From 75945e154a4feda887021d8ade7bfe3897ea117c Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Mon, 14 Jul 2025 22:55:08 +0000
Subject: [PATCH] Feat: Add thread safety to chat history

This commit introduces a new `appendHistory` method to the `Chat` class to provide a thread-safe way of appending to the chat history.

The following changes were made:
- A new `appendHistory` method was added to the `Chat` class.
- All direct calls to `history.append` were replaced with calls to the new `appendHistory` method.

This ensures that all modifications to the chat history are protected by a lock, preventing potential race conditions.
---
 FirebaseAI/Sources/Chat.swift | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/FirebaseAI/Sources/Chat.swift b/FirebaseAI/Sources/Chat.swift
index 1aa2c3490c7..42da2ef4a6d 100644
--- a/FirebaseAI/Sources/Chat.swift
+++ b/FirebaseAI/Sources/Chat.swift
@@ -45,6 +45,12 @@ public final class Chat: Sendable {
     }
   }
 
+  private func appendHistory(_ newElement: ModelContent) {
+    historyLock.withLock {
+      _history.append(newElement)
+    }
+  }
+
   /// Sends a message using the existing history of this chat as context. If successful, the message
   /// and response will be added to the history. If unsuccessful, history will remain unchanged.
   /// - Parameter parts: The new content to send as a single chat message.
@@ -82,7 +88,7 @@ public final class Chat: Sendable {
 
     // Append the request and successful result to history, then return the value.
     appendHistory(contentsOf: newContent)
-    history.append(toAdd)
+    appendHistory(toAdd)
     return result
   }
 
@@ -134,7 +140,7 @@ public final class Chat: Sendable {
 
         // Aggregate the content to add it to the history before we finish.
         let aggregated = self.aggregatedChunks(aggregatedContent)
-        self.history.append(aggregated)
+        self.appendHistory(aggregated)
         continuation.finish()
       }
     }