Aider-AI/aider · error · DiffError

Invalid patch line found in update section: {line}

Error message

Invalid patch line found in update section: {line}

What it means

Raised by PatchCoder's update-section parser: while collecting patch body lines it encountered a line beginning with '***' that is not one of the recognized markers ('@@', '*** End Patch', '*** Update File:', '*** Delete File:', '*** Add File:', '*** End of File'). Inside an update body, '***' is reserved for structural markers only.

Source

Thrown at aider/coders/patch_coder.py:127

        line = lines[index]
        norm_line = _norm(line)

        # Check for section terminators
        if norm_line.startswith(
            (
                "@@",
                "*** End Patch",
                "*** Update File:",
                "*** Delete File:",
                "*** Add File:",
                "*** End of File",  # Special terminator
            )
        ):
            break
        if norm_line == "***":  # Legacy/alternative terminator? Handle just in case.
            break
        if norm_line.startswith("***"):  # Invalid line
            raise DiffError(f"Invalid patch line found in update section: {line}")

        index += 1
        last_mode = mode

        # Determine line type and strip prefix
        if line.startswith("+"):
            mode = "add"
            line_content = line[1:]
        elif line.startswith("-"):
            mode = "delete"
            line_content = line[1:]
        elif line.startswith(" "):
            mode = "keep"
            line_content = line[1:]
        elif line.strip() == "":  # Treat blank lines in patch as context ' '
            mode = "keep"
            line_content = ""  # Keep it as a blank line
        else:

View on GitHub (pinned to 5dc9490bb3)

Solutions

1. Remove or reword lines starting with '***' inside the update body (e.g. change '*** note' to '# note').
2. Verify marker spelling exactly: '*** Update File: path', '*** End Patch', etc.
3. Send the DiffError back to the model to re-emit a clean patch — PatchCoder.get_edits converts it to ValueError('Error parsing patch content: ...') for that retry loop.
4. If the target file genuinely contains '***'-prefixed lines, keep them as patch body lines with a leading context space (' *** line') so they parse as kept content.

Example fix

# before
*** Update File: foo.py
@@
 context
-*** legacy banner
+new code
*** End Patch

# after
*** Update File: foo.py
@@
 context
- *** legacy banner   (prefix kept-content lines with a space)
+new code
*** End Patch

VALID_MARKERS = ("@@", "*** End Patch", "*** Update File:", "*** Delete File:", "*** Add File:", "*** End of File")

def stray_marker_lines(patch_text: str) -> list[str]:
    return [
        l for l in patch_text.splitlines()
        if l.strip().startswith("***") and l.strip() not in VALID_MARKERS and not l.strip().startswith(tuple(VALID_MARKERS))
    ]  # non-empty → fix these lines before calling get_edits()

try:
    coder.get_edits(patch_text)
except ValueError as e:
    if "Invalid patch line found in update section" in str(e):
        patch_text = reemit_patch_without_stray_markers(str(e))  # ask the model to fix
        coder.get_edits(patch_text)
    else:
        raise

When it happens

Trigger: An LLM emitting a patch (via the 'patch' edit format / apply_patch grammar) whose update section contains a stray '***'-prefixed line — e.g. a C-style comment like '*** note ***', a markdown divider, or a mistyped marker such as '*** Update-File:'.

Common situations: Models mixing apply_patch syntax with unified diff or markdown conventions; comment lines in updated code accidentally starting with '***'; typo'd section headers.

Related errors

• Invalid line prefix in update section: {line}
• Empty patch section found.
• Error parsing patch content: {e}
• Unexpected error parsing patch: {e}
• Update File action missing path.

AI-assisted analysis of Aider-AI/aider@5dc9490bb3 (2026-08-15). Data as JSON: /api/errors/76179c35e8a3981a. Report an issue: GitHub.