diff --git a/aider/coders/editblock_coder.py b/aider/coders/editblock_coder.py
index cfb9ba16c..ef8115d11 100644
--- a/aider/coders/editblock_coder.py
+++ b/aider/coders/editblock_coder.py
@@ -31,10 +31,10 @@ class EditBlockCoder(Coder):
                 continue
             raise ValueError(f"""InvalidEditBlock: edit failed!
 
-{path} does not contain the *exact sequence* of HEAD lines you specified.
+{path} does not contain the *exact chunk* of SEARCH lines you specified.
 Try again.
 DO NOT skip blank lines, comments, docstrings, etc!
-The HEAD block needs to be EXACTLY the same as the lines in {path} with nothing missing!
+The SEARCH block needs to be EXACTLY the same as the lines in {path} with nothing missing!
 
 {path} does not contain these {len(original.splitlines())} exact lines in a row:
 ```
@@ -122,7 +122,7 @@ def try_dotdotdots(whole, part, replace):
     replace_pieces = re.split(dots_re, replace)
 
     if len(part_pieces) != len(replace_pieces):
-        raise ValueError("Unpaired ... in edit block")
+        raise ValueError("Unpaired ... in SEARCH/REPLACE block")
 
     if len(part_pieces) == 1:
         # no dots in this edit block, just return None
@@ -132,7 +132,7 @@ def try_dotdotdots(whole, part, replace):
     all_dots_match = all(part_pieces[i] == replace_pieces[i] for i in range(1, len(part_pieces), 2))
 
     if not all_dots_match:
-        raise ValueError("Unmatched ... in edit block")
+        raise ValueError("Unmatched ... in SEARCH/REPLACE block")
 
     part_pieces = [part_pieces[i] for i in range(0, len(part_pieces), 2)]
     replace_pieces = [replace_pieces[i] for i in range(0, len(replace_pieces), 2)]
@@ -148,10 +148,10 @@ def try_dotdotdots(whole, part, replace):
             whole += replace
             continue
 
-        if whole.count(part) != 1:
-            raise ValueError(
-                "No perfect matching chunk in edit block with ... or part appears more than once"
-            )
+        if whole.count(part) == 0:
+            raise ValueError
+        if whole.count(part) > 1:
+            raise ValueError
 
         whole = whole.replace(part, replace, 1)
 
@@ -301,9 +301,9 @@ def do_replace(fname, content, before_text, after_text, fence=None):
     return new_content
 
 
-HEAD = "<<<<<<< HEAD"
+HEAD = "<<<<<<< SEARCH"
 DIVIDER = "======="
-UPDATED = ">>>>>>> updated"
+UPDATED = ">>>>>>> REPLACE"
 
 separators = "|".join([HEAD, DIVIDER, UPDATED])
 
@@ -379,10 +379,10 @@ def find_original_update_blocks(content):
         raise ValueError(f"{processed}\n^^^ {err}")
     except IndexError:
         processed = "".join(processed)
-        raise ValueError(f"{processed}\n^^^ Incomplete HEAD/updated block.")
+        raise ValueError(f"{processed}\n^^^ Incomplete SEARCH/REPLACE block.")
     except Exception:
         processed = "".join(processed)
-        raise ValueError(f"{processed}\n^^^ Error parsing HEAD/updated block.")
+        raise ValueError(f"{processed}\n^^^ Error parsing SEARCH/REPLACE block.")
 
 
 if __name__ == "__main__":
diff --git a/aider/coders/editblock_prompts.py b/aider/coders/editblock_prompts.py
index bd193eeb4..5a1ed02f6 100644
--- a/aider/coders/editblock_prompts.py
+++ b/aider/coders/editblock_prompts.py
@@ -14,40 +14,38 @@ If the request is ambiguous, ask questions.
 Once you understand the request you MUST:
 1. List the files you need to modify. *NEVER* suggest changes to a *read-only* file. Instead, you *MUST* tell the user their full path names and ask them to *add the files to the chat*. End your reply and wait for their approval.
 2. Think step-by-step and explain the needed changes.
-3. Describe each change with an *edit block* per the example below.
+3. Describe each change with a *SEARCH/REPLACE block* per the example below.
 """
 
-    system_reminder = """You MUST format EVERY code change with an *edit block* like this:
+    system_reminder = """You MUST use a *SEARCH/REPLACE block* to modify the source file:
 
 {fence[0]}python
 some/dir/example.py
-<<<<<<< HEAD
-    # some comment
-    # Func to multiply
-    def mul(a,b)
+<<<<<<< SEARCH
+    # Multiplication function
+    def multiply(a,b)
+        "multiply 2 numbers"
+
+        return a*b
 =======
-    # updated comment
-    # Function to add
+    # Addition function
     def add(a,b):
->>>>>>> updated
+        "add 2 numbers"
+
+        return a+b
+>>>>>>> REPLACE
 {fence[1]}
 
-A program will parse the edit blocks you generate and replace the `HEAD` lines with the `updated` lines.
-So edit blocks must be precise and unambiguous!
+The *SEARCH* section must *EXACTLY MATCH* the existing source code, character for character.
 
-Every *edit block* must be fenced with {fence[0]}...{fence[1]} with the correct code language.
-Every *edit block* must start with the full path! *NEVER* propose edit blocks for *read-only* files.
+Every *SEARCH/REPLACE block* must be fenced with {fence[0]} and {fence[1]}, with the correct code language.
 
-The `HEAD` section must be an *exact set of sequential lines* from the file!
-NEVER SKIP LINES in the `HEAD` section!
-NEVER ELIDE LINES AND REPLACE THEM WITH A COMMENT!
-NEVER OMIT ANY WHITESPACE in the `HEAD` section!
+Every *SEARCH/REPLACE block* must start with the full path!
+NEVER try to *SEARCH/REPLACE* any *read-only* files.
 
-Edits to different parts of a file each need their own *edit block*, including the full path.
-
-If you want to put code in a new file, use an edit block with:
+If you want to put code in a new file, use a *SEARCH/REPLACE block* with:
 - A new file path, including dir name if needed
-- An empty `HEAD` section
+- An empty `SEARCH` section
 - The new file's contents in the `updated` section
 """