diff --git a/src/app/error.tsx b/src/app/error.tsx
index 463eb661..fe4d4948 100644
--- a/src/app/error.tsx
+++ b/src/app/error.tsx
@@ -13,6 +13,7 @@
 import { useEffect } from "react";
 import Link from "next/link";
 
+import { ExceptionHandler } from "@/core/errors";
 import { ROUTES } from "@/router/routes";
 import { Logger } from "@/utils";
 
@@ -29,6 +30,8 @@ export default function GlobalError({ error, unstable_retry }: ErrorProps) {
     log.error("[app/error.tsx]", error);
   }, [error]);
 
+  const errorMessage = ExceptionHandler.message(error, "Unexpected error");
+
   return (
     <div className="flex flex-1 flex-col items-center justify-center gap-md p-lg">
       <h1
@@ -41,7 +44,7 @@ export default function GlobalError({ error, unstable_retry }: ErrorProps) {
         className="max-w-md text-center text-sm"
         style={{ color: "var(--color-text-secondary)" }}
       >
-        {error.message || "Unexpected error"}
+        {errorMessage}
         {error.digest ? ` (digest: ${error.digest})` : null}
       </p>
       <div className="flex gap-sm">
diff --git a/src/app/global-error.tsx b/src/app/global-error.tsx
index 8ec10f92..16589d02 100644
--- a/src/app/global-error.tsx
+++ b/src/app/global-error.tsx
@@ -11,12 +11,19 @@
  * 因为它会替换根 layout。
  */
 
+import { ExceptionHandler } from "@/core/errors";
+
 interface GlobalErrorProps {
   error: Error & { digest?: string };
   unstable_retry?: () => void;
 }
 
 export default function GlobalError({ error }: GlobalErrorProps) {
+  const errorMessage = ExceptionHandler.message(
+    error,
+    "An unexpected error occurred.",
+  );
+
   return (
     <html lang="en">
       <body
@@ -32,7 +39,7 @@ export default function GlobalError({ error }: GlobalErrorProps) {
           Something went wrong
         </h1>
         <p style={{ marginBottom: "1rem", opacity: 0.8 }}>
-          {error.message || "An unexpected error occurred."}
+          {errorMessage}
         </p>
         <button
           type="button"
diff --git a/src/app/subscription/components/stripe-payment-dialog.tsx b/src/app/subscription/components/stripe-payment-dialog.tsx
index f0fc66ec..68c969b7 100644
--- a/src/app/subscription/components/stripe-payment-dialog.tsx
+++ b/src/app/subscription/components/stripe-payment-dialog.tsx
@@ -13,6 +13,7 @@ import {
 } from "@stripe/react-stripe-js";
 import { loadStripe } from "@stripe/stripe-js";
 
+import { ExceptionHandler } from "@/core/errors";
 import { ROUTES } from "@/router/routes";
 import { Logger } from "@/utils";
 
@@ -116,8 +117,10 @@ function StripePaymentForm({
       declineCode: event.error.decline_code,
     });
     setErrorMessage(
-      event.error.message ??
+      ExceptionHandler.message(
+        event.error,
         "Payment methods could not be loaded. Please try again later.",
+      ),
     );
   };
 
@@ -130,7 +133,9 @@ function StripePaymentForm({
 
     const { error: submitError } = await elements.submit();
     if (submitError) {
-      setErrorMessage(submitError.message ?? "Please check your payment info.");
+      setErrorMessage(
+        ExceptionHandler.message(submitError, "Please check your payment info."),
+      );
       setIsSubmitting(false);
       return;
     }
@@ -148,7 +153,9 @@ function StripePaymentForm({
     });
 
     if (error) {
-      setErrorMessage(error.message ?? "Payment confirmation failed.");
+      setErrorMessage(
+        ExceptionHandler.message(error, "Payment confirmation failed."),
+      );
       setIsSubmitting(false);
       return;
     }
diff --git a/src/core/errors/__tests__/exception-handler.test.ts b/src/core/errors/__tests__/exception-handler.test.ts
index 50e83dd9..1c77ddd0 100644
--- a/src/core/errors/__tests__/exception-handler.test.ts
+++ b/src/core/errors/__tests__/exception-handler.test.ts
@@ -96,9 +96,23 @@ describe("ExceptionHandler", () => {
       message: "plain failure",
     });
 
