fix(server): device hub errors show the hub's reason instead of a connection error

apps/server/src/device/DeviceHubOperations.ts

@@ -49,6 +49,7 @@ const HubActionResult = Schema.Struct({
     Schema.Array(Schema.Struct({ message: Schema.String, error: Schema.optional(Schema.String) })),
   ),
 });
+const HubRejection = Schema.Struct({ error: Schema.String });
 
 // Hub diagnostics can carry a whole stderr dump.
 const boundDiagnostics = (text: string) =>
@@ -98,13 +99,38 @@ export const makeDeviceHubOperations = (options: {
     schema: Schema.Codec<A, I>,
     operation: string,
     timeout: Duration.Input = Duration.seconds(15),
-  ) =>
-    fetchJson(request, schema).pipe(
-      Effect.timeout(timeout),
-      Effect.mapError(
-        (cause) => new DeviceOperationError({ operation, reason: "request_failed", cause }),
+  ) => {
+    const requestFailed = (cause: unknown) =>
+      Effect.fail(new DeviceOperationError({ operation, reason: "request_failed", cause }));
+    return httpClient.execute(request).pipe(
+      Effect.flatMap(HttpClientResponse.filterStatusOk),
+      Effect.flatMap(HttpClientResponse.schemaBodyJson(schema)),
+      Effect.catchReason("HttpClientError", "StatusCodeError", ({ response }, cause) =>
+        // Only the hub's `error` string is surfaced; other bodies can be private hub output.
+        HttpClientResponse.schemaBodyJson(HubRejection)(response).pipe(
+          Effect.map(({ error }) => errorHead(error)),
+          Effect.orElseSucceed(() => ""),
+          Effect.flatMap((detail) =>
+            Effect.fail(
+              new DeviceOperationError({
+                operation,
+                reason: "hub_rejected",
+                ...(detail ? { diagnostics: boundDiagnostics(detail) } : {}),
+                cause,
+              }),
+            ),
+          ),
+        ),
       ),
+      Effect.scoped,
+      Effect.timeout(timeout),
+      Effect.catchTags({
+        HttpClientError: requestFailed,
+        SchemaError: requestFailed,
+        TimeoutError: requestFailed,
+      }),
     );
+  };
 
   const postJson = (path: string, body: Record<string, string>, operation: string) =>
     HttpClientRequest.post(`${origin}${path}`).pipe(

apps/server/src/device/DeviceService.test.ts

@@ -82,6 +82,42 @@ it.effect.each([400, 500])(
     }),
 );
 
+it.effect("reports the hub's error when it rejects attaching a simulator stream", () =>
+  Effect.gen(function* () {
+    const hubError =
+      "Could not release launch state for phone: /tmp/serve-sim/launch-phone.lock is still locked. Retry cleanup after the active command finishes.";
+    const operations = makeDeviceHubOperations({
+      hostId: LOCAL_DEVICE_HOST_ID,
+      origin: "http://device.test",
+      http: HttpClient.make((request) =>
+        Effect.succeed(
+          HttpClientResponse.fromWeb(
+            request,
+            Response.json({ ok: false, error: hubError }, { status: 500 }),
+          ),
+        ),
+      ),
+      run: () => Effect.die("Attaching does not run a command"),
+      platformAvailable: () => Effect.succeed(false),
+    });
+    const error = yield* operations
+      .attach({
+        id: "phone",
+        name: "Phone",
+        version: "iOS 26.3",
+        platform: "ios",
+        booted: true,
+        physical: false,
+      })
+      .pipe(Effect.flip);
+    expect({ _tag: error._tag, reason: error.reason, message: error.message }).toEqual({
+      _tag: "DeviceOperationError",
+      reason: "hub_rejected",
+      message: expect.stringContaining("is still locked"),
+    });
+  }),
+);
+
 const fixture = Effect.fn("fixture")(function* (
   onBoot: Effect.Effect<void> = Effect.void,
   bootError?: string | { error?: string; errors?: Array<{ message: string; error?: string }> },

packages/contracts/src/device.ts

@@ -590,6 +590,7 @@ export class DeviceOperationError extends Schema.TaggedError<DeviceOperationErro
       "hub_rejected",
     ]),
     exitCode: Schema.optional(Schema.Number),
+    diagnostics: Schema.optional(Schema.String.check(Schema.isMaxLength(2_000))),
     cause: Schema.Defect(),
   },
 ) {
@@ -601,7 +602,8 @@ export class DeviceOperationError extends Schema.TaggedError<DeviceOperationErro
       settings_failed: "Could not read or save device settings.",
       hub_rejected: "The device hub could not complete the request.",
     }[this.reason];
-    return `Device ${this.operation} failed: ${explanation}`;
+    const summary = `Device ${this.operation} failed: ${explanation}`;
+    return this.diagnostics ? `${summary}\n\n${this.diagnostics}` : summary;
   }
 }