What causes "Error rendering template '{template_name}': {e!s}" in microsoft/graphrag?

Inspect the chained original exception (e.__cause__) and message for the underlying Jinja error

microsoft/graphrag · error · RuntimeError

Error rendering template '{template_name}': {e!s}

Error message

Error rendering template '{template_name}': {e!s}

What it means

JinjaTemplateEngine.render wraps any non-UndefinedError exception from jinja_template.render() in a RuntimeError with the template name and the original message. This catches genuine Jinja failures such as syntax errors in the template, bad filters, or invalid operations on context values, chaining the original exception as __cause__.

Source

Thrown at packages/graphrag-llm/graphrag_llm/templating/jinja_template_engine.py:50

    def render(self, template_name: str, context: dict[str, Any]) -> str:
        """Render a template with the given context."""
        jinja_template = self._templates.get(template_name)
        if jinja_template is None:
            template_contents = self._template_manager.get(template_name)
            if template_contents is None:
                msg = f"Template '{template_name}' not found."
                raise KeyError(msg)
            jinja_template = Template(template_contents, undefined=StrictUndefined)
            self._templates[template_name] = jinja_template
        try:
            return jinja_template.render(**context)
        except UndefinedError as e:
            msg = f"Missing key in context for template '{template_name}': {e.message}"
            raise KeyError(msg) from e
        except Exception as e:
            msg = f"Error rendering template '{template_name}': {e!s}"
            raise RuntimeError(msg) from e

    @property
    def template_manager(self) -> "TemplateManager":
        """Template manager associated with this engine."""
        return self._template_manager

View on GitHub (pinned to f40e9a26ce)

Solutions

Inspect the chained original exception (e.__cause__) and message for the underlying Jinja error
Fix the template syntax/filter or load the required Jinja extension
Validate the types of context values passed to render
Preview/test templates with jinja2.Template(...).render in isolation to confirm they compile

Example fix

# before
{{ name | nosuchfilter }}

# after
{{ name | upper }}

Defensive patterns

Strategy: try-catch

Validate before calling

from jinja2 import Environment, TemplateSyntaxError

src = engine.template_manager.get(name)
if src is not None:
    try:
        Environment().parse(src)
    except TemplateSyntaxError as e:
        raise ValueError(f"Template {name} has syntax error: {e}") from e

Type guard

from jinja2 import Environment, TemplateSyntaxError

def template_compiles(src: str) -> bool:
    try:
        Environment().parse(src)
        return True
    except TemplateSyntaxError:
        return False

Try / catch

try:
    out = engine.render(name, ctx)
except RuntimeError as e:
    log.error("Template render failed: %s", e)
    if e.__cause__ is not None:
        log.error("Underlying Jinja error: %r", e.__cause__)
    raise

Prevention

Parse/compile templates once at startup to catch syntax errors early
Type-check context values before render
Load required Jinja extensions when constructing engines

When it happens

Trigger: Calling render() with a template containing Jinja syntax errors, applying an undefined/nonexistent filter, or performing invalid operations (e.g. arithmetic on None) on context values.

Common situations: Hand-edited templates with syntax mistakes, filters requiring extra extensions not loaded, or context values with unexpected types.

Related errors

AI-assisted analysis of microsoft/graphrag@f40e9a26ce (2026-08-27). Data as JSON: /api/errors/c98d2658906fd162. Report an issue: GitHub.