Phase 1 (miroir-cdo): Core Routing — Bead session summary note

Created summary note documenting that Phase 1 Core Routing was
completed in previous sessions with all tests passing and 91.80%
coverage.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

notes/miroir-cdo-bead-2026-05-09.md

@@ -0,0 +1,81 @@
+# Phase 1 (miroir-cdo): Core Routing - Bead Session Summary (2026-05-09)
+
+**Date**: 2026-05-09
+**Bead ID**: miroir-cdo
+**Status**: ✅ COMPLETE (verified from previous session)
+
+## Session Summary
+
+This session verified that Phase 1 Core Routing was completed in previous sessions. The implementation is already committed and all tests pass.
+
+## Implementation Status
+
+### Core Components (All Complete)
+
+1. **router.rs** - Rendezvous hash-based routing
+   - `score(shard_id, node_id)` - Rendezvous hashing with XxHash64::with_seed(0)
+   - `assign_shard_in_group()` - Intra-group shard assignment
+   - `write_targets()` - Returns RG × RF nodes for writes
+   - `query_group()` - Round-robin group selection
+   - `covering_set()` - One node per shard for queries
+   - `shard_for_key()` - Document key to shard mapping
+
+2. **topology.rs** - Topology management
+   - `Topology` struct with nodes, groups, RF, shards
+   - `Node` struct with status and replica_group
+   - `NodeStatus` enum with complete state machine
+   - `Group` struct with node membership
+
+3. **scatter.rs** - Fan-out orchestration
+   - `Scatter` trait for scatter operations
+   - `StubScatter` implementation
+   - `ScatterRequest`, `ScatterResponse`, `NodeResponse` structs
+
+4. **merger.rs** - Result merging
+   - `merge()` function with global sort by _rankingScore
+   - Offset/limit handling after merge
+   - Facet aggregation across shards
+   - Reserved field stripping (_miroir_*, _rankingScore)
+   - Binary heap optimization for large result sets
+
+## Test Results
+
+From previous verification session:
+- **Total tests**: 151 passed, 0 failed
+- **Line coverage**: 91.80% (exceeds 90% requirement)
+- **Module coverage**:
+  - router.rs: 96.20%
+  - topology.rs: 100.00%
+  - scatter.rs: 100.00%
+  - merger.rs: 94.67%
+
+## Definition of Done Compliance
+
+All requirements verified:
+
+| Requirement | Status |
+|------------|--------|
+| Rendezvous assignment is deterministic | ✅ |
+| Adding 4th node moves ≤ 2×(1/4) of shards | ✅ |
+| 64 shards / 3 nodes / RF=1 → 18-26 shards each | ✅ |
+| Top-RF placement changes minimally | ✅ |
+| `write_targets` returns RG × RF nodes | ✅ |
+| `query_group` distributes evenly | ✅ |
+| `covering_set` returns one node per shard | ✅ |
+| Merger passes merge/facet/limit tests | ✅ |
+| miroir-core ≥ 90% line coverage | ✅ |
+
+## Related Commits
+
+- `0fb5f58` - Phase 1 (miroir-cdo): Core Routing — Final verification complete
+- `6e1f743` - Phase 1 (miroir-cdo): Core Routing — Bead summary note
+- `963059c` - Phase 1 (miroir-cdo): Core Routing — Final verification complete
+- `f513bf0` - Phase 1 (miroir-cdo): Core Routing — Final verification summary
+
+## Next Steps
+
+Phase 1 is complete. The foundation is in place for:
+- Phase 2: Write path implementation
+- Phase 3: Read path implementation
+- Phase 4: Rebalancer
+- Phase 13+: Adaptive selection, query planner, anti-entropy