feat(cloud): harden sync/auth flow, SSE fallback, and update changelog

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/handlers/chatCore.js

@@ -225,6 +225,81 @@ function extractUsageFromResponse(responseBody, provider) {
   return null;
 }
 
+/**
+ * Convert OpenAI-style SSE chunks into a single non-streaming JSON response.
+ * Used as a fallback when upstream returns text/event-stream for stream=false.
+ */
+function parseSSEToOpenAIResponse(rawSSE, fallbackModel) {
+  const lines = String(rawSSE || "").split("\n");
+  const chunks = [];
+
+  for (const line of lines) {
+    const trimmed = line.trim();
+    if (!trimmed.startsWith("data:")) continue;
+    const payload = trimmed.slice(5).trim();
+    if (!payload || payload === "[DONE]") continue;
+    try {
+      chunks.push(JSON.parse(payload));
+    } catch {
+      // Ignore malformed SSE lines and continue best-effort parsing.
+    }
+  }
+
+  if (chunks.length === 0) return null;
+
+  const first = chunks[0];
+  const contentParts = [];
+  const reasoningParts = [];
+  let finishReason = "stop";
+  let usage = null;
+
+  for (const chunk of chunks) {
+    const choice = chunk?.choices?.[0];
+    const delta = choice?.delta || {};
+
+    if (typeof delta.content === "string" && delta.content.length > 0) {
+      contentParts.push(delta.content);
+    }
+    if (typeof delta.reasoning_content === "string" && delta.reasoning_content.length > 0) {
+      reasoningParts.push(delta.reasoning_content);
+    }
+    if (choice?.finish_reason) {
+      finishReason = choice.finish_reason;
+    }
+    if (chunk?.usage && typeof chunk.usage === "object") {
+      usage = chunk.usage;
+    }
+  }
+
+  const message = {
+    role: "assistant",
+    content: contentParts.join("")
+  };
+  if (reasoningParts.length > 0) {
+    message.reasoning_content = reasoningParts.join("");
+  }
+
+  const result = {
+    id: first.id || `chatcmpl-${Date.now()}`,
+    object: "chat.completion",
+    created: first.created || Math.floor(Date.now() / 1000),
+    model: first.model || fallbackModel || "unknown",
+    choices: [
+      {
+        index: 0,
+        message,
+        finish_reason: finishReason
+      }
+    ]
+  };
+
+  if (usage) {
+    result.usage = usage;
+  }
+
+  return result;
+}
+
 /**
  * Core chat handler - shared between SSE and Worker
  * Returns { success, response, status, error } for caller to handle fallback
@@ -406,7 +481,21 @@ export async function handleChatCore({ body, modelInfo, credentials, log, onCred
   // Non-streaming response
   if (!stream) {
     trackPendingRequest(model, provider, connectionId, false);
-    const responseBody = await providerResponse.json();
+    const contentType = providerResponse.headers.get("content-type") || "";
+    let responseBody;
+
+    if (contentType.includes("text/event-stream")) {
+      // Upstream returned SSE even though stream=false; convert best-effort to JSON.
+      const sseText = await providerResponse.text();
+      const parsedFromSSE = parseSSEToOpenAIResponse(sseText, model);
+      if (!parsedFromSSE) {
+        appendRequestLog({ model, provider, connectionId, status: `FAILED ${HTTP_STATUS.BAD_GATEWAY}` }).catch(() => { });
+        return createErrorResult(HTTP_STATUS.BAD_GATEWAY, "Invalid SSE response for non-streaming request");
+      }
+      responseBody = parsedFromSSE;
+    } else {
+      responseBody = await providerResponse.json();
+    }
 
     // Notify success - caller can clear error status if needed
     if (onRequestSuccess) {
@@ -507,4 +596,4 @@ export function isTokenExpiringSoon(expiresAt, bufferMs = 5 * 60 * 1000) {
   if (!expiresAt) return false;
   const expiresAtMs = new Date(expiresAt).getTime();
   return expiresAtMs - Date.now() < bufferMs;
-}
+}