ADR-v4-006: EvaluatorWithRunner variant + two-table Registry lookup

Status: Accepted (2026-05-25)

Context:

The single-active-role-instance evaluator needs read access to the live *PassRegistry (to count open passes on a (role, context) tuple). The existing Evaluator = func(ctx, c Clause) (*Result, error) signature has no path for this — passing the registry through Clause.Args is type-unsafe and would bypass the registry’s locks.

R9 of the v2 adversarial flagged that the v1 “EvaluatorWithRunner wraps Lookup” handwave was mechanically incorrect; Runner.Evaluate calls Registry.Lookup(c.Concept) and the runner-typed variant cannot be returned through that shape.

Decision:

Two-table Registry lookup:

• Registry.Register(concept, Evaluator) + Registry.Lookup(concept) is the plain table (existing).
• Registry.RegisterWithRunner(concept, EvaluatorWithRunner) + Registry.LookupWithRunner(concept) is the runner-typed table (new).
• A concept is registered in AT MOST ONE table. Registering in the second after the first returns ErrConceptAlreadyRegistered.

Runner.Evaluate tries LookupWithRunner first; on miss, falls back to Lookup; on second miss, returns ErrEvaluatorUnknown.

Only one concept uses the new variant today: single-active-role-instance. Adding a future runner-typed evaluator means: declare the function with the new signature, register via RegisterWithRunner.

Consequences:

• Runner.passes *PassRegistry is a new unexported field; NewRunner(reg *Registry, passes *PassRegistry, tier DepthRank) is the new constructor (replaces the prior 1-arg form).
• 37 call sites updated to pass the new args (nil and DepthRankNone are valid defaults for tests that don’t exercise the runner-typed dispatch).
• Registry.Count() reports the union of both tables — the cardinality assertion in RegisterBuiltins counts 11 across the two tables.
• Registry.Snapshot() / SwapInto() (per ADR-v4-003) duplicate both tables in lock-step.