What causes "assistant id is required" in langchain-ai/deepagents?

Set DEEPAGENTS_TALON_ASSISTANT_ID= in the environment or .env file used by the process.

langchain-ai/deepagents · error · TalonConfigError

assistant id is required

Error message

assistant id is required

What it means

`TalonConfig.from_env` requires an assistant id and falls back to the value 'default' only when the env vars (`DEEPAGENTS_TALON_ASSISTANT_ID`, `AGENT_ASSISTANT_ID`) resolve to an empty string; if the resolved value is `None`, configuration is considered incomplete and `TalonConfigError` is raised. Every Talon runtime must be bound to an assistant id.

Source

Thrown at libs/talon/deepagents_talon/config.py:72

            base_home: Optional base directory for assistant state. Tests and
                embedding hosts can supply this to avoid the user home directory.

        Returns:
            Runtime configuration with a validated assistant id and namespaced home.

        Raises:
            TalonConfigError: If the assistant id is empty or unsafe for a path segment.
        """
        values = os.environ if env is None else env
        assistant_id = _first_present(
            values,
            "DEEPAGENTS_TALON_ASSISTANT_ID",
            "AGENT_ASSISTANT_ID",
            default="default",
        )
        if assistant_id is None:
            msg = "assistant id is required"
            raise TalonConfigError(msg)
        _validate_assistant_id(assistant_id)

        if base_home is None:
            configured_home = values.get("DEEPAGENTS_TALON_HOME")
            root = Path(configured_home) if configured_home else Path.home() / ".deepagents"
        else:
            root = base_home

        model = _first_present(values, "DEEPAGENTS_TALON_MODEL", "AGENT_MODEL", default=None)
        return cls(
            assistant_id=assistant_id,
            home=root.expanduser() / assistant_id,
            model=model,
            env={key: value for key, value in values.items() if _is_runtime_env(key)},
        )

    def ensure_home(self) -> Path:
        """Create the per-assistant home directory with restrictive permissions.

View on GitHub (pinned to a1af029e6e)

Solutions

Set DEEPAGENTS_TALON_ASSISTANT_ID=<your-assistant-id> in the environment or .env file used by the process.
Alternatively set AGENT_ASSISTANT_ID, the legacy fallback variable.
If you intend the default, verify why the fallback didn't apply — the lookup likely returned None rather than empty; export the var explicitly to be safe.

Example fix

# before
# (no assistant id in env)
# after
export DEEPAGENTS_TALON_ASSISTANT_ID=my-assistant

Defensive patterns

Strategy: validation

Validate before calling

import os
if not (os.environ.get("DEEPAGENTS_TALON_ASSISTANT_ID") or os.environ.get("AGENT_ASSISTANT_ID")):
    raise RuntimeError("Set DEEPAGENTS_TALON_ASSISTANT_ID before starting Talon")

Type guard

def assistant_id_configured(env: dict[str, str]) -> bool:
    return bool(env.get("DEEPAGENTS_TALON_ASSISTANT_ID") or env.get("AGENT_ASSISTANT_ID"))

Try / catch

try:
    config = TalonConfig.from_env(os.environ)
except TalonConfigError as exc:
    logging.error("invalid Talon configuration: %s", exc)
    raise SystemExit(1)

Prevention

Keep assistant id in your .env template and commit the template (not secrets)
Fail fast at process start with an env-var presence check
Document the variable names in your deployment runbook
When scripting, pass an explicit env dict including the assistant id

When it happens

Trigger: Calling `TalonConfig.from_env` (directly or via `main`, `_run_import_fleet_command`) when `DEEPAGENTS_TALON_ASSISTANT_ID` / `AGENT_ASSISTANT_ID` are unset such that the resolved assistant id is None rather than the 'default' fallback.

Common situations: New developer machines without the .env loaded; CI jobs missing secrets/env injection; helper scripts constructing env dicts that omit the assistant id keys; migrations from other agent tooling that used a different variable name.

Understand the failure class

Background: "environment variable is not set" and "Missing keys in environment" errors: what missing required env var messages mean and how to fix them — this error's family across 28 libraries.

Related errors

AI-assisted analysis of langchain-ai/deepagents@a1af029e6e (2026-08-29). Data as JSON: /api/errors/bcfc2453fb4746fb. Report an issue: GitHub.