05 — PgStructureStore, Auto-cut Bridge, Delivery Seam

Python PgStructureStore — live SQL-backed driver

cutter_agent/iu_core/pg_structure_store.py — PgStructureStore is the live counterpart of the in-memory InMemoryStructureStore test seam. It delegates the whole plan→apply→verify→rollback envelope to the SQL execution layer of record (fn_iu_structure_op_*).

Deliberate architecture: the SQL layer owns every safety property (structure-op gate, IU Gateway write guard, fn_iu_create birth gate, acyclicity assertion, compensation snapshot). PgStructureStore is a thin typed driver — it never re-implements tree logic in Python and never writes a table directly. Driving the granular StructureStore Protocol against Postgres would bypass those gates; the live path goes through them.

Interface: structure_ops_enabled(), plan(StructureOpRequest) → op_id, apply/verify/rollback(op_id) → PgStructureOpResult, drive(request) — the workflow-equivalent plan→apply→verify. Takes any DB-API 2.0 connection; imports no driver → import-safe without a database, unit-testable with a recording fake connection (10 executable tests).

Auto-cut bridge — birth-gate handshake wiring

autocut_bridge.py gained BirthSpec — the IU birth attributes (canonical_address/title/body/unit_kind/section_type) a cut must supply for every new piece. CutResultUnit.birth_spec carries it; map_cut_to_structure_ops puts it into payload['new_pieces'] — the same birth-gate handshake the migration-012 SQL apply consumes.

End-to-end proof: CutResult with BirthSpec → AutocutBridge → StructureOpRequest with new_pieces → PgStructureStore.drive() → verdict.ok. The add/split mapping was also proven DB-backed in sandbox/070 P9 (autocut-mapped add_new_piece applies ok, past feature_not_supported).

Delivery seam — next-step package (NOT executed)

dry_run=false remains a separate sovereign macro. Current: fn_iu_route_ deliver RAISEs feature_not_supported; every structure route dry_run=true; CHECK iu_outbound_route_safe_chk makes enabled+dry_run=false impossible.

Concrete dry_run=false package:

1. Build fn_iu_route_deliver with a sql_function consumer — fn_iu_structure_consumer(event_ref, safe_payload) recording an iu_tree_change_log projection. In-PG, no network, idempotent on event_ref.
2. Relax the route CHECK per-route — keep the blanket CHECK; add a dot_config allowlist (iu_core.delivery_live_routes) + a guard.
3. Add dot_config 'iu_core.delivery_enabled' — dedicated fail-closed kill-switch.
4. Rollback/disable package — stub restore, route → dry_run=true, close the gate, dead-letter replay, truncatable projection.

The Python contract exists (delivery_seam.py — target-kind vocabulary, request/outcome shapes, UnbuiltDeliveryTarget fail-closed default). Blast radius strictly larger than dry-run — sovereign macro.