fix(outbound): keep channel send durable when transcript mirror fails (#89626)

src/infra/outbound/deliver.test.ts

@@ -3074,9 +3074,6 @@ describe("deliverOutboundPayloads", () => {
   });
 
   it("does not fail the channel send when the post-delivery transcript mirror throws", async () => {
-    // Regression for #89626: a transient session-lock failure on the
-    // best-effort transcript mirror must not invalidate an already-delivered
-    // channel message, otherwise the caller retries and re-sends duplicates.
     const sendMatrix = vi.fn().mockResolvedValue({ messageId: "m1", roomId: "!room:example" });
     mocks.appendAssistantMessageToSessionTranscript.mockClear();
     mocks.appendAssistantMessageToSessionTranscript.mockRejectedValueOnce(
@@ -3096,7 +3093,6 @@ describe("deliverOutboundPayloads", () => {
       },
     });
 
-    // Channel delivered exactly once; the mirror failure was swallowed.
     expect(sendMatrix).toHaveBeenCalledTimes(1);
     expect(results).toHaveLength(1);
     const warnCall = requireMockCall(logMocks.warn, "warn");

src/infra/outbound/deliver.ts

@@ -1967,15 +1967,9 @@ async function deliverOutboundPayloadsCore(
       mediaUrls: deliveredMirror.mediaUrls,
     });
     if (mirrorText) {
-      // The transcript mirror is best-effort bookkeeping that runs *after* the
-      // channel payloads were already delivered (guarded by results.length > 0
-      // above). A failure here — e.g. transient session-lock contention
-      // ("session file changed while embedded prompt lock was released") — must
-      // not propagate, or the caller would treat the whole send as failed and
-      // re-deliver the already-sent message (duplicate announcements). Match the
-      // cron delivery path (mirrorDirectDeliveryIntoTranscript) and downgrade
-      // mirror failures to a warning. The append carries an idempotency key, so
-      // any later reconciliation stays deduplicated.
+      // Transcript mirroring is best-effort bookkeeping after platform send.
+      // Keep mirror failures non-fatal so callers do not retry an already-sent
+      // channel payload and create duplicate delivery.
       try {
         const { appendAssistantMessageToSessionTranscript } = await loadTranscriptRuntime();
         const mirrorResult = await appendAssistantMessageToSessionTranscript({