Theming

AG Grid v33+ styles grids through the Theming API: a JS theme object passed as the :theme grid option. The wrapper ships no theming code in v1 — no builder, no params helper (ADR 0013). It does not need any: a theme object is an opaque JS value, so :theme rides the conversion boundary untouched (non-CLJS values pass through verbatim, ADR 0005). :theme is a known option key, so it still gets dev-mode validation for free. This page is the whole recipe.

Default theme

Omit :theme entirely and you get AG Grid's default (Quartz). Nothing to configure:

(-> (ag/options)
    (ag/with-columns [...])
    (ag/with-row-data rows))

Customizing with .withParams

Import a base theme from AG Grid and build a variant with .withParams — this is raw interop past the conversion boundary, so the param object is a #js map with camelCase keys (the kebab→camel law does not apply here — you are already in JS):

(ns my.app
  (:require [ag-grid-cljs.core :as ag]
            ["ag-grid-community" :refer [themeQuartz]]))

(def my-theme
  (.withParams themeQuartz #js {:accentColor "red"
                                :fontFamily  "Inter, sans-serif"}))

(-> (ag/options)
    (assoc :theme my-theme)          ; opaque JS value, passes through verbatim
    (ag/with-columns [...]))

Dark mode

Two routes, both plain interop. Set dark parameters via .withParams on a base theme, or compose AG Grid's colorSchemeDark part with .withPart:

(ns my.app
  (:require ["ag-grid-community" :refer [themeQuartz colorSchemeDark]]))

;; compose the dark color-scheme part
(def dark-theme (.withPart themeQuartz colorSchemeDark))

;; or set dark params directly
(def dark-theme
  (.withParams themeQuartz #js {:backgroundColor "#1a1a1a"
                                :foregroundColor "#e0e0e0"}))

Assign whichever you build to :theme exactly as above. Switching themes at runtime is an ordinary options update — pass the new theme object through [[ag-grid-cljs.core/update-grid!]].

The theme: "legacy" escape hatch

To fall back to the pre-v33 CSS-files approach, set :theme to the string "legacy" and import the stylesheets through your own bundler:

(-> (ag/options)
    (assoc :theme "legacy"))         ; keyword would camelize; a string is verbatim

;; then, via your bundler:
;;   (:require ["ag-grid-community/styles/ag-grid.css"]
;;             ["ag-grid-community/styles/ag-theme-quartz.css"])

Note the value is the string "legacy", not the keyword :legacy: a keyword would camelize by the conversion law, and "legacy" is a literal AG Grid needs verbatim — this is the same keyword-vs-string distinction as everywhere else. The Theming API is AG Grid's default from v33+ and the story we recommend; legacy CSS is only the escape hatch.