sgl-project/sglang · error · ValueError

Every cache_salt should be a string.

Error message

Every cache_salt should be a string.

What it means

Raised when cache_salt is a list containing at least one non-string element. Each per-request salt must be a str (empty string normalizes to None, meaning no salting).

Source

Thrown at python/sglang/srt/managers/io_struct.py:812

            self.extra_key = [value or None for value in self.extra_key]
            self.extra_key = self.extra_key * self.parallel_sample_num
        else:
            raise ValueError("extra_key should be a list or a string.")

    def _normalize_cache_salt(self, num):
        """Normalize cache_salt for batch processing."""
        if self.cache_salt is None:
            return
        if isinstance(self.cache_salt, str):
            value = self.cache_salt or None
            self.cache_salt = [value] * num
        elif isinstance(self.cache_salt, list):
            if len(self.cache_salt) != self.batch_size:
                raise ValueError(
                    "The length of cache_salt should be equal to the batch size."
                )
            if any(not isinstance(value, str) for value in self.cache_salt):
                raise ValueError("Every cache_salt should be a string.")
            self.cache_salt = [value or None for value in self.cache_salt]
            self.cache_salt = self.cache_salt * self.parallel_sample_num
        else:
            raise ValueError("cache_salt should be a list or a string.")

    def _normalize_bootstrap_params(self, num):
        """Normalize bootstrap parameters for batch processing."""
        # Normalize bootstrap_host
        if self.bootstrap_host is None:
            self.bootstrap_host = [None] * num
        elif not isinstance(self.bootstrap_host, list):
            self.bootstrap_host = [self.bootstrap_host] * num
        elif isinstance(self.bootstrap_host, list):
            self.bootstrap_host = self.bootstrap_host * self.parallel_sample_num

        # Normalize bootstrap_port
        if self.bootstrap_port is None:
            self.bootstrap_port = [None] * num

View on GitHub (pinned to 0132848349)

Solutions

1. Convert elements to str: [str(s) for s in salts]
2. Use '' for requests needing no salt
3. Use a single str for uniform salting

Example fix

// before
cache_salt=[b'hash1', b'hash2']
// after
cache_salt=['hash1', 'hash2']

assert all(isinstance(s, str) for s in cache_salt), 'salts must be str'

When it happens

Trigger: cache_salt=[None, 's'] or [1, 2] with batch_size=2.

Common situations: Using bytes from hashes, ints, or None placeholders in the salt list.

Related errors

• extra_key should be a list or a string.
• The length of cache_salt should be equal to the batch size.
• cache_salt should be a list or a string.
• Unsupported image type: {type(image)}
• MiniMax H3 model variant must be a non-empty string

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/5e89d0217e640c72. Report an issue: GitHub.