What causes "project_files.read_json path must be a file" in nexu-io/open-design?

Point input.path at a specific .json file, not a directory.

project_files.read_json path must be a file

Error message

project_files.read_json path must be a file

What it means

executeProjectFilesReadJson (refresh.ts:597-598) stats the resolved real target and requires it to be a regular file (entryStat.isFile()). A directory, device, socket, or other non-file entry is rejected because the tool can only JSON.parse file contents.

Source

Thrown at apps/daemon/src/live-artifacts/refresh.ts:598

    matches.push(result);
  }

  return asBoundedRefreshOutput({ toolName: 'project_files.search', query: query ?? '', count: matches.length, truncated: allFiles.length > matches.length && matches.length >= maxResults, matches });
}

async function executeProjectFilesReadJson(options: ExecuteLocalDaemonRefreshSourceOptions): Promise<BoundedJsonObject> {
  const filePath = selectJsonPath(options.source.input as ProjectFilesReadJsonInput);
  if (!filePath.endsWith('.json')) throw new Error('project_files.read_json only supports .json files');
  const dir = projectDir(options.projectsRoot, options.projectId);
  const target = path.resolve(dir, filePath);
  const [dirReal, targetLinkStat] = await Promise.all([realpath(dir), lstat(target)]);
  if (targetLinkStat.isSymbolicLink()) throw new Error('project_files.read_json does not follow symlinks');
  const targetReal = await realpath(target);
  if (!targetReal.startsWith(`${dirReal}${path.sep}`) && targetReal !== dirReal) {
    throw new Error('project_files.read_json path escapes project dir');
  }
  const entryStat = await stat(targetReal);
  if (!entryStat.isFile()) throw new Error('project_files.read_json path must be a file');
  if (entryStat.size > 256 * 1024) throw new Error('project_files.read_json file exceeds 256KB');
  if (options.signal?.aborted === true) throw options.signal.reason;
  let parsed: BoundedJsonValue;
  try {
    parsed = JSON.parse(await readFile(targetReal, 'utf8')) as BoundedJsonValue;
  } catch {
    throw new Error(`project_files.read_json could not parse JSON at ${filePath}`);
  }
  return asBoundedRefreshOutput({ toolName: 'project_files.read_json', path: filePath, size: entryStat.size, json: parsed });
}

function compactExecOutput(value: string): string[] {
  return value.split('\n').map((line) => line.trimEnd()).filter(Boolean).slice(0, 100);
}

async function runGit(projectPath: string, args: string[], signal: AbortSignal | undefined): Promise<string> {
  try {
    const result = await execFileAsync('git', args, { cwd: projectPath, signal, timeout: 10_000, maxBuffer: 128 * 1024 });

View on GitHub (pinned to 5be4028344)

Solutions

Point input.path at a specific .json file, not a directory.
Remove any trailing slash from the path.
Verify the path is a file before scheduling a refresh.

Example fix

// before
const input = { path: 'src/' };
// throws `project_files.read_json path must be a file`

// after
const input = { path: 'src/data.json' };

Defensive patterns

Strategy: validation

Validate before calling

import { stat } from 'node:fs/promises';
async function assertIsFile(target: string): Promise<void> {
  const st = await stat(target);
  if (!st.isFile()) throw new Error('project_files.read_json path must be a file');
}

Prevention

Point read_json at a specific file, never a directory.
Strip trailing slashes from input.path.
Validate the path resolves to a regular file before scheduling refresh.

When it happens

Trigger: input.path resolves to a directory, a FIFO/socket, or a device special file inside the project.

Common situations: Pointing read_json at a directory path (e.g. 'src' instead of 'src/data.json'); a path with a trailing slash; an empty extension that resolved to a folder.

Related errors

AI-assisted analysis of nexu-io/open-design@5be4028344 (2026-08-12). Data as JSON: /api/errors/b95efb46c2d8d278. Report an issue: GitHub.