diff --git a/README.md b/README.md
index 42ddb80..42a2c9a 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ You can also build and run Sucker as a Docker container with `docker compose bui
 
 ### Changelog
 
-- 2.5: Unread dot on the Changelog button. Fixed extraction for users whose Janitor sends a request without the blank turn before the first message — sucker read the parts by position rather than by role, so for them it read the wrong ones and errored. Now resolved by role, with tests for both shapes.
+- 2.5: Real error messages instead of one blanket "dingus" reply; unexplained failures now ask you to DM @lyseverian. Unread dot on the Changelog button. Fixed extraction for users whose Janitor sends a request without the blank turn before the first message — sucker read the parts by position rather than by role, so for them it read the wrong ones and errored. Now resolved by role, with tests for both shapes.
 - 2.4: CSS editor for Janitor profiles. New banner links to the live-preview editor at tools.from-avalon.com/janitor-profile-maker.
 - 2.3: ECHO. Put ECHO: anywhere in a message and sucker repeats whatever comes after it in the reply — for triggering char-side script and lorebook keywords.
 - 2.2: Added support for directly inputting webp file names or character image links when creating PNG character cards
diff --git a/src/app/api/proxy/route.ts b/src/app/api/proxy/route.ts
index 5f76ed9..1e30742 100644
--- a/src/app/api/proxy/route.ts
+++ b/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");
diff --git a/src/app/page.tsx b/src/app/page.tsx
index eb5882d..813dab1 100644
--- a/src/app/page.tsx
+++ b/src/app/page.tsx
@@ -1025,6 +1025,12 @@ export default function Home() {
                   The Changelog button also carries a dot now when there is
                   something here you haven&apos;t read.
                 </p>
+                <p>
+                  And when something does go wrong, sucker now tells you what
+                  actually happened instead of calling you a dingus. If it hits
+                  something it cannot explain, it says so and asks you to DM
+                  @lyseverian on Discord — those are the ones worth hearing about.
+                </p>
               </div>
             </div>
             <Separator />
diff --git a/src/lib/errors.ts b/src/lib/errors.ts
new file mode 100644
index 0000000..98ce706
--- /dev/null
+++ b/src/lib/errors.ts
@@ -0,0 +1,71 @@
+/**
+ * Telling people what actually went wrong.
+ *
+ * Every failure used to produce one message: "You dingus, read the directions
+ * on sucker before trying again", with a note about context size. For a
+ * truncated card 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 told them to check directions they had already followed.
+ *
+ * So: anything thrown as a SuckerError is written for the person who hit it
+ * and is shown to them verbatim. Anything else is a bug nobody anticipated,
+ * and the reply says so and asks them to report it, because an unexplained
+ * failure that nobody hears about never gets fixed.
+ */
+
+/** Where to send someone when sucker is at fault. */
+export const CONTACT = "DM @lyseverian on Discord";
+
+export class SuckerError extends Error {
+  constructor(message: string) {
+    super(message);
+    this.name = "SuckerError";
+  }
+}
+
+/**
+ * `instanceof` is checked by name as well: Next can bundle the same module
+ * into more than one chunk, and a class identity that differs between them
+ * would quietly send every explained error down the "unknown bug" path.
+ */
+export function isSuckerError(error: unknown): error is SuckerError {
+  return (
+    error instanceof SuckerError ||
+    (typeof error === "object" &&
+      error !== null &&
+      (error as { name?: unknown }).name === "SuckerError")
+  );
+}
+
+export function userFacingMessage(error: unknown): string {
+  if (isSuckerError(error)) return error.message;
+  return (
+    "Something went wrong that sucker has no explanation for, and nothing was " +
+    `saved. This one is not your fault — please ${CONTACT} and say what you ` +
+    "were pulling, because unreported ones do not get fixed."
+  );
+}
+
+/** The card arrived without the markers sucker needs to read it. */
+export const TRUNCATED_CARD = new SuckerError(
+  "The card came through incomplete — the markers sucker looks for are not in " +
+    "it. That usually means the bot is larger than your context size and " +
+    "Janitor cut it short, so raise Context Size in Generation Settings and " +
+    `try again. If it is already generous, re-read the directions on sucker, and ${CONTACT} if it still will not go.`
+);
+
+export const NO_CARD = new SuckerError(
+  "There is no character card in that request — sucker could not find a " +
+    "system message in it. Point sucker at a chat with a bot in it, not an " +
+    "empty one, and try again."
+);
+
+export const NO_GREETING = new SuckerError(
+  "That chat has no message from the bot yet, so there is nothing to pull. " +
+    "Open the chat until the bot's first message shows, then send again."
+);
+
+export const TOO_FEW_MESSAGES = new SuckerError(
+  "That request barely had anything in it — sucker needs a chat with a bot " +
+    "and at least one message in it. Open the chat properly and try again."
+);
diff --git a/tests/errors.test.ts b/tests/errors.test.ts
new file mode 100644
index 0000000..e596eb1
--- /dev/null
+++ b/tests/errors.test.ts
@@ -0,0 +1,44 @@
+/**
+ * Which failures explain themselves, and which ask to be reported.
+ */
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import {
+  CONTACT,
+  NO_CARD,
+  NO_GREETING,
+  SuckerError,
+  TOO_FEW_MESSAGES,
+  TRUNCATED_CARD,
+  isSuckerError,
+  userFacingMessage,
+} from "../src/lib/errors.ts";
+
+test("an explained failure is shown to the user as written", () => {
+  for (const e of [NO_CARD, NO_GREETING, TOO_FEW_MESSAGES, TRUNCATED_CARD]) {
+    assert.equal(userFacingMessage(e), e.message);
+    assert.ok(!/dingus/i.test(e.message), "nobody is called a dingus for these");
+  }
+});
+
+test("an unexplained failure owns it and asks to be reported", () => {
+  const msg = userFacingMessage(new TypeError("Cannot read properties of undefined"));
+  assert.match(msg, /not your fault/i);
+  assert.ok(msg.includes(CONTACT), "must say where to report it");
+  // The internals must not leak into a user-facing reply.
+  assert.ok(!msg.includes("Cannot read properties"));
+});
+
+test("the truncated-card case keeps the context-size advice", () => {
+  assert.match(TRUNCATED_CARD.message, /Context Size/);
+  assert.ok(TRUNCATED_CARD.message.includes(CONTACT));
+});
+
+test("recognised across module boundaries, not just by identity", () => {
+  assert.ok(isSuckerError(new SuckerError("x")));
+  // What a second copy of the class in another bundle would look like.
+  assert.ok(isSuckerError({ name: "SuckerError", message: "x" }));
+  assert.ok(!isSuckerError(new Error("x")));
+  assert.ok(!isSuckerError(null));
+  assert.ok(!isSuckerError("SuckerError"));
+});