12000x · 09 — Lessons + carry-forward

Lessons (new this macro)

L1 — Live discovery before authoring is non-negotiable

The 11000x brief said five Product Factory primitives "remain to implement" and listed them as 12000x work. Live discovery in dot_iu_command_catalog, pg_proc, and cutter_agent/iu_core/*.py showed THE SUBSTRATE IS ALREADY SHIPPED. Running the brief verbatim would have produced redundant code that fights existing FK/CHECK invariants.

Rule: read \df, \d, dot_iu_command_catalog, and the Python module surface BEFORE drafting a migration. The brief is a hypothesis, not ground truth.

L2 — In-tx gate-toggle is a clean reversibility pattern

The composer (iu_core.composer_enabled) and event-emit (piece_event_runtime.emit_enabled) gates default to false in production. Inside BEGIN/ROLLBACK, UPDATE dot_config SET value='true' WHERE key=… flips them for the duration of the TX and the ROLLBACK reverts the row, leaving durable state untouched.

Rule: use the gate-toggle-in-tx pattern when a brief says "exercise the substrate without affecting production." Pair it with post-rollback durability check on the affected tables AND on the gate values themselves.

L3 — fn_iu_compose already supports both branches: {new_piece:{…}} and {iu_id:<uuid>}

11000x docs emphasized the new_piece branch (mint+attach). The iu_id branch (reuse-existing) was inside the same function body but had no live exerciser. Phase F is the first production-shape proof — it is the mechanism for generate_instance_from_template.

Rule: don't write a new "instance" function. Use the existing iu_id branch — already governed by composer gate + birth-gate + manifest-refresh pipeline.

L4 — Manifest digest is keyed on the piece graph

Phase F headline: template digest = instance digest. The hash function ignores collection_key, title, description. Two collections with the same (piece_order, iu_id, piece_role, collection_kind) sequence are IDENTICAL content artefacts by digest, even if they belong to different business products.

Rule: when indexing collections downstream (Qdrant, audit, text-as-code ledger), key on manifest_digest to dedupe across instances; key on collection_key to distinguish business identity. Both, not either.

L5 — Birth gate L1 PILOT-ONLY warnings are pre-existing noise

fn_iu_birth_gate_layer1 emits "P-pub1/P-pub2 missing — production sẽ BLOCK" warnings on every design_doc_section IU create. Function still returns; IU is created. Not 12000x defects but they pollute transcripts (14 emissions in Phase D alone).

Rule: triage in 13000x — either silence under a "pilot OK" config or replace with a single summary line per macro. Not blocking this PASS.

Carry-forward to 13000x

Substrate (author-mode candidates, not blockers)

1. iu_piece_collection.source_collection_id uuid FK + relation_kind text — promote description-based template lineage proven in Phase F to a queryable FK.
2. source_axis_kind += 'instance' — distinguish in-place compositions from template-derived ones.
3. Manifest-digest-keyed text-as-code ledger — iu_collection_text_as_code_anchor(manifest_digest text PK, latest_path, first_seen_at, last_seen_at) so byte-identical roundtrip (Phase 07) becomes durably indexable.

Execution proofs (gated)

4. End-to-end durable apply of propose_collection_import result — currently APPLY_IS_DESTRUCTIVE=False; build durable applier behind a third gate (text_as_code.apply_enabled=false default).
5. Live mode for piece events — piece_event_runtime.dry_run_only=false in bounded BEGIN/ROLLBACK to confirm delivery seam carries actual piece events past in-tx outbox.
6. Mac-host PILOT-noise triage — see L5.

Constitution-preserving operations

7. PR #669 merge — owned by frontend/DevOps; do not merge from a macro.
8. Retention enable — earliest eligible ~2026-06-22 (see feedback_authority_discovery_real_verify).
9. Nuxt deploy — owned externally.

Carry-forward to AgentData memory layer

Three new memory entries proposed:

• feedback_in_tx_gate_toggle_reversibility — pattern from L2.
• feedback_manifest_digest_keyed_on_piece_graph — property from L4.
• feedback_compose_iu_id_branch_is_instance_mechanism — L3.

Cross-references

• 11000x baseline: [[project_dot_iu_cutter_v0_6_iu_core_11000x_piece_event_runtime_product_factory]]
• 10000x defect re-verified by live INSERT round-trip (G.F): [[feedback_event_outbox_check_vs_registry_drift]]
• Trigger-over-fn-rewrite design respected: [[feedback_trigger_emit_over_fn_rewrite]]
• Healthcheck SQL parity rule: [[feedback_healthcheck_sql_must_match_db_check]]