fix: use core-appropriate error messages in runHandler instead of extension wording

runHandler is used exclusively for core agent/client RPC methods (e.g.
session/prompt, fs/read_text_file), not extension methods. It was
incorrectly using fromHandlerError which always emits 'ACP extension
request handler failed' and tags operation as 'handle-extension-request'.

Now runHandler produces 'ACP request handler failed for method ...' with
operation 'handle-request', making core protocol failures distinguishable
from extension failures for debugging and client-side error handling.

Author: cursoragent

packages/effect-acp/src/_internal/shared.ts

@@ -35,9 +35,17 @@ export const runHandler = Effect.fnUntraced(function* <A, B>(
     return yield* Effect.fail(AcpError.AcpRequestError.methodNotFound(method).toProtocolError());
   }
   return yield* handler(payload).pipe(
-    Effect.mapError((error) =>
-      AcpError.AcpRequestError.fromHandlerError(error, method).toProtocolError(),
-    ),
+    Effect.mapError((error) => {
+      const requestError =
+        error._tag === "AcpRequestError"
+          ? error
+          : AcpError.AcpRequestError.internalError(
+              `ACP request handler failed for method '${method}'`,
+              undefined,
+              { method, operation: "handle-request", cause: error },
+            );
+      return requestError.toProtocolError();
+    }),
   );
 });
 

packages/effect-acp/src/errors.test.ts

@@ -96,7 +96,7 @@ describe("effect-acp errors", () => {
 
       expect(error).toMatchObject({
         code: -32603,
-        message: "ACP extension request handler failed for method 'fs/read_text_file'",
+        message: "ACP request handler failed for method 'fs/read_text_file'",
       });
       expect(error.message).not.toContain(cause.message);
     });

packages/effect-acp/src/errors.ts

@@ -6,6 +6,7 @@ import * as AcpSchema from "./_generated/schema.gen.ts";
 export const AcpRequestOperation = Schema.Literals([
   "decode-extension-request-payload",
   "handle-extension-request",
+  "handle-request",
 ]);
 export type AcpRequestOperation = typeof AcpRequestOperation.Type;