store: Overlap Memories Duplicated to Both Target Graphs During Migration

graph/decisions/overlap-memories-duplicated-to-both-target-graphs-during-mig-e30109.md

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+---
+id: e301095c-7d4c-45d8-8352-9491e4ad6603
+type: decision
+title: "Overlap Memories Duplicated to Both Target Graphs During Migration"
+tags: [cognitive-memory, migration, multi-graph, decision, overlap]
+importance: 0.7
+confidence: 0.8
+created: "2026-03-01T22:16:56.955400+00:00"
+updated: "2026-03-01T22:16:56.955400+00:00"
+---
+
+# Decision: Copy Overlap Memories to Multiple Target Graphs
+
+## Context
+During migration of memories from default graph to named project graphs, some memories are tagged for multiple projects (e.g., both `major-domo` and `paper-dynasty`).
+
+## Decision
+Overlap memories are **COPIED** (not moved) to each matching target graph. They remain in the default graph until all migrations complete, then the `--cleanup-overlaps` flag removes them from default.
+
+## Rationale
+- Preserves memory context in both project graphs where it's relevant
+- Avoids data loss if migration is interrupted partway through
+- Keeps default graph clean after all targets are confirmed populated
+
+## Implementation Details
+- Overlap tracking stored in `_migration_overlaps.json`
+- A memory is an overlap if it matches tag criteria for 2+ target graphs
+- Cleanup step verifies presence in all target graphs before deleting from default