Say what actually went wrong

Every failure produced the same reply: read the directions, and check your
context size. For a card Janitor truncated that was fair. For a request
shape the user never chose, or for a bug in sucker, it blamed them for
something they could not have done anything about — and sent them back to
directions they had already followed.

Failures that can be explained now explain themselves: no card in the
request, no greeting in the chat, a card that arrived truncated (which
keeps the context-size advice, since that is where it belongs), and a
request with nothing in it. Anything else is a bug nobody anticipated, so
the reply says as much, says it is not the user's fault, and asks them to
DM @lyseverian on Discord — an unexplained failure nobody reports never
gets fixed. Internals are never echoed back.

SuckerError is recognised by name as well as by identity, because Next can
bundle a module into more than one chunk and a mismatched class would
quietly send every explained error down the unknown-bug path.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NX2SsmUqQftWTZAY4BDuFa

src/app/api/proxy/route.ts

@@ -5,6 +5,13 @@ import {
   tokenCandidates,
   type Message,
 } from "@/lib/messages";
+import {
+  NO_CARD,
+  NO_GREETING,
+  TOO_FEW_MESSAGES,
+  TRUNCATED_CARD,
+  userFacingMessage,
+} from "@/lib/errors";
 
 interface CardVersion {
   version: number;
@@ -122,10 +129,10 @@ function extractCardData(messages: Message[]): ExtractedCard {
   const { system, greeting, nameSlot } = selectMessageSlots(messages);
 
   if (!system) {
-    throw new Error("No system message: this request carries no character card.");
+    throw NO_CARD;
   }
   if (!greeting) {
-    throw new Error("No assistant message: this chat has no greeting to read.");
+    throw NO_GREETING;
   }
 
   const first_mes = greeting.replace(/{user}/g, "{{user}}");
@@ -162,7 +169,7 @@ function extractCardData(messages: Message[]): ExtractedCard {
     !content.includes("<.>") ||
     !content.includes("<UserPersona>.</UserPersona>")
   ) {
-    throw new Error("Required substrings not found");
+    throw TRUNCATED_CARD;
   }
 
   content = content.replace("<.>", "");
@@ -335,12 +342,10 @@ export async function POST(request: NextRequest) {
 
     if (!body.messages || body.messages.length < 2) {
       if (isStreamingRequest) {
-        return createSSEErrorResponse(
-          "Missing messages or insufficient message count"
-        );
+        return createSSEErrorResponse(TOO_FEW_MESSAGES.message);
       }
       return NextResponse.json(
-        { error: "Missing messages or insufficient message count" },
+        { error: TOO_FEW_MESSAGES.message },
         {
           status: 400,
           headers: {
@@ -560,8 +565,7 @@ export async function POST(request: NextRequest) {
   } catch (error) {
     console.error("Error processing request:", error);
 
-    const errorMessage =
-      "You dingus, read the directions on sucker before trying again. If you're trying to suck a bot with more tokens than your current context limit, try bumping your Context Size setting up on Generation Settings.";
+    const errorMessage = userFacingMessage(error);
 
     // Check if this was a streaming request
     const acceptHeader = request.headers.get("accept");