fix(sse): strip Gemini built-in tools when functionDeclarations present in Antigravity envelope (#4821)

Integrated into release/v3.8.37 — cherry-picked defining commit onto release tip; CHANGELOG re-merged; tests green.

tests/unit/antigravity-strip-builtin-tools-funcdecls-1095.test.ts

@@ -0,0 +1,102 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+import { openaiToAntigravityRequest } from "../../open-sse/translator/request/openai-to-gemini.ts";
+
+// Regression guard for the Antigravity v1internal 400 that fires when a Gemini
+// built-in tool (google_search / web_search / googleSearch ...) is sent in the
+// same request as functionDeclarations. The Cloud Code envelope must strip the
+// built-in tool names out of functionDeclarations before dispatch.
+// Inspired-by decolua/9router#1095 (author @vanszs).
+
+type EnvelopeTool = { functionDeclarations?: Array<{ name: string }> };
+
+function declaredToolNames(result: { request: { tools?: EnvelopeTool[] } }): string[] {
+  return (result.request.tools ?? []).flatMap((tool) =>
+    (tool.functionDeclarations ?? []).map((fn) => fn.name)
+  );
+}
+
+const CREDS = { projectId: "proj-1" } as never;
+
+test("Antigravity envelope strips built-in tool names mixed with custom functionDeclarations (#1095)", () => {
+  const result = openaiToAntigravityRequest(
+    "gemini-2.5-pro",
+    {
+      messages: [{ role: "user", content: "Search and read" }],
+      tools: [
+        {
+          type: "function",
+          function: { name: "google_search", parameters: { type: "object", properties: {} } },
+        },
+        {
+          type: "function",
+          function: { name: "read_file", parameters: { type: "object", properties: {} } },
+        },
+      ],
+    },
+    false,
+    CREDS
+  );
+
+  const names = declaredToolNames(result);
+  // Built-in tool name must be gone from functionDeclarations...
+  assert.ok(
+    !names.includes("google_search") && !names.includes("googleSearch"),
+    `expected built-in tool name stripped, got ${JSON.stringify(names)}`
+  );
+  // ...while the custom declaration survives.
+  assert.ok(names.includes("read_file"), `expected custom tool kept, got ${JSON.stringify(names)}`);
+  // toolConfig stays set because custom declarations remain.
+  assert.deepEqual(result.request.toolConfig, {
+    functionCallingConfig: { mode: "VALIDATED" },
+  });
+});
+
+test("Antigravity envelope keeps a normal custom-only tool request intact (#1095 regression)", () => {
+  const result = openaiToAntigravityRequest(
+    "gemini-2.5-pro",
+    {
+      messages: [{ role: "user", content: "Hello" }],
+      tools: [
+        {
+          type: "function",
+          function: { name: "weather", parameters: { type: "object", properties: {} } },
+        },
+      ],
+    },
+    false,
+    CREDS
+  );
+
+  const names = declaredToolNames(result);
+  assert.deepEqual(names, ["weather"]);
+  assert.deepEqual(result.request.toolConfig, {
+    functionCallingConfig: { mode: "VALIDATED" },
+  });
+});
+
+test("Antigravity envelope drops tools + toolConfig when only built-in tools are present (#1095)", () => {
+  const result = openaiToAntigravityRequest(
+    "gemini-2.5-pro",
+    {
+      messages: [{ role: "user", content: "Search the web" }],
+      tools: [
+        {
+          type: "function",
+          function: { name: "google_search", parameters: { type: "object", properties: {} } },
+        },
+      ],
+    },
+    false,
+    CREDS
+  );
+
+  const names = declaredToolNames(result);
+  assert.ok(
+    !names.includes("google_search") && !names.includes("googleSearch"),
+    `expected no built-in functionDeclarations, got ${JSON.stringify(names)}`
+  );
+  // No custom declarations remain -> no VALIDATED toolConfig is forced.
+  assert.equal(result.request.toolConfig, undefined);
+});