fix(backfill): compare PR updatedAt by instant so the metadata gate skips

packages/das/src/entities/PullRequest.entity.ts

@@ -35,8 +35,9 @@ export class PullRequest {
   @Column({ name: "merged_at", type: "timestamptz", nullable: true })
   mergedAt: string;
 
+  // ISO string on write, Date on read (TypeORM hydrates timestamptz).
   @Column({ name: "updated_at", type: "timestamptz", nullable: true })
-  updatedAt: string | null;
+  updatedAt: Date | string | null;
 
   @Column({ name: "last_edited_at", type: "timestamptz", nullable: true })
   lastEditedAt: string | null;

packages/das/src/webhook/incremental-backfill.spec.ts

@@ -69,4 +69,41 @@ describe("needsMetadataRefresh", () => {
   it("re-fetches when GitHub returned a null updatedAt", () => {
     expect(needsMetadataRefresh(stored(), null)).toBe(true);
   });
+
+  // Stored side is a hydrated Date, incoming is GitHub's ISO string.
+  it("skips when a hydrated Date equals GitHub's ISO string (same instant)", () => {
+    expect(
+      needsMetadataRefresh(
+        stored({ updatedAt: new Date("2026-06-01T00:00:00Z") }),
+        "2026-06-01T00:00:00Z",
+      ),
+    ).toBe(false);
+  });
+
+  it("skips across timezone-equivalent representations of the same instant", () => {
+    expect(
+      needsMetadataRefresh(
+        stored({ updatedAt: new Date("2026-06-01T00:00:00Z") }),
+        "2026-05-31T19:00:00-05:00",
+      ),
+    ).toBe(false);
+  });
+
+  it("re-fetches when a hydrated Date is a different instant", () => {
+    expect(
+      needsMetadataRefresh(
+        stored({ updatedAt: new Date("2026-06-01T00:00:00Z") }),
+        "2026-06-02T00:00:00Z",
+      ),
+    ).toBe(true);
+  });
+
+  it("re-fetches (fails safe) on an unparseable stored value", () => {
+    expect(
+      needsMetadataRefresh(
+        stored({ updatedAt: "not-a-date" }),
+        "2026-06-01T00:00:00Z",
+      ),
+    ).toBe(true);
+  });
 });

packages/das/src/webhook/incremental-backfill.ts

@@ -5,7 +5,8 @@
 export interface StoredPrState {
   headSha: string | null;
   baseSha: string | null;
-  updatedAt: string | null;
+  // Date from TypeORM (timestamptz), string in tests.
+  updatedAt: Date | string | null;
   scoringDataStored: boolean;
 }
 
@@ -23,16 +24,20 @@ export function needsContentRefresh(
   );
 }
 
-// updatedAt bumps on edits, state changes, merges, closes and link changes, so
-// skip the PR_METADATA fetch only when it matches the stored value.
+// Normalise a Date or ISO string to an epoch-ms instant; null if unparseable.
+function toEpochMs(value: Date | string | null): number | null {
+  if (value == null) return null;
+  const ms =
+    value instanceof Date ? value.getTime() : new Date(value).getTime();
+  return Number.isNaN(ms) ? null : ms;
+}
+
+// Skip the PR_METADATA fetch only when GitHub's updatedAt instant is unchanged.
 export function needsMetadataRefresh(
   stored: StoredPrState | null | undefined,
   updatedAt: string | null,
 ): boolean {
-  return !(
-    stored != null &&
-    stored.updatedAt != null &&
-    updatedAt != null &&
-    stored.updatedAt === updatedAt
-  );
+  const storedMs = stored ? toEpochMs(stored.updatedAt) : null;
+  const incomingMs = toEpochMs(updatedAt);
+  return !(storedMs != null && incomingMs != null && storedMs === incomingMs);
 }