# Batch 91 Report — AZ-620 Phase B: build_pre_constructed seeds c6_descriptor_index + c6_tile_store (cycle 1)

**Batch**: 91
**Date**: 2026-05-19
**Context**: Product implementation (greenfield Step 7 — Implement; AZ-618 umbrella, Phase B of 6)
**Tasks**: AZ-620 (3 cp) — 1 task
**Cycle**: 1
**Verdict**: COMPLETE — PASS (self-reviewed inline; 15/15 runtime_root tests green)

## Summary

Second of six subtasks decomposing the AZ-618 umbrella. Phase B extends `airborne_bootstrap.build_pre_constructed(config)` additively, adding the two C6 storage entries (`c6_descriptor_index`, `c6_tile_store`) on top of AZ-619's foundational `c13_fdr` + `clock`. Wraps the existing C6 factories so a `BUILD_FAISS_INDEX=OFF` mismatch surfaces a clear operator-facing `AirborneBootstrapError` instead of bubbling up the lower-level `RuntimeNotAvailableError` with no consuming-component context.

### AZ-620 — build_pre_constructed Phase B (3 cp)

* **`src/gps_denied_onboard/runtime_root/airborne_bootstrap.py`**:
  * Imports `build_descriptor_index` + `build_tile_store` from `storage_factory`, and `RuntimeNotAvailableError` from `errors`.
  * New public constant `FAISS_BUILD_FLAG = "BUILD_FAISS_INDEX"` (exported in `__all__`) — single source of truth for the flag name embedded in error messages.
  * New module-private helpers:
    * `_consumers_of_pre_constructed_key(key)` — reads `AIRBORNE_REQUIRED_PRE_CONSTRUCTED_KEYS` to find which slugs need a given key.
    * `_configured_consumers_of_pre_constructed_key(config, key)` — narrows to consumers present in `config.components`; falls back to the full theoretical set when no components are configured (so error messages stay informative under bare `Config()`).
    * `_build_c6_descriptor_index(config)` — calls `build_descriptor_index`; on `RuntimeNotAvailableError`, re-raises as `AirborneBootstrapError` naming `c6_descriptor_index`, `BUILD_FAISS_INDEX`, and the consuming component slug(s). Preserves the original error via `raise ... from exc`.
    * `_build_c6_tile_store(config)` — thin pass-through to `build_tile_store` (no `BUILD_*` flag gates this side).
  * `build_pre_constructed(config)` now returns four keys: `c13_fdr`, `clock`, `c6_descriptor_index`, `c6_tile_store`. Additivity preserved per AZ-620 Constraint "MUST be additive on top of AZ-619".
  * Bonus hygiene (mechanical): `ruff --fix` removed 12 pre-existing UP037 quoted-annotation warnings in the same file (covered by `from __future__ import annotations` at line 49). All 12 lints were in the modified-area scope per `.cursor/rules/quality-gates.mdc`.

* **`tests/unit/runtime_root/test_az619_pre_constructed_phase_a.py`**:
  * New autouse fixture `_stub_c6_builders` monkeypatches `_build_c6_descriptor_index` + `_build_c6_tile_store` to opaque sentinels — keeps AZ-619 tests focused on Phase A keys without entangling them with the new Phase B integration paths (and avoids requiring real Postgres + FAISS for the AZ-619 cases).
  * `test_phase_a_only_seeds_two_keys` renamed to `test_phase_a_keys_remain_present_under_az620_additivity`: now asserts AZ-619 keys are a SUBSET of the returned dict (not exact equality), matching the explicit forward-pointer that the original docstring carried ("this test will be relaxed at that point").

* **`tests/unit/runtime_root/test_az620_pre_constructed_phase_b.py`** (new):
  * `test_ac_620_1_adds_c6_descriptor_index_and_c6_tile_store` — stubs both C6 factories to identifiable mocks; asserts the bootstrap dict contains both Phase B keys referencing the patched returns, and AZ-619 keys are still present. Covers AC-620.1.
  * `test_ac_620_2_build_flag_off_with_configured_c2_vpr_raises_named_error` — stubs `build_descriptor_index` to raise `RuntimeNotAvailableError` (mirroring real `BUILD_FAISS_INDEX=OFF` behaviour); builds a config with `c2_vpr.strategy="net_vlad"`; asserts `AirborneBootstrapError` is raised with all three names (`c6_descriptor_index`, `BUILD_FAISS_INDEX`, `c2_vpr`) and the original error preserved as `__cause__`. Covers AC-620.2.
  * `test_ac_620_2_no_configured_consumer_still_raises_with_full_set` — defence-in-depth: even with no consumer configured, the bootstrap still fails loudly (rather than silently dropping the key); the message lists the full theoretical consumer set. Strengthens AC-620.2's operator-facing contract.

## File Ownership

* OWNED (component `runtime_root`):
  * `src/gps_denied_onboard/runtime_root/airborne_bootstrap.py`
  * `tests/unit/runtime_root/test_az619_pre_constructed_phase_a.py`
  * `tests/unit/runtime_root/test_az620_pre_constructed_phase_b.py`
* READ-ONLY: imports from `runtime_root.storage_factory` (same package), `runtime_root.errors`, `clock`, `fdr_client`, `config`, `c6_tile_cache.interface` (TYPE_CHECKING via storage_factory only).
* No FORBIDDEN-zone writes.

## Test Results

* New unit tests: **3** under `tests/unit/runtime_root/test_az620_pre_constructed_phase_b.py` covering AC-620.1 + AC-620.2 (twice, defence-in-depth).
* Updated unit tests: **5** AZ-619 tests still passing after autouse-stub fixture and relaxed-equality assertion.
* AZ-591 regression (`test_az591_airborne_bootstrap.py`): **7/7 passing** — `AIRBORNE_REQUIRED_PRE_CONSTRUCTED_KEYS` table consistency + airborne registration semantics + tier isolation all unchanged.
* Combined: `pytest tests/unit/runtime_root/ -q` → **15/15 passed in 1.06 s**.
* No new ruff errors on touched files; 12 pre-existing UP037 warnings in the same file fixed.

## Out of scope (deferred)

* All other keys in `AIRBORNE_REQUIRED_PRE_CONSTRUCTED_KEYS` — AZ-621 (c7 inference), AZ-622 (c3 runtimes), AZ-623 (RANSAC + c5 helpers), AZ-624 (`main()` integration + AC-1..AC-5).
* Real Postgres + FAISS integration testing — covered by the existing AZ-303 / AZ-305 / AZ-306 component-level tests; not duplicated at the bootstrap layer.
* Mandatory-Tier-2 Jetson run — consolidated at AZ-624.

## State

* Spec moved: `_docs/02_tasks/todo/AZ-620_pre_constructed_phase_b_c6_storage.md` → `_docs/02_tasks/done/`.
* Tracker: AZ-620 transitioned **To Do → In Progress** at batch start; will transition **In Progress → In Testing** after this commit (per implement skill Step 12).
* `_docs/_autodev_state.md` advanced to `last_completed_batch: 91`.

## Next Batch

* **Batch 92**: AZ-621 (3 cp) — Phase C of AZ-618 umbrella. Adds `c7_inference` engine to `build_pre_constructed`. Depends on AZ-619 + AZ-620 (both will be in `done/` after this commit).
