diff --git a/services/backend/src/modules/moderation/moderation.repository.ts b/services/backend/src/modules/moderation/moderation.repository.ts
index e813511e..da182b89 100644
--- a/services/backend/src/modules/moderation/moderation.repository.ts
+++ b/services/backend/src/modules/moderation/moderation.repository.ts
@@ -124,7 +124,7 @@ export class ModerationRepository {
         a.score,
         a.evidence,
         a.policy_version,
-        m.username,
+        a.username,
         LEFT(m.content, 300) AS content
       FROM moderation_actions a
       LEFT JOIN messages m ON m.id = a.message_id
@@ -314,7 +314,7 @@ export class ModerationRepository {
       SELECT
         a.id, a.message_id, a.user_id, a.guild_id, a.action_type,
         a.reason, a.status, a.created_at, a.severity, a.confidence, a.score,
-        m.username, LEFT(m.content, 300) AS content
+        a.username, LEFT(m.content, 300) AS content
       FROM moderation_actions a
       LEFT JOIN messages m ON m.id = a.message_id
       WHERE a.created_at >= ${since}
diff --git a/services/discord-gateway/drizzle/migrations/0017_add_username_to_moderation_actions.sql b/services/discord-gateway/drizzle/migrations/0017_add_username_to_moderation_actions.sql
new file mode 100644
index 00000000..4b9b04e1
--- /dev/null
+++ b/services/discord-gateway/drizzle/migrations/0017_add_username_to_moderation_actions.sql
@@ -0,0 +1,9 @@
+ALTER TABLE "moderation_actions" ADD COLUMN "username" text;
+--> statement-breakpoint
+-- Backfill username from messages table for existing actions
+UPDATE "moderation_actions" a
+  SET "username" = m."username"
+  FROM "messages" m
+  WHERE a."message_id" = m."id"
+    AND a."username" IS NULL
+    AND m."username" IS NOT NULL;
diff --git a/services/discord-gateway/drizzle/migrations/meta/_journal.json b/services/discord-gateway/drizzle/migrations/meta/_journal.json
index e56282fd..2af0157f 100644
--- a/services/discord-gateway/drizzle/migrations/meta/_journal.json
+++ b/services/discord-gateway/drizzle/migrations/meta/_journal.json
@@ -120,6 +120,13 @@
       "when": 1787185000000,
       "tag": "0016_drop_user_reputations",
       "breakpoints": true
+    },
+    {
+      "idx": 17,
+      "version": "7",
+      "when": 1787810000000,
+      "tag": "0017_add_username_to_moderation_actions",
+      "breakpoints": true
     }
   ]
 }
\ No newline at end of file
diff --git a/services/discord-gateway/src/modules/ai-moderation/autoDeleteManager.ts b/services/discord-gateway/src/modules/ai-moderation/autoDeleteManager.ts
index 29d9bee7..9a7c0fa3 100644
--- a/services/discord-gateway/src/modules/ai-moderation/autoDeleteManager.ts
+++ b/services/discord-gateway/src/modules/ai-moderation/autoDeleteManager.ts
@@ -197,6 +197,7 @@ async function logAutoDeleteAttempt(
       action_type: "delete_message",
       reason: result.reason,
       ...verdictToActionFields(message),
+      username: message.username,
       executed_by: "auto-delete-manager",
       status: result.deleted
         ? "executed"
@@ -262,6 +263,7 @@ export async function attemptAutoDeleteFlaggedMessage(
             reason:
               "nickname melanggar aturan server (offensive_username); pesan dibiarkan",
             ...verdictToActionFields(message),
+            username: message.username,
             executed_by: "auto-delete-manager",
             status: resetOk ? "executed" : "failed",
             error: resetOk ? null : "nickname_reset_failed",
diff --git a/services/discord-gateway/src/modules/command-handler/moderation.handler.ts b/services/discord-gateway/src/modules/command-handler/moderation.handler.ts
index 42f9f7bb..1a2b23f6 100644
--- a/services/discord-gateway/src/modules/command-handler/moderation.handler.ts
+++ b/services/discord-gateway/src/modules/command-handler/moderation.handler.ts
@@ -103,6 +103,7 @@ export class ModerationHandler {
           | "kick_user"
           | "ban_user",
         reason: payload.reason ?? null,
+        username: null,
         executed_by: payload.executed_by ?? "command-handler",
         status: "executed",
         error: null,
diff --git a/services/discord-gateway/src/shared/database/schema.ts b/services/discord-gateway/src/shared/database/schema.ts
index a544ecef..7d93e756 100644
--- a/services/discord-gateway/src/shared/database/schema.ts
+++ b/services/discord-gateway/src/shared/database/schema.ts
@@ -642,6 +642,7 @@ export const pgModerationActionsTable = pgTable(
     score: pgReal("score"), // 0..1 raw model score
     evidence: pgText("evidence"), // JSON array of short quoted snippets
     policy_version: pgText("policy_version"), // rules.ts policy version string
+    username: pgText("username"), // denormalized from messages table for retention safety
   },
   (table) => ({
     messageIdIdx: pgIndex("idx_moderation_actions_message_id").on(
diff --git a/services/discord-gateway/src/shared/database/schema/messages.ts b/services/discord-gateway/src/shared/database/schema/messages.ts
index 39f22f10..6fe03744 100644
--- a/services/discord-gateway/src/shared/database/schema/messages.ts
+++ b/services/discord-gateway/src/shared/database/schema/messages.ts
@@ -59,6 +59,7 @@ export const pgModerationActionsTable = pgTable(
     score: pgReal("score"), // 0..1 raw model score
     evidence: pgText("evidence"), // JSON array of short quoted snippets
     policy_version: pgText("policy_version"), // rules.ts policy version string
+    username: pgText("username"), // denormalized from messages table for retention safety
   },
   (table) => ({
     messageIdIdx: pgIndex("idx_moderation_actions_message_id").on(
diff --git a/services/discord-gateway/src/shared/moderation-types.ts b/services/discord-gateway/src/shared/moderation-types.ts
index 113603d5..849c52a5 100644
--- a/services/discord-gateway/src/shared/moderation-types.ts
+++ b/services/discord-gateway/src/shared/moderation-types.ts
@@ -208,6 +208,7 @@ export interface ModerationAction {
   guild_id: string;
   action_type: ModerationActionType;
   reason: string | null;
+  username: string | null;
   executed_by: string | null;
   status: "pending" | "executed" | "failed";
   error: string | null;