BoundaryML/baml · error · anyhow::Error

Failed to get template '{}': {}

Error message

Failed to get template '{}': {}

What it means

BAML renders Jinja-templated prompt parts with minijinja. After adding the template to the render environment, it fetches it back by name; if the get fails, BAML wraps the minijinja error in this message. This indicates the template engine refused to return a template that was just registered, typically due to template-name or environment issues.

Source

Thrown at engine/baml-lib/baml-core/src/ir/ir_helpers/mod.rs:2086

                    "{{% macro {name}({args}) %}}{template}{{% endmacro %}}",
                    name = t.name(),
                    args = args_str,
                    template = t.template(),
                )
            })
            .chain(std::iter::once(template_content.to_string()))
            .collect::<Vec<_>>()
            .join("\n");

        // Use the shared environment (trim_blocks, lstrip_blocks, debug,
        // null formatter, regex_match/sum filters) to match the prompt renderer.
        let mut env = get_env();
        env.add_template("__template__", &full_template)
            .map_err(|e| anyhow::anyhow!("Failed to parse template '{}': {}", name, e))?;

        let tmpl = env
            .get_template("__template__")
            .map_err(|e| anyhow::anyhow!("Failed to get template '{}': {}", name, e))?;

        let context = minijinja::Value::from_serialize(&args_map);
        let rendered = tmpl
            .render(context)
            .map_err(|e| anyhow::anyhow!("Failed to render template '{}': {}", name, e))?;

        Ok(rendered)
    }
}

#[cfg(test)]
mod render_template_tests {
    use baml_types::TemplateStringRenderer;
    use repr::make_test_ir;

    use super::*;

    #[test]

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Check your BAML version and upgrade to the latest — this is often fixed in newer minijinja/baml-core releases.
2. Inspect the inner minijinja error (printed after ': {}' in the message) for the real cause.
3. Simplify the prompt template (remove exotic Jinja syntax, ensure valid UTF-8) and retry.
4. If reproducible, file an issue with the BAML team — this path is normally unreachable for valid templates.

match render_template(&name, &args) {
    Ok(rendered) => rendered,
    Err(e) if e.to_string().contains("Failed to get template") => {
        // log inner minijinja cause, retry with upgraded baml, or fail fast
        eprintln!("template env error: {e:#}");
        return Err(e);
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: Calling BAML's template rendering helper (render_template in ir_helpers) when minijinja's env.get_template("__template__") fails after env.add_template succeeded — e.g. internal environment state inconsistency or engine-level rejection of the template.

Common situations: BAML internal/template engine version mismatch; corrupted or non-UTF8 prompt template content; concurrency issues with the shared Jinja environment. Rarely caused directly by user code since the template name is the fixed internal name "__template__".

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Expected a statically defined string, not expression
• Failed to parse template '{}': {}
• Failed to render template '{}': {}
• Expected a statically defined string, not a template_string
• UnknownMethod

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/3aa4b2835bbdef72. Report an issue: GitHub.