diff --git a/src/gateway/server-methods/agent.test.ts b/src/gateway/server-methods/agent.test.ts
index 8d77e04db14..be7caca9aee 100644
--- a/src/gateway/server-methods/agent.test.ts
+++ b/src/gateway/server-methods/agent.test.ts
@@ -522,6 +522,7 @@ describe("gateway agent handler", () => {
   it("rejects deliver=true when backend callers use the inter_session sentinel", async () => {
     primeMainAgentRun();
     mocks.agentCommand.mockClear();
+    const context = makeContext();
     const selectionSpy = vi.spyOn(channelSelection, "resolveMessageChannelSelection");
     selectionSpy.mockResolvedValue({
       channel: "telegram",
@@ -540,6 +541,7 @@ describe("gateway agent handler", () => {
       },
       {
         reqId: "inter-session-backend-deliver-1",
+        context,
         client: {
           connect: {
             role: "operator",
@@ -566,6 +568,11 @@ describe("gateway agent handler", () => {
       code: "INVALID_REQUEST",
       message: expect.stringContaining("inter_session"),
     });
+    expect(context.addChatRun).not.toHaveBeenCalled();
+    expect(mocks.registerAgentRunContext).not.toHaveBeenCalledWith(
+      "test-inter-session-backend-deliver",
+      expect.anything(),
+    );
     expect(mocks.agentCommand).not.toHaveBeenCalled();
   });
 
diff --git a/src/gateway/server-methods/agent.ts b/src/gateway/server-methods/agent.ts
index 497f15e8d39..ce7b7844356 100644
--- a/src/gateway/server-methods/agent.ts
+++ b/src/gateway/server-methods/agent.ts
@@ -313,6 +313,23 @@ export const agentHandlers: GatewayRequestHandlers = {
         return;
       }
     }
+
+    const wantsDelivery = request.deliver === true;
+    const requestedInterSessionForDelivery = [request.channel, request.replyChannel].some((value) =>
+      isInterSessionChannel(normalizeMessageChannel(value)),
+    );
+    if (wantsDelivery && requestedInterSessionForDelivery) {
+      respond(
+        false,
+        undefined,
+        errorShape(
+          ErrorCodes.INVALID_REQUEST,
+          "delivery channel cannot use the inter_session sentinel",
+        ),
+      );
+      return;
+    }
+
     let resolvedSessionId = request.sessionId?.trim() || undefined;
     let sessionEntry: SessionEntry | undefined;
     let bestEffortDeliver = requestedBestEffortDeliver ?? false;
@@ -472,21 +489,6 @@ export const agentHandlers: GatewayRequestHandlers = {
       }
     }
 
-    const wantsDelivery = request.deliver === true;
-    const requestedInterSessionForDelivery = [request.channel, request.replyChannel].some((value) =>
-      isInterSessionChannel(normalizeMessageChannel(value)),
-    );
-    if (wantsDelivery && requestedInterSessionForDelivery) {
-      respond(
-        false,
-        undefined,
-        errorShape(
-          ErrorCodes.INVALID_REQUEST,
-          "delivery channel cannot use the inter_session sentinel",
-        ),
-      );
-      return;
-    }
     const explicitTo =
       typeof request.replyTo === "string" && request.replyTo.trim()
         ? request.replyTo.trim()