fix(embeddings): strip stale Content-Encoding headers from upstream response (#2477)

Integrated into release/v3.8.2

open-sse/handlers/embeddings.ts

@@ -23,6 +23,7 @@ import { createRequestLogger } from "../utils/requestLogger.ts";
 import { isDetailedLoggingEnabled } from "@/lib/db/detailedLogs";
 import { getCallLogPipelineCaptureStreamChunks } from "@/lib/logEnv";
 import { toJsonErrorPayload } from "@/shared/utils/upstreamError";
+import { stripStaleEncodingHeaders } from "../utils/upstreamResponseHeaders.ts";
 
 interface ClientRawRequest {
   endpoint: string;
@@ -215,7 +216,7 @@ export async function handleEmbedding({
         success: false,
         status: response.status,
         error: errorText,
-        headers: response.headers,
+        headers: stripStaleEncodingHeaders(response.headers),
       };
     }
 
@@ -266,7 +267,7 @@ export async function handleEmbedding({
     return {
       success: true,
       data: normalizedResponse,
-      headers: response.headers,
+      headers: stripStaleEncodingHeaders(response.headers),
     };
   } catch (err) {
     if (log) {

tests/unit/embeddings-handler.test.ts

@@ -215,3 +215,75 @@ test("handleEmbedding surfaces upstream failures", async () => {
     globalThis.fetch = originalFetch;
   }
 });
+
+test("handleEmbedding strips content-encoding header on success path", async () => {
+  const originalFetch = globalThis.fetch;
+
+  globalThis.fetch = async () =>
+    new Response(
+      JSON.stringify({
+        data: [{ object: "embedding", embedding: [0.1, 0.2], index: 0 }],
+        usage: { prompt_tokens: 5, total_tokens: 5 },
+      }),
+      {
+        status: 200,
+        headers: {
+          "content-type": "application/json",
+          "content-encoding": "gzip",
+          "content-length": "512",
+          "transfer-encoding": "chunked",
+          "x-request-id": "abc123",
+        },
+      }
+    );
+
+  try {
+    const result = await handleEmbedding({
+      body: { model: "openai/text-embedding-3-small", input: "test" },
+      credentials: { apiKey: "openai-key" },
+      log: null,
+    });
+
+    assert.equal(result.success, true);
+    assert.strictEqual(result.headers.get("content-encoding"), null);
+    assert.strictEqual(result.headers.get("content-length"), null);
+    assert.strictEqual(result.headers.get("transfer-encoding"), null);
+    assert.strictEqual(result.headers.get("x-request-id"), "abc123");
+    assert.strictEqual(result.headers.get("content-type"), "application/json");
+  } finally {
+    globalThis.fetch = originalFetch;
+  }
+});
+
+test("handleEmbedding strips content-encoding header on error path", async () => {
+  const originalFetch = globalThis.fetch;
+
+  globalThis.fetch = async () =>
+    new Response("upstream error", {
+      status: 502,
+      headers: {
+        "content-type": "text/plain",
+        "content-encoding": "gzip",
+        "content-length": "42",
+        "transfer-encoding": "chunked",
+        "x-trace-id": "trace-456",
+      },
+    });
+
+  try {
+    const result = await handleEmbedding({
+      body: { model: "openai/text-embedding-3-small", input: "test" },
+      credentials: { apiKey: "openai-key" },
+      log: null,
+    });
+
+    assert.equal(result.success, false);
+    assert.equal(result.status, 502);
+    assert.strictEqual(result.headers.get("content-encoding"), null);
+    assert.strictEqual(result.headers.get("content-length"), null);
+    assert.strictEqual(result.headers.get("transfer-encoding"), null);
+    assert.strictEqual(result.headers.get("x-trace-id"), "trace-456");
+  } finally {
+    globalThis.fetch = originalFetch;
+  }
+});