microsoft/autogen · error · ValueError

Invalid name: {name}. Name must be less than 64 characters.

Error message

Invalid name: {name}. Name must be less than 64 characters.

What it means

Thrown by assert_valid_name in autogen_ext.models.openai._utils when a configured name is longer than 64 characters. Even if the character set is valid, the length cap (mirroring API-side identifier limits) is enforced client-side before the name reaches the provider.

Source

Thrown at python/packages/autogen-ext/src/autogen_ext/models/openai/_utils.py:13

import re


def assert_valid_name(name: str) -> str:
    """
    Ensure that configured names are valid, raises ValueError if not.

    For munging LLM responses use _normalize_name to ensure LLM specified names don't break the API.
    """
    if not re.match(r"^[a-zA-Z0-9_-]+$", name):
        raise ValueError(f"Invalid name: {name}. Only letters, numbers, '_' and '-' are allowed.")
    if len(name) > 64:
        raise ValueError(f"Invalid name: {name}. Name must be less than 64 characters.")
    return name

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Shorten the name to <= 64 characters (abbreviate or drop path segments)
2. Derive a stable short name, e.g. hashlib-based: name[:64] or a slug of the full name
3. Add a length check in name-generation code so long names fail loudly at build time

Example fix

# before
tool_name = f"{module_path}_{klass}_{method}"  # 80+ chars
assert_valid_name(tool_name)  # ValueError

# after
tool_name = f"{module_path}_{klass}_{method}"[:64]
assert_valid_name(tool_name)

name = name[:64]  # enforce cap before use
assert is_valid_name(name)

def is_valid_name(name: str) -> bool:
    import re
    return bool(re.fullmatch(r"[a-zA-Z0-9_-]{1,64}", name))

try:
    assert_valid_name(name)
except ValueError as e:
    if "64 characters" in str(e):
        name = name[:64]
        assert_valid_name(name)
    else:
        raise

When it happens

Trigger: Passing a name that passes the character regex but exceeds 64 chars — e.g. auto-generated tool names combining module paths, class names, and suffixes, or long descriptive agent identifiers.

Common situations: Programmatically composed names (f'{module}_{class}_{method}') growing past 64 chars; names embedding UUIDs or long slugs; copy-pasted fully-qualified identifiers.

Related errors

• Invalid name: {name}. Only letters, numbers, '_' and '-' are
• Unsupported config type {config.GetType()}
• Messages should not be provided in options
• Parameter name cannot be null
• Unknown message type: {m.GetType()}

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/fe04962b838f38d4. Report an issue: GitHub.