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A template is a string with {{...}} tags that graph fills from data before a step, tool or agent runs. Templates only move data. They never call a model, and they have no logic beyond iterating over lists.

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Where templates are used

Inside a map or reduce body, item and index reference the current element, and reduce adds accumulator. A filter gate gets item and index too.

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Variables

A variable is a dotted path from a root. Number segments index into arrays, and length as the last segment counts the items in an array or the characters in a string.
Spaces inside the braces are ignored. A step id can’t be input, item, index, accumulator or length. A route step’s result is read through the route’s own id: {{triage.branch}} names the branch that ran and {{triage.result}} holds what it returned. Steps inside a branch are visible only to later steps in the same branch.

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Typed values

When a string is exactly one tag, the tag’s value keeps its JSON type. When a tag sits in other text, the result is a string, and objects and arrays are written as JSON.
With max set to 50 and ids to [1, 2, 3], limit is the number 50, ids is the array [1, 2, 3], and query is the string "team Core". A null value written into text renders as nothing.

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Sections

A section renders its body once for each item in a list, once for an object or any other value, and not at all for a missing, null, false or empty value.
  • Inside a section, a tag without a root, such as {{title}}, reads from the current item, then from enclosing sections. If no item has the key, it renders as nothing.
  • {{@index}} is the item’s position, starting at 0. {{@first}} and {{@last}} are booleans you can use as sections.
  • An inverted section, {{^path}}...{{/path}}, renders only when the section would not:
  • A section path that doesn’t resolve counts as empty rather than an error, so {{^fetch.optional}} works as a fallback. A section over a step that doesn’t exist is still an error.

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Errors

A variable that doesn’t resolve stops the step with one of three errors: graph plan validate catches references to steps that don’t exist or haven’t run yet before the plan runs. To learn how a plan responds to each error, see Handle failures.

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Not supported

Templates have no conditionals, functions, partials, comments or inheritance, and using that syntax is a parse error. Put any computation in a step, such as a reshape tool or an infer gate.