# Phase 22: Monitor Hardening + Schema - Context

**Gathered:** 2026-03-27
**Status:** Ready for planning
**Mode:** Auto-generated (infrastructure phase)

<domain>
## Phase Boundary

Heartbeat freshness, sidecar stability, and CH schema enforce correct Aion mode without silent fallbacks. GitHub Issue #312.

</domain>

<decisions>
## Implementation Decisions

### Claude's Discretion

All implementation choices are at Claude's discretion. Three sub-items: freshness query filter, sidecar restart investigation, CH DEFAULT review.

</decisions>

<code_context>

## Existing Code Insights

Codebase context will be gathered during plan-phase research.

</code_context>

<specifics>
## Specific Ideas

From A5 audit: \_check_aion_freshness() line 77-83 queries max(close_time_us) WITHOUT ouroboros_mode='aion' filter. From A2 audit: 5 PIDs/hour sidecar restarts.

</specifics>

<deferred>
## Deferred Ideas

None.

</deferred>
