diff --git a/.changeset/calm-agent-manager-streams.md b/.changeset/calm-agent-manager-streams.md
new file mode 100644
index 00000000000..2d16ef00e4d
--- /dev/null
+++ b/.changeset/calm-agent-manager-streams.md
@@ -0,0 +1,5 @@
+---
+"kilo-code": patch
+---
+
+Reduce duplicate event processing across VS Code when multiple sessions run concurrently.
diff --git a/packages/kilo-vscode/src/services/cli-backend/connection-service.ts b/packages/kilo-vscode/src/services/cli-backend/connection-service.ts
index d202eeedba9..1b0e8679d38 100644
--- a/packages/kilo-vscode/src/services/cli-backend/connection-service.ts
+++ b/packages/kilo-vscode/src/services/cli-backend/connection-service.ts
@@ -3,7 +3,7 @@ import { ServerManager } from "./server-manager"
 import { createKiloClient, type KiloClient } from "@kilocode/sdk/v2/client"
 import { SdkSSEAdapter, type SSEPayload } from "./sdk-sse-adapter"
 import type { ServerConfig } from "./types"
-import { resolveEventSessionId as resolveEventSessionIdPure } from "./connection-utils"
+import { createDuplicateEventFilter, resolveEventSessionId as resolveEventSessionIdPure } from "./connection-utils"
 import { SandboxPreference } from "../sandbox-preference"
 
 export type ConnectionState = "connecting" | "connected" | "disconnected" | "error"
@@ -96,6 +96,7 @@ export class KiloConnectionService {
   private remoteService: import("../RemoteStatusService").RemoteStatusService | null = null
 
   private readonly eventListeners: Set<SSEEventListener> = new Set()
+  private readonly duplicateEvent = createDuplicateEventFilter()
   private readonly stateListeners: Set<StateListener> = new Set()
   private readonly notificationDismissListeners: Set<NotificationDismissListener> = new Set()
   private readonly languageChangeListeners: Set<LanguageChangeListener> = new Set()
@@ -837,6 +838,8 @@ export class KiloConnectionService {
     // Wire SSE events → broadcast to all registered listeners
     sse.onEvent((event, directory) => {
       if (this.sseClient !== sse) return
+      // EventV2Bridge also emits these durable compatibility envelopes after their normal live events.
+      if (this.duplicateEvent(event)) return
       this.handlePermissionEvent(event, directory)
       this.handleQuestionEvent(event, directory)
       for (const listener of this.eventListeners) {
diff --git a/packages/kilo-vscode/src/services/cli-backend/connection-utils.ts b/packages/kilo-vscode/src/services/cli-backend/connection-utils.ts
index f41c9a8b16f..271eec41148 100644
--- a/packages/kilo-vscode/src/services/cli-backend/connection-utils.ts
+++ b/packages/kilo-vscode/src/services/cli-backend/connection-utils.ts
@@ -4,6 +4,33 @@ export type { SSEPayload } from "./sdk-sse-adapter"
 type SyncPayload = Extract<SSEPayload, { type: "sync" }>
 type TransientPayload = Exclude<SSEPayload, SyncPayload>
 
+const duplicateSyncEvents = new Set([
+  "message.updated.1",
+  "message.removed.1",
+  "message.part.updated.1",
+  "message.part.removed.1",
+  "session.created.1",
+  "session.deleted.1",
+])
+
+const duplicateLiveEvents = new Set([...duplicateSyncEvents].map((name) => name.slice(0, -2)))
+const DUPLICATE_EVENT_LIMIT = 1024
+
+export function createDuplicateEventFilter() {
+  const seen = new Set<string>()
+  return (event: SSEPayload): boolean => {
+    if (event.type === "sync") {
+      return duplicateSyncEvents.has(event.name) && seen.delete(event.id)
+    }
+
+    if (duplicateLiveEvents.has(event.type)) {
+      seen.add(event.id)
+      if (seen.size > DUPLICATE_EVENT_LIMIT) seen.delete(seen.values().next().value!)
+    }
+    return false
+  }
+}
+
 /**
  * Pure session ID resolution for SSE events.
  * The lookupMessageSessionId callback remains part of the public resolver contract for
diff --git a/packages/kilo-vscode/tests/unit/connection-utils.test.ts b/packages/kilo-vscode/tests/unit/connection-utils.test.ts
index bd9ab804353..c1865616e7d 100644
--- a/packages/kilo-vscode/tests/unit/connection-utils.test.ts
+++ b/packages/kilo-vscode/tests/unit/connection-utils.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, it } from "bun:test"
-import { resolveEventSessionId } from "../../src/services/cli-backend/connection-utils"
+import { createDuplicateEventFilter, resolveEventSessionId } from "../../src/services/cli-backend/connection-utils"
 import type { SSEPayload as Payload } from "../../src/services/cli-backend/sdk-sse-adapter"
 
 const noLookup = (_: string) => undefined
@@ -172,3 +172,65 @@ describe("resolveEventSessionId", () => {
     expect(resolveEventSessionId(event, noLookup)).toBeUndefined()
   })
 })
+
+describe("isDuplicateSyncEvent", () => {
+  it("drops a compatibility envelope only after its live event", () => {
+    const filter = createDuplicateEventFilter()
+    const live = {
+      id: "e13",
+      type: "message.part.updated",
+      properties: { sessionID: "s6", part, delta: "x" },
+    } satisfies Payload
+    expect(filter(live)).toBe(false)
+    expect(
+      filter(
+        sync({
+          type: "sync",
+          name: "message.part.updated.1",
+          id: "e13",
+          seq: 5,
+          aggregateID: "s6",
+          data: { sessionID: "s6", part, time: 0 },
+        }),
+      ),
+    ).toBe(true)
+  })
+
+  it("keeps replay-only compatibility envelopes", () => {
+    const filter = createDuplicateEventFilter()
+    expect(
+      filter(
+        sync({
+          type: "sync",
+          name: "session.next.model.switched.1",
+          id: "e14",
+          seq: 6,
+          aggregateID: "s6",
+          data: { sessionID: "s6", messageID: "m1", model: { id: "test", providerID: "kilo" } },
+        }),
+      ),
+    ).toBe(false)
+  })
+
+  it("keeps session updates because the provider consumes their sync metadata", () => {
+    const filter = createDuplicateEventFilter()
+    const live = {
+      id: "e15",
+      type: "session.updated",
+      properties: { sessionID: "s6", info: { id: "s6", time: { created: 0, updated: 1 } } },
+    } as Payload
+    expect(filter(live)).toBe(false)
+    expect(
+      filter(
+        sync({
+          type: "sync",
+          name: "session.updated.1",
+          id: "e15",
+          seq: 7,
+          aggregateID: "s6",
+          data: { sessionID: "s6", info: { id: "s6", time: { created: 0, updated: 1 } } },
+        }),
+      ),
+    ).toBe(false)
+  })
+})