reflex-dev/reflex · error · FileNotFoundError

Plugin is trying to modify but it does not exist.

Error message

Plugin {plugin_name} is trying to modify {path} but it does not exist.

What it means

During the plugin output-modification phase of compile_app, a plugin's modify hook targets a file path that is neither in the compiled output mapping nor present on disk, so there is no content to modify. Reflex raises FileNotFoundError naming the plugin and path.

Solutions

Verify the exact path against compiled output in the .web directory and fix the plugin's path constant
Make the plugin's modify hook tolerant: check path.exists()/output_mapping before returning a modify_fn
Pin or update the plugin to a version compatible with your Reflex version

Defensive patterns

Strategy: validation

Validate before calling

from pathlib import Path

def safe_modify_path(path: Path, output_mapping: dict) -> bool:
    return path in output_mapping or path.exists()

Try / catch

try:
    compile_app(app)
except FileNotFoundError as e:
    if "trying to modify" in str(e):
        # fix plugin path or skip plugin
        ...
    raise

Prevention

Verify plugin target paths against .web output after upgrades
Make plugin modify hooks no-op when the target file is absent
Pin plugin and Reflex versions together and test compiles in CI

When it happens

Trigger: A plugin's get_modified_outputs / output modification hook returns a modify_fn for a path that was never emitted by compilation (typo'd path, wrong extension like .jsx vs .tsx, or a file only produced under other config) and that doesn't exist on disk.

Common situations: Custom or third-party Reflex plugins referencing output files with incorrect paths; Reflex upgrades changing emitted filenames while the plugin wasn't updated; plugins targeting files emitted only when certain features (e.g. radix themes) are enabled.

Related errors

AI-assisted analysis of reflex-dev/reflex@45b8ed5ab7 (2026-08-28). Data as JSON: /api/errors/780789a73e9e136a. Report an issue: GitHub.

Appendix: source

Thrown at reflex/compiler/compiler.py:1461

        for static_file_path, content in plugin.get_static_assets():
            path = utils.resolve_path_of_web_dir(static_file_path)
            if path in output_mapping:
                logger.warning(
                    f"Plugin {plugin.__class__.__name__} is overwriting existing files at {path}."
                )
            output_mapping[path] = (
                content.decode("utf-8") if isinstance(content, bytes) else content
            )

    for plugin_name, file_path, modify_fn in modify_files_tasks:
        path = utils.resolve_path_of_web_dir(file_path)
        file_content = output_mapping.get(path)
        if file_content is None:
            if path.exists():
                file_content = path.read_text()
            else:
                msg = f"Plugin {plugin_name} is trying to modify {path} but it does not exist."
                raise FileNotFoundError(msg)
        output_mapping[path] = modify_fn(file_content)

    with log.timing(logger, "Write to Disk"):
        for output_path, code in output_mapping.items():
            utils.write_file(output_path, code)

    return True

View on GitHub (pinned to 45b8ed5ab7)