mastra-ai/mastra · error · Error

Config file not found at ${configPath}

Error message

Config file not found at ${configPath}

What it means

After tokenizer.json is found, loadTokenizerFromDir reads config.json to obtain model metadata (e.g. model type/dimensions). If <modelDir>/config.json does not exist on disk, the loader throws with the resolved path. The model directory is incomplete even though tokenizer.json was present.

Source

Thrown at packages/fastembed/src/fastembed.ts:156

    typeof token === 'object' &&
    token !== null &&
    'content' in token &&
    'single_word' in token &&
    'rstrip' in token &&
    'lstrip' in token &&
    'normalized' in token
  );
}

function loadTokenizerFromDir(modelDir: PathLike, maxLength: number): Tokenizer {
  const tokenizerPath = path.join(modelDir.toString(), 'tokenizer.json');
  if (!fs.existsSync(tokenizerPath)) {
    throw new Error(`Tokenizer file not found at ${tokenizerPath}`);
  }

  const configPath = path.join(modelDir.toString(), 'config.json');
  if (!fs.existsSync(configPath)) {
    throw new Error(`Config file not found at ${configPath}`);
  }
  const config = JSON.parse(fs.readFileSync(configPath, 'utf-8'));

  const tokenizerFilePath = path.join(modelDir.toString(), 'tokenizer_config.json');
  if (!fs.existsSync(tokenizerFilePath)) {
    throw new Error(`Tokenizer config file not found at ${tokenizerFilePath}`);
  }
  const tokenizerConfig = JSON.parse(fs.readFileSync(tokenizerFilePath, 'utf-8'));
  maxLength = Math.min(maxLength, tokenizerConfig['model_max_length']);

  const tokensMapPath = path.join(modelDir.toString(), 'special_tokens_map.json');
  if (!fs.existsSync(tokensMapPath)) {
    throw new Error(`Tokens map file not found at ${tokensMapPath}`);
  }
  const tokensMap = JSON.parse(fs.readFileSync(tokensMapPath, 'utf-8'));

  const tokenizer = Tokenizer.fromFile(tokenizerPath);

View on GitHub (pinned to 75dd419e61)

Solutions

1. Copy config.json from the source Hugging Face model repo into the model directory.
2. If the download was interrupted, clear the model cache and re-initialize to re-download everything.
3. For CUSTOM models, verify the full file set exists (config.json, tokenizer.json, tokenizer_config.json, special_tokens_map.json, model .onnx) before calling init.

Example fix

// before
$ cp my-model/model.onnx ./deploy-model/  # only weights copied
// after
$ cp my-model/{model.onnx,config.json,tokenizer.json,tokenizer_config.json,special_tokens_map.json} ./deploy-model/

import fs from 'node:fs';
if (!fs.existsSync(path.join(dir, 'config.json'))) {
  throw new Error(`${dir} missing config.json; copy it from the model repo root`);
}

try {
  const embedder = await FlagEmbedding.init(opts);
} catch (err) {
  if (err instanceof Error && err.message.includes('Config file not found')) {
    // restore config.json into the model dir, then retry once
  } else throw err;
}

When it happens

Trigger: FlagEmbedding.init with a modelDir that has tokenizer.json but no config.json — typically a hand-assembled custom model directory, a custom HF checkpoint exported without config, or a manually pruned cache.

Common situations: Copying only tokenizer + ONNX weights when preparing a CUSTOM model; a download that fetched tokenizer.json but failed before config.json; minifying a model directory and deleting files deemed unused.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

• Tokenizer file not found at ${tokenizerPath}
• Model file not found at ${modelPath}
• Tokenizer config file not found at ${tokenizerFilePath}
• Tokens map file not found at ${tokensMapPath}
• Snapshot file not found: ${snapshotPath} Run with { updateSn

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/016df0133d613014. Report an issue: GitHub.