+    expect(ExceptionHandler.handle({ message: "card declined" })).toEqual({
+      code: ExceptionCode.unknown,
+      message: "card declined",
+    });
+
     expect(ExceptionHandler.handle({ nope: true })).toEqual({
       code: ExceptionCode.unknown,
       message: "Something went wrong. Please try again.",
     });
   });
+
+  it("uses call-site fallback text only for unrecognized errors", () => {
+    expect(ExceptionHandler.message({ nope: true }, "Domain fallback")).toBe(
+      "Domain fallback",
+    );
+    expect(ExceptionHandler.message(new Error("specific"), "Domain fallback")).toBe(
+      "specific",
+    );
+  });
 });
diff --git a/src/core/errors/exception-handler.ts b/src/core/errors/exception-handler.ts
index 5748c667..af25343d 100644
--- a/src/core/errors/exception-handler.ts
+++ b/src/core/errors/exception-handler.ts
@@ -1,7 +1,11 @@
 import { AppException } from "./app-exception";
+import { ExceptionCode } from "./exception-code";
 import type { ExceptionResult } from "./exception-result";
 import { ApiExceptionHandler } from "./handlers/api-exception-handler";
-import { FallbackExceptionHandler } from "./handlers/fallback-exception-handler";
+import {
+  DEFAULT_EXCEPTION_MESSAGE,
+  FallbackExceptionHandler,
+} from "./handlers/fallback-exception-handler";
 import { NetworkExceptionHandler } from "./handlers/network-exception-handler";
 import { PaymentExceptionHandler } from "./handlers/payment-exception-handler";
 import { StorageExceptionHandler } from "./handlers/storage-exception-handler";
@@ -36,8 +40,16 @@ export class ExceptionHandler {
     return FallbackExceptionHandler.handle(error);
   }
 
-  static message(error: unknown): string {
-    return ExceptionHandler.handle(error).message;
+  static message(error: unknown, fallbackMessage?: string): string {
+    const result = ExceptionHandler.handle(error);
+    if (
+      fallbackMessage &&
+      result.code === ExceptionCode.unknown &&
+      result.message === DEFAULT_EXCEPTION_MESSAGE
+    ) {
+      return fallbackMessage;
+    }
+    return result.message;
   }
 
   static toError(error: unknown): AppException {
diff --git a/src/core/errors/handlers/fallback-exception-handler.ts b/src/core/errors/handlers/fallback-exception-handler.ts
index c5199a7e..f96cc4e9 100644
--- a/src/core/errors/handlers/fallback-exception-handler.ts
+++ b/src/core/errors/handlers/fallback-exception-handler.ts
@@ -1,6 +1,9 @@
 import { ExceptionCode } from "../exception-code";
 import type { ExceptionResult } from "../exception-result";
 
+export const DEFAULT_EXCEPTION_MESSAGE =
+  "Something went wrong. Please try again.";
+
 export class FallbackExceptionHandler {
   static handle(error: unknown): ExceptionResult {
     return {
@@ -19,5 +22,18 @@ function resolveMessage(error: unknown): string {
     return error;
   }
 
-  return "Something went wrong. Please try again.";
+  if (isMessageLike(error) && error.message.trim().length > 0) {
+    return error.message;
+  }
+
+  return DEFAULT_EXCEPTION_MESSAGE;
+}
+
+function isMessageLike(error: unknown): error is { message: string } {
+  return (
+    typeof error === "object" &&
+    error !== null &&
+    "message" in error &&
+    typeof error.message === "string"
+  );
 }
diff --git a/src/core/net/chat-websocket.ts b/src/core/net/chat-websocket.ts
index f1b785da..83244837 100644
--- a/src/core/net/chat-websocket.ts
+++ b/src/core/net/chat-websocket.ts
@@ -9,6 +9,7 @@
  *   - onError(errorMessage)
  */
 import { getApiConfig } from "@/core/net/config/api_config";
+import { ExceptionHandler } from "@/core/errors";
 import { AppEnvUtil, Logger } from "@/utils";
 
 const log = new Logger("ChatWebSocket");
@@ -89,7 +90,9 @@ export class ChatWebSocket {
       };
     } catch (e) {
       logWebSocketError("✕ WS CONNECT FAILED", e);
-      this.onError?.(e instanceof Error ? e.message : String(e));
+      this.onError?.(
+        ExceptionHandler.message(e, "WebSocket connection failed."),
+      );
     }
   }
 
