fix(translator): strict Anthropic content block compliance (#2225)

Filter empty text blocks from thoughtSignature-only parts, preserve
tool_calls when functionResponse and functionCall coexist in the same
content, and skip empty regular text parts before they reach Claude.

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

open-sse/translator/request/antigravity-to-openai.js

@@ -138,12 +138,14 @@ function convertContent(content) {
 
     // Text with thoughtSignature = regular text after thinking
     if (part.thoughtSignature && part.text !== undefined) {
-      textParts.push({ type: OPENAI_BLOCK.TEXT, text: part.text });
+      if (part.text) {
+        textParts.push({ type: OPENAI_BLOCK.TEXT, text: part.text });
+      }
       continue;
     }
 
     // Regular text
-    if (part.text !== undefined) {
+    if (part.text !== undefined && part.text !== "") {
       textParts.push({ type: OPENAI_BLOCK.TEXT, text: part.text });
     }
 
@@ -180,8 +182,22 @@ function convertContent(content) {
     }
   }
 
-  // Content with only functionResponses → return array of tool messages
+  // Content with functionResponses — return array of tool result messages,
+  // plus an assistant message for any co-located tool calls / text.
   if (toolResults.length > 0) {
+    if (toolCalls.length > 0 || textParts.length > 0 || reasoningContent) {
+      const assistantMsg = { role: ROLE.ASSISTANT };
+      if (textParts.length > 0) {
+        assistantMsg.content = collapseTextParts(textParts);
+      }
+      if (reasoningContent) {
+        assistantMsg.reasoning_content = reasoningContent;
+      }
+      if (toolCalls.length > 0) {
+        assistantMsg.tool_calls = toolCalls;
+      }
+      return [...toolResults, assistantMsg];
+    }
     return toolResults;
   }
 

tests/translator/bugs-antigravity.test.js

@@ -9,10 +9,9 @@ const AG2O = (req) =>
   translateRequest(FORMATS.ANTIGRAVITY, FORMATS.OPENAI, "m", { request: req }, true, null, null);
 
 describe("Antigravity → OpenAI", () => {
-  // antigravity-to-openai.js:177-189 — content with BOTH functionResponse and functionCall/text
+  // antigravity-to-openai.js — content with BOTH functionResponse and functionCall/text
-  // returns toolResults early → drops the tool calls / text.
+  // previously returned toolResults early → dropped tool calls / text (fixed in #2225)
-  // KNOWN BUG
+  it("functionResponse + functionCall in same content keeps both", () => {
-  it.fails("functionResponse + functionCall in same content keeps both", () => {
     const out = AG2O({
       contents: [{
         role: "model",