fix(google): repair Cloud Code Assist tool-call ordering (#406)

src/agents/pi-embedded-helpers.ts

@@ -104,6 +104,36 @@ export async function sanitizeSessionMessagesImages(
   return out;
 }
 
+const GOOGLE_TURN_ORDER_BOOTSTRAP_TEXT = "(session bootstrap)";
+
+export function sanitizeGoogleTurnOrdering(
+  messages: AgentMessage[],
+): AgentMessage[] {
+  const first = messages[0] as
+    | { role?: unknown; content?: unknown }
+    | undefined;
+  const role = first?.role;
+  const content = first?.content;
+  if (
+    role === "user" &&
+    typeof content === "string" &&
+    content.trim() === GOOGLE_TURN_ORDER_BOOTSTRAP_TEXT
+  ) {
+    return messages;
+  }
+  if (role !== "assistant") return messages;
+
+  // Cloud Code Assist rejects histories that begin with a model turn (tool call or text).
+  // Prepend a tiny synthetic user turn so the rest of the transcript can be used.
+  const bootstrap: AgentMessage = {
+    role: "user",
+    content: GOOGLE_TURN_ORDER_BOOTSTRAP_TEXT,
+    timestamp: Date.now(),
+  } as AgentMessage;
+
+  return [bootstrap, ...messages];
+}
+
 export function buildBootstrapContextFiles(
   files: WorkspaceBootstrapFile[],
 ): EmbeddedContextFile[] {