diff --git a/aider/coders/editblock_coder.py b/aider/coders/editblock_coder.py
index 557e692b6..28331edf0 100644
--- a/aider/coders/editblock_coder.py
+++ b/aider/coders/editblock_coder.py
@@ -1,8 +1,12 @@
+import difflib
 import math
 import re
+import sys
 from difflib import SequenceMatcher
 from pathlib import Path
 
+from aider import utils
+
 from ..dump import dump  # noqa: F401
 from .base_coder import Coder
 from .editblock_prompts import EditBlockPrompts
@@ -481,24 +485,6 @@ def find_filename(lines, fence):
             return
 
 
-if __name__ == "__main__":
-    edit = """
-Here's the change:
-
-```text
-foo.txt
-<<<<<<< HEAD
-Two
-=======
-Tooooo
->>>>>>> updated
-```
-
-Hope you like it!
-"""
-    print(list(find_original_update_blocks(edit)))
-
-
 def find_similar_lines(search_lines, content_lines, threshold=0.6):
     search_lines = search_lines.splitlines()
     content_lines = content_lines.splitlines()
@@ -526,3 +512,32 @@ def find_similar_lines(search_lines, content_lines, threshold=0.6):
 
     best = content_lines[best_match_i:best_match_end]
     return "\n".join(best)
+
+
+def main():
+    history_md = Path(sys.argv[1]).read_text()
+    if not history_md:
+        return
+
+    messages = utils.split_chat_history_markdown(history_md)
+
+    for msg in messages:
+        msg = msg["content"]
+        edits = list(find_original_update_blocks(msg))
+
+        for fname, before, after in edits:
+            # Compute diff
+            diff = difflib.unified_diff(
+                before.splitlines(keepends=True),
+                after.splitlines(keepends=True),
+                fromfile="before",
+                tofile="after",
+            )
+            diff = "".join(diff)
+            dump(before)
+            dump(after)
+            dump(diff)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/aider/coders/editblock_prompts.py b/aider/coders/editblock_prompts.py
index 44e44df92..8e94b0312 100644
--- a/aider/coders/editblock_prompts.py
+++ b/aider/coders/editblock_prompts.py
@@ -124,8 +124,12 @@ Every *SEARCH/REPLACE block* must use this format:
 
 Every *SEARCH* section must *EXACTLY MATCH* the existing source code, character for character, including all comments, docstrings, etc.
 
+
 *SEARCH/REPLACE* blocks will replace *all* matching occurrences.
-Include enough lines to make the SEARCH blocks unique.
+Include enough lines to make the SEARCH blocks uniquely match the lines to change.
+
+Keep *SEARCH/REPLACE* blocks concise.
+Include just the changing lines, and a few surrounding lines if needed for uniqueness.
 
 Include *ALL* the code being searched and replaced!