Function substituteVariables

src/services/SessionMemory/prompts.ts:201–213

* Substitute variables in the prompt template using {{variable}} syntax

(
  template: string,
  variables: Record<string, string>,
)

 * Substitute variables in the prompt template using {{variable}} syntax
 */
function substituteVariables(
  template: string,
  variables: Record<string, string>,
): string {
  // Single-pass replacement avoids two bugs: (1) $ backreference corruption
  // (replacer fn treats $ literally), and (2) double-substitution when user
  // content happens to contain {{varName}} matching a later variable.
  return template.replace(/\{\{(\w+)\}\}/g, (match, key: string) =>
    Object.prototype.hasOwnProperty.call(variables, key)
      ? variables[key]!
      : match,
  )
}

/**
 * Check if the session memory content is essentially empty (matches the template).