diff --git a/open-sse/handlers/chatCore/nonStreamingHandler.js b/open-sse/handlers/chatCore/nonStreamingHandler.js
index 3b42612..93d3d88 100644
--- a/open-sse/handlers/chatCore/nonStreamingHandler.js
+++ b/open-sse/handlers/chatCore/nonStreamingHandler.js
@@ -185,6 +185,14 @@ export async function handleNonStreamingResponse({ providerResponse, provider, m
     translatedResponse.usage = filterUsageForFormat(addBufferToUsage(translatedResponse.usage), sourceFormat);
   }
 
+  // Strip reasoning_content — some clients (e.g. Firecrawl AI SDK) have JSON parsers that
+  // break on this non-standard field, even though OpenAI allows it in extensions.
+  if (translatedResponse?.choices) {
+    for (const choice of translatedResponse.choices) {
+      if (choice?.message) delete choice.message.reasoning_content;
+    }
+  }
+
   reqLogger.logConvertedResponse(translatedResponse);
 
   const totalLatency = Date.now() - requestStartTime;
diff --git a/open-sse/handlers/chatCore/sseToJsonHandler.js b/open-sse/handlers/chatCore/sseToJsonHandler.js
index a3a69a1..b7fabe3 100644
--- a/open-sse/handlers/chatCore/sseToJsonHandler.js
+++ b/open-sse/handlers/chatCore/sseToJsonHandler.js
@@ -210,6 +210,13 @@ export async function handleForcedSSEToJson({ providerResponse, sourceFormat, pr
       status: "success"
     }, { endpoint: clientRawRequest?.endpoint || null })).catch(() => {});
 
+    // Strip reasoning_content — breaks JSON parsers in some clients (e.g. Firecrawl AI SDK)
+    if (parsed?.choices) {
+      for (const choice of parsed.choices) {
+        if (choice?.message) delete choice.message.reasoning_content;
+      }
+    }
+
     return { success: true, response: new Response(JSON.stringify(parsed), { headers: { "Content-Type": "application/json", "Access-Control-Allow-Origin": "*" } }) };
   } catch (err) {
     console.error("[ChatCore] Chat Completions SSE→JSON failed:", err);