fix: normalize session keys and outbound mirroring

src/gateway/server-methods/send.test.ts

@@ -6,6 +6,7 @@ import { sendHandlers } from "./send.js";
 const mocks = vi.hoisted(() => ({
   deliverOutboundPayloads: vi.fn(),
   appendAssistantMessageToSessionTranscript: vi.fn(async () => ({ ok: true, sessionFile: "x" })),
+  recordSessionMetaFromInbound: vi.fn(async () => ({ ok: true })),
 }));
 
 vi.mock("../../config/config.js", async () => {
@@ -37,6 +38,7 @@ vi.mock("../../config/sessions.js", async () => {
   return {
     ...actual,
     appendAssistantMessageToSessionTranscript: mocks.appendAssistantMessageToSessionTranscript,
+    recordSessionMetaFromInbound: mocks.recordSessionMetaFromInbound,
   };
 });
 
@@ -134,4 +136,33 @@ describe("gateway send mirroring", () => {
       }),
     );
   });
+
+  it("derives a target session key when none is provided", async () => {
+    mocks.deliverOutboundPayloads.mockResolvedValue([{ messageId: "m3", channel: "slack" }]);
+
+    const respond = vi.fn();
+    await sendHandlers.send({
+      params: {
+        to: "channel:C1",
+        message: "hello",
+        channel: "slack",
+        idempotencyKey: "idem-4",
+      },
+      respond,
+      context: makeContext(),
+      req: { type: "req", id: "1", method: "send" },
+      client: null,
+      isWebchatConnect: () => false,
+    });
+
+    expect(mocks.recordSessionMetaFromInbound).toHaveBeenCalled();
+    expect(mocks.deliverOutboundPayloads).toHaveBeenCalledWith(
+      expect.objectContaining({
+        mirror: expect.objectContaining({
+          sessionKey: "agent:main:slack:channel:resolved",
+          agentId: "main",
+        }),
+      }),
+    );
+  });
 });