diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index 52b274ab7..e64971f47 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -360,7 +360,9 @@ class Coder:
 
     def move_back_cur_messages(self, message):
         self.done_messages += self.cur_messages
-        self.done_messages = self.summarizer.summarize(self.done_messages)
+        if self.summarizer.too_big(self.done_messages):
+            self.io.tool_output("Summarizing chat history...")
+            self.done_messages = self.summarizer.summarize(self.done_messages)
 
         if message:
             self.done_messages += [
diff --git a/aider/history.py b/aider/history.py
index ca45feab8..d342530a7 100644
--- a/aider/history.py
+++ b/aider/history.py
@@ -13,20 +13,27 @@ class ChatSummary:
         self.tokenizer = tiktoken.encoding_for_model(model)
         self.max_tokens = max_tokens
 
+    def too_big(self, messages):
+        sized = self.tokenize(messages)
+        total = sum(tokens for tokens, _msg in sized)
+        dump(total, self.max_tokens)
+        return total > self.max_tokens
+
+    def tokenize(self, messages):
+        sized = []
+        for msg in messages:
+            tokens = len(self.tokenizer.encode(json.dumps(msg)))
+            sized.append((tokens, msg))
+        return sized
+
     def summarize(self, messages):
         num = len(messages)
         dump(num)
         if num < 2:
             return messages
 
-        total = 0
-        sized = []
-        for msg in messages:
-            tokens = len(self.tokenizer.encode(json.dumps(msg)))
-            sized.append((tokens, msg))
-            total += tokens
-
-        dump(total, self.max_tokens)
+        sized = self.tokenize(messages)
+        total = sum(tokens for tokens, _msg in sized)
         if total <= self.max_tokens:
             return messages