v3.11.10: fix Antigravity — interleave function_call/output pairs, trim Gemini turns (PR #11)

src/codex-launcher-gui

@@ -27,6 +27,10 @@ model_catalog_json = ""
 """
 
 CHANGELOG = [
+    ("3.11.10", "2026-05-26", [
+        "Fix Antigravity: interleave function_call/output pairs (PR #11)",
+        "Gemini sanitizer: trim non-user turns for Google API compliance",
+    ]),
     ("3.11.9", "2026-05-26", [
         "Fix Antigravity: preserve functionCall/functionResponse (PR #10)",
         "Prevents tool responses from being dropped in multi-turn sessions",

src/codex_launcher_lib.py

@@ -83,6 +83,11 @@ model_catalog_json = ""
 """
 
 CHANGELOG = [
+    ("3.11.10", "2026-05-26", [
+        "Fix Antigravity: interleave function_call/output pairs in correct sequence (PR #11)",
+        "Fix Gemini sanitizer: trim leading/trailing non-user turns for Google API compliance",
+        "Stricter function call/response isolation — no merging across role boundaries",
+    ]),
     ("3.11.9", "2026-05-26", [
         "Fix Antigravity: preserve functionCall/functionResponse in Gemini sanitizer (PR #10)",
         "Prevents tool responses from being merged/dropped in multi-turn Antigravity sessions",

src/translate-proxy.py

@@ -4958,6 +4958,7 @@ def _antigravity_normalize_context(input_data, model=""):
         if cid in tool_call_ids:
             paired_calls.append((idx, item))
 
+    # Build result maintaining proper function_call -> function_call_output pairing
     result = list(dev_messages)
 
     compaction_summaries = []
@@ -4973,11 +4974,30 @@ def _antigravity_normalize_context(input_data, model=""):
         summary_text = f"[Tool history summary: {n_summarized} older tool outputs omitted. {n_tool_calls} prior function calls were made for file inspection/editing.]"
         result.append({"type": "message", "role": "user", "content": [{"type": "input_text", "text": summary_text}]})
 
-    for _, call_item in paired_calls:
-        result.append(call_item)
-
+    # CRITICAL FIX: Interleave function_calls with their corresponding function_call_outputs
+    # to maintain the required sequence: function_call -> function_call_output -> function_call -> ...
+    # Build a lookup map: call_id -> function_call_output item
+    tool_output_map = {}
     for _, tool_item in kept_tools:
-        result.append(tool_item)
+        cid = tool_item.get("call_id", tool_item.get("id", ""))
+        if cid:
+            tool_output_map[cid] = tool_item
+
+    # First, add all paired function_calls followed immediately by their responses
+    added_call_ids = set()
+    for _, call_item in paired_calls:
+        cid = call_item.get("call_id", call_item.get("id", ""))
+        result.append(call_item)
+        added_call_ids.add(cid)
+        # Immediately append the corresponding function_call_output if available
+        if cid in tool_output_map:
+            result.append(tool_output_map[cid])
+
+    # Add any remaining tool outputs that weren't paired (orphans)
+    for _, tool_item in kept_tools:
+        cid = tool_item.get("call_id", tool_item.get("id", ""))
+        if cid not in added_call_ids:
+            result.append(tool_item)
 
     for cs_item in compaction_summaries:
         result.append(cs_item)
@@ -5569,17 +5589,21 @@ class Handler(http.server.BaseHTTPRequestHandler):
                 # Skip duplicate user text messages, but NEVER skip function responses
                 if role == "user" and text_key and text_key == last_user_text and not has_function_response:
                     continue
-                # Only merge same-role messages if they don't contain function calls/responses
-                # Function calls and responses must remain as separate turns
+                # CRITICAL FIX: Function calls (model role) and function responses (user role) MUST NOT be merged
+                # Google's API requires strict alternation: functionCall (model) -> functionResponse (user)
+                # Never merge across role boundaries when function calls/responses are involved
                 if role == last_role and role in ("user", "model") and sanitized and not has_function_call and not has_function_response:
+                    # Only merge same-role consecutive text messages without tool content
                     sanitized[-1].setdefault("parts", []).extend(parts)
                 else:
                     sanitized.append({"role": role, "parts": parts})
                 if role == "user" and text_key:
                     last_user_text = text_key
                 last_role = role
+            # Trim leading non-user messages (Google expects conversation to start with user)
             while sanitized and sanitized[0].get("role") != "user":
                 sanitized.pop(0)
+            # Trim trailing non-user messages (must end with user turn for continuation)
             while sanitized and sanitized[-1].get("role") != "user":
                 sanitized.pop()
             contents = sanitized