---
phase: 14-rust-core-gap-fields-conditional-reset
plan: 02
subsystem: streaming-engine
tags: [ouroboros, aion-mode, midnight-reset, conditional-reset]
dependency_graph:
  requires: []
  provides: [OuroborosMode-enum, conditional-midnight-reset]
  affects: [live_engine, trade_dispatch, puck, symbol_task]
tech_stack:
  added: []
  patterns: [enum-default-derive, conditional-dispatch]
key_files:
  created: []
  modified:
    - crates/opendeviationbar-streaming/src/live_engine/types.rs
    - crates/opendeviationbar-streaming/src/live_engine/trade_dispatch.rs
    - crates/opendeviationbar-streaming/src/live_engine/symbol_task.rs
    - crates/opendeviationbar-streaming/src/live_engine/puck.rs
    - crates/opendeviationbar-streaming/src/live_engine/mod.rs
decisions:
  - OuroborosMode placed in streaming crate types.rs (co-located with DAY_US constant and other bar construction types)
  - All call sites default to Day mode for backward compatibility, with TODO comments for Phase 16 wiring
  - Puck gap-fill also defaults to Day mode (gap fills during Aion will be handled in Phase 16)
metrics:
  duration: 43min
  completed: "2026-03-27T06:24:00Z"
---

# Phase 14 Plan 02: Conditional Midnight Reset Summary

OuroborosMode enum with Day/Aion variants added to streaming crate; maybe_reset_at_midnight returns None for Aion mode (no midnight reset), Day mode unchanged

## What Was Done

### Task 1: Add OuroborosMode enum and make midnight reset conditional

Added `OuroborosMode` enum to `types.rs` with `Day` (default) and `Aion` variants. Modified `maybe_reset_at_midnight` to accept the mode parameter -- Aion mode early-returns `None` (still tracks day for metrics but never triggers processor reset). Threaded `ouroboros_mode` through `process_trade_through_processors` as the last parameter.

Updated all 7 call sites across 4 files:

- `symbol_task.rs`: 3 call sites (junction fill, WS buffer drain, main trade loop)
- `puck.rs`: 1 call site (gap fill midnight reset)
- `mod.rs`: 1 call site (REST chunk processing) + 2 test call sites

All call sites pass `OuroborosMode::Day` as default. `OuroborosMode` is re-exported from `live_engine` public API for Phase 16 consumption.

**Commit:** bef25a4

## Verification Results

1. `cargo check -p opendeviationbar-streaming` -- PASSED (clean compilation)
2. `cargo check -p opendeviationbar-py` -- PASSED (PyO3 crate depends on streaming)
3. `cargo nextest run -p opendeviationbar-streaming --lib` -- 35/35 tests PASSED
4. All call sites use `OuroborosMode::Day` as default (verified via grep: 7 call sites)

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 3 - Blocking] Fixed duplicate import conflict**

- **Found during:** Task 1 verification
- **Issue:** Added `use types::OuroborosMode` import in mod.rs but `pub use types::{..., OuroborosMode, ...}` already brought it into scope, causing E0252 (name defined multiple times)
- **Fix:** Removed the redundant `use types::OuroborosMode;` line
- **Files modified:** `mod.rs`
- **Commit:** bef25a4 (included in task commit)

**2. [Rule 2 - Missing call sites] Updated puck.rs and mod.rs call sites not listed in plan**

- **Found during:** Task 1 (grep for maybe_reset_at_midnight)
- **Issue:** Plan only mentioned symbol_task.rs and mod.rs tests, but `puck.rs` line 84 and `mod.rs` line 557 also call `maybe_reset_at_midnight` directly
- **Fix:** Added `OuroborosMode::Day` parameter to both call sites
- **Files modified:** `puck.rs`, `mod.rs`
- **Commit:** bef25a4

## Known Stubs

None -- all code paths are fully wired. The `OuroborosMode::Day` defaults are intentional placeholders that Phase 16 will replace with actual symbol config values.

## Self-Check: PASSED

- All 5 modified files exist on disk
- Commit bef25a4 verified in git log
