fix(web): stock hub request failures include the hub's error message (CL-8422)

apps/web/src/needs-converge.test.ts

@@ -6,6 +6,7 @@ import {
   createFetchStockHub,
   forkSubThread,
   StockHubCapabilityError,
+  StockHubRequestError,
   type HubSnapshot,
   type MailMessage,
   type StockHub,
@@ -701,6 +702,36 @@ describe("stock-only fetch hub", () => {
     }) as typeof fetch;
   }
 
+  function stubFetchRejecting(body: unknown, status: number): typeof fetch {
+    return (async () => new Response(JSON.stringify(body), { status })) as unknown as typeof fetch;
+  }
+
+  test("a failed request carries the hub's error code and message", async () => {
+    const hub = createFetchStockHub(
+      stubFetchRejecting({ error: { code: "invalid_workflow", message: "entry threw" } }, 409),
+    );
+
+    const error = await hub
+      .deployWorkflow("tnt_1", {
+        source: {
+          kind: "asset",
+          assetId: "ast_1",
+          package: { format: "source", commitSha: "abc" },
+        },
+        entry: "./workflow.js",
+        sourceOfferingIds: ["off_1"],
+        defaultSourceOfferingId: "off_1",
+      })
+      .then(
+        () => null,
+        (cause: unknown) => cause,
+      );
+    expect(error).toBeInstanceOf(StockHubRequestError);
+    expect((error as StockHubRequestError).message).toBe(
+      "Stock request deployWorkflow failed with HTTP 409. invalid_workflow: entry threw",
+    );
+  });
+
   test("mailbox search and thread reads stay typed upstream gaps", async () => {
     const hub = createFetchStockHub(stubFetch([], {}));
 

apps/web/src/needs-converge.ts

@@ -528,12 +528,21 @@ async function resolveRoleId(
   return found.id;
 }
 
+const HubErrorEnvelope = type({
+  error: { code: "string", "message?": "string", "userMessage?": "string" },
+});
+
 async function readJson(response: Response, operation: string): Promise<unknown> {
   if (!response.ok) {
+    const envelope = HubErrorEnvelope(await response.json().catch(() => undefined));
+    const reason =
+      envelope instanceof type.errors
+        ? ""
+        : ` ${envelope.error.code}: ${envelope.error.userMessage ?? envelope.error.message ?? ""}`;
     throw new StockHubRequestError(
       operation,
       response.status,
-      `Stock request ${operation} failed with HTTP ${response.status}.`,
+      `Stock request ${operation} failed with HTTP ${response.status}.${reason}`,
     );
   }
   return (await response.json()) as unknown;