diff --git a/aider/coders/editblock_coder.py b/aider/coders/editblock_coder.py
index ffbcfc644..a8762846b 100644
--- a/aider/coders/editblock_coder.py
+++ b/aider/coders/editblock_coder.py
@@ -365,9 +365,13 @@ def do_replace(fname, content, before_text, after_text, fence=None):
     return new_content
 
 
-HEAD = "<<<<<<< SEARCH"
-DIVIDER = "======="
-UPDATED = ">>>>>>> REPLACE"
+HEAD = r"<{5,9} SEARCH"
+DIVIDER = r"={5,9}"
+UPDATED = r">{5,9} REPLACE"
+
+HEAD_ERR = "<<<<<<< SEARCH"
+DIVIDER_ERR = "======="
+UPDATED_ERR = ">>>>>>> REPLACE"
 
 separators = "|".join([HEAD, DIVIDER, UPDATED])
 
@@ -407,6 +411,10 @@ def find_original_update_blocks(content, fence=DEFAULT_FENCE, valid_fnames=None)
     i = 0
     current_filename = None
 
+    head_pattern = re.compile(HEAD)
+    divider_pattern = re.compile(DIVIDER)
+    updated_pattern = re.compile(UPDATED)
+
     while i < len(lines):
         line = lines[i]
 
@@ -425,7 +433,7 @@ def find_original_update_blocks(content, fence=DEFAULT_FENCE, valid_fnames=None)
             "```csh",
             "```tcsh",
         ]
-        next_is_editblock = i + 1 < len(lines) and lines[i + 1].rstrip() == HEAD
+        next_is_editblock = i + 1 < len(lines) and head_pattern.match(lines[i + 1].strip())
 
         if any(line.strip().startswith(start) for start in shell_starts) and not next_is_editblock:
             shell_content = []
@@ -440,10 +448,10 @@ def find_original_update_blocks(content, fence=DEFAULT_FENCE, valid_fnames=None)
             continue
 
         # Check for SEARCH/REPLACE blocks
-        if line.strip() == HEAD:
+        if head_pattern.match(line.strip()):
             try:
                 # if next line after HEAD exists and is DIVIDER, it's a new file
-                if i + 1 < len(lines) and lines[i + 1].strip() == DIVIDER:
+                if i + 1 < len(lines) and divider_pattern.match(lines[i + 1].strip()):
                     filename = find_filename(lines[max(0, i - 3) : i], fence, None)
                 else:
                     filename = find_filename(
@@ -460,21 +468,21 @@ def find_original_update_blocks(content, fence=DEFAULT_FENCE, valid_fnames=None)
 
                 original_text = []
                 i += 1
-                while i < len(lines) and not lines[i].strip() == DIVIDER:
+                while i < len(lines) and not divider_pattern.match(lines[i].strip()):
                     original_text.append(lines[i])
                     i += 1
 
-                if i >= len(lines) or lines[i].strip() != DIVIDER:
-                    raise ValueError(f"Expected `{DIVIDER}`")
+                if i >= len(lines) or not divider_pattern.match(lines[i].strip()):
+                    raise ValueError(f"Expected `{DIVIDER_ERR}`")
 
                 updated_text = []
                 i += 1
-                while i < len(lines) and not lines[i].strip() in (UPDATED, DIVIDER):
+                while i < len(lines) and not (updated_pattern.match(lines[i].strip()) or divider_pattern.match(lines[i].strip())):
                     updated_text.append(lines[i])
                     i += 1
 
-                if i >= len(lines) or lines[i].strip() not in (UPDATED, DIVIDER):
-                    raise ValueError(f"Expected `{UPDATED}` or `{DIVIDER}`")
+                if i >= len(lines) or not (updated_pattern.match(lines[i].strip()) or divider_pattern.match(lines[i].strip())):
+                    raise ValueError(f"Expected `{UPDATED_ERR}` or `{DIVIDER_ERR}`")
 
                 yield filename, "".join(original_text), "".join(updated_text)