---
phase: 02-seeder-day-boundary-backfill
plan: 01
subsystem: scripts
tags: [seeder, parquet, crossover, day-boundary, backfill, binance-rest]

# Dependency graph
requires:
  - phase: 01-crossover-tid-utility
    provides: "get_crossover_tid(symbol, date) shared utility"
provides:
  - "_backfill_yesterday_boundary() function in tick_cache_seeder.py"
  - "Post-midnight backfill of yesterday's Parquet to crossover TID boundary"
  - "State marker dedup in ~/.cache/opendeviationbar/seeder-state/"
affects: [03-kintsugi-parquet-trust, 04-heartbeat-coverage, 05-documentation]

# Tech tracking
tech-stack:
  added: []
  patterns: ["state-marker-based once-per-day execution guard"]

key-files:
  created:
    - tests/test_seeder_day_boundary.py
  modified:
    - scripts/tick_cache_seeder.py

key-decisions:
  - "State marker location: ~/.cache/opendeviationbar/seeder-state/ (user cache, not repo)"
  - "Backfill runs at top of _seed_symbol() before _find_missing_days, spot market only"
  - "Complete files also get state marker written to avoid repeated crossover TID lookups"

patterns-established:
  - "State marker pattern: {cache_sym}_boundary_{date}.done file prevents re-runs"

requirements-completed: [SEED-01, SEED-02]

# Metrics
duration: 3min
completed: 2026-03-25
---

# Phase 2 Plan 1: Seeder Day-Boundary Backfill Summary

**Post-midnight backfill of yesterday's Parquet file to crossover_tid - 1 using shared crossover utility, with state marker dedup and 5 unit tests**

## Performance

- **Duration:** 3 min
- **Started:** 2026-03-25T07:53:18Z
- **Completed:** 2026-03-25T07:56:20Z
- **Tasks:** 1 (TDD: RED + GREEN)
- **Files modified:** 2

## Accomplishments

- Added `_backfill_yesterday_boundary()` to seeder that detects incomplete yesterday Parquet (max TID < crossover_tid - 1) and fetches missing trailing trades via REST
- State marker in `~/.cache/opendeviationbar/seeder-state/` prevents redundant backfill runs within the same UTC day
- Wired into `_seed_symbol()` for spot market only -- runs on every 5-min invocation but state marker makes it effectively once-per-day
- 5 unit tests cover: incomplete backfill, complete skip, crossover failure skip, missing file skip, state marker dedup

## Task Commits

Each task was committed atomically:

1. **Task 1 RED: Failing tests** - `bf4f6d0` (test)
2. **Task 1 GREEN: Day-boundary backfill implementation** - `0f5a6ea` (feat)

## Files Created/Modified

- `tests/test_seeder_day_boundary.py` - 5 unit tests for day-boundary backfill logic with mocked Binance REST and storage
- `scripts/tick_cache_seeder.py` - Added `_backfill_yesterday_boundary()` function (130 lines) + wiring into `_seed_symbol()`

## Decisions Made

- State marker location: `~/.cache/opendeviationbar/seeder-state/` -- consistent with other seeder state files in user cache dir
- Backfill runs at the top of `_seed_symbol()` before `_find_missing_days` -- ensures yesterday completeness before processing today
- Complete files also get a state marker to avoid repeated crossover TID REST lookups on subsequent 5-min invocations
- Fixed pre-existing ruff RUF003 warnings (ambiguous Unicode multiplication sign in comments)

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 3 - Blocking] Fixed pre-existing ruff RUF003 lint errors**

- **Found during:** Task 1 GREEN (commit attempt)
- **Issue:** Pre-existing ambiguous Unicode `x` (MULTIPLICATION SIGN) in comments triggered ruff check
- **Fix:** Replaced `x1000` with `x1000` in two comments
- **Files modified:** scripts/tick_cache_seeder.py
- **Verification:** ruff passes, commit succeeds
- **Committed in:** 0f5a6ea (part of GREEN commit)

---

**Total deviations:** 1 auto-fixed (1 blocking)
**Impact on plan:** Trivial comment fix to pass pre-commit linting. No scope creep.

## Issues Encountered

None

## User Setup Required

None - no external service configuration required.

## Known Stubs

None - all data paths are fully wired (crossover TID lookup, REST fetch, Parquet write).

## Next Phase Readiness

- Yesterday's Parquet files will now be complete (max TID == crossover_tid - 1) after the first post-midnight seeder run
- Phase 3 (Kintsugi Parquet Trust) can now verify Parquet completeness using the same crossover TID
- Phase 4 (Heartbeat Coverage) can extend yesterday completion checks to all streaming symbols

## Self-Check: PASSED

- [x] tests/test_seeder_day_boundary.py exists
- [x] scripts/tick_cache_seeder.py exists
- [x] Commit bf4f6d0 exists (RED)
- [x] Commit 0f5a6ea exists (GREEN)

---

_Phase: 02-seeder-day-boundary-backfill_
_Completed: 2026-03-25_
