fix(server): PR watches wake again when a push leaves the branch conflicting

apps/server/src/orchestration-v2/PullRequestWatchReactor.ts

@@ -508,9 +508,9 @@ export const make = Effect.gen(function* () {
     }
     readFailures.delete(group.key);
     const [detail, activity] = read.value;
-    const headSha = detail.headSha ?? null;
     for (const target of group.targets) {
       const life = lifeOf(target);
+      const headSha = detail.headSha ?? life.headSha;
       const pushed = life.headSha !== null && headSha !== life.headSha;
       lives.set(lifeKey(target), {
         ...life,

apps/server/src/orchestration-v2/pullRequestWatch.test.ts

@@ -339,6 +339,10 @@ describe("evaluatePullRequestWatch", () => {
     const conflicting = detail({ mergeability: "conflicting" });
     const first = evaluatePullRequestWatch(watch(), conflicting, noRemarks);
     assert.deepEqual(first.changes, [{ kind: "conflicting" }]);
+    const { headSha: _unreadHead, ...headUnread } = conflicting;
+    const unread = evaluatePullRequestWatch(first.next, headUnread, noRemarks);
+    assert.deepEqual(unread.changes, []);
+    assert.deepEqual(evaluatePullRequestWatch(unread.next, conflicting, noRemarks).changes, []);
     const recomputing = evaluatePullRequestWatch(
       first.next,
       detail({ mergeability: "unknown" }),
@@ -352,6 +356,20 @@ describe("evaluatePullRequestWatch", () => {
     assert.deepEqual(evaluatePullRequestWatch(clean.next, conflicting, noRemarks).changes, [
       { kind: "conflicting" },
     ]);
+    const pushed = { headSha: "bbbbbbbbbb" };
+    const recomputed = evaluatePullRequestWatch(
+      first.next,
+      detail({ ...pushed, mergeability: "unknown" }),
+      noRemarks,
+    );
+    assert.deepEqual(
+      evaluatePullRequestWatch(
+        recomputed.next,
+        detail({ ...pushed, mergeability: "conflicting" }),
+        noRemarks,
+      ).changes,
+      [{ kind: "conflicting" }],
+    );
   });
 
   it("does not spend the comment wake limit on check results", () => {

apps/server/src/orchestration-v2/pullRequestWatch.ts

@@ -41,7 +41,8 @@ export function evaluatePullRequestWatch(
   now: number,
 ): PullRequestWatchReport {
   const changes: Array<PullRequestWatchChange> = [];
-  const headSha = detail.headSha ?? null;
+  // Azure DevOps omits the head when its iteration read fails; that is not a push.
+  const headSha = detail.headSha ?? watch.headSha;
   const headMoved = headSha !== watch.headSha;
 
   // Hosts can return no checks on read failure; preserve prior state.
@@ -126,12 +127,14 @@ export function evaluatePullRequestWatch(
     ...atLatest.map((remark) => remark.id),
   ];
 
-  if (detail.mergeability === "conflicting" && !watch.conflicting) {
+  // Like a failed check, a conflict a push did not resolve is news for the new head.
+  const toldConflict = !headMoved && watch.conflicting;
+  if (detail.mergeability === "conflicting" && !toldConflict) {
     changes.push({ kind: "conflicting" });
   }
   // "unknown" is a host still computing after a push; only a clean answer clears a conflict.
   const conflicting =
-    detail.mergeability === "unknown" ? watch.conflicting : detail.mergeability === "conflicting";
+    detail.mergeability === "unknown" ? toldConflict : detail.mergeability === "conflicting";
 
   const commentsOnly = changes.length > 0 && changes.every((change) => change.kind === "remarks");
   const progress = headMoved || (changes.length > 0 && !commentsOnly);