Handlebars helper execution remains synchronous, blocking async operations

Handlebars 4.x executes every helper synchronously and does not await promises returned by helper functions. The engine coerces the helper result directly to a string, so an unresolved promise appears as “[object Promise]” or an empty string in the rendered output.

The documentation explicitly states that helpers must return a string or a Handlebars.SafeString, and there is no runtime flag or configuration option to enable asynchronous helper resolution. This limitation has been tracked since 2013 (issue #831) and remains open in the current release line.

• Is there any built‑in API or configuration in Handlebars 4.x that allows helpers to resolve asynchronously without pre‑fetching data?
• Are there officially supported patterns for integrating async data sources directly inside templates?
• What is the current roadmap status for native async helper support in future Handlebars releases?