fix(desktop): key the change list on the channel, not the updater channel

scripts/publish-bk-desktop-dmg.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, it } from "vite-plus/test";
 
 import {
   fingerprintDesignatedRequirement,
+  findPreviousChannelTag,
   summarizeCommitSubjects,
 } from "./publish-bk-desktop-dmg.ts";
 
@@ -79,3 +80,35 @@ describe("summarizeCommitSubjects", () => {
     expect(summarizeCommitSubjects(["Merge branch 'bkmain' into expbkmain", "  ", ""])).toEqual([]);
   });
 });
+
+/**
+ * These tags are the real shapes, because the first version of this lookup keyed
+ * on the brand's `updateChannel` — already `staging-nightly` — and searched for
+ * `-staging-nightly-nightly.`. It matched nothing, so a release shipped with an
+ * empty change list and nothing failed to say so.
+ */
+describe("findPreviousChannelTag", () => {
+  const TAGS = [
+    "v0.0.34-staging-nightly.20260819.1",
+    "v0.0.34-production-nightly.20260818.2",
+    "v0.0.34-staging-nightly.20260818.6",
+    "v0.0.34-production-nightly.20260817.1",
+  ];
+
+  it("finds the newest tag of the requested channel", () => {
+    expect(findPreviousChannelTag(TAGS, "staging")).toBe("v0.0.34-staging-nightly.20260819.1");
+    expect(findPreviousChannelTag(TAGS, "production")).toBe(
+      "v0.0.34-production-nightly.20260818.2",
+    );
+  });
+
+  it("never returns the other channel's build", () => {
+    expect(findPreviousChannelTag(["v0.0.34-production-nightly.20260818.2"], "staging")).toBe(
+      undefined,
+    );
+  });
+
+  it("returns undefined for the very first build of a channel", () => {
+    expect(findPreviousChannelTag([], "production")).toBe(undefined);
+  });
+});

scripts/publish-bk-desktop-dmg.ts

@@ -386,6 +386,23 @@ export function summarizeCommitSubjects(
   return [...unique.slice(0, limit), `…and ${unique.length - limit} more commits.`];
 }
 
+/**
+ * The newest published tag belonging to one channel.
+ *
+ * Keyed on the channel — `staging` / `production` — and not on the brand's
+ * `updateChannel`, which is already `staging-nightly`; matching on that produced
+ * `-staging-nightly-nightly.`, found nothing, and silently shipped a release with
+ * no change list. Same predicate the workflow's already-published check uses.
+ *
+ * `gh release list` returns newest first, so the first hit is the previous build.
+ */
+export function findPreviousChannelTag(
+  publishedTags: ReadonlyArray<string>,
+  variant: BkManagedChannel,
+): string | undefined {
+  return publishedTags.find((candidate) => candidate.includes(`-${variant}-nightly.`));
+}
+
 const GhCompare = Schema.Struct({
   commits: Schema.Array(Schema.Struct({ commit: Schema.Struct({ message: Schema.String }) })),
 });
@@ -799,9 +816,7 @@ const command = Command.make(
       const newest = resolveNewestNightlyVersion(publishedTags, variant);
       // The most recent published build of *this* channel is what the reader is
       // upgrading from, so it is the right base for "what changed".
-      const previousTag = publishedTags.find((candidate) =>
-        candidate.includes(`-${brand.updateChannel}-nightly.`),
-      );
+      const previousTag = findPreviousChannelTag(publishedTags, variant);
       if (newest && compareNightlyVersions(parsed, newest) <= 0) {
         return yield* new ReleaseVersionNotNewerError({
           version,