fix(routing): unify session delivery invariants for duplicate suppression (#33786)

* Routing: unify session delivery invariants

* Routing: address PR review feedback

* Routing: tighten topic and session-scope suppression

* fix(chat): inherit routes for per-account channel-peer sessions

src/utils/delivery-context.test.ts

@@ -24,16 +24,45 @@ describe("delivery context helpers", () => {
     expect(normalizeDeliveryContext({ channel: "  " })).toBeUndefined();
   });
 
-  it("merges primary values over fallback", () => {
+  it("does not inherit route fields from fallback when channels conflict", () => {
     const merged = mergeDeliveryContext(
-      { channel: "whatsapp", to: "channel:abc" },
-      { channel: "slack", to: "channel:def", accountId: "acct" },
+      { channel: "telegram" },
+      { channel: "discord", to: "channel:def", accountId: "acct", threadId: "99" },
     );
 
     expect(merged).toEqual({
-      channel: "whatsapp",
-      to: "channel:abc",
+      channel: "telegram",
+      to: undefined,
+      accountId: undefined,
+    });
+    expect(merged?.threadId).toBeUndefined();
+  });
+
+  it("inherits missing route fields when channels match", () => {
+    const merged = mergeDeliveryContext(
+      { channel: "telegram" },
+      { channel: "telegram", to: "123", accountId: "acct", threadId: "99" },
+    );
+
+    expect(merged).toEqual({
+      channel: "telegram",
+      to: "123",
       accountId: "acct",
+      threadId: "99",
+    });
+  });
+
+  it("uses fallback route fields when fallback has no channel", () => {
+    const merged = mergeDeliveryContext(
+      { channel: "telegram" },
+      { to: "123", accountId: "acct", threadId: "99" },
+    );
+
+    expect(merged).toEqual({
+      channel: "telegram",
+      to: "123",
+      accountId: "acct",
+      threadId: "99",
     });
   });
 
@@ -103,7 +132,7 @@ describe("delivery context helpers", () => {
     });
   });
 
-  it("normalizes delivery fields and mirrors them on session entries", () => {
+  it("normalizes delivery fields, mirrors session fields, and avoids cross-channel carryover", () => {
     const normalized = normalizeSessionDeliveryFields({
       deliveryContext: {
         channel: " Slack ",
@@ -118,12 +147,11 @@ describe("delivery context helpers", () => {
     expect(normalized.deliveryContext).toEqual({
       channel: "whatsapp",
       to: "+1555",
-      accountId: "acct-2",
-      threadId: "444",
+      accountId: undefined,
     });
     expect(normalized.lastChannel).toBe("whatsapp");
     expect(normalized.lastTo).toBe("+1555");
-    expect(normalized.lastAccountId).toBe("acct-2");
-    expect(normalized.lastThreadId).toBe("444");
+    expect(normalized.lastAccountId).toBeUndefined();
+    expect(normalized.lastThreadId).toBeUndefined();
   });
 });

src/utils/delivery-context.ts

@@ -121,11 +121,23 @@ export function mergeDeliveryContext(
   if (!normalizedPrimary && !normalizedFallback) {
     return undefined;
   }
+  const channelsConflict =
+    normalizedPrimary?.channel &&
+    normalizedFallback?.channel &&
+    normalizedPrimary.channel !== normalizedFallback.channel;
   return normalizeDeliveryContext({
     channel: normalizedPrimary?.channel ?? normalizedFallback?.channel,
-    to: normalizedPrimary?.to ?? normalizedFallback?.to,
-    accountId: normalizedPrimary?.accountId ?? normalizedFallback?.accountId,
-    threadId: normalizedPrimary?.threadId ?? normalizedFallback?.threadId,
+    // Keep route fields paired to their channel; avoid crossing fields between
+    // unrelated channels during session context merges.
+    to: channelsConflict
+      ? normalizedPrimary?.to
+      : (normalizedPrimary?.to ?? normalizedFallback?.to),
+    accountId: channelsConflict
+      ? normalizedPrimary?.accountId
+      : (normalizedPrimary?.accountId ?? normalizedFallback?.accountId),
+    threadId: channelsConflict
+      ? normalizedPrimary?.threadId
+      : (normalizedPrimary?.threadId ?? normalizedFallback?.threadId),
   });
 }