Address remote protocol error diagnostics

Co-authored-by: Codex <codex@openai.com>

Author: StiensWout

packages/shared/src/remote.test.ts

@@ -83,7 +83,8 @@ describe("remote", () => {
     }
 
     expect(pairingUrlError).toBeInstanceOf(RemotePairingUrlInvalidError);
-    expect((pairingUrlError as RemotePairingUrlInvalidError).cause).toBeInstanceOf(Error);
+    expect(pairingUrlError).toMatchObject({ protocol: "ftp:" });
+    expect((pairingUrlError as RemotePairingUrlInvalidError).cause).toBeUndefined();
   });
 
   it("rejects unsupported hosted pairing backend protocols", () => {
@@ -98,8 +99,8 @@ describe("remote", () => {
     }
 
     expect(hostError).toBeInstanceOf(RemoteBackendUrlInvalidError);
-    expect(hostError).toMatchObject({ source: "hosted-pairing-host" });
-    expect((hostError as RemoteBackendUrlInvalidError).cause).toBeInstanceOf(Error);
+    expect(hostError).toMatchObject({ source: "hosted-pairing-host", protocol: "ftp:" });
+    expect((hostError as RemoteBackendUrlInvalidError).cause).toBeUndefined();
   });
 
   it("rejects unsupported direct host protocols", () => {
@@ -114,8 +115,8 @@ describe("remote", () => {
     }
 
     expect(hostError).toBeInstanceOf(RemoteBackendUrlInvalidError);
-    expect(hostError).toMatchObject({ source: "direct-host" });
-    expect((hostError as RemoteBackendUrlInvalidError).cause).toBeInstanceOf(Error);
+    expect(hostError).toMatchObject({ source: "direct-host", protocol: "ftp:" });
+    expect((hostError as RemoteBackendUrlInvalidError).cause).toBeUndefined();
   });
 
   it("uses distinct structural errors for missing pairing inputs", () => {

packages/shared/src/remote.ts

@@ -19,7 +19,10 @@ export class RemoteBackendUrlMissingError extends Schema.TaggedErrorClass<Remote
 
 export class RemotePairingUrlInvalidError extends Schema.TaggedErrorClass<RemotePairingUrlInvalidError>()(
   "RemotePairingUrlInvalidError",
-  { cause: Schema.Defect() },
+  {
+    cause: Schema.optional(Schema.Defect()),
+    protocol: Schema.optional(Schema.String),
+  },
 ) {
   override get message(): string {
     return "Pairing URL is invalid.";
@@ -30,7 +33,8 @@ export class RemoteBackendUrlInvalidError extends Schema.TaggedErrorClass<Remote
   "RemoteBackendUrlInvalidError",
   {
     source: Schema.Literals(["direct-host", "hosted-pairing-host"]),
-    cause: Schema.Defect(),
+    cause: Schema.optional(Schema.Defect()),
+    protocol: Schema.optional(Schema.String),
   },
 ) {
   override get message(): string {
@@ -65,9 +69,6 @@ export const RemotePairingTargetError = Schema.Union([
 ]);
 export type RemotePairingTargetError = typeof RemotePairingTargetError.Type;
 
-const createUnsupportedRemoteBackendProtocolError = (url: URL): TypeError =>
-  new TypeError(`Unsupported remote backend URL protocol: ${url.protocol}`);
-
 const hasSupportedRemoteBackendProtocol = (url: URL): boolean =>
   SUPPORTED_REMOTE_BACKEND_PROTOCOLS.has(url.protocol);
 
@@ -93,7 +94,7 @@ const normalizeRemoteBaseUrl = (
   if (!hasSupportedRemoteBackendProtocol(url)) {
     throw new RemoteBackendUrlInvalidError({
       source,
-      cause: createUnsupportedRemoteBackendProtocolError(url),
+      protocol: url.protocol,
     });
   }
   url.pathname = "/";
@@ -199,7 +200,7 @@ export const resolveRemotePairingTarget = (input: {
     }
     if (!hasSupportedRemoteBackendProtocol(url)) {
       throw new RemotePairingUrlInvalidError({
-        cause: createUnsupportedRemoteBackendProtocolError(url),
+        protocol: url.protocol,
       });
     }
     const hostedPairingRequest = readHostedPairingRequest(url);