diff --git a/db/migrate/20260419023642_create_captain_contact_memories.rb b/db/migrate/20260419023642_create_captain_contact_memories.rb
index 6027601d8..e13aa7f00 100644
--- a/db/migrate/20260419023642_create_captain_contact_memories.rb
+++ b/db/migrate/20260419023642_create_captain_contact_memories.rb
@@ -1,6 +1,12 @@
 class CreateCaptainContactMemories < ActiveRecord::Migration[7.1]
   # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
   def change
+    # NOTE: source_conversation_id, source_unit_id, source_inbox_id, and
+    # superseded_by_id are intentionally plain bigints WITHOUT foreign keys.
+    # Rationale: preserve memory history and audit trail even if the source
+    # conversation/unit/inbox is hard-deleted (LGPD compliance for customer
+    # data retention, see spec §10). Application code must tolerate
+    # dangling references gracefully.
     create_table :captain_contact_memories do |t|
       t.references :account, null: false, foreign_key: true
       t.references :contact, null: false, foreign_key: true
diff --git a/docs/superpowers/specs/2026-04-18-captain-semantic-memory-design.md b/docs/superpowers/specs/2026-04-18-captain-semantic-memory-design.md
index e3712d5ad..fe7ac60aa 100644
--- a/docs/superpowers/specs/2026-04-18-captain-semantic-memory-design.md
+++ b/docs/superpowers/specs/2026-04-18-captain-semantic-memory-design.md
@@ -107,13 +107,13 @@ CREATE TABLE captain_contact_memories (
   confidence              FLOAT NOT NULL,
   scope                   VARCHAR NOT NULL DEFAULT 'global',
   embedding               vector(1536),
-  source_conversation_id  BIGINT REFERENCES conversations(id),
-  source_unit_id          BIGINT REFERENCES captain_units(id),
-  source_inbox_id         BIGINT REFERENCES inboxes(id),
+  source_conversation_id  BIGINT,
+  source_unit_id          BIGINT,
+  source_inbox_id         BIGINT,
   expires_at              TIMESTAMP,
   last_verified_at        TIMESTAMP NOT NULL,
   superseded_at           TIMESTAMP,
-  superseded_by_id        BIGINT REFERENCES captain_contact_memories(id),
+  superseded_by_id        BIGINT,
   deleted_at              TIMESTAMP,
   metadata                JSONB NOT NULL DEFAULT '{}',
   created_at              TIMESTAMP NOT NULL,
@@ -121,6 +121,8 @@ CREATE TABLE captain_contact_memories (
 );
 ```
 
+**Observação — FKs secundárias:** `source_conversation_id`, `source_unit_id`, `source_inbox_id` e `superseded_by_id` são `BIGINT` simples sem `FOREIGN KEY`. Manter a referência mesmo após o registro de origem ser hard-deletado é essencial pra auditoria LGPD (§10) e pra relatórios históricos por unidade (§3 decisão 3). App-layer precisa tratar referências órfãs graciosamente.
+
 ### 6.2 Índices
 
 ```sql