diff --git a/packages/server/src/routes/dm.ts b/packages/server/src/routes/dm.ts
index c13077bd..1801ad00 100644
--- a/packages/server/src/routes/dm.ts
+++ b/packages/server/src/routes/dm.ts
@@ -645,15 +645,25 @@ export async function dmRoutes(app: FastifyInstance): Promise<void> {
       lastMessage: null,
     };
 
-    // Broadcast dm_channel_created to ALL members (including caller)
+    // Broadcast dm_channel_created only to LOCAL members.
+    // Remote members will receive the channel via federation relay → bootstrap
+    // on their home instance, preventing duplicate channels in their sidebar.
+    const domainOriginForBroadcast = isFederationRelayEnabled() ? getOurOrigin() : null;
+    const isLocalMember = (u: { homeInstance?: string | null }) =>
+      !u.homeInstance || !domainOriginForBroadcast ||
+      u.homeInstance === domainOriginForBroadcast ||
+      `https://${u.homeInstance}` === domainOriginForBroadcast;
+
     for (const member of allMembers) {
+      if (!isLocalMember(member)) continue;
       connectionManager.sendToUser(member.id, {
         type: 'dm_channel_created',
         dmChannel: result,
       });
     }
 
-    // Insert & broadcast system messages for each added member
+    // Insert system messages (DB) for all members, but only broadcast to local members.
+    // Remote instances create their own system messages via federation event handlers.
     for (const targetUser of targetUsers) {
       if (!targetUser) continue;
       const baseName = targetUser.username.includes('@') ? targetUser.username.split('@')[0] : targetUser.username;
@@ -683,10 +693,14 @@ export async function dmRoutes(app: FastifyInstance): Promise<void> {
         createdAt: sysMsg.createdAt,
       }).run();
 
-      connectionManager.sendToDmMembers(dmChannelId, {
-        type: 'dm_message_created',
-        message: sysMsg as any,
-      });
+      // Only broadcast to local members — remote instances handle their own
+      for (const member of allMembers) {
+        if (!isLocalMember(member)) continue;
+        connectionManager.sendToUser(member.id, {
+          type: 'dm_message_created',
+          message: sysMsg as any,
+        });
+      }
     }
 
     // Federation: relay member_add for each remote member
@@ -725,8 +739,10 @@ export async function dmRoutes(app: FastifyInstance): Promise<void> {
 
         const targetOrigins = getGroupDmTargetOrigins(dmChannelId);
         let finalTargets = targetOrigins;
-        if (finalTargets && targetUser.homeInstance !== domainOrigin && !finalTargets.includes(targetUser.homeInstance)) {
-          finalTargets = [...finalTargets, targetUser.homeInstance];
+        // Normalize homeInstance to full URL to match peer origin format
+        const targetHomeOrigin = targetUser.homeInstance?.startsWith('http') ? targetUser.homeInstance : `https://${targetUser.homeInstance}`;
+        if (finalTargets && targetHomeOrigin !== domainOrigin && !finalTargets.includes(targetHomeOrigin)) {
+          finalTargets = [...finalTargets, targetHomeOrigin];
         }
 
         appendMutationLog(
@@ -1010,7 +1026,9 @@ export async function dmRoutes(app: FastifyInstance): Promise<void> {
 
       // Include the new member's instance in targets even if not previously in the group
       const targetOrigins = getGroupDmTargetOrigins(id);
-      const newMemberInstance = addedUser?.homeInstance || domainOrigin;
+      // Normalize homeInstance to full URL to match peer origin format
+      const rawNewMemberInstance = addedUser?.homeInstance || domainOrigin;
+      const newMemberInstance = rawNewMemberInstance.startsWith('http') ? rawNewMemberInstance : `https://${rawNewMemberInstance}`;
       let finalTargets = targetOrigins;
       if (finalTargets && newMemberInstance !== domainOrigin && !finalTargets.includes(newMemberInstance)) {
         finalTargets = [...finalTargets, newMemberInstance];
diff --git a/packages/server/src/routes/federation.ts b/packages/server/src/routes/federation.ts
index 78d14605..32117cd9 100644
--- a/packages/server/src/routes/federation.ts
+++ b/packages/server/src/routes/federation.ts
@@ -1705,8 +1705,15 @@ function processMemberAddEvent(
       lastMessage: null,
     };
 
-    // Send dm_channel_created to all local WebSocket-connected members
+    // Send dm_channel_created only to members whose home is THIS instance.
+    // Remote replicas will get the channel from their own home instance's
+    // federation bootstrap — prevents duplicate channels in their sidebar.
+    const bootstrapOrigin = getOurOrigin();
     for (const mu of memberUsers) {
+      const muHome = mu.homeInstance
+        ? (mu.homeInstance.startsWith('http') ? mu.homeInstance : `https://${mu.homeInstance}`)
+        : bootstrapOrigin;  // null homeInstance = native local user
+      if (muHome !== bootstrapOrigin) continue;
       connectionManager.sendToUser(mu.id, {
         type: 'dm_channel_created',
         dmChannel: bootstrapResult,
diff --git a/packages/server/src/utils/federationOutbox.ts b/packages/server/src/utils/federationOutbox.ts
index 1f178a59..3d3f7fbc 100644
--- a/packages/server/src/utils/federationOutbox.ts
+++ b/packages/server/src/utils/federationOutbox.ts
@@ -288,8 +288,10 @@ export function getGroupDmTargetOrigins(dmChannelId: string): string[] | undefin
 
   const origins = new Set<string>();
   for (const p of participants) {
-    if (p.homeInstance !== ourOrigin) {
-      origins.add(p.homeInstance);
+    // Normalize homeInstance to full URL format to match federation_peers.origin
+    const normalized = p.homeInstance.startsWith('http') ? p.homeInstance : `https://${p.homeInstance}`;
+    if (normalized !== ourOrigin) {
+      origins.add(normalized);
     }
   }
 
diff --git a/packages/server/src/utils/federationWorker.ts b/packages/server/src/utils/federationWorker.ts
index 67990aaf..1cb7ff26 100644
--- a/packages/server/src/utils/federationWorker.ts
+++ b/packages/server/src/utils/federationWorker.ts
@@ -171,6 +171,7 @@ async function processOutboxTick(): Promise<void> {
         timestamp: entry.createdAt,
       };
       if (isDm && entry.contextId) evt.dmChannelId = entry.contextId;
+      if (parsed.federatedId) evt.federatedId = parsed.federatedId;
       if (parsed.participants) evt.participants = parsed.participants;
       if (parsed.message) evt.message = parsed.message;
       if (parsed.reactions) evt.reactions = parsed.reactions;