shows more helpful errors when users' prefills are invalid during AWS streaming

src/proxy/middleware/response/handle-streamed-response.ts

@@ -6,7 +6,6 @@ import { APIFormat, keyPool } from "../../../shared/key-management";
 import {
   copySseResponseHeaders,
   initializeSseStream,
-
 } from "../../../shared/streaming";
 import type { logger } from "../../../logger";
 import { enqueue } from "../../queue";
@@ -15,7 +14,8 @@ import { getAwsEventStreamDecoder } from "./streaming/aws-event-stream-decoder";
 import { EventAggregator } from "./streaming/event-aggregator";
 import { SSEMessageTransformer } from "./streaming/sse-message-transformer";
 import { SSEStreamAdapter } from "./streaming/sse-stream-adapter";
-import { buildSpoofedSSE } from "./error-generator";
+import { buildSpoofedSSE, sendErrorToClient } from "./error-generator";
+import { BadRequestError } from "../../../shared/errors";
 
 const pipelineAsync = promisify(pipeline);
 
@@ -109,6 +109,18 @@ export const handleStreamedResponse: RawResponseBodyHandler = async (
       );
       req.retryCount++;
       await enqueue(req);
+    } else if (err instanceof BadRequestError) {
+      sendErrorToClient({
+        req,
+        res,
+        options: {
+          format: req.inboundApi,
+          title: "Proxy streaming error (Bad Request)",
+          message: `The API returned an error while streaming your request. Your prompt might not be formatted correctly.\n\n*${err.message}*`,
+          reqId: req.id,
+          model: req.body?.model,
+        },
+      });
     } else {
       const { message, stack, lastEvent } = err;
       const eventText = JSON.stringify(lastEvent, null, 2) ?? "undefined";

src/proxy/middleware/response/streaming/sse-stream-adapter.ts

@@ -4,6 +4,7 @@ import { Message } from "@smithy/eventstream-codec";
 import { APIFormat } from "../../../../shared/key-management";
 import { RetryableError } from "../index";
 import { buildSpoofedSSE } from "../error-generator";
+import { BadRequestError } from "../../../../shared/errors";
 
 type SSEStreamAdapterOptions = TransformOptions & {
   contentType?: string;
@@ -59,8 +60,7 @@ export class SSEStreamAdapter extends Transform {
             return [`event: ${eventObj.type}`, `data: ${event}`].join(`\n`);
           }
         }
-      // Intentional fallthrough, as non-JSON events may as well be errors
-      // noinspection FallThroughInSwitchStatementJS
+      // noinspection FallThroughInSwitchStatementJS -- non-JSON data is unexpected
       case "exception":
       case "error":
         const type = String(
@@ -72,16 +72,32 @@ export class SSEStreamAdapter extends Transform {
               "AWS request throttled after streaming has already started; retrying"
             );
             throw new RetryableError("AWS request throttled mid-stream");
+          case "validationexception":
+            try {
+              const { message } = JSON.parse(bodyStr);
+              this.log.error({ message }, "Received AWS validation error");
+              this.emit(
+                "error",
+                new BadRequestError(`AWS validation error: ${message}`)
+              );
+              return null;
+            } catch (error) {
+              this.log.error(
+                { body: bodyStr, error },
+                "Could not parse AWS validation error"
+              );
+            }
+          // noinspection FallThroughInSwitchStatementJS -- who knows what this is
           default:
-            this.log.error({ message, type }, "Received bad AWS stream event");
             let text;
             try {
-              const { bytes } = JSON.parse(bodyStr);
-              text = Buffer.from(bytes, "base64").toString("utf8");
+              text = JSON.parse(bodyStr).message;
             } catch (error) {
               text = bodyStr;
             }
-            const error: any = new Error(`Got mysterious error chunk: ${type}`);
+            const error: any = new Error(
+              `Got mysterious error chunk: [${type}] ${text}`
+            );
             error.lastEvent = text;
             this.emit("error", error);
             return null;