diff --git a/aider/utils.py b/aider/utils.py
index c1bf9ca5f..ccd5fc334 100644
--- a/aider/utils.py
+++ b/aider/utils.py
@@ -258,40 +258,27 @@ class Spinner:
         self.visible = False
         self.is_tty = sys.stdout.isatty()
 
-        # --------------------------------------------------------------
-        # Spinner configuration
-        # --------------------------------------------------------------
-        # Logical width of the animation area inside the brackets
-        self.scanner_width = 7
+        self.scanner_width = 7  # Width of the scanning area (e.g., 7 for "[---■--]")
         self.scanner_pos = 0
-        self.scanner_dir = 1 if self.scanner_width > 1 else 0  # 1 → right, -1 → left
+        self.scanner_dir = 1 if self.scanner_width > 1 else 0  # Direction of scanner movement
 
-        # Character palette – will be upgraded to Unicode if possible
-        self.scanner_head_char = "#"   # One char per head position
-        self.trail_active_char = "="   # Recently-visited positions
-        self.trail_empty_char = "-"    # Background
-
-        # Visual lengths (number of logical positions)
-        self.scanner_head_length = 2   # "≡≡"
-        self.trail_active_length = 2   # "══"
-
-        # Upgrade to Unicode glyphs when the terminal supports them
+        # Attempt to use Unicode characters for the scanner, fallback to ASCII
+        self.scanner_char = "#"  # ASCII fallback
+        self.trail_char = "-"  # ASCII fallback
         if self.is_tty:
             try:
-                sys.stdout.write("≡═─")
+                # Test print Unicode chars and erase them to check encoding support
+                sys.stdout.write("■─")
                 sys.stdout.flush()
-                sys.stdout.write("\b\b\b   \b\b\b")
+                sys.stdout.write("\b\b  \b\b")  # Backspace, write spaces, backspace
                 sys.stdout.flush()
-                self.scanner_head_char = "≡"
-                self.trail_active_char = "═"
-                self.trail_empty_char = "─"
+                self.scanner_char = "≡"  # Unicode
+                self.trail_char = "─"  # Unicode
             except UnicodeEncodeError:
+                pass  # Stick to ASCII fallbacks
+            except Exception:  # Catch other potential IO errors on strange terminals
                 pass
-            except Exception:
-                pass
-
-        # Cached length of the animation segment (inside the [])
-        self.animation_len = self.scanner_width + 2
+        self.animation_len = self.scanner_width + 2  # For brackets like "[]"
 
     def step(self):
         if not self.is_tty:
@@ -309,42 +296,45 @@ class Spinner:
         if not self.visible:
             return
 
-        # Start with an empty frame
-        frame_chars = [self.trail_empty_char] * self.scanner_width
+        frame_chars = [self.trail_char] * self.scanner_width
+        # Ensure scanner_pos is within bounds for frame assignment
+        current_pos_in_frame = max(0, min(self.scanner_pos, self.scanner_width - 1))
 
-        # Place the 2-character head
-        head_start = max(0, min(self.scanner_pos, self.scanner_width - self.scanner_head_length))
-        head_end = head_start + self.scanner_head_length - 1
-        for i in range(self.scanner_head_length):
-            pos = head_start + i
-            if 0 <= pos < self.scanner_width:
-                frame_chars[pos] = self.scanner_head_char
+        if self.scanner_width > 0:  # Only place char if width is positive
+            frame_chars[current_pos_in_frame] = self.scanner_char
 
-        # Add the active trail directly behind the head
-        for i in range(1, self.trail_active_length + 1):
-            if self.scanner_dir > 0:          # moving right → trail to the left
-                pos = head_start - i
-            else:                             # moving left  → trail to the right
-                pos = head_end + i
-            if 0 <= pos < self.scanner_width and frame_chars[pos] == self.trail_empty_char:
-                frame_chars[pos] = self.trail_active_char
-
-        animation_content = "".join(frame_chars)
-        animation_segment = f"[{animation_content}]"
+        animation_content = "".join(frame_chars)  # Content inside brackets, e.g., "---■--"
+        animation_segment = f"[{animation_content}]"  # Full animation part, e.g., "[---■--]"
 
+        # Print the entire line to display it
         full_line_output = f"\r{self.text} {animation_segment}"
         sys.stdout.write(full_line_output)
-        sys.stdout.flush()
 
-        # Advance for next frame
-        if self.scanner_width > self.scanner_head_length:
+        # Now, calculate backspaces to position cursor on the scanner_char
+        # Only if scanner_char was actually placed (i.e., scanner_width > 0)
+        if self.scanner_width > 0:
+            # Number of characters in animation_content *after* the scanner_char
+            # (self.scanner_width - 1) is the last index of animation_content.
+            # So, (self.scanner_width - 1) - current_pos_in_frame gives count of chars after.
+            chars_in_content_after_scanner = (self.scanner_width - 1) - current_pos_in_frame
+
+            # We also need to backspace over the closing bracket ']'
+            num_backspaces = chars_in_content_after_scanner + 1
+
+            num_backspaces = max(0, num_backspaces) + 1  # Ensure not negative
+            sys.stdout.write("\b" * num_backspaces)
+
+        sys.stdout.flush()  # Flush after all writes for this frame
+
+        # Update scanner position for the next frame
+        if self.scanner_width > 1:
             self.scanner_pos += self.scanner_dir
-            if self.scanner_dir > 0 and self.scanner_pos >= self.scanner_width - self.scanner_head_length:
-                self.scanner_pos = self.scanner_width - self.scanner_head_length
-                self.scanner_dir = -1
-            elif self.scanner_dir < 0 and self.scanner_pos <= 0:
-                self.scanner_pos = 0
-                self.scanner_dir = 1
+            if self.scanner_pos >= self.scanner_width - 1:  # Reached or passed the end
+                self.scanner_pos = self.scanner_width - 1  # Pin to end
+                self.scanner_dir = -1  # Reverse direction
+            elif self.scanner_pos <= 0:  # Reached or passed the beginning
+                self.scanner_pos = 0  # Pin to start
+                self.scanner_dir = 1  # Reverse direction
 
     def end(self):
         if self.visible and self.is_tty: