@@ -57,6 +57,12 @@ import type {
  */
 export const CF_SUB_AGENT_OUTER_URL_KEY = "_cf_subAgentOuterUrl";
 export const CF_SUB_AGENT_TAGS_KEY = "_cf_subAgentTags";
+/**
+ * Set on a socket closed because its sub-agent was deleted. Its late
+ * message/close events are dropped, so they can't reach a same-name
+ * replacement created after the delete. Storage-frozen — never rename.
+ */
+export const CF_SUB_AGENT_DELETED_KEY = "_cf_subAgentDeleted";
 
 /** Wire-frozen internal header carrying the outer URL on WS upgrades. */
 export const SUB_AGENT_OUTER_URL_HEADER = "x-cf-agents-subagent-url";
@@ -872,6 +878,11 @@ export class DynamicAgentsInternal extends LifecycleCapability {
       const targetPath = this.connectionTargetPath(connection);
       if (!targetPath) continue;
       if (!this.#host._isSameAgentPathPrefix(prefix, targetPath)) continue;
+      this.#host._unsafe_setConnectionFlag(
+        connection,
+        CF_SUB_AGENT_DELETED_KEY,
+        true
+      );
       try {
         connection.close(code, reason);
       } catch {
@@ -1353,6 +1364,11 @@ export class DynamicAgentsInternal extends LifecycleCapability {
     );
     const uri = typeof outerUri === "string" ? outerUri : connection.uri;
     if (!uri) return { status: "no-match" };
+    if (
+      this.#host._unsafe_getConnectionFlag(connection, CF_SUB_AGENT_DELETED_KEY)
+    ) {
+      return { status: "dropped" };
+    }
 
     const ctx = this.#host.ctx as unknown as Partial<FacetCapableCtx>;
     let match = parseSubAgentPath(uri, {
 
@@ -1,5 +1,7 @@
 import { Agent, callable, getCurrentAgent } from "../../index.ts";
 import type {
+  Connection,
+  WSMessage,
   FiberInspection,
   FiberRecoveryContext,
   FiberRecoveryResult,
@@ -8,6 +10,8 @@ import type {
 import { RpcTarget } from "cloudflare:workers";
 import { MessageType } from "../../types.ts";
 
+const STALE_FRAME_PROBE = "stale-frame-probe";
+
 // ── SubAgent: Counter ───────────────────────────────────────────────
 // A SubAgent with its own SQLite counter table.
 
@@ -98,6 +102,10 @@ export class CounterSubAgent extends Agent {
     return rows.length > 0 ? rows[0].value : 0;
   }
 
+  onMessage(_connection: Connection, message: WSMessage) {
+    if (message === STALE_FRAME_PROBE) this.increment(STALE_FRAME_PROBE);
+  }
+
   ping(): string {
     return "pong";
   }
@@ -1427,6 +1435,44 @@ export class TestSubAgentParent extends Agent {
     await this.deleteSubAgent(CounterSubAgent, subAgentName);
   }
 
+  /**
+   * Deletes the child, recreates it under the same name, then forwards a
+   * frame from the socket the delete closed, as a late event would. Returns
+   * how many of those frames the replacement received.
+   */
+  async subAgentForwardStaleFrameToReplacement(
+    subAgentName: string
+  ): Promise<number> {
+    const sockets = (
+      this as unknown as {
+        _webSockets: { getConnections(): Iterable<Connection> };
+      }
+    )._webSockets.getConnections();
+    const connection = [...sockets].find((candidate) => {
+      const outerUrl = this._unsafe_getConnectionFlag(
+        candidate,
+        "_cf_subAgentOuterUrl"
+      );
+      return (
+        typeof outerUrl === "string" &&
+        outerUrl.includes(`/sub/counter-sub-agent/${subAgentName}`)
+      );
+    });
+    if (!connection) throw new Error("no socket for the sub-agent");
+
+    await this.deleteSubAgent(CounterSubAgent, subAgentName);
+    const replacement = await this.subAgent(CounterSubAgent, subAgentName);
+    await (
+      this as unknown as {
+        _cf_forwardSubAgentWebSocketMessage(
+          connection: Connection,
+          message: WSMessage
+        ): Promise<boolean>;
+      }
+    )._cf_forwardSubAgentWebSocketMessage(connection, STALE_FRAME_PROBE);
+    return replacement.get(STALE_FRAME_PROBE);
+  }
+
   async subAgentScheduleDelayed(
     subAgentName: string,
     delaySeconds: number,
 
@@ -2030,6 +2030,20 @@ describe("SubAgent", () => {
       expect(await parent.nestedHasInner(outerName, innerName)).toBe(false);
     });
 
+    it("a late frame from a deleted sub-agent's socket does not reach a same-name replacement", async () => {
+      const parentName = uniqueName();
+      const childName = uniqueName();
+      await connectWS(
+        `/agents/test-sub-agent-parent/${parentName}/sub/counter-sub-agent/${childName}`
+      );
+      const parent = await getAgentByName(env.TestSubAgentParent, parentName);
+      expect(await parent.has("CounterSubAgent", childName)).toBe(true);
+
+      expect(
+        await parent.subAgentForwardStaleFrameToReplacement(childName)
+      ).toBe(0);
+    });
+
     it("listSubAgents enumerates every spawned child", async () => {
       const parentName = uniqueName();
       const a = uniqueName();