sigoden/aichat · error

No return value from '_instructions' function

Error message

No return value from '_instructions' function

What it means

Guard in the dynamic-instructions path: the agent's '_instructions' LLM function was invoked to generate instructions at runtime, but it returned no value (None), so there is nothing to store as the dynamic instruction text. The fault is in the agent's function definition — it fails to return any output for the empty '{}' arguments it is called with.

Solutions

1. Fix the '_instructions' function in the agent's functions directory so it always returns a string
2. Test the function directly with '{}' arguments to reproduce the empty return
3. Add a default/fallback instruction text to use when the function yields nothing, so agent init does not hard-fail

When it happens

Trigger: Thrown at src/config/agent.rs:322 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of sigoden/aichat@82976d349a (2026-09-09). Data as JSON: /api/errors/351c755a0dff3216. Report an issue: GitHub.

Appendix: source

Thrown at src/config/agent.rs:322

        if self.is_dynamic_instructions() {
            let value = match value {
                Some(v) => v,
                None => self.run_instructions_fn()?,
            };
            self.session_dynamic_instructions = Some(value);
        }
        Ok(())
    }

    fn run_instructions_fn(&self) -> Result<String> {
        let value = run_llm_function(
            self.name().to_string(),
            vec!["_instructions".into(), "{}".into()],
            self.variable_envs(),
        )?;
        match value {
            Some(v) => Ok(v),
            _ => bail!("No return value from '_instructions' function"),
        }
    }
}

impl RoleLike for Agent {
    fn to_role(&self) -> Role {
        let prompt = self.interpolated_instructions();
        let mut role = Role::new("", &prompt);
        role.sync(self);
        role
    }

    fn model(&self) -> &Model {
        &self.model
    }

    fn temperature(&self) -> Option<f64> {
        self.config.temperature

View on GitHub (pinned to 82976d349a)