diff --git a/packages/server/src/routes/federation.ts b/packages/server/src/routes/federation.ts
index 36e44495..118741ca 100644
--- a/packages/server/src/routes/federation.ts
+++ b/packages/server/src/routes/federation.ts
@@ -1252,14 +1252,16 @@ function processReactionAddEvent(
     return;
   }
 
-  // Find the local message corresponding to the source message
+  // Find the local message — use the actual message ID from the reaction payload,
+  // not event.messageId which is the outbox dedup key (reactionId)
+  const sourceMessageId = event.reaction.messageId ?? event.messageId;
   const localMsg = db
     .select()
     .from(schema.dmMessages)
     .where(
       and(
         eq(schema.dmMessages.sourceInstance, sourceInstance),
-        eq(schema.dmMessages.sourceMessageId, event.messageId),
+        eq(schema.dmMessages.sourceMessageId, sourceMessageId),
       ),
     )
     .get();
@@ -1337,14 +1339,16 @@ function processReactionRemoveEvent(
     return;
   }
 
-  // Find the local message
+  // Find the local message — use the actual message ID from the reaction payload,
+  // not event.messageId which is the outbox dedup key (composite string)
+  const sourceMessageId = event.reaction.messageId ?? event.messageId;
   const localMsg = db
     .select()
     .from(schema.dmMessages)
     .where(
       and(
         eq(schema.dmMessages.sourceInstance, sourceInstance),
-        eq(schema.dmMessages.sourceMessageId, event.messageId),
+        eq(schema.dmMessages.sourceMessageId, sourceMessageId),
       ),
     )
     .get();
diff --git a/packages/server/src/ws/events.ts b/packages/server/src/ws/events.ts
index 0203d052..ed39ccfb 100644
--- a/packages/server/src/ws/events.ts
+++ b/packages/server/src/ws/events.ts
@@ -1135,6 +1135,7 @@ function handleReactionAdd(event: Record<string, unknown>, userId: string): void
     }));
     queueOutboxEvent(reactionId, dmMsg.dmChannelId, 'reaction_add', JSON.stringify({
       reaction: {
+        messageId,
         userId,
         homeUserId: reactionUser?.homeUserId || userId,
         emoji,
@@ -1212,6 +1213,7 @@ function handleReactionRemove(event: Record<string, unknown>, userId: string): v
       'reaction_remove',
       JSON.stringify({
         reaction: {
+          messageId,
           userId,
           homeUserId: removingUser?.homeUserId || userId,
           emoji,
diff --git a/packages/shared/src/types.ts b/packages/shared/src/types.ts
index 95ca25a5..3a832594 100644
--- a/packages/shared/src/types.ts
+++ b/packages/shared/src/types.ts
@@ -744,6 +744,7 @@ export interface FederationRelayEvent {
 }
 
 export interface FederationRelayReaction {
+  messageId?: string;
   userId: string;
   homeUserId: string;
   emoji: string;