diff --git a/aider/coder.py b/aider/coder.py
index bf2e1164c..dd43f392d 100755
--- a/aider/coder.py
+++ b/aider/coder.py
@@ -10,7 +10,6 @@ from rich.console import Console
 from rich.live import Live
 from rich.markdown import Markdown
 from pathlib import Path
-import tiktoken
 
 import git
 import openai
@@ -19,7 +18,7 @@ import openai
 from aider import utils
 from aider import prompts
 from aider.commands import Commands
-from aider.ctags import get_tags_map
+from aider.ctags import RepoMap
 
 openai.api_key = os.getenv("OPENAI_API_KEY")
 
@@ -43,7 +42,6 @@ class Coder:
         verbose=False,
     ):
         self.verbose = verbose
-        self.use_ctags = use_ctags
         self.abs_fnames = set()
         self.cur_messages = []
         self.done_messages = []
@@ -75,7 +73,8 @@ class Coder:
 
         self.pretty = pretty
         self.show_diffs = show_diffs
-        self.tokenizer = tiktoken.encoding_for_model(self.main_model)
+
+        self.repo_map = RepoMap(use_ctags, self.root, self.main_model)
 
     def find_common_root(self):
         if self.abs_fnames:
@@ -172,7 +171,7 @@ class Coder:
             all_content += files_content
 
         other_files = set(self.get_all_abs_files()) - set(self.abs_fnames)
-        repo_content = self.get_repo_map(self.abs_fnames, other_files)
+        repo_content = self.repo_map.get_repo_map(self.abs_fnames, other_files)
         if repo_content:
             if all_content:
                 all_content += "\n"
@@ -189,51 +188,6 @@ class Coder:
 
         return files_messages
 
-    def get_repo_map(self, chat_files, other_files):
-        res = self.choose_files_listing(other_files)
-        if not res:
-            return
-
-        files_listing, ctags_msg = res
-
-        if chat_files:
-            other = "other "
-        else:
-            other = ""
-
-        repo_content = prompts.repo_content_prefix.format(
-            other=other,
-            ctags_msg=ctags_msg,
-        )
-        repo_content += files_listing
-
-        return repo_content
-
-    def choose_files_listing(self, other_files):
-        # 1/4 of gpt-4's context window
-        max_map_tokens = 2048
-
-        if not other_files:
-            return
-
-        if self.use_ctags:
-            files_listing = get_tags_map(other_files)
-            if self.token_count(files_listing) < max_map_tokens:
-                ctags_msg = " with selected ctags info"
-                return files_listing, ctags_msg
-
-        files_listing = self.get_simple_files_map(other_files)
-        ctags_msg = ""
-        if self.token_count(files_listing) < max_map_tokens:
-            return files_listing, ctags_msg
-
-    def get_simple_files_map(self, other_files):
-        files_listing = "\n".join(self.get_rel_fname(ofn) for ofn in sorted(other_files))
-        return files_listing
-
-    def token_count(self, string):
-        return len(self.tokenizer.encode(string))
-
     def run(self):
         self.done_messages = []
         self.cur_messages = []
diff --git a/aider/ctags.py b/aider/ctags.py
index 983bbd11e..30de11320 100644
--- a/aider/ctags.py
+++ b/aider/ctags.py
@@ -2,6 +2,9 @@ import os
 import json
 import sys
 import subprocess
+import tiktoken
+
+from aider import prompts
 
 # Global cache for tags
 TAGS_CACHE = {}
@@ -91,6 +94,63 @@ def get_tags(filename, root_dname):
     return tags
 
 
+class RepoMap:
+    use_ctags = False
+
+    def __init__(self, use_ctags, root, main_model):
+        self.use_ctags = use_ctags
+        self.tokenizer = tiktoken.encoding_for_model(main_model)
+        self.root = root
+
+    def get_repo_map(self, chat_files, other_files):
+        res = self.choose_files_listing(other_files)
+        if not res:
+            return
+
+        files_listing, ctags_msg = res
+
+        if chat_files:
+            other = "other "
+        else:
+            other = ""
+
+        repo_content = prompts.repo_content_prefix.format(
+            other=other,
+            ctags_msg=ctags_msg,
+        )
+        repo_content += files_listing
+
+        return repo_content
+
+    def choose_files_listing(self, other_files):
+        # 1/4 of gpt-4's context window
+        max_map_tokens = 2048
+
+        if not other_files:
+            return
+
+        if self.use_ctags:
+            files_listing = get_tags_map(other_files)
+            if self.token_count(files_listing) < max_map_tokens:
+                ctags_msg = " with selected ctags info"
+                return files_listing, ctags_msg
+
+        files_listing = self.get_simple_files_map(other_files)
+        ctags_msg = ""
+        if self.token_count(files_listing) < max_map_tokens:
+            return files_listing, ctags_msg
+
+    def get_simple_files_map(self, other_files):
+        files_listing = "\n".join(self.get_rel_fname(ofn) for ofn in sorted(other_files))
+        return files_listing
+
+    def token_count(self, string):
+        return len(self.tokenizer.encode(string))
+
+    def get_rel_fname(self, fname):
+        return os.path.relpath(fname, self.root)
+
+
 if __name__ == "__main__":
     res = get_tags_map(sys.argv[1:])
     print(res)