fix(gemini): normalize contents and handle intermediate tool responses in Antigravity

Co-Authored-By: Claude Code <noreply@anthropic.com>

open-sse/executors/antigravity.js

@@ -5,7 +5,7 @@ import { OAUTH_ENDPOINTS, ANTIGRAVITY_HEADERS, AG_DEFAULT_TOOLS, AG_TOOL_SUFFIX,
 import { HTTP_STATUS } from "../config/runtimeConfig.js";
 import { resolveSessionId, toNumericSessionId } from "../utils/sessionManager.js";
 import { proxyAwareFetch } from "../utils/proxyFetch.js";
-import { cleanJSONSchemaForAntigravity } from "../translator/formats/gemini.js";
+import { cleanJSONSchemaForAntigravity, normalizeGeminiContents } from "../translator/formats/gemini.js";
 import { DEFAULT_THINKING_AG_SIGNATURE } from "../config/defaultThinkingSignature.js";
 import { getGeminiThoughtSignatureSync } from "../services/thoughtSignatureStore.js";
 
@@ -193,7 +193,7 @@ export class AntigravityExecutor extends BaseExecutor {
 
     // ─── Standard (non-image) request ───
     // Fix contents for Claude models via Antigravity
-    const contents = body.request?.contents?.map(c => {
+    const rawContents = (body.request?.contents || []).map(c => {
       let role = c.role;
       // functionResponse must be role "user" for Claude models
       if (c.parts?.some(p => p.functionResponse)) {
@@ -226,15 +226,13 @@ export class AntigravityExecutor extends BaseExecutor {
         return p;
       });
 
-      const partsChanged = parts?.length !== c.parts?.length || modifiedParts?.some((p, idx) => p !== c.parts[idx]);
-      if (role !== c.role || partsChanged) {
-        return {
-          ...c, role,
-          parts: modifiedParts || parts,
-        };
-      }
-      return c;
+      return {
+        ...c,
+        role,
+        parts: modifiedParts || parts || [],
+      };
     });
+    const contents = normalizeGeminiContents(rawContents);
 
     // Sanitize tool schemas and function names before sending to Antigravity.
     let tools = body.request?.tools;

open-sse/translator/formats/gemini.js

@@ -432,3 +432,21 @@ export function cleanJSONSchemaForAntigravity(schema) {
   return cleaned;
 }
 
+// Merge adjacent same-role messages, strip empty parts, ensure initial user turn
+export function normalizeGeminiContents(contents) {
+  const out = [];
+  for (const c of contents || []) {
+    if (!c?.role || !Array.isArray(c.parts)) continue;
+    const parts = c.parts.filter(p => p && Object.keys(p).length > 0);
+    if (parts.length === 0) continue;
+    const last = out.at(-1);
+    if (last?.role === c.role) last.parts.push(...parts);
+    else out.push({ ...c, parts: [...parts] });
+  }
+  if (out.length > 0 && out[0].role !== "user") {
+    out.unshift({ role: "user", parts: [{ text: "..." }] });
+  }
+  return out;
+}
+
+

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

@@ -15,7 +15,8 @@ import {
   generateRequestId,
   generateSessionId,
   generateProjectId,
-  cleanJSONSchemaForAntigravity
+  cleanJSONSchemaForAntigravity,
+  normalizeGeminiContents
 } from "../formats/gemini.js";
 import { deriveSessionId, toNumericSessionId } from "../../utils/sessionManager.js";
 import { ROLE, GEMINI_ROLE, OPENAI_BLOCK, CLAUDE_BLOCK } from "../schema/index.js";
@@ -35,17 +36,6 @@ function sanitizeGeminiFunctionName(name) {
   return sanitized.substring(0, 64);
 }
 
-function normalizeGeminiContents(contents) {
-  const out = [];
-  for (const c of contents || []) {
-    if (!c?.role || !Array.isArray(c.parts) || c.parts.length === 0) continue;
-    const last = out.at(-1);
-    if (last?.role === c.role) last.parts.push(...c.parts);
-    else out.push({ ...c, parts: [...c.parts] });
-  }
-  return out;
-}
-
 // Core: Convert OpenAI request to Gemini format (base for all variants)
 function openaiToGeminiBase(model, body, stream, signature = DEFAULT_THINKING_AG_SIGNATURE, sessionId = null) {
   const result = {
@@ -163,12 +153,14 @@ function openaiToGeminiBase(model, body, stream, signature = DEFAULT_THINKING_AG
           }
 
           // Check if there are actual tool responses in the next messages
-          const hasActualResponses = toolCallIds.some(fid => toolResponses[fid]);
+          const isIntermediate = i < body.messages.length - 1;
+          const hasActualResponses = toolCallIds.some(fid => toolResponses[fid] !== undefined);
 
-          if (hasActualResponses) {
+          if (hasActualResponses || isIntermediate) {
             const toolParts = [];
             for (const fid of toolCallIds) {
-              if (!toolResponses[fid]) continue;
+              let resp = toolResponses[fid];
+              if (resp === undefined) resp = "";
 
               let name = tcID2Name[fid];
               if (!name) {
@@ -180,7 +172,6 @@ function openaiToGeminiBase(model, body, stream, signature = DEFAULT_THINKING_AG
                 }
               }
 
-              let resp = toolResponses[fid];
               let parsedResp = tryParseJSON(resp);
               if (parsedResp === null) {
                 parsedResp = { result: resp };