From 42284cc2da69ad98dbbf867533199bc06cf87eff Mon Sep 17 00:00:00 2001
From: Rai Butera <rai@rbutera.com>
Date: Thu, 12 Mar 2026 18:20:34 +0000
Subject: [PATCH] fix: remove session-key channel hint fallback for
 inter-session turns

---
 src/auto-reply/reply/session-delivery.test.ts | 7 +++++--
 src/auto-reply/reply/session-delivery.ts      | 4 ----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/src/auto-reply/reply/session-delivery.test.ts b/src/auto-reply/reply/session-delivery.test.ts
index 6b4caaa555e..68e34ad9f96 100644
--- a/src/auto-reply/reply/session-delivery.test.ts
+++ b/src/auto-reply/reply/session-delivery.test.ts
@@ -28,14 +28,17 @@ describe("INTER_SESSION_CHANNEL sentinel routing", () => {
     expect(result).toBe("discord");
   });
 
-  it("falls back to session-key channel hint when no persisted channel is set", () => {
+  it("returns undefined when persisted channel is absent and only session-key hint exists (no channel synthesis)", () => {
+    // Inter-session turns must not synthesise a channel from the session key alone.
+    // Without a persisted external channel, returning a channel-only route would leave
+    // lastTo undefined and risk misdelivery via the channel defaultTo fallback.
     expect(
       resolveLastChannelRaw({
         originatingChannelRaw: INTER_SESSION_CHANNEL,
         persistedLastChannel: undefined,
         sessionKey: "agent:navi:discord:direct:channel:123",
       }),
-    ).toBe("discord");
+    ).toBeUndefined();
   });
 
   it("returns undefined when no external route can be determined", () => {
diff --git a/src/auto-reply/reply/session-delivery.ts b/src/auto-reply/reply/session-delivery.ts
index af00dc2d7dd..6dc8a53e57c 100644
--- a/src/auto-reply/reply/session-delivery.ts
+++ b/src/auto-reply/reply/session-delivery.ts
@@ -99,10 +99,6 @@ export function resolveLastChannelRaw(params: {
     if (isExternalRoutingChannel(persistedChannel)) {
       return persistedChannel;
     }
-    const sessionKeyChannelHint = resolveSessionKeyChannelHint(params.sessionKey);
-    if (isExternalRoutingChannel(sessionKeyChannelHint)) {
-      return sessionKeyChannelHint;
-    }
     return undefined;
   }