx and does the I/O. Never call the host from a carrier.

Testing

lua tests/run_lua.lua          # runs the full unit suite from repo root

• Add a unit test in the matching file: tests/unit/ir_term.lua (admission, normal form, encoding), ir_interp.lua (semantics), policy_verbs.lua / declarative_policy.lua (DSL + elaboration), execute.lua / execute_step.lua (orchestration + FailPlan actions), flow_basic.lua (Σ_flow), parity.lua (declarative-vs-IR equivalence).
• For a user-facing op, add a conformance vector to the golden set:

  lua tests/golden/gen_vectors.lua      # regenerates tests/golden/sigma_pol_v2.json
  

  Review the resulting diff — a fingerprint change on an existing vector means you touched semantics; stop and reconsider (see invariant 2).
• The genvm on-chain surface has its own pytest under genvm/tests/.

Where to read more

• docs/SIGMA-POL.md — normative signature, sorts, numeric model, encoding, hashing (the contract).
• docs/POLICY_DESIGN.md — why the core is pure; the candidate object and the four verbs.
• docs/SIGMA-FLOW.md — the Σ_flow composition layer (flow.lua, sequence.lua).
• docs/GENVM-LLM-POLICY.md — the on-chain embedding and why deterministic diversity is the security property.
• The comments at the top of llm_policy/sig.lua — the append-only rule and the v2 removals, verbatim.