Pins the arc's original goal against the ACTUAL serving spine (ChatRuntime,
the driver core chat constructs), not just the composer: a user asks a basic
logic question -> CORE decides -> an articulated, deterministic, telemetered
response comes back. Covers propositional + categorical, flag-off byte-identity
across both bands, honest reader-refusal on out-of-regime input (INV-34), and
the peripheral-systems wiring.
Peripheral systems verified (nothing to build, all automatic): deduction
turns are well-formed served turns (turn_log grows, _context.turn advances)
so ADR-0255 discovery-yield counts them; they carry grounding_source=
'deduction' on ChatResponse + TurnEvent and an observable DispatchAttempt;
they emit no discovery candidates (decided answer, not a would-have-grounded
gap) so they lift the yield denominator without inflating the numerator.
Scope-out doc (docs/research/deduction-serve-arc-completion-and-scope-outs-
2026-07-23.md) records the whole arc + everything deliberately deferred with
rationale: multi-word English reader relaxation (risky, shared reader, its
own pass), multi-step proof recap (Phase-6 core_logos), accrue_realized_
knowledge default, ADR-0246 s3.7 (blocked on research evidence not wiring),
Tier-2 (waits for field reader), Hamiltonian compiler (eval-side), and the
GroundingSource enum registration.
New: tests/test_deduction_serve_e2e.py (5 tests through the real REPL path).
[Verification]: core test --suite deductive 50 passed; smoke 180 passed;
cognition 122 passed/1 skipped.
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