# Batch 55 — Cycle 1 Report

**Date**: 2026-05-14
**Tasks**: AZ-528 (Hygiene — c1_vio strategy facade orchestration-spine consolidation)
**Verdict**: COMPLETE — PASS

## Summary

Consolidated the 3-way orchestration-spine duplication across the
c1_vio `VioStrategy` modules (`okvis2.py`, `vins_mono.py`,
`klt_ransac.py`) into a single c1-internal helper module
`_facade_spine.py`. Closes cumulative review batches 52-54 Finding
F1 (Medium / Maintainability). Mirrors the AZ-527 precedent for the
c2_vpr-side `_assert_engine_output_dim` consolidation. No behaviour
change — every existing AZ-332 / AZ-333 / AZ-334 AC test passes
unmodified.

## Files added / modified

### Added (2)

- `src/gps_denied_onboard/components/c1_vio/_facade_spine.py` — new
  c1-internal helper, 225 lines. Exports 5 free functions (`now_iso`,
  `bias_norm`, `se3_from_4x4`, `frame_ts_ns`, `frame_image`) and the
  `FacadeSpine` mixin class (`_classify_state`, `_tick_lost`,
  `_emit_transition`).
- `tests/unit/c1_vio/test_az528_facade_spine.py` — new test file, 19
  tests covering AC-1..AC-8 + a Risk-1 mitigation test (each
  strategy's `__init__` statically asserts that every spine-required
  attribute is assigned). All pass.

### Modified (3)

- `src/gps_denied_onboard/components/c1_vio/okvis2.py` — inherit from
  `FacadeSpine`; import the 5 free functions; delete the 5 local
  module-level definitions, 3 instance methods, and the unused
  `_BIAS_NORM_FLOOR` constant. Set the 3 spine-required attributes
  (`_feature_threshold`, `_producer_id`, `_strategy_label`) in
  `__init__`.
- `src/gps_denied_onboard/components/c1_vio/vins_mono.py` — same
  pattern as `okvis2.py`.
- `src/gps_denied_onboard/components/c1_vio/klt_ransac.py` — same
  pattern; spine threshold reads `self._cfg.min_features_for_pose`
  (the KLT-side equivalent of OKVIS2's `degraded_feature_threshold`).
  Deferred-consolidation comments referencing this PBI removed.

## Tests

- `tests/unit/c1_vio/test_az528_facade_spine.py` — 19 new tests, all
  pass.
- `tests/unit/c1_vio/` (full focused suite) — 120 collected, 114
  pass + 6 tier-2 skipped (unchanged from pre-AZ-528 state).
- Adjacent regression suite (`test_az270_compose_root`,
  `test_az272_fdr_record_schema`, `test_az273_fdr_client_ringbuf`,
  `test_ac1_scaffold_layout`, `tests/unit/c1_vio/`) — 237 pass + 6
  skipped.

## AC traceability

| AC    | Status | Notes                                                   |
|-------|--------|---------------------------------------------------------|
| AC-1  | ✓      | Helper module exposes documented surface.               |
| AC-2  | ✓      | `now_iso()` returns aware UTC `+00:00` ISO-8601.        |
| AC-3  | ✓      | `bias_norm` matches L2 formula (accel + gyro).          |
| AC-4  | ✓      | `se3_from_4x4` builds `gtsam.Pose3` identity correctly. |
| AC-5  | ✓      | `_classify_state` INIT during warmup, T/D thresholds.   |
| AC-6  | ✓      | `_tick_lost` demotes T→D first call, escalates to LOST. |
| AC-7  | ✓      | `_emit_transition` exactly one FDR record per change.   |
| AC-8  | ✓      | AST guard: 0 module-level free funcs in 3 strategies.   |
| AC-9  | ✓      | All AZ-332 / AZ-333 / AZ-334 AC tests pass unmodified.  |
| AC-10 | ✓      | AZ-270 layer-lint regression still passes.              |

## Code review

See `_docs/03_implementation/reviews/batch_55_review.md` — verdict
PASS, no findings.

## Outcomes & lessons

- Pattern of an "AST regression guard against duplicated free
  functions" continues to work well (AZ-508 / AZ-526 / AZ-527 /
  AZ-528 all use it). It catches re-introduction by future authors
  who don't know the consolidated home exists.
- Mixin-via-instance-attributes (rather than constructor parameters)
  keeps strategy `__init__` signatures stable — the AZ-331 factory
  signature `(config, *, fdr_client)` is preserved across all three
  strategies post-refactor.
- A 3-point hygiene PBI was the right granularity: 1 new module,
  3 small edits to existing strategies, 1 test file with AST + import
  regression guards. Same shape and complexity as AZ-527.

## Outstanding

None for AZ-528. F2 from cumulative review batches 52-54 (test fake
+ `_patch_pose_recovery` helper consolidation) remains deferred —
sits at a different abstraction layer and will ride a later hygiene
pass.