Aider-AI/aider · error · DiffError

Update File action missing path.

Error message

Update File action missing path.

What it means

Raised by PatchCoder._parse_patch_text when a '*** Update File:' header line has nothing after the colon — the update action has no target path, so there is nothing to attach the subsequent hunks to.

Source

Thrown at aider/coders/patch_coder.py:314

        """
        patch = Patch()
        index = start_index
        fuzz_accumulator = 0

        while index < len(lines):
            line = lines[index]
            norm_line = _norm(line)

            if norm_line == "*** End Patch":
                index += 1
                break  # Successfully reached end

            # ---------- UPDATE ---------- #
            if norm_line.startswith("*** Update File: "):
                path = norm_line[len("*** Update File: ") :].strip()
                index += 1
                if not path:
                    raise DiffError("Update File action missing path.")

                # Optional move target
                move_to = None
                if index < len(lines) and _norm(lines[index]).startswith("*** Move to: "):
                    move_to = _norm(lines[index])[len("*** Move to: ") :].strip()
                    index += 1
                    if not move_to:
                        raise DiffError("Move to action missing path.")

                if path not in current_files:
                    raise DiffError(f"Update File Error - missing file content for: {path}")

                file_content = current_files[path]

                existing_action = patch.actions.get(path)
                if existing_action is not None:
                    # Merge additional UPDATE block into the existing one
                    if existing_action.type != ActionType.UPDATE:

View on GitHub (pinned to 5dc9490bb3)

Solutions

1. Complete the header: '*** Update File: relative/path/to/file.py'.
2. Check the reply for truncation and re-request the patch if output was cut off.
3. Retry with the error fed back to the model so it fills in the path.
4. If the intent was a new file, use '*** Add File: path' with full content instead.

Example fix

# before
*** Update File:
@@
-a
+b
*** End Patch

# after
*** Update File: foo.py
@@
-a
+b
*** End Patch

import re

def headerless_update_paths(patch_text: str) -> list[str]:
    return [l for l in patch_text.splitlines() if re.fullmatch(r"\*\*\* Update File:\s*", l)]
# non-empty → these headers lack paths; fill them in before get_edits()

try:
    coder.get_edits(patch_text)
except ValueError as e:
    if "Update File action missing path" in str(e):
        patch_text = fill_in_missing_paths(patch_text)  # or re-ask the model
        coder.get_edits(patch_text)
    else:
        raise

When it happens

Trigger: A patch containing the literal line '*** Update File:' (or '*** Update File: ' with only whitespace, since the path is .strip()ed) — usually a model truncating the header or emitting the template before filling in the filename.

Common situations: Templated/partial LLM output where the path placeholder was never replaced; copy-paste edits dropping the filename; token-limit truncation right after the header.

Related errors

• Update File Error - missing file content for: {path}
• Invalid patch line found in update section: {line}
• Invalid line prefix in update section: {line}
• Empty patch section found.
• File referenced in patch not found or could not be read: {re

AI-assisted analysis of Aider-AI/aider@5dc9490bb3 (2026-08-15). Data as JSON: /api/errors/8abe4317148606df. Report an issue: GitHub.