rohitg00/ai-engineering-from-scratch · error · ValueError

state secret must not be empty

Error message

state secret must not be empty

What it means

Error "state secret must not be empty" thrown in rohitg00/ai-engineering-from-scratch.

Source

Thrown at certifications/claude/lessons/11-mcp-server-design-and-integration/code/main.py:75

            "string": lambda value: isinstance(value, str),
        }
        for name, value in arguments.items():
            if name not in properties:
                continue
            expected = properties[name].get("type")
            if expected not in checks:
                raise ValueError(f"unsupported schema type for {name}: {expected!r}")
            if not checks[expected](value):
                raise ValueError(f"{name} must be {expected}")
        return arguments


class RequestStateSigner:
    """Produces an opaque, integrity-protected MRTR requestState value."""

    def __init__(self, secret: bytes) -> None:
        if not secret:
            raise ValueError("state secret must not be empty")
        self.secret = secret

    def issue(self, method: str, tool: str, arguments: dict[str, Any]) -> str:
        payload = json.dumps(
            {"method": method, "tool": tool, "arguments": arguments},
            sort_keys=True,
            separators=(",", ":"),
        ).encode("utf-8")
        encoded = base64.urlsafe_b64encode(payload).decode("ascii").rstrip("=")
        signature = hmac.new(self.secret, encoded.encode("ascii"), hashlib.sha256).hexdigest()
        return f"{encoded}.{signature}"

    def verify(self, token: str, method: str, tool: str, arguments: dict[str, Any]) -> None:
        if not isinstance(token, str) or "." not in token:
            raise ValueError("requestState is malformed")
        encoded, supplied_signature = token.rsplit(".", 1)
        expected_signature = hmac.new(
            self.secret, encoded.encode("ascii"), hashlib.sha256

View on GitHub (pinned to 39ea8a1c6d)

When it happens

Trigger: Thrown at certifications/claude/lessons/11-mcp-server-design-and-integration/code/main.py:75 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of rohitg00/ai-engineering-from-scratch@39ea8a1c6d (2026-08-26). Data as JSON: /api/errors/b619237b31f260cc. Report an issue: GitHub.