task-51 - Specializer-raw-dict-output-mode-—-close-the-python_dict-gap-opt-in.md

id	TASK-51
title	Specializer raw-dict output mode — close the python_dict gap (opt-in)
status	Done
assignee
created_date	2026-07-26 20:17
labels
milestone	m-7
dependencies	TASK-50
type	feature
ordinal	45000

Acceptance Criteria

• #1 output='dict' opt-in on DuckDBInferFn; typed default untouched; mutually exclusive with output_model; unknown values rejected
• #2 All four emit paths honor it (marshaller, generic fallback, reentrant, constant engine) with fresh dicts per call
• #3 Parity: dict mode == typed mode field-for-field, enforced in the serving parity gate + oracle tests
• #4 Bench: spec_dict engine row lands the python_dict head-to-head
• #5 gate green

Final Summary

Raw-dict output shipped as a strict opt-in: DuckDBInferFn(..., output="dict") returns per-row plain dicts, skipping model construction — the marshaller already built the dict the model would consume, so the modes agree field-for-field by construction (enforced in the serving parity gate and tests). All four emit paths honor the mode (generated marshaller, generic baseline, reentrant fallback, constant engine — the latter copying per call so caller mutation cannot leak). Guards: mutually exclusive with output_model, unknown values rejected, output getter exposes the mode. Measured at n=1024: 25-35% off the typed path; the handcrafted python_dict floor shrinks from the standing 1.3-2x caveat to 0.74-1.11x (spec_dict WINS house_prices) — the remaining gap is input marshalling, not output. Gate green (759 + 13 xfail); 6 new tests + parity-gate extension + spec_dict bench engine.