Capture keyed prompts and source-backed content at load time

internal/prompt/go_renderer.go

@@ -76,7 +76,7 @@ func (r *goRenderer) Render(ctx context.Context, definition *domain.PromptDefini
 		if err := ctx.Err(); err != nil {
 			return nil, err
 		}
-		tmpl, parseErr := template.New(fmt.Sprintf("msg_%d", i)).Funcs(funcs).Option("missingkey=error").Parse(tmplMsg.Content)
+		tmpl, parseErr := parseTemplate(fmt.Sprintf("msg_%d", i), tmplMsg.Content, funcs)
 		if err := ctx.Err(); err != nil {
 			return nil, err
 		}
@@ -167,7 +167,7 @@ func renderSessionID(ctx context.Context, raw string, funcs template.FuncMap, va
 	if err := ctx.Err(); err != nil {
 		return "", err
 	}
-	tmpl, parseErr := template.New("session_id").Funcs(funcs).Option("missingkey=error").Parse(raw)
+	tmpl, parseErr := parseTemplate("session_id", raw, funcs)
 	if err := ctx.Err(); err != nil {
 		return "", err
 	}

internal/prompt/template.go

@@ -0,0 +1,15 @@
+package prompt
+
+import "text/template"
+
+// CompileTemplate checks static syntax with the same grammar and function
+// names as rendering, without evaluating request inputs or variables.
+func CompileTemplate(name, raw string) (*template.Template, error) {
+	return parseTemplate(name, raw, template.FuncMap{
+		"input": func(string) (string, error) { return "", nil },
+	})
+}
+
+func parseTemplate(name, raw string, funcs template.FuncMap) (*template.Template, error) {
+	return template.New(name).Funcs(funcs).Option("missingkey=error").Parse(raw)
+}