adds ?debug=true query param to have proxy respond with transformed prompt

src/proxy/middleware/common.ts

@@ -56,10 +56,6 @@ export function sendProxyError(
       ? `The proxy encountered an error while trying to process your prompt.`
       : `The proxy encountered an error while trying to send your prompt to the upstream service.`;
 
-  if (req.tokenizerInfo && typeof errorPayload.error === "object") {
-    errorPayload.error.proxy_tokenizer = req.tokenizerInfo;
-  }
-
   sendErrorToClient({
     options: {
       format: req.inboundApi,

src/proxy/middleware/response/error-generator.ts

@@ -26,15 +26,6 @@ function getMessageContent({
    "error": {
      "type": "not_found_error",
      "message": "model: some-invalid-model-id",
-     "proxy_tokenizer": {
-       "tokenizer": "@anthropic-ai/tokenizer",
-       "token_count": 6104,
-       "tokenization_duration_ms": 4.0765,
-       "prompt_tokens": 6104,
-       "completion_tokens": 30,
-       "max_model_tokens": 200000,
-       "max_proxy_tokens": 9007199254740991
-      }
     },
    "proxy_note": "The requested Claude model might not exist, or the key might not be provisioned for it."
   }

src/proxy/middleware/response/index.ts

@@ -23,6 +23,7 @@ import {
 import { handleStreamedResponse } from "./handle-streamed-response";
 import { logPrompt } from "./log-prompt";
 import { saveImage } from "./save-image";
+import { config } from "../../../config";
 
 const DECODER_MAP = {
   gzip: util.promisify(zlib.gunzip),
@@ -105,6 +106,7 @@ export const createOnProxyResHandler = (apiMiddleware: ProxyResMiddleware) => {
       } else {
         middlewareStack.push(
           trackRateLimit,
+          addProxyInfo,
           handleUpstreamErrors,
           countResponseTokens,
           incrementUsage,
@@ -706,6 +708,38 @@ const copyHttpHeaders: ProxyResHandlerWithBody = async (
   });
 };
 
+/**
+ * Injects metadata into the response, such as the tokenizer used, logging
+ * status, upstream API endpoint used, and whether the input prompt was modified
+ * or transformed.
+ * Only used for non-streaming requests.
+ */
+const addProxyInfo: ProxyResHandlerWithBody = async (
+  _proxyRes,
+  req,
+  res,
+  body
+) => {
+  const { service, inboundApi, outboundApi, tokenizerInfo } = req;
+  const native = inboundApi === outboundApi;
+  const info: any = {
+    logged: config.promptLogging,
+    tokens: tokenizerInfo,
+    service,
+    in_api: inboundApi,
+    out_api: outboundApi,
+    prompt_transformed: !native,
+  };
+
+  if (req.query?.debug?.length) {
+    info.final_request_body = req.signedRequest?.body || req.body;
+  }
+
+  if (typeof body === "object") {
+    body.proxy = info;
+  }
+};
+
 function getAwsErrorType(header: string | string[] | undefined) {
   const val = String(header).match(/^(\w+):?/)?.[1];
   return val || String(header);