diff --git a/src/hub/hub.ts b/src/hub/hub.ts
index 8ba68d64..1676309b 100644
--- a/src/hub/hub.ts
+++ b/src/hub/hub.ts
@@ -30,6 +30,7 @@ import { evaluateCommandSafety, requiresApproval } from "../agent/tools/exec-saf
 import { addAllowlistEntry, recordAllowlistUse, matchAllowlist } from "../agent/tools/exec-allowlist.js";
 import type { ExecApprovalCallback, ExecApprovalConfig, ApprovalResult, ExecApprovalRequest } from "../agent/tools/exec-approval-types.js";
 import { readProfileConfig, writeProfileConfig } from "../agent/profile/storage.js";
+import { MessageAggregator, type BlockChunkerConfig, DEFAULT_CHUNKER_CONFIG } from "./message-aggregator.js";
 
 export class Hub {
   private readonly agents = new Map<string, AsyncAgent>();
@@ -37,6 +38,7 @@ export class Hub {
   private readonly agentStreamIds = new Map<string, string>();
   private readonly agentStreamCounters = new Map<string, number>();
   private readonly localApprovalHandlers = new Map<string, (payload: ExecApprovalRequest) => void>();
+  private readonly agentAggregators = new Map<string, MessageAggregator>();
   private readonly rpc: RpcDispatcher;
   private readonly approvalManager: ExecApprovalManager;
   private client: GatewayClient;
@@ -243,6 +245,60 @@ export class Hub {
     return this.approvalManager.resolveApproval(approvalId, decision);
   }
 
+  /**
+   * Enable message aggregation for an agent.
+   * When enabled, streaming text deltas are buffered and emitted as complete block replies
+   * instead of being forwarded as raw events. Useful for third-party messaging integrations.
+   */
+  enableAggregation(agentId: string, config?: Partial<BlockChunkerConfig>): void {
+    const fullConfig = { ...DEFAULT_CHUNKER_CONFIG, ...config };
+    const aggregator = new MessageAggregator(
+      fullConfig,
+      (block) => {
+        const targetDeviceId = this.agentSenders.get(agentId);
+        if (!targetDeviceId) return;
+        this.client.send(targetDeviceId, "block-reply", {
+          agentId,
+          block,
+        });
+      },
+      (event) => {
+        const targetDeviceId = this.agentSenders.get(agentId);
+        if (!targetDeviceId) return;
+
+        const isCompactionEvent =
+          event.type === "compaction_start" || event.type === "compaction_end";
+        if (isCompactionEvent) {
+          this.client.send(targetDeviceId, StreamAction, {
+            streamId: `compaction:${agentId}`,
+            agentId,
+            event,
+          });
+          return;
+        }
+
+        if (event.type === "message_start") {
+          this.beginStream(agentId, event);
+        }
+        const streamId = this.getActiveStreamId(agentId, event);
+        this.client.send(targetDeviceId, StreamAction, {
+          streamId,
+          agentId,
+          event,
+        });
+        if (event.type === "message_end") {
+          this.endStream(agentId);
+        }
+      },
+    );
+    this.agentAggregators.set(agentId, aggregator);
+  }
+
+  /** Disable message aggregation for an agent (reverts to streaming mode). */
+  disableAggregation(agentId: string): void {
+    this.agentAggregators.delete(agentId);
+  }
+
   /** Create new Agent, or rebuild with existing ID */
   createAgent(id?: string, options?: { persist?: boolean; profileId?: string }): AsyncAgent {
     if (id) {
@@ -312,20 +368,13 @@ export class Hub {
           agentId: agent.sessionId,
           content: item.content,
         });
-      } else {
-        // Compaction events: forward with synthetic streamId (no stream tracking)
-        const isCompactionEvent =
-          item.type === "compaction_start" || item.type === "compaction_end";
-        if (isCompactionEvent) {
-          this.client.send(targetDeviceId, StreamAction, {
-            streamId: `compaction:${agent.sessionId}`,
-            agentId: agent.sessionId,
-            event: item,
-          });
-          continue;
-        }
+        continue;
+      }
 
-        // Filter: only forward events useful for frontend rendering
+      // Filter: only forward events useful for frontend rendering
+      const isCompactionEvent =
+        item.type === "compaction_start" || item.type === "compaction_end";
+      if (!isCompactionEvent) {
         const maybeMessage = (item as { message?: { role?: string } }).message;
         const isAssistantMessage = maybeMessage?.role === "assistant";
         const shouldForward =
@@ -333,19 +382,36 @@ export class Hub {
           || item.type === "tool_execution_start"
           || item.type === "tool_execution_end";
         if (!shouldForward) continue;
+      }
 
-        if (item.type === "message_start") {
-          this.beginStream(agent.sessionId, item);
-        }
-        const streamId = this.getActiveStreamId(agent.sessionId, item);
+      // Aggregated mode: buffer text deltas, emit block replies
+      const aggregator = this.agentAggregators.get(agent.sessionId);
+      if (aggregator) {
+        aggregator.handleEvent(item);
+        continue;
+      }
+
+      // Streaming mode: forward events as-is (existing behavior)
+      if (isCompactionEvent) {
         this.client.send(targetDeviceId, StreamAction, {
-          streamId,
+          streamId: `compaction:${agent.sessionId}`,
           agentId: agent.sessionId,
           event: item,
         });
-        if (item.type === "message_end") {
-          this.endStream(agent.sessionId);
-        }
+        continue;
+      }
+
+      if (item.type === "message_start") {
+        this.beginStream(agent.sessionId, item);
+      }
+      const streamId = this.getActiveStreamId(agent.sessionId, item);
+      this.client.send(targetDeviceId, StreamAction, {
+        streamId,
+        agentId: agent.sessionId,
+        event: item,
+      });
+      if (item.type === "message_end") {
+        this.endStream(agent.sessionId);
       }
     }
   }
@@ -503,6 +569,7 @@ export class Hub {
     this.agentStreamIds.delete(id);
     this.agentStreamCounters.delete(id);
     this.localApprovalHandlers.delete(id);
+    this.agentAggregators.delete(id);
     removeAgentRecord(id);
     return true;
   }
@@ -518,6 +585,7 @@ export class Hub {
       this.agentStreamIds.delete(id);
       this.agentStreamCounters.delete(id);
       this.localApprovalHandlers.delete(id);
+      this.agentAggregators.delete(id);
     }
     this.client.disconnect();
     console.log("Hub shut down");