diff --git a/open-sse/translator/helpers/claudeHelper.ts b/open-sse/translator/helpers/claudeHelper.ts
index bf4e589d0f..d42c86dc08 100644
--- a/open-sse/translator/helpers/claudeHelper.ts
+++ b/open-sse/translator/helpers/claudeHelper.ts
@@ -148,11 +148,14 @@ export function prepareClaudeRequest(
 ): ClaudeRequestBody {
   // 1. System: remove all cache_control, add only to last block with ttl 1h
   // In passthrough mode, preserve existing cache_control markers
+  const supportsPromptCaching =
+    provider === "claude" || provider?.startsWith?.("anthropic-compatible-");
+
   const systemBlocks = body.system;
   if (systemBlocks && Array.isArray(systemBlocks) && !preserveCacheControl) {
     body.system = systemBlocks.map((block, i) => {
       const { cache_control, ...rest } = block;
-      if (i === systemBlocks.length - 1) {
+      if (i === systemBlocks.length - 1 && supportsPromptCaching) {
         return { ...rest, cache_control: { type: "ephemeral", ttl: "1h" } };
       }
       return rest;
@@ -217,7 +220,7 @@ export function prepareClaudeRequest(
     // - cache the second-to-last user turn for conversation reuse
     // - cache the last assistant turn so the next user turn can reuse it
     // Skip in passthrough mode to preserve client's cache_control markers
-    if (!preserveCacheControl) {
+    if (!preserveCacheControl && supportsPromptCaching) {
       const userMessageIndexes = filtered.reduce<number[]>((indexes, msg, index) => {
         if (msg?.role === "user") indexes.push(index);
         return indexes;
@@ -238,7 +241,12 @@ export function prepareClaudeRequest(
       if (msg.role === "assistant" && content.length > 0) {
         // Add cache_control to last block of first (from end) assistant with content
         // Skip in passthrough mode to preserve client's cache_control markers
-        if (!preserveCacheControl && !lastAssistantProcessed && markMessageCacheControl(msg)) {
+        if (
+          !preserveCacheControl &&
+          supportsPromptCaching &&
+          !lastAssistantProcessed &&
+          markMessageCacheControl(msg)
+        ) {
           lastAssistantProcessed = true;
         }
 
@@ -283,10 +291,12 @@ export function prepareClaudeRequest(
       const { cache_control, ...rest } = tool;
       return rest;
     });
-    for (let i = body.tools.length - 1; i >= 0; i--) {
-      if (!body.tools[i].defer_loading) {
-        body.tools[i].cache_control = { type: "ephemeral", ttl: "1h" };
-        break;
+    if (supportsPromptCaching) {
+      for (let i = body.tools.length - 1; i >= 0; i--) {
+        if (!body.tools[i].defer_loading) {
+          body.tools[i].cache_control = { type: "ephemeral", ttl: "1h" };
+          break;
+        }
       }
     }
   }
diff --git a/open-sse/translator/request/openai-to-gemini.ts b/open-sse/translator/request/openai-to-gemini.ts
index 69b3075c9e..5e854ec996 100644
--- a/open-sse/translator/request/openai-to-gemini.ts
+++ b/open-sse/translator/request/openai-to-gemini.ts
@@ -538,27 +538,23 @@ function wrapInCloudCodeEnvelopeForClaude(model, claudeRequest, credentials = nu
     });
     if (geminiTools) {
       envelope.request.tools = geminiTools;
-      envelope.request.toolConfig = {
-        functionCallingConfig: { mode: "VALIDATED" },
-      };
     }
   }
 
   // Add system instruction (Antigravity default)
-  const defaultPart = { text: ANTIGRAVITY_DEFAULT_SYSTEM };
-  const systemParts = [defaultPart];
+  let combinedSystemText = ANTIGRAVITY_DEFAULT_SYSTEM;
 
   if (claudeRequest.system) {
     if (Array.isArray(claudeRequest.system)) {
       for (const block of claudeRequest.system) {
-        if (block.text) systemParts.push({ text: block.text });
+        if (block.text) combinedSystemText += "\n\n" + block.text;
       }
     } else if (typeof claudeRequest.system === "string") {
-      systemParts.push({ text: claudeRequest.system });
+      combinedSystemText += "\n\n" + claudeRequest.system;
     }
   }
 
-  envelope.request.systemInstruction = { role: "user", parts: systemParts };
+  envelope.request.systemInstruction = { role: "user", parts: [{ text: combinedSystemText }] };
 
   const changedToolNameMap = buildChangedToolNameMap(toolNameMap);
   if (changedToolNameMap) {