fix(server): PR reads no longer join canceled cache lookups

apps/server/src/pullRequest/PullRequestService.test.ts

@@ -263,6 +263,63 @@ it.effect("does not wait for an in-flight detail read to display a preview", ()
   }),
 );
 
+it.effect("starts a fresh detail lookup while an interrupted read is cleaning up", () =>
+  Effect.gen(function* () {
+    const detailStarted = yield* Deferred.make<void>();
+    const cleanupStarted = yield* Deferred.make<void>();
+    const releaseCleanup = yield* Deferred.make<void>();
+    let calls = 0;
+    const service = yield* makeService({
+      projects: [project({ id: "p1", title: "web", workspaceRoot: "/w", repository: "acme/web" })],
+      providers: [
+        fakeProvider("github", {
+          getChangeRequest: () => {
+            const call = ++calls;
+            return Effect.gen(function* () {
+              if (call === 1) {
+                yield* Deferred.succeed(detailStarted, undefined);
+                return yield* Effect.never;
+              }
+              return hostedChangeRequest("fresh detail");
+            }).pipe(
+              Effect.ensuring(
+                call === 1
+                  ? Deferred.succeed(cleanupStarted, undefined).pipe(
+                      Effect.andThen(Deferred.await(releaseCleanup)),
+                    )
+                  : Effect.void,
+              ),
+            );
+          },
+        }),
+      ],
+    });
+    const reference = { projectId: "p1" as ProjectId, repository: "acme/web", number: 1 };
+
+    const first = yield* service
+      .detail(reference)
+      .pipe(Effect.forkChild({ startImmediately: true }));
+    yield* Deferred.await(detailStarted);
+    const firstInterrupt = yield* Fiber.interrupt(first).pipe(
+      Effect.forkChild({ startImmediately: true }),
+    );
+    yield* Deferred.await(cleanupStarted);
+
+    const second = yield* service
+      .detail(reference)
+      .pipe(Effect.forkChild({ startImmediately: true }));
+    yield* Deferred.succeed(releaseCleanup, undefined);
+    yield* Fiber.join(firstInterrupt);
+
+    assert.strictEqual((yield* Fiber.join(second)).body, "fresh detail");
+    assert.strictEqual(
+      (yield* service.detail({ ...reference, allowStale: false })).body,
+      "fresh detail",
+    );
+    assert.strictEqual(calls, 2);
+  }),
+);
+
 it.effect("keeps previews warm when another project finishes a turn", () =>
   Effect.gen(function* () {
     const reads: string[] = [];

patches/effect@4.0.0-rc.115.patch

@@ -1,3 +1,16 @@
+diff --git a/dist/Cache.js b/dist/Cache.js
+index 315795c3f9f23cc407b270f7def4fef792257a0c..541ae1896a58c88b147d4f364529f1f36e2d98cf 100644
+--- a/dist/Cache.js
++++ b/dist/Cache.js
+@@ -300,6 +300,8 @@ class EntryImpl {
+     return effect.onExit(effect.fiberJoin(this.fiber), () => {
+       this.awaiters--;
+       if (this.awaiters > 0 || this.fiber.pollUnsafe()) return effect.void;
++      // A new reader must not join this lookup while interruption finalizers run.
++      this.expiresAt = 0;
+       return effect.fiberInterrupt(this.fiber);
+     });
+   }
 diff --git a/dist/unstable/ai/McpServer.js b/dist/unstable/ai/McpServer.js
 index e8b9be4..9cffc5c 100644
 --- a/dist/unstable/ai/McpServer.js
@@ -350,3 +363,16 @@ index cbf047f..c7d5cc2 100644
    }
 
    get remoteAddress(): Option.Option<string> {
+diff --git a/src/Cache.ts b/src/Cache.ts
+index de91e02322e21f59c0b49cfebed68a4a536ff9e4..d24cd5cc79ff0c805665ace97d462b2138a4cf48 100644
+--- a/src/Cache.ts
++++ b/src/Cache.ts
+@@ -669,6 +669,8 @@ class EntryImpl<A, E> implements Entry<A, E> {
+     return effect.onExit(effect.fiberJoin(this.fiber), () => {
+       this.awaiters--
+       if (this.awaiters > 0 || this.fiber.pollUnsafe()) return effect.void
++      // A new reader must not join this lookup while interruption finalizers run.
++      this.expiresAt = 0
+       return effect.fiberInterrupt(this.fiber)
+     })
+   }