fix(run-store): reject an id-less or wrong-shard waitpoint co-located onto a gen-2 shard

Author: d-cs

internal-packages/run-store/src/runOpsStore.shardMap.test.ts

@@ -672,7 +672,17 @@ describe("RoutingRunStore gen-2 shard refuses a co-located cuid waitpoint", () =
       router.createWaitpoint({ data: { id: "cuid_w1" } } as never, undefined, {
         coLocateWithRunId: "a:run_1",
       })
-    ).toThrow("cuid-shaped waitpoint");
+    ).toThrow('onto gen-2 shard "a"');
+    expect(trace(log)).toEqual([]);
+  });
+
+  it("throws when an id-less waitpoint is co-located onto a gen-2 shard", () => {
+    // Prisma's @default(cuid()) would otherwise mint a cuid on the gen-2 shard AFTER the write,
+    // leaving it unroutable for its own completion (CodeRabbit finding). Reject it up front.
+    const { router, log } = coLocateRouter();
+    expect(() =>
+      router.createWaitpoint({ data: {} } as never, undefined, { coLocateWithRunId: "a:run_1" })
+    ).toThrow('onto gen-2 shard "a"');
     expect(trace(log)).toEqual([]);
   });
 

internal-packages/run-store/src/runOpsStore.ts

@@ -1494,17 +1494,15 @@ export class RoutingRunStore implements RunStore {
   ): RunStore {
     if (ownerId !== undefined) {
       const key = this.#shardKeyOfSafe(ownerId);
-      // A gen-2 shard holds only shard-stamped ids. A cuid waitpoint co-located here would be
-      // unroutable for its own completion, so the blocked run would never resume. The mint layer
-      // must stamp the owner's shard onto the waitpoint id. Fail loud rather than write it.
+      // A gen-2 shard holds only ids stamped for that shard, because a waitpoint completes on the
+      // shard its own id names. Anything else stranded the blocked run: a cuid (routes to the gen-1
+      // pair on completion), an id for a DIFFERENT gen-2 shard, or NO id at all — Prisma's
+      // @default(cuid()) then mints a cuid on the gen-2 shard after the write. The mint layer must
+      // stamp the owner's shard onto the waitpoint id, so fail loud rather than write an orphan.
       const isGen2 = key !== NEW_SHARD && key !== LEGACY_SHARD;
-      if (
-        isGen2 &&
-        typeof waitpointId === "string" &&
-        this.#shardKeyOfSafe(waitpointId) === LEGACY_SHARD
-      ) {
+      if (isGen2 && (waitpointId === undefined || this.#shardKeyOfSafe(waitpointId) !== key)) {
         throw new Error(
-          `RoutingRunStore: refusing to co-locate cuid-shaped waitpoint "${waitpointId}" onto gen-2 shard "${key}"`
+          `RoutingRunStore: refusing to co-locate waitpoint "${waitpointId ?? "<no id>"}" onto gen-2 shard "${key}"; its id must be stamped for that shard`
         );
       }
       return this.#shardStore(key);