fix(claude-tty): report an adapter error in its own words instead of "Internal error"

apps/claude-tty-acp/src/main.ts

@@ -4,6 +4,7 @@ import { ClaudeTtyAgent } from "./agent.ts";
 import { useAnswersDirectory } from "./card-answers.ts";
 import { readIdleTimeout } from "./idle-timeout.ts";
 import { enableLogFile, writeLog } from "./log.ts";
+import { withRequestErrors } from "./request-errors.ts";
 import { cleanupAbandonedRuntimeDirectories } from "./runtime-directories.ts";
 import { useSettingsFile } from "./settings-document.ts";
 
@@ -34,7 +35,7 @@ export async function runAcpServer(settingsFile: string | null, answersDirectory
         void shutdown("workspace_removed").finally(() => process.exit(0));
       },
     });
-    return agent;
+    return withRequestErrors(agent);
   }, ndJsonStream(output, input));
 
   const handleSignal = (signal: NodeJS.Signals): void => {

apps/claude-tty-acp/src/request-errors.test.ts

@@ -0,0 +1,50 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import {
+  AgentSideConnection,
+  ClientSideConnection,
+  ndJsonStream,
+  PROTOCOL_VERSION,
+  RequestError,
+  type Client,
+} from "@agentclientprotocol/sdk";
+import { ClaudeTtyAgent } from "./agent.ts";
+import { withRequestErrors } from "./request-errors.ts";
+
+/** Connects a client to the agent over the SDK's own JSON-RPC, so the test sees what Paseo sees. */
+function connect(): { client: ClientSideConnection; agent: () => ClaudeTtyAgent | null } {
+  const toAgent = new TransformStream<Uint8Array, Uint8Array>();
+  const toClient = new TransformStream<Uint8Array, Uint8Array>();
+  let agent: ClaudeTtyAgent | null = null;
+  new AgentSideConnection((connection) => {
+    agent = new ClaudeTtyAgent(connection);
+    return withRequestErrors(agent);
+  }, ndJsonStream(toClient.writable, toAgent.readable));
+  const client = new ClientSideConnection(
+    () => ({ requestPermission: async () => ({ outcome: { outcome: "cancelled" } }), sessionUpdate: async () => undefined }) as Client,
+    ndJsonStream(toAgent.writable, toClient.readable),
+  );
+  return { client, agent: () => agent };
+}
+
+test("answers a failed request with the adapter's own sentence", async () => {
+  const { client, agent } = connect();
+  await client.initialize({ protocolVersion: PROTOCOL_VERSION });
+
+  await assert.rejects(client.prompt({ sessionId: "missing", prompt: [{ type: "text", text: "hi" }] }), {
+    code: -32603,
+    message: "Session missing not found",
+  });
+  await agent()?.close();
+});
+
+test("passes a RequestError through as it was thrown", async () => {
+  const thrown = RequestError.invalidParams(undefined, "no such mode");
+  const wrapped = withRequestErrors({
+    initialize: async () => {
+      throw thrown;
+    },
+  } as unknown as ClaudeTtyAgent);
+
+  await assert.rejects(wrapped.initialize({ protocolVersion: PROTOCOL_VERSION }), (error) => error === thrown);
+});

apps/claude-tty-acp/src/request-errors.ts

@@ -0,0 +1,28 @@
+import { type Agent, RequestError } from "@agentclientprotocol/sdk";
+
+/**
+ * Hands the SDK an agent whose failures carry their own text as the JSON-RPC message.
+ * The SDK answers any error that is not a `RequestError` with the message "Internal error" and
+ * the real text in `data.details`, which a client is free to drop, and Paseo has. The code stays
+ * -32603: Paseo branches on -32602 alone, so another code would change nothing but the meaning.
+ */
+export function withRequestErrors<T extends Agent>(agent: T): T {
+  return new Proxy(agent, {
+    get(target, property, receiver) {
+      const value: unknown = Reflect.get(target, property, receiver);
+      if (typeof value !== "function") return value;
+      return async (...args: unknown[]) => {
+        try {
+          return await value.apply(target, args);
+        } catch (error) {
+          throw toRequestError(error);
+        }
+      };
+    },
+  });
+}
+
+export function toRequestError(error: unknown): RequestError {
+  if (error instanceof RequestError) return error;
+  return new RequestError(-32603, error instanceof Error ? error.message : String(error));
+}