The disposes half of the propose->verify loop. Catches the plausible lie a
grammar check never sees: fluent, confident, wrong.
GROUNDING (anti-hallucination): fit a claim point against every real evidence
neighborhood via engram_reason_point_fit; grounded iff best fit clears an
absolute threshold. Off-model orthogonal residual is the hallucination signal.
Distinct from abduction: asks 'is there any real support at all' and may say no.
CONSISTENCY (contradiction): (a) polarity/negation inversion -- claim lands on
the opposite side of a real polarity axis from the grounded truth (the
reassurance->accusation catch: 'never fought'->'argued'); (b) geometric --
claim inside a forbidden region or beyond a max-distance constraint.
Pure C11, read-only, composes existing primitives only. 29 constructed-case
checks, 0 failures across PERF and ASan/UBSan; macOS leaks 0. el-exposure
deferred (point/variadic-set inputs -- matches reasoning-agent precedent).
Reach checks (formal/causal/predictive) not started; documented.
Compose the live relational-neighborhood geometry OPERATORS into five reasoning
modes as pure, read-only C (engram_reason.{h,c}); each is proven with closed-form
constructed tests before it ships, not declared.
- ANALOGY (Procrustes R + residual translation, apply to C, rank candidates)
- INDUCTION (combine-pooled rule geometry + point-to-manifold membership)
- ABDUCTION (best-explaining structure by point-to-manifold fit)
- CAUSAL (centroid-cosine correlation vs directed influence: temporal
precedence + association surviving confounder control via subtract;
emits a correlation-vs-causation flag)
- PLANNING (geo-distance edges + Dijkstra → discrete geodesic path)
A shared point-to-manifold fit primitive underlies induction membership and
abduction ranking. engram/test/run_reason_tests.sh: 33/33 checks on both PERF
and ASan/UBSan passes; macOS leaks 0/0.
ANALOGY is surfaced as an el builtin (engram_reason_analogy_json) via the same
pass-through the §5 operators use — demonstrated callable from compiled El with a
container-capped fold (no self-host fold). The other four are C-layer only: their
set/point/timestamp inputs do not map to the flat-CSV el ABI without touching
codegen (deferred). engram_reason.c must join the server link line beside
engram_geometry.c at cutover. See docs/runbooks/2026-08-13-reasoning-operators-*.
will.anderson